Neutral depletion and the helicon density limit
نویسندگان
چکیده
منابع مشابه
Measurements of neutral helium density in helicon plasmas.
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 propo...
متن کاملObservations of neutral depletion and plasma acceleration in a flowing high-power argon helicon plasma
Neutral depletion effects are observed in a steady-state flowing argon helicon plasma with a magnetic nozzle for high rf input powers up to 3 kW . Noninvasive diagnostics including 105 GHz microwave interferometry and optical spectroscopy with collisional-radiative modeling are used to measure the electron density ne , electron temperature Te , and neutral density nn . A region of weak neutral ...
متن کاملDensity jump in helicon discharges
Helicon discharges characteristically exhibit a sharp jump from low to high density as the radiofrequency (RF) power is raised. This is usually explained by the transition from an inductively coupled plasma (ICP) mode to a helicon mode when the dispersion relation for helicon wave propagation is satisfied at a critical power or magnetic field. Experiments have suggested a different mechanism fo...
متن کاملTwo photon absorption laser induced fluorescence measurements of neutral density in a helicon plasma
We have developed a new diagnostic based on two-photon absorption laser induced fluorescence (TALIF). We use a high intensity (5 MW/cm), narrow bandwidth (0.1 cm ) laser to probe the ground state of neutral hydrogen, deuterium and krypton with spatial resolution better than 0.2 cm, a time resolution of 10 ns, and a measurement cadence of 20 Hz. Here, we describe proof-of-principle measurements ...
متن کاملUpper Limit to Landau Damping in Helicon Discharges
The uncommonly high rf absorption efficiency of helicon discharges has been thought to be caused by Landau damping of helicon waves and the concomitant acceleration of primary electrons. By constructing an energy analyzer that accounts for rf fluctuations in plasma potential, it is shown that Landau-accelerated electrons are too sparse to explain the ionization efficiency. Instead, rf absorptio...
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ژورنال
عنوان ژورنال: Physics of Plasmas
سال: 2013
ISSN: 1070-664X,1089-7674
DOI: 10.1063/1.4849376