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 language | English |
|---|---|
| Article number | 124004 |
| Number of pages | 11 |
| Journal | Plasma Physics and Controlled Fusion |
| Volume | 64 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - Dec 2022 |
Bibliographical note
Funding Information:This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. This work has been supported also by a EUROfusion Engineering Grant. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Additionally, the work was supported in part by Spanish Grant FIS2017-85252-R, funded by MCIN 10.13039/ 501100011033 and by ERDF ‘A way of making Europe’. The authors wish to thank C Angioni, R Bilato, T Bolzonella, J Hughes, F Köchl, U Plank and F Ryter for the useful inputs and discussions. In particular, data for figure have been kindly provided by J Hughes and F Ryter.
Funding
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. This work has been supported also by a EUROfusion Engineering Grant. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Additionally, the work was supported in part by Spanish Grant FIS2017-85252-R, funded by MCIN 10.13039/ 501100011033 and by ERDF ‘A way of making Europe’. The authors wish to thank C Angioni, R Bilato, T Bolzonella, J Hughes, F Köchl, U Plank and F Ryter for the useful inputs and discussions. In particular, data for figure have been kindly provided by J Hughes and F Ryter.
Keywords
- H-mode
- ion heat flux
- JET
- L-H
- power balance analysis