|icc_2006_phd_talk.pdf||2006-03-24 21:09:12||John Slough|
The Pulsed High Density Experiment: Concept, Design, and Initial Results
Author: John T. Slough
Submitted: 2005-12-20 15:44:41
Co-authors: S. Andreason, H. Gota, C.Pihl, G. Votroubek
University of Washington
223D Condon Hall
Seattle, WA 98195
The difficulty for most nuclear fusion concepts stems from the complexity and large mass associated with the confinement systems. A simpler path to fusion, that avoids these difficulties, can be achieved by creating fusion conditions in a different regime at small scale (rp ~ a few cm). An experimental program has been initiated that will explore the very compact, high energy density regime of fusion based on the magneto-kinetic compression of the FRC. Of all fusion reactor embodiments, only the FRC has the simply-connected closed field, linear confinement geometry, and intrinsic high β required for magnetic fusion at high energy density. In the area of reactor configuration improvements, the reactor envisioned for PHD provides for significant improvements in essentially all aspects of concern (A1-A4). PHD takes advantage of the linear confining geometry by incorporating a traveling, burning plasmoid, significantly reducing the wall loading as well as keeping the formation well separated from the burn chamber. Being small, compact, and at high β greatly improves the exposed surface to reacting volume ratio. Being pulsed eliminates the need for flux sustainment, and provides for regulation of the average wall loading. A wide range of reactor scenarios are compatible with PHD including liquid metal walls with the prospect of direct energy conversion through cyclical wall compression/expansion.
The energy required to compress the FRC to fusion conditions is transferred to the FRC via low field acceleration/compression coils. The FRC has demonstrated the confinement scaling with size and density required for fusion at a confining pressure well below the yield strength of materials allowing for solenoidal confining magnets. The requirement on the FRC closed poloidal flux is reduced to what has already been achieved so that the FRC should remain MHD stable through burn. Given the simplicity and small scale, it is ultimately the intent of the PHD experiment to bring the FRC to fusion breakeven conditions. The initial effort is to construct a source suitable for generating the start-up FRC parameters for a fusion gain > 1. The source section of the PHD experiment has been constructed with a unique segmented flux conserver that allows for simultaneous formation/acceleration. Several ionization and formation improvements have been initiated to enhance flux retention into the FRC equilibrium. High flux retention with operation employing only RF preionization has been achieved for the first time. Several new diagnostics have been constructed and applied to study FRC formation including visible bremstrahlung tomography, ion Doppler spectroscopy, interferometry, bolometry, and magnetic probe arrays. Results from these diagnostics will be presented.