Pulse modulators for ion recirculator cells

We report here on a study of circuits for the accelerating modules in a recirculator. Future requirements are challenging: flat-top (or slightly rising) pulses with varying duration; beam currents as high as a kiloampere; a train of 50-100 pulses with instantaneous repetition rate as high as 50 kHz; and high efficiency. An accelerating module providing 200-400 kV to the beam might house 30-100 cores. Our study uses cores of moderate size - we chose 20.3 cm diameter. The pulsers use tapered pulse-forming networks and provide core reset, 20-μs recovery and variable duration. A novel addition is a separate, 150-kV, 200-A modulator used to simulate a constant-current ion beam, allowing a direct measurement of the cell dynamic impedance and the modulator-to-beam conversion efficiency. The basic goal of the project is to explore the use of solid-state switches and low-voltage circuits with efficiency and low cost in mind. In this report we describe our circuits and salient results, then offer comments and conclusions