SRS Labs QMS 100 Series User Manual

Gas analyzer

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User's Manual

QMS 100 Series

Gas Analyzer

1290-D Reamwood Avenue

Sunnyvale, CA 94089 U.S.A.

Phone: (408) 744-9040, Fax: (408) 744-9049

Email: info@thinkSRS.com ▪ www.thinkSRS.com

Version 3.2 (1/2012)

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Page 1 User’s Manual QMS 100 Series Gas Analyzer 1290-D Reamwood Avenue Sunnyvale, CA 94089 U.S.A. Phone: (408) 744-9040, Fax: (408) 744-9049 Email: info@thinkSRS.com ▪ www.thinkSRS.com Copyright © 2012 All Rights Reserved Version 3.2 (1/2012)
Page 2 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment. Warranty This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment. Service For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service facility.
Page 3: Table Of Contents
Table of Contents Safety ................................... iv Symbols ..................................v Fast Start ..................................vi Specifications................................vii Materials List ................................ix Calibration Log ................................x Chapter 1. Introduction & Operation.........................1–1 Introduction ..............................1–2 What’s Inside ?...............................1–4 Operation................................1–7 Mass Spectrometry Basics..........................1–16 Chapter 2. Windows Software ........................... 2-1 Overview ................................
Page 4: Safety
Safety WARNING Hazardous voltages, capable of causing injury or death, are present in this instrument. Use extreme caution whenever the instrument cover is removed. Always unplug the unit while removing the cover. Ventilation The QMS system requires forced air cooling to operate at a reasonable temperature.
Page 5 SRS QMS Gas Analyzer...
Page 6: Fast Start
Fast Start • Connect the power cord to the . Set the four switches on the control panel to off and turn on the main power switch. • Turn on the diaphragm pump switch and the turbo pump switch. The pumps should begin the startup sequence, which takes several minutes.
Page 7: Specifications
Specifications Inlet Type capillary: available in stainless steel, PEEK, and glass lined plastic Flowrate 1 to 10 milliliter per minute at atmospheric pressure Response time <400 ms Pressure selectable from 10 mbar to 1 bar Mass Spectrometer Type quadrupole Detector Faraday cup standard electron multiplier optional Range...
Page 8 viii protection class IP44 Materials construction: SS304 and SS316 (see full materials list for details) insulators: alumina, ceramic seals: Viton, buna-N, and nitrile butyl rubber misc: aluminum, Tygon General Startup time 2 minutes from full stop 35 °C Max. Ambient Operating Temperature Power requirement either 110 V / 60 Hz or 220 V / 50 Hz (not field...
Page 9: Materials List
Materials List SRS receives many requests for information about corrosion compatibility. It is our policy not to state the compatibility of our system with various corrosive environments. We simply cannot test the myriad combinations of environments that our customers use. We do provide a list of all the materials exposed to the gas being introduced into the system.
Page 10: Calibration Log
Calibration Log SRS serial number ___________ In the table below are the results of the factory calibration of the inlet and capillary. The factor is entered in the pressure reduction factor dialog box (under the Utilities menu) in the RGA software.
Page 11 Chapter 1. Introduction & Operation In This Chapter Introduction ..................................1–2 External Connections ..............................1–3 Operating Orientation ...............................1–4 What’s Inside ? ................................1–4 Gas Handling Subsystem............................1–4 Mass Spectrometer..............................1–6 Operation...................................1–7 Front Panel Operation...............................1–8 Continuous Sample Mode............................1–10 Startup Just the Pumps.............................1–10 Startup the Sample Flow...........................1–10 Idle ..................................1–11 Shutdown ................................1–11 Batch Analyze Mode ..............................1–12...
Page 12: Introduction
1–2 Introduction Introduction The QMS 100 series instruments are modern mass spectrometers designed for the analysis of light gases. The three systems, 100, 200 and 300, differ only in the mass range they can detect. A quadrupole mass spectrometer performs the task of analyzing the gas.
Page 13: External Connections
Introduction 1–3 needs of most users. For users with specialized needs, the QMS can be controlled from user programs. The Technical Reference Manual discusses details of the QMS, its programming, and service. External Connections The instrument has two gas connections: an inlet on the front panel and an exhaust on the back panel.
Page 14: What's Inside
1–4 What’s Inside ? The system exhausts to the rear panel. All of the gas drawn into the inlet is exhausted through this port. The port is a 1/4 inch Swagelok tube stub, which can be connected to a wide variety of tube fittings. When sampling hazardous gases, the user must ensure that the exhaust gas is properly handled.
Page 15 What’s Inside ? 1–5 a length of 0.9 m. Most of the capillary flow does not travel to the RGA, but is bypassed directly to the diaphragm pump. A small part of this flow is drawn through a small aperture (60 µm diameter) into the chamber where the RGA is located.
Page 16: Mass Spectrometer
1–6 What’s Inside ? Mass Spectrometer A residual gas analyzer (RGA) is mass spectrometer of small physical dimensions whose function is to analyze the gases inside the vacuum chamber. The principle of operation is the same for all instruments: A small fraction of the gas molecules are ionized to create positive ions, and the resulting ions are separated, detected and measured according to their molecular masses.
Page 17: Operation
Operation 1–7 • Histogram scanning • Single mass measurement RGA Windows provides fast access to all the RGA functions without the need for any computer programming; however, the instrument can also be programmed directly using the RGA Command Set supported by its serial interface. Consult the RGA Programming chapter of the Technical Reference for information on programming and a complete listing of the RGA Command Set.
Page 18: Front Panel Operation
1–8 Operation Front Panel Operation The two pumps and two valves are operated with the four switches on the small panel (see Figure 5). The Pressure bar display is the pressure at the inlet port on the instrument front panel. The Current bar display is an indication of the current drawn by the turbo pump and is useful as a system diagnostic.
Page 19 Operation 1–9 Controller State Diagram V e n t R ou gh P um p Tur bo Pum p Te s t B yp as s B yp a ss F low E r r or co n dition s wh ich cau s e a ret reat to previ ou s s tate: T u r bo pum p is no t at s pe ed B at ch An a lyze...
Page 20: Continuous Sample Mode
1–10 Operation The microcontroller is inactive for about 5 seconds after main power is turned on. The user cannot turn on any of the system components during this period. If the user does turn on one of the front panel switches during this period, it will be rejected and the adjacent light will blink.
Page 21: Idle
Operation 1–11 established, the sample valve will open, and measurements can be made. When the capillary flow valve is first opened, a pressure pulse will occur in the system that will invariable shutoff the RGA filament. If you where previously making measurements at state 2B, the RGA filament should be turned off while starting the sample flow.
Page 22: Batch Analyze Mode
1–12 Operation If the diaphragm pump is inadvertently stored under vacuum for extended periods, the internal pressures will reach a state that prevents the pump from starting. If this has happened the user will hear a relay click but the diaphragm pump will not start. This locked state is cured by venting the system; the diaphragm pump will then start up.
Page 23: Microcontroller Error Checks
Operation 1–13 Microcontroller Error Checks The microcontroller is programmed to prevent the system from restarting after a power failure. If the Mechanical Pump switch is turned on before line power is applied, the controller will halt and prevent further action from taking place. It will stay halted until the Mechanical Pump switch is turned off, which resets the system.
Page 24: Operating Modes Of The Spectrometer
1–14 Operation Operating Modes of the Spectrometer The RGA is a mass spectrometer that analyzes residual gases by ionizing some of the gas molecules (positive ions), separating the resulting ions according to their respective masses and measuring the ion currents at each mass. Partial pressure measurements are determined with the help of previously calculated sensitivity (i.e.
Page 25: The Rga As A Single Gas Monitor
Operation 1–15 RGA Windows uses the two modes to generate the data for the Analog and Histogram Scan Modes. Analog scanning is the most basic operation of the RGA as a quadrupole mass spectrometer. During analog scanning the quadrupole mass spectrometer is stepped at fixed mass increments through a pre- specified mass-range.
Page 26: Mass Spectrometry Basics
1–16 Mass Spectrometry Basics Mass Spectrometry Basics The RGA can perform both qualitative and quantitative analysis of the gases in a vacuum system. Obtaining spectra with the RGA is very simple. Interpreting the spectra, that is, understanding what the spectra is trying to tell you about your vacuum system requires some work. The following sections will introduce some basic concepts of Spectral Analysis emphasizing the main aspects of Residual Gas Analysis.
Page 27: Partial Pressure Measurement
Mass Spectrometry Basics 1–17 Notes on Fragmentation Patterns : The electron impact type of ionizer used in modern RGA’s almost always causes more than one kind of ion to be produced from a single type of gas molecule. Multiple ionization, molecular fragmentation and changes in the isotopic composition of the molecule are responsible for the effect.
Page 28: Partial Pressure Sensitivity Factors
1–18 Mass Spectrometry Basics = RGA’s partial pressure sensitivity factor for gas g, in amp/Torr (see Partial Pressure Sensitivity Factor below) = Partial pressure of gas g in the system. Equations (1) and (2) are combined to obtain the system of equations: = Σ...
Page 29 Mass Spectrometry Basics 1–19 The sensitivity of the RGA varies with different gases, changes with time due to aging of the head, and is a strong function of the operating conditions of the instrument. Careful quantitative analysis requires that the sensitivity factor, , be determined for every gas which may be a component gas in the system being analyzed.
Page 30 1–20 Mass Spectrometry Basics built into the program, can adjust the CDEM voltage for any gain between 10 and 10 . Consult the RGA On-Line Help Files for details on the automated tuning procedures built into the RGA Windows program. Also see the Sensitivity and Electron Multiplier Tuning sections of the RGA Tuning Chapter for more general information.
Page 31: Chapter 2. Windows Software
Chapter 2. Windows Software The QMS system contains a mass spectrometer that belongs to a class of spectrometers commonly referred to as residual gas analyzers or RGA. RGAs are low resolution, low mass range, quadrupole spectrometers. The SRS spectrometer is used both as a stand-alone RGA and in the PPR and QMS systems.
Page 32 2-2 Overview Running in Split Display Mode.......................2-16 Manual Scaling of Graphs........................2-16 Using Scan Data as Background ......................2-16 General Utilities............................2-17 Using the Data Cursors ...........................2-17 Scheduled Saving of Data ........................2-18 Logging Scans ...........................2-18 Viewing Scans...........................2-18 Browsing Through the Gas Library ......................2-19 Analyzing the Mass Spectrum ........................2-19 Spectrum Analysis description ......................2-19 Analysis Procedure..........................2-20...
Page 33: Overview
Overview 2-3 Overview Program Structure The RGA program is a fully interactive Windows program capable of managing several RGA Heads simultaneously. Fully interactive means that you can double-click on any graph object and the program responds by executing a specific command such as editing the color of a data line. RGA was designed to handle data acquisition from multiple heads simultaneously by assigning one head for each window and by making all the windows independent from each other.
Page 34: System Requirements
2-4 System Requirements RGA ASCII Data files (.txt) The RGA program can save the last scan data in an ASCII format that is easily read by spreadsheet programs for data analysis. The file header contains the scan setup information followed by the scan data. The RGA program does not read these ASCII file, it only writes them. RGA Graph Metafiles (.wmf) RGA can also save the active graph as a Windows Metafile.
Page 35: Starting The Rga Software
Getting Started 2-5 Starting the RGA Software To start the RGA software simply double-click on the RGA icon in the "SRS RGA" program group created by the RGA installation program. You may also type the full path name of the RGA program in the Run command from the Program manager.
Page 36: Features And Operation
2-6 Features and Operation The recommended shut-down procedure is: 1. Stop the scan if there is one in progress using the Stop Now command in the Scan menu. 2. Turn off the filament and CEM. 3. Save the RGA file you have been working on, using the Save or Save As command in the File menu.
Page 37: Analog (Mode Menu)
Features and Operation 2-7 Analog (Mode Menu) Analog mode is the spectrum analysis mode common to all Residual Gas Analyzers. The X- Axis represents the mass range chosen in the Mass Spec Parameters menu. The Y-Axis represents the ion current amplitudes of every mass increment measured. Select the Schedule menu to set the scan trigger timing.
Page 38: P Vs. T (Mode Menu)
2-8 Features and Operation Spec Scan Parameters menu button on the toolbar Table entries can be configured independently from each other. Some entries can use the Channel Electron Multiplier (CEM), while others can have different scan speeds with the CEM off.
Page 39: Leak Test (Mode Menu)
Features and Operation 2-9 parameters, alarm parameters, and graph trace colors. The data acquisition method for the P vs. T scan will vary depending on the display mode selected: In P vs. T mode or Table mode split with P vs. T mode, each table entry value (partial pressure) is acquired directly from the RGA head by individually querying the partial pressure for the appropriate mass.
Page 40: Library (Mode Menu)
2-10 Features and Operation The Annunciator channels can be independently configured. Some channels can use the Channel Electron Multiplier (CEM) while others can have different scan speed with the CEM off. The alarm control and level settings can be edited by either double clicking on the Alarm text of the desired Annunciator entry, or by clicking on the 'Alarm X' (where X is the channel number) button for the Annunciator channel in the Table Parameters dialog box.
Page 41: Scan Data Logging
Features and Operation 2-11 2. Establish a connection between the RGA program and the Head (Connector List Setup in the Head menu, or Connector List button on the toolbar). 3. Select the desired display mode (Mode Menu). 4. Turn On the Filament (Head menu or Filament button). 5.
Page 42: Head Management
2-12 Features and Operation example, if the background mode in Analog mode is changed to yellow, the background mode of all the other modes remains unchanged. Also, any new file using the Analog mode still uses the default background color. After an RGA file has been edited to have a desired look, it may be used as a template for new files by clearing its data using the Clear Graph Data command, saving it using the Save As command, and opening it again using the Open command.
Page 43: Rga Head And Scan Parameters
RGA Head and Scan Parameters 2-13 Background Data This mode is helpful in providing the user with a clean baseline after the background data gets subtracted from newly acquired scans. This utility is available in Analog mode, Histogram mode, Table mode, and P vs. T mode. In Analog mode and Histogram mode the scan must be allowed to finish at the Stop mass before the data can be used as background.
Page 44: Changing Head Parameters
2-14 RGA Head and Scan Parameters Note: Changing scan parameters will result in loss of all displayed data on the screen. Use the File menu to save the data in one of the formats available before changing any scan parameters. Changing Head Parameters The head parameters menu items are available only when there is an SRS RGA Head connected and turned on.
Page 45: Display Modes
Display Modes 2-15 Scanning With The Filament Off The software can run experiments with the filament off. This is useful only to researchers who perform experiments that generate their own source of ions. The program will warn you if you start a scan without the filament turned on. This is done to prevent casual use and accidents.
Page 46: Changing Display Modes
2-16 Display Modes Changing Display Modes A display mode presents the user with a specific way to analyze the RGA data acquired. The RGA program has several display modes including a combination of those modes (split modes). To change the present display mode to any other mode do the following: 1.
Page 47: General Utilities
General Utilities 2-17 To Enable the Background mode make sure the graph has valid data and the RGA head is connected. In Analog and Histogram mode the scan must be allowed to finish at the Stop mass before the data can be used as background. Use the Stop at End command (if in continuous scan mode) to guarantee this condition.
Page 48: Scheduled Saving Of Data
2-18 General Utilities In PvsT mode, the cursor values are displayed in the legend box. If the legend view is toggled off you cannot see the cursor values. This off-option can be useful if the legend box obscures some data points. You may move the cursor by either clicking on or near a data point of interest, or by clicking and dragging with the mouse with the left mouse button held down.
Page 49: Browsing Through The Gas Library
General Utilities 2-19 3. Use the Next Item or Previous Item from the View menu to view the sequential logs (The time and date of the scan appears on each log). Browsing Through the Gas Library Library Browsing Description There are several ways to browse through the gas library depending on the display mode and whether the Library Search utility is active.
Page 50: Head Calibration And Security
2-20 Head Calibration and Security Analysis Procedure Make sure the RGA window is in either Analog mode or Histogram mode and connected to an RGA head. Set the scan range to be from 1 amu to at least 50 amu. 1.
Page 51: Adjusting The Cem Gain
Head Calibration and Security 2-21 Please refer to the RGA Tuning Chapter for more information about tuning and calibration. While performing the tuning procedure the total pressure in the vacuum chamber should be around 10E-6 Torr. In order to set the sensitivity factors of the RGA Head you must have a reference pressure gauge installed on your vacuum system.
Page 52: Peak Tuning The Rga Head
2-22 Head Calibration and Security Peak Tuning the RGA Head WARNING! The peak tuning procedure should be performed by qualified personnel only. A mistuned RGA Head could give erroneous readings. Please refer to the RGA Tuning chapter of this manual for more information about tuning and calibration.
Page 53: Rga On-Line Help
RGA On-line Help 2-23 • Press Undo ALL to revert to the initial settings, or • Press Factory Settings to recall factory set values. Securing the RGA Head Use this feature in an environment where you would like to restrict access to the head parameters.
Page 54: Commonly Asked Questions
2-24 RGA On-line Help To see the entries for a topic, click the first letter of the word you want to look up, or press TAB to select the letter and then press ENTER. Click on any entry highlighted in green and the topic for that entry is displayed automatically.
Page 55 Chapter 3. Measurement Techniques This chapter discusses procedures to help the user make accurate measurements with the QMS. Several sections are devoted calibration and tuning procedures. The last sections discuss specific measurement techniques. In This Chapter Calibration ..................................3-2 Effect of Total Pressure .............................3-3 Operating Off the Design Pressure........................3-3 Total Pressure and Composition........................3-4 Calibration of Partial Pressure...........................3-5...
Page 56: Calibration
3-2 Calibration Calibration The QMS has been calibrated at the factory to measure the partial pressure of nitrogen correctly. For many purposes this will be suitable. Overtime the calibration can change or operating conditions may change. There are many factors involved in calibrating the QMS and interpreting the mass spectra. To make accurate measurements, the following conditions need to be met: •...
Page 57: Effect Of Total Pressure
Calibration 3-3 Effect of Total Pressure Increasing the total pressure at the inlet of the capillary will increase the flow through the capillary. The higher flowrate in turn will increase the pressure at the RGA. This effect is not linear and in applications where the inlet pressure varies, the user needs to understand the flow at the inlet.
Page 58: Total Pressure And Composition
3-4 Calibration range of the QMS with respect to increasing the inlet pressure above the design point. The instrument has little “head-room” and the capillary should be designed for the maximum expected pressure. Below the design point, the QMS can tolerate large decreases in the inlet pressure. The ultimate vacuum of the diaphragm pump limits the lowest pressure at the outlet of the capillary, typically to 0.5 mbar.
Page 59: Calibration Of Partial Pressure
Calibration 3-5 Calibration of Partial Pressure All quantitative calculations performed with the RGA rely on the assumption that there is a linear relation between the partial pressure and the corresponding RGA signals of the gases. Each gas ionizes differently, and its ions make it through the mass filter with different efficiencies. As a result the proportionality constant relating the ion current of a gas to its partial pressure is dependent on the specific gas.
Page 60: Initial Calibration
3-6 Calibration control the filter (electron energy, focus voltage, ionizer current, and ion energy). In the equation above, the two factors are unknown. During calibration only the standard partial pressure and measured ion current are known. Therefore, both factors cannot be determined; only the overall factor can be determined.
Page 61: Basic Recalibration
Calibration 3-7 This completes the calibration. All modes of the software will now report partial pressure at the inlet to the capillary. Be sure to record these values as they can be used to diagnose system performance. The pressure reduction factor is saved in the .RGA file; make sure to select File|Save to record the new pressure reduction factor.
Page 62: Calibration For Multiple Operating Conditions
3-8 Calibration Calibration for Multiple Operating Conditions The QMS capable of being used over a variety of operating conditions, which in turn require different overall sensitivity factors. Examples are: • one QMS system used with multiple capillaries • measurements of gas streams at different total pressure, temperature, or composition •...
Page 63 Calibration 3-9 The Peak Tuning procedures described in this section allow the user to calibrate the mass scale and the resolution, ∆m , of the mass spectrometer. The RGA has a very solid design and this type of tuning procedures should rarely be needed. WARNINGS The peak tuning procedures should be performed by qualified personnel only.
Page 64: General Procedure
3-10 Calibration General Procedure Peak tuning is a simple procedure that requires the introduction of two known gases into the vacuum system. A low mass gas (1-20 amu recommended) is used to adjust the low end of the mass axis, a high mass gas, with a mass-to-charge ratio close to the upper limit of the instrument’s mass range, is used to adjust the high end of the mass scale.
Page 65: Peak Position Tuning Algorithms
Calibration 3-11 Low Mass High Mass 80 81 82 83 84 85 86 87 88 89 90 15 16 17 18 19 20 21 22 23 24 25 amu/e amu/e Users writing their own computer code can write Peak Tuning Commands for their own programs using the Tuning Commands of the RGA Command Set and the instructions of the following two sections.
Page 66: Peak Width Tuning Algorithms
3-12 Calibration scale. An increase in RI causes the low end of the analog spectrum to displace towards lower masses (A small effect is seen at the high masses). An increase in RS results in the spacing between peaks in a scan to decrease (with the largest effect seen at the high mass end).
Page 67 Calibration 3-13 (Slope), stored in the non-volatile memory of the RGA, to calculate the 8 bit settings of the DAC according to the linear equation: DAC8 (m) = DS m + DI (DC_Tweek (m) = (DAC8(m) - 128) 19.6 mV) where m is the mass in amu, and DAC8(m) is the 8 bit setting at that mass.
Page 68: Temperature Effects On The Mass Scale Calibration
3-14 Calibration • The effect is more significant at the higher masses and that is why we do this adjustment second after the width has already been modified by the change in DI. • If the mass-to-charge ratio of the low mass gas is real low this adjustment will have a small effect on the width of its peak.
Page 69: Electron Multiplier Tuning Procedure
Calibration 3-15 Electron Multiplier Tuning Procedure Accurate quantitative measurements with the electron multiplier detector require the determination of the CDEM gain for all the ion peaks being measured. Frequent recalibrations are recommended to correct against aging of the device. The gain of the electron multiplier (CDEM) in the RGA is defined relative to the Faraday Cup output (which is assumed to be mass independent).
Page 70: Techniques
3-16 Techniques Techniques Correcting for the Chamber Background Even with the sample flow and capillary flow valves closed, their will be a noticeable background in the mass spectrum. This background in the analyzer chamber is caused by outgassing from the chamber surfaces, backstreaming through the turbomolecular pump, and gas production from the ionizer of the RGA.
Page 71: Correcting For Multiple Species
Techniques 3-17 Correcting for Multiple Species As discussed above, the QMS is calibrated at one mass number. Because every gas behaves differently, analog scans can only show peak heights that are correct at the one mass number. It is not possible to correct the analog and histograms at every mass number.
Page 72 3-18 Techniques When the gas being measured is significantly hotter than the QMS system, condensation is likely and presents a problem. If the species at the inlet are gases only at temperatures above room temperature, they can condense when they reach the QMS. The condensed material will continually build up in the QMS and cover the valve seats and aperture.
Page 73: Glossary
Glossary The following is a listing of some of the most important terms used throughout the SRS RGA Operations Manual. For a more complete listing of terms relevant to partial pressure analyzers in general, refer to: “A Dictionary of Vacuum Terms used in Vacuum Science and Technology, Surface Science, Thin Film Technology and Vacuum Metalurgy”, edited by M.
Page 74 Glossary Electron Energy. The kinetic energy of the electrons (in eV) used for electron bombardment in the ionizer. Note: In the SRS RGA the Electron Energy is equal to the voltage difference (in Volts) between the filament and the anode grid. Electronics Control Unit (abbreviation: ECU).
Page 75 Glossary Ionization efficiency. The ionization probability normalized to the probability of ionization of a reference gas. Ionization Potential. The minimum energy per unit charge (often in eV) required to remove an electron from an atom (or molecule) to infinite distance. Note: In the SRS RGA the Electron energy must be set above the ionization potential of the molecules for ionization to occur.
Page 76 Glossary cannot be differentiated from each other with most mass spectrometers. Note: Mass spectrometers do not actually measure the molecular mass directly, but rather the mass-to-charge ratio of the ions. For singly charged ions, the mass to charge ratio is numerically equal to the mass of the ion in atomic mass units (amu).
Page 77 Glossary Response time - is a measure of the steepness of the response when a step change is presented at the inlet. RGA - residual gas analyzer (a class of QMS) RGA Cover Nipple. CF Nipple that covers the RGA Probe. Scan Speed (mass spectrometer).
Page 78 References General RGA information Dawson, “Quadrupole Mass Spectrometery and Its Applications”, AIP Press, NY, 1995. Drinkwine and D. Lichtman, “Partial Pressure Analyzers and Analysis”, AVS Monograph Series published by the Education Committee of the American Vacuum Society Basford et. al., J. Vac. Sci. Technol., A 11(3) (1993) A22-40: “Recommended Practice for the Calibration of Mass Spectrometers for Partial Pressure Analysis.
Page 79 Technical Reference Manual QMS 100 Series Gas Analyzer Version 3.2 (1/2012)
Page 80 Certification Stanford Research Systems certifies that this product met its published specifications at the time of shipment. Warranty This Stanford Research Systems product is warranted against defects in materials and workmanship for a period of one (1) year from the date of shipment. Service For warranty service or repair, this product must be returned to a Stanford Research Systems authorized service facility.
Page 81 Table of Contents Safety ................................... iv Specifications .................................v Materials List ................................vii Command List ................................viii Chapter 1. Principles of Operation ..........................1-1 Internal View ..............................1-2 Overall System ............................... 1-3 Pressure Reducing Inlet ..........................1-5 Capillary Design ............................1-10 Chapter 2.
Page 82: Safety
Safety Line Voltage The QMS system is specified for power line of either 110 V / 60 Hz or 220 V / 50 Hz. The diaphragm pump will only operate on the specified voltage. Operating at other voltages will damage the motor. For 110 V operation use one 3 A fuse. For 220 V operation, two 1.5 A fuses must be used in the power entry module.
Page 83: Specifications
Specifications Inlet Type capillary: available in stainless steel, PEEK, and glass lined plastic Flowrate 1 to 10 milliliter per minute at atmospheric pressure Response time <400 ms Pressure selectable from 10 mbar to 1 bar Mass Spectrometer Operational: Mass filter type Quadrupole (Rod diameter: 0.25”, rod length: 4.5”) Detector type...
Page 84 Recommended bakeout 100 - 250 C temperature Ionizer: Design Open ion source. Cylindrical symmetry Operation Electron impact ionization. Material SS304 construction Filament Thoriated Iridium (dual) with firmware protection. Field replaceable. Degas 1 to 10 W Degas ramp-up. Electron energy 25 to 105 V, programmable. Ion energy 8 or 12 V, programmable.
Page 85: Materials List
Materials List SRS receives many requests for information about corrosion compatibility. It is our policy not to state the compatibility of our system with various corrosive environments. We simply cannot test the myriad combinations of environments that our customers use. We do provide a list of all the materials exposed to the gas being introduced into the system.
Page 86: Command List
viii Command List Initialization Name Description Parameters Echo Identification Query ID String Initialization 0,1,2 STATUS Byte Ionizer Control Name Description Parameters Echo Degas Ionizer 0-20, * STATUS Byte Electron Energy 25-105, *, ? STATUS Byte or query response Electron Emission Current 0-3.50, *, ? STATUS Byte or query response...
Page 87 Initial Mass 1-M_MAX, *, ? Query response Single mass measurement 0, M_MAX Ion Current Steps per amu 10-25,*,? Query response Analog Scan Trigger 0-255,*, none Ion Currents Total Pressure measurement 0, 1, ? Ion Current Parameter Storage Name Description Parameters Echo CDEM gain storage 0.0000-2000.0000,?
Page 88 DET_ERR Byte Query Query response QMF_ERR Byte Query Query response CEM_ERR Byte Query Query response FIL_ERR Byte Query Query response RS232_ERR Byte Query Query response Note: M_MAX= 100 for RGA100, 200 for RGA200 and 300 for RGA300. SRS QMS Gas Analyzer...
Page 89 Chapter 1. Principles of Operation The QMS consists of two main subsystems: the gas handling inlet and the mass spectrometer. These two subsystems operate independently of each other. The gas handling subsystem delivers the sample to the spectrometer chamber. It has no control of the spectrometer or communications with it. The spectrometer only analyzes the sample.
Page 90: Internal View
1-2 Internal View Internal View Figure 1. Main components of the QMS are labeled: 1. microcontroller 2. aperture 3. sample valve 4. pressure gauge 5. bypass valve 6. quadrupole electronics 7. mass spectrometer 8. analyzer chamber 9. 24V power supply 10. turbo pump controller 11.
Page 91: Overall System
Overall System Overall System The QMS was designed to be a self contained instrument. Only line power is required to operate the instrument. One serial cable between the instrument and a computer is required to run the software. No ancillary gas supplies are necessary. Power Internally the QMS uses line power (110 or 220) and 24 VDC.
Page 92: Structure
1-4 Overall System The pressure gauge operates on 15 VDC, which is provided by the microcontroller. The gauge has on- board electronics that provide a setpoint comparison. The setpoint check is used by the microcontroller to determine if the system is operating acceptably. The gauge also outputs an analog signal related to the pressure.
Page 93: Pressure Reducing Inlet
Pressure Reducing Inlet Pressure Reducing Inlet The gas handling subsystem is designed to achieve several goals: • reduce the pressure of the sample gas to the operating range of the mass spectrometer (<10 mbar) • provide a quick response time to changes of sample composition at the inlet •...
Page 94: Flow Calculations
1-6 Pressure Reducing Inlet Flow Calculations The pressure and flowrates of the sampled gas can be calculated with simple formulas. The calculations here assume that gases behave ideally, which is a reasonable approximation at the temperatures and pressures involved. Actual system performance compares well with these simple calculations. The pressure drop across a length of tube is related to the flowrate and dimensions by: −...
Page 95 Pressure Reducing Inlet where C is the conductivity of the tube from the tee to the diaphragm pump. The flow through the aperture is: − ≅ sample where again the large pressure drop allows the approximation to be used. The turbo pump is an active component that is characterized by sample where S is the speed of the pump and has the same units as conductivity (liter s...
Page 96: Diaphragm Pump
1-8 Pressure Reducing Inlet These last two characteristics greatly simplify the selection of alternate capillaries and is discussed later in this chapter. Diaphragm Pump A measured speed curve for the diaphragm pump is shown in the figure at the right. The speed is the volumetric flowrate at that pressure.
Page 97: Turbo Pump
Pressure Reducing Inlet Turbo Pump The pump attached to the spectrometer chamber is hybrid turbomolecular/drag pump. The turbo pump hybrid design of this pump allows it to diaphragm pump exhaust at high pressure (relative to conventional turbomolecular pumps). The pumping speed is constant at the nominal value of 70 over a large range of exhaust pressures.
Page 98: Capillary Design
1-10 Capillary Design Capillary Design The inlet uses a bypass configuration that results in a fast response time. A large flow is drawn through the capillary tube, which drops the pressure 3 decades. The typical capillary used at atmospheric pressure has a bore diameter of 0.125 mm and a length of 0.7 m. Any number of combinations of length and bore diameter can achieve the same flowrate and pressure drop.
Page 99 Capillary Design 1-11 The chromatography industry uses a large variety of capillaries, from which we can select capillaries for the QMS. The figure below shows the conductivity for several commonly available bore diameters. 1E-02 1E-03 1E-04 1E-05 1E-06 1E-07 1E-08 1000 length (cm) Figure 6.
Page 100: Materials And Fittings
1-12 Capillary Design Materials and Fittings Users will find vendors of gas chromatography supplies a good source for capillaries and fittings. Capillaries are available in many materials. No material is ideal for all applications. The following table list features of several materials material min.
Page 101: Extensions
Capillary Design 1-13 Extensions As discussed in the previous section, the capillary can be designed to any length necessary by choosing an appropriate bore diameter. The cost of material might warrant the use of an extension of another material, e.g. common vinyl tubing. This can be accomplished as long as the extension is added to the vacuum side of the capillary: CORRECT 3 mm ID x 4m L...
Page 102 ...
Page 103 Chapter 2. Quadrupole Spectrometer This chapter describes the design and principles of operation of the components of the RGA quadrupole probe. In This Chapter Introduction ..................................2-2 ECU......................................2-3 RS232/DCE/28.8k Connector.............................2-3 Calibration Lockout..............................2-3 Electrometer..................................2-5 Detection limit vs. scan rate............................2-5 Adjusting the Zero of the Ion Detector........................2-6 Mass Filter Power Supply ..............................2-7 Ionizer....................................2-8 Description ..................................2-8...
Page 104: Introduction
2-2 Introduction Introduction The SRS RGA is a mass spectrometer consisting of a quadrupole probe, and an Electronics Control Unit (ECU) which mounts directly on the probe’s flange and contains all the necessary electronics for operating the instrument. Figure 1 Quadrupole Head Components The probe is a specially engineered form of quadrupole mass spectrometer sensor.
Page 105: Ecu
ECU 2-3 Independently from the gas handling susbsystem, the ECU completely controls the operation of the spectrometer, handles its data and transmits it to the computer for analysis and display. The ECU is a densely packed box of electronics (3”x4”x9”) that connects directly to the probe’s feedthru-flange and also to a host computer.
Page 106 2-4 ECU changes in the calibration parameters by inexperienced operators. Peak tuning is completely disabled when the jumper is configured to the CAL DIS setting. SRS QMS Gas Analyzer...
Page 107: Electrometer
Electrometer 2-5 Electrometer Detection limit vs. scan rate A unique, temperature-compensated, logarithmic picoammeter built into the ECU box measures the ion currents collected by the Faraday cup (FC), or electron multiplier (CDEM). The output voltage of the electrometer is equal to the logarithm of the ion current so that several decades of signal can be read on the meter without any gain switching being necessary.
Page 108: Adjusting The Zero Of The Ion Detector
2-6 Electrometer When using the RGA Windows program to operate the RGA, the Scan Speed parameter setting available in the Scan Parameter Setups of the Scan menu is used to set the NF parameter value in the RGA Head according to the equation: NF = ScanSpeed - 1. The following table summarizes the performance of the RGA electrometer during mass measurements as a function of the Scan Speed and NF settings.
Page 109: Mass Filter Power Supply
Mass Filter Power Supply 2-7 Mass Filter Power Supply All the necessary electronics required to power up the quadrupole mass filter during mass measurements are built into the ECU box. The RF/DC levels for each mass are set and regulated from the ECU, under microprocessor control, and based on internal calibration parameters permanently stored in non-volatile memory.
Page 110: Ionizer
2-8 Ionizer Ionizer Positive ions are produced in the ionizer by bombarding gas molecules with electrons derived from a heated filament. The ions are then directed toward the entrance of the ion filter where they are separated based on their mass-to-charge ratio. Description The SRS RGA ionizer is of an open design (wire mesh construction) with cylindrical symmetry and mounted co-axially with the filter assembly.
Page 111: Principle Of Operation
Ionizer 2-9 Principle of operation The principle of operation of the ionizer is similar to the Bayard-Alpert gauge, except there is no central wire collector, and the electron repeller has been added. Figure 4 Ionizer Schematic The filament is the source of the electrons used in ionizing the gas molecules. It operates at a negative potential relative to ground and is resistively heated to incandescence with an electrical current from the emission regulator.
Page 112: Parameter Settings
2-10 Ionizer Parameter Settings The parameters that affect the ionization efficiency of the ionizer are: electron energy, ion energy, electron emission current and focusing voltage. The general principles by which they affect the performance of the source are well understood. The ECU contains all the necessary high voltage and current supplies needed to bias the ionizer’s electrodes and establish an electron emission current.
Page 113 Ionizer 2-11 Ion energy also determines the time spent by the ions in the fringing fields at the entrance and exit points of the filter. Ions passing through the fringing fields can collect high transverse velocities and are more likely to collide with the quadrupole rods and never be collected at the detector. As a result, ion signals (i.e.
Page 114: Quadrupole Mass Filter
2-12 Quadrupole mass filter Quadrupole mass filter Positive ions are transferred from the ionizer into the quadrupole where they are filtered according to their mass-to-charge ratios. Ions that successfully pass through the quadrupole are focused towards the detector by an exit aperture held at ground potential. Description The quadrupole mass filter is an electrodynamic quadrupole operated by a combination of DC and RF voltages.
Page 115: Principle Of Operation
Quadrupole mass filter 2-13 potential terms. The radius of the circle inscribed by the rods is 0.109”. The frequency of operation is f=2.7648 MHz. Principle of operation The following figure schematically represents the quadrupole mass filter and its connections. Figure 6 Quadrupole Connections During operation, a two dimensional (X-Y) quadrupole field is established between the four cylindrical electrodes with the two opposite rods connected together electrically.
Page 116: Mass Range, Resolution And Throughput
2-14 Quadrupole mass filter compared to other types of analyzers. The upper limit of useful operation is determined by the collisions between the ions and the neutral gas molecules. In order to avoid collisional scattering it is necessary to maximize the mean free path of the ions. The general principle of operation of the filter can be visualized qualitatively in the following terms: One rod pair (X-Z plane) is connected to a positive DC voltage upon which a sinusoidal RF voltage is superimposed.
Page 117 Quadrupole mass filter 2-15 The mass range is the range of masses defined by the lightest and the heaviest singly charged ions which can be detected by the mass spectrometer. The spectrometer is offered in three different models with mass ranges of 1 to 100, 200, and 300 amu. The main difference between the three models is given by the maximum supply voltage available to the rods.
Page 118: Zero Blast Suppression
2-16 Quadrupole mass filter It is well established that the resolution attainable by a quadrupole is limited by the number of cycles of RF field to which the ions are exposed before they reach the detector. In practice, the minimum resolution (∆M ) value attainable is mass independent, linearly related to the ion energy, and inversely proportional to the square of the product of the quadrupole length and frequency.
Page 119: Ion Detector
Ion Detector 2-17 Ion Detector Positive ions that successfully pass through the quadrupole are focused towards the detector by an exit aperture held at ground potential. The detector measures the ion currents directly (Faraday Cup) or, using an optional electron multiplier detector, measures an electron current proportional to the ion current.
Page 120: Faraday Cup Operation
2-18 Ion Detector mounting the CDEM cone very close to the top of the FC. The clip anchors the CDEM glass tube to the side of the FC Shield and holds the lower end of the tube at ground. Chrome electrical coatings, deposited at both ends of the tube provide the necessary electrical contacts.
Page 121 Ion Detector 2-19 of the electron multiplier currents is reversed before the current value is sent out over RS232 so that the computer does not need to do any sign flipping on the currents received when the CDEM is activated. The gain of the electron multiplier in the RGA is a function of the bias voltage and is measured relative to the FC signal.
Page 122 2-20 Ion Detector along the channel walls replenishing their charge as secondary electrons are emitted. Channel electron multipliers, operate linearly in the analog mode until the output current is approximately 10% of the bias current. The dark current of a multiplier is the electron current measured at its output in the absence of an input ion current.
Page 123 Ion Detector 2-21 applications. However, in order to achieve maximum useful lifetime and optimum performance, it is very important to handle them very carefully. Please read the CDEM Handling and Care section in the Service chapter to familiarize yourself with some of the basic procedures that must be followed for the correct operation of the multipliers.
Page 124 ...
Page 125: Chapter 3. Programming The Rga
Chapter 3. Programming the RGA This chapter describes how to program the RGA ECU from a host computer using the RGA Command Set and an RS232 Link. In This Chapter Introduction ..................................3-3 The RGA COM Utility ..............................3-4 Command Syntax................................3-5 Examples of command formats..........................3-5 Programming tips................................3-6 Communication Errors ..............................3-7 Command errors ................................3-7...
Page 126 3-2 Introduction MIparam, param: 1 - M_MAX, *, ? ........................3-44 MRparam, param:0 - M_MAX........................3-44 SAparam, param: 10 - 25, *, ?...........................3-46 SC[param], param: 0 - 255, *..........................3-47 TP?, TP0, TP1 ..............................3-49 Parameter Storage Commands..........................3-51 MGparam, param: 0.0000 - 2000.0000,?......................3-51 MVparam, param: 0 - 2490,?..........................3-51 SPparam, param:0.0000 - 10.0000, ?.........................3-52 STparam, param:0.0000 - 100.0000, ?.......................3-53 Mass Filter Control Commands..........................3-54...
Page 127: Introduction
Introduction 3-3 Introduction The RGA comes standard with an RS232 communications port. A host computer interfaced to the RGA can easily configure, calibrate, diagnose and operate the quadrupole mass spectrometer using ASCII commands. The RGA ECU executes the commands in the order received and, when information is requested, data is quickly returned to the computer for analysis and display.
Page 128: The Rga Com Utility
3-4 The RGA COM Utility The RGA COM Utility The RGA Com Utility is a simple Windows™ OS communication program that allows you to communicate with the RGA ECU directly by typing valid RGA commands on your keyboard. The program functions like any common terminal program where the typed characters are sent directly to the serial communications port and any received characters are displayed immediately on the screen.
Page 129: Command Syntax
Command Syntax 3-5 Command Syntax The RGA commands are ASCII character strings consisting of a two letter (case insensitive) command name, a parameter, and a carriage return terminator. Note: The carriage return character, decimal ASCII value=13, is represented throughout this manual with the symbol <CR>.
Page 130: Programming Tips
3-6 Command Syntax RGA Identification Query. Set initial scan mass to 1 amu. MF100 Set final scan mass to 100 amu. FL1.0 Turn on the filament to a 1.0 mA emission current. Use default noise floor setting. (sets scan rate and averaging.) Query the number of scan points to be received by the computer.
Page 131: Communication Errors
Communication Errors 3-7 Communication Errors Communication errors are signaled to the user flashing the Error LED a few times, setting Bit 0 of the STATUS error byte and setting the error-specific bits of the RS232_ERR error byte . Many different circumstances can result in a communication error being reported after a command string is received by the RGA.
Page 132: Jumper Protection Violation
3-8 Communication Errors Jumper Protection Violation Some calibration related commands are subject to jumper protection. Jumper JP100 on the digital (i.e. top) board of the RGA electronics box can be used to enable/disable some of the tuning features of the instrument.
Page 133: Programming The Rga Ecu
Programming the RGA ECU 3-9 Programming the RGA ECU This section describes the basic programming steps needed to configure, operate, and diagnose the RGA. The emphasis is on general program implementation without going into specific details on the different commands that are mentioned. Please consult the “RGA Command Set”...
Page 134: Programming The Ionizer
3-10 Programming the RGA ECU -Check the quality of the serial connection to the host computer. -Check the user’s communication software to make sure it is communicating properly with the RGA. -Check the serial numbers of the RGA ECU’s connected to the computer's serial ports. Programming the Ionizer Positive ions are produced in the ionizer by bombarding residual gas molecules with electrons derived from a heated filament.
Page 135: Programming The Detector
Programming the RGA ECU 3-11 Programming the Detector Positive ions that successfully pass through the quadrupole filter are focused towards a detector that measures the ion currents directly (Faraday Cup, FC) or, using an optional electron multiplier (CDEM), measures an ion signal proportional to the ion current. Use the Detection Control commands to choose the detector type (FC or CDEM), query the CDEM option, recalibrate the electrometer’s I-V response and set the electrometer’s averaging and bandwidth.
Page 136 3-12 Programming the RGA ECU Please consult the RGA Command Set section for details on the CA command. Detector Programming example The following list of commands starts by checking the RGA ECU to make sure there is a multiplier installed: A CDEM is present if a 1<LF><CR> response is sent back to the computer. After the test (and assuming the CDEM option was detected), a voltage of -1400V is set across the multiplier, and the noise floor setting is programmed for minimum averaging and maximum scan rate.
Page 137: Setting Up Analog Scans
Programming the RGA ECU 3-13 • Follow all recommended procedures for the operation of the CDEM. Consult the RGA Maintenance chapter for complete CDEM Care and Handling information. Setting up Analog Scans Analog scanning is the most basic operation of the RGA as a quadrupole mass spectrometer. During analog scanning the quadrupole mass spectrometer is stepped at fixed mass increments through a pre- specified mass-range.
Page 138: Setting Up Histogram Scans
3-14 Programming the RGA ECU MF150 Final mass = 150 amu. Fastest scan rate selected. SA10 Steps/amu = 10. Analog Points query. The number 1401 is echoed. Add one for total pressure. SC10 Analog Scan trigger: 10 scans are generated and transmitted. Analog Scan Programming Tips •...
Page 139 Programming the RGA ECU 3-15 Histogram scans are triggered with the HS command. The scan parameter can be set for single, multiple and continuous scanning operation. The mass range for the scan is set in advance with the commands MI (Initial Mass) and MF (Final Mass). A current value is transmitted for each integer mass value between MI and MF for a total of (MF-MI +1) measurements (See HP command).
Page 140: Single Mass Measurements
3-16 Programming the RGA ECU • Any command sent to the RGA during scanning will immediately halt the scanning action and clear the RGA’s transmit buffer. Remember to also clear the computer’s receive buffer to reset the communications. The new command responsible for stopping the scan will be executed! •...
Page 141 Programming the RGA ECU 3-17 scanning procedure, referred to as Peak-Locking, is designed to measure peak currents for individual masses in a mass spectrum without being affected by drifts in the mass scale calibration. The Miniscan covers a 0.6 amu range centered at the mass requested, and selects the maximum current from 7 individual measurements performed at 0.1 amu mass increments.
Page 142: Total Pressure Measurements
3-18 Programming the RGA ECU • The output of a D/A converter can be linearly related to the readings obtained at a certain mass. • A relay switch can be closed whenever another mass concentration goes above a certain level. •...
Page 143: Storing Information In The Rga Ecu
Programming the RGA ECU 3-19 gauge readings. Expect to see deviations between the two gauges as the composition of a residual gas changes. Total Pressure measurement example The following list of commands is an example of a total pressure measurement setup. The first step sets up the FC as the detector, and automatically sets the TP_Flag = 1.
Page 144: Programming The Quadrupole Mass Filter
3-20 Programming the RGA ECU CDEM gain at the HV setting stored in MV. See MG command. See the Parameter Storage commands list in the next section for details. Important: • The Parameter Storage commands are used by the RGA Windows software to store and retrieve the partial and total pressure sensitivity factors, and the gain and voltage settings of the CDEM calculated and used by the program.
Page 145: Error Checking The Rga
Programming the RGA ECU 3-21 The net result is very stable RF/DC levels that are highly insensitive to the operating conditions of the RGA ECU. Important: The RF/DC stabilization algorithm (Step 2 above) remains active as long as no new commands are detected by the RGA ECU.
Page 146 3-22 Programming the RGA ECU The Burnt and Leak LED’s indicate specific filament problems and are turned on, in addition to the Error LED, whenever the ionizer’s emission is internally shut down or not established as requested. Error Queries: Queering the Error Bytes with the Error Reporting commands. The “Error Byte Definitions”...
Page 147 Programming the RGA ECU 3-23 The Error LED is immediately turned on if any one of the bits 1-7 of STATUS is set. Bit 0 of STATUS reports communications errors and the Error LED is only flashed twice when the bit is set. The STATUS Byte should be queried regularly by the programming software (ER? command.) Commands that involve hardware control (such as Ionizer Control commands) do diagnostic checks on the hardware as they are executed.
Page 148 3-24 Programming the RGA ECU The RGA is turned on and, after all the internal checks are performed, the green Power LED and the Error LED are turned on. The red LED signals the operator that a problem was detected. A 24V P/S error is not expected since the Power LED is on.
Page 149: Rga Command Set
RGA Command Set 3-25 RGA Command Set This section lists and describes the commands of the RGA’s Command Set. The commands are separated into several lists, based on their functions. They are each identified by a header that describes the command’s syntax (with the acceptable parameter values), the command’s function, and the information returned (echo) to the computer during execution.
Page 150: Initialization Commands
3-26 RGA Command Set Initialization Commands Description: Identification query. Echo: ID string. Use to identify the RGA ECU connected to the host computer. The RGA returns the ID string (ASCII format): SRSRGA###VER#.##SN#####<LF><CR> The three string parameters, in the exact format shown above, correspond to: 1.
Page 151 RGA Command Set 3-27 Initialize the RGA to a known state. Three different levels of initialization are available. Command excecution times vary depending on the pre-existing ionizer conditions. The end of the command excecution is prompted to the host computer returning the STATUS byte over RS232. Parameters: IN0: Initialize communications and check the ECU hardware.
Page 152: Dgparam, Param: 0 - 20
3-28 RGA Command Set Ionizer Control Commands DGparam, param: 0 - 20,* Description: Ionizer Degas command Echo: STATUS error byte (unless command is stopped before completion, or param=0). DEGAS the ionizer by heating and electron stimulated desorption. The parameter represents the desired DEGAS time in minutes and includes a one minute initial ramping time.
Page 153 RGA Command Set 3-29 8. At the end of the time specified by the parameter (and if no problems were encountered) the Degas_LED is turned off. 9. Ionizer goes back to pre-Degas configuration 10. The electron emission current is reprogrammed to its pre-Degas value and background filament protection is reenabled.
Page 154: Flparam, Param: 0.00 - 3.50
3-30 RGA Command Set Command excecution times vary depending on the pre-existing ionizer conditions. The end of the command excecution is prompted to the host computer by sending out the STATUS byte over RS232. Note: The Electron Impact Ionization Energy is set to the default value when the unit is turned on. Important: The repeller grid and the focus plate are only biased while the filament is emitting electrons.
Page 155: Ieparam, Param: 0,1
RGA Command Set 3-31 • The repeller grid and the focus plate are only biased while the filament is emitting electrons. • In order to protect the filament, the emission current is defaulted to zero when the RGA is turned on. •...
Page 156: Vfparam, Param: 0 - 150
3-32 RGA Command Set Since the axis of the quadrupole mass filter is at ground, the ion energy (in eV) is equal to the anode grid voltage (in Volts). Important: The anode grid is always biased regardless of the ionizer’s emission status. Upon reset the grid level is set to the default value.
Page 157 RGA Command Set 3-33 Command excecution times vary depending on the pre-existing ionizer conditions. The end of the command excecution is prompted to the host computer sending out the STATUS byte over RS232. Parameters: VFparam, param: 0-150: The parameter represents the magnitude of the focus plate bias potential in Volts (The actual bias voltage is negative).
Page 158: Detection Control Commands
3-34 RGA Command Set Detection Control Commands Description: Calibrate All. Echo: STATUS Error Byte. Readjust the zero of the ion detector under the present detector settings, and correct the internal scan parameters against small temperature fluctuations to assure that the correct RF voltages (i.e. as specified by the last Peak Tuning procedure) are programmed on the QMF rods as a funtion of mass.
Page 159 RGA Command Set 3-35 Notes: • This mass axis correction procedure can also be triggered at any time, by itself, using the RS and RI commands with no parameters (See Tuning commands). • The correction procedure is also automatically performed at the beginning of all analog and histogram scans.
Page 160: Hvparam, Param: 0 - 2490
3-36 RGA Command Set • All offset correction factors previously stored in memory are cleared after a complete calibration of the electrometer is performed (see CA command for more information). Parameters: Only one possible command format is allowed Error Checking: An attempt to pass any parameter with CL results in a bad-parameter error being reported.
Page 161 RGA Command Set 3-37 • It is good practice to readjust the Zero of the ion detector every time the type of detector (FC or CDEM) is changed. This is particularly important if the new detector settings have not been used in a long time or since the unit was turned on or recalibrated with the CL command.
Page 162: Nfparam, Param: 0 - 7
3-38 RGA Command Set Error Checking: The CDEM option (Opt01) must be available in the RGA ECU receiving the command or a bad- command error is reported (see MO command for details). Number parameters must be within the accepted range, and must be integers. No parameter (i.
Page 163 RGA Command Set 3-39 A decrease in the Noise-Floor setting results in cleaner baselines and lower detection limits during scans and measurements, but also means longer measurement and scanning times due to the reduced bandwidth of the electrometer and increased averaging. The NF parameter must be chosen keeping in mind the strong interplay between detection limit and acquisition speed.
Page 164: Scan And Measurement Commands
3-40 RGA Command Set Scan and Measurement Commands Description: Analog Scan Points Query. Echo: Query Response. Query the total number of ion currents that will be measured and transmitted during an analog scan under the current scan conditions. Important: The query response does not include the extra current (4 bytes) corresponding to the total pressure measurement performed at the end of all analog scans (Please see SC command for details).
Page 165: Hsparam, Param:0 - 255
RGA Command Set 3-41 Important: The query response does not include the extra current (4 bytes) corresponding to the total pressure measurement performed at the end of all histogram scans. (Please see HS command for details). The number of points (ion currents) retuned over RS232 is calculated based on the MI and MF parameter values.
Page 166 3-42 RGA Command Set • The detector’s zero and the internal scan parameters are checked and corrected at the beginning of each scan resulting in a slight delay before the scan actually starts. • A Total Pressure measurement is performed at the end of each scan and transmitted out to the host computer (Please see HP and TP Commands).
Page 167: Mfparam, Param: 1 - M_Max
RGA Command Set 3-43 computer over RS232. As a result of the high acquisition rate of the RGA there might be a delay between the time at which the data is collected and the time at which a complete spectrum is displayed by the host computer. The time lag between data acquisition and display depends on a large number of factors including the scan rate (NF setting) of the RGA, the host computer’s processing speed, and the amount of handshaking activity over the RS232...
Page 168: Miparam, Param: 1 - M_Max
3-44 RGA Command Set The mass value set by MF must always be greater than or equal to the initial mass setting of MI or else a parameter-conflict communications error is generated. The absence of a parameter (i.e. MF) is treated as a bad-parameter error. MIparam, param: 1 - M_MAX, *, ? Description: Initial Mass (amu) of mass spectra (Analog and Histogram).
Page 169 RGA Command Set 3-45 The type of detector and noise-floor settings to be used by the measurement must be selected in advance with the NF and HV commands. The precision and duration of the measurement are totally determined by the NF parameter value. The scan rates and signal-to-noise ratios for the different NF settings of the electrometer are listed in a table in the Electrometer section of the “RGA Electronic Control Unit”...
Page 170: Saparam, Param: 10 - 25
3-46 RGA Command Set The upper mass limit depends on the RGA model number: M_MAX=100 for RGA100, 200 for RGA200 and 300 for the RGA300. Error Checking: The command does not accept query or default parameters. Programming tips: • Single mass measurements are commonly performed in sets where several different masses are monitored sequencially and in a merry-go-round fashion.
Page 171: Sc[Param], Param: 0 - 255
RGA Command Set 3-47 Parameters: SAparam, param: 10-25: The parameter specifies the number of steps-per-amu desired during analog scans. SA*: The number of points per amu value is set to its default value. Default: 10 SA?: Query. Returns the SA parameter value currently in use by the analog scans. Error checking: Number parameters must be integers and within the specified range.
Page 172 3-48 RGA Command Set • A Total Pressure measurement is performed at the end of each scan and transmitted out to the host computer (Please see AP and TP Commands). • Unless otherwise specified, the measurements are performed with the detector settings that are present at the time the scan is triggered.
Page 173: Tp?, Tp0, Tp1
RGA Command Set 3-49 received to the time it actually starts. Using the SC1 command and waiting until the whole scan data stream is transmitted back to the host computer will minimize the problems that are associated to this feature. •...
Page 174 3-50 RGA Command Set different from that of the Bayard Alpert gauge readings. Expect to see deviations between the two gauges as the composition of a residual gas changes. Parameters : TP0: TP_Flag is cleared. Total Pressure measurement is disallowed and a null current value is returned as a response to a total Pressure Measurement request (note that this includes the total pressure measurement requests at the end of scans!).
Page 175: Parameter Storage Commands
RGA Command Set 3-51 Parameter Storage Commands MGparam, param: 0.0000 - 2000.0000,? Description: Electron Multiplier Gain Storage. Echo: Query Response. Store a value of electron multiplier (CDEM) Gain, expressed in units of thousands, in the non-volatile memory of the RGA ECU. The command is typically used together with the MV instruction to store calibrated sets of [High Voltage and gain] for the Electron Multiplier.
Page 176: Spparam, Param:0.0000 - 10.0000
3-52 RGA Command Set Important: The voltage value is not used internally by the RGA to set the bias voltage of the Electron Multiplier, it is simply stored so it can be read and used by a host computer. As expected, this command is only available in ECU’s with a CDEM option installed (See MO command for details).
Page 177: Stparam, Param:0.0000 - 100.0000
RGA Command Set 3-53 STparam, param:0.0000 - 100.0000, ? Description: Total Pressure Sensitivity Factor storage. Echo: Query Response Store a value of Total Pressure Sensitivity, expressed in units of mA/Torr, in the non-volatile memory of the RGA ECU. Important: The sensitivity factor is not used internally by the RGA to turn ion currents into total pressures, it is simply stored so it can be read and used by any host computer connected to the instrument.
Page 178: Mass Filter Control Commands
3-54 RGA Command Set Mass Filter Control Commands MLparam, param: 0.0000 - M_MAX Description: Mass Lock Echo: none Activate the quadrupole mass filter (QMF) and center its pass-band at the mass value specified by the parameter. The QMF is parked at the mass requested but no ion current measurements take place. The parameter is a real number and the mass increments are limited to a minimum value of 1/256 amu.
Page 179: Error Reporting Commands
RGA Command Set 3-55 Error Reporting Commands Description: RS232_ERR Byte Query Echo: RS232_ERR Byte. Query the value of the RS232_ERR byte. The value of the RS232_ERR byte is sent to the computer in ASCII format and with a <LF><CR> terminator. RS232_ERR and bit 0 of STATUS are then cleared to provide a clean error reporting slate.
Page 180 3-56 RGA Command Set Error checking: The only acceptable parameter is a question mark. The absence of a parameter (i. e. ED) is treated as a bad-parameter error. Description: FIL_ERR Byte Query Echo: FIL_ERR Byte. Query the value of FIL_ERR. The FIL_ERR byte value is returned to the computer in ASCII format and with a <LF>...
Page 181 RGA Command Set 3-57 This query command can be used to determine whether the CDEM option is installed in the RGA unit being programmed: A CDEM option is available if Bit 7 of CEM_ERR is cleared when the byte is queried (See also MO command).
Page 182 3-58 RGA Command Set results). The QMF_ERR byte value is returned to the computer in ASCII format and with a <LF><CR> terminator. No errors are present as long as the byte value is zero. Consult the Error Byte Definitions section of this chapter for detatils on the different error bytes of the RGA.
Page 183 RGA Command Set 3-59 Error checking: The only acceptable parameter is a question mark. The absence of a parameter (i. e. ER) is treated as a bad-parameter error. Technical Reference...
Page 184: Tuning Commands
3-60 RGA Command Set Tuning Commands Description: Calibration Enable Query. Echo: JP100 setting. Query the Calibration Enable/Disable jumper (JP100) status. An internal jumper (JP100) on the digital (i.e. top) electronics board of the RGA’s ECU box can be configured by the end-user to enable/disable the modification of the peak tuning parameters.
Page 185: Dsparam, Param: -0.8500 - +0.8500
RGA Command Set 3-61 non-volatile memory of the RGA, to calculate the 8 bit settings of the DAC according to the linear equation: DAC8 (m) = DS m + DI where m is the mass in amu, and DAC8(m) is the 8 bit setting at that mass. The purpose of the Peak Width Tuning Procedure is to determine the values of DI and DS so that all the peaks in an analog spectrum have the desired peak width (typically 1 amu).
Page 186 3-62 RGA Command Set Program the value of DS during the Peak Width Tuning Procedure. The parameter (one of four peak tuning parameters) represents the DS value, in units of bits/amu. Warning: Please read the Peak Tuning Section of the RGA Tuning Chapter before using this command. The RGA ECU adjusts the DC levels of the quadrupole filter during measurements so that constant mass resolution is automatically available throughout the entire mass range of the spectrometer.
Page 187: Riparam, Param: -86.0000 - +86.0000, *, ?, None
RGA Command Set 3-63 RIparam, param: -86.0000 - +86.0000, *, ?, none Description: RF_Driver output @ 0 amu (Peak Position Tuning command). JP100 Jumper protected. Echo: Query Response. Warning: Please read the Peak Tuning Section of the RGA Tuning Chapter before using this command. Program the output of the RF_Driver @ 0 amu during a Peak Posion Tuning Procedure.
Page 188 3-64 RGA Command Set Error checking: The absence of a parameter (i. e. RI) is treated as an error in the parameter. This parameter is protected by an internal calibration jumper (JP100) and a Protection-violation error will result if the jumper is in the Calibration Disabled mode (see CE command). RSparam, param: 600.0000 - 1600.0000, *, ?, none Description: RF_Driver output @ 128 amu (Peak Position Tuning command).
Page 189 RGA Command Set 3-65 RS: Uses the current parameter value to recalculate the internal scan parameters used to step the RF during scans and single mass measurements. This is often used to compensate against small temperature drifts in the mass scale, caused by drifts in the output of the RF_Driver. Error checking: The absence of a parameter (i.
Page 190: Error Byte Definitions
3-66 Error Byte Definitions Error Byte Definitions The Error Bytes described in this section store the results of the firmware-driven checks built into the RGA ECU. Use the Error Reporting commands to query the value of the bytes. Important: No errors are present as long as all bits in the Error Bytes are cleared. The RGA Windows software supports all the Error Reporting commands and reports the errors detected based on their Error Codes.
Page 191 Error Byte Definitions 3-67 PS_ERR Error Byte: 24V P/S Error Byte. Description Error Code External 24V P/S error: Voltage >26V. External 24V P/S error: Voltage <22V. Not used Not Used Not Used Not Used Not Used Not Used DET_ERR Error Byte: Electrometer Error Byte. Description Error Code ADC16 Test failure.
Page 192 3-68 Error Byte Definitions QMF_ERR Error Byte: Quadrupole Mass Filter RF P/S Error Byte. Description Error Code RF_CT exceeds (V_EXT- 2V) at M_MAX Primary current exceeds 2.0A Not used Power supply in current limited mode. Not Used Not Used Not Used Not Used CEM_ERR Error Byte: Electron Multiplier Error Byte.
Page 193 Error Byte Definitions 3-69 FIL_ERR Error Byte: Filament Error Byte. Description Error Code No filament detected. Unable to set the requested emission current. Vacuum Chamber pressure too high. Not used Not used Not used Not used Single filament operation. RS232_ERR Error Byte: Communications Error Byte Description Not used Parameter conflict...
Page 194 ...
Page 195: Chapter 4. Trouble Shooting
Chapter 4. Trouble Shooting In This Chapter System Problems ................................4-2 Diaphragm Pump Does Not Start ..........................4-2 Turbo Pump Does Not Start............................4-2 Turbo Pump Does Not Reach Full Speed .......................4-2 RGA Fails After Capillary Flow Valve Opened ......................4-2 Loud Noises While Shutting Down.........................4-3 Nothing Operates ...............................4-3 Internal Error Detection in the SRS RGA ........................4-4 24V DC Power Supply ..............................4-5...
Page 196: System Problems
4-2 System Problems System Problems Diaphragm Pump Does Not Start If the light next to the diaphragm pump switch on the front panel is dim, then the microcontroller is trying to run the pump. A relay click can be heard when the controller attempted to start the pump. If the click was not heard, the microcontroller or relay could have failed.
Page 197: Loud Noises While Shutting Down
System Problems 4-3 Loud Noises While Shutting Down It is common to hear loud noises while the turbo pump is coasting to a stop. The pump is a vibration source which is slowly scans the frequency range from 1250 Hz to 0 Hz. Any resonances in the chassis are momentarily excited as the pump passes through the resonant frequency.
Page 198: Internal Error Detection In The Srs Rga
4-4 Internal Error Detection in the SRS RGA Internal Error Detection in the SRS RGA Several firmware-driven checks automatically test the RGA when the instrument is turned on, and continuously monitor the internal workings of the unit. A “Background Filament Protection Mode” is activated, when the filament is turned on to protect the delicate filament (and CDEM) from accidental overpressures.
Page 199: 24V Dc Power Supply
Internal Error Detection in the SRS RGA 4-5 • The query command that can be used to trigger the check (see Error Reporting Commands.) • The prefix of the Error Codes associated to the check. • Is this check performed at power-on? 24V DC Power Supply STATUS Bit affected: Error Byte affected:...
Page 200: Quadrupole Mass Filter Rf P/S
4-6 Internal Error Detection in the SRS RGA checked at any time with the query command: ED?. Several tests are performed during the check: 1. The ADC16 input is grounded and its digital output is measured to make sure it corresponds to less than 15 mV.
Page 201: Filament's Background Protection Mode
Internal Error Detection in the SRS RGA 4-7 Filament’s Background Protection mode STATUS Bit affected: Error Byte affected: FIL_ERR Error Reporting Command: Error Codes prefix: Power-on check?: The filament is by far the most carefully protected component of the RGA. When a electron emission current is requested, the RGA biases the ionizer and activates the filament’s heater until the desired electron current is achieved.
Page 202: Windows Software Error Codes
4-8 Windows Software Error Codes Windows Software Error Codes A unique Error Code has been assigned to each one of the fault conditions that can be internally detected by the RGA Head. The Error Codes are used only by the RGA Windows program to report all internally detected errors.
Page 203: Det5
Windows Software Error Codes 4-9 Troubleshooting: Contact SRS. DET5 Type of Error: Electrometer Error Message: Electrometer Error: DETECT fails to read -5nA input current. Error Cause: The logarithmic output of the picoammeter is not within the levels expected for a -5 nA input current.
Page 204: Em7
4-10 Windows Software Error Codes Type of Error: Electron Multiplier Error Message: Electron Multiplier Error: No Electron Multiplier Option available in this head. Error Cause: A function involving the electron multiplier was invoked in a unit that does not include the CDEM option. Troubleshooting: Do not use any of the CDEM related commands in this unit.
Page 205: Fl7
Windows Software Error Codes 4-11 If a short is detected, remove the probe from the vacuum system , inspect the ionizer and fix any shorts. Note: Use the information in the RGA Maintenance chapter to remove the repeller and/or service the ionizer. If the short is still present after that, remove the RGA Cover Nipple and inspect the rest of the probe for other sources of shorts (i.e.
Page 206: Ps7
4-12 Windows Software Error Codes Troubleshooting: Check the voltage output of the external power supply with a voltmeter. Adjust the voltage to 24 V in adjustable external supplies or replace the power supply altogether if necessary. Contact SRS for units with a built-in power supply (Option Opt02). Type of Error: 24VDC P/S.
Page 207: Rf7
Windows Software Error Codes 4-13 Error Cause: The circuit that drives the primary of the RF Transformer is delivering an unusually large current. Troubleshooting: Check for a short in the quadrupole connections. Type of Error: Quadrupole Mass Filter RF P/S. Error Message: RF P/S Error.
Page 208 4-14 Windows Software Error Codes continuously for a long time. Note: During the warm-up period, RGA Windows users should see that the mass range over which the RGA can be operated reliably increases with time until it goes beyond the user’s requested scan range. No more warnings are posted beyond that point.
Page 209: Chapter 5. Service
Chapter 5. Service The QMS contains no user serviceable parts. The service information in this chapter is intended for the use of Qualified Service Personnel. Read and understand the warnings on the following page. Read the procedures carefully and prepare by having proper tools available. In This Chapter Warnings!...................................5-2 Component Notes ................................5-3...
Page 210: Warnings
5-2 Warnings! Warnings! • The service information in this chapter is for the use of Qualified Service Personnel. To avoid shock, do not perform any procedures in this chapter unless you are qualified to repair electronic and vacuum equipment. • Read and follow all Warnings before servicing the product.
Page 211: Component Notes
Component Notes 5-3 Component Notes Gas Handling Components The QMS system is designed to require low maintenance. A regular maintenance schedule will not extend the life of the components. The pumps are intended to be used until they fail. At such time factory service or kits are available.
Page 212: Fittings And Seals
5-4 Component Notes doubled to 2 mbar. The turbo pump can easily tolerate exhaust pressures up to 5 mbar, so the performance of the diaphragm pump is still acceptable in this example. The pumps contains two components that are most likely to fail: valves and membranes. The valves tend to wear resulting increased backing line pressure (decreased compression ratio).
Page 213: Cdem Handling And Care
Component Notes 5-5 CDEM Handling and Care Continuous Dynode Electron Multipliers (CDEM) have a history of high performance and dependability in mass spectrometry applications. By following the simple recommendations described below the user should achieve a long useful lifetime from these detectors. Handling and mounting •...
Page 214: Storage
5-6 Component Notes liquid nitrogen traps with diffusion pumps (particularly for silicone oil based pumps) , and molecular sieves traps with mechanical roughing pumps whenever possible. If the multiplier becomes contaminated it must be cleaned immediately! (See CDEM Refreshment procedure in this chapter) Storage CDEM’s can be stored indefinitely in a clean dry container such as an air or dry nitrogen-filled “dry box”.
Page 215: Accessing Internal Components
Accessing Internal Components 5-7 Accessing Internal Components The first step to all of the service procedures in the cleaning or replacement sections is opening the QMS chassis. This involves removing the aesthetic covers. Have the QMS turned off, cooled, and vented to atmospheric pressure before beginning.
Page 216: Internal View
5-8 Accessing Internal Components Internal View Map of Internal Components SRS QMS Gas Analyzer...
Page 217: Removing The Rga Ecu
Accessing Internal Components 5-9 Removing the RGA ECU The RGA ECU is supported between the front panel and the probe body. After following the “Opening the Chassis” section above, this procedure can be performed. Reverse the procedure to reattach the ECU. Equipment •...
Page 218 5-10 Accessing Internal Components • Work in a clean dust-free area. Avoid dust, lint and any kind of particulate matter. • Wear talc-free rubber gloves or finger cots. • Use properly degreased tools. • Avoid excessive shock, such as from dropping onto a hard surface (Remember that the CDEM is made out of glass).
Page 219: General Checks
General Checks 5-11 General Checks Leak Testing The seals in the system will have a long life. The metal seals will last indefinitely under normal usage. Only severe force or corrosion will cause them to fail. Elastomeric seals can eventually degrade. The integrity of these seals can be assured using the leak testing mode of the RGA software.
Page 220 5-12 General Checks to install a second gauge in the inlet fitting of the QMS. The two gauges are then compared to see if the internal gauge is correct. Note that the gauge is a thermocouple type gauge and its sensitivity will vary significantly with the composition of the gas being measured.
Page 221: Cleaning
Cleaning 5-13 Cleaning The most general method of cleaning the QMS is to use the vacuum pumps to remove contaminants. The inlet section is cleaned by installing a plug in the Ultra-Torr fitting and opening both valves. This will cause the pumps to continually draw on these surfaces. In severe contamination cases, more aggressive steps may be required.
Page 222: Ionizer Degas
5-14 Cleaning 2. Wrap a heating tape or heating jacket around the vacuum chamber. Make sure the entire probe, including flanges, is evenly covered. 3. Start the pumps and have both pumps operating. The inlet should be plugged with and both valves open.
Page 223: Quadrupole Filter Cleaning
Cleaning 5-15 Warning: The fumes from isopropyl alcohol can be dangerous to health if inhaled and are highly flammable. Work in well ventilated areas and away from flames. Warning: Read and follow all directions and warnings of the ultrasonic cleaner regarding the use of organic solvents for cleaning.
Page 224 5-16 Cleaning • The exact alignment of the rods in the quadrupole is essential to the optimum performance of the RGA. • Do not scratch the surface of the rods. • Do not remove excessive amounts of surface material with the abrasives. •...
Page 225 Cleaning 5-17 Figure 1 Probe Removal for Quadrupole Filter Cleaning 6. Carry the probe to a clean, dust free area immediately. Avoid contamination using handling procedures compatible with high vacuum requirements. 7. Hold the probe in a secure upright position and do a thorough visual inspection of the unit. Check for loose, damaged, misaligned and severely contaminated components.
Page 226 5-18 Cleaning grit down to 12000 until the metal surface has a fine polished appearance. Warning: Do not remove excessive material from the surface of the precision-ground rods. 14. After all metal surfaces have been polished, they must be cleaned to remove all the abrasive compound from their surface.
Page 227 Cleaning 5-19 16. Visually inspect the probe to make sure all the parts are in place and correctly aligned. Use an ohmmeter to make sure the electrodes are electrically isolated from each other and from the body of the flange (ground). 17.
Page 228: Component Replacement
5-20 Component Replacement Component Replacement Ionizer Replacement As the RGA is used, deposits form on the ionizer parts and the sensitivity of the sensor is degraded. Once the sensitivity of the spectrometer is significantly affected by this buildup it is necessary to completely replace the ionizer.
Page 229 Component Replacement 5-21 Figure 2 Probe Removal for Ionizer Replacement 6. Carry the probe to a clean, dust free area immediately. Avoid contamination using handling procedures compatible with high vacuum requirements. 7. Hold the probe in a upright position and do a thorough visual inspection of the unit. Check for loose, damaged, misaligned and contaminated components.
Page 230 5-22 Component Replacement 16. Attach the new repeller to the longer filament rod using a fresh screw. Align the cage and tighten the screw (Correct alignment is best assured when the two small holes on the side of the repeller cage line up with the filament screws.) 17.
Page 231: Filament Replacement
Component Replacement 5-23 Filament Replacement The filament eventually wears out and needs to be replaced. The replacement procedure is simple and can be completed in a few minutes by qualified personnel. The filament is very delicate and should be handled with extreme care. The thoria coating is very delicate and can easily be damaged if the filament is mishandled.
Page 232 5-24 Component Replacement Figure 3 Probe Removal for Filament Replacement 6. Immediately carry the probe to a clean, dust-free area and secure it in an upright position. Avoid contamination using handling procedures compatible with high vacuum requirements. 7. Using the clean, flat-head screwdriver remove the single screw that connects the repeller to the longer filament rod and pull out the cage exposing the filament and the anode grid.
Page 233: Cdem Replacement
Component Replacement 5-25 repeller and anode grid and need to be corrected. Use gentle pressure on the filament wire to bend it back into its correct shape if needed (Note: use a clean cotton swab for this procedure). 16. Attach the repeller to the longer filament rod using a fresh screw. Align the cage and tighten the screw (Correct alignment is best assured when the two small holes on the side of the repeller cage line up with the filament screws.) 17.
Page 234 5-26 Component Replacement 2. Set up in advance a clean dust-free working area where to carry out this procedure. 3. Turn off the RGA and disconnect the ECU from the probe. 4. Wait for the probe to cool down for at least 30 minutes after the emission is turned off. Severe burns can result if the probe is handled too soon.
Page 235 Component Replacement 5-27 contacts. A plate (CDEM Anode ) mounted at the exit of the CDEM collects the secondary electrons. The whole assembly is self aligning. Figure 5 CDEM Replacement 9. Using the clean flat head screwdriver, remove the small screw that fastens the clamp to the HV rod and rotate the entire multiplier about its axis until the clamp’s end points away from the FC Shield.
Page 236: Replacement Parts
5-28 Replacement Parts Replacement Parts Some of the parts discussed in the previous sections are widely available. For users who wish to obtain replacement parts directly, the following manufacturers part numbers will be needed. Nupro and Cajon parts are carried by your local Swagelok distributor. diaphragm pump diaphragm rebuild kit - contact SRS VCR gaskets...
Page 237: Factory Service
Factory Service 5-29 Factory Service The procedures described in this chapter are designed to guide the user through the various steps needed to maintain and/or repair the different components of the QMS instrument. These procedures should only be carried out by qualified personnel who fully understand the instrument. Users who do not feel comfortable or simply do not have the time to go through the different maintenance steps can choose to send the unit back to the factory for out-of-warranty service.
Page 238 ...
Page 239: Appendix A. System Electronics
Appendix A. System Electronics In This Chapter Description of Schematics ............................. A-2 Schematic: MCA_C1..............................A-2 Schematic: MCA_C2..............................A-3 Schematic: MCA_D1..............................A-3 Parts List................................... A-4 SRS QMS Gas Analyzer Technical Reference...
Page 240: Description Of Schematics
A-2 Description of Schematics Description of Schematics Control of the system originates from the microcontroller board mounted to the inside top of the chassis. This board controls the pumps, valves, and pressure gauge. The board consists of two parts: the main board and the display board.
Page 241: Schematic: Mca_C2
Description of Schematics A-3 Schematic: MCA_C2 The relay and two solenoid valves have 24 VDC coils. The relay draws very little power and uses a simple drive circuit. Comparator U3A buffers the value from 5 V logic to 0-24 V. The pull-down resistor assures that the relay will be off during power up.
Page 242: Parts List
A-4 Parts List Parts List Microcontroller Board and Chassis Assembly Parts List REF. SRS part# VALUE DESCRIPTION 5-00011-501 Capacitor, Ceramic Disc, 50V, 10%, SL 5-00011-501 Capacitor, Ceramic Disc, 50V, 10%, SL 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX 5-00225-548 .1U AXIAL Capacitor, Ceramic, 50V,+80/-20% Z5U AX 5-00100-517...
Page 243 Parts List A-5 1-00250-116 2 PIN, WHITE Header, Amp, MTA-156 1-00037-130 16 PIN DIL Connector, Male 7-00748-701 QMS CONTROLLER Printed Circuit Board 4-00088-401 Resistor, Carbon Film, 1/4W, 5% 4-00088-401 Resistor, Carbon Film, 1/4W, 5% 4-00088-401 Resistor, Carbon Film, 1/4W, 5% 4-00088-401 Resistor, Carbon Film, 1/4W, 5% 4-00088-401...
Page 244 A-6 Parts List U 11 3-00546-340 HDSP-4830 Integrated Circuit (Thru-hole Pkg) U 12 3-00546-340 HDSP-4830 Integrated Circuit (Thru-hole Pkg) U 13 3-00103-340 LM3914 Integrated Circuit (Thru-hole Pkg) U 14 3-00103-340 LM3914 Integrated Circuit (Thru-hole Pkg) 6-00010-620 4.000 MHZ Crystal 0-00043-011 4-40 KEP Nut, Kep 0-00084-032...
Page 245 Parts List A-7 1-00316-113 8 PIN, 18AWG/OR Connector, Amp, MTA-156 1-00317-179 2 PIN PLUG Connector Housing, Receptacle 1-00318-179 2 PIN RECPTCL Connector Housing, Receptacle 2-00044-211 1901.1102 Switch, Rocker 7-00731-720 PRS-7 Fabricated Part 7-00766-709 PRS-9 Lexan Overlay 9-00267-917 GENERIC Product Labels Technical Reference...
Page 246: Appendix Brga Circuit Description
Appendix B RGA Circuit Description This chapter describes the electronics circuits located inside the Electronics Control Unit of the RGA. There are no electronic components inside the RGA Probe. The information in this chapter is provided for the use by qualified technical personnel during service and repairs.
Page 247 B-2 Overview of the RGA Schematic name: QMSE_V1........................... B-15 Signal Conditioning............................B-15 Schematic name: QMSE_V2........................... B-17 Electron Multiplier High Voltage Power Supply ..................B-17 Parts Lists..................................B-18 Top Board Components Parts List ……………………………………………………………………………..….. Bottom Board Parts List ……………………………………………………………………………………………….. Vertical Board Parts List B-29 …………………………………………………………………………………………….…...
Page 248: Overview Of The Rga
Overview of the RGA B-3 Overview of the RGA The SRS RGA is a mass spectrometer consisting of a quadrupole probe, and an Electronics Control Unit (ECU) which mounts directly on the probe’s flange. The quadrupole probe is a mass spectrometer sensor consisting of an ion source, a quadrupole mass filter, a Faraday cup and an optional electron multiplier.
Page 249: Circuit Description
B-4 Circuit Description Circuit Description General Description The specifications and features of the many circuits that drive the RGA are determined by characteristics of the quadrupole mass spectrometer such as: • the ionizer settings available to the user, • the characteristics of the quadrupole mass filter, •...
Page 250: Circuit Boards
Circuit Description B-5 multiplier may be used. The electron multiplier needs to be biased with as much as -2500VDC to provide gains as large as 10 Circuit Boards There are two main PCBs inside the ECU package. The top PCB has the CPU, RS232, digital ports, the analog electronics for A/Ds and D/As, and the RF amplitude detection circuit.
Page 251: Description Of Schematics
B-6 Description of Schematics Description of Schematics Schematic name: QMSE_T1 Microprocessor An MC68HC11E9 microcontroller is used to control the system and to communicate with the host computer. This central processing unit (CPU) also has RAM, ROM, EEPROM, UART, octal 8-bit A/D converter, counter timers, and a multiplexed address/data bus to accommodate an external 32Kx8 RAM.
Page 252: The Led Port
Description of Schematics B-7 RS232 data received from host computer. RS232 data transmitted to host computer. SPI_IN Serial peripheral interface data from 16-bit A/D converter. SPI_OUT Serial peripheral interface data to 8 and 18-bit D/A converters. SPI_CLK Serial peripheral interface data clock. -CTS Low to allow host computer to send RS232 data.
Page 253: The Misc Port
B-8 Description of Schematics CAL_2 MSB of current detector calibration attenuator multiplexer. MPX_0 LSB of 16-bit A/D converter's input multiplexer. MPX_1 Middle bit of 16-bit A/D converter's input multiplexer. MPX_2 MSB of 16-bit A/D converter's input multiplexer. EMIT_CTL Filament heater duty cycle control: 0=direct, 1=regulate GRID_SEL Low for low grid potential, high for high grid potential.
Page 254: Rs232 Interface
Description of Schematics B-9 RS232 Interface The microcontroller communicates with a host computer via the RS232 interface. The RS232 interface is configured as a DCE (data communications equipment) at a fixed baud rate of 28.8k, with hardware handshaking via CTS (clear-to-send) and RTS (request-to-send), and uses a PC compatible female DB9 connector.
Page 255: Power-Up Conditioning
B-10 Description of Schematics -IRQ, the CPU sets CS_VETO high (which sets -CS_ADC16 high) and sets R/-C high to allow the data to be read. The -BUSY output will remain low for up to 20µs during a conversion. When -BUSY goes high, the CPU returns CS_VETO low, which again asserts the -CS_ADC16 (this time with R/-C high), and reads the data from the ADC via the SPI.
Page 256: Rf Amplitude Detection
Description of Schematics B-11 RF Amplitude Detection The amplitude of the RF is detected by a full-wave charge pump detector. In order to provide a symmetrical load to the generator, the amplitude on both rods is detected and summed. The charge pump works as follows: as the potential on the rod reaches a peak, the 0.5 pF capacitor (C750 on the PCB which holds the flange socket) is charged to the maximum voltage, Vp + Vdc - Vdiode with current flowing to ground via D303, a Schottky diode.
Page 257: Schematic Name: Qmse_B1
B-12 Description of Schematics The 18-bit DAC output is also used to set the DC potentials applied to the mass filter. RF_SET is multiplied by 4 by the differential amplifier U304A, which uses the bottom PCB for its ground reference. The output of U304A is passed to the bottom PCB via JP301 to control the DC bias sources.
Page 258: Dc Potentials
Description of Schematics B-13 with the correct amplitude and phase into the primary drive inductor, T401, to cancel the charge injected via the FET gates. DC Potentials In addition to the RF, DC potentials of about ±1/12th the RF peak-to-peak value is required for the two rod pairs.
Page 259: Bias Regulators
B-14 Description of Schematics DE_GAS bit) to the voltage seen on the 100Ω emission current shunt resistor, R522. (The current sensed by this resistor is actually composed of three components: the filament emission current, the repeller voltage/100kΩ, and Vref (+5V)/30kΩ. All of these components sum. With a repeller voltage of -60V, the two non-emission sources sum to 0.60+0.166=0.766mA.
Page 260: Schematic Name: Qmse_B3
Description of Schematics B-15 For a high power de-gas, a DPDT relay is used to by-pass the bias regulators, connecting the grid and repeller directly to the un-regulated +250Vdc and -150Vdc supplies. During de-gas, the filament emission current is set to 20mA, which will provide about 8W of power to heat the grid, in addition to 15W of filament heater power.
Page 261 B-16 Description of Schematics lowest current which may be detected. Extreme care is required to achieve low drift and low noise current measurements at these very low current levels. In addition, the instrument needs to measure a wide range of pressures, which requires current measurements over a wide range. The sensitivity of the ionizer and mass filter is about 100µA/Torr, and is nearly constant from 0 to 5x10 Torr, so we expect ion currents from 0 to 5nA.
Page 262: Schematic Name: Qmse_V2
Description of Schematics B-17 Schematic name: QMSE_V2 Electron Multiplier High Voltage Power Supply The electron multiplier option extends the operation of the RGA to much lower pressures. By multiplying the ion current before detection in the I/V converter, the signal to noise ratio is not affected by the bias current noise of the I/V converter.
Page 263: Parts Lists
B-18 Parts Lists Parts Lists Top Board Parts List REF. SRS part# VALUE DESCRIPTION C 100 5-00023-529 Cap, Monolythic Ceramic, 50V, 20%, Z5U C 101 5-00221-529 330P Cap, Monolythic Ceramic, 50V, 20%, Z5U C 102 5-00221-529 330P Cap, Monolythic Ceramic, 50V, 20%, Z5U C 103 5-00285-562 100P...
Page 264 Parts Lists B-19 C 303 5-00239-562 680P Cap., NPO Monolitic Ceramic, 50v, 5% Ra C 304 5-00233-532 Capacitor, Ceramic Disc, 50V, 10% NPO C 305 5-00239-562 680P Cap., NPO Monolitic Ceramic, 50v, 5% Ra C 306 5-00023-529 Cap, Monolythic Ceramic, 50V, 20%, Z5U D 100 3-00010-303 GREEN...
Page 265 B-20 Parts Lists Q 104 3-00021-325 2N3904 Transistor, TO-92 Package Q 105 3-00021-325 2N3904 Transistor, TO-92 Package Q 106 3-00021-325 2N3904 Transistor, TO-92 Package R 100 4-00192-407 49.9K Resistor, Metal Film, 1/8W, 1%, 50PPM R 101 4-00138-407 10.0K Resistor, Metal Film, 1/8W, 1%, 50PPM R 102 4-00887-407 133K...
Page 266 Parts Lists B-21 R 210 4-00192-407 49.9K Resistor, Metal Film, 1/8W, 1%, 50PPM R 211 4-00142-407 100K Resistor, Metal Film, 1/8W, 1%, 50PPM R 212 4-00142-407 100K Resistor, Metal Film, 1/8W, 1%, 50PPM R 213 4-00192-407 49.9K Resistor, Metal Film, 1/8W, 1%, 50PPM R 214 4-00142-407 100K...
Page 267 B-22 Parts Lists R 316 4-00021-401 1.0K Resistor, Carbon Film, 1/4W, 5% R 317 4-00188-407 4.99K Resistor, Metal Film, 1/8W, 1%, 50PPM R 318 4-00188-407 4.99K Resistor, Metal Film, 1/8W, 1%, 50PPM R 319 4-00164-407 20.0K Resistor, Metal Film, 1/8W, 1%, 50PPM R 320 4-00188-407 4.99K...
Page 268: Bottom Board Parts List
Parts Lists B-23 U 307 3-00633-340 MAX528CPP Integrated Circuit (Thru-hole Pkg) 0-00042-010 4-40 HEX Nut, Hex 0-00241-021 4-40X3/16PP Screw, Panhead Phillips 1-00087-131 2 PIN JUMPER Connector, Female Bottom Board Parts List REF. SRS part# VALUE DESCRIPTION C 400 5-00049-566 .001U Cap, Polyester Film 50V 5% -40/+85c Rad C 401 5-00100-517...
Page 269 B-24 Parts Lists C 505 5-00329-526 120U Capacitor, Electrolytic, 35V, 20%, Rad C 506 5-00264-513 .0015U Capacitor, Mylar/Poly, 50V, 5%, Rad C 507 5-00264-513 .0015U Capacitor, Mylar/Poly, 50V, 5%, Rad C 508 5-00330-533 .01U 400V 10% Capacitor, Metallized Polyester C 509 5-00330-533 .01U 400V 10% Capacitor, Metallized Polyester...
Page 270 Parts Lists B-25 D 503 3-00004-301 1N4148 Diode D 504 3-00004-301 1N4148 Diode D 505 3-00203-301 1N5711 Diode D 506 3-00004-301 1N4148 Diode D 611 3-00228-301 MUR160 Diode D 612 3-00228-301 MUR160 Diode D 613 3-00228-301 MUR160 Diode D 614 3-00228-301 MUR160 Diode...
Page 271 B-26 Parts Lists 7-00670-701 RGA BOTTOM Printed Circuit Board Q 400 3-00022-325 2N3906 Transistor, TO-92 Package Q 404 3-00627-325 MPSA92 Transistor, TO-92 Package Q 405 3-00628-325 MPSA42 Transistor, TO-92 Package Q 406 3-00627-325 MPSA92 Transistor, TO-92 Package Q 407 3-00628-325 MPSA42 Transistor, TO-92 Package Q 502...
Page 272 Parts Lists B-27 R 424 4-00405-407 2.49M Resistor, Metal Film, 1/8W, 1%, 50PPM R 425 4-00034-401 Resistor, Carbon Film, 1/4W, 5% R 426 4-00188-407 4.99K Resistor, Metal Film, 1/8W, 1%, 50PPM R 427 4-00074-401 Resistor, Carbon Film, 1/4W, 5% R 428 4-00022-401 1.0M Resistor, Carbon Film, 1/4W, 5%...
Page 273 B-28 Parts Lists R 517 4-00141-407 Resistor, Metal Film, 1/8W, 1%, 50PPM R 518 4-00031-401 Resistor, Carbon Film, 1/4W, 5% R 519 4-00034-401 Resistor, Carbon Film, 1/4W, 5% R 520 4-00192-407 49.9K Resistor, Metal Film, 1/8W, 1%, 50PPM R 521 4-00138-407 10.0K Resistor, Metal Film, 1/8W, 1%, 50PPM...
Page 274 Parts Lists B-29 R 617 4-00800-401 Resistor, Carbon Film, 1/4W, 5% R 618 4-00058-401 220K Resistor, Carbon Film, 1/4W, 5% RL500 3-00196-335 HS-212S-5 Relay T 400 6-00009-610 T1-1-X65 Transformer T 401 6-00197-601 RF PRIMARY Inductor T 500 6-00200-610 RGA FILAMENT Transformer T 601 6-00199-610...
Page 275: Vertical Board Parts List
B-30 Parts Lists Vertical Board Parts List REF. SRS part# VALUE DESCRIPTION C 700 5-00023-529 Cap, Monolythic Ceramic, 50V, 20%, Z5U C 701 5-00023-529 Cap, Monolythic Ceramic, 50V, 20%, Z5U C 750 5-00339-574 .5P 500V SMT SMT, High Voltage Porcelain Cap. C 751 5-00339-574 .5P 500V SMT...
Page 276 Parts Lists B-31 D 810 3-00626-301 MUR1100E Diode D 811 3-00626-301 MUR1100E Diode D 812 3-00004-301 1N4148 Diode J 701 1-00268-120 PUSH-ON RG58 Connector, BNC JP700 1-00266-130 20 PIN DI RA Connector, Male JP750 1-00271-131 4 PIN SI SIDE Connector, Female JP751 1-00271-131 4 PIN SI SIDE...
Page 277 B-32 Parts Lists R 705 4-00193-407 Resistor, Metal Film, 1/8W, 1%, 50PPM R 706 4-00032-401 100K Resistor, Carbon Film, 1/4W, 5% R 707 4-00031-401 Resistor, Carbon Film, 1/4W, 5% R 708 4-00031-401 Resistor, Carbon Film, 1/4W, 5% R 709 4-00032-401 100K Resistor, Carbon Film, 1/4W, 5% R 800...
Page 278 Parts Lists B-33 0-00308-021 4-40X7/8PP Screw, Panhead Phillips 0-00316-003 PLTFM-28 Insulators 0-00317-000 40MM 24V Hardware, Misc. 0-00551-000 40MM FAN GUARD Hardware, Misc. 0-00588-030 #4X5/16" Spacer 0-00589-026 4-40X5/16"PF Screw, Black, All Types 0-00614-021 4-40X1-1/4PP Screw, Panhead Phillips 0-00617-031 4-40X1-3/16 F/F Standoff 0-00627-056 SOUND/AUDIO 1PR Cable, Coax &...
Page 279: Appendix C. Drawings & Schematics
Appendix C. Drawings & Schematics This appendix contains foldout drawings & schematics refered to in previous chapters. System Schematics • QMS Wiring Diagram • Microcontroller PCB Diagram • MCA_C1 • MCA_C2 • MCA_D1 Probe Drawings • Feed-through Flange Connectors • Probe Assembly RGA Schematics •...
Page 280 Declaration of Contamination of Vacuum Equipment The repair and/or service of vacuum equipment or components can only be carried out if a completed declaration has been submitted. SRS reserves the right to refuse acceptance of vacuum equipment submitted for repair or maintenance work where the declaration has been omitted or has not been fully or correctly completed.

SRS Labs QMS 100 Series User Manual

Table of Contents

. Introduction & Operation

Chapter 1 . Introduction & Operation

. Windows Software

Chapter 2. Windows Software

. Measurement Techniques

Table of Contents

. Principles of Operation

. Quadrupole Spectrometer

. Programming the Rga

Chapter 3. Programming the RGA

. Trouble Shooting

Chapter 4. Trouble Shooting

. Service

Chapter 5. Service

Appendix A. System Electronics

Appendix B Rga Circuit Description

Appendix Brga Circuit Description

Appendix C. Drawings & Schematics

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Summary of Contents for SRS Labs QMS 100 Series