  The CDEX (China Dark matter Experiment) now deploys ~10 kg pPCGe (p-type
Point Contact Germanium) detectors in CJPL (China Jinping Underground
Laboratory). It aims to detect rare events such as dark matter and 0vbb
(neutrinoless double beta decay). The discrimination of bulk and very bulk
events are essential for improvements of the analysis threshold of dark matter.
Very bulk events are generated near the p+ point surface of pPCGe, which are
usually from radioactive materials of electronic devices. Due to different
locations of charge collection, bulk and very bulk events have different pulse
shape. This paper will present two linear PSD (Pulse Shape Discrimination)
methods: CCM (Charge Comparison Method) and Fisher's LDA (Linear Discriminant
Analysis), to realize the discrimination of bulk and very bulk events. The
results show that FOMs (Figure of Merit) are 1.38 $\pm$ 0.33 and 1.62 $\pm$
0.18 by CCM and Fisher's LDA respectively.
