High Pressure BF3 Proportional Counters

Abstract

Construction and filling procedures are described for neutron proportional counters filled to 101‐cm Hg of enriched BF₃+20‐cm Hg of A. Examples are given of the plateau and bias curves obtained for different values of the gas multiplication. Characteristics taken at different times after filling are practically identical, which indicates that no deterioration occurs. The effect of the electron affinity of the BF₃ is discussed, and it is shown how the counter parameters affect the survival probability of the electrons, hence the quality of the pulse size distribution. It has been verified experimentally that negative ions produced by electron attachment are present in the counter gas.