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The Joint European Torus (JET) fusion reactor was upgraded to the metallic wall configuration in 2011 which consisted of bulk beryllium (Be) tiles in the main chamber and bulk tungsten (W) and W-coated CFC tiles in the divertor (Matthews G.F. et al 2011 Phys. Scr. T148 014001). During each campaign, a series of wall damages were observed; on the upper dump plates (UDP) positioned to the top part of the vessel walls and on the inner wall—mainly affecting the inner wall guard limiters (IWGL). In both cases, it was concluded that the causes of these damages were unmitigated plasma disruptions. In the case of JET with the metallic wall configuration, most of these plasma disruptions were intentionally provoked. The overall objective was to study the behaviour of these phenomena, in order to assess their impact on the wall, improve understanding of morphological material changes, and—based on that—to develop, implement and test mitigation techniques for their prospective use on ITER. The current results bring additional information on the effects of the unmitigated plasma disruptions on the UDPs and are a significant extension of work presented in (Jepu et al 2019 Nucl. Fusion 59 086009) where the scale of the damage after three operational campaigns on the Be top limiters of JET was highlighted. In addition, new data is presented on the damaging effect that the high energetic runaway electrons had on the Be IWGL in JET., QC 20240926

Within the 9th European Framework programme, since 2021 EUROfusion is operating five tokamaks under the auspices of a single Task Force called ‘Tokamak Exploitation’. The goal is to benefit from the complementary capabilities of each machine in a coordinated way and help in developing a scientific output scalable to future largre machines. The programme of this Task Force ensures that ASDEX Upgrade, MAST-U, TCV, WEST and JET (since 2022) work together to achieve the objectives of Missions 1 and 2 of the EUROfusion Roadmap: i) demonstrate plasma scenarios that increase the success margin of ITER and satisfy the requirements of DEMO and, ii) demonstrate an integrated approach that can handle the large power leaving ITER and DEMO plasmas. The Tokamak Exploitation task force has therefore organized experiments on these two missions with the goal to strengthen the physics and operational basis for the ITER baseline scenario and for exploiting the recent plasma exhaust enhancements in all four devices (PEX: Plasma EXhaust) for exploring the solution for handling heat and particle exhaust in ITER and develop the conceptual solutions for DEMO. The ITER Baseline scenario has been developed in a similar way in ASDEX Upgrade, TCV and JET. Key risks for ITER such as disruptions and run-aways have been also investigated in TCV, ASDEX Upgrade and JET. Experiments have explored successfully different divertor configurations (standard, super-X, snowflakes) in MAST-U and TCV and studied tungsten melting in WEST and ASDEX Upgrade. The input from the smaller devices to JET has also been proven successful to set-up novel control schemes on disruption avoidance and detachment., QC 20240926

A characterization of plasma parameters and neutral particle energies and fluxes has been performed for radio frequency and microwave discharges in the Toroidal Magnetized System (TOMAS). A movable triple Langmuir probe was used to study the electron densities and temperatures, and a time-of-flight neutral particle analyzer was used to measure the energy and fluxes of neutral particles, as a function of the total injected power and the antenna frequency used to generate the plasma. The experimental results can provide information on the behavior of neutral particles at low energies in wall conditioning plasmas., QC 20240906

Efficient Electron Cyclotron Resonance Heating (ECRH) breakdown and pre-ionization can be achieved with fundamental X-mode, while higher harmonics can introduce excessive stray radiation. Fundamental heating however is characterized by a low cut-off density, introducing additional power absorption mechanisms in the plasma. A good knowledge of these mechanisms is necessary to use fundamental X-mode as an efficient pre-ionization method. Numerous experiments were performed on the TOroidally MAgnetized System (TOMAS) to study the power deposition for ECRH in helium. It is a facility designed to study plasma production, wall conditioning and plasma-surface interactions and is operated by LPP-ERM/KMS at the FZ-J & uuml;lich. The influence of the injected power P EC and the magnetic field B 0 on the absorption mechanisms is examined, in order to reduce stray radiation and improve the absorption efficiency. This will allow to determine the best scenarios for plasma start-up and pre-ionization., QC 20240820

To improve the plasma performance and control the density and plasma quality during the flat top phase, wall conditioning techniques are used in large fusion devices like W7-X and in JT60-SA. To study the performance of electron cyclotron wall conditioning, numerous experiments were performed on the TOroidally MAgnetized System, which is operated by LPP-ERM/KMS at the FZ-Jülich. It is a facility designed to study plasma production, wall conditioning, and plasma-surface interactions. The produced electron cyclotron resonance heating plasmas are characterized in various conditions by density and temperature measurements using a movable triple Langmuir probe in the horizontal and the vertical direction, complemented by video and spectroscopic data, to obtain a 2D extrapolation of the plasma parameters in the machine. A way to calibrate the triple Langmuir probe measurements is also investigated. These data can be used to determine the direction of the plasma drift in the vessel and identify the power absorption mechanisms. This will give more insight in the plasma behavior and improve the efficiency of wall conditioning and sample exposure experiments., QC 20240612

Polycrystalline (PC) and single crystal (SC) molybdenum mirrors were irradiated with 98Mo+, 1H+, 4He+, 11B+ and 184W+. Energies were chosen to impact the optically active region (up to 30 nm deep) of Mo mirrors. Some surfaces were coated by magnetron sputtering either with B or W films 4–65 nm thick. The overall objective was to simulate the neutron-induced damage and transmutation (H, He), and the impact of H, He, B, W on the optical performance of test mirrors, and on fuel retention. In parallel, a set of PC Mo mirrors irradiated with 1.6 MeV 98Mo3+ to a damage of 2 dpa and 20 dpa was installed in the JET tokamak for exposure during deuterium-tritium campaigns. Data from spectrophotometric, ion beam and microscopy techniques reveal: (i) the irradiation decreased specular reflectivity, whereby the differences between PC and SC in reflectivity are very small, (ii) He is retained in bubbles within 25–30 nm of the subsurface layer in all irradiated materials, (iii) W, either deposited or implanted, decreases reflectivity, but the strongest reflectivity degradation is caused by B deposition. Laboratory studies show the correlation of damage and H retention. Several cycles of W deposition and its removal from SC-Mo mirrors by plasma-assisted methods were also performed., QC 20231218

Electron Cyclotron Heating (ECH) at the fundamental resonance in X-mode is limited by a low cut-off density. Electromagnetic waves cannot propagate in the region between this cut-off and the Upper Hybrid Resonance (UHR) and cannot reach the Electron Cyclotron Resonance (ECR) position. Higher harmonic heating is hence preferred in nowadays ECH plasma heating scenarios to overcome this problem. However, if this evanescent region is small compared to the wavelength of the waves, additional power deposition mechanisms can occur to increase the plasma density. This includes collisional losses in the evanescent region, tunneling of the X-wave with resonant coupling at the ECR, and conversion to the Electron Bernstein Wave (EBW) with resonant coupling. Several ECH plasma production experiments were performed on the TOMAS device with simple toroidal magnetic field to identify these additional heating regimes and to study the influence of the heating power on the ECH plasma parameters and the power deposition. Density and temperature profiles were measured with Langmuir Probes. Measurements of the forwarded and reflected power allow to estimate the coupling efficiency. The results help to understand ECH plasma production for tokamak plasma breakdown assistance and Electron Cyclotron Wall Conditioning (ECWC)., QC 20231206

The plasma electron density and temperature were measured in hydrogen electron-cyclotron resonance (ECR) plasma and combined ECR + radio-frequency (RF) discharges in the TOMAS facility. The results of ECR and combined ECR+RF discharges studies are compared. With an addition of RF, it is possible to vary the plasma parameters around the values provided by the ECR discharge. The propagation of slow (SW) and fast (FW) waves in hydrogen plasma is analyzed. Depending on the plasma density and the parallel component of the wave vector three cases are possible: SW propagation only, SW and FW simultaneous propagation, and FW propagation only., QC 20231207

The study of discharge initiation by an Ion Cyclotron Range of Frequency (ICRF) antenna is of importance for operational scenarios at low magnetic field in e.g., ITER and Wendelstein 7-X. At low magnetic fields ohmic breakdown is difficult because of relatively short connection lengths and the electron cyclotron (EC) systems cannot assist because of a low-density cut-off. In that case ion cyclotron (IC) start-up, with waves in the Radio Frequency (RF) wavelength range, can be a good alternative solution. To explore in more detail the processes at play during the initial breakdown phase and to test measurement requirements, the diagnostic's capabilities of the TOMAS experimental device are being enlarged to allow for IC breakdown studies. A first set of IC breakdown experiments has been performed and data was taken by a newly installed spectrometer and a horizontal triple Langmuir probe. Limitations were found in pressure, ICRF power, and hydrogen concentration. Further diagnostic's upgrades and extensions of the experimental sessions will allow for a more complete study in support of modelling and experiments on other machines., QC 20231207

To complement wall conditioning research in TOMAS, a characterisation of radio-frequency hydrogen plasmas has been performed using a radially movable triple Langmuir probe. Experimental measurements of electron temperature and density radial profiles at different magnetic field on axis strengths and neutral pressures have been performed. First results of simulations of the radial profiles with the code TOMATOR-1D can qualitatively reproduce the measurements of the diagnostic and may be used to understand the behaviour of the waves inside the plasma., QC 20231204

To measure the local ion energy distribution functions for support of Ion Cyclotron Wall Conditioning (ICWC) application studies in the TOMAS device, a Semion Retarding Field Energy Analyzer (RFEA) by Impedans Ltd. has been installed in the sample load-lock system. The RFEA system has been commissioned in hydrogen Radio-Frequency (RF) plasmas. The first studies have been performed on the influence of the neutral hydrogen pressure, the input power, the magnetic field and the location on the average ion energy and ion flux density., QC 20231204

Psychedelic substances have in recent years attracted considerable interest as potential treatments for several psychiatric conditions, including depression, anxiety, and addiction. Imaging studies in humans point to a number of possible mechanisms underlying the acute effects of psychedelics, including changes in neuronal firing rates and excitability as well as alterations in functional connectivity between various brain nodes. In addition, animal studies using invasive recordings, have suggested synchronous high-frequency oscillations involving several brain regions as another key feature of the psychedelic brain state. To better understand how the imaging data might be related to high-resolution electrophysiological measurements, we have here analyzed the aperiodic part of the local field potential (LFP) in rodents treated with a classic psychedelic (LSD) or a dissociative anesthetic (ketamine). In addition, functional connectivity, as quantified by mutual information measures in the LFP time series, has been assessed with in and between different structures. Our data suggest that the altered brain states of LSD and ketamine are caused by different underlying mechanisms, where LFP power shifts indicate increased neuronal activity but reduced connectivity following ketamine, while LSD also leads to reduced connectivity but without an accompanying change in LFP broadband power.

This work was carried out to identify sources of errors, uncertainties and discrepancies in studies of fuel retention in wall components from the JET tokamak using methods based on thermal desorption. Parallel aims were to establish good practices in measurements and to unify procedures in data handling. A comprehensive program designed for deuterium quantification comprised the definition and preparation of two types of materials (samples of JET limiter Be tiles and deuterium-containing targets produced in the laboratory by magnetron-assisted deposition), their pre-characterization, quantitative analyses of the desorption products in three different thermal desorption spectroscopy systems and a detailed critical comparison of the results. Tritium levels were also determined by several techniques in samples from JET and in tritiated targets manufactured specifically for this research program. Facilities available for studies of Be- and tritium-contaminated materials from JET are presented. Apparatus development, future research options and challenges are discussed., QC 20230824

In the TOMAS device, a triple Langmuir probe is used to measure the electron temperature and density. The accuracy of this measurement depends on correct determination of the effective collecting area of the probe, which depends on complex plasma transport processes. The probe can be calibrated by electron cyclotron resonance heating experiments using the cut-off density of the ordinary wave (O-wave). This threshold only depends on the frequency of the injected wave, and the occurrence of this phenomenon is clearly visible in the temperature evolution. The value of density is consequently known at this point and can be used to calibrate the density measurements of the triple Langmuir probe., QC 20230630

Sputter-deposited thin films (33-1160 nm) from EUROFER97 were obtained on different substrates (C, Si, W, MgO) in argon and a mix of argon and deuterium atmosphere. The composition, microstructure, and mechanical properties of the films were analyzed and compared to those of the bulk material. The films feature lower density (-10%), higher hardness (+79%), and smaller crystallites in comparison to the bulk. Despite such differences, the elemental atomic composition of the films and the bulk was very similar, as determined by ion beam analysis. Deposition in deuterium-containing atmosphere resulted in a low deuterium incorporation (0.28% of atomic content), indicating low retention of hydrogen-isotopes in the deposited material., QC 20230607

Det svenska lantbruket är bara en av många näringar i Sverige där kostnaderna för verksamheten har ökat kraftigt den senaste tiden. Detta har gjort att många lantbrukare har det tuffare rent ekonomiskt när det kommer till investeringar. För dikoproducenter är det redan tufft sen innan då inkomsterna kontra utgifterna är relativt lika. För att dikoproducenterna ska få det bättre ekonomiskt bör de undersöka andra sätt om hur de kan hålla djuren under vinterperioden. Utedrift utan ligghall är ett bra och ekonomiskt djurhållningssystem för lantbrukare förutsatt att de har rätt marker till det. I detta arbete kommer den som är intresserad av utedrift utan ligghall få ta del utav information gällande utedrift utan ligghall samt djurhållning i byggnader. Det kommer att presenteras två kvantitativa undersökningar som har gjorts för vartdera system via enkäter. Utifrån undersökningen får man ta del utav arbetsbehovet för varje system samt vissa ekonomiska aspekter exempelvis investeringskostnad för byggnaden respektive för stängslet. Bland de viktigaste resultaten är att arbetstiden för den dagliga skötseln av dikor i utedrift utan ligghall i medeltal tar 1,8 minuter per diko och dag under vinterperioden och 2 minuter per diko och dag för system med djurstall. Det är stor variation i arbetstid mellan minsta och högsta arbetstid för båda systemen. Det ska också nämnas att det var stor variation för investeringskostnaden per dikoplats för de olika systemen. Systemet som hade högst investeringskostnad per dikoplats var ett system med byggnader med en kostnad på 47 095 kr medan ett system med utedrift utan ligghall hade en kostnad på 3 900 kr per diko. Slutsatsen är att det är mer ekonomiskt att ha utedrift utan ligghall eftersom investeringskostnaden är lägre per djur jämfört kostnaden som är för djur som hålls i djurstall. Dessutom kan lantbrukare som har utedrift kan spara tid med sitt system jämfört om de skulle ha djuren i en byggnad då de har färre arbetsmoment kring djure, Swedish agriculture is just one of many industries in Sweden where the costs of operations have increased sharply recently. This has meant that many farmers have a tougher financial time when it comes to investments. For beef cow producers, this is already tough since before due to the income versus expenses are relatively equal. For the beef cow producers to be better off financially, they should check other ways about how they can keep the animals during the winter period. Ranching without any buildings is a good and economical animal husbandry system for farmers, provided they have the right land for it. In this work anyone who is interested in ranching without any buildings will be able to take part in information regarding ranching without any buildings and keeping animals in buildings. Two quantitative studies have been done for each system with the help of surveys. Based on the surveys, one can take part in the work requirements for each system as well as certain financial aspects such as the investment cost of the building compared with the fence. Among the most important results is that the working time for the daily care of the cows in outdoor operation without a lying shed takes an average of 1,8 minutes per cow and day during the winter period and 2 minutes per cow and day för systems with animal stalls. There is a large variation in working hours between the minimum and maximum working hours for both systems. It should also be mentioned that there was a large variation in the investment cost per cow place for the different systems. The system with the highest investment cost per cow place was a system with buildings with a cost of 47 095 SEK, while an outdoor operation without a lying shed had a cost of 3 900 SEK per cow. The conclusion is that it is more economical to have a ranch without any buildings. As the cost is lower per animal compared to the cost of animals kept in buildings. And that the farmers that have this kind of system can save time com

Tremor can be highly incapacitating in everyday life and typically fluctuates depending on motor state, medication status as well as external factors. For tremor patients being treated with deep-brain stimulation (DBS), adapting the intensity and pattern of stimulation according the current needs therefore has the potential to generate better symptomatic relief. We here describe a procedure for how patients independently could perform self-tests in their home to generate sensor data for on-line adjustments of DBS parameters. Importantly, the inertia sensor technology needed exists in any standard smartphone, making the procedure widely accessible. Applying this procedure, we have characterized detailed features of tremor patterns displayed by both Parkinson's disease and essential tremor patients and directly compared measured data against both clinical ratings (Fahn-Tolosa-Marin) and finger-attached inertia sensors. Our results suggest that smartphone accelerometry, when used in a standardized testing procedure, can provide tremor descriptors that are sufficiently detailed and reliable to be used for closed-loop control of DBS.

It has been hypothesized that to perform sensorimotor transformations efficiently, somatosensory information being fed back to a particular motor circuit is organized in accordance with the mechanical loading patterns of the skin that result from the motor activity generated by that circuit. Rearrangements of sensory information to different motor circuits could in this respect constitute a key component of sensorimotor learning. We here explored whether the organization of tactile input from the plantar forepaw of the rat to cortical and striatal circuits is affected by a period of extensive sensorimotor training in a skilled reaching and grasping task. Our data show that the representation of tactile stimuli in terms of both temporal and spatial response patterns changes as a consequence of the training and that spatial changes particularly involve the primary motor cortex. Based on the observed reorganization, we propose that reshaping of the spatiotemporal representation of the tactile afference to motor circuits is an integral component of the learning process that underlies skill acquisition in reaching and grasping.

The paper provides a concise overview of ion beam analysis methods and procedures in studies of materials exposed to fusion plasmas in controlled fusion devices with magnetic confinement. An impact of erosion-deposition processes on the morphology of wall materials is presented. In particular, results for deuterium analyses are discussed. Underlying physics, advantages and limitations of methods are addressed. The role of wall diagnostics in studies of material migration and fuel retention is explained. A brief note on research and handling of radioactive and beryllium-contaminated materials is also given., QC 20220420

An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low-Z impurity profiles. The L-H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma beta. The enhanced D- alpha H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfven turbulence, an analytic mod, QC 20220406

The microstructure of Mo was significantly refined by high pressure torsion to verify its irradiation tolerance in comparison with its micrograined counterpart. After deformation microhardness increased from 231 Hv0.2 for a microgarined sample to 542 and 558 Hv0.2, respectively after one and five rotations. Concurrently, the grain refinement was observed, as the grain size decreased with the increase of the deformation degree down to 480 and 110 nm, respectively for one and five rotations. Subsequently, deformed Mo and a micrograined one were irradiated by He ions to the dose of 8 x 1016/cm 2 to verify their potential application as fusion mirrors. Irra-diations were followed by reflectivity measurements in the 300-2400 nm range with a dual beam spectrometer. The measurements revealed that the applied dose causes a decrease in total reflectivity of the micrograined sample, whereas the total reflectivity of deformed samples decreases by additional 2.5%. Nanohardness mea-surements, detailed microscopy observations using focused ion beam and scanning transmission electron mi-croscope as well as positron annihilation spectroscopy investigations were performed to elucidate changes in the microstructure and understand the different mechanisms of bubble creation after irradiation in micrograined and high pressure torsion processed samples., QC 20221122

Silicon plates were installed above the inner and outer divertor of the JET with the ITER-like wall (ILW) after the second and third ILW campaigns to monitor dust generation and deposition with the aim to determine the morphology and content of individual particles and co-deposits, including deuterium content. Particular interest was in metal-based particles: Be, W, steel, Cu. Ex-situ examination after two ILW campaigns was performed by a set of microscopy and ion beam methods including micro-beam nuclear reaction analysis and particle-induced X-ray emission. Different categories of Be-rich particles were found: co-deposits peeled-off from plasma-facing components (PFC), complex multi-element spherical objects, and solid metal splashes and regular spherical droplets. The fuel content on the two latter categories was at the level of 1 x 10(16) at/cm(-2) indicating that Be melting and splashing occurred in the very last phase of the second experimental campaign. The splashes adhere firmly to the substrate thus not posing risk of Be dust mobilisation. No tungsten droplets were detected. The only W-containing particles were fragments of tungsten coatings from the divertor tiles., QC 20230109

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 (alpha) 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., QC 20230920

Background: Large-scale microelectrode recordings offer a unique opportunity to study neurophysiological processes at the network level with single cell resolution. However, in the small brains of many experimental animals, it is often technically challenging to verify the correct targeting of the intended structures, which inherently limits the reproducibility of acquired data. New method: To mitigate this problem, we have developed a method to programmatically segment the trajectory of electrodes arranged in larger arrays from acquired CT-images and thereby determine the position of individual recording tips with high spatial resolution, while also allowing for coregistration with an anatomical atlas, without pre-processing of the animal samples or post-imaging histological analyses. Results: Testing the technical limitations of the developed method, we found that the choice of scanning angle influences the achievable spatial resolution due to shadowing effects caused by the electrodes. However, under optimal acquisition conditions, individual electrode tip locations within arrays with 250 µm inter-electrode spacing were possible to reliably determine. Comparison to existing methods: Comparison to a histological verification method suggested that, under conditions where individual wires are possible to track in slices, a 90% correspondence could be achieved in terms of the number of electrodes groups that could be reliably assigned to the same anatomical structure. Conclusions: The herein reported semi-automated procedure to verify anatomical targeting of brain structures in the rodent brain could help increasing the quality and reproducibility of acquired neurophysiological data by reducing the risk of assigning recorded brain activity to incorrectly identified anatomical locations., The tools developed in this study are freely available as a software package at: https://github.com/NRC-Lund/ct-tools

Divertor tiles from the COMPASS tokamak have been examined with ion beam analysis for the determination of deuterium retention and co-deposits. A novel approach was used to draw 2D deuterium retention maps at different depths and correlated to the concentrations of other elements: boron, carbon, oxygen and metals. This approach, which employs all three spatial dimensions, revealed that the deuterium retention pattern is not toroidally symmetric at different depths while the overall deuterium pattern is toroidally symmetric. Analysis of visible-light camera records disclosed that parts of the divertor were not wetted by plasma. The radial profile of deuterium in both wetted and non-wetted ( "shadowed ") divertor regions was compared to strike point positions, angle of incidence, electron temperature T-e, parallel heat flux Q(par) and ion saturation current Isat in order to find the influence of these parameters on deuterium retention. There are certain series of consecutive shots for which correlations between deuterium retention and separate plasma parameters (T-e, I-sat, Q(par)) are high. Combining the three parameters in a linear model or a power law model enabled reconstruction of the radial deuterium retention pattern. After fitting the model to one third of the data points, the deuterium retention for shadowed tiles was reproduced at the other two thirds of the data points within 20% deviation. This study shows the need for detailed tile analysis in three dimensions, the great benefits of broad statistical analysis in solving challenges in fusion, and motivates the investigation of COMPASS tiles after dismantling., QC 20220627

Titanium activation foils for neutron studies were exposed inside the JET tokamak vessel during the entire 15 months long experimental campaign with deuterium fuelling. Afterwards, it was found that the structure of some foils was only slightly affected, while others were totally or partly disintegrated into dust: flakes and powder. The analyses indicated that defects produced in materials by cutting during the sample preparation eventually lead to the degradation of the titanium crystal structure upon the exposure in JET to neutral particles including hydrogen. In some cases, a passive oxide layer on the foil surface effectively prevented the access of hydrogen, and by this protected the metal against partial or complete transformation into the titanium hydride powder., QC 20220503

In nuclear fusion reactors, plasmas are heated to very high temperatures of more than 100 million kelvin and, in so-called tokamaks, they are confined by magnetic fields in the shape of a torus. Light nuclei, such as deuterium and tritium, undergo a fusion reaction that releases energy, making fusion a promising option for a sustainable and clean energy source. Tokamak plasmas, however, are prone to disruptions as a result of a sudden collapse of the system terminating the fusion reactions. As disruptions lead to an abrupt loss of confinement, they can cause irreversible damage to present-day fusion devices and are expected to have a more devastating effect in future devices. Disruptions expected in the next-generation tokamak, ITER, for example, could cause electromagnetic forces larger than the weight of an Airbus A380. Furthermore, the thermal loads in such an event could exceed the melting threshold of the most resistant state-of-the-art materials by more than an order of magnitude. To prevent disruptions or at least mitigate their detrimental effects, empirical models obtained with artificial intelligence methods, of which an overview is given here, are commonly employed to predict their occurrence—and ideally give enough time to introduce counteracting measures., QC 20230908

Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity., QC 20230907