Abstract Details

Bias Field Operation on SSPX

Author: Reginald D. Wood
Submitted: 2005-12-21 16:15:07


Contact Info:
Lawrence Livermore National Laboratory
7000 East Ave.
Livermore, CA   94550

Abstract Text:
We have carried out experiments to explore how different vacuum magnetic-field configurations affect plasma performance on SSPX. Nine independently controllable magnetic field coils and power supplies can be programmed to obtain a wide range of field line configurations: those with vacuum magnetic field lines passing parallel to the side walls of the SSPX chamber and those with diverging fields passing through the side walls of the chamber. During operation using the injector coils only, the threshold at which the magnetic pressure becomes high enough to eject plasma from the gun into the flux conserver is about twice that of the plasma inside the separatrix. This type of operation provides strong helicity injection that can lead to increased magnetic turbulence resulting in poor energy confinement. High performance discharges are obtained by carefully adjusting the injected current and injector magnetic flux to produce a flat to slightly peaked radial current profile. Additional bias magnetic flux can be programmed to optimize edge currents close to that of the confined plasma and provides a means to explore the transport of current drive by magnetic helicity injection. A wide range of configurations have been tested using the bias coils and initial results show little improvement in energy transport or magnetic field generation over operations without the coils. Energy confinement and magnetic field generation during operation with the bias coils will be presented. This work performed under the auspices of the USDOE by LLNL under contract 7405-Eng-48.

Characterization: A5


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