A Sweep Circuit Designed For X-Ray Streak Cameras

X-Ray streak cameras with high spatial-temporal resolution are widely used in the ultrafast diagnosis fields. In laser fusion, X-Rays carry a lot of important information about the physical process inside. The time range in laser fusion is just several nanoseconds, and the spatial range is smaller than a few hundreds of microns. Thus the X-Ray diagnosis using X-Ray streak cameras is very important in laser fusion. With the development of the laser fusion experiments, devices with higher performance are demanded to analyze the complicated physical process of laser fusion in detail. The sweep circuit, which makes the electron beam deflected vertically and linearly with respect to time, is the reason why steak cameras are capable of storing the temporal information in the spatial information. An increase in the slope of the sweep voltage can raise the sweep rate, which improves the temporal resolution. In addition, it is helpful for adjustments in streak cameras to analyze the operation theory of the sweep circuit. And it is beneficial for the error analysis to figure out the relation between the quality of the sweep pulse and the measure results. A fast sweep circuit based on avalanche transistors is developed for the purpose of improving the performance of the sweep circuit currently used. The main contents of this thesis are presented in the follow:1. Analyze the factors influencing the temporal resolution and conclude that increasing the sweep rate which depends on the slope of the sweep voltage is the most possible method to improve the temporal resolution.2. Establish an equivalent sweep circuit: a RLC resonator. And obtain the relation between the design parameters and the shape of the sweep voltage.3. Establish a 1-D model to describe the process of current mode second breakdown(CMSB) in avalanche transistors aroused by the rapidly increasing current caused by the avalanche multiplication effect, which is a crucial factor in the operation of avalanche transistors.4. Design and manufacture a sweep circuit based on ZetexFMMT417 avalanche transistors, which is half size of the circuit currently used.5. The performance of the sweep circuit is measured such as magnitude, edge, delay and the trigger threshold on oscilloscopes. Compared with the sweep circuit of a 3 ns sweep duration currently used, two magnificent improvements are presented that the delay is cut down by 12 ns; and the overshoot or undershoot is limited, thus the ‘overwrite’ is canceled. The circuit installed in a six electrodes type streak camera, and tests have been performed to measure the sweep rate and the linearity. Excellent results are obtained that the nonlinearity is 1.95% and the sweep rate is 61.4 ps/mm.