| Co-Investigator(Kenkyū-buntansha) |
MUTO Sadatugu National Institute for Fusion Science, LHD project, researcher, 大型ヘリカル研究部, 助手 (40260054)
GOTO Motoshi National Institute for Fusion Science, LHD project, researcher, 大型ヘリカル研究部, 助手 (00290916)
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| Research Abstract |
During past 4 years we experimentally verified many advantages on back-illuminated CCD detector, which was used in visible, vacuum ultraviolet (VUV) and x-ray plasma spectroscopy. The CCD detector was being operated without any technical trouble through this research. As a most important result it was concluded that no limit on the measurement existed for such variations of spectroscopy. Excellent characteristics of the CCD detector on the stability of sensitivity and the spatial-and time-resolution, which were examined in this research, can be applicable to another field of scientific research.
In the visible region, the characteristics of the back-illuminated CCD were compared with photodiode array (PDA) with image intensifier (II) used for the visible spectroscopy. The characteristics of the CCD was much superior to the PDA+II in many terms of sudden detector destruction due to strong visible light input, sensitivity change over long period, spectral profile shape at foot position, s
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patial resolution, dynamic range for signal detection, time resolution, operational stability, S/N ratio etc.
In the VUV region, the characteristics of the back-illuminated CCD were compared with PDA with micro-channel plate (MCP). The detectors were installed on a 20cm normal incidence spectrometer and checked using CHS and LHD plasma light. The result was the same as the visible case. The CCD detector had much better quality. Especially, the CCD did not show, any damage to increase of the vacuum pressure of the spectrometer, although the operation of M C P was very sensitive to the pressure increase and the CCD was easily damaged by the pressure increase. In addition, the use of CCD as a detector of VUV spectrometer enabled us a very easy setting and adjustment of the grating because we could exactly monitor the focus image at the detector plane using 0th-order (visible) light.
In the x-ray region, the characteristics of the CCD detector were compared with usually used multiwire proportional counter (MWPC ). In x-ray emissions. from plasmas the intensity is a large function of electron temperature. Then, the x-ray intensity largely changes during a discharge and is easily enhanced by an additional heating. As a result, the x-ray spectroscopy was limited by the detector signal dynamic range. The use of the CCD detector instead of the MWPC increased the detector dynamic range by 1000 times. Until now the ion temperature measurement by the x-ray spectroscopy included a considerably large error bar. However, we could completely resolve the problem using the CCD detector. Less
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