NDLI: Studies of short-waveturbulence in ECR heated plasma of the L-2M stellarator

Content Provider	IEEE Xplore Digital Library
Author	Skvortsova, N.N. Batanov, G.M. Kolik, L.V. Petrov, A.E. Phenichnikov, A.A. Sarksyan, K.A. Kharchev, N.K.
Copyright Year	2008
Description	Author affiliation: Gen. Phys. Inst., Moscow (Skvortsova, N.N.; Batanov, G.M.; Kolik, L.V.; Petrov, A.E.; Phenichnikov, A.A.; Sarksyan, K.A.; Kharchev, N.K.)
Abstract	In an attempt to explain anomalous transport in toroidal confinement systems, recent attention has been focused on short-wave turbulence associated with ETG (electron-temperature gradient driven drift waves) instability. Shortwave turbulence was observed in the L-2M and LHD stellarator by using scattering of gyrotron radiation at the operating frequency and at its second harmonics. The excitation of short-wave turbulence $(kv_{Te}/omega_{e}~0.3-0.4)$ in plasma of the FT-2 tokamak was studied by using enhanced scattering diagnostic. The report presents results of studies of characteristics of short-wave turbulence measured from the scattering spectra of gyrotron radiation at the second harmonic of operating frequency (according to the Bragg relation, we have kap40 $cm^{-1};$ $kv_{Te}/omega_{e}ap0.2),$ whereas long-wave plasma fluctuations measured from small-angle scattering of gyrotron radiation at the operating frequency (kap1-1.5 $cm^{-1},$ $kv_{Ti}/omega_{i}ap0.1).$ Measurements were carried out at ECRH powers of 100 and 200 kW. The Fourier spectra of scattered radiation in both cases are continuous spectra with exponentially decreasing intensity in the frequency range from 5 kHz to 1 MHz and with feebly marked wide bands. As the ECRH power was doubled, the noise spectral density increased by a factor of 1.5-2 throughout the measured spectra. Under these heating conditions, the electron temperature in the core plasma increased by a factor of 1.5. When the sector limiter was introduced into the plasma to a depth of 2 cm, the electron temperature was lower by a factor of about 1.5; at the same time, the noise spectral density increased by a factor of 1.5-2 in the frequency range 10-150 kHz for both kap40 $cm^{-1}$ and kap1-1.5 $cm^{-1}.$ In the scattering spectra of fluctuations with kap40 $cm^{-1}$ in the region r/a = 0.3-0.4, an increase in the intensities of spectral bands standing out against a background of continuum was more in evidence than in the spectra measured in the region r/a = 0.5-0.6. Estimates show that the conditions for an onset of ETG instability are satisfied in L- 2M plasma at r/a= 0.3-0.6. It may be assumed that a correlation between values of the electron temperature and spectral intensity of short-wave turbulence, observed under different discharge conditions (ECRH power, plasma-wall interaction), is some evidence of interrelation between transport processes and short-wave turbulence.
Starting Page	1
Ending Page	1
File Size	64061
Page Count	1
File Format	PDF
ISBN	9781424419296
ISSN	07309244
DOI	10.1109/PLASMA.2008.4591014
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2008-06-15
Publisher Place	Germany
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Plasmas Plasma temperature Frequency measurement Scattering Plasma measurements Physics Gyrotrons
Content Type	Text
Resource Type	Article
Subject	Atomic and Molecular Physics, and Optics Condensed Matter Physics Electrical and Electronic Engineering

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