Development of Compton Imaging Device for Gamma Rays in MeV Region by The Use of High-pressure Xenon Gas

这项研究的范围分为三类，氙气高压辐射物理、探测器模拟和探测器基础研究。结果表明，当氙气压力从1.0 Mpa增加到3.0 Mpa时，电离产额略有下降。当电场强度小于0.05Td时，闪烁产额迅速下降，高于0.05Td时，产额恒定，约为零电场时的40%。当氙气压力从1.0 Mpa增加到3.0 Mpa时，产额略有增加。当CH4浓度从0增加到2.0%时，掺杂CH4的氙离子由于复合而产生的闪烁产额逐渐消失，而电子群的漂移速度随着电场强度的增加而迅速增大。掺入少量的H_2和CH_4等分子杂质，使高压氙气中的电子温度显著降低。结果表明，这种效应不仅使电子漂移速度增大，而且使电子群在漂移上的扩散减小。利用氙气中的康普顿效应，模拟了一台高压氙气时间投影室(HPXe-TPC)。结果表明，在100公里高度的轨道上，角分辨率约为10度。在扩散伽马射线源的情况下，由于康普顿反冲电子的多次散射，以及在点状伽马射线源的情况下，由于散射伽马射线的多普勒展宽，分辨率主要是模糊的。能量在MeV区的带电粒子的Momenta是可以用TPC测量的，因为α粒子发射角的分布可能是通过重建在正常氙压下用二维TPC测量的α粒子轨迹来确定的。

The scope of this research is divided into three categories, radiation physics on high pressure of xenon, simulation of detectors, and basic studies on the detectors. It is found that ionization yields slightly decrease as increasing the pressure xenon from 1.0MPa to 3.0MPa. On the other hand, scintillation yields rapidly decrease according to the electric field strength less than 0.05 Td and at above that field, show constant yields which are about 40% of ones at zero electric field. However, the yields slightly increase as increasing the pressure of xenon from 1.0MPa to 3.0MPa. The scintillation yields due to recombination in xenon doped with CH^4 disappear as increasing the concentration of CH^4 from 0 to 2.0% and the drift velocity of electron swarms is rapidly increase as increasing the electric field strength. The electron temperature in high pressure xenon dramatically decreases by doping a small amount of molecular impurities such as H_2 and CH_4. It is found the effect make not only the electron drift velocity larger, but the spread of an electron swarm on drift smaller. A high pressure xenon time-projection-chamber(HPXe-TPC) is simulated as an imaging apparatus by using Compton effects in xenon. The results show an angular resolution of about 10 degree at an orbit of 100km altitude. The resolution is mainly blurred by multiple scattering of Compton recoil electrons in the case of a diffused gamma ray source and due to Doppler broadening of scattered gamma rays in the case of a point-like gamma ray source. Momenta of charged particles with an energy in MeV region are made sure to be measurable with the TPC, because a distribution of alpha-particle emission angle is possibly determined by reconstructing alpha-particle tracks measured with a two dimensional TPC under an normal pressure of xenon.