Experimental investigation of dynistors and dynistor based pulsers

The US Army Research Laboratory has evaluated reverse switching dynistors (RSD) and dynistor based pulsers from the Ioffe Institute, St. Petersburg, Russia. The dynistor is an asymmetric thyristor with an alternating p⁺ and n⁺ structure in its anode. It is a two-terminal device. Application of a reverse voltage across the dynistor makes the device operate like a transistor during turn-on, and generates a uniform plasma distribution enabling fast turn-on. This reduces commutation dissipation and permits high peak current operation to be achieved for submillisecond pulses. An 80 mm diameter device was evaluated in a pulser using a 0.5 ms (FWHM), 10 mΩ PFN with a matched load. Work with a 2.3 kA driver demonstrated operation at di/dt of 1.7 kA/μs (26.6% to 70.7%) and 177 kA. Differentiation of the current pulse gives a di/dt of 2.8 kA/μs. The dynistor exceeded the performance of standard symmetric devices of up to 100 mm diameter. This series of tests was performed using two devices stacked in series with a diode in series to protect against voltage reversal. The two devices were triggered by a single trigger unit. The trigger unit must be capable of holding off full operating voltage and generating a high voltage reverse pulse for turn-on. A saturable reactor is required to isolate the main discharge circuit during the turn-on period. This technique can be extended to many devices in series, thus enabling a high voltage switch to be built using a single driver. Two dynistor based pulsers, the MPG-1 and the MPG-2, were tested. Details of the measurements are discussed