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Density buildup of compact toroids by accelerator-region ionization of noble gas on CTIX

Author: Robert D. Horton
Requested Type: Poster Only
Submitted: 2012-12-07 12:32:41

Co-authors: D.Q. Hwang, D.W. Buchenauer, F.Liu, R. Klauser

Contact Info:
University of California, Davis
Box 303, 4435 N First St
Livermore, CA   94551
USA

Abstract Text:
Runaway electron (RE) mitigation by injection of compact toroid (CT) plasmas with high atomic number is a promising technique for runaway electron suppression. Compared to other methods, high-Z CTs of sufficient velocity (>100 km/s) have the potential to reach the tokamak magnetic axis on a sub-millisecond time scale. In addition to reducing avalanche RE production by collisions, high-Z CTs can cool RE by bremsstrahung effects. From theoretical calculations, using Xe ions, bremsstrahlung exceeds collisional cooling above 10 MeV RE energy, a value expected to be exceeded in large tokamaks [Bakhtiari, PRL, 2005]. Past experiments on the CTIX compact-toroid injector have demonstrated increased CT mass using snowplow accretion of puffed neutral gas by an initial hydrogenic CT. These experiments will be continued using a higher ratio of accreted high-Z plasma to H plasma, to maximize CT kinetic energy density. Density change will be measured both directly, by interferometry, and indirectly, by kinematic reduction of CT velocity due to mass increase. For low-Z puffed species the two results will be compared. Time-integrated, wavelength-resolved spectroscopic measurements will be used to identify the prominent emission lines of injected species. Selected individual spectral lines will be selected for time-dependent measurements, providing a species-specific measure of the density, velocity, and charge state of plasma formed from the accelerator-region gas puff.

Characterization: 1.3

Comments:
Group abstract: CTIX #1 of 2