MEASUREMENTS OF ELECTRON DENSITIES AND TEMPERATURES AND OTHER PLASMA PARAMETERS IN MAGNETIC COMPRESSION EXPERIMENTS

Journal Article · Mon Jan 01 00:00:00 EST 1962 · Nucl. Fusion, Suppl.

OSTI ID:4718000

Griem, H R; Kolb, A C; Lupton, W H; Phillips, D T

A high energy plasma is produced in preionized deuterium (0.1 mm Hg) that has been preheated with an electrodeless discharge to 1.0 ev by a current pulse through a single-turn coil (length 70 cm, inner diameter 5.7 cm, mirror ratio 2 : 1, peak current 5.5 MA, H/sub max/80 kG in 5 mu s, coil voltage 9 kV, bank voitage 17 kV). Time-resolved measurements of the soft x-ray intensities transmitted by various absorber foils yield an electron temperature which rises rapidly from 1 kev at 3 mu s to 2.5 kev at peak current and persists at this level through most of the first halfcycle. This electron temperature is higher than the temperature expected from shock heating and adiabatic compression by a factor of approximates 3 to 6. The additional heating is due to the dissipation of an initially trapped reverse field of 6 kG opposite in direction to the main confining field. From the visible bremsstrahlung follows an electron density of 7 plus or minus 2 x 10/sup 18/ cm/sup -3/ at the time of maximum current, indicating a high BETA . Streak camera observations show that the plasma is macroscopically stable through most of the first half-cycle of the discharge and that end losses are small. Towards the end of the first half-cycle, the plasma splits into two filaments rotating around each other, and the end losses increase sharply. For the first 2 mu s the radial electron density distribution has a minimum on the axis, due to some remaining trapped (reserve) field. The upper limit for impurities during the first half-cycle is about l% since within the experimental error no excessive x-ray radiation could be observed, and otherwise rapid radiation cooling would dominate the electron temperature. (During the second half-cycle the electron temperature stays below 300 ev.) Similar experiments (PHAROS) with a larger plasma volume (length 180 cm, bore 9.6 cm, mirror ratio 2: 1) and comparable fields (80 kG at 11.5 MA in 10 mu s) yield electron temperatures of 350 plus or minus 50 ev, which is lower than before, possibly because of the longer times required for the reverse field to dissipate with a larger plasma diameter. However, the impurity concentration is not yet known and this could account for the difference. (auth)

• Research Organization: Naval Research Lab., Washington, D.C.
• NSA Number: NSA-17-009734
• OSTI ID: 4718000
• Journal Information: Nucl. Fusion, Suppl., Other Information: Orig. Receipt Date: 31-DEC-63
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

PHYSICS
ABSORPTION
ADIABATIC PROCESSES
BREMSSTRAHLUNG
CAMERAS
CAPACITORS
COILS
CONFIGURATION
CONFINEMENT
COOLING
CURRENTS
DENSITY
DEUTERIUM
DISTRIBUTION
ELECTRIC DISCHARGES
ELECTRIC POTENTIAL
ELECTRONS
ERRORS
FOILS
GASES
HEATING
IMPURITIES
IONIZATION
LIGHT
LOSSES
MAGNETIC COMPRESSION
MAGNETIC FIELDS
MAGNETIC MIRRORS
MEASURED VALUES
PHOTOGRAPHY
PLASMA
PRESSURE
PULSES
ROTATION
SCHLIEREN
SHOCK WAVES
STABILITY
TEMPERATURE
THERMODYNAMICS
VARIATIONS
VOLUME
X RADIATION