Density fluctuations measured by a mm-wave collective scattering in helicon plasmas

Kwak, J.G.; Wang, S. J.; Kim, S. K.; Cho, Suwon

doi:10.1063/1.2234287

Cited by 4 publications

(5 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Recent experiments in helicon plasma sources have employed collective scattering diagnostics in the microwave to millimeter wavelength ranges. 1,2 Using enhanced backscattering of microwaves at the upper hybrid resonance layer, ion-acousticlike waves were observed by Altukhov et al Ion-acoustic waves were also observed with a 140 GHz millimeter-wave based scattering diagnostic by Kwak et al, similar to the system described here. Interferometers employing millimeter-wave sources have been installed on experiments ranging from a fusion class device 3 ͑DIII-D͒ to a low temperature helicon plasma.…”

Section: Introductionsupporting

confidence: 54%

See 2 more Smart Citations

A 300GHz collective scattering diagnostic for low temperature plasmas

Hardin

Scime

Heard

2008

Review of Scientific Instruments

View full text Add to dashboard Cite

A compact and portable 300 GHz collective scattering diagnostic employing a homodyne detection scheme has been constructed and installed on the hot helicon experiment (HELIX). Verification of the homodyne detection scheme was accomplished with a rotating grooved aluminum wheel to Doppler shift the interaction beam. The HELIX chamber geometry and collection optics allow measurement of scattering angles ranging from 60 degrees to 90 degrees. Artificially driven ion-acoustic waves are also being investigated as a proof-of-principle test for the diagnostic system.

show abstract

Section: Introductionsupporting

confidence: 54%

“…Thus all optical components, except the vacuum collection mirror, fit on a 36 by 36 in. 2 the four 6 in. ports.…”

Section: Ghz Diagnostic Descriptionmentioning

confidence: 99%

See 1 more Smart Citation

A 300GHz collective scattering diagnostic for low temperature plasmas

Hardin

Scime

Heard

2008

Review of Scientific Instruments

View full text Add to dashboard Cite

show abstract

“…Laser induced fluorescence (LIF) is routinely employed in helicon [16][17][18] plasma sources to measure Doppler resolved velocity distribution functions (VDF) of argon ions, argon neutrals, helium neutrals, and xenon ions. [19][20][21] The full width at half maxima of the VDF represents the average temperature of the distribution and the shift of the peak of the distribution from a standard reference line gives the ion fluid velocity.…”

Section: Introductionmentioning

confidence: 99%

Laser induced fluorescence measurements of ion velocity and temperature of drift turbulence driven sheared plasma flow in a linear helicon plasma device

et al. 2012

View full text Add to dashboard Cite

Using laser induced fluorescence (LIF), radial profiles of azimuthal ion fluid velocity and ion temperature are measured in the controlled shear de-correlation experiment (CSDX) linear helicon plasma device. Ion velocities and temperatures are derived from the measured Doppler broadened velocity distribution functions of argon ions. The LIF system employs a portable, high power (>300 mW), narrowband (∼1 MHz) tunable diode laser-based system operating at 668.614 nm. Previous studies in CSDX have shown the existence of a radially sheared azimuthal flow as measured with time delay estimation methods and Mach probes. Here, we report the first LIF measurements of sheared plasma fluid flow in CSDX. Above a critical magnetic field, the ion fluid flow profile evolves from radially uniform to peaked on axis with a distinct reversed flow region at the boundary, indicating the development of a sheared azimuthal flow. Simultaneously, the ion temperature also evolves from a radially uniform profile to a profile with a gradient. Measurements in turbulent and coherent drift wave mode dominated plasmas are compared.

show abstract

“…Although it is possible to extract some details about the electron EDF from a Langmuir probe current versus voltage sweep, 8 the details of the ion EDF are much harder to extract from Langmuir probe measurements; neutral EDFs cannot be measured with a Langmuir probe; and any flows in the plasma make the interpretation of the electron EDF particularly problematic. 9 LIF is routinely employed in helicon [10][11][12] and other plasma sources to measure velocity distributions of argon ions, argon neutrals, helium neutrals, and xenon ions. [13][14][15] LIF is an effective and versatile technique as long as sufficiently large populations of the target species initial state are available.…”

Section: Introductionmentioning

confidence: 99%

Continuous wave cavity ring down spectroscopy measurements of velocity distribution functions of argon ions in a helicon plasma

Thakur

McCarren

Carr

et al. 2012

Review of Scientific Instruments

View full text Add to dashboard Cite

We report continuous wave cavity ring down spectroscopy (CW-CRDS) measurements of ion velocity distribution functions (VDFs) in low pressure argon helicon plasma (magnetic field strength of 600 G, T(e) ≈ 4 eV and n ≈ 5 × 10(11) cm(-3)). Laser induced fluorescence (LIF) is routinely used to measure VDFs of argon ions, argon neutrals, helium neutrals, and xenon ions in helicon sources. Here, we describe a CW-CRDS diagnostic based on a narrow line width, tunable diode laser as an alternative technique to measure VDFs in similar regimes but where LIF is inapplicable. Being an ultra-sensitive, cavity enhanced absorption spectroscopic technique; CW-CRDS can also provide a direct quantitative measurement of the absolute metastable state density. The proof of principle CW-CRDS measurements presented here are of the Doppler broadened absorption spectrum of Ar II at 668.6138 nm. Extrapolating from these initial measurements, it is expected that this diagnostic is suitable for neutrals and ions in plasmas ranging in density from 1 × 10(9) cm(-3) to 1 × 10(13) cm(-3) and target species temperatures less than 20 eV.

show abstract

Density fluctuations measured by a mm-wave collective scattering in helicon plasmas

Cited by 4 publications

References 16 publications

A 300GHz collective scattering diagnostic for low temperature plasmas

A 300GHz collective scattering diagnostic for low temperature plasmas

Laser induced fluorescence measurements of ion velocity and temperature of drift turbulence driven sheared plasma flow in a linear helicon plasma device

Continuous wave cavity ring down spectroscopy measurements of velocity distribution functions of argon ions in a helicon plasma

Contact Info

Product

Resources

About