In order to investigate the formation of toroidal flow in helical systems, both NBI driven flow and spontaneous toroidal flow were observed in Large Helical Device (LHD). The toroidal flow driven by NBI is dominant in plasma core while its contribution is small near plasma edge. The spontaneous toroidal flow changes its direction from co to counter when the radial electric field is changed from negative to positive at plasma edge. The direction of the spontaneous toroidal flow due to the radial electric field near plasma edge is observed to be opposite to that in plasma core where the helical ripple is small

Katsumi IDA

Kenichi NAGAOKA

LHD Experimental Group the

Masaki OSAKABE

Masayuki YOKOYAMA

Mikirou YOSHINUMA

In order to investigate the formation of toroidal flow in helical systems, both NBI driven flow and spontaneous toroidal flow were observed in Large Helical Device (LHD). The toroidal flow driven by NBI is dominant in plasma core while its contribution is small near plasma edge. The spontaneous toroidal flow changes its direction from co to counter when the radial electric field is changed from negative to positive at plasma edge. The direction of the spontaneous toroidal flow due to the radial electric field near plasma edge is observed to be opposite to that in plasma core where the helical ripple is small.journal articl

YOSHINUMA,  Mikirou

IDA,  Katsumi

YOKOYAMA,  Masayuki

NAGAOKA,  Kenichi

OSAKABE,  Masaki

the, LHD Experimental Group

NIFS-Repository (National Institute for Fusion Science)

Charge exchange spectroscopy by Fabry–Pérot spectrometer in W7-ASM. Yoshinuma, K. Ida, and J. Baldzuhn  Citation: Rev. Sci. Instrum. 75, 4136 (2004); doi: 10.1063/1.1789587 View online: http://dx.doi.org/10.1063/1.1789587 View Table of Contents: http://rsi.aip.org/resource/1/RSINAK/v75/i10 Published by the American Institute of Physics.  Related ArticlesIon pseudoheating by low-frequency Alfvén waves revisited Phys. Plasmas 20, 012121 (2013) Neutral beam heating of a RFP plasma in MST Phys. Plasmas 19, 122505 (2012) The effects of neutral gas heating on H mode transition and maintenance currents in a 13.56MHz planar coilinductively coupled plasma reactor Phys. Plasmas 19, 093501 (2012) Collisionless inter-species energy transfer and turbulent heating in drift wave turbulence Phys. Plasmas 19, 082309 (2012) Development of a low-energy and high-current pulsed neutral beam injector with a washer-gun plasma source forhigh-beta plasma experiments Rev. Sci. Instrum. 83, 083504 (2012)  Additional information on Rev. Sci. Instrum.Journal Homepage: http://rsi.aip.org Journal Information: http://rsi.aip.org/about/about_the_journal Top downloads: http://rsi.aip.org/features/most_downloaded Information for Authors: http://rsi.aip.org/authors Downloaded 04 Feb 2013 to 133.75.110.124. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/about/rights_and_permissionsCharge exchange spectroscopy by Fabry–Pérot spectrometer in W7-ASM. Yoshinumaa) and K. IdaNational Institute for Fusion Science, Toki 509-5292, JapanJ. BaldzuhnMaxPlank Institute for Plasma Physics, Wendelsteinstrasse, 1, 17491 Greifswald, Germany(Presented on 21 April 2004; published 13 October 2004)Charge exchange spectroscopy using a Fabry–Pérot spectrometer has been developed to study thedynamic of ion temperature and radial electric field in plasmas. A charge coupled device detecterwith 80380 pixels was used to gain the spectral resolution of the charge exchange spectroscopysystem. This Fabry–Pérot charge exchange spectroscopy system has been applied to measure the iontemperature using the charge exchange line of carbon impurity with a time resolution of 5 ms forhigh density quasisteady discharges in W7-AS. The cold component due to the charge exchangereaction between the carbon impurity and thermal neutrals is subtracted from the change emissionwith the beam modulation technique © 2004 American Institute of Physics.[DOI: 10.1063/1.1789587]I. INTRODUCTIONCharge exchange spectroscopy (CXS) has been used tomeasure the profile of ion temperature and plasma rotationvelocity in both the poloidal and toroidal direction in toka-mak and helical plasmas.1,2 An improvement of time resolu-tion of the CXS has been desired eagerly as going to studythe dynamic behaviors of radial electric field in the plasmawhere the radial electric field changes rapidly at the transi-tion to the confinement improved mode or in the breathingphase. Since the background emissions from the charge ex-change with the thermal neutrals around the peripheral of theplasma overlaps the charge exchange emission to be mea-sured, the background emission should be subtracted fromthe change exchange emission to derive local ion tempera-ture. The beam modulation is one of the techniques to sub-tract the background emission. The improvement of the timeresolution is also useful for the CXS measurement with thebeam modulation. A Fabry–Pérot spectrometer has goodspectral resolution, therefor the aperture for input light canbe larger compared with the slit of a conventional spectrom-eter. Charge exchange spectroscopy using a Fabry–Pérotspectrometer was developed and installed in the JIPP TII-Utokamak. The spectral resolution was limited by the numberof two dimensional (2D) photodiodes of the ditector.3 The2D photodiodes array was replaced with the charge coupleddevice (CCD) image detector to improve the spectralresolution.II. CXS SYSTEM BY FABRY–PÉROT SPECTROMETERFigure 1 shows the schematic view of the CXS systemusing Fabry-Pérot spectrometer. The system consists of anétalon with a spacing of 75 mm, two optical lenses, one in-terference filter, CCD image detector, and a bundle of sevenoptical fibers that are arranged on an optical axis. The étalonhas 1.7 nm of free spectrum range (FSR) which is largeenough to measure the Doppler broadened spectrum for theplasma with the ion temperature of 1 keV. The center wave-length and bandwidth of the interference filter are 529.1 and1.5 nm, which is narrower than the FSR of the étalon to cutthe interference of the higher order of spectrum, respectively.The carbon impurity line sC VI l=529.1 nmd is used for theCXS measurement. Two optical lenses are arranged at eachside of the étalon. The wavelength l transmitting the étalonwith the finite angle ud are given byld = l0 cos ud = l0sf/˛f2 + d2d , s1dwhere d , f ,ud, and l0 are the distance from the optical axis,the focal length of the coupled lens, light injection angle intothe étalon against the optical axis, and center wavelengthtransmiting the étalon along the optical axis. The system hassix channels for measurement (Nos. 1–6 in Fig. 1) and onechannel for calibration (No. 0 in Fig. 1) of center wave-length. The CCD detector is arranged at the focal plane ofthe lense opposite the fiber bundle. The back illuminationCCD detector with 80380 pixels (36 mm pixel size) is usedto increase quantum efficiency. The image of the aperture ofthe fiber bundle is focused on the CCD detector. The wave-length for each pixel is calculated from the distance of thepixel position from the optical axis by using formula (1).III. CALIBRATIONS OF FABRY–PÉROT SYSTEMFigure 2 shows the spectra of the Sm and Cu lampsmeasured with the Czerny–Turner type spectrometer, whichis already calibrated and the Fabry–Pérot system. Becausethe range of the wavelength of the Fabry–Pérot system,which is limited by a diameter of the optical fiber, is 0.8 nmthe center wavelength of the étalon is tuned at 528.8 and529.75 nm for Sm line and 529.75 and 530.45 nm for Culine. The wavelengths in Fig. 2(b) are calculated with for-mula (1). The center wavelength of the étalon is calibrateda)Electronic mail: yoshinuma@nifs.ac.jpREVIEW OF SCIENTIFIC INSTRUMENTS VOLUME 75, NUMBER 10 OCTOBER 20040034-6748/2004/75(10)/4136/3/$22.00 4136 © 2004 American Institute of PhysicsDownloaded 04 Feb 2013 to 133.75.110.124. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/about/rights_and_permissionsby using the peak at 528.291 nm of the Sm lamp and at529.25 nm of the Cu lamp. The spectrum, which was ob-served with the Czerny–Turner type spectrometer is almostidentical to that observed with the Fabry–Pérot system.Figures 3(a) and 3(b) show the spectrum of the Cu lamps529.25 nmd without and with the intensity calibration, re-spectively. The intensity decreases as the distance from theoptical axis is increased (away from the CCD center) as seenin Fig. 3(a). The light intensity at the center region of theimage is higher than that at the outer region of the imagebecause the effective aperture of the étalon for the outer re-gion of the image is decreased. Furthermore the sensitivity ofpixels of the CCD are scattered slightly. The profile of thephotons throughput are measured by injecting the white light(halogen lamp) uniformly and is used for the intensity cali-bration. Figure 3(b) shows the spectra after the intensity iscorrected with the calibration of throughput. The scatteringsof the data are also corrected by the intensity calibrations andthe x2 value of the fitting with Gaussian curve decreases to1/3 compared with the data without the calibration.Because the dispersion of the Fabry–Pérot system is notlinear on d, the width of the spectra at the position is largerthan that at the outer position. Figure 3(c) shows the spec-trum of the Cu lamp s529.25 nmd polotted on the axis of thewavelength. The spectra measured at different d overlap eachother. The instrumental width from full width half maximum(FWHM) of the spectrum is 0.065 nm. The wavelength reso-lution of the data points is about 0.0015 nm, which is muchsmaller than the instrumental width of the Fabry–Pérot spec-trometer. The resolution of the Fabry–Pérot system is limitedby the instrumental width. The instrumental width of0.065 nm corresponds to 0.03 keV in the Doppler width ofcarbon impurity, which is much smaller than the target tem-perature of 1 keV. The effective finesse (FSR/FWHM)FIG. 1. Schematic view of the Fabry–Pérot CXS system.FIG. 2. Spectra of the Cu and Sm lamp measured by using the: (a) Czerny–Turner type spectrometer and (b) Fabry–Pérot spectrometer. Dotted line in-dicates the characteristic curve of the interference filter used for the Fabry–Pérot spectrometer. The arrow in (a) indicates the wavelength of the C VIline without Doppler shift. The arrow in (b) indicates the range of wave-length acquired with a fixed space of Fabry–Pérot interferometer.FIG. 3. Spectra of Cu s529.25 nmd measured at the inner (circle), middle(triangle), and outer (square) region of CCD image: (a) without intensitycalibration, (b) without intensity calibration, and (c) with intensity calibra-tion plotted on wavelength axis.Rev. Sci. Instrum., Vol. 75, No. 10, October 2004 Plasma diagnostics 4137Downloaded 04 Feb 2013 to 133.75.110.124. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/about/rights_and_permissionswhich indicates the performance of a Fabry–Pérot system is26, while the Fabry–Pérot system installed in JIPP TII-U in19953 was only 14.IV. CXS MEASUREMENT IN W7-ASThe Fabry–Pérot system are installed in W7-AS with sixline of sights which cross the neutral beam of the radialneutral beam injector (RNBI). The charge exchange line ofcarbon impurity is measured with a time resolution of 5 mswith exposure time 3.5 ms for high-density quasisteady dis-charge. The line averaged density is 3.731020 m−3 and thetotal heating power of the neutral beam is 3.5 MW.Figure 4 shows the time evolution of C VI intensity andthe total power of the RNBI. The C VI intensity is modulatedwith 50 Hz associated with the modulation of the radial in-jector of the neutral beam (10 ms on, 10 ms off). The inten-sity of the charge exchange line due to the beam is compa-rable to the intensity induced by charge exchange reactionbetween carbon and thermal neutrals (background).Figure 5 shows the charge exchange spectrum of C VI atthe timing of beam on (at 0.262 s) and beam off (at 0.267 s).The difference between the spectra at beam on and beam offgives C VI emission emitted from the cross section betweenline of sight and the neutral beam line. The ion temperaturederived from the Doppler width after subtracting the back-ground is 350 eV.ACKNOWLEDGMENTSThe authors would like to thank the W7-AS team fortheir support of this work. This work is supported by a grant-in-aid for scientific research from MEXT, Japan.1 K. Ida, S. Kado, and Y. Liang, Rev. Sci. Instrum. 71, 2360 (2000).2 J. Baldzuhn, W. Ohlendorf, and the W7-As-Team, Rev. Sci. Instrum. 68,1020 (1997).3 K. Ida, Fusion Eng. Des. 34–35, 219 (1997).FIG. 4. Time evolution of signal intensity (circle) plotted with the totalpower of RNBI (solid line).FIG. 5. Spectra of the charge exchange line of C VI with the RNBI on (opensquare), off (open triangle), and the beam induced component (open circle).Solid lines the curve of fitting with Gaussian profile.4138 Rev. Sci. Instrum., Vol. 75, No. 10, October 2004 Yoshinuma, Ida, and BaldzuhnDownloaded 04 Feb 2013 to 133.75.110.124. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/about/rights_and_permissions

Observation of Toroidal Flow on LHD

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Observation of Toroidal Flow on LHD

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