| Flash X-ray radiographic technology is an important research and diagnostics method of materials transient state process.The pulse X-ray radiographic source driven by pulsed power technology is one of main high energy X-ray producing means.At present,the technology schemes of these pulse X-ray radiographic sources which are based on pulsed power technology can be classified as follows:Marx generator-Blumlein Pulse Forming Line(PFL)-Diode;Marx generator-Induction Voltage Adder(IVA)-Diode?Linear Transformer Driver(LTD)-Diode.In order to enhance pulse X-ray radiographic source reliability,a novel technology scheme is proposed.It is described as fast pulse forming unit(branch),based on Tesla transformer-IVA-Diode.The great feature of the novel technology scheme is its reliability because of the number of the "active" components,such as field distortion gas spark switch and laser trigger multi-gap multi-channel switches,can be reduced drastically,so as to decrease operational failure probability of pulse X-ray radiographic source.A pulse X-ray radiographic source adopting novel technology scheme,which uses only six field distortion gas spark switches,six laser trigger multi-gap multi-channel switches and twelve capacitors,has an output of delivering a 4 MV?100 kA electric pulse to the 40 ? matched impedance load.In the paper,the key technologies of the high reliability pulse X-ray radiographic source were researched.The working process of pulse X-ray radiographic source was analysised and the key components that impacts reliability of source were identified.Failure Mode and Effects Criticality Analysis(FMECA)of key components were carried out.The reliability model was established by above analysis.The reliability of individual component was decomposed on the assumption that the reliability of pulse X-ray radiographic source is a as well as considering components technology maturity.The reliability distribution laws of compoents as well as experimental and data processing methods was given.A Tesla transformer was designed and tested.The Tesla transformer has a capability to output 1.2 MV when its primary capacitors are charged to ±62 kV.In order to enhance reliability of Tesla transformer,a spaced secondary winding was adopted as well as surface field of inner-conductor insulator was optimized.A high reliability field distortion gas spark switch was designed and tested.The Weibull distribution predicts that self-breakdown probability of field distortion gas spark switch is 1×10-8 under the condition of ±55 kV charging voltage and 0.4 Mpa dry air dielectric.The experiment results show that its jitter was 8 ns with 96 kV amplitude,35 ns rising time(10%?90%),150 ns Full Width at Half Maximum(FWHM)pulse width.A 1.2 MV laser trigger multi-gap multi-channel switch which uses dry air as insulation dielectric was designed.The fitting formula shows that the relationship between self-breakdown voltage Vbr and air pressure p?gap space d?applied time t0.89 ist Vbr?p0.7 V?Vbr?d5/6?Vbr?p-0.193 respectively.The trigger jitter were 0.8 ns?2.6 ns?5.2 ns respectively when working ratio were 0,95?0.85?0.77 under condition of 70 mJ,266 nm,8ns laser beam.A novel method is proposed to synthesize an adjustable high voltage unipolar(bipolar)rectangular pulse by means of two(three)over-damped RLC nonsynchronous discharge circuits.A prototype was designed and tested.The results show that the prototype can output an independently-adjustable-parameters unipolar rectangular pulse with 17 kV amplitude,330 ns?5.45?s flattop duration and 110-350 ns rising time(0%-100%)on insulation specimen.The pulse X-ray radiographic source experimental results show that diode peaking voltage achieved 4.3 MV with 30 ns(10%,90%)rising time and the diode current was 99 kA.The failure mode proved that any branch outputted prior to normal time,the diode would be destroyed and no X-ray yielded,thus the corresponding azimuthal transmission line of IVA cavity would be applied to a same polarity high voltage pulse with a higher amplitude as well as any branch outputted posterior to normal time,the diode peaking voltage acheive 5/6 of that of normal mode,thus the corresponding azimuthal transmission line of IVA cavity would be applied to a reversal high voltage pulse with a higher amplitude... |
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