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This work studies the influence of RF waves in ICRH range of frequency on fusion alphas during the recent JET D-T campaign. Fusion alphas from D-T reactions are born with energies of about 3.5MeV and therefore have significant Doppler shift enabling synergistic interaction between them and RF waves at broad range of frequencies including the ones foreseen for future fusion machines ITER and SPARC. Resonant interaction between RF waves and alphas, also called synergistic effects, will modify the alpha distribution and ultimately will have an impact on alpha orbit losses and heating. Data from JET 3.43T/2.3MA pulses based on the hybrid scenario during the DTE2 campaign were used for the analysis in this study. The impact of synergistic effects on alpha orbit losses and alpha heating is assessed. Conclusions are based on analysis of experimental data for fast alphas losses, i.e. measurements from neutral particle analyser, fast ion losses scintillator detector, Faraday cups, and TRANSP simulations. Experimental data and TRANSP analysis indicate that there are indeed changes in the alphas’ distribution function due to interaction with RF waves. Data from the scintillator detector and the Faraday cups were compared for pulses with and without ICRH power and versus cases with enhanced alpha losses due to MHD activities. The trends from these diagnostics consistently show no additional alpha losses due to interaction with RF waves. TRANSP predictions for the impact of the synergistic effects on alpha heating show up to 42% increase in alpha electron heating and up to 25% increase in alpha ion heating. These effects however become negligibly small, less than 1%, when alpha heating is compared to the total auxiliary hearting power in the investigated JET pulses., This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them., Peer Reviewed, "Article signat per 27 autors/es: Krassimir K Kirov, Fulvio Auriemma, Phillip Bonofiglo, Clive D Challis, Elena de la Luna, Jacob Eriksson, Daniel Gallart, Jeronimo Garcia, Marina Gorelenkova, Joerg Hobirk, Philippe Jacquet, Athina Kappatou, Yevgen Kazakov, David Keeling, Damian King, Vasily Kiptily, Ernesto A Lerche, Costanza F Maggi, Joelle Mailloux, Paola Mantica, Mervi Mantsinen, Mikhail Maslov, Sheena Menmuir, Ridhima Sharma, Paula Sirén, Žiga Štancar and Dirk Van Eester", Postprint (author's final draft)

The PION code has been integrated into the European Transport Solver (ETS) transport workflow, and we present the first application to model Ion Cyclotron Resonance Frequency (ICRF) heating scenarios in the next-step fusion reactor ITER. We present results of predictive, self-consistent and time-dependent simulations where the resonant ion concentration is varied to study its effects on the performance, with a special emphasis on the resulting bulk ion heating and thermal ion temperature. We focus on two ICRF heating schemes, i.e., fundamental H minority heating in a 4He plasma at 2.65 T/7.5 MA and a three-ion ICRF scheme consisting of fundamental 3He heating in a H-4He plasma at 3.3 T/ 8.8 MA. The H minority heating scenario is found to result in strong absorption by resonant H ions as compared to competing absorption mechanisms and dominant background electron heating for H concentrations up to 10%. The highest H absorption of ∼80% of the applied ICRF power and highest ion temperature of ∼15 keV are obtained with an H concentration of 10%. For the three-ion scheme in 85%:15% H:4He plasma, PION+ETS predicts 3He absorption in the range of 21–65% for 3He concentrations in the range of 0.01–0.20%, with the highest 3He absorption at a 3He concentration of 0.20%., This research was funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion)., Peer Reviewed, Postprint (published version)

Superconductivity is a physical phenomenon of some materials that allow them to conduct electrical current without resistance. This property has a wide range of applications. In particular, type-II high-temperature superconductors appear promising for building strong electromagnets carrying large amounts of current in the extreme conditions foreseen for future fusion reactors. However, their fabrication and related experiments are highly expensive and complex. Therefore, there is an increasing need for numerical models to guide the design optimization of superconducting cables and to predict their performance. In this work, we present a new code to simulate high-temperature superconductors (HTS) based on the edge finite element discretization of Maxwell’s equations in the time domain using the widely adopted H-formulation in the superconductor analysis community. This code is integrated in the High-Performance Computing (HPC) Alya suite and obtain an excellent performance up to 1024 processors in MareNostrum 4 supercomputer. This capacity allows to us to solve a wide variate of problems in big domains in relatively reduce amount of computer time, being a promising tool to aboard HTS coils design problems. Furthermore, validations against experimental data are presented and code results for superconducting tapes with different magnetic properties are analyzed., This work is part of the FusionCAT project (001-P-001722) which has been 50% co-financed by the European Fund for Regional Development of the European Union within the framework of the 2014–2020 ERDF Operational Program of Catalonia, with the support of the Generalitat of Catalonia. In addition, it has been partly co-financed by grant PID2019-110854RB-I00 funded by MCIN/AEI/10.13039/501100011033 ., Peer Reviewed, Postprint (author's final draft)

Several dedicated High-Performance Computing (HPC) centers provide essential expertise and support in developing a suitable portfolio of EUROfusion standard codes. Barcelona Supercomputing Center (BSC) is one of these HPC hubs involved in this complex task. Several fusion codes were selected, installed and analyzed to meet the developers' requirements, ranging from portability to GPU, improving the performance, getting better data management, extending the capacity of coupling with other codes, etc. In this paper, we will describe the work developed by BSC and some of the tasks carried out in this project. We will explain briefly how the project is faced and the work required to create good quality codes, i.e. robust and trustable software capable of running efficiently in modern HPC systems., This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Program (Grant Agreement No 101052200 — EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. The research group Fusion Group at Barcelona Supercomputing Center is grateful for the support received from the Departament de Recerca i Universitats de la Generalitat de Catalunya with code 2021 SGR 00908, and from the Spanish National R&D Project PID2019-110854RB-I00 funded through MCIN/AEI/10.13039/501100011033. This work was supported by the Ministry of Education, Youth and Sports of the Czech Republic through the e-INFRA CZ (ID:90254)., Peer Reviewed, "Article signat per 12 autors/es: Xavier Sáez, Alejandro Soba, Joan Vinyals Ylla Català, Gaurav Saxena, Marta Garcia Gasulla, Cristian Morales, David Vicente Dorca, Michael Komm, Ales Podolnik, Juri Romazanov, Edilberto Sanchez, Jose Luis Velasco and Mervi Mantsinen", Postprint (author's final draft)

Special Issue Featuring the Invited Talks from the 48th EPS Conference on Plasma Physics, 27 June - 1 July 2022, The required heating power, , to access the high confinement regime (H-mode) in tritium containing plasmas is investigated in JET with ITER-like wall at a toroidal magnetic field of T and a plasma current of MA. , also referred to as the L-H power threshold, is determined in plasmas of pure tritium as well as mixtures of hydrogen with tritium (H-T) and mixtures of deuterium with tritium (D-T), and is compared to the L-H power threshold in plasmas of pure hydrogen and pure deuterium. It is found that, for otherwise constant parameters, is not the same in plasmas with the same effective isotope mass, , when they differ in their isotope composition. Thus, is not sufficient to describe the isotope effect of in a consistent manner for all considered isotopes and isotope mixtures. The electron temperature profiles measured at the L-H transition in the outer half of the radius are very similar for all isotopes and isotope mixtures, despite the fact that the L-H power threshold varies by a factor of about six. This finding, together with the observation of an offset linear relation between the L-H power threshold, , and an effective heat diffusivity, , indicates that the composition-dependent heat transport in the low confinement mode (L-mode) determines, how much power is needed to reach the necessary electron temperatures at the edge, and hence PLH., This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. G Birkenmeier received funding from the Helmholtz Association under Grant No. VH-NG-1350, Peer Reviewed, "Article signat per 50 autors/es: G Birkenmeier, E R Solano, I S Carvalho, J C Hillesheim, E Delabie, E Lerche, D Taylor, D Gallart, M J Mantsinen, C Silva, C Angioni, F Ryter, P Carvalho, M Fontana, E Pawelec, S A Silburn, P Sirén, S Aleiferis, J Bernardo, A Boboc, D Douai, P Puglia, P Jacquet, E Litherland-Smith, I Jepu, D Kos, H J Sun, A Shaw, D King, B Viola, R Henriques, K K Kirov, M Baruzzo, J Garcia, A Hakola, A Huber, E Joffrin, D Keeling, A Kappatou, M Lennholm, P Lomas, E de la Luna, C F Maggi, J Mailloux, M Maslov, F G Rimini, N Vianello, G Verdoolaege, H Weisen, M Wischmeier and JET Contributors", Postprint (published version)

Proceedings of the 24TH TOPICAL CONFERENCE ON RADIO-FREQUENCY POWER IN PLASMAS 26–28 September 2022 Annapolis, USA, The viability of magnetic confinement fusion as an energy source depends on achieving the high ion temperatures required for D-T fusion. Among the available techniques, plasma heating with waves in the ion cyclotron range of frequencies (ICRF) is a prominent method for bulk ion heating in fusion plasmas. Furthermore, a detailed understanding of the non-linear physics of alpha heating and the complex impact of MeV-range fast ions on plasma dynamics becomes progressively more important. This paper provides a comprehensive overview of recent developments with the three-ion ICRF scenarios on Alcator C-Mod, ASDEX Upgrade and JET tokamaks. The results demonstrate the flexibility of these novel scenarios for heating bulk ions in D-T ≈ 50%-50% plasmas and efficient generation of MeV-range fast ions in multi-ion species plasmas. Several key results relevant for ITER and future fusion reactors are highlighted., This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 – EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. We thank the ITPA Energetic Particle Physics Topical Group for its support. Part of this work was also carried out in the framework of projects done for the ITER Scientist Fellow Network (ISFN). ITER is the Nuclear Facility INB No. 174. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization. This publication is provided for scientific purposes only. Its contents should not be considered as commitments from the ITER Organization as a nuclear operator in the frame of the licensing process., Peer Reviewed, "Article signat per 78 autors/es: Ye. O. Kazakov; J. Ongena; M. Nocente; V. Bobkov; J. Garcia; V. G. Kiptily; M. Schneider; S. Wukitch; J. C. Wright; M. Dreval; K. K. Kirov; S. Mazzi; R. Ochoukov; S. E. Sharapov; Ž. Štancar; H. Weisen; Y. Baranov; M. Baruzzo; A. Bierwage; R. Bilato; A. Chomiczewska; R. Coelho; T. Craciunescu; K. Crombé; E. Delabie; E. de la Luna; R. Dumont; P. Dumortier; F. Durodié; J. Eriksson; M. Fitzgerald; J. Galdon-Quiroga; D. Gallart; M. Garcia-Munoz; L. Giacomelli; C. Giroud; J. Gonzalez-Martin; A. Hakola; R. Henriques; P. Jacquet; I. Jepu; T. Johnson; A. Kappatou; D. Keeling; D. King; C. Klepper; Ph. Lauber; M. Lennholm; E. Lerche; B. Lomanowski; C. Lowry; M. J. Mantsinen; M. Maslov; S. Menmuir; I. Monakhov; F. Nabais; M. F. F. Nave; C. Noble; E. Panontin; S. D. Pinches; A. R. Polevoi; D. Rigamonti; A. Sahlberg; M. Salewski; P. A. Schneider; H. Sheikh; K. Shinohara; P. Siren; S. Sumida; A. Thorman; R. A. Tinguely; D. Valcarcel; D. Van Eester; M. Van Schoor; J. Varje; M. Weiland; N. Wendler; JET Contributors, the ASDEX Upgrade Team and the EUROfusion MST1 Team", Postprint (author's final draft)

In the paper we present an overview of interpretive modelling of a database of JET-ILW 2021 D-T discharges using the TRANSP code. The main aim is to assess our capability of computationally reproducing the fusion performance of various D-T plasma scenarios using different external heating and D-T mixtures, and to understand the performance driving mechanisms. We find that interpretive simulations confirm a general power-law relationship between increasing external heating power and fusion output, which is supported by absolutely calibrated neutron yield measurements. A comparison of measured and computed D-T neutron rates shows that the calculations' discrepancy depends on the absolute neutron yield. The calculations are found to agree well with measurements for higher performing discharges with external heating power above ∼20 $\mathrm{MW}$, while low-neutron shots display an average discrepancy of around +40% compared to measured neutron yields. A similar trend is found for the ratio between thermal and beam-target fusion, where larger discrepancies are seen in shots with dominant beam-driven performance. We compare the observations to studies of JET-ILW D discharges, to find that on average the fusion performance is well modelled over a range of heating power, although an increased unsystematic deviation for lower-performing shots is observed. The ratio between thermal and beam-induced D-T fusion is found to be increasing weakly with growing external heating power, with a maximum value of $\gtrsim$1 achieved in a baseline scenario experiment. An evaluation of the fusion power computational uncertainty shows a strong dependence on the plasma scenario type and fusion drive characteristics, varying between ±25% and 35%. D-T fusion alpha simulations show that the ratio between volume-integrated electron and ion heating from alphas is $\lesssim$10 for the majority of analysed discharges. Alphas are computed to contribute between ∼15% and 40% to the total electron heat, This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No. 101052200—EUROfusion). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them. This work has been part-funded by the EPSRC Energy Programme with grant number EP/W006839/1. The Barcelona Supercomputing Center part of this work has contributed through the Spanish National R&D Project PID2019-110854RB-I00 funded through MCIN/AEI/10.13039/501100011033. In addition BSC are grateful for the support received from the Departament de Recerca i Universitats de la Generalitat de Catalunya via the Research Group Fusion Group with code: 2021 SGR 00908. The Laboratorio Nacional de Fusión contribution was funded in part via the Spanish National R&D Project PID2021-127727OB-I00 funded through MCIN/AEI /10.13039/501100011033., Peer Reviewed, "Article signat per 43 autors/es: Ž. Štancar, K.K. Kirov, F. Auriemma, H.-T. Kim, M. Poradziński, R. Sharma, R. Lorenzini, Z. Ghani, M. Gorelenkova, F. Poli, A. Boboc, S. Brezinsek, P. Carvalho, F.J. Casson, C.D. Challis, E. Delabie, D. Van Eester, M. Fitzgerald, J.M. Fontdecaba, D. Gallart, J. Garcia, L. Garzotti, C. Giroud, A. Kappatou, Ye.O. Kazakov, D.B. King, V.G. Kiptily, D. Kos, E. Lerche, E. Litherland-Smith, C.F. Maggi, P. Mantica, M.J. Mantsinen, M. Maslov, S. Menmuir, M. Nocente, H.J.C. Oliver, S.E. Sharapov, P. Sirén, E.R. Solano, H.J. Sun, G. Szepesi and JET Contributors", Postprint (published version)

This work studies the interaction between Radio Frequency (RF) waves used for Ion Cyclotron Resonance Heating (ICRH) and the fast Deuterium (D) and Tritium (T) Neutral Beam Injected (NBI) ions in DT plasma. The focus is on the effect of this interaction, also referred to as synergistic effects, on the fusion performance in the recent JET DTE2 campaign. Experimental data from dedicated pulses at 3.43T/2.3MA heated at (i) 51.4MHz giving central minority H and n=2 D and at (ii) 32.2MHz for central minority 3He and n=2 T resonances were analyzed and conclusions were drawn and supported by modelling of the synergistic effects. TRANSP runs with and without RF kick operator predicted moderate increase, about 10%, in DT rates for the case of RF wave - fast D NBI ions interactions at n=2 harmonic of ion cyclotron resonance and negligible impact by synergistic interaction between fast T NBI ions and RF waves. JETTO modelling gives 29% enhancement of fusion rates due to RF waves – fast D NBI ions interaction and 18% enhancement for fast T NBI ions. Analysis of experimental neutron rates compared to TRANSP predictions without synergistic effects and Magnetic Proton Recoil (MPRu) neutron spectrometer indicate approximately 25-28% enhancement of fusion rates due to RF interaction with fast D ions and approximately 5-8% when RF wave – fast T NBI ions interaction is taking place. Contribution of various heating and fast ion sources have been assessed and discussed. }, This work has been carried out within the framework of the EUROfusion Consortium, funded by the European Union via the Euratom Research and Training Programme (Grant Agreement No 101052200 — EUROfusion) and from the EPSRC [grant number EP/W006839/1]. To obtain further information on the data and models underlying this paper please contact PublicationsManager@ukaea.uk . Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the European Union nor the European Commission can be held responsible for them., Peer Reviewed, "Article signat per 23 autors/es: Krassimir K Kirov, Clive D Challis, Elena de la Luna, Jacob Eriksson, Daniel Gallart, Jeronimo Garcia, Marina Gorelenkova, Joerg Hobirk, Philippe Jacquet, Athina Kappatou, Yevgen Kazakov, David Keeling, Damian King, Ernesto A Lerche, Costanza F Maggi, Joelle Mailloux, Paola Mantica, Mervi Mantsinen, Mikhail Maslov, Sheena Menmuir, Paula Sirén, Žiga Štancar and Dirk Van Eester", Postprint (published version)

The JET 2019–2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power in 2019–2020, and tested the technical and procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle (a) physics in the coming D–T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed shattered pellet injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design and operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D–T benefited from the highest D–D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER., 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., Peer Reviewed, Article signat per 1223 autors/autores: J. Mailloux1, N. Abid1, K. Abraham1, P. Abreu2, O. Adabonyan1, P. Adrich3, V. Afanasev4, M. Afzal1, T. Ahlgren5, L. Aho-Mantila6, N. Aiba7, M. Airila6, M. Akhtar1, R. Albanese8, M. Alderson-Martin1, D. Alegre9, S. Aleiferis10, A. Aleksa1, A.G. Alekseev11, E. Alessi12, P. Aleynikov13, J. Algualcil14, M. Ali1, M. Allinson1, B. Alper1, E. Alves2, G. Ambrosino8, R. Ambrosino8, V. Amosov15, E.Andersson Sunden16, P. Andrew13, B.M. Angelini17, C. Angioni18, I. Antoniou1, L.C. Appel1, C. Appelbee1, S. Aria1, M. Ariola8, G. Artaserse17, W. Arter1, V. Artigues18, N. Asakura7, A. Ash1, N. Ashikawa19, V. Aslanyan20, M. Astrain21, O. Asztalos22, D. Auld1, F. Auriemma23, Y. Austin1, L. Avotina24, E. Aymerich25, A. Baciero9, F. Bairaktaris26, J. Balbin27, L. Balbinot23, I. Balboa1, M. Balden18, C. Balshaw1, N. Balshaw1, V.K. Bandaru18, J. Banks1, Yu.F. Baranov1, C. Barcellona28, A. Barnard1, M. Barnard1, R. Barnsley13, A. Barth1, M. Baruzzo17, S. Barwell1, M. Bassan13, A. Batista2, P. Batistoni17, L. Baumane24, B. Bauvir13, L. Baylor29, P.S. Beaumont1, D. Beckett1, A. Begolli1, M. Beidler29, N. Bekris30,31, M. Beldishevski1, E. Belli32, F. Belli17, É. Belonohy1, M. Ben Yaala33, J. Benayas1, J. Bentley1, H. Bergsåker34, J. Bernardo2, M. Bernert18, M. Berry1, L. Bertalot13, H. Betar35, M. Beurskens36, S. Bickerton1, B. Bieg37, J. Bielecki38, A. Bierwage7, T. Biewer29, R. Bilato18, P. Bílková39, G. Birkenmeier18, H. Bishop1, J.P.S. Bizarro2, J. Blackburn1, P. Blanchard40, P. Blatchford1, V. Bobkov18, A. Boboc1, P. Bohm39, T. Bohm41, I. Bolshakova42, T. Bolzonella23, N. Bonanomi18, D. Bonfiglio23, X. Bonnin13, P. Bonofiglo43, S. Boocock1, A. Booth1, J. Booth1, D. Borba2,30, D. Borodin44, I. Borodkina39,44, C. Boulbe45, C. Bourdelle27, M. Bowden1, K. Boyd1, I.Bozicevic Mihalic46, S.C. Bradnam1, V. Braic47, L. Brandt48, R. Bravanec49, B. Breizman50, A. Brett1, S. Brezinsek44, M. Brix1, K. Bromley1, B. Brown1, D. Brunetti1,12, R. Buckingham1, M. Bu, Postprint (published version)

The heating power to access the high confinement mode (H-mode), PLH, scales approximately inversely with the isotope mass of the main ion plasma species as found in (protonic) hydrogen, deuterium and tritium plasmas in many fusion facilities over the last decades. In first dedicated L–H transition experiments at the Joint European Torus (JET) tokamak facility with the ITER-like wall (ILW), the power threshold, PLH, was studied systematically in plasmas of pure tritium and hydrogen–tritium mixtures at a magnetic field of 1.8 T and a plasma current of 1.7 MA in order to assess whether this scaling still holds in a metallic wall device. The measured power thresholds, PLH, in Ohmically heated tritium plasmas agree well with the expected isotope scaling for metallic walls and the lowest power threshold was found in Ohmic phases at low density. The measured power thresholds in ion cyclotron heated plasmas of pure tritium or hydrogen–tritium mixtures are significantly higher than the expected isotope mass scaling due to higher radiation levels. However, when the radiated power is taken into account, the ion cyclotron heated plasmas exhibit similar power thresholds as a neutral beam heated plasma, and are close to the scaling. The tritium plasmas in this study tended to higher electron heating fractions and, when heated with ion cyclotron waves, to relatively higher radiation fractions compared to other isotopes potentially impeding access to sustained H-modes., The authors thank P.A. Schneider, F. Ryter, A. Nielsen, and A. Kappatou for fruitful discussions and for help with data analysis tools. 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. G. Birkenmeier received funding from the Helmholtz Association under Grant No. VH-NG-1350., Peer Reviewed, "Article signat per 27 autors/es: G. Birkenmeier, E.R. Solano, E. Lerche, D. Taylor, D. Gallart, M.J. Mantsinen, E. Delabie, I.S. Carvalho, P. Carvalho, E. Pawelec, J.C. Hillesheim, F. Parra Diaz, C. Silva, S. Aleiferis, J. Bernardo, A. Boboc, D. Douai, E. Litherland-Smith, R. Henriques, K.K. Kirov, C.F. Maggi, J. Mailloux, M. Maslov, F.G. Rimini, S.A. Silburn, P. Sirén, H. Weisen and JET Contributors", Postprint (published version)

Neutron reactions on fusion reactor materials are key phenomena to be understood to enable fusion as a feasible energy source for future reactors. We present significant improvements and validations of NEUTRO, a deterministic neutron transport code dedicated to solving the Boltzmann transport equation. The code is integrated as a module in the Alya system developed by the Barcelona Supercomputing Center and uses the discrete ordinates method over an angular portion, multigroup for energy discretization and the finite element method over unstructured meshes to treat special complex domains. Material anisotropy of the scattering medium is introduced into the scattering kernel using real base expressions for spherical harmonics. In order to build the total cross-section and the respective group matrix for the elastic cross-section, we use the NJOY code. We test the solver using different geometries and materials with varying levels of scattering properties. We compare our results on classic tests, benchmarks obtained from a Nuclear Energy Agency database and test cases using other neutron transport codes., This work is part of the FusionCAT project (001-P-001722) which has been 50% co-financed with € 1.960.963,66 by the European Fund for Regional Development of the European Union within the framework of the 2014-2020 ERDF Operational Program of Catalonia, with the support of the Generalitat of Catalonia. In addition, it has been partly co-financed by grant PID2019-110854RB-I00 funded by MCIN/AEI/10.13039/501100011033., Peer Reviewed, Postprint (author's final draft)

Using the PION ICRH modelling code and comparisons against JET tokamak experiments, the effect of including pitch angle dependence within the RF diffusion operator on the fast ion particle distribution functions is quantified. It is found to be of greatest importance in cases of higher harmonic heating and lower heating ion mass, resulting in faster drop-off of the distribution's high energy tail. We see differences of several orders of magnitude in the high-energy range and significant non-linear alterations by several tens of percent to ion species power partition. ITER scenario operational parameters are also considered, and this improved treatment is shown to benefit anticipated ITER scenarios with second harmonic hydrogen heating, according to our predictions. PION's combination of benchmarked simplified wave physics and Fokker-Planck treatment offers modelling advantages. Since including the pitch angle dependence in the RF diffusion operator has not led to a significant increase in the required computing time when modelling different ICRF schemes in JET discharges, it has been made available within the production code., The CCFE part of 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. The BSC part of this project is co-financed by the European Union Regional Development Fund within the framework of the ERDF Operational Program of Catalonia 2014–2020 with a grant of 50% of total cost eligible. The authors are grateful to Jacob Eriksson for assistance with experimental data, to Lars-Göran Eriksson for discussions on the implementation of the new features, and to Colin Roach and Michael Fitzgerald for valuable comments on the manuscript., Peer Reviewed, Postprint (published version)

Tungsten (W) is an important and versatile transition metal and has a firm place at the heart of many technologies. A popular experimental technique for the characterization of tungsten and tungsten-based compounds is x-ray photoelectron spectroscopy (XPS), which enables the assessment of chemical states and electronic structure through the collection of core level and valence band spectra. However, in the case of tungsten metal, open questions remain regarding the origin, nature, and position of satellite features that are prominent in the photoelectron spectrum. These satellites are a fingerprint of the electronic structure of the material and have not been thoroughly investigated, at times leading to their misinterpretation. The present work combines high-resolution soft and hard x-ray photoelectron spectroscopy (SXPS and HAXPES) with reflected electron energy loss spectroscopy (REELS) and a multitiered ab initio theoretical approach, including density functional theory (DFT) and many-body perturbation theory (G0W0 and GW + C ), to disentangle the complex set of experimentally observed satellite features attributed to the generation of plasmons and interband transitions. This combined experiment-theory strategy is able to uncover previously undocumented satellite features, improving our understanding of their direct relationship to tungsten's electronic structure. Furthermore, it lays the groundwork for future studies into tungsten-based mixed-metal systems and holds promise for the reassessment of the photoelectron spectra of other transition and post-transition metals, where similar questions regarding satellite features remain., CK acknowledges the support from the Department of Chemistry, UCL. NKF acknowledges support from the Engineering and Physical Sciences Research Council (EP/L015277/1). AR acknowledges the support fromthe Analytical Chemistry Trust Fund for her CAMS-UK Fellowship. LER acknowledges support from an EPSRC Early Career Research Fellowship (EP/P033253/1). JL and JMK acknowledge funding from EPSRC under Grant No. EP/R002010/1 and from a Royal Society University Research Fellowship (URF/R/191004). This work used the ARCHER UK National Supercomputing Service via JL’s membership of the HEC Materials Chemistry Consortium of UK, which is funded by EPSRC (EP/L000202). JJGM and SM acknowledge the support from the FusionCAT project (001-P-001722) cofinanced by the European Union Regional Development Fund within the framework of the ERDF Operational Program of Catalonia 2014-2020 with a grant of 50% of total cost eligible, the access to computational resources at MareNostrum and the technical support provided by BSC (RES-QS-2020-3-0026). Part of this work was carried out using supercomputer resources provided under the EU-JA Broader Approach collaboration in the Computational Simulation Centre of International Fusion Energy Research Centre (IFERC-CSC), Peer Reviewed, "Article signat per 13 autors/es: C. Kalha, L. E. Ratcliff, J. J. Gutiérrez Moreno, S. Mohr, M. Mantsinen, N. K. Fernando, P. K. Thakur, T.-L. Lee, H.-H. Tseng, T. S. Nunney, J. M. Kahk, J. Lischner, and A. Regoutz", Postprint (author's final draft)

We present significant improvements and validations of a deterministic neutron transport code (NEUTRO) dedicated to solving the Boltzmann Transport Equation. The code is integrated as a module in the Alya software package developed by the Barcelona Supercomputing Center which uses the Discrete Ordinates Method on angular coordinates, multi-group for energy discretization and FEM on unstructured meshes to treat special complex domains. The anisotropy of the scattering medium is introduced into the scattering kernel using real base expressions for spherical harmonics. In order to build the total cross-section and the respective group matrix for the elastic cross-section, we use the NJOY code. We test the solver using different geometries, orders of integration for the angular discretization and number of energy groups. Finally, we compare our results against benchmarks obtained from an NEA database that reported measurements of leakage spectra of several materials., This work has been partially carried out within the framework of the EUROlab4HPC and Severo Ochoa fellowship and has been partly co-financed by the European Union Regional Development Fund (ERDF) within the framework of the ERDF Operational Program of Catalonia 2014-2020. The authors would like to thank Dr A. Portone and Dr M. Fabbri for useful discussions., Peer Reviewed, Postprint (author's final draft)

This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting the plasma composition to realize three-ion ICRF scenarios, including two equivalent possibilities for the choice of resonant absorbers that have been identified. The theoretical findings have been convincingly confirmed by the proof-of-principle experiments in mixed H?D plasmas on the Alcator C-Mod and JET tokamaks, using thermal 3He and fast D ions from neutral beam injection as resonant absorbers. Since 2018, significant progress has been made on the ASDEX Upgrade and JET tokamaks in H?4He and H?D plasmas, guided by the ITER needs. Furthermore, the scenario was also successfully applied in JET D?3He plasmas as a technique to generate fusion-born alpha particles and study effects of fast ions on plasma confinement under ITER-relevant plasma heating conditions. Tuned for the central deposition of ICRF power in a small region in the plasma core of large devices such as JET, three-ion ICRF scenarios are efficient in generating large populations of passing fast ions and modifying the q-profile. Recent experimental and modeling developments have expanded the use of three-ion scenarios from dedicated ICRF studies to a flexible tool with a broad range of different applications in fusion research. AB - This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical re, The authors are grateful to the anonymous reviewers for their constructive comments that allowed us to improve the paper, I. Voitsekhovitch for her valuable comments and suggestions during the paper preparation, and to H. Meyer and J. Faustin for fruitful discussions. We thank the ITPA Energetic Particle Physics Topical Group for its support. 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Part of this work was also carried out in the framework of projects done for the ITER Scientist Fellow Network (ISFN). ITER is the Nuclear Facility INB No. 174. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization. This publication is provided for scientific purposes only. Its contents should not be considered as commitments from the ITER Organization as a nuclear operator in the frame of the licensing process., Peer Reviewed, "Article signat per 67 autors/es: Ye. O. Kazakov, J. Ongena, J. C. Wright, S. J. Wukitch, V. Bobkov, J. Garcia, V. G. Kiptily, M. J. Mantsinen, M. Nocente, M. Schneider, H. Weisen, Y. Baranov, M. Baruzzo, R. Bilato, A. Chomiczewska, R. Coelho, T. Craciunescu K. Crombé, M. Dreval, R. Dumont, P. Dumortier, F. Durodié, J. Eriksson, M. Fitzgerald, J. Galdon-Quiroga, D. Gallart, M. Garcia-Muñoz, L. Giacomelli, C. Giroud, J. Gonzalez-Martin, A. Hakola, P. Jacquet, T. Johnson, A. Kappatou, D. Keeling, D. King, K. K. Kirov, P. Lamalle, M. Lennholm, E. Lerche, M. Maslov, S. Mazzi, S. Menmuir, I. Monakhov5, F. Nabais, M. F. F. Nave, R. Ochoukov, A. R. Polevoi, S. D. Pinches, U. Plank, D. Rigamonti, M. Salewski, P. A. Schneider, S. E. Sharapov, Ž. Štancar, A. Thorman, D. Valcarcel, D. Van Eester, M. Van Schoor, J. Varje, M. Weiland, N. Wendler, JET Contributors, ASDEX Upgrade Team, EUROfusion MST1 Team, and Alcator C-Mod Team", Postprint (published version)

One of the challenges that magnetic confinement fusion faces is achieving extreme temperatures inside the reactors. Absorption of electromagnetic waves in the ion cyclotron range of frequencies (ICRF) has demonstrated efficient plasma heating in present-day tokamak experiments and it is one of the three auxiliary heating methods foreseen for the International Thermonuclear Experimental Reactor (ITER). Therefore, the study of different heating schemes using ICRF waves is of utmost interest to optimize the fusion performance. The present thesis is focused in the computational assessment of plasma heating using ICRF waves and neutral beam injection (NBI) using the PION code. A strong emphasis is given to the physics behind these heating mechanisms and how they affect the fusion performance. This project has been carried out in the context of the present deuterium (D) campaign that is being performed at the Joint European Torus (JET) experimental reactor in preparation for the next deuterium-tritium (D-T) campaign DTE2, which is planned to begin in 2021. The results presented in this thesis consist of two parts. In the first part we model several D plasma discharges carried out at JET and we assess the role of different heating characteristics in the fusion yield in pure D plasmas. The second part of this project is focused on the extrapolation of a high performance plasma discharge to a 50%:50% D-T scenario. A comparison of the heating characteristics with pure D plasmas is provided, and special attention is given to the resulting fusion yield., Uno de los retos que afronta la fusión por confinamiento magnético es conseguir temperaturas extremas dentro de los reactores. La absorción de ondas electromagnéticas en el rango de frecuencias de ciclotrón de los iones (ICRF) ha demostrado ser un método eficiente para calentar el plasma en experimentos actuales de tokamaks. Por lo tanto, el estudio de diferentes esquemas de calentamiento con ondas ICRF es de especial relevancia para optimizar el rendimiento de la fusión. Este trabajo se centra en el análisis computacional del calentamiento del plasma con ondas ICRF y neutral beam injection (NBI) mediante el código PION. Se ha dado énfasis en la física detrás los mecanismos de calentamiento y cómo afectan al rendimiento de la fusión. Éste proyecto se ha llevado a cabo en el contexto de la presente campaña de plasmas de deuterio (D) en el reactor experimental Joint European Torus (JET) en preparación para la siguiente campaña de plasmas de deuterio-tritio (D-T), DTE2, prevista para 2021. Los resultados de éste trabajo se han presentado en dos partes. En la primera, se modelan varias descargas de plasma de D que han tenido lugar en JET y analizamos el rol del calentamiento en la potencia obtenida por fusión en plasmas de D. La segunda parte del proyecto consiste en la extrapolación de una descarga de alto rendimiento a un escenario de 50%:50% D-T, donde se compara el calentamiento con los plasmas de D y se analiza la potencia equivalente obtenida por fusión., Un dels reptes que afronta la fusió per confinament magnètic és aconseguir temperatures extremes dins dels reactors. L'absorció d'ones electromagnètiques en el rang de freqüències de ciclotró dels ions (ICRF) ha demostrat ser un mètode eficient per escalfar el plasma en experiments actuals de tokamaks. Per tant, l'estudi de diferents esquemes d'escalfament amb ones ICRF és d'especial rellevància per optimitzar el rendiment de la fusió. Aquest treball se centra en l'anàlisi computacional de l'escalfament del plasma amb ones ICRF i neutral beam injection (NBI) mitjançant el codi PION. S'ha donat èmfasi en la física darrere els mecanismes d'escalfament i com afecten el rendiment de la fusió. Aquest projecte s'ha dut a terme en el context de la present campanya de plasmes de deuteri (D) en el reactor experimental Joint European Torus (JET) en preparació per a la següent campanya de plasmes de deuteri-triti (D-T), DTE2, prevista per 2021. els resultats d'aquest treball s'han presentat en dues parts. En la primera, es modelen diverses descàrregues de plasma de D que han tingut lloc en JET i analitzem el paper de l'escalfament en la potència obtinguda per fusió en plasmes de D. La segona part de el projecte consisteix en l'extrapolació d'una descàrrega d'alt rendiment a un escenari de 50%: 50% D-T, on es compara l'escalfament amb els plasmes de D i s'analitza la potència equivalent obtinguda per fusió.

Dedicated experiments to generate energetic D ions and D-3He fusion-born alpha particles were performed at the Joint European Torus (JET) with the ITER-like wall (ILW). Using the 3-ion D-(DNBI)-3He radio frequency (RF) heating scenario, deuterium ions from neutral beam injection (NBI) were accelerated in the core of mixed D-3He plasmas to higher energies with ion cyclotron resonance frequency (ICRF) waves, in turn leading to a core-localized source of alpha particles. The fast ion distribution of RF-accelerated D-NBI ions was controlled by varying the ICRF and NBI power (PICRF≈4-6MW, PNBI≈ 3-20MW), resulting in rather high D-D neutron (≈1•1016 s-1) and D-3He alpha rates (≈2•1016 s-1) at moderate input heating power. Theory and TRANSP analysis show that large populations of co-passing MeV range D ions were generated using the D-(DNBI)-3He 3-ion ICRF scenario. This important result is corroborated by several experimental observations, in particular gamma-ray measurements. The developed experimental scenario at JET provides unique conditions for probing several aspects of future burning plasmas, such as the contribution from MeV range ions to global confinement, but without introducing tritium. Dominant fast-ion core electron heating with Ti≈Te and a rich variety of fast-ion driven Alfvén eigenmodes (AEs) were observed in these D-3He plasmas. The observed AE activities do not have a detrimental effect on the thermal confinement and, in some cases, may be driven by the fusion born alpha particles. A strong continuous increase in neutron rate was observed during long-period sawteeth (>1s), accompanied by the observation of reversed shear AEs, which implies that a non monotonic q profile was systematically developed in these plasmas, sustained by the large fast-ion populations generated by the 3-ion ICRF scenario.

For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des.82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D–T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D–T preparation. This intense preparation includes the review of the physics basis for the D–T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D–T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfvèn eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D–T campaign provides an incomparable source of information and a basis for the future D–T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas., 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, Postprint (published version)

Tesis sotmesa a embargament des de la defensa fins al dia 1 de setembre de 2020, Heating plasmas to a relevant fusion temperature is one of the key aspects of magnetically confined fusion plasmas. Radio frequency (RF) heating with electromagnetic waves in the ion cyclotron range of frequencies (ICRF) has been proven to be an efficient auxiliary method in present fusion devices such as tokamaks. Moreover, the International Thermonuclear Experimental Reactor (ITER) will be provided with ICRF antennas as one of the main heating mechanisms. For that, the study of different heating schemes to optimise the fusion performance is of utmost importance. During the 2015-2019 Joint European Torus (JET) campaigns many efforts have been devoted to the exploration of high-performance plasma scenarios envisaged for D-T operation in JET. Experiments in D, H and T are expected to lead in 2020 to the first experiments with 50%:50% D-T mixtures. These last campaigns at JET have been focused on enhancing the fusion performance of the baseline and hybrid scenarios with the final goal of improving ITER's future operation. This thesis reports on the modelling study of plasma heating through ICRF waves and NBI for recent experiments at JET with special emphasis on plasma performance. The modelling has been performed mainly with the ICRF code PION. Simulations are in excellent agreement with experimental results which proves the reliability of the results shown in this thesis. The assessment of the results offer an overview to understand and optimise plasma performance for high-performance hybrid discharges that were performed with D plasma and H minority. Impurity accumulation control with ICRF waves was found to be efficient only for a range of central resonance locations while impurity accumulation occurred for off-axis resonance. Contribution to temperature screening from fast ions was calculated to be negligible when finite orbit widths (FOW) are taken into account, as opposed to previous studies that did not take into account FOW. Small differences in H concentrati, L'escalfament de plasmes a una temperatura de fusió rellevant és un dels aspectes clau dels plasmes de fusió confinats magnèticament. L'escalfament de radiofreqüència (RF) amb ones electromagnètiques en el rang de freqüències iòniques (ICRF) s'ha demostrat que és un mètode auxiliar eficient en dispositius de fusió actuals, com ara tokamaks. D'altra banda, el Reactor Termonuclear Experimental Internacional (ITER) disposarà de les antenes ICRF com un dels principals mecanismes d'escalfament. Per això, l'estudi de diferents esquemes d'escalfament per optimitzar el rendiment de fusió és sumament important. Durant les campanyes del Joint European Torus (JET) 2015-2019 s'han dedicat molts esforços a l'exploració d'escenaris de plasma d'alt rendiment previstos per a l'operació D-T en JET. S'espera que els experiments en D, H i T condueixin el 2020 als primers experiments amb 50%: 50% de mescles D-T. Aquestes darreres campanyes a JET s'han centrat en millorar el rendiment de fusió dels escenaris bàsics i híbrids amb l'objectiu final de millorar el futur funcionament de l'ITER. Aquesta tesi dóna informació sobre l'estudi de modelització de l'escalfament de plasma mitjançant ones ICRF i NBI per a experiments recents a JET amb especial èmfasi en el rendiment del plasma. El modelat s'ha realitzat principalment amb el codi PION per a ICRF. Les simulacions estan en excel·lent acord amb els resultats experimentals el qual demostra la fiabilitat dels resultats mostrats en aquesta tesi. L'avaluació dels resultats ofereix una visió general per comprendre i optimitzar el rendiment del plasma per a descàrregues híbrides d'alt rendiment que es van realitzar amb plasma D i una minoria d'H. El control de l'acumulació de les impureses amb ones ICRF només es va trobar eficaç per a una sèrie de localitzacions de ressonància central, mentre que es va produir una acumulació d'impureses per a ressonàncies fora de l'eix. Es va calcular que la contribució a l'apantallament per temperatura de les, Postprint (published version)

Alfvén waves are electromagnetic perturbations inherent to magnetized plasmas that can be driven unstable by a free energy associated with gradients in the energetic particles' distribution function. The energetic particles with velocities comparable to the Alfvén velocity may excite Alfvén instabilities via resonant wave–particle energy and momentum exchange. Burning plasmas with large population of fusion born super-Alfvénic alpha particles in magnetically confined fusion devices are prone to excite weakly-damped Alfvén eigenmodes (AEs) that, if allowed to grow unabated, can cause a degradation of fusion performance and loss of energetic ions through a secular radial transport. In order to control the fast-ion distribution and associated Alfvénic activity, the fusion community is currently searching for external actuators that can control AEs and energetic ions in the harsh environment of a fusion reactor. Most promising control techniques are based on (i) variable fast-ion sources to modify gradients in the energetic particles' distribution, (ii) localized electron cyclotron resonance heating to affect the fast-ion slowing-down distribution, (iii) localized electron cyclotron current drive to modify the equilibrium magnetic helicity and thus the AE existence criteria and damping mechanisms, and (iv) externally applied 3D perturbative fields to manipulate the fast-ion distribution and thus the wave drive. Advanced simulations help to identify the key physics mechanisms underlying the observed AE mitigation and suppression and thus to develop robust control techniques towards future burning plasmas., 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Support by US DOE and ITER-CN is also acknowledged. The support from the FP7 People: Marie-Curie Actions (Grant No. 321455) and the Spanish Ministry of Economy and Competitiveness (Grants No. RYC-2011-09152, No. FIS2015-69362-P) is gratefully acknowledged. The work of AVM was funded by the Russian Science Foundation, project 14-22-00193, and was partly supported by the Competitiveness Program of NRNU MEPhI., Peer Reviewed, Postprint (published version)

The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q95 = 5.5, ) at low density. Higher installed electron cyclotron resonance heating power 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m−1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and Er allow for inter ELM transport analysis confirming that Er is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the E, 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission., "Article signat per més de 100 autors/es: H. Meyer, for the AUG Team: D. Aguiam, C. Angioni, C.G. Albert, N. Arden, R. Arredondo Parra, O. Asunta, M. de Baar, M. Balden, V. Bandaru, K. Behler, A. Bergmann, J. Bernardo, M. Bernert, A. Biancalani, R. Bilato, G. Birkenmeier, T.C. Blanken, V. Bobkov, A. Bock, T. Bolzonella, A. Bortolon, B. Böswirth, C. Bottereau, A. Bottino, H. van den Brand, S. Brezinsek, D. Brida, F. Brochard, C. Bruhn, J. Buchanan, A. Buhler, A. Burckhart, Y. Camenen, D. Carlton, M. Carr, D. Carralero, C. Castaldo, M. Cavedon, C. Cazzaniga, S. Ceccuzzi, C. Challis, A. Chankin, S. Chapman, C. Cianfarani, F. Clairet, S. Coda, R. Coelho, J.W. Coenen, L. Colas, G.D. Conway, S. Costea, D.P. Coster, T.B. Cote, A. Creely, G. Croci, G. Cseh, A. Czarnecka, I. Cziegler, O. D'Arcangelo, P. David, C. Day, R. Delogu, P. de Marné, S.S. Denk, P. Denner, M. Dibon, A. Di Siena, D. Douai, A. Drenik, R. Drube, M. Dunne, B.P. Duval, R. Dux, T. Eich, S. Elgeti, K. Engelhardt, B. Erdös, I. Erofeev, B. Esposito, E. Fable, M. Faitsch, U. Fantz, H. Faugel, I. Faust, F. Felici, J. Ferreira, S. Fietz, A. Figuereido, R. Fischer, O. Ford, L. Frassinetti, S. Freethy, M. Fröschle, G. Fuchert, J.C. Fuchs, H. Fünfgelder, K. Galazka, J. Galdon-Quiroga, A. Gallo, Y. Gao, S. Garavaglia, A. Garcia-Carrasco, M. Garcia-Muñoz, B. Geiger, L. Giannone, L. Gil, E. Giovannozzi, C. Gleason-González, S. Glöggler, M. Gobbin, T. Görler, I. Gomez Ortiz, J. Gonzalez Martin, T. Goodman, G. Gorini, D. Gradic, A. Gräter, G. Granucci, H. Greuner, M. Griener, M. Groth, A. Gude, S. Günter, L. Guimarais, G. Haas, A.H. Hakola, C. Ham, T. Happel, N. den Harder, G.F. Harrer, J. Harrison, V. Hauer, T. Hayward-Schneider, C.C. Hegna, B. Heinemann, S. Heinzel, T. Hellsten, S. Henderson, P. Hennequin, A. Herrmann, M.F. Heyn, E. Heyn, F. Hitzler, J. Hobirk, K. Höfler, M. Hölzl, T. Höschen, J.H. Holm, C. Hopf, W.A. Hornsby, L. Horvath, A. Houben, A. Huber, V. Igochine, T. Ilkei, I. Ivanova-Stanik, W. Jacob, A.S. Jac, Postprint (published version)

Tesi en modalitat de cotutela: Universitat Politècnica de Catalunya i Universiteit Gent. Erasmus Mundus. Aplicat embargament des de la data de defensa fins el 30/3/2021, In this thesis, a detailed analysis of the experientially observed energetic particle-driven Alfvénic instabilities in tokamak and stellarator plasmas using three dimensional numerical tools based on the reduced MHD model has been carried out. In TJ-II stellarator plasmas, modelling of chirping and steady modes assesses their coexistence on the persistent appearance of the corresponding combination of the toroidal (n) and poloidal (m) mode numbers through the rotational transform sensitivity analysis both in iota lowering and iota rising dynamic plasmas. Modelling of the experimentally observed frequency sweeping phenomenon during the presence of Alfvénic activity with radially extended low-shear and radially localized strong-shear non-monotonic (NM) iota profiles provides an extended spectrum of Alfvénic modes in the wide frequency range as compared with normal (monotonic) iota profile results. Comparison of mode frequencies calculated using a standard dispersion relation and those modelled with the reduced MHD clustered frequency solver AE3D shows an agreement with the selection of iota minimum values, which supports MHD spectroscopy calculations. Wave particle interaction (WPI) studies for the resonance function calculations developed using Monte Carlo transport model based on the 3D MHD equilibria for the TJ-II plasmas suggest for low bounce harmonics (p) the possibility of describing the non-linear evolution of the AEs in TJ-II by a sum of two ion populations with different weighting factors, one of which is dominated by drag and the other by diffusion. As the bounce harmonic increases, the resonance region starts to expand and can cover a significant area of the particle phase space until this resonance region vanishes at high bounce harmonics. In ASDEX Upgrade tokamak plasmas a bifurcated MHD equilibrium is reconstructed with formation of 3D helical core as saturated magnetic axis and the remaining torus with an axisymmetric equilibrium. The formation of heli, En esta tesis, se ha llevado a cabo un análisis detallado de las inestabilidades Alfvénicas de partículas energéticas observadas experimentalmente en plasmas de tokamak y stellarators utilizando herramientas numéricas tridimensionales basadas en el modelo MHD reducido. En los plasmas de estellarators de TJ-II, el modelado de chirping y modos estables evalúa su coexistencia en la aparición persistente de la combinación correspondiente de los números de modo toroidal (n) y poloidal (m) a través del análisis de sensibilidad de transformación rotacional tanto en disminución de iota como en aumento de iota. El modelado del fenómeno de barrido de frecuencia observado experimentalmente durante la presencia de actividad Alfvénica con perfiles de iota no monotónicos (NM) de cizallamiento fuerte y de cizallamiento fuerte radialmente extendido proporciona un espectro extendido de modos Alfvénicos en el amplio rango de frecuencia en comparación con el normal (monotónico). La comparación de las frecuencias de modo calculadas usando una relación de dispersión estándar y aquellas modeladas con el solver de frecuencia agrupada para MHD reducido AE3D muestra un acuerdo con la selección de valores mínimos de iota, que respalda los cálculos de espectroscopía MHD. Los estudios de interacción de onda-partículas (WPI) para los cálculos de la función de resonancia desarrollados utilizando el modelo de transporte Monte Carlo basado en los equilibrios 3D MHD para los plasmas TJ-II sugieren para armónicos de bajo rebote (p) la posibilidad de describir la evolución no lineal de los AE en TJ-II por una suma de dos poblaciones de iones con diferentes factores de ponderación, uno de los cuales está dominado por arrastre y el otro por difusión. A medida que aumenta el armónico de rebote, la región de resonancia comienza a expandirse y puede cubrir un área significativa del espacio de fase de partículas hasta que esta región de resonancia se desvanece en armónicos de alto rebote. En los plasmas de, (Neerlandès) De experimenteel waargenomen Alfvénic-instabiliteiten die in tokamak- en stellaratorplasma's aangedreven worden door snelle deeltjes worden in detail geanalyseerd. De analyse gebeurde met behulp van driedimensionale numerieke methodes gebaseerd op het gereduceerde MHD-model. In TJ-II stellarator plasma's werd de co-existentie van tjilpende (chirping) en steady-state modi vastgesteld op basis van het aanhoudend voorkomen van de overeenkomstige combinatie van de toroïdale (n) en poloidale (m) modenummers. Deze vaststelling gebeurde op basis van de gevoeligheid ten opzichte van de rotatie-transformatie (rotational transform). Modellering van de veging van de frequentie (frequency sweeping) van de Alfvénic-activiteit met niet-monotone iota-profielen zijn, in vergelijking met normale (monotone) iota-profielresultaten, consistent met experimentele resultaten. Studies van de interactie tussen golf en deeltjes (WPI-wave particle interaction) voor de berekening van de resonantiefunctie met behulp van Monte Carlo transportmodel voor TJ-II plasma's, suggereren dat de niet-lineaire evolutie van AE's een som is van twee ion populaties met verschillende wegingsfactoren. Voor lage bounce harmonische, wordt één gedomineerd door sleep (drag) en de andere door diffusie. In ASDEX Upgrade tokamak-plasma's wordt een vertakt MHD-evenwicht gereconstrueerd met de vorming van een 3D-spiraalvormige kern en de asymmetrische 2D-mantel. Alfvén continuümberekeningen met de vertakte evenwichten leiden tot de frequentiesplitsing tussen de continua van de hoogste frequentietak en de laagste frequentietak en het verschuiven van modi met aangrenzend n continuüm rond het frequentieaccumulatiepunt., Postprint (published version)

In recent years, a strong reduction of plasma turbulence in the presence of energetic particles has been reported in a number of magnetic confinement experiments and corresponding gyrokinetic simulations. While highly relevant to performance predictions for burning plasmas, an explanation for this primarily nonlinear effect has so far remained elusive. A thorough analysis finds that linearly marginally stable energetic particle driven modes are excited nonlinearly, depleting the energy content of the turbulence and acting as an additional catalyst for energy transfer to zonal modes (the dominant turbulence saturation channel). Respective signatures are found in a number of simulations for different JET and ASDEX Upgrade discharges with reduced transport levels attributed to energetic ion effects., The simulations presented in this work were performed at the Cobra HPC system at the Max Planck Computing and Data Facility (MPCDF), Germany. 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. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Furthermore, we acknowledge the CINECA award under the ISCRA initiative, for the availability of high performance computing resources and support. The authors would like to thank N. Bonanomi, J. Citrin, H. Doerk, Ph. Lauber, P. Manas, P. Mantica, M.J. Pueschel, K. Stimmel, P.W. Terry, D. Zarzoso, and A. Zocco for all the stimulating discussions, useful suggestions and comments., Peer Reviewed, Postprint (published version)

The radial structure of the continuum spectrum of shear Alfvén and Alfvén-acoustic waves in the beta-induced Alfvén eigenmode (BAE) frequency range is modeled for tokamak plasmas in the presence of 3D effects obtained from the bifurcated MHD equilibrium reconstruction. Plasma compressibility and geodesic curvature effects responsible for the low-frequency continuum spectrum calculations are invoked. In the equilibrium calculations we find that the helically distorted MHD equilibria may exist even for the axisymmetric devices if q = 1 rational surfaces are present. The continuum calculations with the bifurcated equilibria lead to a frequency splitting between the highest frequency branch and the lowest frequency branch continua at the frequency accumulation point. Radially localised shifting of modes happens via coupling of the adjacent n − 1 continuum around an accumulation point. Our modelling (including 3D effects) correctly reproduces the phenomenon of continuum frequency splitting and provides a possible solution for the differences of few kHz in frequency splitting, which remained unexplained with the 2D kinetic calculations (Curran et al 2012 Plasma Phys. Control. Fusion 54 055001). The pressure scaling confirms the increase of helical excursion of the magnetic axis in equilibrium reconstruction and hence the range of continuum frequency splitting. In our calculations, the existence of low-frequency continua is in agreement with the experimentally observed low-frequency modes., 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. The views and opinions expressed herein do not necessarily re ect those of the European Commission. Allah Rakha is grateful for an AGAUR FI predoctoral grant to support his PhD studies and a Severo Ochoa (SO) mobility grant to support his research stay at Max Planck Institute for Plasma Physics (IPP) Garching, Germany., Peer Reviewed, Postprint (author's final draft)

Measurements are reported of electromagnetic emission close to the cyclotron frequency of energetic ions in JET plasmas heated by waves in the ion cylotron range of frequencies (ICRF). Hydrogen was the majority ion species in all of these plasmas. The measurements were obtained using a sub-harmonic arc detection system in the transmission lines of one of the ICRF antennas. The measured ion cyclotron emission spectra were strongly filtered by the antenna system, and typically contained sub-structure, consisting of sets of peaks with a separation of a few kHz, suggesting the excitation of compressional Alfvén eigenmodes closely spaced in frequency. In most cases the energetic ions can be clearly identified as ICRF wave-accelerated 3He minority ions, although in two pulses the emission may have been produced by energetic 4He ions, originating from third harmonic ICRF wave acceleration. It is proposed that the emission close to the 3He cyclotron frequency was produced by energetic ions of this species undergoing drift orbit excursions to the outer midplane plasma edge. Particle-in-cell and hybrid (kinetic ion, fluid electron) simulations using plasma parameters corresponding to edge plasma conditions in these JET pulses, and energetic particle parameters inferred from the cyclotron resonance location, indicate strong excitation of waves at multiple 3He cyclotron harmonics, including the fundamental, which is identified with the observed emission. These results underline the potential importance of ICE measurements as a method of studying confined fast particles that are strongly suprathermal but have insufficient energies or are not present in sufficient numbers to excite detectable levels of γ-ray emission or other collective instabilities., 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 under grant agreement No 633053 and from the RCUK Energy Programme (grant number EP/P012450/1). The views and opinions expressed herein do not necessarily reflect those of the European Commission. AB was supported by the Embassy of France in the United Kingdom. We thank Ernesto Lerche for helpful information on the determination of He concentration in the pulses discussed in the paper., Peer Reviewed, Postprint (published version)

ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.

This paper reports on impurity behavior in a set of hybrid discharges with Ne seeding—one of the techniques considered to reduce the power load on reactor walls. A series of experiments carried out with light gas injection on JET with the ITER-Like-Wall (ILW) suggests increased tungsten release and impurity accumulation [C. Challis et al., Europhysics Conference Abstracts 41F, 2.153 (2017)]. The presented method relies mainly on the measurements collected by vacuum-ultra-violet and soft X-ray (SXR) diagnostics including the “SOXMOS” spectrometer and the SXR camera system. Both diagnostics have some limitations. Consequently, only a combination of measurements from these systems is able to provide comprehensive information about high-Z [e.g., tungsten (W)] and mid-Z [nickel (Ni), iron (Fe), copper (Cu), and molybdenum (Mo)] impurities for their further quantitative diagnosis. Moreover, thanks to the large number of the SXR lines of sight, determination of a 2D radiation profile was also possible. Additionally, the experimental results were compared with numerical modeling based on integrated simulations with COREDIV. Detailed analysis confirmed that during seeding experiments, higher tungsten release is observed, which was also found in the past. Additionally, it was noticed that besides W, the contribution of molybdenum to SXR radiation was greater, which can be explained by the place of its origin., 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 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. This scientific work was partly supported by the Polish Ministry of Science and Higher Education within the framework of the scientific financial resources in the years 2014-2018 allocated for the realization of the international co-financed project., Postprint (author's final draft)

Density functional theory (DFT) has become a standard tool for ab-initio simulations for a wide range of applications. While the intrinsic cubic scaling of DFT was for a long time limiting the accessible system size to some hundred atoms, the recent progress with respect to linear scaling DFT methods has allowed to tackle problems that are larger by many orders of magnitudes. However, as these linear scaling methods were developed for insulators, they cannot, in general, be straightforwardly applied to metals, as a finite (electronic) temperature is needed to ensure locality of the density matrix. In this paper we show that, once finite electronic temperature is employed, the linear scaling version of the BigDFT code is able to exploit this locality to provide a computational treatment that scales linearly with respect to the number of atoms of a metallic system. We provide prototype examples based on bulk Tungsten, which plays a key role in finding safe and long-lasting materials for Fusion Reactors; however we do not expect any major obstacles in extending this work to cover other metals. We believe that such an approach might help in opening the path towards novel approaches for investigating the electronic structure of such materials, in particular when large supercells are required., We acknowledge valuable discussions with María José Caturla and Chu-Chun Fu. S.M. acknowledges support from the MaX project, which has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant agreements 676598. M.A. acknowledges support from the Novartis Universität Basel Excellence Scholarship for Life Sciences and the Swiss National Science Foundation (P300P2-158407, P300P2-174475). We gratefully acknowledge the computing resources on Marconi-Fusion under the EUROfusion project BigDFT4F, from the Swiss National Supercomputing Center in Lugano (project s700), the Extreme Science and Engineering Discovery Environment (XSEDE) (which is supported by National Science Foundation grant number OCI-1053575), the Bridges system at the Pittsburgh Supercomputing Center (PSC) (which is supported by NSF award number ACI-1445606), the Quest high performance computing facility at Northwestern University, and the National Energy Research Scientific Computing Center (DOE: DE-AC02- 05CH11231)., Peer Reviewed, Postprint (published version)