Observation of Plasma Heating Due to Parametric Instabilities at the Upper Hybrid and at the Cyclotron Harmonic Frequencies

Grek, B.; Porkoláb, M.

doi:10.1103/physrevlett.30.836

Cited by 65 publications

(20 citation statements)

References 9 publications

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“…This indicates that there is a yet to be determined mechanism of the RF absorption that is directly heating ions, including the background He and boron ions. Possible candidates are: fast electromagnetic to slow electrostatic wave mode conversion [19] and excitation of the parametric decay instability of upper and lower hybrid waves [20,21].…”

Section: Discussion and Summarymentioning

confidence: 99%

Study and optimization of boronization in Alcator C-Mod using the Surface Science Station (S3)

Ochoukov

Whyte

Lipschultz

et al. 2012

Fusion Engineering and Design

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A Surface Science Station (S 3 ) on the Alcator C-Mod tokamak is used to study and optimize the location and rate of boron film deposition in-situ during electron cyclotron (EC) discharge plasmas using 2.45 GHz radio-frequency (RF) heating and a mixture of helium and diborane (B 2 D 6 ) gasses. The radial profile of boron deposition is measured with a pair of quartz microbalances (QMB) on S . A maximum boron deposition rate of 0.82 g/cm 2 /min is obtained, which corresponds to 3.5 nm/min if the film density is that of solid boron. These deposition rates are sufficient for boron film applications between tokamak discharges. However the deposition does not peak at the EC resonance as previously assumed. Rather, deposition peaks near the upper hybrid (UH) resonance, ~5 cm outboard of the EC resonance. This has implications for RF absorption, with the RF waves being no longer damped on the electrons at the EC resonance. The previously inferred radial locations of critical erosion zones in Alcator C-Mod also need to be reevaluated. The boron deposition profile versus major radius follows the ion flux/density profile, implying that the boron deposition is primarily ionic. The application of a vertical magnetic field (B V ~0.01 T) was found to narrow the plasma density and boron deposition profiles near the UH resonance, thus better localizing the deposition. A Monte Carlo simulation is developed to model the boron deposition on the different QMB/tokamak surfaces. The model requires a relatively high boron ion gyroradius of ~5 mm, indicating a B +1 ion temperature of ~2 eV, to match the deposition on QMB surfaces with different orientation to B T . Additionally, the boron ion trajectories become de-magnetized at high neutral gas throughput (~0.5 Pa m ) and pressure (~2 Pa) when the largest absolute deposition rates are measured, resulting in deposition patterns, which are independent of surface orientation to B T in optimized conditions.

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Section: Discussion and Summarymentioning

confidence: 99%

Study and optimization of boronization in Alcator C-Mod using the Surface Science Station (S3)

Ochoukov

Whyte

Lipschultz

et al. 2012

Fusion Engineering and Design

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“…Wavelength measurements of the decay waves have shown decay into upper-hybrid waves (Bernstein waves) and lower-hybrid and/or ion acoustic waves. M asurements of thresholds, growth rates, pump depled tion, and anomalous resistivity have been performe (Grek and Porkolab, 1973), in which significant electron heating was associated with the -presence of the decay in -I I I I I IIII I I I I I IIII I I I I I IIII I I I I I I stability. An effective anomalous resistivity of a factor of ten to twenty times larger than classical resistivity has been measured (Grek, 1973).…”

Section: Upper-hybrid Frequencymentioning

confidence: 99%

“…In the regime of the upper-hybrid frequency recent measurements on parametric decay have been performed in both linear geometry (Grek and Porkolab, 1973; Porkolab et a/. , 1976) and toroidal devices (Okabayashi et a/.…”

Section: Upper-hybrid Frequencymentioning

confidence: 99%

Nonlinear wave effects in laboratory plasmas: A comparison between theory and experiment

Porkoláb

Chang²

1978

Rev. Mod. Phys.

Self Cite

124

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The rich nonlinear phenomena that occur in plasmas are reviewed in a systematic way. The foundations of turbulence theory (both weak and strong) and-experiments performed in the past decade to verify such theories are presented. The aim is to emphasize those experiments that demonstrate clearly the validity (or failure) of' some of the theories. In particular, we discuss experiments that demonstrate the validity and/or limits of weak turbulence theory, strong turbulence theory, parametric instabilities, echoes, trapping of particles in large-amplitude waves, and electrostatic ion acoustic shocks. We present concluding remarks in each section regarding the present status of each of these phenomenon. CONTENTSimproving weak-turbulence theory by "renormalization, " namely, orbit diffusion and the concept of "clumps. " In Sec. VI we present results concerning large-amplitude waves and trapping, and in Sec. VII we discuss some experiments on ion acoustic shocks. We have deliberately avoided or discuss only briefly experiments that (in our opinion) are not yet well understood in terms of quantitative comparison with theories (e.g. , nonlinear drift waves, turbulent resistivity experiments, nonlinear tearing modes, magnetic reconnection, etc. ). II. WEAK-TURBULENCE THEORY AND EXP ER IMENTSA. Foundations of weak-turbulence theoryThe first comprehensive theory of plasma turbulence, what we today call "weak-turbulence theory, " was devel-Rev.

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“…Many researchers have developed ion heating systems for fusion and small-scale laboratory experiments. Typically a wave-particle resonance is exploited to directly heat the ions, e.g., ion cyclotron, [13][14][15] lower hybrid, 16 Alfvén, 16 upper hybrid, 17 and ion Bernstein. 18 Ion cyclotron resonant heating is the most common in tokamaks and linear devices.…”

Section: Introductionmentioning

confidence: 99%

Ion heating in the HELIX helicon plasma source

et al. 1999

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Efficient ion heating in a steady-state helicon plasma source is observed with two external loop antennae just above the ion cyclotron frequency. The ion velocity space distribution is measured by laser induced fluorescence in an argon plasma. The measured bulk ion heating is highly anisotropic ͑the perpendicular temperature increase is ten times the parallel temperature increase͒ even though the plasma is moderately collisional. Measurements of the perturbed distribution function with laser induced fluorescence suggest that an electrostatic ion cyclotron wave is launched.

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Observation of Plasma Heating Due to Parametric Instabilities at the Upper Hybrid and at the Cyclotron Harmonic Frequencies

Cited by 65 publications

References 9 publications

Study and optimization of boronization in Alcator C-Mod using the Surface Science Station (S3)

Study and optimization of boronization in Alcator C-Mod using the Surface Science Station (S3)

Nonlinear wave effects in laboratory plasmas: A comparison between theory and experiment

Ion heating in the HELIX helicon plasma source

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