Dark-ground illumination: a quantitative diagnostic for plasma density
Radial electron density profiles of a toroidal belt pinch plasma have been obtained by a single measurement. Collimated ruby laser light, incident on the plasma, is focused to a diffraction limited spot (100 ..mu..m). The technique, a variation of the dark-ground microscope, involves masking the center of the plasma diffraction pattern with a thin wire. Undiffracted light is blocked by a thin wire, whereas light diffracted by the plasma passes around the wire and onto a photoplate. The resulting interference generates a high contrast fringe pattern whose intensity varies as 1-cos..delta.. phi, where ..delta.. phi is the phase shift induced by the plasma. The fringes are recorded on Polaroid type 46L transparency film. Using this technique, radial density profiles of the plasma produced in the Columbia Torus I belt pinch have been measured. The plasma minor cross section is elliptical with a approx. 2 cm, b approx. 30 cm and approx. 3 x 10/sup 16//cm/sup 3/. Average densities as low as 2 x 10/sup 15//cm/sup 3/ have been measured.
- Research Organization:
- Columbia Univ., New York (USA). School of Engineering and Applied Science
- DOE Contract Number:
- AS02-76ET-53016
- OSTI ID:
- 6144145
- Report Number(s):
- DOE/ET/53016-74; ON: DE82000442; TRN: 81-017776
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BELT PINCH
PLASMA DIAGNOSTICS
LASER RADIATION
ELECTRON DENSITY
PLASMA DENSITY
SCATTERING
TOROIDAL CONFIGURATION
WIRES
ANNULAR SPACE
CONFIGURATION
ELECTROMAGNETIC RADIATION
LONGITUDINAL PINCH
PINCH EFFECT
RADIATIONS
SPACE
700102* - Fusion Energy- Plasma Research- Diagnostics