Measurements of neutral helium density in helicon plasmas

Journal Article · Fri Oct 15 04:00:00 EDT 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3466796· OSTI ID:22055796

Houshmandyar, Saeid; Sears, Stephanie H; Thakur, Saikat Chakraborty; Carr, Jerry Jr; Galante, Matthew E; Scime, Earl E ^[1]

---

1. Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

Laser-induced-fluorescence (LIF) is used to measure the density of helium atoms in a helicon plasma source. For a pump wavelength of 587.725 nm (vacuum) and laser injection along the magnetic field, the LIF signal exhibits a signal decrease at the Doppler shifted central wavelength. The drop in signal results from the finite optical depth of the plasma and the magnitude of the decrease is proportional to the density of excited state neutral atoms. Using Langmuir probe measurements of plasma density and electron temperature and a collisional-radiative model, the absolute ground state neutral density is calculated from the optical depth measurements. Optimal plasma performance, i.e., the largest neutral depletion on the axis of the system, is observed for antenna frequencies of 13.0 and 13.5 MHz and magnetic field strengths of 550-600 G.

• OSTI ID: 22055796
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 10 Vol. 81; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
BEAM INJECTION
DOPPLER EFFECT
ELECTRON TEMPERATURE
EXCITED STATES
FLUORESCENCE
GROUND STATES
HELIUM
LANGMUIR PROBE
LASERS
MAGNETIC FIELDS
MHZ RANGE
PLASMA
PLASMA DENSITY
SIGNALS
WAVELENGTHS