Scaling of impurity Ne

1
Scaling of impurity (Ne Ar) transport in beam
heated NSTX H-mode discharges

• L. F. Delgado-Aparicio, D. Stutman, K. Tritz, and
  M. Finkenthal
• The Johns Hopkins University, The Plasma
  Spectroscopy Group
• R. E. Bell, R. Kaita, S. Kaye, B. P. LeBlanc, S.
  Paul,
• L. Roquemore and D. Smith
• Princeton Plasma Physics Laboratory
• F. Levinton, H. YuhNOVA Photonics, Inc.

NSTX, results meeting Monday, July 22,
2007 Princeton, New Jersey, USA
2
Abstract

• Motivation
• Perform particle transport studies in high
  (Power b) performance
• NSTX H-modes, important for NSTX and the
  next-step ST.

• DZ (diffusion) vZ (convective velocity)
• Identify regimes with possible impurity
  screening (vZgt0).
• r scaling at fixed q-profile,
• Ip and Bf scaling

• Experiment
• i) Neon injected in MHD quiescent high-b,
  high confinement H-modes.
• ii) The main diagnostic used was the
  multi-color optical SXR array.
• iii) B Ip scanned at fixed q-profile for
  r scaling experiments.

3
Experimental requirements and issues during XP 716

• Experimental requirements
• Sources A B _at_ 90 kV, and source C _at_ 70 kV
• Turn of source C _at_ 300 ms
• Impurity injection _at_ 350 ms

• Issues during XP 716
• Source B had to be turned off. Worked at 4 MW
  with sources A C
• Multiple ELMs and possible inboard MARFE
  activity
• Try to reduce the ELM activity by changing the
  CS fueling
• MHD activity in 5.5 kG shots
• H-mode ? L-mode ? H-mode (change timings)
• Impossible to achieve good conditions _at_ 0.8 MA ?
  0.9 MA
• Control access for TVPS PLC
• Failed to open shutters (TIVs) for good Ar
  injection!

4
Neon injection at 4.5 kG and 1.0 MA (121032
121031)
Did MHD e.g. ELMs, MARFEs or (m,n) modes
shield the core from impurities?
Neon, t?400,406ms
CORE MID-RADIUS EDGE
5
Argon injection at 4.5 kG and 1.0 MA (121036
121035)
Argon, t?400,410ms
CORE MID-RADIUS EDGE
6
Neon injection at 5.5 kG and 1.0 MA (121017
121015)
Neon, t?350,360ms
CORE MID-RADIUS EDGE
7
Neon injection at 5.5 kG and 1.2 MA (121030
121029)

• Background H-L-H-mode conditions _at_ 390 ms. tE
  and Sn increased strongly when in L-mode
• Neon seeded Do not have the H-L-H transitions.
  tE and Sn increased when gas is injected!

Neon, t?420,430ms
CORE MID-RADIUS EDGE
MHD
8
Future work

• Invert line-integrated data to obtain SXR
  emissivity profiles.
• Run MIST code. Possible need of time-dependent
  (DZ VZ) analysis.
• Establish (if possible) impurity scaling at 4.5
  kG and 1.0 MA.
• Investigate the role of MHD and ELMs in
  shielding the core.
• Study the transport reduction at high current
  during the Ip scaling (5.5 kG 1.0 MA vs. 5.5 kG
  1.2 MA)
• Find out why tE and Sn increased when gas was
  injected.