Material Screening with HPGe Counting Station for PandaX Experiment
  A gamma counting station based on high-purity germanium (HPGe) detector was set up for the material screening of the PandaX dark matter experiments in the China Jinping Underground Laboratory. Low background gamma rate of 2.6 counts/min within the energy range of 20 to 2700 keV is achieved due to the well-designed passive shield. The sentivities of the HPGe detetector reach mBq/kg level for isotopes like K, U, Th, and even better for Co and Cs, resulted from the low-background rate and the high relative detection efficiency of 175%. The structure and performance of the counting station are described in this article. Detailed counting results for the radioactivity in materials used by the PandaX dark-matter experiment are presented. The upgrading plan of the counting station is also discussed. 
Xuming Wang, Xun Chen, Changbo Fu, Xiangdong Ji, Xiang Liu, Yajun Mao,   Hongwei Wang, Siguang Wang, Pengwei Xie, Tao Zhang
physics.ins-det hep-ex