High-Current, Solid-State Switch for Dense Plasma Focus Applications

Project Elpis investigates the use of a plasma focus (PF) as a commercial radiation source, ideally for fusion energy generation. A PF is a type of pinch in which a short-lived, hot, and dense plasma is created, in which fusion reactions can take place. Since this is an energy-dense pulsed apparatus, eventually a suitable pulse source must be designed. First, the requirements for the initial research prototype have been determined (10 kV, 10 kJ, 500 kA, and 25 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>s). Due to the requirement for a long operational lifetime, in this work, we will investigate a solid-state pulse switch implementation and develop a first (lower power, 1-kV) prototype for the initial research demonstrator. Different solid-state switches (an insulated gate bipolar transistor (IGBT) and two MOS-gated thyristors) have been experimentally selected for their current conduction capabilities in the required regime, after which a final selection is made. Next, a sinusoidal discharge pulse source is designed to measure the current-sharing performance of four such switches in parallel. The results show a desirable current sharing performance (<15% difference) below 20-kA peak. Simultaneously, a simulation model is developed to aid in further system design. Next, a switch module consisting of 16 switches in parallel has been designed. Again, sufficient current sharing behavior is observed (<5% difference) up to 140-kA peak (single-shot and destructive) and 70-kA peak for repetitive operation. Finally, simulations demonstrating the feasibility of the 500-kA prototype are shown, as well as a successful simulated operation with PF.