- 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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