We report the first results of light Weakly Interacting Massive Particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with an exposure of 102.8 kg-days. At an analysis threshold of 160 eVee, improved limits of 8 $times 10^{-42}$ cm$^{2}$ and 3 $times 10^{-36}$ cm$^{2}$ at 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross-sections, respectively, at a WIMP mass (m$_{chi}$) of 5 GeV/$c^2$ are achieved. The lower reach of m$_{chi}$ is extended to 2 GeV/$c^2$.

This paper develops a method of Vector Projection (VP), which is based on investigations and a mathematical abstraction of many methods of Pulse Shape Discrimination (PSD) used in particle identification. VP is a universal method and its optimum parameter selection is discussed in detail. Optimized PSD effect by using VP with appropriate parameters is verified utilizing the data obtained from the FADC measurement system.