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Oxford Instruments NanoScience Optistat CF Operation Manual

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Oxford Instruments
NanoScience
Optistat CF
Operation Manual
System Manual
/
Issue 2.0
/
September 2020
© Oxford Instruments Nanotechnology Tools Limited, 2016. All rights reserved.

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  • Page 1 Oxford Instruments NanoScience Optistat CF Operation Manual System Manual Issue 2.0 September 2020 © Oxford Instruments Nanotechnology Tools Limited, 2016. All rights reserved.
  • Page 2 P a g e...

  • Page 3: Table Of Contents

    Contents Introduction ............................ 5 Copyright ..........................5 Statement of intended use ..................... 6 Restrictions on use ........................6 Maintenance and adjustment ....................6 Warranty ..........................6 Acknowledgements ......................... 6 Technical support ........................7 Health and safety ..........................8 Disclaimer ..........................8 Disposal and recycling instructions ..................
  • Page 4 3.2.3 Precision height and rotate sample probe..............18 3.2.4 Sample holders ......................18 The cryogen transfer siphon ....................19 MercuryiTC temperature controller ..................19 System wiring ........................19 Sensor calibrations ........................ 20 Gas flow pump and flow controller ..................20 System dewar ........................
  • Page 5 Rubber O-rings ........................39 Troubleshooting ........................39 Optistat CF specifications ......................41 Performance ......................... 41 Electrical power ........................41 Physical..........................41 Technical exclusions and assumptions ................. 41 Appendices ............................ 42 Checking the wiring ....................... 42 Cleaning and general care ..................... 42 P a g e...

  • Page 6: Introduction

    Oxford Instruments be liable for direct or indirect loss or damage of any kind, including loss of profit, revenue, goodwill or anticipated savings. All such warranties are hereby excluded to the fullest extent permitted by law.

  • Page 7: Statement Of Intended Use

    Use of the equipment for purposes other than those intended and expressly stated by Oxford Instruments, as well as incorrect use or operation of the equipment, may relieve Oxford Instruments or its agent of the responsibility for any resultant non-compliance damage or injury. The system must only be used with all external covers fitted.

  • Page 8: Technical Support

    Technical support If you have any questions, please direct all queries through your nearest support facility (see below) with the following details available. Please contact Oxford Instruments first before attempting to service, repair or return components. System type: Optistat CF Serial number: The Sales Order (SO) number and/or other identifiers of your system.

  • Page 9: Health And Safety

    Disclaimer Oxford Instruments assumes no liability for use of any document supplied with the system if any unauthorised changes to the content or format have been made. Oxford Instruments' policy is one of continued improvement. The company reserves the right to alter without notice the specification, design or conditions of supply of any of its products or services.

  • Page 10: Rohs Compliance

    All the materials and components used in the manufacture of the Optistat CF are in compliance without exemption with the EU Directive 2011/65/EU for Restrictions of Hazardous Substances (RoHS). This is based on information provided by Oxford Instruments suppliers and is accurate to the best of our knowledge.

  • Page 11: Low Temperatures

    PROTECTIVE EARTH The cryostat and any other parts of the system fitted with earthing points must always be connected to protective earth during operation. Parts of the system carry high voltages that can cause death or serious injury. Ensure that a local electrical earth (ground) connection is available.

  • Page 12: Weight And Lifting

    Figure 2-1: Example of the pressure relief valve on the Optistat CF. Do not modify or tamper with these safety features in any way. Additionally, ensure that nothing can restrict the movement of any of the pressure relief valves. The relief valves should not vent during normal operation of the system.

  • Page 13: Trip Hazards

    2.5.7 Trip hazards TRIP HAZARDS Poorly routed cables and pumping lines can be trip hazards and have the potential to cause accidents. Such accidents can result in both damage to the system and injury to personnel. Where cables and lines are required, their routings should be considered when planning the installation of the system.

  • Page 14: Risk Assessments

    • Hazard warning signs, barriers or controlled entry systems to ensure that personnel approaching the system are aware of the potential hazards. This precaution is especially important if your system includes a superconducting magnet. • Oxygen monitors should be fitted in the laboratory to warn personnel if the concentration of oxygen in the air falls below safe levels.

  • Page 15: System Description

    System description The Optistat CF is a continuous flow, top-loading static cryostat and can be held at temperatures between 3.4 K and 500 K using a MercuryiTC temperature controller. The sample is mounted on a removeable probe which is cooled via exchange gas during operation. Up to five windows can be fitted to provide optical access to the sample space.

  • Page 16: The Sample Probe

    Figure 3-1 Optistat CF cryostat schematic. The sample probe There are three variants of Optistat CF sample probe; standard, height and rotate, and precision height and rotate. All these Optistat CF sample probes are fitted with a 10-pin seal as standard. The connector is wired to a Harwin pin ring mounted just above the sample holder.

  • Page 17: Standard Sample Probe

    Figure 3-2: Pin configuration for the 10-pin connector. Figure 3-3: Harwin pin ring configuration, as viewed from above. Connector Pin Harwin Ring Pin Wire Function 34 SWG Cu Not Used 34 SWG Cu Not Used 40 SWG Cu Not Used 40 SWG Cu Not Used 40 SWG Cu...

  • Page 18: Height And Rotate Sample Probe

    Figure 3-4: Standard Optistat CF sample probe. 3.2.2 Height and rotate sample probe The Optistat CF height and rotate sample probe is shown in Figure 3-5. The sample rod has fittings to attach a sample holder to its base. When the sample rod is inserted into the Optistat CF, the sample holder then sits between the system’s radial windows.

  • Page 19: Precision Height And Rotate Sample Probe

    3.2.3 Precision height and rotate sample probe The Optistat CF precision height and rotate sample probe is shown in Figure 3-6. The sample rod has fittings to attach a sample holder to its base. When the sample rod is inserted into the Optistat CF, the sample holder then sits between the system’s radial windows.

  • Page 20: The Cryogen Transfer Siphon

    The cryogen transfer siphon The LLT transfer siphon is designed for ultra-low loss performance. The cold exhaust gas from the cryostat flows along the tube, and the enthalpy of the gas is used to shield the flow of liquid from the room temperature surroundings.

  • Page 21: Sensor Calibrations

    Gas flow pump and flow controller The Oxford Instruments GF4 gas flow pump is used to promote the flow through the cryostat. It is an oil-free, twin piston pump with a nominal displacement of 70 litres per minute. The air leak rate is guaranteed to be less than 10 cm .

  • Page 22: System Installation

    Carefully remove the cryostat and all the accessories from the packing case and check the packing list to make sure that you have all the components. Examine the system to make sure that it has not been damaged since it left the factory. If you find any signs of damage, please contact Oxford Instruments immediately.
  • Page 23 Figure 4-1: Standard system operating configuration. A rotary pump may be used as the gas flow pump as part of a lower base temperature operating configuration, as shown in Figure 4-2. In this configuration, temperatures down to 2.3 K can be achieved.

  • Page 24: Evacuating The Outer Vacuum Chamber

    After the evacuation of the OVC, Oxford Instruments recommends fitting a DN16NW blanking flange to the evacuation port to prevent any possible leaks.

  • Page 25: Connecting To The Mercuryitc Temperature Controller

    Connecting to the MercuryiTC temperature controller The MercuryiTC has been configured by Oxford Instruments to suit the ordered system. When you first switch on the MercuryiTC, you will see the instrument home screen, similar to the screen shown in Figure 4-4.
  • Page 26 needle valve (LLT650). After the cable connections have been made, turn on the MercuryiTC. The temperature should read approximately 295 K (room temperature). Cable From (Mercury) Function OVC body Heat exchanger, CQB0090 (Sensor & heater) (Diagnostic 10-pin) sensor & heater Automatic needle CWA0112 Auxiliary socket...

  • Page 27: System Operation

    5 System operation This section describes the operation of the Optistat CF in conjunction with an Oxford Instruments MercuryiTC temperature controller. The cryostat can be operated manually if a temperature controller is not available, although it may be difficult to obtain good temperature control in this configuration.

  • Page 28: Cooling The System

    To begin evacuating the sample space, connect the pumping system to the DN16NW sample space evacuation port. Open the sample space valve by turning the valve cap anti-clockwise by a few turns and then turn the pump on to begin evacuating the sample space. If a high-vacuum pump is being used, it is sufficient to pump once.

  • Page 29: Operation Below 4.2 K

    To start, fully close then fully open the needle valve on the transfer siphon. If a manual transfer siphon (LLT600) is being used, rotate the needle valve fully clockwise to close it, then open it by rotating six full anti-clockwise turns. If an automatic transfer siphon (LLT650) is being used, close the siphon needle valve by setting the gas flow to 0 % on the MercuryiTC.

  • Page 30: Transitioning From 4.2 K Operation

    4.2 K and allowing the heater voltage to increase automatically. The heater voltage will increase to the maximum available level introducing a large amount of heat and boiling off the liquid helium. Oxford Instruments recommends using the following procedure to set a temperature above 4.2 K, after operating at or below 4.2 K: 1.

  • Page 31: Operation Above 4.2 K

    Operation above 4.2 K The MercuryiTC automatically controls the power supplied to the system’s internal heater to maintain the set temperature. The MercuryiTC is a three-term controller, therefore the temperature control is optimised by setting the best values for: • Proportional band (P) •...

  • Page 32: Controlling At A 'Set Temperature

    Figure 5-5: MercuryiTC ‘select file’ screen for loading alternative PID tables. The PID values given in the test results for the system are suitable to give good stability. If you wish to improve the stability further, you may be able to do this by adjusting the three terms slightly. In Manual mode, individual PID values can be changed during operation.

  • Page 33: Operation Above 300 K

    5.5.2 Operation above 300 K To operate at temperatures exceeding 300 K, the OVC should be continuously pumped on using the OVC evacuation port. Pumping on the OVC continuously will help maintain the high vacuum required to operate the system. SYSTEM WINDOWS Before setting an operating temperature above 300 K, ensure that the high temperature sapphire windows have been fitted to the sample space.

  • Page 34: Warming Up The System

    Close the sample space as soon as possible, using a DN25NW clamp and the blank supplied, until the sample probe can be re-inserted. SAMPLE PROBE LOADING Before loading the sample probe, inspect the DN25NW flanges on both the cryostat and sample probe for any damage or debris that could cause an air leak. Also, inspect the O-ring to ensure it is not damaged or contaminated with any debris that could cause an air leak.

  • Page 35: Removing And Replacing The Ovc And Radiation Shield

    Figure 5-6: Special slotted bung fitted in the cryostat siphon arm. SIPHON ARM SLOTTED BUNG It is essential to fit the slotted bung provided with the system as this ensures that the helium circuit within the cryostat is not contaminated, whilst also providing an escape path for any remaining helium within the circuit.

  • Page 36: Changing System Windows

    Before beginning, ensure that the cryostat has been warmed to room temperature by following the procedure described in Section 5.7. Next, vent the OVC and sample space with a dry nitrogen source through their respective valves and ensure that they are at atmospheric pressure. To remove the OVC, remove the four screws which hold the OVC to the cryostat top plate.

  • Page 37: Radiation Shield Windows

    window can then be removed. Select the new window or blank and clean it using a suitable lens cleaner and lens tissue. Inspect the OVC window mount and O-ring to ensure they are not damaged or contaminated with any debris that could cause an air leak. If required, clean the O-ring with isopropanol and apply a light coating of vacuum grease before re-fitting the O-ring.

  • Page 38: Sample Space Windows

    ANNEALED COPPER GASKETS The spare gaskets supplied by Oxford Instruments are thoroughly annealed. If using gaskets supplied by a third party, ensure that they have been thoroughly annealed. Place the gasket in the recess on the sample space window mount and position the new window frame over it.

  • Page 39: 5.10 Operating With Liquid Nitrogen

    Figure 5-9: Changing Optistat CF sample space windows. 5.10 Operating with liquid nitrogen The Optistat CF can be operated with liquid nitrogen instead of liquid helium. The basic operating procedure is the same, but there are a few differences: • Ensure that the flow gauge calibrated for air is used on the VC-U.

  • Page 40: Service And Maintenance

    This section contains basic and essential maintenance information. Rubber O-rings Oxford Instruments recommends replacing the cryostat’s O-rings on a two-year cycle. Whenever a part of the cryostat is removed or if there is a suspected leak on the system, check the relevant O- rings.
  • Page 41 Issue Possible cause Recommendation High base Transfer siphon seal Check the transfer siphon nut is tight enough. temperature Check the transfer siphon is the correct length. Check the PTFE seal has not been damaged. Sensor fault Check sensor resistance at base temperature and compare with the supplied sensor calibration data.
  • Page 42 7 Optistat CF specifications Performance Performance Specification Temperature control range 3.4 K - 300 K * Temperature control stability ± 0.1 K Helium consumption during system cooldown 1.5 L Helium consumption at 4.2 K < 0.55 L / Hour Sample change time 5 minutes System cooldown time 25 minutes...
  • Page 43 8 Appendices Checking the wiring A resistance meter can be used to check the wiring on the cryostat. You should expect to measure the following values. Pins Approx. resistance (at 300K) A - B 15 – 25 Ω C - D 30 –...

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