Jinshui Shi

A compact, portable pulse forming line

Some research has been done on making a compact, portable pulse forming line. A kind of ceramic based on SrTiO(3) is used as the dielectric of the planar pulse forming line. The ceramics dielectric constant is around 300 and can store more energy than water with the same volume. However, it is not easy to manufacture the large ceramic bulk but we did successfully manufacture 80 x 10 x 6 cm(3) ceramic bulks. Using this kind of ceramic bulk as the dielectric, we successfully made a compact, portable line that generated a voltage pulse up to 150 kV with a duration of about 92 ns.

A compact 300 kV solid-state high-voltage nanosecond generator for dielectric wall accelerator

Compact solid-state system is the main development trend in pulsed power technologies. A compact solid-state high-voltage nanosecond pulse generator with output voltage of 300 kV amplitude, 10 ns duration (FWHM), and 3 ns rise-time was designed for a dielectric wall accelerator. The generator is stacked by 15 planar-plate Blumlein pulse forming lines (PFL). Each Blumlein PFL consists of two solid-state planar transmission lines, a GaAs photoconductive semiconductor switch, and a laser diode trigger. The key components of the generator and the experimental results are reported in this paper.

Output of triple-pulse megahertz burst rate high-voltage induction device

Proof-of-principle experiments on the megahertz burst rate high-voltage triple-pulse induction acceleration concept are described and the experimental results are presented. High-voltage triple pulser supplies a triple-pulse burst at pulse rate of 1.25MHz to the acceleration gap of a ferrite induction device after the ferrite cores reset; a train of three 180kV pulses separated by 800ns was obtained in the accelerating gap. Each pulse has a full width at half maximum of 120ns and ±1% flattop of 50ns, with rise time of 40ns, respectively.

Coupling and decoupling of the accelerating units for pulsed synchronous linear accelerator

A pulsed synchronous linear accelerator (PSLA), based on the solid-state pulse forming line, photoconductive semiconductor switch, and high gradient insulator technologies, is a novel linear accelerator. During the prototype PSLA commissioning, the energy gain of proton beams was found to be much lower than expected. In this paper, the degradation of the energy gain is explained by the circuit and cavity coupling effect of the accelerating units. The coupling effects of accelerating units are studied, and the circuit topologies of these two kinds of coupling effects are presented. Two methods utilizing inductance and membrane isolations, respectively, are proposed to reduce the circuit coupling effects. The effectiveness of the membrane isolation method is also supported by simulations. The decoupling efficiency of the metal drift tube is also researched. We carried out the experiments on circuit decoupling of the multiple accelerating cavity. The result shows that both circuit decoupling methods could increase the normalized voltage.

Research on high-power laser diode used for triggering photoconductive semiconductor switch

A kind of laser diode with high power and short duration is described in this paper. The laser diode is used for triggering gallium arsenide photoconductive semiconductor switch (GaAs PCSS) in the experiment. The driver of the laser diode is based on RF MOSFET and it provides an ultra-fast pulse current, which has the rise-time, FWHM and peak current are 4ns, 17ns and 130A, respectively. The characteristics of the laser diode have been researched, including laser pulse waveform, optical field distribution, and limiting drive current. Using a combination of two laser diodes, the PCSS has a better performance than being triggered by single laser diode in the experiment.