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

Abstract

A technique for probing velocity space correlations has been developed using laser-induced 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 3 m long and radius ∼ 0.25 cm, holding singly-charged argon ions (Ar II) with density n ∼ 109 cm−3, Te ∼ 5 eV, Ti,|| ∼ .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.

A Lagrangian model for laser-induced fluorescence and its application to measurements of plasma ion temperature and electrostatic waves

“…The IVDF is obtained by scanning the laser wavelength 18 . Ideally, the full width at half maximum (FWHM) of the IVDF for a Maxwellian plasma is given by 9…”

Laboratory space physics: Investigating the physics of space plasmas in the laboratory

“…For example, laser induced fluorescence (LIF) is a sophisticated means of making spatially resolved measurements of ion velocity distributions in the laboratory. [440][441][442][443][444][445][446][447][448][449][450] Several studies have compared the performance of retarding field energy analyzers to that of LIF systems in measuring ion velocity distributions. 451,452 Note, however, that because LIF depends on the existence of suitable atomic emission lines, it cannot be used to probe the velocities of protons (in ionized hydrogen plasmas) or electrons.…”

The finite probe size effect in fluctuation measurements; application to dusty plasmas

“…2011), quasi-thermal noise spectroscopy (Meyer-Vernet & Perche 1989) or laser-induced fluorescence (Mattingly et al. 2013). Fluctuation measurements by probes have been carried out in various plasma environments, ranging from quiescent laboratory plasmas where thermal fluctuations can be studied (Geissler, Greenwald & Calvert 1972) to plasma mode investigations in dedicated devices and electrostatic low-frequency turbulence in magnetized plasmas and tokamaks (Beall, Kim & Powers 1982; Zweben, Liewer & Couldl 1982; Demidov, Ratynskaia & Rypdal 2002; Ratynskaia, Demidov & Rypdal 2002).…”