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22-27 October 2018
Mahatma Mandir Conference Centre
Asia/Kolkata timezone
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Transport Barriers in DIII-D High βp plasmas and Development of Candidate Steady State Scenarios for ITER

24 Oct 2018, 18:00
20m
Mahatma Mandir Conference Centre

Mahatma Mandir Conference Centre

Gandhinagar (nearest Airport: Ahmedabad), India
Oral EXC - Magnetic Confinement Experiments: Confinement EX/4-TH/2 H-Mode & Pedestal

Speaker

Dr Joseph McClenaghan (Oak Ridge Associated Universities)

Description

Shafranov shift stabilizes turbulence and creates a bifurcation in kinetic ballooning mode(KBM) transport that enables high performance ITB plasmas to be sustained at reactor relevant $q_{95}$. On DIII-D, the internal transport barrier (ITB), high $\beta_N$ ~3, and very high normalized confinement $H_{98,y2}$~1.6 of the high $\beta_p$ scenario has been achieved at $q_{95}$~6.5. This is projected to meet the ITER steady-state goal of Q=5. The ITB is maintained at lower $\beta_p$ with a strong reverse shear, confirming predictions that negative central shear can lower the $\beta_p$ threshold for the ITB. There are two observed confinement states in the high $\beta_p$ scenario: H-mode confinement state with a high edge pedestal, and an enhanced confinement state with a low pedestal and an ITB. At large radius (ρ=0.8), the enhanced ITB confinement state has a much lower predicted turbulent ion energy transport than the H-mode confinement state. Simulating intermediate states, a large electromagnetic “mountain” of increased transport is found due to a KBM. Transient perturbations such as edge localized modes (ELMs) may trigger the transition between states by temporarily reducing the KBM drive. It has been observed that when there are no large type I ELMs, and there is no transition to enhanced confinement otherwise observed with lower n=3 perturbation. Quasilinear gyro-Landau fluid predictive modeling of ITER suggests that only a modest reverse shear is required to achieve the ITB formation necessary for Q=5 when electromagnetic physics including the KBM is incorporated.
Country or International Organization United States of America
Paper Number EX/4-3

Primary author

Dr Joseph McClenaghan (Oak Ridge Associated Universities)

Co-authors

Mr A. M. Garofalo (General Atomics) Dr Christopher T. Holcomb (Lawrence Livermore National Laboratory) Dr David Weisberg (General Atomics) Dr Gary M. Staebler (General Atomics) Dr Jinping Qian (Institute of plasma physics, Chinese academy of sciences) Ms Juan Huang (CnIPPCAS) Dr Lang Lao (General Atomics) Dr Qilong Ren (Institute of Plasma Physics, Chinese Academy of Sciences) Dr Siye Ding (Institute of Plasma Physics, Chinese Academy of Sciences) Prof. Xianzu Gong (Insititute of Plasma Physics, Chinese Academy Sciences)

Presentation Materials

Paper