Hot electron plasma equilibrium and stability in the Constance B mirror experiment

Technical Report · Fri Apr 01 04:00:00 EST 1988

OSTI ID:6988788

Chen, Xing

An experimental study of the equilibrium and macroscopic stability property of an electron cyclotron resonance heating (ECRH) generated plasma in a minimum-B mirror is presented. The Constance B mirror is a single cell quadrupole magnetic mirror in which high beta (..beta.. less than or equal to 0.3) hot electron plasmas (T/sub e/approx. =400 keV) are created with up to 4 kW of ECRH power. The plasma equilibrium profile is hollow and resembles the baseball seam geometry of the magnet which provides the confining magnetic field. This configuration coincides with the drift orbit of deeply trapped particles. The on-axis hollowness of the hot electron density profile is 50 /+-/ 10%, and the pressure profile is at least as hollow as, if not more than, the hot electron density profile. The hollow plasma equilibrium is macroscopically stable and generated in all the experimental conditions in which the machine has been operated. The hollowness of the plasma pressure profile is not limited by the marginal stability condition. Small macroscopic plasma fluctuations in the range of the hot electron curvature drift frequency sometimes occur but their growth rate is small (..omega../sub i//..omega../sub r/ less than or equal to 10/sup -2/) and saturate at very low level (deltaB//bar B/ less than or equal to 10/sup -3/). Particle drift reversal is predicted to occur for the model pressure profile which best fits the experimental data under the typical operating conditions. No strong instability is observed when the plasma is near the drift reversal parameter regime, despite a theoretical prediction of instability under such conditions. The experiment shows that the cold electron population has no stabilizing effect to the hot electrons, which disagrees with current hot electron stability theories and results of previous maximum-B experiments. A theoretical analysis using MHD theory shows that the compressibility can stabilize a plasma with a hollowness of 20--30% in the Constance B mirror well. 57 refs.

• Research Organization: Massachusetts Inst. of Tech., Cambridge (USA). Plasma Fusion Center
• DOE Contract Number: AC02-78ET51013
• OSTI ID: 6988788
• Report Number(s): DOE/ET/51013-250; PFC/RR-88-6; ON: DE88013935
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700107* -- Fusion Energy-- Plasma Research-- Instabilities
CHEMICAL ANALYSIS
CLOSED CONFIGURATIONS
CONFINEMENT
DATA ACQUISITION SYSTEMS
ECR HEATING
ELECTRON TEMPERATURE
EQUILIBRIUM
EQUILIBRIUM PLASMA
FLUCTUATIONS
HEATING
HIGH-FREQUENCY HEATING
HOT PLASMA
INSTABILITY
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELDS
MAGNETIC PROBES
MHD EQUILIBRIUM
MINIMUM AVERAGE-B CONFIGURATIONS
NONDESTRUCTIVE ANALYSIS
PLASMA
PLASMA CONFINEMENT
PLASMA DIAGNOSTICS
PLASMA HEATING
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA PRESSURE
PROBES
STABILITY
VARIATIONS
X-RAY EMISSION ANALYSIS