Analysis of non-thermal electron cyclotron emission during electron cyclotron current drive experiments on the DIII-D tokamak
Non-thermal electron distributions are diagnosed employing a fast scanning Michelson Interferometer capable of viewing the plasma vertically (constant B[sub toroidal]) along a chord at r/a [approximately] .6 terminated by a highly absorptive Macor viewing dump, and horizontally at the midplane. Extraordinary (X) mode and Ordinary (O) mode polarizations of Electron Cyclotron Emission (ECE) in the second to the tenth harmonic of the fundamental electron cyclotron frequency have been collected under a variety of plasma conditions, during high power microwave injection at 60 GHz in the DIII-D Tokamak. Plasma refraction limits the data analysis to frequencies above the fifth harmonic where the data is characterized by a smooth, exponentially decreasing intensity, due to the high degree of harmonic overlap in this frequency range. Analysis of this data has shown the extreme sensitivity of this diagnostic to emission from high pitch angle particles. Results of delta function distribution calculations and distribution function fitting show that for a low density target plasma (central line averaged n[sub e]=0.5x10[sup 13] cm[sup [minus]3]), the emission is dominated by electrons near the trapping boundary ([psi] [approximately] 53[degrees]) at the author's viewing location, with average energies 400keV < [E] < 500 keV during ECH. Under higher plasma target density conditions (central line averaged n[sub e]=1.0x10[sup 13] cm[sup [minus]3]) the population of electrons during ECH contributing to the emission increases in average energy to [E] [approximately] 1.2MeV as a result of the residual electric field induced by the primary transformer. Non-thermal electron densities (n[sub hot])[approximately]1x10[sup 10] cm[sup [minus]3] are estimated during the ECH phases while the post-ECH phase is characterized by a very diffuse (n[sub hot][approximately]5x10[sup 7] cm[sup [minus]3]), energetic ([E] [approximately] 1.5 MeV), population in the trapped region of momentum space.
- Research Organization:
- Maryland Univ., College Park, MD (United States)
- OSTI ID:
- 7070861
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
TOKAMAK DEVICES
ECR HEATING
ELECTRON EMISSION
HARMONIC GENERATION
CYCLOTRON FREQUENCY
ELECTRON SPECTRA
NON-INDUCTIVE CURRENT DRIVE
CLOSED PLASMA DEVICES
EMISSION
FREQUENCY MIXING
HEATING
HIGH-FREQUENCY HEATING
PLASMA HEATING
SPECTRA
THERMONUCLEAR DEVICES
700350* - Plasma Production
Heating
Current Drive
& Interactions- (1992-)