Development of Gamma-ray burst Polarization Monitor(GAPOM)

2002年，我们建立了伽马射线暴偏振监测器(GAPOM)的基本模型--单胞模型和评价模型--八角形闪烁体。我们用实验室的X射线发生器和KEK光子工厂的同步辐射X射线对这两个模型进行X射线照射。将所得结果与仿真结果进行了比较。在2003年，我们采用分段塑料闪烁体作为散射体，实现了位置探测。它由52根长条塑料闪烁体组成。其中的康普顿损失提供了头寸信息。另一方面，我们使用了Geant4蒙特卡罗模拟，并将计算结果与所获得的数据进行了比较。2004年，我们搭建了CdTe磁头单元。它使用了16个CdTe半导体探测器作为吸收体，这导致了比NaI或CSI闪烁体更好的能量分辨率。我们用80keV偏振X射线照射KEK PF。光谱在最高X射线方向出现单峰，在最低X射线方向出现两个峰。它代表了康普顿散射角的依赖关系，与Geant4的模拟结果一致。获得的偏振探测效率为M=0.67，这是一个很高的数值，证实了很好的效率。同时，我们用H8500光电倍增管制作了分段塑料闪烁体。用10个这种类型的探测器，我们可以用气球实验观测蟹状星云。

In 2002,we build one-cell model which is a basic model of GAPOM(Gamma-ray burst polarization monitor), and octagonal scintillator which is an evaluative model of GAPOM. We irradiate X-ray to both models with X-ray generator in the laboratory and synchrotron X-ray in KEK Photon factory. Obtained results are compared to the simulation. The measured values such as photon detection efficiency, event ratios, polarization detectability are confirmed to be as expected.In 2003,we employed segmented plastic scintillator as the scatterer to have a position detectability. It consists of 52 long bars of plastic scintillators. The Compton loss in them gives position information. On the other hand we used Geant4 montecarlo scimulation and compared the calculated results with obtained data. They agree well.In 2004,we build CdTe head unit. It uses 16 pieces of CdTe semiconductor detectors as absorbers, which leads to a better energy resolution than NaI or CsI scintillators. We irradiated 80 keV polarized X-ray in KEK PF. The spectra showed single peak in the most-X-ray direction, and two peaks in the least-X-ray direction. It represents the angular dependence of the Compton scattering, and the results are as expected by Geant4 simulation. The obtained polarization detection efficiency was M=0.67, which is a high value and confirmed good efficiency.Also, we built 8x8 segmented plastic scintillators with H8500 photomultiplier. With 10 detectors of this type we can observe the Crab nebula with balloon experiment.