Speaker
Dániel Réfy
Description
An intermediate phase (M-mode [1], I-phase [2][3] or LCO [4]) close to the L-H transition has been identified at various magnetic confinement fusion devices, sharing the same feature of low frequency oscillation (LFO, few kHz), quasi-periodic changes of the plasma edge pressure, turbulence amplitude and flow velocity. This contribution aims at a comparative analysis of this phase in terms of the modulation of edge and SOL density and temperature pedestal properties and the high-frequency oscillations at the JET, AUG, COMPASS and EAST tokamaks. The main tool used in the investigation is the Lithium Beam Emission Spectroscopy (Li-BES) diagnostic whose capabilities depend on the observation geometry and the amount of light collected. Consequently, the information from different devices is of different nature or resolution. However, the common observation is that the edge density gradient and turbulence amplitude is modulated at the LFO frequency. At AUG and JET the analysis of the ECE signals, while at COMPASS the probe measurements revealed that the electron temperature is also modulated in phase with the density. Further, a high frequency oscillation (HFO, 10-150 kHz) of the magnetics and the density was characterized, its amplitude is modulated with the LFO frequency. The relation between these and both the density and the temperature pedestal modulation will be shown. The virtual 2D measurement at COMPASS allows investigation of the poloidal flow velocity modulation, while the real 2D Li-BES system at EAST revealed the poloidal and radial wave structure of the HFO activity. Our results indicate that these phenomena at the various experiments are likely related.
[1] E. R. Solano et al 2017 Nucl. Fusion 57 022021
[2] G. Birkenmeier et al 2016 Nucl. Fusion 56 086009
[3] G.S. Xu et al 2014 Nuclear Fusion 54 013007
[4] O. Grover et al accepted for publication in Nuclear Fusion
Primary author
Dániel Réfy
Co-authors
Attila Bencze
(Wigner RCP, Budapest, Hungary)
Balázs Tál
(MPI for Plasma Physics, Garching, Germany)
Dániel Dunai
(Wigner RCP, Budapest, Hungary)
Elizabeth Wolfrom
(MPI for Plasma Physics, Garching, Germany)
Dr
Emilia Rodríguez Solano
(Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain)
Ephrem Delabie
(ORNL, Tennessee, USA,)
Florian Laggner
(MPI for Plasma Physics, Garching, Germany)
Gregor Birkenmeier
(Max Planck Institute for Plasma Physics)
Guanghai Hu
(Institute of Plasma Physics CAS, Hefei, China)
Gábor Anda
(Wigner RCP, Budapest, Hungary)
Jakub Seidl
(Institute of Plasma Physics of the CAS, Prague, Czech Republic)
Jaroslav Krbec
(Institute of Plasma Physics of the CAS, Prague, Czech Republic)
Martin Hron
Mathias Brix
(CCFE, Abingdon, United Kingdom)
Dr
Nicola Vianello
(Consorzio RFXPadova, Italy)
Ondřej Grover
Pavel Hacek
(Institute of Plasma Physics of the CAS, Prague, Czech Republic)
Radomír Panek
(Institute of Plasma Physics of the CAS, Prague, Czech Republic)
Rui Gomes
(IPFN, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal)
Sándor Zoletnik
(Wigner RCP, Budapest, Hungary)
Vladimír Weinzettl
