Speaker
Dr
Maiko Yoshida
(National Institutes for Quantum and Radiological Science and Technology)
Description
Negative magnetic shear has been demonstrated to mitigate the confinement degradation typically observed with increasing the electron to ion temperature ratio (Te/Ti), and the mechanisms are now understood in terms of fluctuation measurements and gyrokinetic (GK) simulations in DIII-D steady-state plasmas. The impact of Te/Ti on plasma transport and confinement is a critical issue for ITER and DEMO, where electron heating by alpha particles will be dominant. In the new experiments in DIII-D negative magnetic shear (NS) discharges, the Ti profile was maintained as Te/Ti increased through electron cyclotron range of frequency (ECRF) heating, while in positive magnetic shear (PS) plasmas, a large reduction in Ti was observed at increased Te/Ti. The different transport behavior has been explained by the turbulence measurements and GK simulations; the increase in Te/Ti had less impact on broadband turbulent fluctuations in the NS plasmas compared with that in the PS plasmas. The difference reflects changes in thermal energy confinement; the ion thermal diffusivity remained constant in the NS plasma but increased in the PS plasma when ECRF was applied. The reduced confinement degradation at high Te/Ti with NS has been commonly observed in DIII-D and JT-60U.
| Country or International Organization | Japan |
|---|---|
| Paper Number | EX/8-1 |
Primary author
Dr
Maiko Yoshida
(National Institutes for Quantum and Radiological Science and Technology)
