Page 821 - Radiation Safety

Neutron Detector

3 He vs BF Detectors
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❑ Boron has a lower neutron cross section (3840 barns) compared

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with He (5400 barns), therefore boron counters are less sensitive
than their helium counterparts.

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❑ The energy released per reaction is higher in B than He which
enables BF counters to discriminate against gamma pulses.
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❑ BF counters function at much higher voltages than He counters
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(1 - 4 kV). For voltages above 2 kV it is recommended that a guard

ring be used on the anode insulator. Guard rings prevent

electrical leakage across the insulator and reduce noise from the

counter signal.