Andrew C. Stephan

Neutron detector based on lithiated sol-gel glass

Abstract A neutron detector technology is demonstrated based on 6 Li/ 10 B doped sol–gel glass. The detector is a sol–gel glass film coated silicon surface barrier detector (SBD). The ionized charged particles from ( n , α) reactions in the sol–gel film enter the SBD and are counted. Data showing that gamma-ray pulse amplitudes interfere with identifying charged particles that exit the film layer with energies below the gamma-ray energy is presented. Experiments were performed showing the effect of 137 Cs and 60 Co gamma rays on the SBD detector. The reaction product energies of the triton and alpha particles from 6 Li are significantly greater than the energies of the Compton electrons from high-energy gamma rays, allowing the measurement of neutrons in a high gamma background. The sol–gel radiation detection technology may be applicable to the characterization of transuranic waste, spent nuclear fuel and to the monitoring of stored plutonium.

Spectra of fast neutrons using a lithiated glass film on silicon

Abstract Experimental results of a neutron detector manufactured by coating a silicon charged particle detector with a film of lithiated glass are presented. The silicon surface barrier detector (SBD) responds to the 6 Li(n, alpha)triton reaction products generated in the thin film of lithiated glass entering the SBD. Neutron spectral information is present in the pulse height spectrum. An energy response is seen that clearly shows that neutrons from a Pu–Be source and from a deuterium–tritium (D–T) pulsed neutron generator can be differentiated and counted above a gamma background. The significant result is that the fissile content within a container can be measured using a pulsed D–T neutron generator using the neutrons that are counted in the interval between the pulses.

Development of a High-Efficiency, Glass Shell-Based, 3 He-Filled Neutron Detector

We have developed a new type of neutron sensor based on small, gas-filled, glass shells with external electrodes. The detector functions as a small (<1-cm-diameter) 3He ion chamber for applied bias voltages from roughly 50 V to 900 V. We have demonstrated that the detectors function with internal gas pressures from 6 to 10 atm. Charge transport times across the detector volume are a few microseconds. The detectors have very low gamma-ray sensitivity due to their small size as compared to the path-length of energetic electrons generated by gamma-ray interactions. Multiple shell detectors are intended to be deployed within a moderator block to form a single detector system. The resulting detector-moderator configuration approaches the efficiency of a homogeneous system. This paper presents device characterizations and performance data.