Electron-cyclotron heating in the Constance 2 mirror experiment
Electron cyclotron heating of a highly-ionized plasma in mirror geometry is investigated. The experimental diagnosis of the electron energy distribution and the comparison of the results of this diagnosis with a two dimensional, time-dependent Fokker-Planck simulation are accomplished in four steps. (1) First, the power balance of the heated and unheated Constance 2 plasma is analyzed experimentally. It is concluded that the heated electrons escape the mirror at a rate dominated by a combination of the influx of cool electrons from outside the mirror and the increased loss rate of the ions. (2) The microwave parameters at the resonance zones are then calculated by cold-plasma ray tracing. High N/sub parallel/ waves are launched and for these waves, strong first-pass absorption is predicted. The absorption strength is qualitatively checked in the experiment by surrounding the plasma with non-reflecting liners. (3) A simplified quasilinear theory including the effect of N/sub parallel/ is developed to model the electrons. An analytic expression is derived for the RF-induced pump-out of the magnetically-confined warm electrons. Results of the Fokker-Planck simulations show the development of the electron energy distribution for several plasma conditions and verify the scaling of the analytic expression for RF-induced diffusion into the loss cone. (4) Sample x-ray and endloss data are presented, and the overall comparison between the simulation and experiment is discussed. The x-ray signals indicate that, for greater RF power, the hot electrondensity increases more rapidly than its temperature. The time history of the endloss data, illustrating RF-enhancement, suggests the predicted scaling for warm-electron pump-out. Finally, a comparison between the measured and predicted energy distribution shows that the bulk, warm and hot components of the heated Constance 2 electrons are indeed reproduced by the simulation.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge (United States). Plasma Fusion Center
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 6696216
- Report Number(s):
- DOE/ET/51013-58; ON: DE83001003; TRN: 82-026713
- Resource Relation:
- Other Information: Thesis. Portions of document are illegible
- Country of Publication:
- United States
- Language:
- English
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ECR HEATING
ANALYTICAL SOLUTION
MAGNETIC MIRROR CONFIGURATIONS
ELECTRON DENSITY
ENERGY BALANCE
FOKKER-PLANCK EQUATION
MICROWAVE RADIATION
X-RAY SPECTRA
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
EQUATIONS
HEATING
HIGH-FREQUENCY HEATING
MAGNETIC FIELD CONFIGURATIONS
OPEN CONFIGURATIONS
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA HEATING
RADIATIONS
SPECTRA
700101* - Fusion Energy- Plasma Research- Confinement
Heating
& Production