Andrew Seltzman

Design and modeling of nanocrystalline iron core resonant transformers for pulsed power applications

A high power resonant three phase switch mode power supply has been constructed at University of Wisconsin to drive a klystron tube. Utilization of a resonant transformer with loosely coupled secondaries allows generation of high boost ratios exceeding the turns ratio while providing high efficiency. Use of nanocrystalline iron cores provides high volt seconds while maintaining low loss at high switching frequencies. Analytic models are developed and compared to measured data from two different size resonant transformers and effects of turns ratio, load resistance, and primary are examined and compared to theory.

Design of an 80kV, 40A resonant switch mode power supply for pulsed power applications

A high power resonant three phase switch mode power supply with low output ripple has been constructed at University of Wisconsin to drive a klystron tube. Output voltage stabilization has been achieved by adjusting switching frequency toward resonance to compensate for capacitor bank droop. The power supply input is connected to a 900V electrolytic capacitor bank and three transformers with loosely coupled resonant secondaries are connected to a doubling three phase rectifier to provide an 80kV, 40A output. A snubber and crowbar sparkgap protects the klystron in the event of an internal arc, while output filters reduce voltage ripple in the output.

Electron Bernstein Wave Experiment on the Madison Symmetric Torus

A 0.25 MW system designed to heat electrons and drive current via the electron Bernstein wave is in its early stages of operation on the Madison Symmetric Torus reversed field pinch. The antenna is a grill of four half‐height S‐band waveguides with each arm powered by a separate, phase controlled traveling wave tube amplifier. Coupling to the plasma (as measured by ratio of reflected power) is very dependent on the relative phasing. The total reflected power can be maintained at or below 25%, similar to that measured for a two‐waveguide full height grill[1]. The antenna face is outfitted with a pair of triple Langmuir probes to measure local electron density; the density gradient at the upper hybrid resonance (typically within 1–2 cm of the antenna) is expected to strongly influence coupling efficiency. Conditioning of the antenna is currently underway and total system power is expected to reach 0.25 MW, or roughly a fourth of the Ohmic input power in target plasmas. The x‐ray spectrum (5–200 keV) is moni...