Wall Effect of Internal Gas Proportional Counter in ³⁷Ar Activity Measurement

By analyzing the escape of X-ray and Auger electron generated by 37Ar, wall effect of internal gas proportional counter in 37Ar activity measurement was studied theoretically. Escape of X-ray is the main reason for wall effect of internal gas proportional counter in 37Ar activity measurement. Thus, the exponential extrapolation method of pressure was proved correctly. X-ray and electron transport in proportional counter was simulated by MCNP, and the simulation result accords with theory analytic result. The value of the wall effect was calculated by MCNP, and it is close to experimental result. This work offers theory support for 37Ar detection.