2013年和2014年初国际上多个实验组发表了新的轻质量暗物质探测结果，引起高度关注。高纯锗探测器凭借极低的能量阈值可以直接探测轻质量暗物质，研究方案具有优势。通过模拟和实验研究相结合的方式，对于深入理解高纯锗暗物质实验本底种类和来源，发展更优化的高纯锗探测器本底甄别方法，大大提高暗物质探测灵敏度具有重要意义。 本项研究以清华大学暗物质实验组获取的低能量阈高纯锗探测器的实验数据为基础，结合模拟研究，并开展新的低通量中子实验，对12keV以下能量范围的高纯锗探测器中子和伽马本底进行研究，建立实验和模拟研究方法，确定包括探测器自身本底、结构材料本底及外部屏蔽材料等贡献的中子和伽马本底详细来源及其对能谱的贡献，并尝试发展针对高纯锗探测器的中子伽马信号甄别方法，有效提升高纯锗暗物质实验灵敏度，并且可以在更高灵敏度情况下开展年度调制效应研究，预期得到国际一流暗物质实验物理结果。

The low mass dark matter particles have been the new hot topics for dark matter direct detection experiment. There are several new physical results being published by different collaborations in 2013 and the beginning of 2014. Due to its good performances such as ultra-low energy threshold and high internal radioactive purity, high purity germanium detector has been a good choice for low mass dark matter search. The energy threshold of about 400eV has achieved by germanium detector makes it possible for scientists to scan the ultra-low energy spectrum of germanium detector where exists some low energy characteristic X-ray lines. Combining experimental and simulated methods, one can go further to understand the kinds,sources of the germanium detector served as dark matter detector and develop the optimal signal discrimination methods. This will be very helpful to improve the sensitivity of dark matter experiment. This project will study further the gamma and neutron background contribution of the point-contact germaniumd detector below 12 keV used by CDEX-1 group for light mass dark matter search. We will try to set up the experimental and simulated methods to define the background kinds and sources including gamma and neutron background contribution. At the same time, the new data analysis method will be developed to discriminate the different pulses near energy threshold region in order to lower further the energy threshold of our germanium detector. This will be helpful for the improvement of the sensitivity of the dark matter search experiment and the studies of annaul modulation effect of fark matter.