Abstract
Count-rate capability, spatial resolution, and photon discrimination of position-sensitive, proportional neutron counters were improved by using a detector gas mixture of 65% 3He and 35% CF4. These improvements, relative to previously used 3HeXe CO2 mixtures, were due to the larger electron drift velocity, greater stopping power for the protons and tritons of the 3He(n, p) reaction, and smaller photon cross section of the HeCF4 mixtures.
| Original language | English |
|---|---|
| Pages (from-to) | 395-401 |
| Number of pages | 7 |
| Journal | Nuclear Instruments and Methods In Physics Research |
| Volume | 201 |
| Issue number | 2-3 |
| DOIs | |
| State | Published - Oct 15 1982 |
Funding
Drift velocity measurements on gas mixtures containing CF 4 \[1,2\]m otivated us to evaluate the characteristics of 3He-CF4 mixtures and to show that this mixture improves the neutron detection and imaging with proportional counters relative to previously used gas mixtures \[3,4\]. Whenever the 3He(n, p) reaction is used in proportional counters to detect and image thermal neutrons, the 3He gas is mixed with polyatomic gas additives to (1) quench the ultraviolet or visible light emitted from collisions between drifting electrons and gas molecules and, hence, prevent breakdown in the counter when operating at high gas multiplication \[5\];( 2) increase the drift velocity and, hence, shorten the pulse rise time of the output signals and increase the count-rate capability \[6\]; and (3) increase the stopping power for the protons and tritons from the 3He(n,p) reaction and, hence, improve the spatial resolution and mitigate the wall effects \[7\]. Furthermore, to prevent deterioration of the counter properties, the additive gas must be stable under discharge conditions and in high temperature and gamma radiation environments. Also, to preserve proportionality between converted energy and avalanche charge, the electron attachment cross section of the additive gas must be small. Finally, the photon cross section of the additive gas should be as small as possible to preserve the inherently good photon discrimination * Research sponsored by the Office of Reactor Research and Technology and the Office of Health and Environmental Research, U.S. Department of Energy, under contract W-7405-eng-26 with Union Carbide Corporation. ** Also, Department of Physics, the University of Tennessee, Knoxville, TN 37916, U.S.A.