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.
Power balance analysis at the L-H transition in JET-ILW NBI-heated deuterium plasmas
Vincenzi P.; Solano E.R.; Delabie E.; Bourdelle C.; Snoep G.; Baciero A.; Birkenmeier G.; Carvalho P.; Cavedon M.; Chernyshova M.; Citrin, J.; Fontdecaba J.M.; Hillesheim J.C.; Huber A.; Maggi C.; Menmuir S.; Parra F.
ID | 474042 |
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DOI | 10.1088/1361-6587/ac97c0 |
PRODUCT TYPE | Journal Article |
LAST UPDATE | 2022-12-07T16:28:04Z |
EU PROJECT | EUROfusion |
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TITLE | Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium |
FOUNDING PROGRAM | H2020 |