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Oct 13 – 18, 2014
Hotel Park Inn Pribaltiyskaya
Europe/Moscow timezone

Pedestal Characteristics during the Edge Localized Mode Mitigation by Super-Sonic Molecular Beam Injection on KSTAR

Oct 17, 2014, 2:00 PM
4h 45m
Green 8-9 (Hotel Park Inn Pribaltiyskaya)

Green 8-9

Hotel Park Inn Pribaltiyskaya

Saint Petersburg, Russian Federation
Poster Poster 8

Speaker

Dr Hyunyong Lee (Korea Advanced Institute of Science and Technology)

Description

This paper describes the pedestal characteristics during the Edge Localized Mode (ELM) mitigation by Super-sonic Molecular Beam Injection (SMBI) on KSTAR. After SMBI, whose pressure and duration time are 1 MPa and 8 ms, respectively, the reductions in both amplitude and time interval of D_alpha signals indicate the mitigation of type I-like ELM by SMBI. Despite the cold neutral gas injected by SMBI, the stored energy (W_p) did not change by the injection event. The fractional changes in electron density (delta n_e/n_e) and stored energy (delta W_p/W_p) by a single ELM burst and the change in H factor are small after SMBI. The ELM frequency (f_ELM) was increased by a factor of 2 - 3 due to SMBI, on the other hand, the change in f_ELM owing to the increase in the line-averaged electron density is only 8-15 %. The influence time, which is the time length of ELM mitigation, was about 300 ms. During the mitigated ELM phase by SMBI, both pedestal electron density gradient (nabla n_e^ped) and the pedestal electron temperature (T_e^ped) were reduced. As a result, the pedestal electron pressure (P_e^ped) and its gradient were decreased by about 50 %. According to a diffusive, bi-stable cellular automata model, the key mechanism of ELM mitigation is that the controlled relaxation of the nabla P_e^ped changes large ELMs to small ELMs. This prediction is qualitatively consistent with the experimental result and it suggests that the modification of pedestal profiles by SMBI is closely related to the ELM mitigation.
Paper Number EX/P8-9
Country or International Organisation Korea, Republic of

Primary author

Dr Hyunyong Lee (Korea Advanced Institute of Science and Technology)

Co-authors

Dr Hyungho Lee (National Fusion Research Institute) Dr Hyunsun HAN (Nuclear Fusion Research Institute, Korea) Mr Jae Sun Park (Korea Advanced Institute of Science and Technology) Dr Jongha Lee (National Fusion Research Institude) Mr Joohwan Hong (KAIST) Mr Juhyeok Jang (Korea Advanced Institute of Science and Technology) Mr June-Woo Juhn (Seoul National University) Dr Sang-hee Hahn (National Fusion Research Institute) Dr Seung Hun Lee (Korea Advanced Institute of Science and Technology) Dr Si-Woo Yoon (National Fusion Research Institute) Dr Won Ha Ko (Korea, Republic of) Prof. Wonho Choe (Korea Advanced Institute of Science and Technology)

Presentation materials

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