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V. Vershkov NUCLEAR FUSION INSTITUTE OF RUSSIAN RESEARCH CENTRE “KURCHATOV INSTITUTE

RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE”. "Comparison of the confinement of different plasma components and turbulence rotation with [ExB] velosity in OH and ECRH T-10 plasmas". V. Vershkov NUCLEAR FUSION INSTITUTE OF RUSSIAN RESEARCH CENTRE “KURCHATOV INSTITUTE

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V. Vershkov NUCLEAR FUSION INSTITUTE OF RUSSIAN RESEARCH CENTRE “KURCHATOV INSTITUTE

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  1. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” "Comparison of the confinement ofdifferent plasma components and turbulence rotation with [ExB]velosity in OH and ECRH T-10 plasmas" • V. Vershkov • NUCLEAR FUSION INSTITUTE OF RUSSIAN RESEARCH CENTRE “KURCHATOV INSTITUTE • 9th ITPA Transport Physics meeting, St. Petersburg, Russia, October 3-6, 2005

  2. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” • OUTLINE • Comparison of the confinement of the different plasma components in OH and ECRH plasmas • New measurements of the radial electrical field by HIBP and comparison with turbulence rotation

  3. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Schematic comparison of the results for the impurity decay and short gas puffing 1.The time of the approaching the steady state are equal for impurity decay with zero recycling and short gas puffing with 100 % recycling

  4. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Comparison of k+17 decay times with the energy confinement times/1.5 in OH plasma • The K+17 data from 10th IAEA (1984) 200 kA • Energy confinement from Lion EX/P3-01 paper 200 kA, • Both values and density dependence are in agreement

  5. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Comparison of the energy confinement/1.5 with impurity decay and characteristic times of density evolution after short gas puff in ECRH • Good overlapping the values and density dependence for all components • Degradation of confinement in two times in accordance with rise the turbulence level • Question: energy – only heat conduction; • Density and impurity - Diffusion + convection. How they can coincide functionally at al densities?

  6. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” The relative level of the density fluctuation in OH and ECRH The relative level of density fluctuation in ECRH increases in two times with respect to OH in accordance with confinement degradation in “L” mode, practically without dependence on density

  7. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” • Discussion of the physical mechanisms determining the functional dependence of confinement on density • Instead of the question about saturation at high densities, more important – Why confinement rises at low densities? • One reason – The gradual transfer from the dangerous long-wave ITG to less dangerous shorter-wave TEM (see next slide) • In that way the rise up to 0.5 Greenwald is reasonable and the constancy after establishing of the TEM also understandable. • The other important feature is the strong Te/Ti ratio decrease with density rise. As theory predict the confinement should be bad at high Te at low Ne (see second slide)

  8. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Turbulence spectrum variation versus density in OH (top row) and ECRH (bottom row) 1.In both cases low frequency (long-wave) ITG? Gradually substituted for the short-wave TEM? Up to 0.5 Greenwald. This may lead to increase of confinement 2. After establishing of the TEM no confinement rise is expected.

  9. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Variations of Te(0) and Ti(o) with average density in OH and ECR heated discharges • Te(0) measured by ECE and SXR • Ti(0) was measured by NPA analysis and modeling with “ASTRA”, normalized on neutron emission • The ratio is strongest in ECRH case

  10. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” The map of the primary Tl+1 and secondary Tl+2 beams of T-10 HIBP B=2.4 T E=180-250 keV 13 < r < 32 cm

  11. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Double radial pass of potential value in OH and ECRH • Potential well is symmetric • It has negative value in plasma center • It greatly decreases in ECRH phase

  12. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Core potential evolves with Te variations • Potential follows the local Te with lower increment • The characteristic time of the potential evolution is ~ 50 ms, higher than E • ECRH power is deposited closer to the plasma center

  13. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Comparison of rotation velocities of density perturbations with plasma, [ExB] and electron drift waves rotation in OH and ECRH deuterium core plasma 1. In core deuterium plasma both turbulence and EB rotation decrease in ECRH 2. The uncertainties of calculated velocities are determined by the uncertainties in estimations of Er 3. In spite of the scattering the EB rotation seems fit better to  turb 4. More work should be done, especially at different BT

  14. RUSSIAN RESEARCH CENTRE “KURTCHATOV INSTITUTE” Comparison of the turbulence rotation  TURBwith  EBin OH and ECRH helium edge plasma Clear disagreement between two rotations was observed at the outer half of plasma radius *  TURB increases, while  EB decreases in ECRH

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