1. Turbulence Imaging with Impurity Lines
S. Zweben, J. Terry, O. Grulke, D. Stotler, D. D’Ippolito,
S. Krasheninnikov, B. LaBombard, J. Myra, S. Pigarov, M. Umansky
C-Mod Ideas Forum /2-3/04
Goal: Look for inward turbulent transport of impurity ions
Method: Use PSI-5 camera with impurity puffs in GPI view
Run time: Initially 1/2 day with small puffs of He, Ne, or Ar

2. Background and Motivations
• Turbulent transport of electrons seems to be outward in
SOL due to “blob” convection (at midplane, anyway)
• Yet impurities must have some inward motion to enter
the plasma (but Nachtrieb saw He “outward pinch”)
• Theory says that turbulenet “holes” might carry impurity
ions inward (e.g. Krash... ‘02, D’Ippolito ‘04)
look for turbulent transport of impurities in SOL with GPI
Difficulties:
need lines ~ as bright at Da (use local impurity puffs)
ionization balance will limit radial range of image
toroidal transport of ions will reduce localization

3. Possible Experiments on C-Mod
• Puff impurity gases at GPI location and look at images
and fast diodes with appropriate filters: e.g.
He+ (468.6 nm); Ne+ (456.9 nm); Ar+ (488.2 nm)
[Boron, Carbon,... ?]
• Avoid possible changes in turbulence due to radiative
cooling for strong puffs (or, look at effect of cooling
in conjunction with Grulke’s experiment)
• Maybe use LaBombard gas puffing probe (+ optics) ?