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  • 151.
    Emmoth, Birger
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Kreter, A.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT.
    Jakubowski, M.
    Lehnen, M.
    Litnovsky, A.
    Petersson, P.
    Philipps, V.
    Possnert, G.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Schweer, B.
    Sundelin, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Unterberg, B.
    Wienhold, P.
    In-situ measurements of carbon and deuterium deposition using the fast reciprocating probe in TEXTOR2009Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 390-91, s. 179-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Silicon samples were exposed in the scrape-off layer of the TEXTOR plasma using a fast reciprocating probe, with the aim of studying carbon deposition and deuterium retention during Dynamic Ergodic Divertor (DED) operation. Separate samples were exposed for 300 ms at the flat-top phase of neutral beam heated discharges. The exposure conditions were varied on a shot-to-shot basis by external magnetic perturbations generated by the DED in the m/n = 3/1, DC regime, base configuration. Nuclear Reaction Analysis (NRA) was used to characterise collector sample surfaces after their exposure. Enhanced concentrations of both carbon and deuterium (C 3-10 x 10(16) at./cm(2), D 8-60 x 10(15) at./cm(2)) were found. The D/C ratio was less than unity which indicates that most of the carbon and deuterium were co-deposited. Carbon e-folding lengths of about 2 cm were found on both toroidal sides of the probe independent of DED perturbations.

  • 152. Eriksson, J.
    et al.
    Nocente, M.
    Binda, F.
    Cazzaniga, C.
    Conroy, S.
    Ericsson, G.
    Giacomelli, L.
    Gorini, G.
    Hellesen, C.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Hjalmarsson, A.
    Jacobsen, A. S.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Kiptily, V.
    Koskela, T.
    Mantsinen, M.
    Salewski, M.
    Schneider, M.
    Sharapov, S.
    Skiba, M.
    Tardocchi, M.
    Weiszflog, M.
    Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET2015Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, nr 12, artikel-id 123026Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations made in a JET experiment aimed at accelerating deuterons to the MeV range by third harmonic radio-frequency (RF) heating coupled into a deuterium beam are reported. Measurements are based on a set of advanced neutron and gamma-ray spectrometers that, for the first time, observe the plasma simultaneously along vertical and oblique lines of sight. Parameters of the fast ion energy distribution, such as the high energy cut-off of the deuteron distribution function and the RF coupling constant, are determined from data within a uniform analysis framework for neutron and gamma-ray spectroscopy based on a one-dimensional model and by a consistency check among the individual measurement techniques. A systematic difference is seen between the two lines of sight and is interpreted to originate from the sensitivity of the oblique detectors to the pitch-angle structure of the distribution around the resonance, which is not correctly portrayed within the adopted one dimensional model. A framework to calculate neutron and gamma-ray emission from a spatially resolved, two-dimensional deuteron distribution specified by energy/pitch is thus developed and used for a first comparison with predictions from ab initio models of RF heating at multiple harmonics. The results presented in this paper are of relevance for the development of advanced diagnostic techniques for MeV range ions in high performance fusion plasmas, with applications to the experimental validation of RF heating codes and, more generally, to studies of the energy distribution of ions in the MeV range in high performance deuterium and deuterium-tritium plasmas.

  • 153. Eriksson, L. -G
    et al.
    Hellsten, Torbjörn A K
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Holmström, Kerstin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas Joe
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brzozowski, Jerzy H.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Nave, F.
    Ongena, J.
    Zastrow, K. -D
    Simulation of fast ion contribution to toroidal rotation in ICRF heated jet plasmas2008Ingår i: EPS Conf. Plasma Phys., EPS - Europhys. Conf. Abstr., 2008, nr 3, s. 1679-1682Konferensbidrag (Refereegranskat)
  • 154. Eriksson, L. G.
    et al.
    Hellsten, Torbjörn A. K.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Nave, M. F. F.
    Brzozowski, Jerzy H.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Holmström, Kerstin
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Ongena, J.
    Zastrow, K. D.
    Holmström, K.
    Toroidal rotation in RF heated JET plasmas2009Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 51, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations of bulk plasma rotation in radio frequency (RF) heated JET discharges are reported. This study is concentrated on RF heated L-mode plasmas. In particular, the toroidal rotation profiles in plasmas heated by ion cyclotron resonance frequency (ICRF) waves and lower hybrid (LH) waves have been analysed. It is the first time that rotation profiles in JET plasmas with LH waves have been measured in dedicated discharges. It is found that the toroidal plasma rotation in the outer region of the plasmas is in the co-current direction irrespective of the heating scenario. An interesting feature is that the toroidal rotation profile appears to be hollow in many discharges at low plasma current, but a low current in itself does not seem to be a sufficient condition for finding such profiles. Fast ion transport and finite orbit width effects are mechanisms that could explain hollow rotation profiles. This possibility has been investigated by numerical simulations of the torque on the bulk plasma due to fast ICRF accelerated ions. The obtained torque is used in a transport equation for the toroidal momentum density to estimate the effect on the thermal bulk plasma rotation profile.

  • 155. Eriksson, L. -G
    et al.
    Hellsten, Torbjörn
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Nave, F.
    Brzozowski, Jerzy
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Holmström, Kerstin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Johnson, Thomas J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Ongena, J.
    Zastrow, K. -D
    Toroidal rotation in RF heated JET plasmas2007Ingår i: RADIO FREQUENCY POWER IN PLASMAS, 2007, Vol. 933, s. 59-62Konferensbidrag (Refereegranskat)
    Abstract [en]

    Experiments have been carried out on JET aimed at studying rotation in RF heated plasmas with low external momentum input. Both plasmas with Ion Cyclotron Resonance Frequency (ICRF) heating and Lower Hybrid Current Drive (LHCD) have been investigated. The rotation profiles are measured by Charge Exchange recombination spectroscopy, using short diagnostic Neutral Beam Injection (NBI) pulses. Moreover, the temporal evolution of the central rotation could in some cases be deduced from MHD activity. While most of the measurements were focussed on ICRF heating, the profiles measured in plasmas with LHCD are interesting since they are the first reported from JET in such plasmas. In particular, they allowed for studies of rotation in RF heated plasmas with q>1. The experimental results are presented together with an analysis of the torque from ICRF heated fast ions.

  • 156. Eriksson, L. G.
    et al.
    Johnson, Thomas J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Mayoral, M. L.
    Coda, S.
    Sauter, O.
    Buttery, R. J.
    McDonald, D.
    Hellsten, Torbjörn A. K.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Mantsinen, M. J.
    Mueck, A.
    Noterdaeme, J. M.
    Santala, M.
    Westerhor, E.
    de Vries, P.
    On ion cyclotron current drive for sawtooth control2006Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 46, nr 10, s. S951-S964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experiments using ion cyclotron current drive (ICCD) to control sawteeth are presented. In particular, discharges demonstrating shortening of fast ion induced long sawteeth reported in (Eriksson et al 2004 Phys. Rev. Lett. 92 235004) by ICCD have been analysed in detail. Numerical simulations of the ICCD driven currents are shown to be consistent with the experimental observations. They support the hypothesis that an increase in the magnetic shear, due to the driven current, at the surface where the safety factor is unity was the critical factor for the shortening of the sawteeth. In view of the potential utility of ICCD, the mechanisms for the current drive have been further investigated experimentally. This includes the influence of the averaged energy of the resonating ions carrying the current and the spectrum of the launched waves. The results of these experiments are discussed in the light of theoretical considerations.

  • 157. Esser, H. G.
    et al.
    Philipps, V.
    Freisinger, M.
    Widdowson, A.
    Heinola, K.
    Kirschner, A.
    Moeller, S.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brezinsek, S.
    Huber, A.
    Matthews, G. F.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Sergienko, G.
    Material deposition on inner divertor quartz-micro balances during ITER-like wall operation in JET2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 463, s. 796-799Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The migration of beryllium, tungsten and carbon to remote areas of the inner JET-ILW divertor and the accompanying co-deposition of deuterium has been investigated using post-mortem analysis of the housings of quartz-micro balances (QMBs) and their quartz crystals. The analysis of the deposition provides that the rate of beryllium atoms is significantly reduced compared to the analogue deposition rate of carbon during the carbon wall conditions (JET-C) at the same locations of the QMBs. A reduction factor of 50 was found at the entrance gap to the cryo-pumps while it was 14 under tile 5, the semi-horizontal target plate. The deposits consist of C/Be atomic ratios of typically 0.1-0.5 showing an enrichment of carbon in remote areas compared to directly exposed areas with less carbon. The deuterium retention fraction D/Be is between 0.3 and 1 at these unheated locations in the divertor.

  • 158. Faghihi, M.
    et al.
    Scheffel, Jan
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Stability of Small Axial Wavelength Internal Kink Modes of an Anisotropic Plasma1987Rapport (Övrigt vetenskapligt)
  • 159. Faghihi, M.
    et al.
    Scheffel, Jan
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Stability of Small Axial Wavelength Internal Kink Modes of an Anisotropic Plasma1987Ingår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 38, s. 495-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The double adiabatic equations are used to study the stability of a cylindrical Z-pinch with respect to small axial wavelength, internal kink (m ≥ 1) modes. It is found that marginally (ideally) unstable, isotropic equilibria are stabilized. Also, constant-current-density equilibria can be stabilized for P⊥ > P∥ and large β⊥

  • 160. Faghihi, M.
    et al.
    Scheffel, Jan
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Stability of Small Axial Wavelength Internal Kink Modes of an Anisotropic Plasma: Corrigendum1988Ingår i: Journal of Plasma Physics, ISSN 0022-3778, E-ISSN 1469-7807, Vol. 40, s. 603-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A minor correction, having no major influence on our results, is reported here.

  • 161. Falchetto, G. L.
    et al.
    Coster, D.
    Coelho, R.
    Scott, B. D.
    Figini, L.
    Kalupin, D.
    Nardon, E.
    Nowak, S.
    Alves, L. L.
    Artaud, J. F.
    Basiuk, V.
    Bizarro, Jao P. S.
    Boulbe, C.
    Dinklage, A.
    Farina, D.
    Faugeras, B.
    Ferreira, J.
    Figueiredo, A.
    Huynh, Ph
    Imbeaux, F.
    Ivanova-Stanik, I.
    Johnson, Thomas
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Klingshirn, H-J
    Konz, C.
    Kus, A.
    Marushchenko, N. B.
    Pereverzev, G.
    Owsiak, M.
    Poli, E.
    Peysson, Y.
    Reimer, R.
    Signoret, J.
    Sauter, O.
    Stankiewicz, R.
    Strand, P.
    Voitsekhovitch, I.
    Westerhof, E.
    Zok, T.
    Zwingmann, W.
    The European Integrated Tokamak Modelling (ITM) effort: achievements and first physics results2014Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 54, nr 4, s. 043018-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A selection of achievements and first physics results are presented of the European Integrated Tokamak Modelling Task Force (EFDA ITM-TF) simulation framework, which aims to provide a standardized platform and an integrated modelling suite of validated numerical codes for the simulation and prediction of a complete plasma discharge of an arbitrary tokamak. The framework developed by the ITM-TF, based on a generic data structure including both simulated and experimental data, allows for the development of sophisticated integrated simulations (workflows) for physics application.The equilibrium reconstruction and linear magnetohydrodynamic (MHD) stability simulation chain was applied, in particular, to the analysis of the edgeMHDstability of ASDEX Upgrade type-I ELMy H-mode discharges and ITER hybrid scenario, demonstrating the stabilizing effect of an increased Shafranov shift on edge modes. Interpretive simulations of a JET hybrid discharge were performed with two electromagnetic turbulence codes within ITM infrastructure showing the signature of trapped-electron assisted ITG turbulence. A successful benchmark among five EC beam/ray-tracing codes was performed in the ITM framework for an ITER inductive scenario for different launching conditions from the equatorial and upper launcher, showing good agreement of the computed absorbed power and driven current. Selected achievements and scientific workflow applications targeting key modelling topics and physics problems are also presented, showing the current status of the ITM-TF modelling suite.

  • 162.
    Fazinic, Stjepko
    et al.
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Tadic, Tonic
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Vuksic, Marin
    Rudjer Boskovic Inst, Bijenicka 54, Zagreb 10000, Croatia..
    Rubel, Marek
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Fortuna-Zalesna, Elibieta
    Warsaw Univ Technol, Fac Mat Sci & Technol, Woloska 141, PL-02507 Warsaw, Poland..
    Widdowson, Anna
    Culham Sci Ctr, Culham Ctr Fus Energy, Abingdon OX14 3DB, Oxon, England..
    Ion Microbeam Analyses of Dust Particles and Codeposits from JET with the ITER-Like Wall2018Ingår i: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, nr 9, s. 5744-5752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Generation of metal dust in the JET tokamak with the ITER-like wall (ILW) is a topic of vital interest to next-step fusion devices because of safety issues with plasma operation. Simultaneous Nuclear Reaction Analysis (NRA) and Particle Induced X-ray Emission (PIXE) with a focused four MeV He-3 microbeam was used to determine the composition of dust particles related to the JET operation with the ILW. The focus was on "Be-rich particles" collected from the deposition zone on the inner divertor tile. The particles found are composed of a mix of codeposited species up to 120 m in size with a thickness of 30-40 mu m, The main constituents are D from the fusion fuel, Be and W from the main plasma-facing components, and Ni and Cr from the Inconel grills of the antennas for auxiliary plasma heating. Elemental concentrations were estimated by iterative NRA-PIXE analysis. Two types of dust particles were found: (i) larger Be-rich particles with Be concentrations above 90 at% with a deuterium presence of up to 3.4 at% and containing Ni (1-3 at%), Cr (0.4-0.8 at%), W (0.2-0.9 at%), Fe (0.3-0.6 at%), and Cu and Ti in lower concentrations and (ii) small particles rich in Al and/or Si that were in some cases accompanied by other elements, such as Fe, Cu, or Ti or W and Mo.

  • 163. Field, A. R.
    et al.
    Frassinetti, Lorenzo
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Fusionsplasmafysik.
    Maggi, C.
    Saarelma, S.
    Inter-ELM power losses and their dependence on pedestal parameters in JET C-And ITER-like wall H-mode plasmas2018Ingår i: 45th EPS Conference on Plasma Physics, EPS 2018, European Physical Society (EPS) , 2018, s. 1636-1639Konferensbidrag (Refereegranskat)
  • 164. Fortuna, E.
    et al.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Philipps, V.
    Kurzydlowski, K. J.
    Mertens, Ph.
    Miskiewicz, M.
    Pisarek, M.
    Van Oost, G.
    Zielinski, W.
    Properties of co-deposited layers on graphite high heat flux components at the TEXTOR tokamak2007Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 367, nr B, s. 1507-1511Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of this work was to examine the structure, composition and properties of co-deposited films from the TEXTOR tokamak. Hydrogenated films formed on the toroidal belt pump limiter (ALT-II), and on the ICRF antenna grill were studied using a set of material analysis techniques. Plasma edge diagnostics were used to assess the parameters influencing the film formation during discharges auxiliary heated by ICRF. The essential results are summarized as follows: (i) the distribution of plasma impurities co-deposited in the films is non-uniform and (ii) the surface topography, crystallographic structure, fuel retention and composition (i.e., content of re-deposited plasma impurities) of the films show significant diversity depending on the location where they were formed. These differences are associated with the local geometry, the tokamak operation scenarios and the resulting plasma edge properties.

  • 165. Fortuna, E.
    et al.
    Rubel, Marek J.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Psoda, M.
    Andrzejczuk, M.
    Kurzydlowski, K. J.
    Miskiewicz, M.
    Philipps, V.
    Pospieszczyk, A.
    Sergienko, G.
    Spychalski, M.
    Zielinski, W.
    Plasma-induced damage of tungsten coatings on graphite limiters2007Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T128, s. 162-165Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vaccum plasma sprayed tungsten coatings with an evaporated sandwich Re - W interlayer on graphite limiter blocks were studied after the experimental campaign in the TEXTOR tokamak. The coating morphology was modified by high-heat loads and co-deposition of species from the plasma. Co-deposits contained fuel species, carbon, boron and silicon. X-ray diffractometer phase analysis indicated the coexistence of metallic tungsten and its carbides (WC and W2C) and boride (W2B). In the Re - W layer the presence of carbon was detected in a several micrometres thick zone. In the overheated part of the limiter, the Re - W layer was transformed into a sigma phase.

  • 166. Fortuna-Zalesna, E.
    et al.
    Grzonka, J.
    Moon, Sunwoo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Petersson, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    Fine metal dust particles on the wall probes from JET-ILW2017Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T170, artikel-id 014038Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Collection and ex situ studies of dust generated in controlled fusion devices during plasma operation are regularly carried out after experimental campaigns. Herewith results of the dust survey performed in JET after the second phase of operation with the metal ITER-like wall (2013-2014) are presented. For the first-time-ever particles deposited on silicon plates acting as dust collectors installed in the inner and outer divertor have been examined. The emphasis is on analysing metal particles (Be and W) with the aim to determine their composition, size and surface topography. The most important is the identification of beryllium dust in the form of droplets (both splashes and spherical particles), flakes of co-deposits and small fragments of Be tiles. Tungsten and nickel rich (from Inconel) particles are also identified. Nitrogen from plasma edge cooling has been detected in all types of particles. They are categorized and the origin of various constituents is discussed.

  • 167. Fortuna-Zalesna, E.
    et al.
    Grzonka, J.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Garcia Carrasco, Alvaro
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Widdowson, A.
    Baron-Wiechec, A.
    Ciupinski, L.
    Studies of dust from JET with the ITER-Like Wall: Composition and internal structure2017Ingår i: NUCLEAR MATERIALS AND ENERGY, ISSN 2352-1791, Vol. 12, s. 582-587Artikel i tidskrift (Refereegranskat)
    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.

  • 168. Fortuna-Zalesna, E.
    et al.
    Weckmann, Armin
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Grozonka, J.
    Rubel, Marek
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Esser, H. G.
    Freisinger, M.
    Kreter, A.
    Kischner, A.
    Sergienko, G.
    Ström, Petter
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dust Survey Following the Final Shutdown of TEXTOR: Metal Particles and Fuel Retention2016Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. T167, artikel-id 014059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The work presents results of a broad TEXTOR dust survey in terms of its composition, structure, distribution and fuel content. The dust particles were collected after final shutdown of TEXTOR in December 2013. Fuel retention, as determined by thermal desorption, varied significantly, even by two orders of magnitude, dependent on the dust location in the machine. Dust structure was examined by means of scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, focused ion beam and scanning transmission electron microscopy. Several categories of dust have been identified. Carbon-based stratified and granular deposits were dominating, but the emphasis in studies was on metal dust. They were found in the form of small particles, small spheres, flakes and splashes which formed “comet”-like structures clearly indicating directional effects in the impact on surfaces of plasma-facing components. Nickel-rich alloys from the Inconel liner and iron-based ones from various diagnostic holders were the main components of metal-containing dust, but also molybdenum and tungsten debris were detected. Their origin is discussed.

  • 169.
    Frassinetti, L.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Menmuir, S.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Spontaneous quasi single helicity regimes in EXTRAP T2R reversed-field pinch2007Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 14, nr 11Artikel i tidskrift (Refereegranskat)
  • 170.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Inter-ELM evolution of the pedestal structure in JET-ILW2016Ingår i: 24th European Fusion Physics Workshop, 28-30 November 2016, 2016Konferensbidrag (Övrigt vetenskapligt)
  • 171.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Magnetic perturbation and dynamo generation effects on 3-d flows in RFPs2010Ingår i: 18th European Fusion Physics Workshop, December 2010, Mayrhofen, Austria, 2010Konferensbidrag (Övrigt vetenskapligt)
  • 172.
    Frassinetti, Lorenzo
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Wall diffusion time in EXTRAP T2R and possible applications to tokamaks2012Konferensbidrag (Övrigt vetenskapligt)
  • 173.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Alfier, A.
    Pasqualotto, R.
    Bonomo, F.
    Innocente, P.
    Heat diffusivity model and temperature simulations in RFX-mod2008Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 48, nr 4, s. 045007-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The core transport properties of reversed field pinch (RFP) plasmas in the standard regime are generally associated with a high level of magnetic chaos. Indeed, in the RFX-mod RFP device, the core temperature profile is often very flat, indicating that the heat diffusivity is very high. In contrast, the temperature edge profile has a steep gradient, indicating that the edge is characterized by low heat transport. These simple experimental evidences are the basis of a heat diffusivity model that is used as an input to a numerical code for plasma temperature simulation. The simulated temperature reproduces with good accuracy both the experimental T, time evolution and its radial profiles in different plasma scenarios, showing that the model is useful for estimating the plasma heat diffusivity. This work suggests that the heat transport properties in the RFP plasma core are dominated by magnetic chaos in standard discharges and suggests a simple way to estimate electron heat diffusivity from density, input power and magnetic fluctuation measurements.

  • 174.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    ELM losses in high triangularity plasmas in JET with the metal and carbon wall2012Ingår i: EFDA-JET Science Meeting on ELM Studies, June 25, 2012, 2012Konferensbidrag (Övrigt vetenskapligt)
  • 175.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Study on global and pedestal confinement in metal and carbon wall2012Ingår i: EFDA-JET Science Meeting on Pedestal Studies, June 11, 2012, 2012Konferensbidrag (Övrigt vetenskapligt)
  • 176.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Alper, B
    Bourdelle, C
    Brezinsek, S
    Bucalossi, J
    Buratti, P
    Crisanti, C
    Challis, C
    Flanagan, J
    Giroud, C
    Groth, M
    Hobirk, J
    Joffrin, E
    Leyland, M
    Lomas, P
    Kampeenars, M
    Maslov, M
    Matthews, G
    Mayoral, M
    McCormick, K
    Neu, R
    Nunes, I
    Rimini, F
    Saarelma, S
    Core versus edge confinement in JET with the ILW compared to the CFC first-wall2012Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics, 2012, s. 1334-1337Konferensbidrag (Refereegranskat)
  • 177.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M. N. A.
    Saarelma, S.
    Boom, J. E.
    Delabie, E.
    Flanagan, J.
    Kempenaars, M.
    Giroud, C.
    Lomas, P.
    Meneses, L.
    Maggi, C. S.
    Menmuir, S.
    Nunes, I.
    Rimini, F.
    Stefanikova, E.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Urano, H.
    Verdoolaege, G.
    Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low-triangularity H-mode plasmas in JET-ILW2017Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, nr 1, artikel-id 061012Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dimensionless collisionality scan in low-triangularity plasmas in the Joint European Torus with the ITER-like wall (JET-ILW) has been performed. The increase of the normalized energy confinement (defined as the ratio between thermal energy confinement and Bohm confinement time) with decreasing collisionality is observed. Moreover, at low collisionality, a confinement factor H-98, comparable to JET-C, is achieved. At high collisionality, the low normalized confinement is related to a degraded pedestal stability and a reduction in the density-profile peaking. The increase of normalized energy confinement is due to both an increase in the pedestal and in the core regions. The improvement in the pedestal is related to the increase of the stability. The improvement in the core is driven by (i) the core temperature increase via the temperature-profile stiffness and by (ii) the density-peaking increase driven by the low collisionality. Pedestal stability analysis performed with the ELITE (edge-localized instabilities in tokamak equilibria) code has a reasonable qualitative agreement with the experimental results. An improvement of the pedestal stability with decreasing collisionality is observed. The improvement is ascribed to the reduction of the pedestal width, the increase of the bootstrap current and the reduction of the relative shift between the positions of the pedestal density and pedestal temperature. The EPED1 model predictions for the pedestal pressure height are qualitatively well correlated with the experimental results. Quantitatively, EPED1 overestimates the experimental pressure by 15-35%. In terms of the pedestal width, a correct agreement (within 10-15%) between the EPED1 and the experimental width is found at low collisionality. The experimental pedestal width increases with collisionality. Nonetheless, an extrapolation to low-collisionality values suggests that the width predictions from the KBM constraint are reasonable for ITER.

  • 178.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M. N. A.
    Scannell, R.
    Osborne, T. H.
    Flanagan, J.
    Kempenaars, M.
    Maslov, M.
    Pasqualotto, R.
    Walsh, M.
    Spatial resolution of the JET Thomson scattering system2012Ingår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, nr 1, s. 013506-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The instrument function of the high resolution Thomson scattering (HRTS) diagnostic in the Joint European Torus (JET) has been calculated for use in improved pedestal profile analysis. The full width at half maximum (FWHM) of the spatial instrument response is (22 +/- 1) mm for the original HRTS system configuration and depends on the particular magnetic topology of the JET plasmas. An improvement to the optical design of the laser input system is presented. The spatial smearing across magnetic flux surfaces is reduced in this design. The new input system has been implemented (from JPN 78742, July 2009) and the HRTS instrument function corresponding to the new configuration has been improved to approximately FWHM = (9.8 +/- 0.8) mm. The reconstructed instrument kernels are used in combination with an ad hoc forward deconvolution procedure for pedestal analysis. This procedure produces good results for both the old and new setups, but the reliability of the deconvolved profiles is greatly reduced when the pedestal width is of the same order as, or less than the FWHM of the instrument kernel.

  • 179.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Saarelma, S
    Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low triangularity H-mode plasmas in JET-ILW2015Ingår i: ITPA-PEP meeting, 22-23 October 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 180.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M
    Saarelma, S.
    Boom, J. E.
    Delabie, E.
    Flanagan, J.
    Kempenaars, C. M.
    Giroud, G.
    Lomas, P.
    Meneses, L.
    Menmuir, S.
    Nunes, I.
    Rimini, F.
    Confinement and pedestal in dimensionless collisionality scans of low triangularity H-mode plasmas in JET-ILW2015Ingår i: 42nd European Physical Society Conference on Plasma Physics, EPS 2015, European Physical Society (EPS) , 2015Konferensbidrag (Refereegranskat)
  • 181.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Beurskens, M.N.A.
    McDonald, D.C.
    Hobirk, J.
    Zarzoso, D.
    Buratti, P.
    Crisanti, F.
    Challis, C.
    Giovannozzi, E.
    Joffrin, E.
    Lomas, P.
    Lonnroth, J.
    Maggi, C.
    Nunes, I.
    Saarelma, S.
    Saibene, G.
    et al.,
    Pedestal confinement in hybrid versus baseline plasmas in JET2010Ingår i: 37th European Physical Society Conference on Plasma Physics. Contributed Papers, 2010, s. P1.1031-Konferensbidrag (Refereegranskat)
  • 182.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brunsell, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Khan, Muhammad Waqas Mehmood
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Olofsson, Erik
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Active feedback control of QSH in EXTRAP-T2R2008Konferensbidrag (Refereegranskat)
  • 183.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James Robert
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Spontaneous QSH in the EXTRAP T2R reversed-field pinch2007Ingår i: 34th EPS Conference on Plasma Physics 2007, EPS 2007 - Europhysics Conference Abstracts, 2007, s. 579-582Konferensbidrag (Refereegranskat)
  • 184.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Cecconello, Marco
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Heat transport modelling in EXTRAP T2R2009Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 49, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A model to estimate the heat transport in the EXTRAP T2R reversed field pinch (RFP) is described. The model, based on experimental and theoretical results, divides the RFP electron heat diffusivity chi(e) into three regions, one in the plasma core, where chi(e) is assumed to be determined by the tearing modes, one located around the reversal radius, where chi(e) is assumed not dependent on the magnetic fluctuations and one in the extreme edge, where high chi(e) is assumed. The absolute values of the core and of the reversal chi(e) are determined by simulating the electron temperature and the soft x-ray and by comparing the simulated signals with the experimental ones. The model is used to estimate the heat diffusivity and the energy confinement time during the flat top of standard plasmas, of deep F plasmas and of plasmas obtained with the intelligent shell.

  • 185.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Experiments and modelling of active quasi-single helicity regime generation in a reversed field pinch2009Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 49, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The interaction of a static resonant magnetic perturbation (RMP) with a tearing mode (TM) is becoming a relevant topic in fusion plasma physics. RMPs can be generated by active coils and then used to affect the properties of TMs and of the corresponding magnetic islands. This paper shows how the feedback system of the EXTRAP T2R reversed field pinch (RFP) can produce a RMP that affects a rotating TM and stimulate the transition to the so-called quasi-single helicity (QSH) regime, a RFP plasma state characterized by a magnetic island surrounded by low magnetic chaos. The application of the RMP can increase the QSH probability up to 10% and enlarge the size of the corresponding island. Part of the experimental results are supported by a theoretical study that models the effect of the active coils on the magnetic island.

  • 186.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Brunsell, Per R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Drake, James R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik. KTH, Skolan för elektro- och systemteknik (EES), Centra, Alfvénlaboratoriet.
    Heat transport in the quasi-single-helicity islands of EXTRAP T2R2009Ingår i: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 16, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The heat transport inside the magnetic island generated in a quasi-single-helicity regime of a reversed-field pinch device is studied by using a numerical code that simulates the electron temperature and the soft x-ray emissivity. The heat diffusivity chi(e) inside the island is determined by matching the simulated signals with the experimental ones. Inside the island, chi(e) turns out to be from one to two orders of magnitude lower than the diffusivity in the surrounding plasma, where the magnetic field is stochastic. Furthermore, the heat transport properties inside the island are studied in correlation with the plasma current and with the amplitude of the magnetic fluctuations.

  • 187.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brunsell, Per
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Setiadi, C
    Fridström, Richard
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Khan, W
    Drake, J
    TM locking and unlocking mechanism to an external resonant field2014Ingår i: Meeting of the Nordic Research Units in EUROfusion, 2014Konferensbidrag (Övrigt vetenskapligt)
  • 188.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Brunsell, P.R.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Fridström, R
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Setiadi, C
    Khan, W
    EXTEAP T2R overview2015Ingår i: 17th IEA/RFP Workshop, 26-29 october 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 189.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Challis, C
    The role of the pedestal on the confinement in hybrids and baseline plasmas2014Ingår i: EUROfusion Science Meeting on Pedestal Studies, Sept 11, 2014, 2014Konferensbidrag (Övrigt vetenskapligt)
  • 190.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dodt, D.
    Beurskens, M. N. A.
    Sirinelli, A.
    Boom, J. E.
    Eich, T.
    Flanagan, J.
    Giroud, C.
    Jachmich, M. S.
    Kempenaars, M.
    Lomas, P.
    Maddison, G.
    Maggi, C.
    Neu, R.
    Nunes, I.
    von Thun, C. Perez
    Sieglin, B.
    Stamp, M.
    Effect of nitrogen seeding on the energy losses and on the time scales of the electron temperature and density collapse of type-I ELMs in JET with the ITER-like wall2015Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 55, nr 2, artikel-id 023007Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The baseline type-I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called the ITER-like wall, JET-ILW). The first JET-ILW results show that the confinement is degraded by 20-30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained to date in JET-ILW baseline plasmas only in the high triangularity shape using N-2 seeding. This work compares the energy losses during ELMs and the corresponding time scales of the temperature and density collapse in JET-ILWbaseline plasmas with and without N-2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, is similar to 2ms in the JET-ILW and lower than 1 ms in the JET-C. The energy losses are in the range Delta W-ELM/W-ped approximate to 7-12% in the JET-ILWand Delta W-ELM/W-ped approximate to 10-20% in JET-C, and fit relatively well with earlier multi-machine empirical scalings of Delta W-ELM/W-ped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. Most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale similar to 8-10 ms (hereafter called slow transport events), that can lead to losses in the range Delta W-slow/W-ped approximate to 15-22%, slightly larger than the losses in JET-C. The N-2 seeding in JET-ILW significantly affects the ELMs. The JET-ILW plasmas with N-2 seeding are characterized by ELM energy losses and time scales similar to the JET-C and by the absence of the slow transport events.

  • 191.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dodt, D
    Beurskens, M
    Sirenelli, A
    Eich, T
    Flanagan, J
    Giroud, C
    Jachmich, S
    Kampenaars, M
    Lomas, P
    Maddison, M
    Neu, R
    Nunes, I
    Sieglin, B
    ELM energy losses in baseline plasma in JET with the ILW compared to the CFC first-wall2013Ingår i: 40th EPS Conference on Plasma Physics, EPS 2013: 40th EPS Conference on Plasma Physics, EPS 2013; Espoo; Finland; 1 July 2013 through 5 July 2013, 2013, , s. 4Konferensbidrag (Refereegranskat)
  • 192.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dunne, M
    Beurskens, M
    Wolfrum, E
    ELM dynamics in AUG and JET with & without Nitrogen seeding2014Ingår i: IPTA-PEP meeting, 2014, 2014Konferensbidrag (Övrigt vetenskapligt)
  • 193.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dunne, M
    Beurskens, M
    Wolfrum, E
    ELM energy losses in AUG with & without Nitrogen seeding2015Ingår i: 15th International Workshop on H-mode Physics and Transport Barriers, 19-21 October 2015, 2015Konferensbidrag (Övrigt vetenskapligt)
  • 194.
    Frassinetti, Lorenzo
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Fusionsplasmafysik.
    Dunne, M. G.
    Beurskens, M.
    Wolfrum, E.
    Bogomolov, A.
    Carralero, D.
    Cavedon, M.
    Fischer, R.
    Laggner, F. M.
    McDermott, R. M.
    Meyer, H.
    Tardini, G.
    Viezzer, E.
    ELM behavior in ASDEX Upgrade with and without nitrogen seeding2017Ingår i: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, nr 2, artikel-id 022004Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Type I ELM behavior in ASDEX Upgrade with full W plasma facing components is studied in terms of time scales and energy losses for a large set of shots characterized by similar operational parameters but different nitrogen seeding rate and input power. ELMs with no nitrogen can have two typical behaviors, that can be classified depending on their duration, the long and the short ELMs. The work shows that both short and long ELMs have a similar first phase, but the long ELMs are characterized by a second phase with further energy losses. The second phase disappears when nitrogen is seeded with a flux rate above 10(22) (e s(-1)). The phenomenon is compatible with a threshold effect. The presence of the second phase is related to a high divertor/scrape-off layer (SOL) temperature and/or to a low pedestal temperature. The ELM energy losses of the two phases are regulated by different mechanisms. The energy losses of the first phase increase with nitrogen which, in turn, produce the increase of the pedestal temperature. So the energy losses of the first phase are regulated by the pedestal top parameters and the increase with nitrogen is due to the decreasing pedestal collisionality. The energy losses of the second phase are related to the divertor/ SOL conditions. The long ELMs energy losses increase with increasing divertor temperature and with the number of the expelled filaments. In terms of the power lost by the plasma, the nitrogen seeding increases the power losses of the short ELMs. The long ELMs have a first phase with power losses comparable to the short ELMs losses. Assuming no major difference in the wetted area, these results suggest that (i) the nitrogen might increase the divertor heat fluxes during the short ELMs and that (ii) the long ELMs, despite the longer time scale, are not beneficial in terms of divertor heat loads.

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