Summary of 3rd Meeting of Divertor and SOL Physics ITPA Group Meeting

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Summary of 3rd Meeting of Divertor and SOL
Physics ITPA Group Meeting
ITPA SOL and Divertor physics Meeting July
15-17, 2003 St. Petersburg, Russia Rajesh
Maingi Oak Ridge National Laboratory
Presented at NSTX Physics Meeting Princeton,
NJ July 21, 2003
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Divertor Group Meeting Outline

• Joint session with plasma control group
• Seemed to focus on ITBs and NTM suppression with
  ECCD rather than basic burn control, etc.
• Physics of ELMs and their effect on divertor
• Really need to know fraction of power going to
  divertor vs walls during type 1 and type 3 ELMs
• Carbon erosion and fuel retention
• tritium retention issue main problem with carbon
  - need recovery technique work
• proposal to have all carbon during H-D phase

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Divertor Group Meeting Outline

• Disruptions effect on materials - joint with MHD
• How much power to divertor vs. wall - JET shows
  not much to div.
• Edge transport
• Intermittent vs. diffusive transport
• Can it be characterized with effective diffusion
  coefficient?
• Issue of wall surfaces receiving more particles
  than design values
• ITER physics basis
• Update 1997 document (1999 NF paper) with new
  results
• Due May-July 2004 (before IAEA)
• NSTX not mentioned at ALL, above or in ITPA
  coordinating committee documents who is PPPL
  rep.?

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Divertor Group Meeting Agenda - p1
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Divertor Group Meeting Agenda - p2
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THIS WAS A VERY LIVELY, CONTENTIOUS MEETING!

• Matthews to Maingi on 75 DW/Wped ELMS in NSTX
  Good show. In the edge group, we are always
  looking for ways to increase our sphere of
  influence! (Laugh)
• Stangeby and Whyte proposed all Graphite ITER
  during H-D
• Stangeby C3 approach (Cautious, Conservative,
  Carbon)
• Loarte BMW approach - Better Make it from W
  (tungsten)
• Unnamed Youd be insane to make the first wall
  out of anything but carbon
• Unnamed late arrival What are we talking about?
  This carbon ?! again? I am going to leave the
  room!
• Roth/Phillips You have hijacked the discussion
  session on tritium retention to propose a carbon
  wall with this political trick!

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NSTX can contribute to ITER Boundary RD

• ELM physics
• How is power distributed over divertor vs. first
  wall
• What is mechanism by which power is transported
• What governs the time-scale of heat flux rise
  time
• What governs time scale of heat flux decay time
• Need fast camera(s) to look at distributions
• NSTX has wide range of ELMs which could be used
  to test models and measure time scales explicitly
• Also, there is lingering question of neutrals
  effects on H-modes and boundary physics, but no
  machine is leading effort to measure neutral
  density at multiple poloidal location with
  cameras
• Big opportunity to contribute!

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ELM size and frequency affected by NBI heating
power
Time of constant NBI power with no locked
mode signature
Double-null
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Average ELM size largest at low NBI power, and
varies inversely with frequency (like Type 1 ELMs
at conventional R/a)
DW/Wped
Double-null