Refueling and density control in the ZT-40M reversed field pinch

Conference · Thu Jan 01 04:00:00 EST 1987

OSTI ID:5929470

Wurden, G A; Weber, P G; Watt, R G; Munson, C P; Cayton, T E; Buechl, K

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 Lab., NM (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 5929470
• Report Number(s): LA-UR-87-2985; CONF-870908-8; ON: DE88000504
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
700205* -- Fusion Power Plant Technology-- Fuel
Heating
& Injection Systems
ABLATION
COMPUTERIZED SIMULATION
DEUTERIUM
ELECTRON TEMPERATURE
ELEMENTS
FIRST WALL
FUELS
HYDROGEN
HYDROGEN ISOTOPES
ION TEMPERATURE
ISOTOPES
LIGHT NUCLEI
NONMETALS
NUCLEI
ODD-ODD NUCLEI
PELLET INJECTION
PINCH EFFECT
PLASMA DENSITY
REVERSE-FIELD PINCH
SIMULATION
STABLE ISOTOPES
THERMONUCLEAR FUELS
THERMONUCLEAR REACTOR WALLS