slide1
Download
Skip this Video
Download Presentation
XP-826: Investigation of “X-point limiter” plasmas M. Bell, R. Maingi, K-C. Lee

Loading in 2 Seconds...

play fullscreen
1 / 4

XP-826: Investigation of “X-point limiter” plasmas M. Bell, R. Maingi, K-C. Lee - PowerPoint PPT Presentation


  • 129 Views
  • Uploaded on

XP-826: Investigation of “X-point limiter” plasmas M. Bell, R. Maingi, K-C. Lee. Define LCFS by a limiter contact close to and just inside the X-point An alternative to conventional poloidal divertor H-mode has been obtained reliably without an X-point on the boundary

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' XP-826: Investigation of “X-point limiter” plasmas M. Bell, R. Maingi, K-C. Lee' - selena


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

XP-826: Investigation of “X-point limiter” plasmas

M. Bell, R. Maingi, K-C. Lee

  • Define LCFS by a limiter contact close to and just inside the X-point
    • An alternative to conventional poloidal divertor
    • H-mode has been obtained reliably without an X-point on the boundary
    • Flux expansion near X-point and tangential contact spread heat load
  • XP-826 tried to make an X-point limiter on lower outer divertor plate
    • SOL contact at location of Liquid Lithium Divertor plates
  • Approach
    • Start with 0.9MA, 65kA TF LSN plasma with 2-source NBI
    • Set PF2L/Ip = 4kA/MA, PF2U/Ip = 2.5kA/MA; PF1AL/Ip, PF1AU/Ip to zero
    • Adjust vertical position down and, depending on the variation in li, adjust PF2L/Ip to bring the X-point close to lower outer divertor plate
    • Attempt feedback control of the X-point location with rtEFIT
    • Repeat shots to condition contact point then assess H-mode access
  • Experiment could also provide X-point height scan (proposed by K-C. Lee)
discharges produced with x point close to outboard divertor plate

Ip 0.9MA; ITF -65kA; PNBI 4.0MW

XP≠826

-1.4

Center column

XP=826

ZX-point (m)

-1.6

Inner divertor

Outer divertor

0.2

0.4

0.6

0.8

RX-point (m)

Discharges Produced with X-Point Close to Outboard Divertor Plate
  • ~4 hours total runtime on 3 days (4/25, 5/2, 6/16)
    • Essentially as “filler” on latter 2 days
    • 12 productive shots plus initial baseline shot

128756, 0.3s

stability appeared to be reduced
Stability Appeared to be Reduced
  • Higher TF needed to maintain q95 > 7
  • H-mode transition occurred while plasma limited on inner wall
    • Confinement appears similar to pre-lithium shots in standard LSN shape
  • Reduced lower triangularity 0.3–0.4 expected to reduce N limit
  • Not able to assess conditioning effect with small number of shots
  • Shots after lithium experiments collapsed at even lower N
experiment was limited success
Experiment was Limited Success
  • X-point limiter configuration was achieved transiently
    • Provides a proof-of-principle for experiments with LLD
    • Appears to be compatible with H-mode
  • Need to optimize control strategy to improve reproducibility
    • Using dRsep control may not be best method
    • X-point control has not been used routinely on NSTX
  • Increasing cross-sectional area (taller, fatter plasma) would relax need for high TF (65kA) and modest Ip (0.9MA) to maintain q95 above practical limit
  • Too few shots were run to assess possible effects of conditioning a new contact area on the PFCs
ad