Polycrystalline BN and LiF Based Semiconductor Alpha Particle and Neutron Detectors

Composite, polycrystalline, semiconductor, hexagonal BN alone or mixed with B₄C or BMg₂ and cubic LiF were embedded in an insulating matrix which acts as a binder and tested as alpha particle and neutron detectors. The boron containing semiconductors have the natural abundance of ¹⁰B which is ~20%. In the case of LiF is the natural content of ⁶Li only 7.4%. The matrix binder further reduces the contents of ¹⁰B and ⁶Li to about one half. For alpha particles from a ²⁴¹Am alpha source of ~10⁵ cm^-2s^-1, 5.5 MeV gives the detector a wide peak in the spectrum. In the case of the thermal neutron detection, if the sources are very weak of only ~100 cm^-2sec^-1, the neutron counting is possible by subtracting the total signal from the noise. The resulting a signal to noise (S/N) ratio is of only ~2 and one needs a larger collection time of hours for a larger number of pulses to be collected. With a source of a higher neutron flux such as a nuclear reactor, which can offer flux of 10⁷ cm^-2s^-1, is the S/N ratio of ~33. LiF composites with only 3.7% of ⁶Li could also detect very weak neutron sources, but the very low amount of ⁶Li produced a S/N ratio of ~1.4. Compared with widely used ³He detectors is the thermal neutron detection efficiency of the BN and LiF based detectors significantly higher for the same sizes of detectors. Even at a pressure of 3 atmospheres of an inch in diameter ³He detector is the detection efficiency 64% compared with ~72% of a 1 mm thick composite BN detector. Results of enriched ⁶LiF and mixed BN composite detector measurements with stronger neutron sources will be also reported.