1. Dynamics of transient divertor re-attachment
in support of ITER divertor gas injection requirements and thermal load specs.
Proposer: R. A. Pitts (IO), MIT contact: B. Lipschultz
R. A. Pitts, ITER_D_2DMGEF
Motivation
Investigate timescales and character of divertor re-attachment
If the ITER divertor plasma re-attaches at full performance, target power fluxes cannot be tolerated for more than a few seconds before critical wall heat flux at mono-block cooling tubes is exceeded.
At fRAD,DIV = 0.2, q,peak ~40 MWm-2 is possible
We wish to study situations in which divertor radiated fractions may fall transiently  loss of extrinsic seeding, confinement transitions
Target
Dta,CWHF (s)
CFC
~2.0 W
Dta,CWHF = design allowable duration before which target destruction can be excluded

2. Dynamics of transient divertor re-attachment
in support of ITER divertor gas injection requirements and thermal load specs.
Proposer: R. A. Pitts (IO), MIT contact: B. Lipschultz
Experimental approach
Initial aim is to characterize the phenomena  is it going to be a problem for ITER?
Emphasis on good divertor diagnostics: Divertor target heat and particle fluxes, volumetric radiation
If possible, similar divertor pumping configuration as in ITER (through the PFR)  probably requires USN on C-Mod but interesting to compare USN/LSN (will require consistent BB drift directions  field reversal) to see effect of presence/absence of pumping
Two areas to look at:
1. Divertor response to loss of extrinsic impurity seeding 2. Divertor response to H-L back transition
Establish H-mode (partially) detached outer divertor at high power with recycling and non-recycling impurity seeding (Ne, N2). Deliberately cut gas seeding and study dynamic response. Use both fast response (main chamber) and slower (divertor) valves.
Study divertor response across H-L back transition (due to loss of heating power) with and without impurity seeding (recycling and non-recycling)
Some edge modelling effort from ITER IO to be provided for interpretation