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3-Helium detectors
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  • The advantage over 10B is that the 3He neutron cross section is almost 40% higher. It is also a better proportional gas than BF3.
  • The gas itself though is expensive due to its natural abundance being low.
  • Helium is a poor at stopping neutrons and Ar or Kr are added to increase the stopping power.
  • The Q value is relatively small (0.764 MeV).
  • Once again wall effects need to be considered and while BF3 gives best results at pressures below one atmosphere much higher pressures of up to 40 atmospheres are used with 3He.
  • The relatively low Q value makes the 3He detector valuable in detecting neutrons which have a kinetic energy which is significant compared to 764 keV from 10 keV upwards.

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