Experimental Study On Quenching Factor Of Recoiled Nucleus Of Low Energy Threshold HPGe Detector

Dark matter research is one of the hottest topics in the field of physics nowadays. Now we know dark matter is an important compositive part of universe. Dark matter dominates the formation of architecture of universe. The nature of dark matter still remains unknown, however, the Weekly Interactive Massive Particle (WIMP), compared with many other theoretic model particles, is the most possible candidate particle.WIMP can be directly detected with scattered particles by some kind of special target. However, several important parameters, such as incident kinetic energy, recoiled nucleus kinetic energy, reaction section, etc, cannot be accurately measured until the ration of the signal amplitudes by a nucleus recoil and an electron of the same energy is confirmed, which is also the definition of quenching factor. This work makes use of recoiled germanium neaclus collided by neutron to simulate recoiled germanium neaclus collided by dark matter particles, and does research on quenching factor of low energy threshold HPGe detector. The feasibility of experiment of quenching factor on ultra-low energy threshold HPGe detector with recoiled energy below 1keV is also evaluated.Motorola's VME bus adapter MVME5100 is applied as the core functional facility in high speed DAQ system. The operation system running in the platform is VxWorks, which takes charge of programming the hardwares and doing the scheduling among tasks. The accuracy of time response and the speed of data transmission can be guaranteed by the combination of high performance of MVME5100 and VxWorks, which is the best embedded real-time operating system in the world. How to make an appropriate VxWorks image running on the MVME5100 and how to build the whole DAQ system will be expatiated detailedly in this thesis.The experiment is finished in China Insitution of Atomic Energy (CIAE), using the neutron generated by HI-13 tandem accelerator. The self collimated pulsed neutron beam was generated by the ~1H (~7Li, n )~7Be reaction using a hydrogen gas target and pulsed ~7Li beam. A HPGe detector was placed at the center of neutron beam as an active scattering target and several neutron detectors were placed at the different angles to detect the scattering neutrons from germanium. The angles of scattered neutron and the time of flight is used to discriminate the real event sigal from the background signal and noise. Signals from neutron detectors and HPGe detector were converted to digit and recorded by DAQ system to do the offline analysis job.At the end of this thesis, the experimental QF curve of this work with the comparison with other experimental results and the theoretic predictions with TRIM98 simulation code is given. This result indicates that quenching factors above 3keV is measured successfully. Having these data and experiences, we can look forward a better result to the next QF experiment with energy below 1 keV.