The measurement of LHD plasmas using X-ray imaging polarimeter

研制了一种x射线成像偏振计，用于在大型螺旋装置（LHD）上测量高温等离子体的x射线偏振。x射线偏振计是利用气体中的光电效应来探测x射线偏振的。为了追踪气体中的光电子轨迹，我们必须测量由光电子电离气体所产生的电子分布。因此，我们采用了气体电子倍增器（GEM），在不丢失电子分布信息的情况下，将电子数量倍增。在没有碲化镉层的情况下，多层电子被下方的CMOS传感器检测到。它是一个精细的像素化电子阅读器，可用面积为2.5×2.5cm^2。我们探测到了能量为6.4keV的Fe Kα的x射线偏振。但CMOS传感器在测量LHD等离子体之前会因放电而失效。因此，我们无法使用x射线偏振计对LHD等离子体进行测量。

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.