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LUDLUM 42-49B Manual

Neutron detector
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LUDLUM MODEL 42-49 & 42-49B
NEUTRON DETECTOR
October 2021

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Summary of Contents for LUDLUM 42-49B

  • Page 1 LUDLUM MODEL 42-49 & 42-49B NEUTRON DETECTOR October 2021...
  • Page 2 LUDLUM MODEL 42-49 & 42-49B NEUTRON DETECTOR October 2021...
  • Page 3 RETURN OF GOODS TO MANUFACTURER If equipment needs to be returned to Ludlum Measurements, Inc. for repair or calibration, please send to the address below. All shipments should include documentation containing return shipping address, customer name, telephone number, description of service requested, and all other necessary information.

  • Page 4: Table Of Contents

    Model 42-49 & 42-49B Neutron Detector Technical Manual Table of Contents Introduction Unpacking and Repacking Connecting to an Instrument Specifications Safety Considerations Environmental Conditions for Normal Use Cleaning Instructions and Precautions Calibration Calibration Operating Voltage Plateau Gamma Rejection Check Conversion Chart...

  • Page 5: Introduction

    He→ H + 0.764 MeV. The Ludlum Model 42-49 and 42-49B utilize this reaction in the form of helium-3( He), which fills the gas proportional tube of the detector The Model 42-49 and 42-49B are designed to be used with portable counting instruments and has a top bracket that allows for convenient mounting of a portable instrument.
  • Page 6 Shown above are the two different boron moderators attached to the detector, which fit into a rem ball. The one on the left is a 42-49, and the one on the right is a 42-49B. Ludlum Measurements, Inc.

  • Page 7: Unpacking And Repacking

    Every returned instrument must be accompanied by an Instrument Return Form, which can be downloaded from the Ludlum website at www.ludlums.com. Find the form by clicking on the “Support” tab and selecting “Repair and Calibration” from the drop-down menu.

  • Page 8: Specifications

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 3 Section Specifications 2 atm ³He tube LND 25185 or equivalent Detector: 19.6 cm (7.7 in.) diameter high density polyethylene sphere Moderator: typically used with portable counting Compatible Instruments: instruments (capable of achieving -2 mV input sensitivity)

  • Page 9: Safety Considerations

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 4 Section Safety Considerations Environmental Conditions for Normal Use Indoor or outdoor use (in a dry environment) No maximum altitude Temperature range of -20 to 50 °C (-4 to 122 °F); may be certified for operation at -40 to 65.6 °C (-40 to 150 °F)

  • Page 10: Calibration

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 5 Section Calibration Calibration To calibrate the detector, the following items are needed:  Counting instrument: Ludlum Model 2200 Scaler/Ratemeter  AmBe neutron source or equivalent  Cs gamma source for gamma rejection check Operating Voltage Plateau Connect the Model 42-49 to a Model 2200.

  • Page 11: Gamma Rejection Check

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 5 For example, an assumed operating voltage is 1100 volts, based upon the flattest part of the plateau. The count rate at that voltage is 2380 counts per minute (cpm), and the neutron field dose-equivalent rate is 20 rem/hr.

  • Page 12: Conversion Chart

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 5 Conversion Chart Expose the detector to an AmBe neutron source at a dose- equivalent rate of 400 mrem/hr. Take a one-minute count and record the value, including the range/scale setting of counting instrument.

  • Page 13: Parts List

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 6 Section Parts List Reference Description Part Number Model 42-49 UNIT Completely Assembled Neutron Detector Model 42-49 Neutron Detector 47-4057 2 EA. SCREW-6-32 X 3/8 BRASS KNURL 17-8659 Model 42-49 SPHERE ASSY 47-4058 4 EA.

  • Page 14: Model 42-49 Neutron Detector

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 6 Reference Description Part Number Model 42-49B Conversion Kit Model 42-49 Conversion Kit 4014-620-01 1 EA. Borated Silicone Shell 5/32 HL 7014-609 1 EA. Borated Silicone Shell, 3/4 HL 7014-610 1 EA.

  • Page 15: Drawings And Diagrams

    Model 42-49 & 42-49B Neutron Detector Technical Manual Section 7 Section Drawings and Diagrams Model 42-49 Overall, Drawing 14 x 584 Model 42-49 Probe Assembly, Drawing 14 x 587 Model 42-49B Probe Assembly, Drawing 14 x 620 Ludlum Measurements, Inc. Page 7-1 October 2021...

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42-49

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