1 / 11

Supported by

Supported by. Wave - plasma interactions in the ion cyclotron range of frequencies: theory and experiment in NSTX. Cynthia K. Phillips Princeton Plasma Physics Laboratory for the NSTX Team APS meeting April 2003. ~. ~. B. E.

merle
Télécharger la présentation

Supported by

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Supported by Wave - plasma interactions in the ion cyclotron range of frequencies: theory and experiment in NSTX Cynthia K. Phillips Princeton Plasma Physics Laboratory for the NSTX Team APS meeting April 2003

  2. ~ ~ B E NSTX IS STUDYING HIGH HARMONIC FAST WAVES IN HIGH BETA PLASMAS B0 • HHFW are compressional fast Alfvén waves • ~ k^ VA ~ N WD ~ (6 - 12) WD • plasma beta ~ 4% - 38% • choosew / k// ~ electron thermal speed • strong electron absorption via transit time magnetic pumping and Landau damping : • ion cyclotron damping generally weak, except for energetic ions and low k// • For NSTX, find ki ≥ 1 and  / a << 1 • Since BP ~ BT, 2D magnetic equilibrium effects important x k^

  3. RADIO FREQUENCY (RF) WAVES USED FOR HEATING AND CURRENT DRIVE • ST’s need auxiliary heating (H) and current drive (CD) • choose wave spectra for H or CD • absorption profile depends on plasma parameters • HHFW are absorbed by electrons in high beta plasmas • competitive absorption by ions degrades CD efficiency

  4. POWER SPECTRUM OF ANTENNA IS PROGRAMMABLE OVER A WIDE RANGE OF k|| (~ 2 to ~ 14 m-1) Antenna phasing controls heating or current drive 12 element antenna for 6 MW @ 30 MHz co-CD B counter-CD Heating -20 0 20 antenna extends almost 90° toroidally kz (m-1) 4

  5. 4 1.5 1.2 PRF (MW) 0.6 0 0 0 0.2 1.6 0 0.5 Time (s) HHFW STRONGLY HEATS ELECTRONS • B = 0.44 T • kT = 14 m-1 • ne0 = 4.0 x 1019 m-3 4He Discharge Te > Ti keV Major Radius (m) Note decay of Te after RF turn-off

  6. AORSA-2D full wave code 0.4 0 0.8 CENTRAL ELECTRON HEATING PREDICTED BY THEORETICAL MODELS Full wave code WKB ray tracing codes 3 3 ray tracing codes AORSA - 2D HPRT Pabs ( MW / m3 ) Pabs ( MW / m3 ) CURRAY 0 0 0.4 0.8 0 normalized minor radius normalized minor radius

  7. HHFW HEATS FAST DEUTERIUM IONS INJECTED WITH NEUTRAL BEAMS ne 0 0.2 0.4 0.6 Neutral particle analyzer 2 12 12 108251 2 10 Te0(keV) beam injection energy 8 ln (flux / Energy1/2) 8 1 ln ( flux / energy 1/ 2 ) ne ( 1019 m-3) Ip (MA) at RF end +10 ms +20 ms 6 4 4 RF 2.4 noise level 2 NBI 1.6 MW 0 0 0 40 80 120 Time (s) Energy (keV) • fastD+tail builds up during and decays after HHFW

  8. THEORY PREDICTS SIGNIFICANT ABSORPTION BY FAST IONS Shot 105908 Time 195 ms Pelec = 55% Pbeam= 45% Pabs (MW / m3) 0.4 0.8 0 normalized minor radius • fast ion and electron absorption comparable • no thermal ion absorption for this k// range • fast ion absorption degrades CD efficiency BUT • fast ion absorption decreases at lower BT , higher b • observed and predicted 1 0.6 beam e- 0.2

  9. CURRENT DRIVE INFERRED FROM DIFFERENCES IN LOOP VOLTAGE WITH PHASED WAVES 1.0 0.8 0.6 0.4 0.2 0 0.2 0.3 0.4 0.5 0.6 • 2 discharges with similar ne(r),Te(r) • inductance similar • V not caused by dli/dt • less loop voltage required for constant IP with co-CD phasing Counter - CD DV ≈ .2V Loop Voltage (V) Co - CD RF on Time (s) • circuit analysis (0D): IP = (V- 0.5*IP*dLi/dt)/RP + IBS + ICD • ICD ~ 110 kA inferredvs 96 – 160 kA predicted by codes • driven current consistent with previous tokamak experience

  10. WAVE-PLASMA INTERACTIONS PLAY A CRITICAL ROLE IN NSTX RESEARCH • HHFW provides means of electron heating • Interaction between HHFW and fast ions observed • ion interaction decreases with increasing electron beta • Initial evidence found for HHFW current drive • driven current consistent with modeling and previous FWCD experiments • higher Te needed to achieve NSTX research goals

  11. HHFW CURRENT DRIVE CONSISTENT WITH D-IIID AND TFTR CD EXPERIMENTS C. Petty et al., Plasma Physics and Controlled Fusion 43 (2001) 1747 • Operation at higher Te required to meet NSTX goals • Increased power and improved confinement should allow this

More Related