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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...
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...
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