E. Bickford Hooper

Theoretical aspects of the use of pulsed reflectometry in a spheromak plasma

Pulsed reflectometry using both ordinary (O) and extraordinary (X) modes has the potential of providing time- and space-resolved measurements of the electron density, the magnitude of the magnetic field, and the magnetic shear as a function of radius. Such a diagnostic also yields the current profile from the curl of the magnetic field. This research addresses theoretical issues associated with the use of reflectometry in the Sustained Spheromak Physics Experiment spheromak experiment at the Lawrence Livermore National Laboratory. We have extended a reflectometry simulation model to accommodate O- and X-mode mixed polarization and linear mode conversion between the two polarizations. A Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) formula for linear mode conversion agrees reasonably well with direct numerical solutions of the wave equation, and we have reconstructed the magnetic pitch–angle profile by matching the results of the WKBJ formula with the mode conversion data observed in simulations using a least-...

QUASI-STATIC MODEL OF MAGNETICALLY COLLIMATED JETS AND RADIO LOBES. II. JET STRUCTURE AND STABILITY

This is the second in a series of companion papers showing that when an efficient dynamo can be maintained by accretion disks around supermassive black holes in active galactic nuclei, it can lead to the formation of a powerful, magnetically driven, and mediated helix that could explain both the observed radio jet/lobe structures and ultimately the enormous power inferred from the observed ultrahigh-energy cosmic rays. In the first paper, we showed self-consistently that minimizing viscous dissipation in the disk naturally leads to jets of maximum power with boundary conditions known to yield jets as a low-density, magnetically collimated tower, consistent with observational constraints of wire-like currents at distances far from the black hole. In this paper we show that these magnetic towers remain collimated as they grow in length at nonrelativistic velocities. Differences with relativistic jet models are explained by three-dimensional magnetic structures derived from a detailed examination of stability properties of the tower model, including a broad diffuse pinch with current profiles predicted by a detailed jet solution outside the collimated central column treated as an electric circuit. We justify our model in part by the derived jet dimensions in reasonable agreement with observations. Using these jet properties, we also discuss the implications for relativistic particle acceleration in nonrelativistically moving jets. The appendices justify the low jet densities yielding our results and speculate how to reconcile our nonrelativistic treatment with general relativistic MHD simulations.

Whistler wave driven plasma thruster

High density plasma can be generated by electron cyclotron resonance heating (ECRH) using whistler waves at densities for which the plasma frequency is much higher than the cyclotron frequency. This will result in a thruster operating at specific impulses of 103–104 s and much higher power and thrust densities than usual for ECRH devices. As the plasma generation is by electromagnetic waves, there are no electrodes, and wall material problems are greatly eased, permitting reliable, long lifetime operation. We report on the modeling of such a thruster, including plasma flow as well as losses to an end wall and ionization. A helical antenna to couple the waves into the plasma column is analyzed, including effects of the anisotropic plasma dielectric constant. An initial experiment to test the concept is planned.

The Fusion Science Research Plan for the Major U.S. Tokamaks

This is the May 1996 report of a subpanel of the US Department of Energy Fusion Energy Sciences Advisory Committee (FESAC), charged with conducting a review of the progress, priorities and potential near-term contributions of TFTR, DIII-D and Alcator C-MOD (and other facilities as appropriate) as part of the transition to a Fusion Energy Sciences Program and produce an optimum plan for obtaining the most scientific benefit from them.

Report of the FESAC Panel on a Burning Plasma Program Strategy to Advance Fusion Energy

This panel was set up by the U.S. Department of Energys Fusion Energy Sciences Advisory Committee in response to a request from the department to prepare a strategy for the study of burning fusion plasmas. Experimental study of a burning plasma has long been a goal of the U.S. science-based fusion energy program. There is an overwhelming consensus among fusion scientists that we are now ready scientifically, and have the full technical capability, to embark on this step. The fusion community is prepared to construct a facility that will allow us to produce this new plasma state in the laboratory, uncover the new physics associated with the fusion burn, and develop and test new technology essential for fusion power. Given this background, the panel has produced a strategy to enable the United States to proceed with this crucial next step in fusion energy science. The strategy was constructed with awareness that the burning plasma program is only one major component in a comprehensive development plan for fusion energy. A strong core science and technology program focused on fundamental understanding, confinement configuration optimization, and the development of plasma and fusion technologies essential to the realization of fusion energy. The core program will also be essential to the successful guidance and exploitation of the burning plasma program, providing the necessary knowledge base and scientific workforce.

Innovative Confinement Concepts Workshop—2002: Conference Report

The Innovative Confinement Concepts Workshop, ICC2002, provided a forum for presentations and exchange of ideas on the science and status of innovative concepts in the U.S. Fusion Energy Program. The workshop, held at the University of Maryland on January 22–24, 2002, included oral presentations addressing the important science and status of the concepts, posters focussed on details of the work, a skunkworks for novel ideas, and breakout sessions preparing for the July 2002 fusion energy Snowmass meeting. This report summarizes the oral presentations. A web site (https://wormhole.ucllnl.org/ICC2002/) has been established with the abstracts and many of the presentations, both oral and poster, from the workshop.

Report of the U.S. Department of Energy Fusion Energy Sciences Advisory Committee panel on burning plasma physics

This is the report of a panel set up by the U.S. Department of Energy Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter on October 5, 2000, from Dr. Mildred Dresselhaus, then Director of the DOEs Office of Science. In that letter, Dr. Dresselhaus asked the FESAC to investigate the subject of burning plasma science. The report addresses several topics, including the scientific issues to be addressed by a burning plasma experiment and its major supporting elements, identification of issues that are generic to toroidal confinement, and the role of the Next-Step Options (NSO) Program.

A multi‐megawatt electric thruster test facility

A Multi‐Megawatt Test Facility (MTF) for electric thrusters is described, based on modifications of the Lawrence Livermore National Laboratory (LLNL) Magnetic Fusion Test Facility‐B (MFTF‐B). MTF would use the large (66 m long, 11 m maximum radius) vacuum vessel, the cryopumping system including 1000 m2 of cryopanels and 11.5 kW cooling at LHe temperature, 250 MVA dedicated power line, and other existing facilities. As a result, significant cost and time savings would be realized over construction of a completely new test facility.