Fusion product measurements by nuclear diagnostics in the Joint European Torus deuterium-tritium 2 campaign (invited)

Review of Scientific Instruments ARTICLE scitation.org/journal/rsi Fusion product measurements by nuclear diagnostics in the Joint European Torus deuterium–tritium 2 campaign (invited) Cite as: Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 Submitted: 3 June 2022 •Accepted: 20 August 2022 • Published Online: 27 September 2022 M. Nocente,1,2,a) V. Kiptily,3M. Tardocchi,2P. J. Bonofiglo,4T. Craciunescu,5A. Dal Molin,2 E. De La Luna,6J. Eriksson,7J. Garcia,8Z. Ghani,3G. Gorini,1,2L. Hägg,7Y. Kazakov,9E. Lerche,9 C. F. Maggi,3P. Mantica,2G. Marcer,1M. Maslov,3O. Putignano,1D. Rigamonti,2M. Salewski,10 S. Sharapov,3P. Siren,3Z. Stancar,3A. Zohar,11 P. Beaumont,3K. Crombe,9G. Ericsson,7M. Garcia-Munoz,12 D. Keeling,3D. King,3K. Kirov,3M. F. F. Nave,13 J. Ongena,9A. Patel,3C. Perez von Thun,14 and JET Contributorsb) AFFILIATIONS 1Department of Physics, University of Milano-Bicocca, Milan 20126, Italy 2Institute for Plasma Science and Technology, National Research Council, Milan 20125, Italy 3United Kingdom Atomic Energy Authority, Culham Centre for Fusion Energy, Culham Science Centre, Abingdon OX14 3DB, United Kingdom 4Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540, USA 5Institute of Atomic Physics, Magurele-Bucharest 077125, Romania 6Laboratorio Nacional de Fusión, CIEMAT, Madrid 28040, Spain 7Department of Physics and Astronomy, Uppsala University, Uppsala SE-75120, Sweden 8CEA, IRFM, Saint Paul lez Durance 13115, France 9Laboratory for Plasma Physics, LPP ERM/KMS, Brussels 1000, Belgium 10Department of Physics, Technical University of Denmark, Kgs. Lyngby 2800, Denmark 11Joˇ zef Stefan Institute, Ljubljana 1000, Slovenia 12Department of Atomic, Molecular and Nuclear Physics, University of Seville, Seville 41012, Spain 13Instituto de Plasmas e Fusao Nuclear, IST, Universidade de Lisboa, Lisboa 1049-001, Portugal 14Institute of Plasma Physics and Laser Microfusion, Warsaw 01-497, Poland Note: This paper is part of the Special Topic on Proceedings of the 24th Topical Conference on High-Temperature Plasma Diagnostics. a)Author to whom correspondence should be addressed: [email protected] b)See the author list of J. Mailloux et al., Nucl. Fusion 62, 042026 (2022). ABSTRACT A new deuterium–tritium experimental, DTE2, campaign has been conducted at the Joint European Torus (JET) between August 2021 and late December 2021. Motivated by significant enhancements in the past decade at JET, such as the ITER-like wall and enhanced auxiliary heating power, the campaign achieved a new fusion energy world record and performed a broad range of fundamental experiments to inform ITERphysicsscenariosandoperations.Newcapabilitiesintheareaoffusionproductmeasurements by nuclear diagnostics were available as a resultofadecadelongenhancementprogram.ThesehavebeentestedforthefirsttimeinDTE2andaconciseoverviewisprovidedhere.Confinedalpha particle measurements by gamma-rayspectroscopywere successfully demonstrated, albeit withlimitations at neutron rates higher than some 1017 n/s. High resolution neutron spectroscopy measurements with the magnetic proton recoil instrument were complemented by novel data from a set of synthetic diamond detectors, which enabled studies of the supra-thermal contributions to the neutron emission. In the area of escaping fast ion diagnostics, a lost fast ion detector and a set of Faraday cups made it possible to determine information on the Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-1 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi velocity space and poloidal distribution of the lost alpha particles for the first time. This extensive set of data provides unique information for fundamental physics studies and validation of the numerical models, which are key to inform the physics and scenarios of ITER. Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0101767 I. INTRODUCTION A second Deuterium–Tritium Experiment (DTE2) campaign was done at the Joint European Torus (JET) with the ITER-like wall from August 2021 to late December 2021. The new campaign was also motivated by the significantly improved capabilities that the machine had compared to the former 1997 deuterium–tritium (DT) experiment.1,2 These included the availability of an ITER relevant wall and divertor materials, increased auxiliary heating, in the form of 35 MW of maximum neutral beam injection (NBI) and up to 6 MW of radio frequency (RF) power for ion cyclotron resonance heating (ICRH) experiments, and real time schemes to sustain the dischargeathighperformanceuptoafewseconds.Inordertomatch the increased plasma physics understanding made possible by the development of sophisticated numerical codes for plasma simulations in a number of areas in the past two decades, new diagnostics for fusion product measurements (in particular, alpha particle) were available as the result of (almost) a decade long enhancement program.3These included systems for confined fuel ion and fusion product measurements, such as gamma-ray and neutron spectrometers, as well as diagnostics to detect the velocity space and location of their losses. In this paper, we provide a concise overview of the new systems available for fusion product observations in DTE2 and the measurements they have made. After a brief summary of the working principles, for each diagnostics, we present examples of data that show new possibilities for physics studies and model validation opened by the systems. At this point in time, the diagnostics have collected data, but their detailed assessment and interpretation has just started. Therefore, no attempt is made for an in-depth explanation of the physics behind the data in this paper, as this will be the subject of future dedicated publications on the experiments that made use of the diagnostics here described. II. GAMMA RAY SPECTROSCOPY MEASUREMENTS Gamma-ray spectroscopy has become an established method to study confined fast ions and electrons in the MeV range.4–6 In the DT phase of ITER, it will be one of the main methods to detect confined alpha particles, together with Collective Thomson Scattering.7Fusion born alphas lead to gamma-ray emission due to the α+9Be →n+12C∗reaction, which occurs spontaneously when 9Be is found in the plasma, for example, due to the unavoidable erosion of the Beryllium wall at JET or ITER. In this case, a gamma-ray line at the energy Eγ=4.44 MeV is expected to be measured, with an intensity and shape that depend on the number and energy distribution of the alpha particles. Enabling this measurement is, however, non-trivial. Calculations8reveal that, in a DT plasma,14MeVneutronemissionfrom the main fusion reactions is ≈105higher than the 4.44 MeV gamma-ray emission. In order to overcome this imbalance, dedicated technological solutions have been devised for ITER8,9 and detector prototypes have been developed for JET by the enhancement programs before DTE2.10,11 One solution is based on the use of a ≈1 m long LiH attenuator,9,12 which is projected to attenuate the neutron flux by a factor ≈105and the 4.44 Mev gamma-ray flux by a factor 10 only. Another is the use of the LaBr3crystal as the inorganic scintillator,10,13 combined with a free streaming data acquisition (DAQ) system with a digitization frequency of some 100 s MHz,14,15 in order to handle the MHz counting rates due to the residual neutron background on the detector.16 None of these technologies had been tested in a DT plasma before DTE2 or gamma-ray measurements had been proven in a magnetically confined DT plasma. Figure 1 shows an example of the gamma-ray spectrum that has been routinely measured in JET DTE2 plasmas, compared to a calculation of the spectrum expected at ITER in the inset. The overall similarity between data and the simulation demonstrates the success of the measurement and brings us confidence on the design of gamma-ray diagnostics for ITER. In more detail, there are three main structures in the spectrum. The most dominant is the 4.44 MeV peak from α+9Be →n+12C∗, which appears together with its single escape peak at 3.93 MeV (a feature of the instrument response function). There are then two higher energy peaks at Eγ=8.53 MeV and Eγ=9.0 MeV at lower intensity. These come fromthecaptureofthermalizedneutrons on Ni found in some components of the JET machine. Finally, there is a broad, low intensity FIG. 1. Gamma ray spectrum measured by the vertical gamma ray detector at JET in a typical DTE2 discharge. The inset shows a calculation of the gammaray spectrum expected from a ITER DT plasma, taken from Nocente et al., Nucl. Fusion57,076016(2017).Copyright2017Institute ofPhysics.Themostdominant structures marked in the inset are described in the text. Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-2 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi structure above the Ni capture peaks and that extends up to about Eγ=20 MeV. Despite being much less intense than the other peaks, this broad structure is of particular relevance as, in principle, it entails information on the fusion power. The structure is better seen, in logarithmic scale, in Fig. 2, which compares the high energy part of the gamma-ray spectrum measured in the DT calibration discharge No. 98044 (top) and in the DTE2 discharge No. 99608 (bottom). No. 98044, performed in October 2020, i.e., 1 year before DTE2, is a predominantly deuterium discharge with neutral beam injection, where tritium at some percent level was injected for the first time in the plasma as a technical test. The red line in the figure isanexponentialfitto the background, which comprises both events from charged production by neutron interaction in the LaBr3crys- tal16 and unresolved pile-ups.14 For both discharges, there is an excess of events in the region Eγ=14 MeV to Eγ=17 MeV and FIG. 2. Gamma-ray spectrum in the energy range Eγ=10–20 MeV measured in the DT calibration discharge No. 98044 at t =6–17 s (top) and in the DTE2 discharge No. 99608 at t =6–8 s (bottom). The red line is an exponential fit to the background. this is stronger when there is more tritium in the plasma, suggesting that this emission is associated with DT fusion reactions. We interpret this as a signature of 17 MeV fusion gamma-rays from the t(d,γ)5He reaction, which have been measured previously in nuclear accelerator based experiments,17 as well as in inertially confined fusion (ICF) plasmas,18,19 but not in a DT magnetically confined fusion (MCF) plasma so far. The emission is relevant as it offersthe possibility to determinethe fusion power ina reactor in an alternative way than measuring the neutron rate. The main advantage stems from the comparably simpler transport of gamma-rays than that of neutrons, mostly because of the more limited variety of interactions gamma-rays can have with the structural materials of the machine. This may be useful when the complexity of the machine increases significantly, such as in a full scale reactor. The difficulty comes, however, mostly from the present scattered knowledge of the t(d,γ)5He to t(d,n)4He branching ratio, as well as the need to absolutely calibrate the gamma-ray detector. JET, however, has a carefully calibrated set of fission chambers,20 together with a carefully designed tangential gamma-ray detector,11 and a combined analysis of neutron emission measurements and our data can determine the branching ratio under MCF DT plasma conditions. This is presently the subject of dedicated analysis, whose results will be published separately. More generally, the high resolution of the gamma-ray measurements we have performed may allow us to draw some conclusions about the velocity distribution function of the energetic ions generating the peak, both for one-step and for two-step reactions, as is mathematically illustrated by weight functions.21,22 When combined with other gamma-ray and neutron emission spectrometry diagnostics or, in principle, any other fastion diagnostic, our data may make it possible to reconstruct the velocity distribution function of the energetic ions in the plasma.23 Besides proving the feasibility of gamma-ray measurements in a DT MCF plasma, the data of Fig. 1 have also shed light on some limitations of the present conceptual design of the Radial Gamma Ray Spectrometers (RGRS) for ITER. A first shortcoming comes from the intensity of the 4.44 MeV peak, which appears brighter by at least 20%–30% than the intensity expected from the sole α+9Be →n+12C∗reaction. A preliminary analysis24 suggests that the peak may also originate from the inelastic scattering of DT neutrons on 12C nuclei which, at JET, are found in some components of the device, for example, in the divertor tiles. The effect was particularly relevant for the JET vertical gamma-ray spectrometer,10 as its line of sight crosses the divertor. A second shortcoming was due to the gain shift of the PMT of the detector, which was found to be higher than surmised and limited good gamma-ray measurements to counting rates of some hundreds kHz, corresponding to neutron rates of a few 1017 n/s from the plasma at JET. This is lower than the valueused for the design of the ITERRGRS spectrometers, where an upper limit of few MHz was considered for the counting rate, and will have to be taken into account in the next phase of the design. A relativelystraightforwardsolution for RGRS would be to usecrystals of smaller dimensions (e.g., 1 ×1 in2, diameter x length) for the full powerphase ofITER,while largercrystals(3 ×6in2)may bekeptfor the early nuclear phases, as in the present design. However, despite theseadditionalchallenges,thesuccessofthemeasurementsofFig.1 proves that the main technical solutions envisaged for gamma-ray measurements in a DT plasma work as planned, which brings us confidence on the overall RGRS design concept for ITER. Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-3 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi III. NEUTRON SPECTROSCOPY MEASUREMENTS Neutron spectroscopy was another key diagnostics for confined fuel ion measurements in the DTE2 campaign. Two main instruments were used: the magnetic proton recoil (MPR) spectrometer25,26 onasingle tangential line of sight (LOS) andsingle crystal, synthetic diamond detectors (SDD)27,28 on few LOSes. The MPR, used also in the previous DTE1 campaign,29 measures neutrons by first converting them into protons through forwardnuclear scattering in the instrumentpolyethylenetargetand by bending the protons on a hodoscope by means of a magnet. In this way, protons originating from neutrons with different energies are dispersed at different positions on the hodoscope and the neutron energy spectrum is measured as a proton position spectrum on the hodoscope. Figure 3, top shows a typical MPR measurement in FIG. 3. (Top) Typical neutron spectrum measured by the MPR instrument in JET DTE2 (discharge No. 99965 with data integrated over the time interval t =9.25 to 9.5 s). The hodoscope position corresponding to E =14 MeV neutrons, as well as the neutron range covered by this instrument, are indicated. (Bottom) Correlation between variations of the radio frequency power (line with color filling) and the E>14 MeV neutron signal (dots) detected by the MPR in an alpha source modulation experiment. DTE2. 14 MeV neutrons show up as a peak centered at Xpos =27 cm on the hodoscope and with a broadening that is dominated by the instrument response function. There is then an (uninteresting) continuous structure at Xpos <20 cm, due to down scattered neutrons, and a high energy tail at, say, Xpos >32 cm. The latter spans three orders of magnitude down from the main 14 MeV peak and is a signature of suprathermal fuel ions born from the heating systems, for example, ICRH partly absorbed by the neutral beams and used in many discharges to enhance the fusion power and alpha particle production in DTE2. An example of application is shown in Fig. 3, bottom. Here, MPR events in the fast ion region Xpos >32 cm are FIG. 4. Main neutron emission peak measured by the JET tangential diamond detector in a DTE2 experiment aimed at testing 9Be acceleration by radio frequency heating. The shape of the peak is different depending on whether 9Be (top) or the beam (bottom) absorbs most of the power. The data come from discharges Nos. 99608 and 99613, respectively, and are integrated over the whole 4 s ICRH+NBI heating phase. The curves are a fit to the data and include components originating from thermal and beam–target fusion reactions, as well as the background contribution due to energy down scattered neutrons. The shape of each component is obtained by a semi-analytical model, with each amplitude left as a free parameter in the fit. Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-4 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi measured as a function of time and compared with a modulation of the ICRH power in discharge No. 99965. The amplitude of the MPR modulation depends on that of the ICRH power and can be used to quantify the magnitude of the fast ion source induced by the ICRH and its relative contribution to the enhancement of the alpha particle and fusion power generation from non-thermal DT reactions. The strength of the MPR is in its high dynamic range (three orders of magnitude or more) which, as in DTE1, made it possible to detect relatively small populations (<1% level) of suprathermal fuel ions in DTE2. Besides MPR measurements, SDDs have been thoroughly testedin aDTplasmafor thefirsttime in DTE2.Thedevelopment of SDDs for JET was motivated by pioneering, albeit limited, proof-of- principle measurements with natural diamonds in the DT campaign of the TFTR tokamak30 and by the opportunities offered by the advancementin theSDDgrowth technologyinthe pasttwodecades. The set of JET SDDs comprised a matrix of 12 pixels28 on a vertical line of sight, a single pixel detector (surface area of 4.7 ×4.7 mm2 ×0.5 mm thickness) behind the MPR (for a one-to-one comparison withthisinstrument)16 andafew other detectors placed closer to the machine in the torus hall, mostly for radiation hardness studies (not describedhere). In an SDD, the signal originates from elastic, inelastic and charged particle production reactions between neutrons and the 12C nuclei that make the active part of the detector. The result is a rather complex response function, where the most interesting feature is the appearance of a sharp peak at the detector “deposited” energy Edep =En−5.702 MeV from the 12C(n,α)9Be reaction. The intrinsic broadening of this peak is <1%31 so that its measured spectral shape can be almost entirely ascribed to the kinetic properties of the fuel ions. In terms of relative probability, a few percent of FIG. 5. (Top) Fishbone activity in the frequency range 14–20 kHz detected by the JET magnetic probes in dischargeNo.99643andinthetimeinterval t=8.5–9.3 s. (Bottom) Spectrogram measured by the JET FILD for the same discharge and in the same time interval. Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-5 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi the interactions with the SDD proceed through 12C(n,α)9Be. In DTE2, counting rates as high as some kHz were observed in the 12C(n,α)9Be peak region when total counting rates of some hundreds kHz were measured for the highest performance discharges, corresponding to global neutron rates of some 1018 n/s. Figure 4 shows the 12C(n,α)9Be peak shape measured in two discharges from a 3-ion scheme radio frequency experiment.32 Measured data are represented by the circles with error bars, while the curves are a fit to data for the different components of the neutron emission using a simplified semi-analytical model for the shape of each component and leaving the amplitude as a free parameter (see the caption for more details). In this experiment, ICRH was used to test the physics principles behind a scheme aimed at heating the intrinsic 9Be impurities of a DT plasma in a ITER-like wall environment. The relevance of the scheme stems from the fact that the heavy9Be nucleiheatedbyICRH are,predominantly,a sourceofion heating, which will help enhancing the fusion rate in a thermonuclear reactor, such as ITER. According to theory, the fraction of the ICRH power that is coupled to the 9Be impurities depends, among other parameters, on the D:T ratio and is maximized for a 50:50 D:T mixture, leading to enhanced thermonuclear fusion power production in this case. The difference in the peak shape measured by the SDD for the case of a 50:50 DT (top) and tritium rich (bottom) plasma is qualitatively consistent with the expectations from theory. When more 9Be heating is expected, the peak is sharper, which is due to the enhanced thermal contribution (Gaussian shaped, red solid curve) to the neutron emission. Additional power absorption by the beam is indicated by a broader peak shape, with a barely visible contribution of the thermal emission, but for the narrow region Edep =8.5–9 MeV. More generally, similarly to the gamma-ray spectroscopy measurements, the high spectral resolution of the diamond and MPR measurements may allow us to draw conclusions about the velocities of the energetic ions generating the neutrons through weight functions.33,34 For neutron spectra, also the relative weights of the fast ion orbits (co- or counter-passing, trapped, etc.) generating the neutron emission can be given.35 IV. LOST FAST ION MEASUREMENTS Lost fast ion measurements, particularly alpha particles, were also a new capability of JET DTE2 and consisted of a Fast Ion Loss Detector (FILD)36 and an array of five Faraday cups (FCs),37,38 both upgraded specifically to enable alpha particle measurements from DT. The JET FILD is available at a fixed position (on Octant 4 and 5 mm behind the nearby poloidal limiter) and measures fast ions that reach the detector through an entrance slit. Depending on their energy and pitch, the energetic ions hit the scintillator plate at different positions. A set of PMTs, as well as a charge coupled device (CCD) camera, detect the light from the scintillator and make a map of the velocity space of the fast ions that have reached the plate. Similarly to the most recent FILD installations in other tokamaks,39 the scintillator used for the JET FILD has a fast (some hundreds ns) light decay time, which opens up to the detection of the magnetohydrodynamic (MHD) instabilities that lead to the losses by a time dependent Fourier transform (spectrogram) of the measured signal, up to some tens of kHz. An example of application is shown in Fig. 5, where a spectrogram of the signal from the magnetic probes and the FILD data in an alpha particle source modulation experiment are shown. In this type of experiments, perturbations with a fast frequency down chirping, known as “fishbones,” have been often observed by the magnetic probes and these were found to lead to prompt alpha particle losses in the FILD signal. It is not yet known whether these had an impact on the overall fusion performance of the experiment and, more generally, the extent to which theMHDinstabilitieslimitedthe outcomeofsomeofthedischarges, but the data offer the unprecedented opportunity for a quantitative investigation in DT and model validation. Complementary to the FILD, the FCs allow obtaining information on the poloidal distribution of the losses. When lost alpha particles hit one of the FCs, the resulting current is measured. As each FC consists of four stacked nickel foils, some rough energy discrimination is possible as depending on their energy, lost fast ions will predominantly be stopped in one of the foils, leading to an enhanced current there and enabling a cross comparison with the detailed velocity space determination by the FILD. The poloidal distribution of the losses is indicated by the relative magnitude of the current measured by each FC. Similarly to the FILD, a frequency spectrogram of the current in each FC can be built to understand which perturbations mostly lead to fast ion losses for comparison with the instabilities measured by the magnetic probes. Figure 6 shows an example of data on fusion alpha particle losses measured by the FCs obtained in the DT discharge No. 99627. The figure compares a spectrogram of the magnetic probes (top) with that obtained from the current detected by the FC in the same poloidal position as the FILD (bottom). This is the FC which has the FIG. 6. (Top) Spectrogram of the signal detected by the JET magnetic probes in discharge No. 99627 showing a magnetic island (bright line with frequency around 20 kHz) in the time interval t =8.0–10.0 s. (Bottom) Spectrogram of the signal measured by the JET Faraday cup in the poloidal position of the FILD for the samedischarge and in thesame time interval. Thesame perturbation isobserved. Rev. Sci. Instrum. 93, 093520 (2022); doi: 10.1063/5.0101767 93, 093520-6 Published under an exclusive license by AIP Publishing 06 February 2025 15:07:02 Review of Scientific Instruments ARTICLE scitation.org/journal/rsi most intense signal, suggesting a higher flux of lost alpha particles at its poloidal position. The long lived magnetic island observed in the magnetics leads to a clear, continuous prompt loss of alpha particles, which opens up new opportunities for code validation and the understanding of the overall impact that the MHD instabilities may have in limiting plasma performance. V. CONCLUSIONS The Deuterium–Tritium Experiment 2 campaign at the Joint European Torus achieved a new fusion energy world record and also performed a broad range of physics oriented experiment whose results are presently under analysis. In the area of nuclear diagnostics for fusion products, new systems were available and collected a vast amount of data, which will be instrumental to test the predictions of the models with unprecedented level of detail. For the first time, gamma-ray spectroscopy measurements of alpha particles in magnetically confined DT fusion plasmas have been demonstrated and the high energy gamma-ray emission from DT fusion has been detected. Some unplanned limitations of the detectors were found, which prevented measurements at neutron rates higher than some 1017 n/s, but also provided important information to revise some designchoicesofthegamma-raydiagnosticsplannedforITER.Neutron spectroscopy measurements with the magnetic proton recoil spectrometer were re-established and were complemented by data from a set of synthetic diamond detectors for the first time. These were key, for example, to assess the relative fraction of thermal and supra-thermal emission in novel radio frequency heating experiments. Finally, lost fast ion diagnostic capabilities were available for the first time in JET DT plasmas. In particular, a fast ion loss detector, for measurements of the velocity space of the escaping alpha particles, and a set of five Faraday cups, for the reconstruction of the spatial distribution of the losses, were used. The spectrogram of the signal detected by both instruments showed the impact that low frequencyMHD instabilitieshadonthe alphaparticlelosses in manyof the discharges and may be used to assess whether the MHD instabilities limited the performance of some discharges by a more detailed analysis. ACKNOWLEDGMENTS This work was 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 expressedare, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Commission. Neither the EuropeanUnion northeEuropean Commission canbeheld responsible for them. This scientific paper has been published as part of the international project co-financed by the Polish Ministry of Science and Higher Education within the programme called “PMW” for 2021. AUTHOR DECLARATIONS Conflict of Interest The authors have no conflicts to disclose. Author Contributions M. Nocente: Conceptualization (lead); Data curation (lead); Formal analysis (equal); Investigation (equal); Methodology (equal); Writing – original draft (lead); Writing – review & editing (lead). V. Kiptily: Data curation (equal); Formal analysis (supporting); Investigation (equal); Validation (equal). M. Tardocchi: Funding acquisition (equal); Investigation (supporting); Methodology (equal). P. J. Bonofiglo: Data curation (supporting); Validation (supporting). T. Craciunescu: Funding acquisition (supporting); Project administration (supporting). A. Dal Molin: Data curation (supporting); Validation (supporting). E. De La Luna: Investigation (supporting); Project administration (supporting). J. Eriksson: Data curation (supporting); Formal analysis (supporting); Validation (supporting). J. Garcia: Investigation (supporting); Project administration (supporting). Z. Ghani: Supervision (supporting); Validation (supporting). G. Gorini: Funding acquisition (supporting); Project administration (supporting). L. Hägg: Data curation (supporting); Validation (supporting). Y. Kazakov: Investigation (equal). E. Lerche: Investigation (supporting). C. F. Maggi: Investigation (supporting); Project administration (supporting). P. Mantica: Investigation (supporting). G. Marcer: Data curation (supporting); Formal analysis (supporting); Validation (supporting). M. Maslov: Investigation (supporting). O. Putignano: Data curation (supporting). D. Rigamonti: Data curation (supporting); Formal analysis (supporting); Validation (supporting). M.Salewski: Investigation (supporting); Writing – review & editing (supporting). S. Sharapov: Investigation (supporting). P. Siren: Data curation (supporting). Z. Stancar: Formal analysis (supporting). A. Zohar: Formal analysis (supporting); Validation (supporting). P. Beaumont: Data curation (supporting). K. Crombe: Data curation (supporting). G.Ericsson: Project administration (supporting). M.Garcia-Munoz:Projectadministration(supporting).D.Keeling: Investigation (supporting). D. King: Investigation (supporting). K. Kirov: Formal analysis (supporting). M. F. F. Nave: Conceptualization (supporting). J. Ongena: Conceptualization (supporting). A. Patel: Data curation (supporting). C. Perez von Thun: Data curation (supporting). DATA AVAILABILITY The data that support the findings of this study are available from the corresponding author upon reasonable request. REFERENCES 1J. Mailloux, “Overview of JET results for optimising ITER operation,” Nucl. Fusion 62, 042026 (2022). 2E. Joffrin, S. Abduallev, M. Abhangi, P. Abreu, V. Afanasev, M. Afzal, K. M. Aggarwal, T. Ahlgren, L. Aho-Mantila, N. Aiba et al., “Overview of the JET preparation for deuterium–tritium operation with the ITER like-wall,” Nucl. Fusion 59(11), 112021 (2019). 3J. Figueiredo, A. Murari, C. Perez Von Thun, D. Marocco, M. 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