Model 42-31H

Neutron Detector

Part Number: 47-3583

The Ludlum Model 42-31H Neutron Detector is designed to detect thermal and fast neutrons (0.025 eV to approximately 12 MeV). Neutrons are detected indirectly through nuclear reactions which result in energetically charged particles, such as alpha particles, which are often found associated with intense fields of gamma rays. Therefore, it is important to choose a method of neutron detection with the ability to discriminate against gamma rays in the detection and measurement processes.

The Model 42-31H is intended for use with portable counting instruments, and is fitted with a top bracket for convenient mounting. The instrument consists of a cadmium-loaded polyethylene sphere surrounding the ³He detector. A study has demonstrated that the 9-inch cadmium-loaded sphere has a response similar to that of a 10-inch diameter rem-responding sphere.

• Specifications
• Suggested Instruments
• Documents

• Specifications
• Suggested Instruments
• Documents

Specifications

Indicated Use	Neutron detection; Area monitoring
Detector Type	2 atm 3He tube LND 25185 or equivalent
Moderator	22.9 cm (9 in.) diameter cadmium-loaded polyethylene sphere
Detection Range	Thermal to approximately 12 MeV
Energy Response	Thermal to 12 MeV; approximately follows the radiation protection guide curve for neutron dose
Sensitivity (241AmBe)	10,000 cpm per mSv/h (100 cpm per mrem/hr )
Gamma Rejection (137Cs)	10 cpm or less up to 0.1 Sv/h (10 R/hr)
Operating Voltage	1200 V (typical)
Input Sensitivity	-2 mV
Connector	Series "C" (others available)
Construction	Brackets: Drawn-and-cast aluminum with a beige powder-coat Ball: Polyethylene
Size (H x W x D)	26 x 22.9 x 22.9 cm (10.3 x 9 x 9 in.)  including brackets
Weight	6.6 kg (14.5 lb)

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Suggested Instruments

• Typically used with portable counting instruments capable of achieving -2 mV input sensitivity

 

Model	Description	Part Number
Model 12	Analog Survey Meter	48-1609

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Documents

• Data Sheet
• Manual
• CE Certificate
• Model 42-31 Removal of BF-3 Tube

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