Modeling and signal analysis of semiconducting B(5)C neutron detectors

Neutron detectors are needed for a myriad of applications ranging from military uses to power generation monitors to medical radiation therapy. Recently, a class of semiconducting boron carbide (B5C)/silicon heterojunction diodes were demonstrated to detect thermal neutrons.[1] The B5C-based devices have advantageous features of requiring low operating voltage, low power, are robust and extremely thin while maintaining detection efficiency. A simple model was developed for the analysis of the neutron capture output spectrum from the detectors, which allowed the comparison of several differing styles of planar geometry detectors. The model was also utilized to obtain the functional dependence of the device efficiencies, capture product spectral features, and the capture product energy deposition on capture layer thickness. An all-B5C device construction was determined by the model to be the most efficient form of a B5C-based detector, which reaches nearly 100% detection efficiency with a low probability of false positives. This model showed agreement with output from a full-physics simulation package, GEANT4, and experimental neutron detection spectra from a B5C/Si device. The signals generated in a B5C/Si heterojunction diode during neutron and alpha particle detection experiments were analyzed through fitting of the output current pulses and through capture output spectra. The output current pulse analysis confirmed charge generation and collection from both materials in the diode and demonstrated the suitability of the B5C material for use in an all-semiconducting B5C neutron detector. The experimental output spectra were analyzed and determined to be lower in detected capture product energy than expected, but retained the spectral features that allowed analysis of the detection results. The development of the model and the results from the particle detection experiments show great promise for the future development of B5C neutron detectors. [1]B. W. Robertson, S. Adenwalla, A. Harken, P. Welsch, J. I. Brand, P. A. Dowben, and J. P. Claassen, A class of boron-rich solid-state neutron detectors, Applied Physics Letters, vol. 80, pp. 3644-46, 2002