The measurement of LHD plasmas using X-ray imaging polarimeter

我们研制了一种X射线偏振成像仪，用于测量大螺旋装置（LHD）上高温等离子体的X射线偏振。X射线偏振仪是利用气体中的光电效应来探测X射线偏振的仪器。为了跟踪光电子在气体中的轨迹，我们必须测量光电子电离气体所产生的电子分布。因此，我们使用气体电子倍增器（GEM），它在不丢失电子分布信息的情况下倍增电子数。并且倍增的电子由下面的没有CdTe层的CMOS传感器检测。它是一个精细的像素化电子阅读器，有效面积为2.5×2.5cm^2。我们探测到Fe Kα的X射线偏振，其能量为6.4keV。但是CMOS传感器在测量LHD等离子体之前发生了放电故障。因此，我们不能进行测量的LHD等离子体使用X射线偏振计。

We developed an X-ray imaging polarimeter to measure the X-ray polarization from high temperature plasmas on the Large Helical Device (LHD). The X-ray polarimeter is based on the photoelectric effect in gas to detect X-ray polarization. In order to trace a photoelectron track in the gas, we have to measure the electron distribution which is produced by a photoelectron ionizing the gas. Therefore, we make use of the Gas Electron Multiplier (GEM), which the number of electron is multiplied without losing the information of electron distribution. And multiplied electron are detected by the underneath CMOS sensor without a CdTe layer. It is a fine pixelized electron reader with the usable area of 2.5×2.5cm^2. We detected the X-ray polarization from the Fe Kα, which energy was 6.4keV. But CMOS sensor breaks down for an electric discharge before measure the LHD plasmas. So, we could not carry out the measurements of LHD plasmas using X-ray polarimeter.