Gas Proportional Counter Tube Measurement <sup> 37 </ Sup> Of Ar Activity Detection Efficiency

For on-site inspections(OSI) under the CTBTO,measurement of the noble gas Argon-37 was considered an important technique,as ³⁷Ar is a definitive and unambiguous indicator of a nuclear underground explosion.For the purpose of on-site inspections in the framework of the Comprehensive Nuclear Test-Ban- Treaty,the Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics,Mianyang,China,has developed the Movable ³⁷Ar Rapid Detection System(MARDS).The detection efficiency of the internal gas proportional counter which is engaged to measure the activity of ³⁷Ar in MARDS is extraordinary important,for it is one of the most significant technology features of MARDS.Furthermore, whether ³⁷Ar verification technology is trusty partially depends on the reliability of detection efficiency.Threshold effect,end effect,and wall effect of a type of proportional counter in detecting ³H and ³⁷Ar activity are studied by experiments in this paper.The detection efficiency of a type of proportional counter in detecting ³H and ³⁷Ar activity,which is determined by experiments,is also presented in this paper.We find that the difference between wall effect of ³H and ³⁷Ar is remarkable.Therefore,the detection efficiency of ³H and ³⁷Ar is different.By theory analysis and MCNP5 simulation,we get the theoretical values of wall effect of ³H and ³⁷Ar,which are extremely close to experimental results.It shows that the experimental results that indicate the differences between the detection efficiency of ³H and ³⁷Ar are believable. Intercomparisons of ³H and ³⁷Ar activity measurements are carried out in this work. Comparison results indicate that the measurement and results of ³⁷Ar and ³H activity are dependable in this work.All the results we get in this work prove that the detection efficiency of a type of proportional counter used in MARDS for ³⁷Ar activity measurement is of great reliability.So this work provides a trusty technology feature for MARDS.Moreover,it offers support for the ³⁷Ar verification technology.