Chris Pihl

Creation of a high-temperature plasma through merging and compression of supersonic field reversed configuration plasmoids

A new device, the Inductive Plasma Accelerator, was employed to simultaneously form and accelerate two oppositely directed field reversed configurations (FRCs) where the relative velocity (600 km s−1) of the plasmoids was much larger than their internal thermal motion. Upon collision all of the FRC directional energy was observed to be rapidly thermalized concurrent with complete magnetic reconnection of the two FRCs. Upon merging, the resulting FRC was compressed to kilovolt ion temperatures exhibiting a configuration lifetime better than predicted by past scaling of in situ formed FRCs. With the improved FRC confinement scaling, a pulsed plasma device based on this approach capable of achieving fusion gain is examined. For an FRC with a poloidal flux 20 mWb or greater, the fusion energy yield per pulse exceeds the plasma energy for compression fields of 10 T or more. The scaling is insensitive to the compression chamber radial scale, providing for the possibility of a very compact fusion neutron source.

Research and development of pseudospark switch drivers

The pseudospark (thyratrons TPI- and TDI-type) switch drivers design and applications in various pulsed power systems are presented. Drivers are constructed using modern IGBT transistors and triggered compact spark gaps, and feature both manual and remote digital control (CAN, Ethernet). TDI-thyratrons can serve as a replacement for ignitron, spark gap and triggered vacuum switches. The TDI drivers are made with multiple outputs for triggering up to 4 thyratrons in parallel or with HV isolated output for applications where the igniter and hydrogen reservoir of the thyratron are under high (transient) voltages. TPI-thyratrons were designed recently however, we have extensive experience in application and the methods of triggering/controlling of these switches. The trigger unit is a simple relaxation oscillator with DC and Pulsed Preionization, including single, double and triple pulse triggering techniques. In particular it is shown that when the requirement for a driver is to provide minimum time jitter (less 0.5ns), high anode current pulse stability and extended lifetime, the best option is triple-pulse triggering. Circuit design for trigger drivers BZ-TP/10 for TPI-thyratrons, optimized for the operation of the particle accelerator LIU-2 are described.

Steady Operation of an FRC Thruster on Martian Atmosphere and Liquid Water Propellants

Nomenclature Bb, Bbias = magnitude of preexisting (vacuum) axial magnetic field B = amplitude of rf rotating magnetic field Bz = axial magnetic field change due to RMF driven currents (superscript M denotes maximum) Bext = magnitude of magnetic field external (radially) to the FRC  = plasma pressure normalized to external (vacuum) field C = capacitance value  = classical skin depth = (2/0) 1/2

Prospective pulsed power applications of pseudospark switches

In this paper, results of comparative tests of commercially available TDI model pseudospark switches (PSS, also known as: cold cathode thyratrons, copper vapor & low pressure switches) versus mercury type D ignitron switches in Field Reversed Configuration (FRC) installations with energy storage up to 14kJ, operating voltage 5–40 kV, peak currents Imax =190 kA, jitter 4–10 ns are presented.

Visible bremsstrahlung tomographic diagnostic for the pulsed high density field-reversed configuration experiment

A diagnostic suite for the source section of the pulsed high density field-reversed configuration (FRC) experiment has been constructed to investigate the equilibrium and stability of FRC plasmas. In particular, a visible bremsstrahlung tomographic system has been designed and implemented. Three types of tomographic analyses for FRCs are performed: a Fourier fit method (Cormack-Granetz), a maximum entropy method, and a minimum Fisher method utilizing code developed for the TCV tokamak experiment in Switzerland [Anton et al., Plasma Phys. Controled Fusion 38, 1849 (1996)]. Results from the different methods and end-on imaging from the fast-framing camera are compared showing relative agreement of FRC internal structures between all measurements.