Cylindrical Detector and Preamplifier Design for Detecting Neutrons

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Title: Cylindrical Detector and Preamplifier Design for Detecting Neutrons
Author: Xia, Zhenghua
Abstract: Tissue equivalent proportional counters are frequently used to measure dose and dose equivalent in mixed radiation fields that include neutrons ; however , detectors simulating sites 1 ?m in diameter underestimate the quality factor , Q , for low energy neutrons because the recoil protons do not cross the detectors . Proportional counters simulating different site -sizes can be used to get a better neutron dose equivalent measurement since the range and stopping power of protons generated by neutrons in the tissue -equivalent walls depend on the energy of the primary neutrons . The differences in the spectra measured by different size detectors will provide additional information on the incident neutron energy . Monte Carlo N -particle extended (MCNPX ) code was used to simulate neutron transportation in proportional counters of different simulated tissue diameter . These Monte Carlo results were tested using two solid walled tissue equivalent proportional counters , 2mm and 10mm in diameter , simulating tissue volumes 0 .1 ?m and 0 .5 ?m in diameter , housed in a single vacuum chamber . Both detectors are built with 3mm thick tissue equivalent plastic (A -150 ) walls and propane gas inside for dose measurement . Using these two detectors , the spectra were compared to determine the underestimation of y for large detector , and thereby obtain more information of the incident neutron particles . Based on the MCNPX simulation and experimental results , we can see that the smaller detector produces a larger average lineal energy than the larger detector , which means the larger detector (0 .5 ?m diameter tissue equivalent size ) underestimates the Q value for the low energy neutron , therefore underestimates the effective dose . These results confirm the results of the typical analysis of lineal energy as a function of site size .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2008 -12 -158
Date: 2010-01-14

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Cylindrical Detector and Preamplifier Design for Detecting Neutrons. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2008 -12 -158 .

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