Internal field probing of translating FRCs
Magnetic field probes have been employed to study the internal field structure of Field-Reversed Configurations (FRCs) translating past the probes in the FRX-C/T device. Internal closed flux surfaces can be studied in this manner with minimal perturbation because of the rapid transit of the plasma (translation velocity v/sub z/ approx. 10 cm/..mu..s). Data have been taken using a 5-mtorr-D/sub 2/ gas-puff mode of operation in the FRC source coil which yields an initial plasma density of approx. 1 x 10/sup 15/ cm/sup -3/ and x/sub s/ approx. 0.40. FRCs translate from the approx. 25 cm radius source coil into a 20 cm radius metal translation vessel. Of many translation conditions studied, the condition considered here is translation into a weak guide field resulting in expansion of the FRC to conditions of density approx. 3 x 10/sup 14/ and x/sub s/ approx. 0.7. The expected reversed B/sub z/ structure is observed. Evidence of island structure is also observed. Fluctuating levels of B/sub THETA/ are observed with amplitudes less than or equal to B/sub 0//3 and values of flux approx. 4 x the poloidal flux. Values of ..beta.. on the separatrix of ..beta../sub s/ approx. = 0.3 (indexed to the external field) are implied from the field measurements. This decrease of ..beta../sub s/ with increased x/sub s/ is expected, and desirable for improved plasma confinement.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Mathematical Sciences Northwest, Inc., Bellevue, WA (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 6294056
- Report Number(s):
- LA-UR-84-3575; CONF-8411111-4; ON: DE85003732
- Resource Relation:
- Conference: Japan/US joint symposium on compact toroid research, Hiroshima, Japan, 13 Nov 1984
- Country of Publication:
- United States
- Language:
- English
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