Dynamics of transient divertor re-attachment

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 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 seeding2. 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