Refueling and density control in the ZT-40M reversed field pinch
The effects of pellet injection and gas puff refueling have been studied in the ZT-40M Reversed Field Pinch. Multiple deuterium pellets (less than or equal to 6 x 10/sup 19/D atoms/pellet) with velocities ranging from 300 to 700 m/sec have been injected into plasmas with n-bar/sub e/ approx.1 to 5 X 10/sup 19/m/sup -3/, I/sub phi/ approx.100 to 250 kA, T/sub e/(0) approx.150 to 300 eV and discharge durations of less than or equal to 20 msec. Photographs and an array D/sub ..cap alpha../ detectors show substantial deflection of the pellet trajectory in both the poloidal and toroidal planes, due to asymmetric ablation of the pellet by electrons streaming along field lines. To compensate for the poloidal deflection, the injector was moved up +14 cm off-axis, allowing the pellets to curve down to the midplane. In this fashion, central peaking of the pellet density deposition profile can be obtained. Both electron and ion temperatures fall in response to the density rise, such that ..beta../sub theta/(..beta../sub theta/ identical to n-bar/sub e/(T/sub e/(0) + T/sub i/)/(B/sub theta/(a))/sup 2/) remains roughly constant. Energy confinement is momentarily degraded, and typically a decrease in F (F identical to B/sub phi/(a)/(B/sub phi/)) is seen as magnetic energy is converted to plasma energy when the pellet ablates. As a result of pellet injection at I/sub phi/ = 150 kA we observe T/sub e/(0) ..cap alpha.. n-bar/sub e//sup -.9 +- .1/, while the helicity based resistivity eta/sub k/ transiently varies as n-bar/sub e//sup .7 +- .1/. While the achievement of center-peaked density profiles is possible with pellet injection, gas puffing at rates strong enough to show a 50% increase in n-bar/sub e/ over a period of 10 msec (approx.150 torr-litres/sec) leads to hollow density profiles. The refueling requirements for parameters expected in the next generation RFPs (ZTH, RFX) can be extrapolated from these data using modified tokamak pellet ablation codes.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5929470
- Report Number(s):
- LA-UR-87-2985; CONF-870908-8; ON: DE88000504; TRN: 87-038653
- Resource Relation:
- Conference: Course and workshop on physics of mirrors, reversed field pinches and compact tori, Varenna, Italy, 1 Sep 1987; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
REVERSE-FIELD PINCH
PELLET INJECTION
PLASMA DENSITY
THERMONUCLEAR FUELS
ABLATION
COMPUTERIZED SIMULATION
DEUTERIUM
ELECTRON TEMPERATURE
FIRST WALL
HYDROGEN
ION TEMPERATURE
ELEMENTS
FUELS
HYDROGEN ISOTOPES
ISOTOPES
LIGHT NUCLEI
NONMETALS
NUCLEI
ODD-ODD NUCLEI
PINCH EFFECT
SIMULATION
STABLE ISOTOPES
THERMONUCLEAR REACTOR WALLS
700205* - Fusion Power Plant Technology- Fuel
Heating
& Injection Systems