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  • 1.
    Blanken, T. C.
    et al.
    Eindhoven Univ Technol, Control Syst Technol Grp, Dept Mech Engn, POB 513, NL-5600 MB Eindhoven, Netherlands.;Eindhoven Univ Technol, POB 513, NL-5600 MB Eindhoven, Netherlands..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, T.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Dori, V
    Univ Split, Fac Elect Engn Mech Engn & Naval Architecture, R Boskovica 32, Split 21000, Croatia..
    Real-time plasma state monitoring and supervisory control on TCV2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 2, article id 026017Article in journal (Refereed)
    Abstract [en]

    In ITER and DEMO, various control objectives related to plasma control must be simultaneously achieved by the plasma control system (PCS), in both normal operation as well as off-normal conditions. The PCS must act on off-normal events and deviations from the target scenario, since certain sequences (chains) of events can precede disruptions. It is important that these decisions are made while maintaining a coherent prioritization between the real-time control tasks to ensure high-performance operation. In this paper, a generic architecture for task-based integrated plasma control is proposed. The architecture is characterized by the separation of state estimation, event detection, decisions and task execution among different algorithms, with standardized signal interfaces. Central to the architecture are a plasma state monitor and supervisory controller. In the plasma state monitor, discrete events in the continuous-valued plasma state arc modeled using finite state machines. This provides a high-level representation of the plasma state. The supervisory controller coordinates the execution of multiple plasma control tasks by assigning task priorities, based on the finite states of the plasma and the pulse schedule. These algorithms were implemented on the TCV digital control system and integrated with actuator resource management and existing state estimation algorithms and controllers. The plasma state monitor on TCV can track a multitude of plasma events, related to plasma current, rotating and locked neoclassical tearing modes, and position displacements. In TCV experiments on simultaneous control of plasma pressure, safety factor profile and NTMs using electron cyclotron heating (ECI I) and current drive (ECCD), the supervisory controller assigns priorities to the relevant control tasks. The tasks are then executed by feedback controllers and actuator allocation management. This work forms a significant step forward in the ongoing integration of control capabilities in experiments on TCV, in support of tokamak reactor operation.

  • 2. Brezinsek, S.
    et al.
    Widdowson, A.
    Mayer, M.
    Philipps, V.
    Baron-Wiechec, P.
    Coenen, J. W.
    Heinola, K.
    Huber, A.
    Likonen, J.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stamp, M. F.
    Borodin, D.
    Coad, J. P.
    Carrasco, Alvaro Garcia
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Kirschner, A.
    Krat, S.
    Krieger, K.
    Lipschultz, B.
    Linsmeier, Ch.
    Matthews, G. F.
    Schmid, K.
    Beryllium migration in JET ITER-like wall plasmas2015In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, no 6, article id 063021Article in journal (Refereed)
    Abstract [en]

    JET is used as a test bed for ITER, to investigate beryllium migration which connects the lifetime of first-wall components under erosion with tokamak safety, in relation to long-term fuel retention. The (i) limiter and the (ii) divertor configurations have been studied in JET-ILW (JET with a Be first wall and W divertor), and compared with those for the former JET-C (JET with carbon-based plasma-facing components (PFCs)). (i) For the limiter configuration, the Be gross erosion at the contact point was determined in situ by spectroscopy as between 4% (E-in = 35 eV) and more than 100%, caused by Be self-sputtering (E-in = 200 eV). Chemically assisted physical sputtering via BeD release has been identified to contribute to the effective Be sputtering yield, i.e. at E-in = 75 eV, erosion was enhanced by about 1/3 with respect to the bare physical sputtering case. An effective gross yield of 10% is on average representative for limiter plasma conditions, whereas a factor of 2 difference between the gross erosion and net erosion, determined by post-mortem analysis, was found. The primary impurity source in the limiter configuration in JET-ILW is only 25% higher (in weight) than that for the JET-C case. The main fraction of eroded Be stays within the main chamber. (ii) For the divertor configuration, neutral Be and BeD from physically and chemically assisted physical sputtering by charge exchange neutrals and residual ion flux at the recessed wall enter the plasma, ionize and are transported by scrape-off layer flows towards the inner divertor where significant net deposition takes place. The amount of Be eroded at the first wall (21 g) and the Be amount deposited in the inner divertor (28 g) are in fair agreement, though the balancing is as yet incomplete due to the limited analysis of PFCs. The primary impurity source in the JET-ILW is a factor of 5.3 less in comparison with that for JET-C, resulting in lower divertor material deposition, by more than one order of magnitude. Within the divertor, Be performs far fewer re-erosion and transport steps than C due to an energetic threshold for Be sputtering, and inhibits as a result of this the transport to the divertor floor and the pump duct entrance. The target plates in the JET-ILW inner divertor represent at the strike line a permanent net erosion zone, in contrast to the net deposition zone in JET-C with thick carbon deposits on the CFC (carbon-fibre composite) plates. The Be migration identified is consistent with the observed low long-term fuel retention and dust production with the JET-ILW.

  • 3. Fortuna-Zalesna, E.
    et al.
    Grzonka, J.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Baron-Wiechec, A.
    Ciupinski, L.
    Studies of dust from JET with the ITER-Like Wall: Composition and internal structure2017In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 582-587Article in journal (Refereed)
    Abstract [en]

    Results are presented for the dust survey performed at JET after the second experimental campaign with the ITER-Like Wall: 2013-2014. Samples were collected on adhesive stickers from several different positions in the divertor both on the tiles and on the divertor carrier. Brittle dust-forming deposits on test mirrors from the inner divertor wall were also studied. Comprehensive characterization accomplished by a wide range of high-resolution microscopy techniques, including focused ion beam, has led to the identification of several classes of particles: (i) beryllium flakes originating either from the Be coatings from the inner wall cladding or Be-rich mixed co-deposits resulting from material migration; (ii) beryllium droplets and splashes; (iii) tungsten and nickel-rich (from Inconel) droplets; (iv) mixed material layers with a various content of small (8-200 nm) W-Mo and Ni-based debris. A significant content of nitrogen from plasma edge cooling has been identified in all types of co-deposits. A comparison between particles collected after the first and second experimental campaign is also presented and discussed.

  • 4.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Impact of material migration on plasma-facing components in tokamaks2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Plasma-wall interaction plays an essential role in the performance and safety of a fusion reactor. This thesis focuses on the impact of material migration on plasma-facing components. It is based on experiments performed in tokamaks: JET, TEXTOR and ASDEX Upgrade. The objectives of the experiments were to assess fuel and impurity removal under ion cyclotron wall conditioning (ICWC) and plasma impact on diagnostic mirrors.

    In wall conditioning studies, tracer techniques based on the injection of rare isotopes (15N, 18O) were used to determine conclusively the impact of the respective gases. For the first time, probe surfaces and wall components exposed to ICWC were examined by surface analysis methods. Discharges in hydrogen were the most efficient to erode carbon co-deposits, resulting in a reduction of the initial deuterium content by a factor of two. It was also found that impurities desorbed under ICWC are partly re-deposited on the wall.

    Plasma impact on diagnostic mirrors was determined by surface analysis of test mirrors exposed at JET. Reflectivity of mirrors from the divertor region was severely decreased due to deposits of beryllium, deuterium, carbon and other impurities. This result points out the need to develop mirror maintenance procedures. Neutron damage on mirrors was simulated by ion irradiation in an ion implanter. It was shown that damage levels similar to those expected in the first wall of a fusion reactor do not produce a significant change in reflectivity.

  • 5.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Investigation of probe surfaces after ion cyclotron wall conditioning in ASDEX UpgradeManuscript (preprint) (Other academic)
    Abstract [en]

    For the first time, material analysis techniques have been applied to study the effect of ion cyclotron wall conditioning (ICWC) on probe surfaces in a metal-wall machine. ICWC is a technique envisaged to contribute to the removal of fuel and impurities from the first wall of ITER. The objective of this work was to assess impurity migration under the ICWC operation. Tungsten probes were exposed in ASDEX Upgrade to discharges in helium. After wall conditioning, the probes were covered with a co-deposited layer containing D, B, C, N, O and relatively high amount of He on virgin W substrates. The concentration ratio He/C+B was 0.7. The formation of the co-deposited layer indicates that a fraction of the impurities desorbed from the wall under ICWC operation are transported by plasma and deposited away from their original location.

  • 6.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Plasma impact on diagnostic mirrors in JETManuscript (preprint) (Other academic)
    Abstract [en]

    All optical diagnostics in ITER will rely on metallic mirrors acting as plasma-facing components. This contribution provides a comprehensive account on plasma impact on diagnostic mirrors in JET with the ITER-Like Wall. Specimens from the First Mirror Test and the lithium-beam diagnostic have been studied by spectrophotometry, ion beam analysis and electron microscopy. Test mirrors made of molybdenum were retrieved from the main chamber and the divertor after exposure to the 2013-2014 experimental campaign. In the main chamber, only mirrors located at the entrance of the carrier lost reflectivity (Be deposition from the eroded limiters), while those located deeper in the carrier were only slightly affected. The performance of mirrors in the JET divertor was strongly degraded by deposition of beryllium, tungsten and other species. Mirrors from the lithium-beam diagnostic have been studied for the first time. Gold coatings were severely damaged by intense arcing. As a consequence, material mixing of the gold layer with the stainless steel substrate occurred. Total reflectivity dropped from over 90% to less than 60 %, i.e. to the level typical for stainless steel.

  • 7.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Möller, S.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kreter, A.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Wauters, T.
    Impact of ion cyclotron wall conditioning on fuel removal from plasma-facing components at TEXTOR2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, p. 014017-Article in journal (Refereed)
    Abstract [en]

    Ion cyclotron wall conditioning (ICWC) is based on low temperature and low density plasmas produced and sustained by ion cyclotron resonance (ICR) pulses in reactive or noble gases. The technique is being developed for ITER. It is tested in tokamaks in the presence of toroidal magnetic field (0.2-3.8 T) and heating power of the order of 10(5) W. ICWC with hydrogen, deuterium and oxygen-helium mixture was studied in the TEXTOR tokamak. The exposed samples were pre-characterized limiter tiles mounted on specially designed probes. The objectives were to assess the reduction of deuterium content, the uniformity of the reduction and the retention of seeded oxygen. For the last objective oxygen-18 was used as a marker. ICWC in hydrogen caused a drop of deuterium content in the tile by a factor of more than 2: from 4.5x10(18) to 1.9x10(18) D cm(-2). A decrease of the fuel content by approximately 25% was achieved by the ICWC in oxygen, while no reduction of the fuel content was measured after exposure to discharges in deuterium. These are the first data ever obtained showing quantitatively the local decrease of deuterium in wall components treated by ICWC in a tokamak. The oxygen retention in the tiles exposed to ICWC with oxygen-helium was analyzed for different orientations and radial positions with respect to plasma. An average retention of 1.38x10(16) O-18 cm(-2) was measured. A maximum of the retention, 4.4x10(16) O-18 cm(-2), was identified on a sample surface near the plasma edge. The correlation with the gas inlet and antennae location has been studied.

  • 8.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Widdowson, A.
    Fortuna-Zalesna, E.
    Jachmich, S.
    Brix, M.
    Marot, L.
    Plasma impact on diagnostic mirrors in JET2017In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 506-512Article in journal (Refereed)
    Abstract [en]

    Metallic mirrors will be essential components of all optical systems for plasma diagnosis in ITER. This contribution provides a comprehensive account on plasma impact on diagnostic mirrors in JET with the ITER-Like Wall. Specimens from the First Mirror Test and the lithium-beam diagnostic have been studied by spectrophotometry, ion beam analysis and electron microscopy. Test mirrors made of molybdenum were retrieved from the main chamber and the divertor after exposure to the 2013-2014 experimental campaign. In the main chamber, only mirrors located at the entrance of the carrier lost reflectivity (Be deposition), while those located deeper in the carrier were only slightly affected. The performance of mirrors in the JET divertor was strongly degraded by deposition of beryllium, tungsten and other species. Mirrors from the lithium-beam diagnostic have been studied for the first time. Gold coatings were severely damaged by intense arcing. As a consequence, material mixing of the gold layer with the stainless steel substrate occurred. Total reflectivity dropped from over 90% to less than 60%, i.e. to the level typical for stainless steel.

  • 9.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Schwarz-Selinger, T.
    Wauters, T.
    Douai, D.
    Bobkov, V.
    Cavazzana, R.
    Krieger, K.
    Lyssoivan, A.
    Moeller, S.
    Spolaore, M.
    Rohde, V.
    Rubel, M.
    Investigation of probe surfaces after ion cyclotron wall conditioning in ASDEX upgrade2017In: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, p. 733-735Article in journal (Refereed)
    Abstract [en]

    For the first time, material analysis techniques have been applied to study the effect of ion cyclotron wall conditioning (ICWC) on probe surfaces in a metal-wall machine. ICWC is a technique envisaged to contribute to the removal of fuel and impurities from the first wall of ITER. The objective of this work was to assess impurity migration under ICWC operation. Tungsten probes were exposed in ASDEX Upgrade to discharges in helium. After wall conditioning, the probes were covered with a co-deposited layer containing D, B, C, N, O and relatively high amount of He. The concentration ratio He/C+B was 0.7. The formation of the co-deposited layer indicates that a fraction of the impurities desorbed from the wall under ICWC operation are transported by plasma and deposited away from their original location.

  • 10.
    Garcia Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Wauters, T.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Drenik, A.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Crombé, K.
    Douai, D.
    Fortuna, E.
    Kogut, D.
    Kreter, A.
    Lyssoivan, A.
    Möller, S.
    Pisarek, M.
    Vervier, M.
    Nitrogen removal from plasma-facing components by ion cyclotron wall conditioning in TEXTOR2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 688-692Article in journal (Other academic)
    Abstract [en]

    The efficiency of ion cyclotron wall conditioning (ICWC) in the removal of nitrogen from plasma-facing components in TEXTOR was assessed. In two experiments the wall was loaded with nitrogen and subsequently cleaned by ICWC in deuterium and helium. The retention and removal of nitrogen was studied in-situ by means of mass spectrometry, and ex-situ by surface analysis of a set of graphite, tungsten and TZM plates installed on test limiter systems. N-15 rare isotope was used as a marker. The results from the gas balance showed that about 25% of the retained nitrogen was removed after ICWC cleaning, whereas surface analysis of the plates based on ToF-HIERDA showed an increase of the deposited species after the cleaning. This indicates that during ICWC operation on carbon devices, nitrogen is not only pumped out but also transported to other locations on the wall. Additionally, deuterium surface content was studied before and after ICWC cleaning.

  • 11.
    Garcia-Carrasco, Alvaro
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Grzonka, J.
    Gilbert, M. R.
    Fortuna-Zalesna, E.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Impact of helium implantation and ion-induced damage on reflectivity of molybdenum mirrors2016In: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584Article in journal (Refereed)
    Abstract [en]

    Molybdenum mirrors were irradiated with Mo and He ions to simulate the effect of neutron irradiation on diagnostic first mirrors in next-generation fusion devices. Up to 30 dpa were produced under molybdenum irradiation leading to a slight decrease of reflectivity in the near infrared range. After 3×1017 cm-2 of helium irradiation, reflectivity decreased by up to 20%. Combined irradiation by helium and molybdenum led to similar effects on reflectivity as irradiation with helium alone. Ion beam analysis showed that only 7% of the implanted helium was retained in the first 40nm layer of the mirror. The structure of the near-surface layer after irradiation was studied with scanning transmission electron microscopy and the extent and size distribution of helium bubbles was documented. The consequences of ion-induced damage on the performance of diagnostic components are discussed.

  • 12.
    García Carrasco, Álvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Plasma-Facing Components in Tokamaks: Studies of Wall Conditioning Processes and Plasma Impact on Diagnostic Mirrors2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Understanding of material migration and its impact on the formation of co-deposited mixed material layers on plasma-facing components is essential for the development of fusion reactors. This thesis focuses on this topic. It is based on experiments performed at JET and TEXTOR tokamaks. The major objectives were to determine: (i) fuel and impurity removal from plasma-facing components by ICWC in different gas mixtures, (ii) fuel and impurity transport connected to ICWC operation, (iii) plasma impact on diagnostic mirrors. All these issues are in line with the ITER needs: mitigation of co-deposition and fuel inventory, and the performance of first mirrors in long-term operation. The novelty in research is demonstrated by several elements. In wall conditioning studies, tracer techniques based on injection of rare isotopes (N-15, O-18) were used to determine conclusively the impact of respective gases. Also, a new approach to ICWC was developed by combining global gas balance studies based on mass spectrometry and the use of multiple surface probes exposed to discharges and then studied ex-situ with accelerator-based techniques. Impact of plasma on diagnostic mirrors was determined after exposure to the entire first experimental campaign in JET-ILW.

  • 13. Hakola, A.
    et al.
    Brezinsek, S.
    Douai, D.
    Balden, M.
    Bobkov, V.
    Carralero, D.
    Greuner, H.
    Elgeti, S.
    Kallenbach, A.
    Krieger, K.
    Meisl, G.
    Oberkofler, M.
    Rohde, V.
    Schneider, P.
    Schwarz-Selinger, T.
    Lahtinen, A.
    De Temmerman, G.
    Caniello, R.
    Ghezzi, F.
    Wauters, T.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Radovic, I. Bogdanovic
    Siketic, Z.
    Plasma-wall interaction studies in the full-W ASDEX upgrade during helium plasma discharges2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 6, article id 066015Article in journal (Refereed)
    Abstract [en]

    Plasma-wall interactions have been studied in the full-W ASDEX Upgrade during its dedicated helium campaign. Relatively clean plasmas with a He content of > 80% could be obtained by applying ion cyclotron wall conditioning (ICWC) discharges upon changeover from D to He. However, co-deposited layers with significant amounts of He and D were measured on W samples exposed to ICWC plasmas at the low-field side (outer) midplane. This is a sign of local migration and accumulation of materials and residual fuel in regions shadowed from direct plasma exposure albeit globally D was removed from the vessel. When exposing W samples to ELMy H-mode helium plasmas in the outer strike-point region, no net erosion was observed but the surfaces had been covered with co-deposited layers mainly consisting of W, B, C, and D and being the thickest on rough and modified surfaces. This is different from the typical erosion-deposition patterns in D plasmas, where usually sharp net-erosion peaks surrounded by prominent net-deposition maxima for W are observed close to the strike point. Moreover, no clear signs of W nanostructure growth or destruction could be seen. The growth of deposited layers may impact the operation of future fusion reactors and is attributed to strong sources in the main chamber that under suitable conditions may switch the balance from net erosion into net deposition, even close to the strike points. In addition, the absence of noticeable chemical erosion in helium plasmas may have affected the thickness of the deposited layers. Retention of He, for its part, remained small and uniform throughout the strike-point region although our results indicate that samples with smooth surfaces can contain an order of magnitude less He than their rough counterparts.

  • 14.
    Ivanova, Darya
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Widdowson, A.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Likonen, J.
    Marot, L.
    Alves, E.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Pintsuk, G.
    An overview of the comprehensive First Mirror Test in JET with ITER-like wall2014In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T159, p. 014011-Article in journal (Refereed)
    Abstract [en]

    The First Mirror Test in Joint European Torus (JET) with the International Thermonuclear Experimental Reactor-like wall was performed with polycrystalline molybdenum mirrors. Two major types of experiments were done. Using a reciprocating probe system in the main chamber, a short-term exposure was made during a 0.3 h plasma operation in 71 discharges. The impact on reflectivity was negligible. In a long-term experiment lasting 19 h with 13 h of X-point plasma, 20 Mo mirrors were exposed, including four coated with a 1 mu m-thick Rh layer. Optical performance of all mirrors exposed in the divertor was degraded by up to 80% because of beryllium, carbon and tungsten co-deposits on surfaces. Total reflectivity of most Mo mirrors facing plasma in the main chamber was only slightly affected in the spectral range 400-1600 nm, while the Rh-coated mirror lost its high original reflectivity by 30%, thus decreasing to the level typical of molybdenum surfaces. Specular reflectivity was decreased most strongly in the 250-400 nm UV range. Surface measurements with x-ray photoelectron spectroscopy and depth profiling with secondary ion mass spectrometry and heavy-ion elastic recoil detection analysis (ERDA) revealed that the very surface region on both types of mirrors had been modified by neutrals, resulting eventually in the composition change: Be, C, D at the level below 1x10(16) cm(-2) mixed with traces of Ni, Fe in the layer 10-30 nm thick. On several exposed mirrors, the original matrix material (Mo) remained as the major constituent of the modified layer. The data obtained in two major phases of the JET operation with carbon and full metal walls are compared. The implications of these results for first mirrors and their maintenance in a reactor-class device are discussed.

  • 15. Lituadon, Xavier
    et al.
    Bergsåker, Henric
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefániková, Estera
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Vallejos Olivares, Pablo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushan
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    et al.,
    Overview of the JET results in support to ITER2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102001Article in journal (Refereed)
    Abstract [en]

    The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H  =  1 at β N ~ 1.8 and n/n GW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed.

  • 16. Meyer, H.
    et al.
    Eich, T.
    Beurskens, M.
    Coda, S.
    Hakola, A.
    Martin, P.
    Adamek, J.
    Agostini, M.
    Aguiam, D.
    Ahn, J.
    Aho-Mantila, L.
    Akers, R.
    Albanese, R.
    Aledda, R.
    Alessi, E.
    Allan, S.
    Alves, D.
    Ambrosino, R.
    Amicucci, L.
    Anand, H.
    Anastassiou, G.
    Andrebe, Y.
    Angioni, C.
    Apruzzese, G.
    Ariola, M.
    Arnichand, H.
    Arter, W.
    Baciero, A.
    Barnes, M.
    Barrera, L.
    Behn, R.
    Bencze, A.
    Bernardo, J.
    Bernert, M.
    Bettini, P.
    Bilkova, P.
    Bin, W.
    Birkenmeier, G.
    Bizarro, J. P. S.
    Blanchard, P.
    Blanken, T.
    Bluteau, M.
    Bobkov, V.
    Bogar, O.
    Boehm, P.
    Bolzonella, T.
    Boncagni, L.
    Botrugno, A.
    Bottereau, C.
    Bouquey, F.
    Bourdelle, C.
    Bremond, S.
    Brezinsek, S.
    Brida, D.
    Brochard, F.
    Buchanan, J.
    Bufferand, H.
    Buratti, P.
    Cahyna, P.
    Calabro, G.
    Camenen, Y.
    Caniello, R.
    Cannas, B.
    Canton, A.
    Cardinali, A.
    Carnevale, D.
    Carr, M.
    Carralero, D.
    Carvalho, P.
    Casali, L.
    Castaldo, C.
    Castejon, F.
    Castro, R.
    Causa, F.
    Cavazzana, R.
    Cavedon, M.
    Cecconello, M.
    Ceccuzzi, S.
    Cesario, R.
    Challis, C. D.
    Chapman, I. T.
    Chapman, S.
    Chernyshova, M.
    Choi, D.
    Cianfarani, C.
    Ciraolo, G.
    Citrin, J.
    Clairet, F.
    Classen, I.
    Coelho, R.
    Coenen, J. W.
    Colas, L.
    Conway, G.
    Corre, Y.
    Costea, S.
    Crisanti, F.
    Cruz, N.
    Cseh, G.
    Czarnecka, A.
    D'Arcangelo, O.
    De Angeli, M.
    De Masi, G.
    De Temmerman, G.
    De Tommasi, G.
    Decker, J.
    Delogu, R. S.
    Dendy, R.
    Denner, P.
    Di Troia, C.
    Dimitrova, M.
    D'Inca, R.
    Doric, V.
    Douai, D.
    Drenik, A.
    Dudson, B.
    Dunai, D.
    Dunne, M.
    Duval, B. P.
    Easy, L.
    Elmore, S.
    Erdos, B.
    Esposito, B.
    Fable, E.
    Faitsch, M.
    Fanni, A.
    Fedorczak, N.
    Felici, F.
    Ferreira, J.
    Fevrier, O.
    Ficker, O.
    Fietz, S.
    Figini, L.
    Figueiredo, A.
    Fil, A.
    Fishpool, G.
    Fitzgerald, M.
    Fontana, M.
    Ford, O.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Fridstr, R.
    Frigione, D.
    Fuchert, G.
    Fuchs, C.
    Palumbo, M. Furno
    Futatani, S.
    Gabellieri, L.
    Galazka, K.
    Galdon-Quiroga, J.
    Galeani, S.
    Gallart, D.
    Gallo, A.
    Galperti, C.
    Gao, Y.
    Garavaglia, S.
    Garcia, J.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia-Lopez, J.
    Garcia-Munoz, M.
    Gardarein, J. -L
    Garzotti, L.
    Gaspar, J.
    Gauthier, E.
    Geelen, P.
    Geiger, B.
    Ghendrih, P.
    Ghezzi, F.
    Giacomelli, L.
    Giannone, L.
    Giovannozzi, E.
    Giroud, C.
    Gleason Gonzalez, C.
    Gobbin, M.
    Goodman, T. P.
    Gorini, G.
    Gospodarczyk, M.
    Granucci, G.
    Gruber, M.
    Gude, A.
    Guimarais, L.
    Guirlet, R.
    Gunn, J.
    Hacek, P.
    Hacquin, S.
    Hall, S.
    Ham, C.
    Happel, T.
    Harrison, J.
    Harting, D.
    Hauer, V.
    Havlickova, E.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Helou, W.
    Henderson, S.
    Hennequin, P.
    Heyn, M.
    Hnat, B.
    Holzl, M.
    Hogeweij, D.
    Honore, C.
    Hopf, C.
    Horacek, J.
    Hornung, G.
    Horvath, L.
    Huang, Z.
    Huber, A.
    Igitkhanov, J.
    Igochine, V.
    Imrisek, M.
    Innocente, P.
    Ionita-Schrittwieser, C.
    Isliker, H.
    Ivanova-Stanik, I.
    Jacobsen, A. S.
    Jacquet, P.
    Jakubowski, M.
    Jardin, A.
    Jaulmes, F.
    Jenko, F.
    Jensen, T.
    Busk, O. Jeppe Miki
    Jessen, M.
    Joffrin, E.
    Jones, O.
    Jonsson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Kallenbach, A.
    Kallinikos, N.
    Kalvin, S.
    Kappatou, A.
    Karhunen, J.
    Karpushov, A.
    Kasilov, S.
    Kasprowicz, G.
    Kendl, A.
    Kernbichler, W.
    Kim, D.
    Kirk, A.
    Kjer, S.
    Klimek, I.
    Kocsis, G.
    Kogut, D.
    Komm, M.
    Korsholm, S. B.
    Koslowski, H. R.
    Koubiti, M.
    Kovacic, J.
    Kovarik, K.
    Krawczyk, N.
    Krbec, J.
    Krieger, K.
    Krivska, A.
    Kube, R.
    Kudlacek, O.
    Kurki-Suonio, T.
    Labit, B.
    Laggner, F. M.
    Laguardia, L.
    Lahtinen, A.
    Lalousis, P.
    Lang, P.
    Lauber, P.
    Lazanyi, N.
    Lazaros, A.
    Le, H. B.
    Lebschy, A.
    Leddy, J.
    Lefevre, L.
    Lehnen, M.
    Leipold, F.
    Lessig, A.
    Leyland, M.
    Li, L.
    Liang, Y.
    Lipschultz, B.
    Liu, Y. Q.
    Loarer, T.
    Loarte, A.
    Loewenhoff, T.
    Lomanowski, B.
    Loschiavo, V. P.
    Lunt, T.
    Lupelli, I.
    Lux, H.
    Lyssoivan, A.
    Madsen, J.
    Maget, P.
    Maggi, C.
    Maggiora, R.
    Magnussen, M. L.
    Mailloux, J.
    Maljaars, B.
    Malygin, A.
    Mantica, P.
    Mantsinen, M.
    Maraschek, M.
    Marchand, B.
    Marconato, N.
    Marini, C.
    Marinucci, M.
    Markovic, T.
    Marocco, D.
    Marrelli, L.
    Martin, Y.
    Solis, J. R. Martin
    Martitsch, A.
    Mastrostefano, S.
    Mattei, M.
    Matthews, G.
    Mavridis, M.
    Mayoral, M. -L
    Mazon, D.
    McCarthy, P.
    McAdams, R.
    McArdle, G.
    McClements, K.
    McDermott, R.
    McMillan, B.
    Meisl, G.
    Merle, A.
    Meyer, O.
    Milanesio, D.
    Militello, F.
    Miron, I. G.
    Mitosinkova, K.
    Mlynar, J.
    Mlynek, A.
    Molina, D.
    Molina, P.
    Monakhov, I.
    Morales, J.
    Moreau, D.
    Morel, P.
    Moret, J. -M
    Moro, A.
    Moulton, D.
    Mueller, H. W.
    Nabais, F.
    Nardon, E.
    Naulin, V.
    Nemes-Czopf, A.
    Nespoli, F.
    Neu, R.
    Nielsen, A. H.
    Nielsen, S. K.
    Nikolaeva, V.
    Nimb, S.
    Nocente, M.
    Nouailletas, R.
    Nowak, S.
    Oberkofler, M.
    Oberparleiter, M.
    Ochoukov, R.
    Odstrcil, T.
    Olsen, J.
    Omotani, J.
    O'Mullane, M. G.
    Orain, F.
    Osterman, N.
    Paccagnella, R.
    Pamela, S.
    Pangione, L.
    Panjan, M.
    Papp, G.
    Paprok, R.
    Parail, V.
    Parra, I.
    Pau, A.
    Pautasso, G.
    Pehkonen, S. -P
    Pereira, A.
    Cippo, E. Perelli
    Ridolfini, V. Pericoli
    Peterka, M.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petrzilka, V.
    Piovesan, P.
    Piron, C.
    Pironti, A.
    Pisano, F.
    Pisokas, T.
    Pitts, R.
    Ploumistakis, I.
    Plyusnin, V.
    Pokol, G.
    Poljak, D.
    Poloskei, P.
    Popovic, Z.
    Por, G.
    Porte, L.
    Potzel, S.
    Predebon, I.
    Preynas, M.
    Primc, G.
    Pucella, G.
    Puiatti, M. E.
    Putterich, T.
    Rack, M.
    Ramogida, G.
    Rapson, C.
    Rasmussen, J. Juul
    Rasmussen, J.
    Ratta, G. A.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ravera, G.
    Refy, D.
    Reich, M.
    Reimerdes, H.
    Reimold, F.
    Reinke, M.
    Reiser, D.
    Resnik, M.
    Reux, C.
    Ripamonti, D.
    Rittich, D.
    Riva, G.
    Rodriguez-Ramos, M.
    Rohde, V.
    Rosato, J.
    Ryter, F.
    Saarelma, S.
    Sabot, R.
    Saint-Laurent, F.
    Salewski, M.
    Salmi, A.
    Samaddar, D.
    Sanchis-Sanchez, L.
    Santos, J.
    Sauter, O.
    Scannell, R.
    Scheffer, M.
    Schneider, M.
    Schneider, B.
    Schneider, P.
    Schneller, M.
    Schrittwieser, R.
    Schubert, M.
    Schweinzer, J.
    Seidl, J.
    Sertoli, M.
    Sesnic, S.
    Shabbir, A.
    Shalpegin, A.
    Shanahan, B.
    Sharapov, S.
    Sheikh, U.
    Sias, G.
    Sieglin, B.
    Silva, C.
    Silva, A.
    Fuglister, M. Silva
    Simpson, J.
    Snicker, A.
    Sommariva, C.
    Sozzi, C.
    Spagnolo, S.
    Spizzo, G.
    Spolaore, M.
    Stange, T.
    Pedersen, M. Stejner
    Stepanov, I.
    Stober, J.
    Strand, P.
    Susnjara, A.
    Suttrop, W.
    Szepesi, T.
    Tal, B.
    Tala, T.
    Tamain, P.
    Tardini, G.
    Tardocchi, M.
    Teplukhina, A.
    Terranova, D.
    Testa, D.
    Theiler, C.
    Thornton, A.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Tophoj, L.
    Treutterer, W.
    Trevisan, G. L.
    Tripsky, M.
    Tsironis, C.
    Tsui, C.
    Tudisco, O.
    Uccello, A.
    Urban, J.
    Valisa, M.
    Vallejos, Pablo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Valovic, M.
    Van den Brand, H.
    Vanovac, B.
    Varoutis, S.
    Vartanian, S.
    Vega, J.
    Verdoolaege, G.
    Verhaegh, K.
    Vermare, L.
    Vianello, N.
    Vicente, J.
    Viezzer, E.
    Vignitchouk, L.
    Vijvers, W. A. J.
    Villone, F.
    Viola, B.
    Vlahos, L.
    Voitsekhovitch, I.
    Vondracek, P.
    Vu, N. M. T.
    Wagner, D.
    Walkden, N.
    Wang, N.
    Wauters, T.
    Weiland, M.
    Weinzettl, V.
    Westerhof, E.
    Wiesenberger, M.
    Willensdorfer, M.
    Wischmeier, M.
    Wodniak, I.
    Wolfrum, E.
    Yadykin, D.
    Zagorski, R.
    Zammuto, I.
    Zanca, P.
    Zaplotnik, R.
    Zestanakis, P.
    Zhang, W.
    Zoletnik, S.
    Zuin, M.
    Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution2017In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 10, article id 102014Article in journal (Refereed)
    Abstract [en]

    Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads to tolerable heat and particle loads on the wall is a major challenge. The new European medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade (AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal and SOL parameters are not achievable simultaneously in present day devices. A two prong approach is adopted. On the one hand, scenarios with tolerable transient heat and particle loads, including active edge localised mode (ELM) control are developed. On the other hand, divertor solutions including advanced magnetic configurations are studied. Considerable progress has been made on both approaches, in particular in the fields of: ELM control with resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control, as well as filamentary scrape-off-layer transport. For example full ELM suppression has now been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement H-H(98,H-y2) approximate to 0.95. Advances have been made with respect to detachment onset and control. Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor) shed new light on SOL physics. Cross field filamentary transport has been characterised in a wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the SOL also play a crucial role for ELM stability and access to small ELM regimes.

  • 17.
    Rubel, Marek
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Moon, Soonwoo
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hallén, Anders
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Krawczynska, A.
    Fortuna-Zalesna, E.
    Gilbert, M.
    Plocinski, T.
    Widdowson, A.
    Metallic mirrors for plasma diagnosis in current and future reactors: tests for ITER and DEMO2017In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, article id 014061Article in journal (Refereed)
    Abstract [en]

    Optical spectroscopy and imaging diagnostics in next-step fusion devices will rely on metallic mirrors. The performance of mirrors is studied in present-day tokamaks and in laboratory systems. This work deals with comprehensive tests of mirrors: (a) exposed in JET with the ITER-like wall (JET-ILW); (b) irradiated by hydrogen, helium and heavy ions to simulate transmutation effects and damage which may be induced by neutrons under reactor conditions. The emphasis has been on surface modification: deposited layers on JET mirrors from the divertor and on near-surface damage in ion-irradiated targets. Analyses performed with ion beams, microscopy and spectro-photometry techniques have revealed: (i) the formation of multiple co-deposited layers; (ii) flaking-off of the layers already in the tokamak, despite the small thickness (130-200 nm) of the granular deposits; (iii) deposition of dust particles (0.2-5 mu m, 300-400 mm(-2)) composed mainly of tungsten and nickel; (iv) that the stepwise irradiation of up to 30 dpa by heavy ions (Mo, Zr or Nb) caused only small changes in the optical performance, in some cases even improving reflectivity due to the removal of the surface oxide layer; (v) significant reflectivity degradation related to bubble formation caused by the irradiation with He and H ions.

  • 18.
    Rubel, Marek
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Brezinsek, S.
    Coenen, J.
    Kreter, A.
    Moeller, S.
    Wienhold, P.
    Wauters, T.
    Fortuna-Zalesna, E.
    Tracer techniques for the assessment of material migration and surface modification of plasma-facing components2015In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, p. 280-284Article in journal (Refereed)
    Abstract [en]

    Tracer techniques were used in the TEXTOR tokamak to determine high-Z metal migration and the deposition of species used for plasma edge cooling or wall conditioning under different types of operation conditions. Volatile molybdenum hexa-fluoride, nitrogen-15 and oxygen-18 were used as markers in tokamak or ion cyclotron wall conditioning discharges (ICWC). The objective was to obtain qualitative and quantitative of a global and local deposition pattern and material mixing effects. The deposition and retention was studied on plasma-facing components, collector probes and test limiters. Optical spectroscopy and ex-situ analysis techniques were used to determine the plasma response to tracer injection and the modification of surface composition. Molybdenum and light isotopes were detected on all types of limiters and short-term probes retrieved from the vessel showing that both helium and nitrogen are trapped following wall conditioning and edge cooling. Only small amounts below 1 x 10(19) m(-2) of O-18 were detected on surfaces treated by oxygen-assisted ICWC.

  • 19.
    Ström, Petter
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tholerus, Simon
    Weckmann, Armin
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics. KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments (pre-2005), Physics. KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, T.
    Stefanikova, E.
    Zhou, Y.
    Zychor, I.
    et al.,
    Analysis of deposited layers with deuterium and impurity elements on samples from the divertor of JET with ITER-like wall2019In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 516, p. 202-213Article in journal (Refereed)
    Abstract [en]

    Inconel-600 blocks and stainless steel covers for quartz microbalance crystals from remote corners in the JET-ILW divertor were studied with time-of-flight elastic recoil detection analysis and nuclear reaction analysis to obtain information about the areal densities and depth profiles of elements present in deposited material layers. Surface morphology and the composition of dust particles were examined with scanning electron microscopy and energy-dispersive X-ray spectroscopy. The analyzed components were present in JET during three ITER-like wall campaigns between 2010 and 2017. Deposited layers had a stratified structure, primarily made up of beryllium, carbon and oxygen with varying atomic fractions of deuterium, up to more than 20%. The range of carbon transport from the ribs of the divertor carrier was limited to a few centimeters, and carbon/deuterium co-deposition was indicated on the Inconel blocks. High atomic fractions of deuterium were also found in almost carbon-free layers on the quartz microbalance covers. Layer thicknesses up to more than 1 micrometer were indicated, but typical values were on the order of a few hundred nanometers. Chromium, iron and nickel fractions were less than or around 1% at layer surfaces while increasing close to the layer-substrate interface. The tungsten fraction depended on the proximity of the plasma strike point to the divertor corners. Particles of tungsten, molybdenum and copper with sizes less than or around 1 micrometer were found. Nitrogen, argon and neon were present after plasma edge cooling and disruption mitigation. Oxygen-18 was found on component surfaces after injection, indicating in-vessel oxidation. Compensation of elastic recoil detection data for detection efficiency and ion-induced release of deuterium during the measurement gave quantitative agreement with nuclear reaction analysis, which strengthens the validity of the results.

  • 20.
    Tierens, W.
    et al.
    Max Planck Inst Plasma Phys, Garching, Germany..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Jonsson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vallejos Olivares, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Zuin, M.
    Consorzio RFX, Padua, Italy..
    et al.,
    Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments2019In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046001Article in journal (Refereed)
    Abstract [en]

    In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap antenna, and for a 4-strap WEST-like antenna. Although RAPLICASOL requires considerably fewer computational resources than TOPICA, we find that the predicted quantities of experimental interest (including reflection coefficients, coupling resistances, S- and Z-matrix entries, optimal matching settings, and even radiofrequency electric fields) are in good agreement provided we are careful to use the same geometry in both codes.

  • 21.
    Trier, E.
    et al.
    Max Planck Inst Plasma Phys, D-85748 Garching, Germany..
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Fridström, Richard
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Vallejos, Pablo
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Vignitchouk, Ladislas
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Zuin, M.
    Consorzio RFX, Corso Stati Uniti 4, I-35127 Padua, Italy..
    ELM-induced cold pulse propagation in ASDEX Upgrade2019In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed)
    Abstract [en]

    In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

  • 22. Vizvary, Z.
    et al.
    Bourdel, B.
    Garcia Carrasco, Alvaro
    KTH, School of Electrical Engineering and Computer Science (EECS), Fusion Plasma Physics.
    Lam, N.
    Leipold, F.
    Pitts, R. A.
    Reichle, R.
    Riccardo, V.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    De Temmerman, G.
    Thompson, V.
    Widdowson, A.
    Engineering design and analysis of an ITER-like first mirror test assembly on JET2017In: Fusion engineering and design, ISSN 0920-3796, E-ISSN 1873-7196, Vol. 123, p. 1054-1057Article in journal (Refereed)
    Abstract [en]

    The ITER first mirrors are the components of optical diagnostic systems closest to the plasma. Deposition may build up on the surfaces of the mirror affecting their ability to fulfil their function. However, physics modelling of this layer growth is fraught with uncertainty. A new experiment is underway on JET, under contract to ITER, with primary objective to test if, under realistic plasma and wall material conditions and with ITER-like first mirror aperture geometry, deposits do grow on first mirrors. This paper describes the engineering design and analysis of this mirror test assembly. The assembly was installed in the 2014-15 shutdown and will be removed in the 2016-17 shutdown.

  • 23. Wauters, T.
    et al.
    Möller, S.
    Kreter, A.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Crombé, K.
    Douai, D.
    Freisinger, M.
    Ivanova, Darya
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Kogut, D.
    Koslowski, R.
    Lyssoivan, A.
    Nicolai, D.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Philipps, V.
    Rack, M.
    Reimer, H.
    Sergienko, G.
    Vervier, M.
    Self-consistent application of ion cyclotron wall conditioning for co-deposited layer removal and recovery of tokamak operation on TEXTOR2013In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 53, no 12, p. 123001-Article in journal (Refereed)
    Abstract [en]

    This paper presents a demonstration experiment of ion cyclotron wall conditioning (ICWC) on TEXTOR covering all ITER wall conditioning aims and discusses the implications for ITER. O-2/He-ICWC applied to erode carbon co-deposits removed 6.6x10(21) C-atoms (39 pulses, 158 s cumulated discharge time). Large oxygen retention (71% of injected oxygen) prevented subsequent ohmic discharge initiation. Plasma operation was recovered by a 1h47 multi-pulse D-2-ICWC procedure including pumping time between pulses with duty cycle of 2 s/20 s, cleaning the vessel from oxygen impurities, followed by a 23 min He-ICWC procedure (2 s/20 s), applied to desaturate the deuterium-loaded walls. A stable ohmic discharge was established on the first attempt right after the recovery procedure. The discharges showed improved density control and only slightly increased oxygen characteristic radiation levels (1-1.5 times). After the recovery procedure 36% of the injected O-atoms remained retained in the vessel, derived from mass spectrometry measurements. This amount is in the estimated range for storage in remote areas obtained from surface analysis of locally exposed samples. The removed amount of oxygen by D-2 and He-ICWC obtained from mass spectrometry corresponds to the retention in plasma-wetted areas estimated by surface analysis. It is concluded that most of the removed oxygen stems from plasma-wetted areas while shadowed areas, e. g. behind poloidal limiters, may feature net retention of the discharge gas. On ITER, designed with a shaped first wall, the ICWC plasma-wetted area will approach the total surface area, reducing consequently the retention in remote areas. A tentative extrapolation of the carbon removal on TEXTOR to tritium removal from co-deposits on ITER in the 39 x 4 s O-2/He-ICWC discharges, including pumping time between the RF pulses, corresponds on ITER to a tritium removal in the order of the estimated retention per 400 s DT-burn (140-500 mgT (Shimada and Pitts 2011 J. Nucl. Mater. 415 S1013-6)).

1 - 23 of 23
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