Development of High Resolution Homogeneous Calorimeter Using Liquid Xenon

在本科研项目中，我们研制了高分辨率液态氙均质量热计。这种新型量热计使用液态氙作为活动介质，在伽马射线和电子的入射下发出紫外线闪烁灯。液体氙周围的许多光电倍增管（pmt）测量这些闪烁光。该量热计在液态氙体积中不含电极等被动物质，能充分观察到所有的能量沉积。我们主要专注于实现大容量（1000升或3吨订单）探测器所需的各种技术的开发。液态氙作为探测器介质，保证了探测器的均匀性，但如果存在杂质污染，则会吸收闪烁光，从而影响如此大体积器件的性能。我们成功地开发了一种新的、高效的净化方法，利用低温离心液体泵，通过分子筛循环液体来快速去除杂质。我们还开发了氙转移、氙压力/温度控制、安全预防等方法和技术。这些是大体积液态氙探测器实际应用所必需的。我们用π^0衰变检验了液态氙探测器的性能。在这次测试中，我们收集了pmt的波形数据，证明了我们可以区分入射伽马射线和α粒子。我们还成功地开发了一种具有光电阴极和基极电路的新型pmt，即使在低温下也能维持非常高的背景速率。开发了计算机代码来模拟探测器的响应，并证明与观测数据非常吻合。在液态氙中对雪崩光电二极管（APD）进行了操作和测试。APD结构紧凑，量子效率高。这一试验的成功开辟了广泛的未来应用，如监测吸收长度。少

In this scientific research project we have developed high resolution homogeneous calorimeter using liquid xenon.This new type of calorimeter uses liquid xenon as the active medium that emits UV scintillation lights upon incidence of gamma rays and electrons. A number of photomultiplier tubes (PMTs) surrounding the liquid xenon measure these scintillation lights. The calorimeter does not contain any passive material like electrodes in the liquid xenon volume, thus can fully observe all the energy deposits.We mostly concentrated on developments of various technologies necessary to realize a large volume (an order of 1,000 liters or 3 tons) detector.Liquid xenon as the detector medium is guaranteed to be perfectly uniform, however, some impurity contamination, if it exists, absorbs the scintillation light and could deteriorate the performance of such a large volume device. We successfully developed a new, efficient purification method to remove impurities very quickly by circulating liqu … More id xenon through molecular sieves using a cryogenic centrifugal liquid pump. We also developed methods and techniques for xenon transfer, xenon pressure/temperature control, safety precaution, etc. These are necessary for practical application of a large volume liquid xenon detector.We examined the performance of a liquid xenon detector by using π^0 decays. In this test we collected waveform data of PMTs and proved that we can distinguish incident gamma-rays from alpha particles. We also succeeded in developing a new type of PMTs with photocathode and base circuit that can sustain very high background rates even at low temperatures. Computer codes were developed to simulate the detector response and were shown to agree very well with the observed data.An avalanche photodiode (APD) was operated and tested in liquid xenon. The APD is very compact and has a very high quantum efficiency. The success of this test opened up extensive future applications such as monitoring of absorption length. Less