The measurement of LHD plasmas using X-ray imaging polarimeter

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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.