Development of a High Sensitivity PMT assembly for the balloon-borne Soft Gamma-ray Polarimeter

偏振伽马射线观测器光版本（PoGOLite）是一种新的气球实验，旨在测量20-100 keV能量范围内的天文物体（如恒星、黑洞和活动星系核）的偏振。它正在建造中，预计将于2009年首次飞行。本研究的最初目的是开发一种高灵敏度光传感器（PMT-ASSY），其可用于气球（即，在2004年至2006年期间，为PoGOLite飞行传感器建造了150多个单元。现在，我们很高兴地报告，我们已经完成了我们的研究，与一些fuits比我们预期的。我们的成果总结如下：（1）生产了150多个光电倍增管组件的首次飞行的PoGOLite。（2）建造由7个phoswich单元组成的原型偏振计，并在KEK光子工厂的同步辐射设施进行详细的性能测试。（3）开发“Monte-calro模拟器”，该模拟器能够在各种背景事件（例如宇宙X射线背景（CXB）、带电粒子和大气伽马射线）下真实地模拟PoGOLite灵敏度。（4）在大坂大学RCNP回旋加速器设施中进行的400 MeV质子束下带电粒子响应的详细测试（5）作为PHENEX的监视器计数器的1单元PMT组件的调试通过以上详细的性能测试，我们证实了该探测器系统的性能是可靠的（PMT ASSY，和相关的电子，高电压等）在这项研究中开发的工作相当不错，在气球轨道预期的严重条件。特别是，我们表明，PMT-ASSY监测信号/背景事件的计数率为16小时的PHENEX实验。引人注目的是，当蟹状星云/脉冲星被锁定在探测器视场中时，监视器计数器的计数率显著增加。

The Polarized Gamma-ray Observer-Light Version (PoGOLite) is a new balloon-borne experiment designed to measure polarization from astronomical objects, such as pulsars, black holes, and Active Galactic Nuclei, in the 20-100 keV energy range. It is under construction for the first flight expected in 2009. The original purpose for this research was to develop a high sensitivity light sensor (PMT-ASSY) which can be used in the balloon (i.e., low-pressure) environment, and to construct more than 150 units of them for the flight PoGOLite sensors between 2004 and 2006. Now we are happy to report that we have completed our research, with a number of fuits than what we had anticipated. Our results are summarized as follows:(1)Production of more than 150 PMT assembly for the first flight of the PoGOLite.(2)Construction of prototype polarimeter which consisted of 7 phoswich units, and detailed performance test at the synchrotron radiation facility in the KEK photon factory.(3)Development of a "Monte-calro simulator" which enables realistic simulations of PoGOLite sensitivity, under various background events such as cosmic X-ray background (CXB), charged particles, and atmospheric gamma-ray.(4)Detailed test of charged particle response under 400 MeV proton beam at the cyclotron facility in the RCNP, Osaka University(5)Balloon-fight of 1 unit PMT-Assembly as a monitor counter of the PHENEX (Polarimeter for High ENErgy X-rays) experiment in 2006.Through above detailed performance tests, we confirmed that the detector system (PMT-ASSY, and associated electronics, high voltage etc) developed in this research works pretty well under serious conditions expected in balloon orbit. In particular, we showed that the PMT-ASSY monitors count rate of signal/background events for 16 hours in the PHENEX experiments. Dramatically, the count rate of the monitor counter increased significantly when the Crab-nebular/pulsar was locked in the detector field of view.