(A) study of soft x-ray imaging for the estimation of electron temperature in plasma using micro-channel plate

Abstract

Micro-channel plate (MCP) is a thin planar device which can detect UV and soft x-rays of the energy up to a few hundreds keV. Therefore it has been widely used in science research and industries, especially in plasma facilities, where UV and/or soft x-rays are often analyzed to diagnose the characteristics of the plasma. It has a relatively high quantum gain up to a million. An MCP is composed of a bundle of individual short glass tubes, through holes of which the primary electrons are multiplied, so the gain of individual channels may yields a significant non-uniformity between each channel, which again distorts the measured soft x-ray image. The x-ray spectra from the obtained MCP images are compared with a single channel silicon diode spectrometer, in order to the map out the gain non-uniformity. In the real plasma facilities, fine calibration of linearity and uniformity is often limited due to the integrated nature of MCP’s signal over all energy radiations and the integration time. In this study, we developed a soft x-ray spectroscopic imager using a pin hole collimator, changeable aluminium filters and an MCP of 28 mm diameter. Using this measurement system, we established the estimation process of x-ray fluence through the system calibration experiments. And if separate spectrometer is supplied, the estimation of electron temperature in plasma can be done. Surely the x-ray fluence data are meaningful things themselves to diagnose the state of plasma.