one have to improve the sampling device and test conditions.The added sealing rubber ring in the improved sampler could not only act as a sealing but also locate casing pipe;the inprovement of test conditions include prolonging the sampling time and increasing well-hole depth from 35 cm to 155 cm. The improved device was used to test Wen-31 oil pool
the counting rate was more than 80 pulse/min. The cyclic anomaly was clearly reflected in plan