Power balance analysis at the L-H transition in JET-ILW NBI-heated deuterium plasmas

JET Contributors, P. Vincenzi, M. Ben Yaala

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3 Citations (Scopus)

Abstract

The understanding of the physics underlying the L-H transition has strong implications for ITER experimental reactor and demonstration power plant (DEMO). In many tokamaks, including JET, it has been observed that, at a particular plasma density, n e,min, the power necessary to access H-mode PL-H is minimum. In the present work, L-H transitions of JET deuterium plasmas heated by neutral beam injection (NBI) are studied for the first time by means of a power balance analysis to characterize the main contributions in the transition, through integrated transport modelling. In the pulses analysed, we do observe a minimum of the L-H power threshold in density, indicating the presence of density branches and of n e,min. Electron and ion heat fluxes at the transition are estimated separately. The electron/ion equipartition power results in favour of the ions, as shown by QuaLiKiz quasilinear gyrokinetic simulations, which predict a larger ion transport that causes T e > T i. The resulting edge ion heat flux also shows a clear change of slope below n e,min, similarly to ASDEX-Upgrade (AUG) NBI pulses (Ryter et al 2014 Nucl. Fusion 54 083003). JET NBI data are compared to radio-frequency heated AUG and Alcator C-mod pulses (Schmidtmayr et al 2018 Nucl. Fusion 58 056003), showing a different trend of the power, coupled to ions at the L-H transition with respect to the linearity observed in the radio-frequency heated plasmas. The presence of n e,min and the role of the ion heat flux is discussed in the paper, although it seems it is not possible to explain the presence of a PL-H minimum in density by a critical ion heat flux and by the equipartition power for the JET NBI-heated plasmas analysed.

Original languageEnglish
Article number124004
JournalPlasma Physics and Controlled Fusion
Volume64
Issue number12
DOIs
Publication statusPublished - 28 Oct 2022

Keywords

  • H-mode
  • ion heat flux
  • JET
  • L-H
  • power balance analysis

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