1 / 14

XP-815: Investigation of SOL widths in NSTX H-mode plasmas

XP-815: Investigation of SOL widths in NSTX H-mode plasmas. J-W. Ahn 1 , R.Maingi 2 , J.A.Boedo 1 , V.Soukhanovskii 3. Acknowledgement: B. LeBlanc and R. Kaita for TS data. 1 University of California – San Diego 2 Oak Ridge National Laboratory 3 Lawrence Livermore National Laboratory.

nau
Télécharger la présentation

XP-815: Investigation of SOL widths in NSTX H-mode plasmas

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. XP-815: Investigation of SOL widths in NSTX H-mode plasmas J-W. Ahn1, R.Maingi2, J.A.Boedo1,V.Soukhanovskii3 Acknowledgement: B. LeBlanc and R. Kaita for TS data 1University of California – San Diego 2Oak Ridge National Laboratory 3Lawrence Livermore National Laboratory J-W.Ahn, NSTX Results Review, 08/06/2008

  2. Introduction • Primary Objectives of XP-815: • 1. To find dependence of near SOL widths on plasma parameters •  comparison with existing scaling laws •  develop empirical scaling laws for NSTX H-mode plasmas • 2. To compare upstream SOL widths and target heat flux width to investigate parallel (and/or perpendicular) SOL transport • 3. To find relation of SOL widths with edge turbulence characteristics • Diagnostics: • Reciprocating mid-plane fast probe – 0.5ms temporal, 1mm spatial resolution for Te and ne measurement • Divertor target IR camera (33ms temporal, 6mm spatial resolution) – target heat flux profile measurement • Thomson Scattering – 60Hz temporal, 1-2cm spatial resolution in the SOL • Edge turbulence measurement: Probe Isat tip, GPI, reflectometry, USXR, mid-plane Dβ camera, etc J-W.Ahn, NSTX Results Review, 08/06/2008

  3. Edge density profile is ‘fixed’ during the H-mode density ramping period 1. Te,sep estimated from 2 point model  TS profiles as a function of R-Rsep 2. ne,sep appears to be fixed irrespective of nebar 3. This enables us to ensemble TS profiles at different time slices for identical H-mode shots to construct a profile with higher spatial resolution J-W.Ahn, NSTX Results Review, 08/06/2008

  4. Density scan: λTe, λne, and λq t=648ms t=382ms 1. nebar continuously rises during the H-mode, by a factor of ~2, with ne,sep fixed 2. λq stays at 4-5mm over the whole density ramping period 3. λTe and λne also stay constant J-W.Ahn, NSTX Results Review, 08/06/2008

  5. Ip scan1: λjsat and λq 1. Ip ↑  λjsat ↓ and λq ↓ 2. R-Rsep for fast probe Jsat data is from equilibrium reconstruction  The apparent radial ‘shift’ of Jsat profiles with respect to each other isthought to be due to the uncertainty in LCFS position determined by equilibrium reconstruction J-W.Ahn, NSTX Results Review, 08/06/2008

  6. Ip scan 2: λTe and λne Ip ↑ λTe decreases and λne stays constant J-W.Ahn, NSTX Results Review, 08/06/2008

  7. Power scan: λTe and λne 1. PNBI↑  λTe decreases and λne stays constant 2. λq decreases from 0.7cm to 0.5cm J-W.Ahn, NSTX Results Review, 08/06/2008

  8. Comparison with H-mode SOL width scaling laws from conventional tokamaks from AUG1 from AUG1 from JET2 1. λTe , λne , and λq dependence on Ip and power: consistent with scaling laws 2. λq dependence on density: consistent with scaling law 3. λTe and λne dependence on density: different trend from scaling laws 1K. McCormick, JNM 266-269 (1999) 99 2W.Fundamenski, NF 44 (2004) 20 J-W.Ahn, NSTX Results Review, 08/06/2008

  9. Relation between λq and λTe in Near SOL (conduction-limited regime) Dominant || electron conduction with ||Te (2) Assume offset exponential profiles (1) Assume simple exponential profiles Conventional relation Additional factor introduced J-W.Ahn, NSTX Results Review, 08/06/2008

  10. λTe/λq=2 λTe/λq=1 ELM-free H-mode Type-V ELM H-mode λTe/λq ratio for ELM-free and Type-V ELM H-modes λTe/λq = is expected if e-conduction is dominant, considering flat Te and ne profiles in the far SOL (ie, λTe/λq=2-2.5) 2. Experimental results: – ELM-free H-mode: λTe/λq ~ 2 – Type-V ELM H-mode: λTe/λq≤ 1 ELMs playing a role in reducing λTe/λq ratio???, eg multiple stripes at the divertor target, therefore broadening the measured (time averaged) λq??? Detailed physical mechanisms to be investigated using the fast IR camera J-W.Ahn, NSTX Results Review, 08/06/2008

  11. Summary and conclusions Confirmed dependence of λq, λTe, λjsat, and λne on Ip, power, and nebar in H-mode plasmas  negative dependence on Ip and power  no dependence on nebar  λq change appears to be driven primarily by λTe change 2. λne remains unchanged by any parameter scan 3. Comparison with H-mode scaling laws from conventional tokamaks  λTe , λne , and λq dependences on Ip and power consistent with scaling laws λq dependence on density consistent with the scaling law λTe and λne dependence on density shows different trend from scaling laws 4. NSTX near SOL plasma appears e-conduction dominated without ELMs 5. ELMs reduce λTe/ λq ratio? Physical mechanisms to be investigated (eg, due to target λq broadening, etc) J-W.Ahn, NSTX Results Review, 08/06/2008

  12. Future Work 1. More data point and confidence  SOL width scaling laws  Comparison with theoretical models eg, SOLPS results and analytic models (J.Canik, R.Maingi)  Extrapolation to future machines 2. Detailed investigation of SOL transport  roles of heat conduction and convection associated with ELMs  perpendicular particle transport (eg, Deff from edge Dβ profile) 3. Investigate relation of SOL widths with edge turbulence characteristics (collaboration with J.Boedo) J-W.Ahn, NSTX Results Review, 08/06/2008

  13. Backup: Ensembled TS profiles, reliable??? Ip=1MA, PNBI=1MW Type-V ELM H-mode 45 TS profiles Te,sep=35eV (from 2pt model) Te,sep=70eV 1.χ2stays low up to Te,sep=45eV 2. For Te,sep > 45eV, ensembled profile becomes more scattered  Te,sep=35eV is in the ball park?? 3. However, some ensembled profiles show monotonic χ2 increase from lower Te,sep J-W.Ahn, NSTX Results Review, 08/06/2008

  14. Backup: Ip scan, λTe and λne 1. Te and ne profiles from the fast probe 2. Large R-Rsep values for the profiles & the respective profile ‘shift’  due to uncertainty in LCFS position determined by LRDFIT???  Te,sep is expected to be ~30eV from power balance consideration J-W.Ahn, NSTX Results Review, 08/06/2008

More Related