| As a means of high-speed radiography, flash x-ray generators are widely used to investigate various physical processes of explosive-driven hydrokinetics experiments. In recent decades, rapid development has been achieved in scientific research, industrial applications. As a result, new challenges are emerging for flash radiography, such as compactness in size, and capability of operating in multi-frame or repetitive rate mode to obtain necessary time-related information with little visual paradox. In this paper, a solid-state flash x-ray generator is developed, some results as following:(1) a solid-state pulsed power driver has been fabricated with photo conductive semiconductor swithes(PCSS) and stacked pulse forming networks(PFN) type of Blumlein. The PCSS makes use of GaAs, and hold on 30 kV with 10mm width. The method to design staked Blumlein PFN was explained in detail, the instaneous voltage pulse on PFN was calculated due to switches’s closing asynchronization. The results show high voltage pulse could be generated on matched impedance load with no less than 220 kV, about 64 ns duration, rise time less than 16 ns, and peak power up to 250 MW;(2) Flash x-ray diode has been studied, conclusions as following:a) A impedance model of industrial x-ray cold cathode diode is established, and calculated current based on the model is accordding to the experimental data; b) based on the industrial diode model, the impedance model of rod pinch diode(RPD) is established, too. and calculated current is almost close to data from reference articles and 1.2MV RPD experiments which has been finished in Pulsed Power Laboratory and Institute of Fluid Physics, CAEP; c) It is found that the duration of x-ray is identical to power of diode by experiments; d) The circuit model of diode and pulsed power driver could be established based on conclusions a,b,c in future.(3)Some experiments have been carried on, the results as follwing:a) The explosive emitted electron comes from plasma formed by absorbed gas and impurity on cathode surface, when the industrial x-ray diode of high configuration impedance operate on about 200 kV voltage. After a discharge shot, more than 2 ms interval was need to absorb enough gas on the surface of cathode, so the frame rate of flash x-ray generator was limited to 500 Hz by the absoption process; b) A novel cathode called as spoked metal-ceramic flashover cathode was proposed. Analysis demonstrated that permittivity and aperture of ceramic were key factors affecting electric field on triple points. Experiments showed that impedance stability and current of diode with the new cathode on the same configuration was about 3 times,2times than with metal method, respectively, ICCD images illuminated that plasma flare was distributed uniformly on aperture of the new cathode; c) the repetitive rate x-ray was generated with 1 kHz frame rate and 200kV voltage on burst 2 pulses mode limited by laser instruments, the two x-ray duration and energy coupled to diode is approximately identical; d) The electron emission process of new type cathode is:initial electron was generated from metal-ceramic-vacuum triple points, in succession plasma and multipled electron was formed on ceramic surface as a result of borbardment by initial electron. |
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