软X射线皮秒变象管扫描相机

软X射线皮秒变象管扫描相机技术是一种用变象管扫描相机测量X射线脉冲而能达到皮秒时间分辨率和一维微米级空间分辨率的技术。X射线扫描相机是研究伴有X射线辐射的一切高速瞬变过程的极为重要的测量工具。例如在激光核聚变的研究中,加热压缩期间靶球发生内爆过程中高温高密度等离子体的光谱辐射主要为软X射线,对这些软X射线的研究,可以获得有关等离子体的电子温度、电子能量分布、各种不稳定性的形态及这些参量随时间变化的资料。

PICOSECOND SOFT X-RAY STREAK CAMERA

An x-ray sheak camera with a time resolution of 30ps is described.The particular feature of our streak camera is the demountable windowless configuration. The quantum efficiency of the photocathode has been calibrated absolutely with a flurescent type soft x-ray monochromatic source. The relation between quantum efficiency and thickness of photocathodes has been studied. The optimum thickness for CsI is-500Å,the quantum yield of Au does not show significant change at 100-300Å thickness rangeThe quantum yield of 500Å CsI is as-20 times as that of 200A Au. polypropylene, For mvar and Parylene fillms have been studied as the substrates of the photocathode. The transmission of 1500A parylene film is the highest for photon energy below 1 kev and is selected to be the substrate.The avalanche transistors are selected to make the deflection circuit for the small jitter of the devices. 122N5681 transistors with similar performance is in series to get two ramp voltages with opposite polarity. The output ramp voltages are ? 1.4kV with ? 150 psec jitter. The write speed of the image converter with this circuit reaches 4? 109 cm/sec, and the nonlinearity of the write speed is<8%.The dynamic characteristics of the camera was measured with short pulse x-ray emission produced by mode-locked pulses irradiated on Au target. when the time resolution was measured, the x-ray pulse width was reduced by using suitable x-ray filter. A recorded pulse width of 33 ps is obtained. The dynamic spatial resolution of 8 Ip/mm was measured by putting a Ni chart at the front of photocathode. Multi-layer foil method was used to measure the dynamic range giving the result of> 32, The camera has been used by the researchers of the laser fusion and some primary results have been obtained.