Measurements on injected impurity transport in TEXT (Texas Experimental Tokamak) using multiply filtered soft x-ray detectors
Aluminum was injected into TEXT to study trace, non-recycling impurity transport. A 92-channel, three array x-ray imaging system was constructed and installed to measure temporally-resolved density profiles of the three highest charge states. A novel krypton filter in one array discriminated between the He-like and H-like resonance lines, and a hard filter responded mostly to the fully stripped charge state. The impurity confinement time scaled approximately as {tau}{sub c} {approximately} {bar n}{sub e}Z{sub eff}{radical}m{sub i}/Z{sub i}/Ip (i denotes the background gas). Aluminum density profiles averaged over a sawtooth crashes were also measured for a few discharges. Sawteeth strongly enhanced the inward impurity flow immediately following injection, when the density was still peaked near the plasma edge. Those discharges with the longest sawtooth period obtained the most peaked aluminum density profiles; thus sawteeth were also important in ameliorating impurity accumulation on the tokamak axis. The charge state balance of the aluminum ions obtained from the measured profiles was compared to predictions of coronal equilibrium. Somewhat surprisingly the aluminum ions were close to coronal, except in those discharges with very short sawtooth periods or very large inversion radii. Preliminary evidence of up-down asymmetric density profiles was also found. Numerical simulations of aluminum transport were performed. The effect of sawtooth oscillations was taken into account with a simple flattening model. The data disagreed with a constant D anomalous model except in the plasma center; enhanced outward transport was required. The experiments did not agree with neoclassical simulations, because the theory had outward convection that was too large. 237 refs., 86 figs., 8 tabs.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge, MA (USA). Plasma Fusion Center
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- AC02-78ET51013
- OSTI ID:
- 7252563
- Report Number(s):
- DOE/ET/51013-278; PFC/RR-90-1; ON: DE90007638; TRN: 90-007290
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IMPURITIES
NEOCLASSICAL TRANSPORT THEORY
ALUMINIUM
BREMSSTRAHLUNG
CONFINEMENT TIME
TEXT DEVICES
X-RAY DETECTION
CLOSED PLASMA DEVICES
DETECTION
ELECTROMAGNETIC RADIATION
ELEMENTS
METALS
RADIATION DETECTION
RADIATIONS
THERMONUCLEAR DEVICES
TOKAMAK DEVICES
TRANSPORT THEORY
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