Neoclassical and turbulent heavy impurity transport in tokamak core plasmas are determined by main ion temperature, density and toroidal rotation profiles. Thus, in order to understand and prevent experimental behaviour of W accumulation, flux-driven integrated modelling of main ion heat and particle transport over multiple confinement times is a vital prerequisite. For the first time, the quasilinear gyrokinetic code QuaLiKiz is applied for successful predictions of core kinetic profiles in an ASDEX Upgrade H-mode discharge in the turbulence dominated region within the integrated modelling suite JETTO. Neoclassical contributions are calculated by NCLASS; auxiliary heat and particle deposition profiles due to NBI and ECRH are prescribed from previous analysis with TRANSP. Turbulent and neoclassical contributions are insufficient in explaining main ion heat and particle transport inside the q = 1 surface, necessitating the prescription of further transport coefficients to mimic the impact of MHD activity on central transport. The ion to electron temperature ratio at the simulation boundary at p tor=0.85 stabilizes ion scale modes while destabilizing ETG modes when significantly exceeding unity. Careful analysis of experimental measurements using Gaussian process regression techniques is carried out to explore reasonable uncertainties. In following trace W impurity transport simulations performed with additionally NEO, neoclassical transport under consideration of poloidal asymmetries alone is found to be insufficient to establish hollow central W density profiles. Reproduction of these conditions measured experimentally is found possible only when assuming the direct impact of a saturated (m, n) = (1, 1) MHD mode on heavy impurity transport.

VL - 59 IS - 1 U1 -FP

U2 -IMT

U5 - 6d42c99c474c747f17f4b44236cecb27 ER - TY - JOUR T1 - ELM-induced cold pulse propagation in ASDEX Upgrade JF - Plasma Physics and Controlled Fusion Y1 - 2019 A1 - Trier, E. A1 - Wolfrum, E. A1 - Willensdorfer, M. A1 - Yu, Q. A1 - Hoelzl, M. A1 - Orain, F. A1 - Ryter, F. A1 - Angioni, C. A1 - Bernert, M. A1 - Vanovac, B. A1 - Dunne, M. G. A1 - Denk, S. S. A1 - Fuchs, J. C. A1 - Fischer, R. A1 - Hennequin, P. A1 - Kurzan, B. A1 - Mink, F. A1 - Mlynek, A. A1 - Odstrcil, T. A1 - Schneider, P. A. A1 - Stroth, U. A1 - Tardini, G. A1 - ASDEX Upgrade Team A1 - EUROfusion MST1 Team AB - 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. VL - 61 IS - 4 U1 - FP U2 - TP U5 - 0279758ced9029d70a2148b4f3b6cd99 ER - TY - JOUR T1 - Overview of physics studies on ASDEX Upgrade JF - Nuclear Fusion Y1 - 2019 A1 - Meyer, H. A1 - Angioni, C. A1 - C.G. Albert A1 - N. Arden A1 - R. Arredondo Parra A1 - Asunta, O. A1 - de Baar, M. A1 - Balden, M. A1 - V. Bandaru A1 - Behler, K. A1 - Bergmann, A. A1 - Bernardo, J. A1 - Bernert, M. A1 - A. Biancalani A1 - Bilato, R. A1 - Birkenmeier, G. A1 - Blanken, T. C. A1 - Bobkov, V. A1 - Bock, A. A1 - Bolzonella, T. A1 - A. Bortolon A1 - B. Böswirth A1 - Bottereau, C. A1 - Bottino, A. A1 - van den Brand, H. A1 - Brezinsek, S. A1 - Brida, D. A1 - Brochard, F. A1 - C. Bruhn A1 - Buchanan, J. A1 - Buhler, A. A1 - Burckhart, A. A1 - Camenen, Y. A1 - D. Carlton A1 - Carr, M. A1 - Carralero, D. A1 - C. Castaldo A1 - Cavedon, M. A1 - C. Cazzaniga A1 - S. Ceccuzzi A1 - Challis, C. A1 - Chankin, A. A1 - Chapman, S. A1 - C. Cianfarani A1 - Clairet, F. A1 - Coda, S. A1 - Coelho, R. A1 - Coenen, J. W. A1 - Colas, L. A1 - Conway, G. D. A1 - Costea, S. A1 - Coster, D. P. A1 - Cote, T. B. A1 - Creely, A. A1 - G. Croci A1 - Cseh, G. A1 - Czarnecka, A. A1 - I. Cziegler A1 - den Harder, N. A1 - Jaulmes, F. A1 - Kantor, M. A1 - Karhunen, J. A1 - Miettunen, J. A1 - Vanovac, B. A1 - EUROfusion MST1 Team A1 - et al. AB - The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation (q 95 = 5.5, ) at low density. Higher installed electron cyclotron resonance heating power 6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m−1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and E r allow for inter ELM transport analysis confirming that E r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of ‘natural’ no ELM regimes have been extended. Stable I-modes up to have been characterised using -feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle—measured for the first time—or the cross-phase angle of and fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvénic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO. PB - IOP Publishing VL - 59 IS - 11 U1 - FP U2 - TP U5 - 87a8b0ff65b4dc41f80072ac74a6868a ER - TY - JOUR T1 - High Z neoclassical transport: Application and limitation of analytical formulae for modelling JET experimental parameters JF - Physics of Plasmas Y1 - 2018 A1 - Breton, S. A1 - Casson, F. J. A1 - Bourdelle, C. A1 - Angioni, C. A1 - Belli, E. A1 - Camenen, Y. A1 - Citrin, J. A1 - Garbet, X. A1 - Sarazin, Y. A1 - Sertoli, M. A1 - JET Contributors AB -Heavy impurities, such as tungsten (W), can exhibit strongly poloidally asymmetric density profiles in rotating or radio frequency heated plasmas. In the metallic environment of JET, the poloidal asymmetry of tungsten enhances its neoclassical transport up to an order of magnitude, so that neoclassical convection dominates over turbulent transport in the core. Accounting for asymmetries in neoclassical transport is hence necessary in the integrated modeling framework. The neoclassical drift kinetic code, NEO [E. Belli and J. Candy, Plasma Phys. Controlled Fusion P50, 095010 (2008)], includes the impact of poloidal asymmetries on W transport. However, the computational cost required to run NEO slows down significantly integrated modeling. A previous analytical formulation to describe heavy impurity neoclassical transport in the presence of poloidal asymmetries in specific collisional regimes [C. Angioni and P. Helander, Plasma Phys. Controlled Fusion 56, 124001 (2014)] is compared in this work to numerical results from NEO. Within the domain of validity of the formula, the factor for reducing the temperature screening due to poloidal asymmetries had to be empirically adjusted. After adjustment, the modified formula can reproduce NEO results outside of its definition domain, with some limitations: When main ions are in the banana regime, the formula reproduces NEO results whatever the collisionality regime of impurities, provided that the poloidal asymmetry is not too large. However, for very strong poloidal asymmetries, agreement requires impurities in the Pfirsch-Schlüter regime. Within the JETTO integrated transport code, the analytical formula combined with the poloidally symmetric neoclassical code NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] predicts the same tungsten profile as NEO in certain cases, while saving a factor of one thousand in computer time, which can be useful in scoping studies. The parametric dependencies of the temperature screening reduction due to poloidal asymmetries would need to be better characterised for this faster model to be extended to a more general applicability.

VL - 25 IS - 1 U1 -FP

U2 -IMT

U5 - 4124380d82634de2c37d95ae7f073ef4 ER - TY - JOUR T1 - Impact of ideal MHD stability limits on high-beta hybrid operation JF - Plasma Physics and Controlled Fusion Y1 - 2017 A1 - Piovesan, P. A1 - Igochine, V. A1 - Turco, F. A1 - Ryan, D. A. A1 - Cianciosa, M. R. A1 - Liu, Y. Q. A1 - Marrelli, L. A1 - Terranova, D. A1 - Wilcox, R. S. A1 - Wingen, A. A1 - Angioni, C. A1 - Bock, A. A1 - Chrystal, C. A1 - Classen, I. A1 - Dunne, M. A1 - Ferraro, N. M. A1 - Fischer, R. A1 - Gude, A. A1 - Holcomb, C. T. A1 - Lebschy, A. A1 - Luce, T. C. A1 - Maraschek, M. A1 - McDermott, R. A1 - Odstrcil, T. A1 - Paz-Soldan, C. A1 - Reich, M. A1 - Sertoli, M. A1 - Suttrop, W. A1 - Taylor, N. Z. A1 - Weiland, M. A1 - Willensdorfer, M. A1 - ASDEX Upgrade Team A1 - DIII-D Team A1 - EUROfusion MST1 Team VL - 59 UR - http://www.euro-fusionscipub.org/wp-content/uploads/WPMST1CP16_15388_submitted.pdf IS - 1 U1 -FP

U2 -PEPD

U3 - FP120 U5 - 9459e9933ae840264ddb8f8a49bbc0dd ER - TY - JOUR T1 - Tractable flux-driven temperature, density, and rotation profile evolution with the quasilinear gyrokinetic transport model QuaLiKiz JF - Plasma Physics and Controlled Fusion Y1 - 2017 A1 - Citrin, J. A1 - Bourdelle, C. A1 - Casson, F. J. A1 - Angioni, C. A1 - Bonanomi, N. A1 - Camenen, Y. A1 - Garbet, X. A1 - Garzotti, L. A1 - Gorler, T. A1 - Gurcan, O. D. A1 - Koechl, F. A1 - Imbeaux, F. A1 - Linder, O. A1 - van de Plassche, K. A1 - Strand, P. A1 - Szepesi, G. A1 - JET Contributors AB - Quasilinear turbulent transport models are a successful tool for prediction of core tokamak plasma profiles in many regimes. Their success hinges on the reproduction of local nonlinear gyrokinetic fluxes. We focus on significant progress in the quasilinear gyrokinetic transport model QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036), which employs an approximated solution of the mode structures to significantly speed up computation time compared to full linear gyrokinetic solvers. Optimisation of the dispersion relation solution algorithm within integrated modelling applications leads to flux calculations x10 6-7 faster than local nonlinear simulations. This allows tractable simulation of flux-driven dynamic profile evolution including all transport channels: ion and electron heat, main particles, impurities, and momentum. Furthermore, QuaLiKiz now includes the impact of rotation and temperature anisotropy induced poloidal asymmetry on heavy impurity transport, important for W-transport applications. Application within the JETTO integrated modelling code results in 1 s of JET plasma simulation within 10 h using 10 CPUs. Simultaneous predictions of core density, temperature, and toroidal rotation profiles for both JET hybrid and baseline experiments are presented, covering both ion and electron turbulence scales. The simulations are successfully compared to measured profiles, with agreement mostly in the 5%–25% range according to standard figures of merit. QuaLiKiz is now open source and available at www.qualikiz.com. VL - 59 UR - https://arxiv.org/abs/1708.01224 IS - 12 U1 - FP U2 - IMT U5 - 5234d3fadaa3c4d0ad98a555a43c362c ER - TY - JOUR T1 - Optimization of ICRH for core impurity control in JET-ILW JF - Nuclear Fusion Y1 - 2016 A1 - Lerche, E. A1 - Goniche, M. A1 - Jacquet, P. A1 - Van Eester, D. A1 - Bobkov, V. A1 - Colas, L. A1 - Giroud, C. A1 - Monakhov, I. A1 - Casson, F. J. A1 - Tsalas, M. A1 - Rimini, F. A1 - Angioni, C. A1 - Baruzzo, M. A1 - Blackman, T. A1 - Brezinsek, S. A1 - Brix, M. A1 - Czarnecka, A. A1 - Crombe, K. A1 - Challis, C. A1 - Dumont, R. A1 - Eriksson, J. A1 - Fedorczak, N. A1 - Graham, M. A1 - Graves, J. P. A1 - Gorini, G. A1 - Hobirk, J. A1 - Joffrin, E. A1 - Johnson, T. A1 - Kazakov, Y. A1 - Kiptily, V. A1 - Krivska, A. A1 - Lennholm, M. A1 - Lomas, P. A1 - Maggi, C. A1 - Mantica, P. A1 - Mathews, G. A1 - Mayoral, M. A1 - Meneses, L. A1 - Mlynar, J. A1 - Monier-Garbet, P. A1 - Nave, M. F. A1 - Noble, C. A1 - Nocente, M. A1 - Nunes, I. A1 - Ongena, J. A1 - Petravich, G. A1 - Petrzilka, V. A1 - Putterich, T. A1 - Reich, M. A1 - Santala, M. A1 - Solano, E. R. A1 - Shaw, A. A1 - Sips, G. A1 - Stamp, M. A1 - Tardocchi, M. A1 - Valisa, M. A1 - JET Contributors AB -Ion cyclotron resonance frequency (ICRF) heating has been an essential component in the development of high power H-mode scenarios in the Jet European Torus ITER-like wall (JET-ILW). The ICRF performance was improved by enhancing the antenna-plasma coupling with dedicated main chamber gas injection, including the preliminary minimization of RF-induced plasma-wall interactions, while the RF heating scenarios where optimized for core impurity screening in terms of the ion cyclotron resonance position and the minority hydrogen concentration. The impact of ICRF heating on core impurity content in a variety of 2.5 MA JET-ILW H-mode plasmas will be presented, and the steps that were taken for optimizing ICRF heating in these experiments will be reviewed.

VL - 56 UR - http://www.euro-fusionscipub.org/wp-content/uploads/2015/09/WPJET1PR1528.pdf IS - 3 U1 -FP

U2 -TP

U5 - d602ccdf3e42dd82b551d41759691058 ER - TY - JOUR T1 - Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall JF - Plasma Physics and Controlled Fusion Y1 - 2015 A1 - Giroud, C. A1 - Jachmich, S. A1 - Jacquet, P. A1 - Jarvinen, A. A1 - Lerche, E. A1 - Rimini, F. A1 - Aho-Mantila, L. A1 - Aiba, N. A1 - Balboa, I. A1 - da Silva Aresta Belo, P. A1 - Angioni, C. A1 - Beurskens, M. A1 - Brezinsek, S. A1 - Casson, F. J. A1 - Coffey, I. A1 - Cunningham, G. A1 - Delabie, E. A1 - Devaux, S. A1 - Drewelow, P. A1 - Frassinetti, L. A1 - Figueiredo, A. A1 - Huber, A. A1 - Hillesheim, J. A1 - Garzotti, L. A1 - Goniche, M. A1 - Groth, M. A1 - Hyun-Tae Kim A1 - Leyland, M. A1 - Lomas, P. A1 - Maddison, G. A1 - Marsen, S. A1 - Matthews, G. A1 - Meigs, A. A1 - Menmuir, S. A1 - Putterich, T. A1 - G. van Rooij A1 - Saarelma, S. A1 - Stamp, M. A1 - Urano, H. A1 - Webster, A. A1 - JET-EFDA Contributors AB - This paper reports the progress made at JET-ILW on integrating the requirements of the reference ITER baseline scenario with normalized confinement factor of 1, at a normalized pressure of 1.8 together with partially detached divertor whilst maintaining these conditions over many energy confinement times. The 2.5 MA high triangularity ELMy H-modes are studied with two different divertor configurations with D-gas injection and nitrogen seeding. The power load reduction with N seeding is reported. The relationship between an increase in energy confinement and pedestal pressure with triangularity is investigated. The operational space of both plasma configurations is studied together with the ELM energy losses and stability of the pedestal of unseeded and seeded plasmas. The achievement of stationary plasma conditions over many energy confinement times is also reported. VL - 57 UR - http://www.iop.org/Jet/fulltext/EFDP14021.pdf IS - 3 U1 - FP U2 - PDG U5 - 4b7265a10a94f029cf4f14cd047251e2 ER - TY - JOUR T1 - Impact of W on scenario simulations for ITER JF - Nuclear Fusion Y1 - 2015 A1 - Hogeweij, G. M. D. A1 - Leonov, V. A1 - Schweinzer, J. A1 - Sips, A.C.C. A1 - Angioni, C. A1 - Calabro, G. A1 - Dux, R. A1 - Kallenbach, A. A1 - Lerche, E. A1 - Maggi, C. A1 - Putterich, T. A1 - ITPA Integrated Operating Scenarios topical group A1 - ASDEX Upgrade Team A1 - JET Contributors AB - In preparation of ITER operation, large machines have replaced their wall and divertor material to W (ASDEX Upgrade) or a combination of Be for the wall and W for the divertor (JET). Operation in these machines has shown that the influx of W can have a significant impact on the discharge evolution, which has made modelling of this impact for ITER an urgent task. This paper reports on such modelling efforts. Maximum tolerable W concentrations have been determined for various scenarios, both for the current ramp-up and flat-top phase. Results of two independent methods are presented, based on the codes ZIMPUR plus ASTRA and CRONOS, respectively. Both methods have been tested and benchmarked against ITER-like I p RU experiments at JET. It is found that W significantly disturbs the discharge evolution when the W concentration approaches ∼10 −4 ; this critical level varies somewhat between scenarios. VL - 55 IS - 6 U1 - FP U2 - CPP-HT U5 - d8553e78fee23a346493abe41c17a811 ER - TY - JOUR T1 - Global and pedestal confinement in JET with a Be/W metallic wall JF - Nuclear Fusion Y1 - 2014 A1 - Beurskens, M. N. A. A1 - Frassinetti, L. A1 - Challis, C. A1 - Giroud, C. A1 - Saarelma, S. A1 - Alper, B. A1 - Angioni, C. A1 - P. Bilkova A1 - Bourdelle, C. A1 - Brezinsek, S. A1 - Buratti, P. A1 - Calabro, G. A1 - Eich, T. A1 - Flanagan, J. A1 - Giovannozzi, E. A1 - Groth, M. A1 - Hobirk, J. A1 - Joffrin, E. A1 - Leyland, M. J. A1 - Lomas, P. A1 - de la Luna, E. A1 - Kempenaars, M. A1 - Maddison, G. A1 - Maggi, C. A1 - Mantica, P. A1 - Maslov, M. A1 - Matthews, G. A1 - M-L Mayoral A1 - Neu, R. A1 - Nunes, I. A1 - Osborne, T. A1 - Rimini, F. A1 - Scannell, R. A1 - Solano, E. R. A1 - Snyder, P. B. A1 - Voitsekhovitch, I. A1 - de Vries, P. C. A1 - JET-EFDA Contributors AB - Type I ELMy H-mode operation in JET with the ITER-like Be/W wall (JET-ILW) generally occurs at lower pedestal pressures compared to those with the full carbon wall (JET-C). The pedestal density is similar but the pedestal temperature where type I ELMs occur is reduced and below to the so-called critical type I-type III transition temperature reported in JET-C experiments. Furthermore, the confinement factor H 98( y ,2) in type I ELMy H-mode baseline plasmas is generally lower in JET-ILW compared to JET-C at low power fractions P loss / P thr,08 < 2 (where P loss is ( P in − d W /d t ), and P thr,08 the LH power threshold from Martin et al 2008 ( J. Phys. Conf. Ser. 123 [http://dx.doi.org/10.1088/1742-6596/123/1/012033] 012033 )). Higher power fractions have thus far not been achieved in the baseline plasmas. At P loss / P thr,08 > 2, the confinement in JET-ILW hybrid plasmas is similar to that in JET-C. A reduction in pedestal pressure is the main reason for the reduced confinement in JET-ILW baseline ELMy H-mode plasmas where typically H 98( y ,2) = 0.8 is obtained, compared to H 98( y ,2) = 1.0 in JET-C. In JET-ILW hybrid plasmas a similarly reduced pedestal pressure is compensated by an increased peaking of the core pressure profile resulting in H 98( y ,2) ⩽ 1.25. The pedestal stability has significantly changed in high triangularity baseline plasmas where the confinement loss is also most apparent. Applying the same stability analysis for JET-C and JET-ILW, the measured pedestal in JET-ILW is stable with respect to the calculated peeling ballooning stability limit and the ELM collapse time has increased to 2 ms from typically 200 µ s in JET-C. This indicates that changes in the pedestal stability may have contributed to the reduced pedestal confinement in JET-ILW plasmas. A comparison of EPED1 pedestal pressure prediction with JET-ILW experimental data in over 500 JET-C and JET-ILW baseline and hybrid plasmas shows a good agreement with 0.8 < (measured p ped )/(predicted p ped,EPED ) < 1.2, but that the role of triangularity is generally weaker in the JET-ILW experimental data than in the model predictions. VL - 54 UR - http://www.iop.org/Jet/article?EFDP12051&EFDP12058 IS - 4 U1 - FP U2 - PDG U5 - 0db46cb7db189d845dec2f404c29ef68 ER - TY - JOUR T1 - Comparison of hybrid and baseline ELMy H-mode confinement in JET with the carbon wall JF - Nuclear Fusion Y1 - 2013 A1 - Beurskens, M. N. A. A1 - Frassinetti, L. A1 - Challis, C. A1 - Osborne, T. A1 - Snyder, P. B. A1 - Alper, B. A1 - Angioni, C. A1 - Bourdelle, C. A1 - Buratti, P. A1 - Crisanti, F. A1 - Giovannozzi, E. A1 - Giroud, C. A1 - Groebner, R. A1 - Hobirk, J. A1 - Jenkins, I. A1 - Joffrin, E. A1 - Leyland, M. J. A1 - Lomas, P. A1 - Mantica, P. A1 - McDonald, D. A1 - Nunes, I. A1 - Rimini, F. A1 - Saarelma, S. A1 - Voitsekhovitch, I. A1 - P. de Vries A1 - Zarzoso, D. AB -The confinement in JET baseline type I ELMy H-mode plasmas is compared to that in so-called hybrid H-modes in a database study of 112 plasmas in JET with the carbon fibre composite (CFC) wall. The baseline plasmas typically have beta(Nu) similar to 1.5-2, H-98 similar to 1, whereas the hybrid plasmas have beta(Nu) similar to 2.5-3, H98 < 1.5. The database study contains both low-( delta similar to 0.2-0.25) and high-triangularity ( delta similar to 0.4) hybrid and baseline H-mode plasmas from the last JET operational campaigns in the CFC wall from the period 2008-2009. Based on a detailed confinement study of the global as well as the pedestal and core confinement, there is no evidence that the hybrid and baseline plasmas form separate confinement groups; it emerges that the transition between the two scenarios is of a gradual kind rather than demonstrating a bifurcation in the confinement. The elevated confinement enhancement factor H98 in the hybrid plasmas may possibly be explained by the density dependence in the tau(98) scaling as n(0.41) and the fact that the hybrid plasmas operate at low plasma density compared to the baseline ELMy H-mode plasmas. A separate regression on the confinement data in this study shows a reduction in the density dependence as n(0.09 +/- 0.08). Furthermore, inclusion of the plasma toroidal rotation in the confinement regression provides a scaling with the toroidal Alfven Mach number as Mach(A)(0.41 +/- 0.07) A and again a reduced density dependence as n(0.15 +/- 0.08). The differences in pedestal confinement can be explained on the basis of linear MHD stability through a coupling of the total and pedestal poloidal pressure and the pedestal performance can be improved through plasma shaping as well as high beta operation. This has been confirmed in a comparison with the EPED1 predictive pedestal code which shows a good agreement between the predicted and measured pedestal pressure within 20-30% for a wide range of beta(Nu) similar to 1.5-3.5. The core profiles show a strong degree of pressure profile consistency. No beneficial effect of core density peaking on confinement could be identified for the majority of the plasmas presented here as the density peaking is compensated by a temperature de-peaking resulting in no or only a weak variation in the pressure peaking. The core confinement could only be optimized in case the ions and electrons are decoupled, in which case the ion temperature profile peaking can be enhanced, which benefits confinement. In this study, the latter has only been achieved in the low-triangularity hybrid plasmas, and can be attributed to low-density operation. Plasma rotation has been found to reduce core profile stiffness, and can explain an increase in profile peaking at small radius rho(tor) = 0.3.

VL - 53 SN - 0029-5515 UR - http://www.euro-fusionscipub.org/wp-content/uploads/2014/11/EFDP12003.pdf U1 -FP

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U5 - 92924cd2ff4a241d14d8e4954dd8cea5 ER - TY - JOUR T1 - Overview of ASDEX Upgrade results JF - Nuclear Fusion Y1 - 2013 A1 - Stroth, U. A1 - Adamek, J. A1 - Aho-Mantila, L. A1 - Akaslompolo, S. A1 - Amdor, C. A1 - Angioni, C. A1 - Balden, M. A1 - Bardin, S. A1 - L. Barrera Orte A1 - Behler, K. A1 - Belonohy, E. A1 - Bergmann, A. A1 - Bernert, M. A1 - Bilato, R. A1 - Birkenmeier, G. A1 - Bobkov, V. A1 - Boom, J. A1 - Bottereau, C. A1 - Bottino, A. A1 - Braun, F. A1 - Brezinsek, S. A1 - Brochard, T. A1 - M. Brüdgam A1 - Buhler, A. A1 - Burckhart, A. A1 - Casson, F. J. A1 - Chankin, A. A1 - Chapman, I. A1 - Clairet, F. A1 - Classen, I.G.J. A1 - Coenen, J. W. A1 - Conway, G. D. A1 - Coster, D. P. A1 - Curran, D. A1 - da Silva, F. A1 - P. de Marné A1 - D'Inca, R. A1 - Douai, D. A1 - Drube, R. A1 - Dunne, M. A1 - Dux, R. A1 - Eich, T. A1 - Eixenberger, H. A1 - Endstrasser, N. A1 - Engelhardt, K. A1 - Esposito, B. A1 - Fable, E. A1 - Fischer, R. A1 - H. Fünfgelder A1 - Fuchs, J. C. A1 - K. Gál A1 - M. García Muñoz A1 - Geiger, B. A1 - Giannone, L. A1 - T. Görler A1 - da Graca, S. A1 - Greuner, H. A1 - Gruber, O. A1 - Gude, A. A1 - Guimarais, L. A1 - S. Günter A1 - Haas, G. A1 - Hakola, A. H. A1 - Hangan, D. A1 - Happel, T. A1 - T. Härtl A1 - Hauff, T. A1 - Heinemann, B. A1 - Herrmann, A. A1 - Hobirk, J. A1 - H. Höhnle A1 - M. Hölzl A1 - Hopf, C. A1 - Houben, A. A1 - Igochine, V. A1 - Ionita, C. A1 - Janzer, A. A1 - Jenko, F. A1 - Kantor, M. A1 - C.-P. Käsemann A1 - Kallenbach, A. A1 - S. Kálvin A1 - Kantor, M. A1 - Kappatou, A. A1 - Kardaun, O. A1 - Kasparek, W. A1 - Kaufmann, M. A1 - Kirk, A. A1 - H.-J. Klingshirn A1 - Kocan, M. A1 - Kocsis, G. A1 - Konz, C. A1 - Koslowski, R. A1 - Krieger, K. A1 - Kubic, M. A1 - Kurki-Suonio, T. A1 - Kurzan, B. A1 - Lackner, K. A1 - Lang, P. T. A1 - Lauber, P. A1 - Laux, M. A1 - Lazaros, A. A1 - Leipold, F. A1 - Leuterer, F. A1 - Lindig, S. A1 - Lisgo, S. A1 - Lohs, A. A1 - Lunt, T. A1 - Maier, H. A1 - Makkonen, T. A1 - Mank, K. A1 - M.-E. Manso A1 - Maraschek, M. A1 - Mayer, M. A1 - McCarthy, P. J. A1 - McDermott, R. A1 - Mehlmann, F. A1 - Meister, H. A1 - Menchero, L. A1 - Meo, F. A1 - Merkel, P. A1 - Merkel, R. A1 - Mertens, V. A1 - Merz, F. A1 - Mlynek, A. A1 - Monaco, F. A1 - Müller, S. A1 - H.W. Müller A1 - M. Münich A1 - Neu, G. A1 - Neu, R. A1 - Neuwirth, D. A1 - Nocente, M. A1 - Nold, B. A1 - Noterdaeme, J. M. A1 - Pautasso, G. A1 - Pereverzev, G. A1 - B. Plöckl A1 - Podoba, Y. A1 - Pompon, F. A1 - Poli, E. A1 - Polozhiy, K. A1 - Potzel, S. A1 - M. J. Pueschel A1 - Putterich, T. A1 - Rathgeber, S. K. A1 - Raupp, G. A1 - Reich, M. A1 - Reimold, F. A1 - Ribeiro, T. A1 - Riedl, R. A1 - Rohde, V. A1 - G. J. van Rooij A1 - Roth, J. A1 - Rott, M. A1 - Ryter, F. A1 - Salewski, M. A1 - Santos, J. A1 - Sauter, P. A1 - Scarabosio, A. A1 - Schall, G. A1 - Schmid, K. A1 - Schneider, P. A. A1 - Schneider, W. A1 - Schrittwieser, R. A1 - Schubert, M. A1 - Schweinzer, J. A1 - Scott, B. A1 - Sempf, M. A1 - Sertoli, M. A1 - Siccinio, M. A1 - Sieglin, B. A1 - Sigalov, A. A1 - Silva, A. A1 - Sommer, F. A1 - A. Stäbler A1 - Stober, J. A1 - Streibl, B. A1 - Strumberger, E. A1 - Sugiyama, K. A1 - Suttrop, W. A1 - Tala, T. A1 - Tardini, G. A1 - Teschke, M. A1 - Tichmann, C. A1 - Told, D. A1 - Treutterer, W. A1 - Tsalas, M. A1 - VanZeeland, M. A. A1 - Varela, P. A1 - Veres, G. A1 - Vicente, J. A1 - Vianello, N. A1 - Vierle, T. A1 - Viezzer, E. A1 - Viola, B. A1 - Vorpahl, C. A1 - Wachowski, M. A1 - Wagner, D. A1 - Wauters, T. A1 - Weller, A. A1 - Wenninger, R. A1 - Wieland, B. A1 - Willensdorfer, M. A1 - Wischmeier, M. A1 - Wolfrum, E. A1 - E. Würsching A1 - Yu, Q. A1 - Zammuto, I. A1 - Zasche, D. A1 - Zehetbauer, T. A1 - Zhang, Y. A1 - Zilker, M. A1 - Zohm, H. AB - The medium size divertor tokamak ASDEX Upgrade (major and minor radii 1.65 m and 0.5 m, respectively, magnetic-field strength 2.5 T) possesses flexible shaping and versatile heating and current drive systems. Recently the technical capabilities were extended by increasing the electron cyclotron resonance heating (ECRH) power, by installing 2 × 8 internal magnetic perturbation coils, and by improving the ion cyclotron range of frequency compatibility with the tungsten wall. With the perturbation coils, reliable suppression of large type-I edge localized modes (ELMs) could be demonstrated in a wide operational window, which opens up above a critical plasma pedestal density. The pellet fuelling efficiency was observed to increase which gives access to H-mode discharges with peaked density profiles at line densities clearly exceeding the empirical Greenwald limit. Owing to the increased ECRH power of 4 MW, H-mode discharges could be studied in regimes with dominant electron heating and low plasma rotation velocities, i.e. under conditions particularly relevant for ITER. The ion-pressure gradient and the neoclassical radial electric field emerge as key parameters for the transition. Using the total simultaneously available heating power of 23 MW, high performance discharges have been carried out where feed-back controlled radiative cooling in the core and the divertor allowed the divertor peak power loads to be maintained below 5 MW m −2 . Under attached divertor conditions, a multi-device scaling expression for the power-decay length was obtained which is independent of major radius and decreases with magnetic field resulting in a decay length of 1 mm for ITER. At higher densities and under partially detached conditions, however, a broadening of the decay length is observed. In discharges with density ramps up to the density limit, the divertor plasma shows a complex behaviour with a localized high-density region in the inner divertor before the outer divertor detaches. Turbulent transport is studied in the core and the scrape-off layer (SOL). Discharges over a wide parameter range exhibit a close link between core momentum and density transport. Consistent with gyro-kinetic calculations, the density gradient at half plasma radius determines the momentum transport through residual stress and thus the central toroidal rotation. In the SOL a close comparison of probe data with a gyro-fluid code showed excellent agreement and points to the dominance of drift waves. Intermittent structures from ELMs and from turbulence are shown to have high ion temperatures even at large distances outside the separatrix. VL - 53 UR - http://hdl.handle.net/11858/00-001M-0000-0026-E166-7 IS - 10 U1 - FP U2 - PDG U5 - 0b5b08fdc590c85cc01e6d1db1958848 ER - TY - JOUR T1 - A Key to Improved Ion Core Confinement in the JET Tokamak: Ion Stiffness Mitigation due to Combined Plasma Rotation and Low Magnetic Shear JF - Physical Review Letters Y1 - 2011 A1 - Mantica, P. A1 - Angioni, C. A1 - Challis, C. A1 - Colyer, G. A1 - Frassinetti, L. A1 - Hawkes, N. A1 - Johnson, T. A1 - Tsalas, M. A1 - de Vries, P. C. A1 - Weiland, J. A1 - Baiocchi, B. A1 - Beurskens, M. N. A. A1 - Figueiredo, A. C. A. A1 - Giroud, C. A1 - Hobirk, J. A1 - Joffrin, E. A1 - Lerche, E. A1 - Naulin, V. A1 - Peeters, A.G. A1 - Salmi, A. A1 - Sozzi, C. A1 - Strintzi, D. A1 - Staebler, G. A1 - Tala, T. A1 - Van Eester, D. A1 - Versloot, T. KW - MODES KW - THERMAL TRANSPORT KW - TRANSPORT BARRIERS KW - TURBULENCE SIMULATIONS AB -New transport experiments on JET indicate that ion stiffness mitigation in the core of a rotating plasma, as described by Mantica et al. [Phys. Rev. Lett. 102, 175002 (2009)] results from the combined effect of high rotational shear and low magnetic shear. The observations have important implications for the understanding of improved ion core confinement in advanced tokamak scenarios. Simulations using quasilinear fluid and gyrofluid models show features of stiffness mitigation, while nonlinear gyrokinetic simulations do not. The JET experiments indicate that advanced tokamak scenarios in future devices will require sufficient rotational shear and the capability of q profile manipulation.

VL - 107 SN - 0031-9007 UR - http://purl.tue.nl/11399973048620600.pdf IS - 13 N1 - ISI Document Delivery No.: 823QCTimes Cited: 0Cited Reference Count: 39 U1 -FP

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U5 - e071481b46251293c570437edddbc5ab ER - TY - JOUR T1 - Overview of ASDEX Upgrade results JF - Nuclear Fusion Y1 - 2011 A1 - Kallenbach, A. A1 - Adamek, J. A1 - Aho-Mantila, L. A1 - Akaslompolo, S. A1 - Angioni, C. A1 - Atanasiu, C. V. A1 - Balden, M. A1 - Behler, K. A1 - Belonohy, E. A1 - Bergmann, A. A1 - Bernert, M. A1 - Bilato, R. A1 - Bobkov, V. A1 - Boom, J. A1 - Bottino, A. A1 - Braun, F. A1 - Brudgam, M. A1 - Buhler, A. A1 - Burckhart, A. A1 - Chankin, A. A1 - Classen, I.G.J. A1 - Conway, G. D. A1 - Coster, D. P. A1 - de Marne, P. A1 - D'Inca, R. A1 - Drube, R. A1 - Dux, R. A1 - Eich, T. A1 - Endstrasser, N. A1 - Engelhardt, K. A1 - Esposito, B. A1 - Fable, E. A1 - Fahrbach, H. U. A1 - Fattorini, L. A1 - Fischer, R. A1 - Flaws, A. A1 - Funfgelder, H. A1 - Fuchs, J. C. A1 - Gal, K. A1 - Munoz, M. G. A1 - Geiger, B. A1 - Adamov, M. G. A1 - Giannone, L. A1 - Giroud, C. A1 - Gorler, T. A1 - da Graca, S. A1 - Greuner, H. A1 - Gruber, O. A1 - Gude, A. A1 - Gunter, S. A1 - Haas, G. A1 - Hakola, A. H. A1 - Hangan, D. A1 - Happel, T. A1 - Hauff, T. A1 - Heinemann, B. A1 - Herrmann, A. A1 - Hicks, N. A1 - Hobirk, J. A1 - Hohnle, H. A1 - Holzl, M. A1 - Hopf, C. A1 - Horton, L. A1 - Huart, M. A1 - Igochine, V. A1 - Ionita, C. A1 - Janzer, A. A1 - Jenko, F. A1 - Kasemann, C. P. A1 - Kalvin, S. A1 - Kardaun, O. A1 - Kaufmann, M. A1 - Kirk, A. A1 - Klingshirn, H. J. A1 - Kocan, M. A1 - Kocsis, G. A1 - Kollotzek, H. A1 - Konz, C. A1 - Koslowski, R. A1 - Krieger, K. A1 - Kurki-Suonio, T. A1 - Kurzan, B. A1 - Lackner, K. A1 - Lang, P. T. A1 - Lauber, P. A1 - Laux, M. A1 - Leipold, F. A1 - Leuterer, F. A1 - Lohs, A. A1 - N C Luhmann Jr. A1 - Lunt, T. A1 - Lyssoivan, A. A1 - Maier, H. A1 - Maggi, C. A1 - Mank, K. A1 - Manso, M. E. A1 - Maraschek, M. A1 - Martin, P. A1 - Mayer, M. A1 - McCarthy, P. J. A1 - McDermott, R. A1 - Meister, H. A1 - Menchero, L. A1 - Meo, F. A1 - Merkel, P. A1 - Merkel, R. A1 - Mertens, V. A1 - Merz, F. A1 - Mlynek, A. A1 - Monaco, F. A1 - Muller, H. W. A1 - Munich, M. A1 - Murmann, H. A1 - Neu, G. A1 - Neu, R. A1 - Nold, B. A1 - Noterdaeme, J. M. A1 - Park, H. K. A1 - Pautasso, G. A1 - Pereverzev, G. A1 - Podoba, Y. A1 - Pompon, F. A1 - Poli, E. A1 - Polochiy, K. A1 - Potzel, S. A1 - Prechtl, M. A1 - M. J. Pueschel A1 - Putterich, T. A1 - Rathgeber, S. K. A1 - Raupp, G. A1 - Reich, M. A1 - Reiter, B. A1 - Ribeiro, T. A1 - Riedl, R. A1 - Rohde, V. A1 - Roth, J. A1 - Rott, M. A1 - Ryter, F. A1 - Sandmann, W. A1 - Santos, J. A1 - Sassenberg, K. A1 - Sauter, P. A1 - Scarabosio, A. A1 - Schall, G. A1 - Schmid, K. A1 - Schneider, P. A. A1 - Schneider, W. A1 - Schramm, G. A1 - Schrittwieser, R. A1 - Schweinzer, J. A1 - Scott, B. A1 - Sempf, M. A1 - Serra, F. A1 - Sertoli, M. A1 - Siccinio, M. A1 - Sigalov, A. A1 - Silva, A. A1 - Sips, A.C.C. A1 - Sommer, F. A1 - Stabler, A. A1 - Stober, J. A1 - Streibl, B. A1 - Strumberger, E. A1 - Sugiyama, K. A1 - Suttrop, W. A1 - Szepesi, T. A1 - Tardini, G. A1 - Tichmann, C. A1 - Told, D. A1 - Treutterer, W. A1 - Urso, L. A1 - Varela, P. A1 - Vincente, J. A1 - Vianello, N. A1 - Vierle, T. A1 - Viezzer, E. A1 - Vorpahl, C. A1 - Wagner, D. A1 - Weller, A. A1 - Wenninger, R. A1 - Wieland, B. A1 - Wigger, C. A1 - Willensdorfer, M. A1 - Wischmeier, M. A1 - Wolfrum, E. A1 - Wursching, E. A1 - Yadikin, D. A1 - Yu, Q. A1 - Zammuto, I. A1 - Zasche, D. A1 - Zehetbauer, T. A1 - Zhang, Y. A1 - Zilker, M. A1 - Zohm, H. KW - PHYSICS KW - REFLECTOMETRY KW - TOKAMAK AB - The ASDEX Upgrade programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. After the finalization of the tungsten coating of the plasma facing components, the re-availability of all flywheel-generators allowed high-power operation with up to 20 MW heating power at I(p) up to 1.2 MA. Implementation of alternative ECRH schemes (140 GHz O2- and X3-mode) facilitated central heating above n(e) = 1.2 x 10(20) m(-3) and low q(95) operation at B(t) = 1.8 T. Central O2-mode heating was successfully used in high P/R discharges with 20 MW total heating power and divertor load control with nitrogen seeding. Improved energy confinement is obtained with nitrogen seeding both for type-I and type-III ELMy conditions. The main contributor is increased plasma temperature, no significant changes in the density profile have been observed. This behaviour may be explained by higher pedestal temperatures caused by ion dilution in combination with a pressure limited pedestal and hollow nitrogen profiles. Core particle transport simulations with gyrokinetic calculations have been benchmarked by dedicated discharges using variations of the ECRH deposition location. The reaction of normalized electron density gradients to variations of temperature gradients and the T(e)/T(i) ratio could be well reproduced. Doppler reflectometry studies at the L-H transition allowed the disentanglement of the interplay between the oscillatory geodesic acoustic modes, turbulent fluctuations and the mean equilibrium E x B flow in the edge negative E(r) well region just inside the separatrix. Improved pedestal diagnostics revealed also a refined picture of the pedestal transport in the fully developed H-mode type-I ELM cycle. Impurity ion transport turned out to be neoclassical in between ELMs. Electron and energy transport remain anomalous, but exhibit different recovery time scales after an ELM. After recovery of the pre-ELM profiles, strong fluctuations develop in the gradients of n(e) and T(e). The occurrence of the next ELM cannot be explained by the local current diffusion time scale, since this turns out to be too short. Fast ion losses induced by shear Alfven eigenmodes have been investigated by time-resolved energy and pitch angle measurements. This allowed the separation of the convective and diffusive loss mechanisms. VL - 51 SN - 0029-5515 IS - 9 N1 - ISI Document Delivery No.: 818DPTimes Cited: 1Cited Reference Count: 45SI U1 - FP U2 - PDG U5 - a193177a90d5b600862ca1e40bcc67af ER - TY - JOUR T1 - Overview of toroidal momentum transport JF - Nuclear Fusion Y1 - 2011 A1 - Peeters, A.G. A1 - Angioni, C. A1 - Bortolon, A. A1 - Camenen, Y. A1 - Casson, F. J. A1 - Duval, B. A1 - Fiederspiel, L. A1 - Hornsby, W. A. A1 - Idomura, Y. A1 - Hein, T. A1 - Kluy, N. A1 - Mantica, P. A1 - Parra, F. I. A1 - Snodin, A. P. A1 - Szepesi, G. A1 - Strintzi, D. A1 - Tala, T. A1 - Tardini, G. A1 - P. de Vries A1 - Weiland, J. KW - ALCATOR-C-MOD KW - ANGULAR-MOMENTUM KW - CYCLOTRON WAVE KW - FLOWS KW - INJECTION KW - ION TEMPERATURE KW - NEUTRAL-BEAM INJECTION KW - OFF-LAYER KW - OHMIC H-MODE KW - PLASMA ROTATION KW - RADIAL ELECTRIC-FIELD KW - TEMPERATURE-GRADIENT MODE AB -Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related to the breaking of symmetry (parity) along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E x B shearing, particle flux, and up-down asymmetric equilibria) are reasonably well understood. At higher order, expected to be of importance in the plasma edge, the theory is still under development.

VL - 51 SN - 0029-5515 IS - 9 N1 - ISI Document Delivery No.: 818DPTimes Cited: 1Cited Reference Count: 114SI U1 -FP

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U5 - 2efb8b4ed885eb95aa643b3d2cfd6e6b ER - TY - JOUR T1 - Metal impurity transport control in JET H-mode plasmas with central ion cyclotron radiofrequency power injection JF - Nuclear Fusion Y1 - 2011 A1 - Valisa, M. A1 - Carraro, L. A1 - Predebon, I. A1 - M. E. Puiatti A1 - Angioni, C. A1 - Coffey, I. A1 - Giroud, C. A1 - Taroni, L. L. A1 - Alper, B. A1 - Baruzzo, M. A1 - da Silva, P. B. A1 - Buratti, P. A1 - Garzotti, L. A1 - Van Eester, D. A1 - Lerche, E. A1 - Mantica, P. A1 - Naulin, V. A1 - Tala, T. A1 - Tsalas, M. KW - ASDEX UPGRADE KW - BARRIER KW - BEHAVIOR KW - CONFINEMENT KW - DISCHARGES KW - divertor KW - FUSION DEVICES KW - NM REGION KW - TOKAMAK KW - Tungsten AB -The scan of ion cyclotron resonant heating (ICRH) power has been used to systematically study the pump out effect of central electron heating on impurities such as Ni and Mo in H-mode low collisionality discharges in JET. The transport parameters of Ni and Mo have been measured by introducing a transient perturbation on their densities via the laser blow off technique. Without ICRH Ni and Mo density profiles are typically peaked. The application of ICRH induces on Ni and Mo in the plasma centre (at normalized poloidal flux rho = 0.2) an outward drift approximately proportional to the amount of injected power. Above a threshold of ICRH power of about 3 MW in the specific case the radial flow of Ni and Mo changes from inwards to outwards and the impurity profiles, extrapolated to stationary conditions, become hollow. At mid-radius the impurity profiles become flat or only slightly hollow. In the plasma centre the variation of the convection-to-diffusivity ratio upsilon/D of Ni is particularly well correlated with the change in the ion temperature gradient in qualitative agreement with the neoclassical theory. However, the experimental radial velocity is larger than the neoclassical one by up to one order of magnitude. Gyrokinetic simulations of the radial impurity fluxes induced by electrostatic turbulence do not foresee a flow reversal in the analysed discharges.

VL - 51 SN - 0029-5515 IS - 3 N1 - ISI Document Delivery No.: 729AETimes Cited: 1Cited Reference Count: 34 U1 -FP

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U5 - dc8bc3592b534a570ec367324f31bd67 ER - TY - JOUR T1 - Core transport properties in JT-60U and JET identity plasmas JF - Nuclear Fusion Y1 - 2011 A1 - X. Litaudon A1 - Sakamoto, Y. A1 - de Vries, P. C. A1 - Salmi, A. A1 - Tala, T. A1 - Angioni, C. A1 - Benkadda, S. A1 - Beurskens, M. N. A. A1 - Bourdelle, C. A1 - Brix, M. A1 - Crombe, K. A1 - Fujita, T. A1 - Futatani, S. A1 - Garbet, X. A1 - Giroud, C. A1 - Hawkes, N. C. A1 - Hayashi, N. A1 - Hoang, G. T. A1 - Hogeweij, G. M. D. A1 - Matsunaga, G. A1 - Nakano, T. A1 - Oyama, N. A1 - Parail, V. A1 - Shinohara, K. A1 - Suzuki, T. A1 - Takechi, M. A1 - Takenaga, H. A1 - Takizuka, T. A1 - Urano, H. A1 - Voitsekhovitch, I. A1 - Yoshida, M. KW - BARRIERS KW - DENSITY PEAKING KW - NEOCLASSICAL TRANSPORT KW - TCV KW - TOKAMAK PLASMAS AB -The paper compares the transport properties of a set of dimensionless identity experiments performed between JET and JT-60U in the advanced tokamak regime with internal transport barrier, ITB. These International Tokamak Physics Activity, ITPA, joint experiments were carried out with the same plasma shape, toroidal magnetic field ripple and dimensionless profiles as close as possible during the ITB triggering phase in terms of safety factor, normalized Larmor radius, normalized collision frequency, thermal beta, ratio of ion to electron temperatures. Similarities in the ITB triggering mechanisms and sustainment were observed when a good match was achieved of the most relevant normalized profiles except the toroidal Mach number. Similar thermal ion transport levels in the two devices have been measured in either monotonic or non-monotonic q-profiles. In contrast, differences between JET and JT-60U were observed on the electron thermal and particle confinement in reversed magnetic shear configurations. It was found that the larger shear reversal in the very centre (inside normalized radius of 0.2) of JT-60U plasmas allowed the sustainment of stronger electron density ITBs compared with JET. As a consequence of peaked density profile, the core bootstrap current density is more than five times higher in JT-60U compared with JET. Thanks to the bootstrap effect and the slightly broader neutral beam deposition, reversed magnetic shear configurations are self-sustained in JT-60U scenarios. Analyses of similarities and differences between the two devices address key questions on the validity of the usual assumptions made in ITER steady scenario modelling, e. g. a flat density profile in the core with thermal transport barrier? Such assumptions have consequences on the prediction of fusion performance, bootstrap current and on the sustainment of the scenario.

VL - 51 SN - 0029-5515 IS - 7 N1 - ISI Document Delivery No.: 781LITimes Cited: 0Cited Reference Count: 31 U1 -FP

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U5 - 84b4980479d5b738ec4d26f9fd404727 ER - TY - JOUR T1 - Ion heat transport studies in JET JF - Plasma Physics and Controlled Fusion Y1 - 2011 A1 - Mantica, P. A1 - Angioni, C. A1 - Baiocchi, B. A1 - Baruzzo, M. A1 - Beurskens, M. N. A. A1 - Bizarro, J. P. S. A1 - Budny, R. V. A1 - Buratti, P. A1 - Casati, A. A1 - Challis, C. A1 - Citrin, J. A1 - Colyer, G. A1 - Crisanti, F. A1 - Figueiredo, A. C. A. A1 - Frassinetti, L. A1 - Giroud, C. A1 - Hawkes, N. A1 - Hobirk, J. A1 - Joffrin, E. A1 - Johnson, T. A1 - Lerche, E. A1 - Migliano, P. A1 - Naulin, V. A1 - Peeters, A.G. A1 - Rewoldt, G. A1 - Ryter, F. A1 - Salmi, A. A1 - Sartori, R. A1 - Sozzi, C. A1 - Staebler, G. A1 - Strintzi, D. A1 - Tala, T. A1 - Tsalas, M. A1 - Van Eester, D. A1 - Versloot, T. A1 - de Vries, P. C. A1 - Weiland, J. KW - ASDEX UPGRADE KW - CONFINEMENT KW - H-MODE PLASMAS KW - INSTABILITIES KW - RATIO KW - SHEAR KW - T-E/T-I KW - THERMAL TRANSPORT KW - TOKAMAKS KW - TURBULENCE SIMULATIONS AB -Detailed experimental studies of ion heat transport have been carried out in JET exploiting the upgrade of active charge exchange spectroscopy and the availability of multi-frequency ion cyclotron resonance heating with (3)He minority. The determination of ion temperature gradient (ITG) threshold and ion stiffness offers unique opportunities for validation of the well-established theory of ITG driven modes. Ion stiffness is observed to decrease strongly in the presence of toroidal rotation when the magnetic shear is sufficiently low. This effect is dominant with respect to the well-known omega(ExB) threshold up-shift and plays a major role in enhancing core confinement in hybrid regimes and ion internal transport barriers. The effects of T(e)/T(i) and s/q on ion threshold are found rather weak in the domain explored. Quasi-linear fluid/gyro-fluid and linear/non-linear gyro-kinetic simulations have been carried out. Whilst threshold predictions show good match with experimental observations, some significant discrepancies are found on the stiffness behaviour.

VL - 53 SN - 0741-3335 IS - 12 N1 - ISI Document Delivery No.: 870BLTimes Cited: 0Cited Reference Count: 58Part 1-2 U1 -FP

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U5 - 3e267c444cd4d79c851bd379feaeb938 ER - TY - JOUR T1 - Parametric dependences of momentum pinch and Prandtl number in JET JF - Nuclear Fusion Y1 - 2011 A1 - Tala, T. A1 - Salmi, A. A1 - Angioni, C. A1 - Casson, F. J. A1 - Corrigan, G. A1 - Ferreira, J. A1 - Giroud, C. A1 - Mantica, P. A1 - Naulin, V. A1 - Peeters, A.G. A1 - Solomon, W. M. A1 - Strintzi, D. A1 - Tsalas, M. A1 - Versloot, T. W. A1 - de Vries, P. C. A1 - Zastrow, K. D. KW - COLLISIONALITY KW - DENSITY PEAKING KW - H-MODES KW - PLASMAS KW - PROFILE KW - ROTATION KW - SHEAR KW - TOKAMAKS KW - TRANSPORT KW - TURBULENCE AB -Several parametric scans have been performed to study momentum transport on JET. A neutral beam injection modulation technique has been applied to separate the diffusive and convective momentum transport terms. The magnitude of the inward momentum pinch depends strongly on the inverse density gradient length, with an experimental scaling for the pinch number being - Rv(pinch)/chi(phi) = 1.2R/L(n) + 1.4. There is no dependence of the pinch number on collisionality, whereas the pinch seems to depend weakly on q-profile, the pinch number decreasing with increasing q. The Prandtl number was not found to depend either on R/L(n), collisionality or on q. The gyro-kinetic simulations show qualitatively similar dependence of the pinch number on R/L(n), but the dependence is weaker in the simulations. Gyro-kinetic simulations do not find any clear parametric dependence in the Prandtl number, in agreement with experiments, but the experimental values are larger than the simulated ones, in particular in L-mode plasmas. The extrapolation of these results to ITER illustrates that at large enough R/L(n) > 2 the pinch number becomes large enough (>3-4) to make the rotation profile peaked, provided that the edge rotation is non-zero. And this rotation peaking can be achieved with small or even with no core torque source. The absolute value of the core rotation is still very challenging to predict partly due to the lack of the present knowledge of the rotation at the plasma edge, partly due to insufficient understanding of 3D effects like braking and partly due to the uncertainties in the extrapolation of the present momentum transport results to a larger device.

VL - 51 SN - 0029-5515 IS - 12 N1 - ISI Document Delivery No.: 865YKTimes Cited: 0Cited Reference Count: 70 U1 -FP

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U5 - 76d59f479b968143a6d6d759b5aaecd1 ER - TY - JOUR T1 - Sawtooth control in fusion plasmas JF - Plasma Physics and Controlled Fusion Y1 - 2005 A1 - Graves, J. P. A1 - Angioni, C. A1 - Budny, R. V. A1 - Buttery, R. J. A1 - Coda, S. A1 - Eriksson, L. G. A1 - Gimblett, C. G. A1 - Goodman, T. P. A1 - Hastie, R. J. A1 - Henderson, M. A. A1 - Koslowski, H. R. A1 - Mantsinen, M. J. A1 - Martynov, A. A1 - Mayoral, M. L. A1 - Muck, A. A1 - M F F Nave A1 - Sauter, O. A1 - Westerhof, E. VL - 47 SN - 0741-3335 UR -