Measurement and interpretation of the velocity space correlation of a laboratory plasma fluctuation with laser induced fluorescence

• Published in: Journal of instrumentation Vol. 8; no. 11; p. C11015
• Main Authors: Mattingly, S W, Berumen, J, Chu, F, Hood, R, Skiff, F
• Format: Journal Article
• Language: English
• Published: 01.11.2013
• Subjects: Correlation; Density; Fluctuation; Instrumentation; Ion velocity; Laser induced fluorescence; Lasers; Magnetic fields; Velocity distribution
• ISSN: 1748-0221; 1748-0221
• DOI: 10.1088/1748-0221/8/11/C11015

A technique for probing velocity space correlations has been developed using laserinduced fluorescence. In this paper, a description of the experimental setup is given, with results to follow in a later publication. The experiment consists of a cylindrical plasma column 3m long and radius ~ 0.25 cm, holding singly-charged argon ions (Ar II) with density n ~ 10 super(9) cm super(-3), T sub(e) ~ 5 eV, T sub(i,) ~ .06 eV, and a 1 kG axial magnetic field. Two separate metastable lines are excited by single frequency lasers at 611 nm and 668 nm. These lasers may tune with a precision of .01 pm. The separate lasers are used to measure independent slices of the velocity distribution function. To confirm the velocity distribution and magnetic field, the Doppler-broadened, sigma-polarized Zeeman line for each transition is measured. With this, the absolute parallel component of ion velocity subject to LIF can be determined. The two separate lasers then give us a signal as a function of two separate parallel ion velocities. Two point correlation is used to reduce the noise floor on the plasma fluctuation. This fluctuation is then investigated as a function of the difference in velocity.