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Title	114: Toroidal peaking of radiation, response time for triggering TQ and mitigation efficiency during mass
Name:	Alberto Loarte-Prieto Alberto.Loarte@iter.org	Affiliation:	ITER Organization
Research Area:	Disruption Mitigation	Presentation time:	Requested
Co-Author(s):	M. Sugihara, R. Pitts, A. Loarte, E. Hollmann, V. Izzo, N. Eidietis,D. Humphreys	ITPA Joint Experiment :	No
Description:	Measure toroidal peaking of radiation, pre-thermal quench time duration and heat flux reduction on target plate.	ITER IO Urgent Research Task :	Yes
Experimental Approach/Plan:	Choose reference discharge, e.g., typical ELMy H-mode, and perform experiments with changing the injection rate/amount of impurity, e.g., neon. Radiation asymmetry, or toroidal peaking if it can be assessed, should be measured by AXUV during pre-TQ and TQ phases. Simultaneously time duration of pre-TQ should be derived from the time sequence data for edge and core Te, Prad and others. Set up fast diagnostics, especially IR cameras and wall probes, for accurate heat load measurements on the divertor target region during TQ phase and derive the reduction of the heat flux by the impurity injection with varied injection rate/amount. These experiments should be repeated for similar reference discharges to derive the database of the inter-relations between toroidal peaking, pre-TQ time duration and heat flux reduction with respect to the injection rate/amount.
Background:	During the massive gas injection, possible large radiation peaking is a large concern in ITER. In particular, recent NIMROD calculation shows that large peaking is generated by m/n=1/1 MHD activity during thermal quench phase. In this case, increasing the number of injection port location would be less effective to reduce the peaking factor and other control scheme needs to be developed. It is conjectured that one potential control scheme is to optimize the injection rate and amount. One could expect that with decreasing the injection rate and amount, the injected impurity will distribute around the torus more uniformly, which may reduce the radiation peaking factor both during pre-TQ and TQ phases. On the other hand, time duration of pre-TQ will be prolonged (prolonged latency time), by which we will lose fast response for triggering the TQ, and in addition, mitigation performance (reduction factor) of the heat flux on the target plate could be degraded. Key point is whether we can find balanced operation window between lower peaking factor and longer response time and degraded mitigation performance in ITER. For this purpose, systematic database of these inter-relations is very important for DMS design of ITER and they have not been studied yet.
Resource Requirements:
Diagnostic Requirements:	AXUV, IR fast cameras (aimed at lower divertor and at main chamber, if possible), fast visible cameras (aimed at main chamber to the extent possible), SPRED, SXR, interferometers, fast filterscopes.
Analysis Requirements:	detailed analysis will be required to evaluate the radiation peaking factor, heat flux reduction factor.
Other Requirements:	None