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Fast crowbar switches are needed to protect high power amplifier tubes from potentially damaging internal arcs. Such a switch needs to have a fast turn-on to a low impedance state while also having the capability to discharge large amounts of stored energy. These switches have historically been thyratron tubes or spark gaps [1]. We will describe a new hybrid solid-state approach that combines a small...
Pulsed gradient magnetic fields are required for magnetic resonance imaging (MRI). Many imaging sequences (e.g., echo planar imaging, diffusion tensor imaging) could be improved with shorter gradient pulses. MRI systems currently available typically require ramp times of hundreds of microseconds. The goal of the work described here is to achieve very high gradient fields, with very short rise times...
Lasers have been used to control semiconductor switching devices either by laser gating or laser triggering. Laser gating requires the optical source to generate of all charge carriers which would be prohibitively expensive in terms of optical power to use with high current devices. Laser triggering only generates charge carriers in the gate region of the device which still results in a slow turn-on...
A solid state pulser, designed and constructed by PLEX LLC, has been tested at the Naval Research Laboratory. It has achieved more than 11,500,000 continuous shots at 10 pps and generated 200 kV, 4.5 kA, 300 ns pulses, and the standard deviation time jitter of the output voltage was less than ± 1 ns. The pulser consists of a 12 stage Marx, coupled with a 3rd harmonic stage, a main magnetic switch,...
There are many applications currently using spark gap switches which would like to have the long lifetime of a solid state switch such as a silicon thyristor. This was not possible till now due to the relatively long turn-on times of silicon thyristors. The turn-on time of a silicon thyristor can be improved by providing the charge carriers using a laser source rather than an electrical source. Then...
This paper describes the design and performance of solid state switches developed for applications ranging from low repetition rates with moderate average power to high repetition rates with high average power. These switches use multiple series connected small 5300 V thyristors capable of 14 kA peak currents and >25 kA/mus rate of current risetimes. These switch designs use patented self powered...
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