Double Pulse Generator for Unipolar Discharges in Long Plasma Tubes for the AWAKE Experiment

High-voltage pulsed gas discharges can produce suitable plasma for wakefield particle acceleration experiments. Such plasmas are challenging loads characterized by significant parasitic elements and fast impedance transitions leading to hard-to-predict dynamic behavior. This hinders the use of solid-state pulse generators to replace inefficient and limited lifetime spark gaps or thyratrons. This article presents the development, simulation, and test of a new semiconductor-based double pulse generator for a 5-m-long plasma load. It uses two successive pulses. The first one consists of a step-up inductive discharge and leads to a low current arc (10 A) enough to set the plasma to a low impedance state. The second pulse, generated by a capacitive discharge, increases the arc current up to 400 A. The pulses are generated by two subcircuits integrated together and tested, showing a substantial reduction of the required instantaneous power compared with the one needed using a single pulse and resulting in a high ionization fraction gas discharge pulse with nanosecond jitter.