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The armor for future nuclear fusion reactors is one of the main areas of research due to the harsh conditions it will undergo. Thermal fatigue is one of the most serious damage, as it will cause any material to fail even if the heat and particle loads during the reactor operation are always maintained low. In this work we have compared the actual tungsten armor for ITER tokamak with a new advanced tungsten material: tungsten reinforced by tungsten fibers (Wf/W). ITER-like W has shown small intergranular cracking at heat loads similar to the ones found in other similar devices: heat flux factor of FHF = 5.2 ± 1.6 MW/m2s0.5. But at much lower number of pulses: 641 versus 105. H embrittlement by the high-energy ions of OLMAT has been postulated as one of the main reason of this relatively prompt cracking appearance. Opposed to this, the type of Wf/W studied here, Porous Matrix (PM-Wf/W), has shown no damage at the same conditions and up to 950 pulses. These results show the capabilities of OLMAT for fatigue studies in conditions relevant to a future nuclear fusion reactor. New upgrades of OLMAT will partially solve the issues found in this first phase. Future work to continue with fatigue studies will be addressed.

For the first wall (FW) of ITER, beryllium will be the plasma facing material and has to sustain high thermal, particle and neutron loads. In order to assess the synergistic effects of thermal and neutron loads in total ten Be-armored FW normal heat flux (NHF) mock-ups were produced consisting of two Be flat tiles each joined via hot isostatic pressing (HIP) to a CuCrZr heat sink and a steel support structure by different manufacturing routes to assess the most promising ones. Five of them were neutron irradiated, two at Centrum Výzkumu Řež in Czech Republic and three in the High Flux Reactor at NRG in the Netherlands. The remaining mock-ups were kept as reference. All flat-tile mock-ups had two Be-tiles and were exposed to cyclic steady state heat loads in the electron beam facilities JUDITH 1 and 2 up to a maximum power density of 3.75 MW/m2, in order to find the damaging threshold. A screening step using 1 MW/m2 was performed after finishing each loading step and after failure for direct comparison and detection of any deterioration caused by the cycling. Despite being still in the early development phase of Be joining, all mock-ups sustained the cycling up to at least 2.75 MW/m2 and clear differences in the performance of irradiated vs. non-irradiated mock-ups were observed.

Assessing the performance of the ITER design for the tungsten (W) divertor Plasma Facing Units (PFUs) in a tokamak environment is a high priority issue to ensure efficient plasma operation. This paper reviews the most recent results derived from experiments and post-mortem analysis of the ITER-grade PFUs exposed in the WEST tokamak and the associated modelling, with a focus on understanding heat loading and damage evolution. Several shaping options, sharp or chamfered leading edge (LE), unshaped or shaped blocks with a toroidal bevel as foreseen in ITER, were investigated, under steady state heat fluxes of up to 120 MW⋅m−2 and 6 MW⋅m−2 on the sharp LE and top surface of the block, respectively. A very high spatial resolution (VHR) infrared (IR) camera (0.1 mm/pixel) was used to derive the temporal and surface distribution of the temperature and heat load on the castellated tungsten blocks for different geometric alignment and plasma conditions. Photonic modelling was required to reproduce the IR measurements in particular in the toroidal and poloidal gaps of the mono-block (MB) stacks where high apparent temperatures are observed. Specular reflection is found to be the dominant emitter in these parts of the blocks. W-cracking was observed on the leading edge of the blocks already within the first phase of plasma operation, during which the divertor was equipped with unshaped PFUs, including some intentionally misaligned blocks. Numerical analysis taking into account softening processes and mechanical stresses, revealed brittle failure due to transients as the dominant failure mechanisms. Ductile failure was observed in one particular block used for the melting experiment, therefore under extremely high steady state heat load conditions. W-melting achieved on actively cooled PFU exhibits specific features: shallow melting and slow melt displacement. Plasma exposure of pre-damaged PFUs at various damage levels (crack network and melted droplets) was carried out under high heat load conditions with several hours of cumulated plasma duration. IR data and preliminary surface analyses show no evidence of significant degradation damage progression under these conditions.

Wendelstein 7-X, the world’s largest superconducting stellarator in Greifswald (Germany), started plasma experiments with a water-cooled plasma-facing wall in 2022, allowing for long pulse operation. In parallel, a project was launched in 2021 to develop a W based divertor, replacing the current CFC divertor, to demonstrate plasma performance of a stellarator with a reactor relevant plasma facing materials with low tritium retention. The project consists of two tasks: Based on experience from the previous experimental campaigns and improved physics modelling, the geometry of the plasma-facing surface of the divertor and baffles is optimized to prevent overloads and to improve exhaust. In parallel, the manufacturing technology for a W based target module is qualified.This paper gives a status update of project. It focusses on the conceptual design of a W based target module, the manufacturing technology and its qualification, which is conducted in the framework of the EUROfusion funded WPDIV program. A flat tile design in which a target module is made of a single target element is pursued. The technology must allow for moderate curvatures of the plasma-facing surface to follow the magnetic field lines. The target element is designed for steady state heat loads of 10 MW/m2 (as for the CFC divertor). Target modules of a similar size and weight as for the CFC divertor are assumed (approx.

For a future commercial fusion reactor, the joining of tungsten and steel will be of vital importance, covering the main part of the plasma facing area. However, the large difference, of more than a factor of 2, in the coefficient of thermal expansion (CTE) of W and steel results in high thermal stresses at their interface. The cyclic nature of the operation can cause fatigue effects and could result in a premature failure of the joint.One possible solution is the insertion of a functionally graded material (FGM), with varying the CTE, as an interlayer between tungsten and steel, which could reduce these stresses. In this study, two processes, atmospheric plasma spraying (APS) and spark plasma sintering (SPS), are utilized to manufacture such FGMs. The gradation was accomplished by using two or three layers with a thickness of 0.5 mm each.Another principle is the insertion of a ductile metal interlayer, which reduces the stress by plastic deformation. Vanadium and titanium foils of varying thickness were chosen, as both have a CTE in between W and steel and V forms a solid solution with W and Fe. These and a direct W-steel joint as baseline reference were made by current-assisted diffusion bonding. All samples consist of 3 mm thick W and steel tiles allowing a direct comparison of the different technologies.An efficient high heat flux benchmark test procedure was developed and performed to investigate and compare the potential of the different joining technologies. For this, the complete stacks were brazed on actively cooled copper cooling modules and tested with high stationary heat loads of up to 5 MW/m2 with 200 cycles at each level in the JUDITH 2 facility. Detailed thermal analysis including comparison with prediction based on FEM simulation are presented to understand the cause of the failure and track the degradation. This study allows to help focusing the further development of W-steel joining technologies.

The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation in a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with a focus on testing the ITER actively cooled W divertor in tokamak conditions. Following the successful completion of phase 1 (2016-2021), phase 2 started in December 2022 with the lower divertor made entirely of actively cooled ITER-grade tungsten mono-blocks. A boronization prior the first plasma attempt allowed for a smooth startup with the new divertor. Despite the reduced operating window due to tungsten, rapid progress has been made in long pulse operation, resulting in discharges with a pulse length of 100 s and an injected energy of around 300 MJ per discharge. Plasma startup studies were carried out with equatorial boron nitride limiters to compare them with tungsten limiters, while Ion Cyclotron Resonance Heating assisted startup was attempted. High fluence operation in attached regime, which was the main thrust of the first campaigns, already showed the progressive build up of deposits and appearance of dust, impacting the plasma operation as the plasma fluence increased. In total, the cumulated injected energy during the first campaigns reached 43 GJ and the cumulated plasma time exceeded 5 h. Demonstration of controlled X-Point Radiator regime is also reported, opening a promising route for investigating plasma exhaust and plasma-wall interaction issues in more detached regime. This paper summarises the lessons learned from the manufacturing and the first operation of the ITER-grade divertor, describing the progress achieved in optimising operation in a full W environment with a focus on long pulse operation and plasma wall interaction.

The evaluation of the impact of plasma-facing units (PFUs) damage on subsequent plasma operation is an important issue for ITER. This is one of the topic addressed by the operation of dedicated PFUs in WEST. From the start of WEST in 2017, few ITER grade divertor PFUs were tested in the lower divertor for short plasma exposure (experimental campaigns C1–C5). A PFU is an assembly of tungsten blocks on CuCrZr tube via pure copper interlayer. Since 2022, WEST operates with a lower divertor fully equipped with ITER grade PFUs (experimental campaign C6–C7) with long duration plasma exposure capabilities. To test the ageing of the ITER-grade PFUs on an accelerated basis, well controlled damage was implemented on purpose with electron beam loading on the plasma facing surface of two different PFUs (pre-damage#1 and #2 featuring different level of damage). Damage tackled in this study is induced by the loading with numerous transient heat loading events to mimic the ELM impact on the ITER grade PFU. This paper presents the damage before and after WEST plasma exposure and shows the tungsten sources and temperature of the block measured during the operation. On damaged area, surface roughening is heterogeneous. With WEST campaigns (C3, C4 and C7) respectively ended in (2018, 2019 and 2023) a global smoothing of the pre-damaged surfaces, in particular those located in the high loaded erosion area, is observed. No evolution of the crack is observed in the electron beam loaded area, while new cracking are observed on non pre-damaged area on the tungsten top surfaces in highly loaded areas (outer strike point) after significant plasma duration and cumulated energy (first observation in C4 and tends to be confirmed with preliminary observations after the C7 campaign). Smoothing is less pronounced after the 2018 campaign, which may be due to the related short plasma duration. The surface smoothing of blocks also depends on their poloidal position. For PFU which has no shaping, toroidal positioning within a block has no influence on the surface smoothing. After 2019 and 2023 campaigns, equivalent relative smoothing is obtained (between 19 and 32%). For the explored plasma conditions, damage has no influence on the maximum brightness of W.

Abstract We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays.

Abstract The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between $$2\times 10^{17}$$ 2×1017 and $$2\times 10^{18}$$ 2×1018 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at $$10^{{17.5}}\, {\mathrm{eV}} $$ 1017.5eV and $$10^{{18}}\, {\mathrm{eV}} $$ 1018eV . We find that, for the models to explain the data, an increase in the muon density of $$38\%$$ 38% $$\pm 4\% (12\%)$$ ±4%(12%) $$\pm {}^{21\%}_{18\%}$$ ±18%21% for EPOS-LHC, and of $$50\% (53\%)$$ 50%(53%) $$\pm 4\% (13\%)$$ ±4%(13%) $$\pm {}^{23\%}_{20\%}$$ ±20%23% for QGSJetII-04, is respectively needed.

Tungsten is an outstanding material and due to its properties like highest melting point and tensile strength of all natural metals and its high thermal conductivity it is a prime candidate for being used in very harsh environments and for challenging applications like X-ray tubes or as plasma facing material (PFM) in fusion reactors. Unfortunately, high brittle to ductile transition temperature and hardness represent a great challenge for classic manufacturing processes. Additive manufacturing (AM) of tungsten could overcome these limitations and resulting design restrictions. However, AM of tungsten also poses challenges in particular related to the production of material of high density and mechanical stability. Using a selective electron beam melting and a base temperature of 1000 °C of the powder, we were able to produce tungsten with a theoretical density of 99 % without the need of any post-treatment like a second melting step or a redensification by e.g. hot isostatic pressing (HIP). The surface morphology, microstructure, hardness, thermal conductivity and stability against severe transient heat loads were investigated with respect to the relevant building parameters and compared with recrystallized standard W. Besides simple test geometries also more sophisticated ones like monoblocks were successfully realized illustrating the potential of AM for fusion.

A micro-structuring of the tungsten plasma-facing surface can strongly reduce near surface thermal stresses induced by ELM heat fluxes. This approach has been confirmed by numerical simulations with the help of ANSYS software. For experimental tests, two 10 × 10 mm2 samples of micro-structured tungsten were manufactured. These consisted of 2000 and 5000 vertically packed tungsten fibres with dimensions of Ø240 µm × 2.4 mm and Ø150 µm × 2.4 mm, respectively. The 1.2 mm bottom parts of the fibres are embedded in a copper matrix. The top parts of the fibres have gaps about of 10 µm so they are not touching each others. The top of all tungsten fibres was electro-polished. A Nd:YAG laser with a pulse duration 1 ms and a pulse repetition frequency of 25 Hz was used to simulate up to 105 ELM-like heat pulses. No damage on either of the micro-structured tungsten samples were observed. Neon plasma erosion rate and fuel retention of the micro-structured tungsten samples were almost identical to bulk tungsten samples. Keywords: Micro-structured tungsten, PFC, PFM, High heat load, Thermal cycling, Retention, Erosion, Emissivity

The plasma facing first wall in ITER will be armored with beryllium. During operation, the armor has to sustain direct plasma contact during the start-up and ramp-down of the plasma. On top, transient thermal loads originating from a variety of plasma instabilities or mitigation systems are impacting the 8–10 mm thick beryllium tiles. In this work, possible armor thickness losses caused by the expected transient heat loads are reviewed. Applying conservative assumptions, vertical displacement events can cause locally a melt layer with a thickness of up to 3 mm. However, cracks after solidification/cool down are confined to the melt layer and the connection between melt layer and bulk remains strong. Radiative cooling mechanisms can be applied to significantly decrease the melt and evaporation layer thickness. To mitigate the critical damage potential of plasma disruptions, massive gas injections or shattered pellet injections can be deployed to transform the stored plasma energy into radiation, which implies a much more homogeneous distribution of energy to the plasma facing components. For a full power plasma discharge in ITER, these radiative loads can cause temperatures exceeding the melting temperature of beryllium. Experiments have demonstrated that a thickness of 340 µm at the entire first wall armor can be affected by these mechanisms over the lifetime of ITER. Edge localized modes with expected characteristics obtained by fluid model simulations caused fatigue cracks with a depth of up to 350 µm in experimental simulations. The critical heat flux factor FHF above which inflicted damage accumulates with each subsequent pulse has been determined to be in the range of FHF ≈ 9–12 MW m−2 s0.5. The damage from thermal loads below this threshold saturates between 104 and 106 pulses. Neutron irradiation has a deteriorating effect on the thermomechanical properties of beryllium, which strongly influence its resistance against thermally induced damages. The rather low neutron fluence over the lifetime of ITER is expected to reduce the material strength and thermal conductivity by a few tens of percents. If the thickness losses are affected to a similar extent, a sufficient margin of armor thickness will remain. Overall, the damage imposed by radiative loads from massive gas injections or shattered pellet injections is expected to be the dominant force influencing the condition of the first wall armor, at least if all disruptions can be successfully mitigated and the number of vertical displacement events can be constrained to a few occurrences over the service time of ITER. Keywords: ITER, First wall, Plasma facing materials, Beryllium, Erosion, Transient thermal load, ELMs, Massive gas injections, Shattered pellet injections

Micro structured tungsten is a new approach to address one of the main issues of tungsten as high heat flux (HHF) plasma facing material (PFM), which is its brittleness and its propensity to crack formation under pulsed, ELM like, heat loads (Loewenhoff et al., 2015; Wirtzet al., 2015 [2,3]). With power densities between 100 MW/m2 and 1 GW/m2, progressive thermal fatigue induced damages like roughening, subsequent cracking and even melting will occur in dependence on the pulse number and PFM base temperature. This represents a serious issue for the usage of tungsten as HHF-PFM. In future tokamaks, such as ITER, about 108 ELMs are expected to occur during the operational lifetime.Several approaches have been tried to overcome this brittleness issue, e.g. alloying tungsten with others elements (Linsmeier et al., 2017 [4]) or introducing pseudo-ductility due to the additions of fibres thus creating composites (Reiser et al., 2017 [5]). Micro-structured tungsten showed a significant improvement in comparison with any of these approaches with respect to the damage expected by ELMs. This investigation on both bulk reference and micro-structured tungsten was performed in the PSI-2 facility (Kreter et al., 2015 [8]). A sequential load was applied combining steady state deuterium plasma (5.1 × 1025 D + m−2, 51 eV, 240 °C, 150 min) loading with laser pulses (up to 105 pulses of 0.5 GW/m2, 3.6 mm spot diameter, 20 J, 1 ms pulse duration, up to 25 Hz pulse frequency). In contrast to reference bulk tungsten, none of the applied loading conditions caused any evident damage on the micro-structured tungsten. The maximum surface temperature within the loaded area measured with a fast pyrometer was increased by about 800 °C at the end of the laser exposure for the reference sample. This is related to the emissivity changes and local temperature increase caused by surface degradation. Meanwhile, the micro-structured sample did not show any change of its temperature response from the 10th to the 100 000th pulse.

Abstract Elves are a class of transient luminous events, with a radial extent typically greater than 250 km, that occur in the lower ionosphere above strong electrical storms. We report the observation of 1,598 elves, from 2014 to 2016, recorded with unprecedented time resolution (100 ns) using the fluorescence detector (FD) of the Pierre Auger Cosmic‐Ray Observatory. The Auger Observatory is located in the Mendoza province of Argentina with a viewing footprint for elve observations of 3·106 km 2, reaching areas above the Pacific and Atlantic Oceans, as well as the Córdoba region, which is known for severe convective thunderstorms. Primarily designed for ultrahigh energy cosmic‐ray observations, the Auger FD turns out to be very sensitive to the ultraviolet emission in elves. The detector features modified Schmidt optics with large apertures resulting in a field of view that spans the horizon, and year‐round operation on dark nights with low moonlight background, when the local weather is favorable. The measured light profiles of 18% of the elve events have more than one peak, compatible with intracloud activity. Within the 3‐year sample, 72% of the elves correlate with the far‐field radiation measurements of the World Wide Lightning Location Network. The Auger Observatory plans to continue operations until at least 2025, including elve observations and analysis. To the best of our knowledge, this observatory is the only facility on Earth that measures elves with year‐round operation and full horizon coverage.

Tungsten, the plasma facing material (PFM) for the divertor in ITER, must sustain severe, distinct loading conditions. This broad array of exposure conditions necessitates comprehensive experiments that cover most of the expected loading parameters to predict qualitative statements about the performance and as a consequence thereof the intended operation time. However, comprehensive experiments are inherently difficult to realize due to the fact that there is no device that is capable of simulating all loading conditions simultaneously. Nevertheless, the linear plasma device PSI-2 enables experiments combining thermal and particle exposure at the same time. In this work, sequential and simultaneous loads on pure tungsten at different base temperatures were investigated to study not only the performance of the material, but also the influence of the experimental parameters. The detailed analysis and comparison of the obtained results showed different kinds of damage depending on the loading sequence, power density, microstructure of the samples, and base temperature. Finally, samples with transversal grain orientation (T) showed the weakest damage resistance and the increase of the base temperature could not compensate the detrimental impact of deuterium.

Structural damage due to high flux particle irradiation can result in significant changes to the thermal strength of the plasma facing component surface (PFC) during off-normal events in a tokamak. Low-energy He+ ion irradiation of tungsten (W), which is currently the leading candidate material for future PFCs, can result in the development of a fiber form nanostructure, known as “fuzz”. In the current study, mirror-finished W foils were exposed to 100eV He+ ion irradiation at a fluence of 2.6 ×1024ionsm−2 and a temperature of 1200K. Then, samples were exposed to two different types of pulsed heat loading meant to replicate type-I edge-localized mode (ELM) heating at varying energy densities and base temperatures. Millisecond (ms) laser exposure done at 1200K revealed a reduction in fuzz density with increasing energy density due to the conglomeration and local melting of W fibers. At higher energy densities (∼ 1.5MJm−2), RT exposures resulted in surface cracking, while 1200K exposures resulted in surface roughening, demonstrating the role of base temperature on the crack formation in W. Electron beam heating presented similar trends in surface morphology evolution; a higher penetration depth led to reduced melt motion and plasticity. In situ mass loss measurements obtained via a quartz crystal microbalance (QCM) found an exponential increase in particle emission for RT exposures, while the prevalence of melting from 1200K exposures yielded no observable trend. Keywords: Plasma facing materials, Fuzz formation, Tungsten, ELM, ITER, Transient heat loading

DEMO is the name for the first stage prototype fusion reactor considered to be the next step after ITER. For the realization of fusion energy especially materials questions pose a significant challenge already today. Advanced materials solution are under discussion in order to allow operation under reactor conditions [1] and are already under development used in the next step devices. Apart from issues related to material properties such as strength, ductility, resistance against melting and cracking one of the major issues to be tackled is the interaction with the fusion plasma. Advanced tungsten (W) materials as discussed below do not necessarily add additional lifetime issues, they will, however, add concerns related to erosion or surface morphology changes due to preferential sputtering. Retention of fuel and exhaust species are one of the main concerns. Retention of hydrogen will be one of the major issues to be solved in advanced materials as especially composites and alloys will introduce new hydrogen interactions mechanisms. Initial calculations show these mechanisms. Especially for Helium as the main impurity species material issues arise related to surfaces modification and embrittlement. Solutions are proposed to mitigate effects on material properties and introduce new release mechanisms.

The experimental fusion reactor ITER will apply beryllium as first wall armor material. In present fusion experiments, e.g. ASDEX Upgrade, it has been detected that up to 25% of the plasma energy loss is deposited in non divertor regions during edge localized mode (ELM) events. Therefore, the impact of transient heating events on beryllium needs to be investigated to reliably predict the performance of the beryllium armor tiles under ITER operational conditions. In the present experiments, the electron beam facility JUDITH 2 was used to exert transient heat pulses with power densities of 0.14–1.0GWm−2, as they can be expected for mitigated Type 1 ELMs in ITER, pulse durations in the range of 0.08–1.0ms, and a number of pulses in the range of 103–107 on S-65 beryllium specimens that were brazed on an actively cooled copper structure. Thereby, a strong drop of the melting threshold was discovered from a heat flux factor FHF = 22–25MWm−2s0.5 for 102 pulses to FHF

The study summarizes the experimental results on fusion relevant pure heat load exposures of different tungsten products in the electron beam devices JUDITH 1 and 2. Besides steady state heat loading, up to 106 transient ELM-like pulses were applied. A detailed postmortem analysis reveals a wide and complex range of thermally-induced surface modifications and damages, such as roughening due to plastic deformation, cracking, and melting of parts of the material surface. Different industrially available tungsten products with varying thermal and mechanical properties were investigated in order to examine their influence on the thermal shock response. Furthermore, recrystallisation of the material, which will take place during long term operation, will additionally deteriorate the mechanical strength of the plasma facing material. The results show that the mechanical strength of the material has a significant influence on the formation and evolution of damage. Especially, recrystallisation and melting/resolidification will make the material more prone to thermal shock and fatigue, accelerating the evolution of damages. The combination of different material modifications/damages accompanied by the degradation of mechanical properties will have a strong impact on the plasma performance and lifetime of plasma facing materials/components. Keywords: Tungsten, Edge localized mode, Transient thermal loads, Material degradation, High pulse numbers, Recrystallisation

In the full-tungsten divertor qualification program at ITER Organization, macro-cracks, so called self-castellation were found in a fraction of tungsten monoblocks during cyclic high heat flux loading at 20MW/m2. The number of monoblocks with macro-cracks varied with the tungsten products used as armour material. In order to understand correlation between the macro-crack appearance and W properties, an activity to characterize W monoblock materials was launched at the IO. The outcome highlighted that the higher the recrystallization resistance, the lower the number of cracks detected during high heat flux tests. Thermo-mechanical finite element modelling demonstrated that the maximum surface temperature ranges from 1800 °C to 2200 °C and in this range recrystallization of tungsten occurred. Furthermore, it indicated that loss of strength due to recrystallization is responsible for the development of macro-cracks in the tungsten monoblock. Keywords: Fracture, Tungsten, ITER, Divertor, High heat flux, Recrystallization

The damage of deformed double forged pure tungsten (W) and tungsten alloyed with 5wt% tantalum (WTa5) have been studied in experimental simulations of ITER-like transient events with relevant surface heat load parameters (energy density up to 0.75MJ/m2 and the pulse duration of 0.25ms) as well as particle loads (varied in wide range from 1023 to 1027 ion/m2 s) with quasi-stationary plasma accelerator QSPA Kh-50. The plasma exposures were performed for the targets maintained at room temperature and preheated at 200°C. The surface heat loads were either with no melting of W surface or above the melting threshold. The development of surface morphology of the exposed targets as well as cracking and swelling at the surface is discussed. Surface analysis was carried out with an optical microscopy and SEM. Surface modification and development of cracks led to increases of roughness of exposed surfaces. X-ray diffraction (XRD) has been used to study the micro-structural evolution of the exposed targets. The micro deformations of W and WTa5 are similar for targets exposed under similar conditions. The contribution of excess complexes of interstitial atoms in the formation of cracks after plasma irradiation was evaluated.

Experiments were performed in the linear plasma device PSI-2 in order to investigate the synergistic effects of combined steady-state He-plasma and thermal shock exposure. Tungsten produced according to the ITER material specifications by Plansee SE, Austria, was loaded sequentially and simultaneously by steady-state He plasma and transient thermal loads induced by a laser beam. All tungsten samples were exposed to helium plasma for 40min at a base temperature of ca. 850°C and a flux of ca. 2.8×1022m−2s−1. Before, during and after the plasma exposure 1000 thermal shock pulses with a pulse duration of 1ms and a power density 0.76GW/m² were applied on the samples. The thermal shock exposure before and after plasma exposure was done at room temperature in order to investigate helium induced surface effects also within cracks. The obtained results show that the combination of He plasma with transient thermal shock events results in a severe modification such as reduced height or agglomeration of the sub-surface He-bubbles and of the created nanostructures, i.e. W-fuzz.

To investigate the synergistic effects of fuel retention in tungsten, experiments were performed in the linear plasma device PSI-2 where the transient heat loads were applied by a high energy laser during the steady-state plasma operation. The impact on the deuterium (D) retention of simultaneous and sequential exposures to laser and plasma has been investigated. A significant increase of D retention, more than a factor of 12, has been observed during the simultaneous transient heat loads and plasma exposure. Successive exposures to transient heat loads and deuterium plasma also show the increased content of D-atoms by more than a factor of 3.6 in comparison to the pure plasma loading. In both cases the increase is most likely due to enhanced hydrogen clustering by the thermal shock exposures, due to an increased mobility of D atoms along the shock-induced cracks as well as to increased diffusion of D atoms into the W material caused by strong temperature gradients during the laser pulse exposure. Comparison of the NRA and TDS measurements shows that only 34% of the retained deuterium in the tungsten specimen is located inside the near-surface layer (d

Massive gas injections (MGIs) will be used in ITER to mitigate the strong damaging effect of full performance plasma disruptions on the plasma facing components. The MGI method transforms the stored plasma energy to radiation that is spread across the vacuum vessel with poloidal and toroidal asymmetries. This work investigated the impact of MGI like heat loading on the first wall armor material beryllium. ITER-relevant power densities of 90-260MWm−2in combination with pulse durations of 5-10ms were exerted onto the S-65 grade beryllium specimens in the electron beam facility JUDITH 1. All tested loading conditions led to noticeable surface morphology changes and in the expected worst case scenario, a crater with thermally induced cracks with a depth of up to ∼340µm formed in the loaded area. The level of destruction in the loaded area was strongly dependent on the pulse number but also on the formation of beryllium oxide. The cyclic melting of beryllium could lead to an armor thinning mechanism under the presence of melt motion driving forces such as surface tension, magnetic forces, and plasma pressure.

In the current study, a solid state disc laser with a wavelength of 1030nm and maximum power of 5.3kW was used to melt the surface of pure tungsten samples (manufactured according to ITER specifications by Plansee SE). Several combinations of laser power and traverse velocity were tested, with the aim of eliminating any pre-existing cracks and forming a smooth and contiguous resolidified surface. Some of the samples were previously damaged by the electron beam simulation of 100 THLs of 0.38GW/m² intensity (Δt=1ms) on a 4×4mm² area in the JUDITH1 facility. These conditions were chosen because the resulting damage (crack network) and the crack depth (∼200–300µm) are known from previous identical material tests with subsequent cross sectioning. After laser melting, the samples were analyzed by SEM, laser profilometry and metallographic cross sectioning. A closed surface without cracks, an increased grain size and pronounced grain boundaries in the resolidified area were found. Profilometry proved that the surface height variations are within ±25µm from the original surface height, meaning a very smooth surface was achieved. These results successfully demonstrate the possibility of repairing a cracked tungsten surface by laser surface re-melting. This “laser repair” could be used to extend the lifetime of future plasma facing components.

Five samples of recrystallized pure tungsten were exposed to transient heat loads using the electron beam of the JUDITH 1 and JUDITH 2 installations of Forschungszentrum Jülich. The heat flux and base temperature were the same for all samples; only the number of pulses and exposure device differed. Transmission electron microscopy was applied to determine the first defects that are introduced during exposure and to compare the effects of the two machines. With increasing number of pulses, first dislocations are formed near the grain boundaries, and then line dislocations and clusters of dislocations appear within the grains. Upon prolonged exposure, the dislocations migrate and cluster in dislocation pile-ups. Comparing exposure in JUDITH 1 to JUDITH 2, the amount of defects is much higher in the samples exposed in JUDITH 1.

One of the numerous challenges of the demonstration power plant DEMO is the selection of appropriate plasma facing materials (PFMs) and this task is ultimately important to the success for DEMO. Low-activation stainless steel (e.g. EUROFER, P92), which is already intended as structural material, could also become a possible plasma facing material, e.g. for the first wall (FW). Therefore, the ferritic martensitic steel P92 was investigated under DEMO relevant loading conditions. An area of the sample surfaces was firstly molten by transient events with varying power densities (A=245MW/m2, B=708MW/m2) and afterwards simultaneously and sequentially exposed to thermal and particle loads. Surface modifications and pronounced microstructure changes were investigated dependent on the pre-exposure, loading sequence and power density. More precisely, it turned out that there was no connection between the loading sequence and the surface modifications for the preloaded A-samples contrary to preloaded B-samples. The preloaded B-samples exhibited surface roughening, melting and the formation of holes dependent on the loading sequence and power density.

The investigation of plasma facing materials (PFM) subjected to a large number (≥10,000) of thermal shocks is of interest to determine long term morphological changes which might influence component lifetime in and plasma performance of a fusion reactor. The electron beam facility JUDITH 2 was used to simulate these conditions experimentally. In this study eight different tungsten grades produced by powder injection molding (PIM) were investigated: Two pure tungsten grades, one with 2 wt% Y2O3, three with 1, 2 and 3 wt% TiC, and two with 0.5 and 1 wt% TaC. Samples of 10 × 10 × 4 mm³ were brazed to a copper cooling structure and subjected to 105 thermal shocks of 0.5 ms duration and an intensity of Labs = 0.55 GW/m² (FHF = 12 MWs½/m2) at a base temperature of Tbase = 700 °C.The PIM grades showed damages in general comparable with a sintered and forged pure tungsten reference grade (>99.97 wt% W) that complies with the ITER specifications. One exception was the 2 wt% TiC doped material which failed early during the experiment by delamination of a large part of the surface. The Y2O3 doped material showed a comparatively good performance with respect to crack width (

An overview of the multi-messenger capabilities of the Pierre Auger Observatory is presented. The techniques and performance of searching for Ultra-High Energy neutrinos, photons and neutrons are described. Some of the most relevant results are reviewed, such as stringent upper bounds that were placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on neutrinos emitted from compact binary mergers that were detected by LIGO and Virgo during their first and second observing runs, as well as searches for high energy photons and neutrons from the Galactic center that constrain the properties of the putative Galactic PeVatron, observed by the H.E.S.S. collaboration. The observation of directional correlations between ultra-high energy cosmic rays and either high energy astrophysical neutrinos or specific source populations, weighted by their electromagnetic radiation, are also discussed. They constitute additional multi-messenger approaches aimed at identifying the sources of high energy cosmic rays.

Table of contents O1 Tumour heterogeneity: what does it mean? Dow-Mu Koh O2 Skeletal sequelae in adult survivors of childhood cancer Sue Creviston Kaste O3 Locoregional effects of breast cancer treatment Sarah J Vinnicombe O4 Imaging of cancer therapy-induced CNS toxicity Giovanni Morana, Andrea Rossi O5 Screening for lung cancer Christian J. Herold O6Risk stratification of lung nodules Theresa C. McLoud O7 PET imaging of pulmonary nodules Kirk A Frey O8 Transarterial tumour therapy Bernhard Gebauer O9 Interventional radiology in paediatric oncology Derek Roebuck O10 Image guided prostate interventions Jurgen J. Fütterer O11 Imaging cancer predisposition syndromes Alexander J. Towbin O12Chest and chest wall masses Thierry AG Huisman O13 Abdominal masses: good or bad? Anne MJB Smets O14 Hepatobiliary MR contrast: enhanced liver MRI for HCC diagnosis and management Giovanni Morana O15 Role of US elastography and multimodality fusion for managing patients with chronic liver disease and HCC Jeong Min Lee O16 Opportunities and challenges in imaging metastatic disease Hersh Chandarana O17 Diagnosis, treatment monitoring, and follow-up of lymphoma Marius E. Mayerhoefer, Markus Raderer, Alexander Haug O18 Managing high-risk and advanced prostate cancer Matthias Eiber O19 Immunotherapy: imaging challenges Bernhard Gebauer O20 RECIST and RECIST 1.1 Andrea Rockall O21 Challenges of RECIST in oncology imaging basics for the trainee and novice Aslam Sohaib O22 Lymphoma: PET for interim and end of treatment response assessment: a users’ guide to the Deauville Score Victoria S Warbey O23 Available resources Hebert Alberto Vargas O24 ICIS e-portal and the online learning community Dow-Mu Koh O25 Benign lesions that mimic pancreatic cancer Jay P Heiken O26 Staging and reporting pancreatic malignancies Isaac R Francis, Mahmoud, M Al-Hawary, Ravi K Kaza O27 Intraductal papillary mucinous neoplasm Giovanni Morana O28 Cystic pancreatic tumours Mirko D’Onofrio O29 Diffusion-weighted imaging of head and neck tumours Harriet C. Thoeny O30 Radiation injury in the head and neck Ann D King O31 PET/MR of paediatric brain tumours Giovanni Morana, Arnoldo Piccardo, Maria Luisa Garrè, Andrea Rossi O32 Structured reporting and beyond Hebert Alberto Vargas O33 Massachusetts General Hospital experience with structured reporting Theresa C. McLoud O34 The oncologist’s perspective: what the oncologist needs to know Nick Reed O35 Towards the cure of all children with cancer: global initiatives in pediatric oncology Carlos Rodriguez-Galindo O36 Multiparametric imaging of renal cancers Hersh Chandarana O37 Linking imaging features of renal disease and their impact on management strategies Hebert Alberto Vargas O38 Adrenals, retroperitoneum and peritoneum Isaac R Francis, Ashish P Wasnik O39 Lung and pleura Stefan Diederich O40 Advances in MRI Jurgen J. Fütterer O41 Advances in molecular imaging Wim J.G. Oyen O42 Incorporating advanced imaging, impact on treatment selection and patient outcome Cheng Lee Chaw, Nicholas van As S1 Combining ADC-histogram features improves performance of MR diffusion-weighted imaging for Lymph node characterisation in cervical cancer Igor Vieira, Frederik De Keyzer, Elleke Dresen, Sileny Han, Ignace Vergote, Philippe Moerman, Frederic Amant, Michel Koole, Vincent Vandecaveye S2 Whole-body diffusion-weighted MRI for surgical planning in patients with colorectal cancer and peritoneal metastases R Dresen, S De Vuysere, F De Keyzer, E Van Cutsem, A D’Hoore, A Wolthuis, V Vandecaveye S3 Role of apparent diffusion coefficient (ADC) diffusion-weighted MRI for predicting extra capsular extension of prostate cancer. P. Pricolo (paola.pricolo@ieo.it), S. Alessi, P. Summers, E. Tagliabue, G. Petralia S4 Generating evidence for clinical benefit of PET/CT – are management studies sufficient as surrogate for patient outcome? C. Pfannenberg, B. Gückel, SC Schüle, AC Müller, S. Kaufmann, N. Schwenzer, M. Reimold,C. la Fougere, K. Nikolaou, P. Martus S5 Heterogeneity of treatment response in skeletal metastases from breast cancer with 18F-fluoride and 18F-FDG PET GJ Cook, GK Azad, BP Taylor, M Siddique, J John, J Mansi, M Harries, V Goh S6 Accuracy of suspicious breast imaging—can we tell the patient? S Seth, R Burgul, A Seth S7 Measurement method of tumour volume changes during neoadjuvant chemotherapy affects ability to predict pathological response S Waugh, N Muhammad Gowdh, C Purdie, A Evans, E Crowe, A Thompson, S Vinnicombe S8 Diagnostic yield of CT IVU in haematuria screening F. Arfeen, T. Campion, E. Goldstraw S9 Percutaneous radiofrequency ablation of unresectable locally advanced pancreatic cancer: preliminary results D’Onofrio M, Ciaravino V, Crosara S, De Robertis R, Pozzi Mucelli R S10 Iodine maps from dual energy CT improve detection of metastases in staging examinations of melanoma patients M. Uhrig, D. Simons, H. Schlemmer S11Can contrast enhanced CT predict pelvic nodal status in malignant melanoma of the lower limb? Kate Downey S12 Current practice in the investigation for suspected Paraneoplastic Neurological Syndromes (PNS) and positive malignancy yield. S Murdoch, AS Al-adhami, S Viswanathan P1 Technical success and efficacy of Pulmonary Radiofrequency ablation: an analysis of 207 ablations S Smith, P Jennings, D Bowers, R Soomal P2 Lesion control and patient outcome: prospective analysis of radiofrequency abaltion in pulmonary colorectal cancer metastatic disease S Smith, P Jennings, D Bowers, R Soomal P3 Hepatocellular carcinoma in a post-TB patient: case of tropical infections and oncologic imaging challenges TM Mutala, AO Odhiambo, N Harish P4 Role of apparent diffusion coefficient (ADC) diffusion-weighted MRI for predicting extracapsular extension of prostate cancer P. Pricolo, S. Alessi, P. Summers, E. Tagliabue, G. Petralia P5 What a difference a decade makes; comparison of lung biopsies in Glasgow 2005 and 2015 M. Hall, M. Sproule, S. Sheridan P6 Solid pseudopapillary tumour of pancreas: imaging features of a rare neoplasm KY Thein, CH Tan, YL Thian, CM Ho P7 MDCT - pathological correlation in colon adenocarcinoma staging: preliminary experience S De Luca, C Carrera, V Blanchet, L Alarcón, E Eyheremnedy P8 Image guided biopsy of thoracic masses and reduction of pneumothorax risk: 25 years experience B K Choudhury, K Bujarbarua, G Barman P9 Tumour heterogeneity analysis of 18F-FDG-PET for characterisation of malignant peripheral nerve sheath tumours in neurofibromatosis-1 GJ Cook, E Lovat, M Siddique, V Goh, R Ferner, VS Warbey P10 Impact of introduction of vacuum assisted excision (VAE) on screen detected high risk breast lesions L Potti, B Kaye, A Beattie, K Dutton P11 Can we reduce prevalent recall rate in breast screening? AA Seth, F Constantinidis, H Dobson P12 How to reduce prevalent recall rate? Identifying mammographic lesions with low Positive Predictive Value (PPV) AA Seth (archana.seth@nhs.net), F Constantinidis, H Dobson P13 Behaviour of untreated pulmonary thrombus in oncology patients diagnosed with incidental pulmonary embolism on CT R. Bradley, G. Bozas, G. Avery, A. Stephens, A. Maraveyas P14 A one-stop lymphoma biopsy service – is it possible? S Bhuva, CA Johnson, M Subesinghe, N Taylor P15 Changes in the new TNM classification for lung cancer (8th edition, effective January 2017) LE Quint, RM Reddy, GP Kalemkerian P16 Cancer immunotherapy: a review of adequate imaging assessment G González Zapico, E Gainza Jauregui, R Álvarez Francisco, S Ibáñez Alonso, I Tavera Bahillo, L Múgica Álvarez P17 Succinate dehydrogenase mutations and their associated tumours O Francies, R Wheeler, L Childs, A Adams, A Sahdev P18 Initial experience in the usefulness of dual energy technique in the abdomen SE De Luca, ME Casalini Vañek, MD Pascuzzi, T Gillanders, PM Ramos, EP Eyheremendy P19 Recognising the serious complication of Richter’s transformation in CLL patients C Stove, M Digby P20 Body diffusion-weighted MRI in oncologic practice: truths, tricks and tips M. Nazar, M. Wirtz, MD. Pascuzzi, F. Troncoso, F. Saguier, EP. Eyheremendy P21 Methotrexate-induced leukoencephalopathy in paediatric ALL Patients D.J. Quint, L. Dang, M. Carlson, S. Leber, F. Silverstein P22 Pitfalls in oncology CT reporting. A pictorial review R Rueben, S Viswanathan P23 Imaging of perineural extension in head and neck tumours B Nazir, TH Teo, JB Khoo P24 MRI findings of molecular subtypes of breast cancer: a pictorial primer K Sharma, N Gupta, B Mathew, T Jeyakumar, K Harkins P25 When cancer can’t wait! A pictorial review of oncological emergencies K Sharma, B Mathew, N Gupta, T Jeyakumar, S Joshua P26 MRI of pancreatic neuroendocrine tumours: an approach to interpretation D Christodoulou, S Gourtsoyianni, A Jacques, N Griffin, V Goh P27 Gynaecological cancers in pregnancy: a review of imaging CA Johnson, J Lee P28 Suspected paraneoplastic neurological syndromes - review of published recommendations to date, with proposed guideline/flowchart JA Goodfellow, AS Al-adhami, S Viswanathan P29 Multi-parametric MRI of the pelvis for suspected local recurrence of prostate cancer after radical prostatectomy R Bradley P30 Utilisation of PI-RADS version 2 in multi-parametric MRI of the prostate; 12-months experience R Bradley P31 Radiological assessment of the post-chemotherapy liver A Yong, S Jenkins, G Joseph P32 Skeletal staging with MRI in breast cancer – what the radiologist needs to know S Bhuva, K Partington P33 Perineural spread of lympoma: an educational review of an unusual distribution of disease CA Johnson, S Bhuva, M Subesinghe, N Taylor P34 Visually isoattenuating pancreatic adenocarcinoma. Diagnostic imaging tools. C Carrera, A Zanfardini, S De Luca, L Alarcón, V Blanchet, EP Eyheremendy P35 Imaging of larynx cancer: when is CT, MRI or FDG PET/CT the best test? K Cavanagh, E Lau