Status of radiographic X-ray source driven by 4 MV, 80 kA induction voltage adder
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摘要: 介绍了西北核技术研究院研制的4 MV脉冲X射线闪光照相装置(“剑光二号”)系统组成和实验结果。装置基于感应电压叠加器(IVA)驱动阳极杆箍缩二极管(RPD)技术,主要由前级脉冲功率源、感应电压叠加器和RPD等组成。前级脉冲功率源由两台3.2 MV低电感Marx发生器和四路同轴水介质线组成。每台Marx同时给两路脉冲形成线(特征阻抗6 Ω、电气长度30 ns)充电,充电峰值时间约370 ns。每路水介质线采用两级脉冲压缩,为感应腔馈入约1 MV/160 kA/60 ns电脉冲。电触发SF6气体开关、自击穿水开关分别用作主同步开关和脉冲陡化开关。感应电压叠加器采用四级1.5 MV感应腔串联,每级感应腔采用单点馈入结构。次级采用真空绝缘传输线实现电压叠加和功率传输,特征阻抗由30 Ω线性增大至120 Ω。采用4 MV电压下综合性能较优的RPD来产生强脉冲X射线。装置目前达到技术指标:输出电压4.3 MV、脉冲前沿(10%~90%) 21 ns、半高宽约70 ns、二极管电流85 kA,X射线半高宽约55 ns,整机延时(从Marx触发器输出到X射线产生)约749 ns,标准偏差约7 ns。当RPD阳极采用直径2 mm钨针时,正前方1 m处剂量约15.5 rad(LiF),正向焦斑约1.4 mm。Abstract: This paper presents the design details and experiment results of a 4 MV facility developed for flash X-ray radiography in Northwest Institute of Nuclear Technology (NINT). The facility is based on the technology of an induction voltage adder (IVA) driving a rod pinch diode (RPD). The facility mainly consists of the prime power source, induction voltage adder, and RPD. The prime power source consists of two 3.2 MV low-inductance Marx generators and four deionized-water coaxial lines. Each Marx generator charges two 6 Ω, 30 ns pulse forming lines (PFLs) in less than 370 ns. There exist two-stage pulse compressions for each pulseline, providing four forward waves with peak voltages of 1 MV at current of 160 kA with a duration time of 60 ns. Four electrically-triggered SF6 gas switches serve as energy transfer switches from PFLs to outlines, and then four self-breakdown water switch are used to sharpen the risetime and reduce the prepulse. The IVA consists of four-stage induction cavities stacked in series, each of which almost operates at 1.5 MV voltage. A vacuum insulated transmission line (without magnetic insulation) is used for power addition. The RPD is chosen to create X rays through bremsstrahlung. At present, the IVA could produce a 4.3 MV voltage with a risetime (10%-90%) of 21 ns and a FWHM time of 70 ns. The diode current is about 85 kA, and the FWHM time of X rays is about 55 ns. The delay time from Marx trigger to the X-ray output is about 749 ns, with a standard deviation of about 7 ns. With a 2-mm diameter tungsten rod used, the X-ray dose is about 15.5 rad (LiF) at 1 m straight ahead, and the spot size is about 1.4 mm.
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表 1 装置连续10发次实验主要输出指标
Table 1. Key output parameters of the Jianguang-II facility over a ten shot sequence
shot output voltage/MV risetime/ns diode current/kA X-ray FWHM time/ns dose@1 m/rad(LiF) delay time/ns 2019-017 4.3 22 85.3 58 14.8 748 2019-018 4.6 24 84.1 54 15.7 749 2019-019 4.5 20 85.6 56 16.0 748 2019-020 4.5 20 80.5 54 14.5 745 2019-021 4.4 24 86.2 56 16.1 740 2019-022 3.9 20 84.9 58 14.2 741 2019-023 4.5 21 84.2 53 15.6 748 2019-024 4.2 19 87.0 52 15.4 756 2019-025 4.3 17 88.0 52 16.9 756 2019-026 4.2 21 82.5 52 15.4 762 average 4.3±0.2 21±2.1 84.8±2.2 55±2.4 15.5±0.8 749±7 表 2 剑光一号和剑光二号装置输出指标的比较
Table 2. Comparation of output parameters between the Jianguang-I and Jianguang-II facilities
output voltage/MV diode current/kA X-ray FWHM time/ns radiated dose @1 m/rad(LiF) spot diameter/mm Jianguang-I facility 2.4 51 46 3.7 1 Jianguang-II facility 4.3 85 55 15.5 1.4 -
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