Compact high current generator for x-ray radiography

Abstract

We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, X pinch, plasma focus, vacuum spark, etc. The X generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (20nF, 25nH, 0.2Ω, 100kV). It stores ∼0.8kJ at 80kV charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At 76kV charging voltage the generator provides ∼260kA with 120ns rise time and 5nH inductive load and ∼220kA with 145ns rise time and 10nH. Delay of output pulse relative to high voltage triggering pulse is ∼65ns with 5ns jitter. The dimensions of the generator are 1240×1240×225mm3 and the weight is ∼250kg, and only one high voltage power supply is required as additional equipment for the generator. The generator with a pumping system is placed on area about 0.5m2. Operation and handling are very simple, because no oil nor purified gases are required for the generator. The X generator has been successfully employed for experiments on the Ni X pinch load. X-ray pulse duration (full width at half maximum above 1keV) was about 5ns. Radiation yield Wr⩾500mJ was observed in the 1.2–1.5KeV range and Wr⩾20mJ in the 3–5keV energy range, which is comparable to results, obtained on the nanosecond accelerators. Clearly resolved images of 6μm wire indicate micron level size of hot spot. These results demonstrate possibility of this generator for application for x-ray backlighting.

Aluminum and tungsten X-pinch experiments on 100 kA, 100 ns linear transformer driver stage

“…Plasmas 18, 052702 (2011) X-ray burst jitter, which is defined as ½ P ðt À t av Þ 2 =n 1=2 , where t is the time of the first X-ray burst and t av is the average time of the first X-ray burst for n tests under the same conditions, 18 was $18 ns with 2-wire 8 lm W (about 45 ). The X-ray jitter was less than 5 ns on XP (400 kA, 40 ns), 18 less than 10 ns on X (260 kA, 120 ns), 12 and about 100 ns on a (320 kA, 1.2 ls) capacitor bank. 19 Our results fit the trend that the X-ray jitter probably increased with the current rise rate.…”

“…The X generator, composed by the capacitor bank and multigap spark switches, 12 and the small size pulse-accumulating source (SPAS), composed by capacitor-switch assemblies, 13 were constructed at High Current Electronics, Russian Academy of Sciences for X-pinch experiments. Another type is the fast linear transformer driver (LTD) which is currently being considered as a basis for future ignitionscale pulsed-power devices.…”

Developments of compact pulsed-power system toward X-ray sources

“…Magnetic pressure compresses the wire/plasma, and it can be further imploded by self-magnetic pressure. Radiation energy W r > 500 mJ was observed in the range 1.2-1.5 keV and W r > 20 mJ in the energy range 3-5 keV [1,2].…”

250 kA compact linear transformer driver for wire arrayz-pinch loads

“…The LTD cavity is a square design developed by the Institute for High Current Electronics in Tomsk, Russia [14], and the basic layout is given in Fig. 1.…”