Abstract
Injecting frozen deuterium pellets into an ELMy H-mode plasma is a well established scheme for triggering edge localized modes (ELMs) before they naturally occur. This paper presents non-linear simulations of spontaneous type-I ELMs and pellet-triggered ELMs in ASDEX Upgrade performed with the extended MHD code JOREK. A thorough comparison of the non-linear dynamics of these events is provided. In particular, pellet-triggered ELMs are simulated by injecting deuterium pellets into different time points during the pedestal build-up described in A Cathey et al (2020 Nuclear Fusion 60 124007). Realistic ExB and diamagnetic background plasma flows as well as the time dependent bootstrap current evolution are included during the build-up to accurately capture the balance between stabilising and destabilising terms for the edge instabilities. Dependencies on the pellet size and injection times are studied. The spatio-temporal structures of the modes and the resulting divertor heat fluxes are compared in detail between spontaneous and triggered ELMs. We observe that the premature excitation of ELMs by means of pellet injection is caused by a helical perturbation described by a toroidal mode number of n=1. In accordance with experimental observations, the pellet-triggered ELMs show reduced thermal energy losses and a narrower divertor wetted area with respect to spontaneous ELMs. The peak divertor energy fluence is seen to decrease when ELMs are triggered by pellets injected earlier during the pedestal build-up.
| Original language | English |
|---|---|
| Article number | 075016 |
| Number of pages | 18 |
| Journal | Plasma Physics and Controlled Fusion |
| Volume | 63 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - Jul 2021 |
Bibliographical note
Funding Information:The authors would like to thank Thomas Eich, Di Hu, and Davide Silvagni for fruitful discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014–2018 and 2019–2020 under Grant No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. In particular, contributions by EUROfusion work packages Enabling Research (EnR) and Medium Size Tokamaks (MST) are acknowledged. We acknowledge PRACE for awarding us access to MareNostrum at Barcelona Supercomputing Center (BSC), Spain. Some of the simulations were performed using the Marconi-Fusion supercomputer.
Publisher Copyright:
© 2021 Institute of Physics Publishing. All rights reserved.
Funding
The authors would like to thank Thomas Eich, Di Hu, and Davide Silvagni for fruitful discussions. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training program 2014–2018 and 2019–2020 under Grant No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. In particular, contributions by EUROfusion work packages Enabling Research (EnR) and Medium Size Tokamaks (MST) are acknowledged. We acknowledge PRACE for awarding us access to MareNostrum at Barcelona Supercomputing Center (BSC), Spain. Some of the simulations were performed using the Marconi-Fusion supercomputer.
| Funders | Funder number |
|---|---|
| European Union's Horizon 2020 - Research and Innovation Framework Programme | |
| European Union's Horizon 2020 - Research and Innovation Framework Programme | 633053 |
Keywords
- ASDEX Upgrade
- ELM
- JOREK
- Pellet