A compact lightweight 125 mm thyristor for pulse power applications

A compact, lightweight, symmetric 125 mm diameter silicon thyristor is under development by SPCO for high current millisecond pulse power applications, i.e. electric launchers. This thyristor has a drastically reduced size and weight. This is due to a new design which eliminates the need for large, heavy refractory metal substrates and endpieces, employs an alloyed anode interface for high surge currents, and a high integrity plastic disk package. The package is less than one-fifth the volume and weight of a package utilizing standard construction technology, and provides for double sided cooling and a lower thermal resistance from junction to sink of 0.0033 K/W. Exploratory testing has been performed at ARL using a 10 milliohm, 0.5 ms (FWHM) PFN. With a matched load the pulser at 4 kV can provide peak currents of 200 kA with a di/dt in excess of 1 kA//spl mu/s. Initial results on the temporal behaviour as a function of operating levels under matched load conditions are presented. A computer simulation of the behaviour of the device using the actual current pulse shape was consistent with the experimental results. The present six star gate design does not provide the rate of plasma spreading required for 200 kA operation. A computer model using an involute gate structure indicates that the peak current objectives are achievable. The development of this switch will permit the construction of compact, lightweight high voltage series switch stacks for electric guns.