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  • 101. Spolaore, M.
    et al.
    Antoni, V.
    Cavazzana, R.
    Regnoli, G.
    Serianni, G.
    Spada, E.
    Vianello, N.
    Bergsåker, Henric
    KTH, Superseded Departments, Alfvén Laboratory.
    Drake, James R.
    KTH, Superseded Departments, Alfvén Laboratory.
    Effects of ExB velocity shear on electrostatic structures2002In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 9, no 10, p. 4110-4113Article in journal (Refereed)
  • 102.
    Strauss, H.
    et al.
    HRS Fus, W Orange, NJ 07052 USA..
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Stefanikova, Estera
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tolias, Panagiotis
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olivares, Pablo Vallejos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zhou, Yushun
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics. KTH, Fusion Plasma Phys, EES, SE-10044 Stockholm, Sweden..
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland..
    et al.,
    Comparison of JETAVDE disruption data with M3D simulations and implications for ITER2017In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 24, no 10, article id 102512Article in journal (Refereed)
    Abstract [en]

    Nonlinear 3D MHD asymmetric vertical displacement disruption simulations have been performed using JET equilibrium reconstruction initial data. Several experimentally measured quantities are compared with the simulation. These include vertical displacement, halo current, toroidal current asymmetry, and toroidal rotation. The experimental data and the simulations are in reasonable agreement. Also compared was the correlation of the toroidal current asymmetry and the vertical displacement asymmetry. The Noll relation between asymmetric wall force and vertical current moment is verified in the simulations. Also verified is the toroidal flux asymmetry. Although in many ways, JET is a good predictor of ITER disruption behavior, JET and ITER can be in different parameter regimes, and extrapolating from JET data can overestimate the ITER wall force.

  • 103.
    Tholerus, Emmi
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    The effects of phase decorrelation on the dynamics of the bump-on-tail instability2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 8, article id 082106Article in journal (Refereed)
    Abstract [en]

    The dynamics of the bump-on-tail instability has been studied. The novelty of the work is the analysis of how the bump-on-tail dynamics is affected by an extrinsic stochastisation of the phase of the wave-particle interaction; here referred to as phase decorrelation. For this purpose, a nonlinear Monte Carlo model has been developed. When the characteristic time scale for macroscopic phase decorrelation becomes shorter than time scales of nonlinear wave-particle dynamics, the system may be described quasilinearly, with the phase decorrelation being replaced by a quasilinear diffusion coefficient in particle energy. A purely quasilinear Monte Carlo model, which is typically less computationally demanding than the fully nonlinear description due to the reduced dimensionality of phase space, has been developed for comparison. In this paper, parameter regimes, where the nonlinear and the quasilinear descriptions quantitatively agree on a macroscopic level, have been investigated, using combined theoretical and numerical analyses. Qualitative effects on the macroscopic dynamics by the presence of phase decorrelation and/or by structures of the energy distribution function in the proximity of the wave-particle resonance are also studied.

  • 104.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Castello, F. Lucco
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Isomorph-based empirically modified hypernetted-chain approach for strongly coupled Yukawa one-component plasmas2019In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 26, no 4, article id 043703Article in journal (Refereed)
    Abstract [en]

    Isomorph theory is employed in order to establish a mapping between the bridge function of Coulomb and Yukawa one-component plasmas. Within an exact invariance ansatz for the bridge functions and by capitalizing on the availability of simulation-extracted Coulomb bridge functions, an analytical Yukawa bridge function is derived which is inserted into the integral theory framework. In spite of its simplicity and computational speed, the proposed integral approach exhibits an excellent agreement with computer simulations of dense Yukawa liquids without invoking adjustable parameters. 

  • 105.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Scattering of radiation in collisionless dusty plasmas2013In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 20, no 4, p. 043706-Article in journal (Refereed)
    Abstract [en]

    Scattering of electromagnetic waves in collisionless dusty plasmas is studied in the framework of a multi-component kinetic model. The investigation focuses on the spectral distribution of the scattered radiation. Pronounced dust signatures are identified in the coherent spectrum due to scattering from the shielding cloud around the dust grains, dust acoustic waves, and dust-ion acoustic waves. The magnitude and shape of the scattered signal near these spectral regions are determined with the aid of analytical expressions and its dependence on the dust parameters is investigated. The use of radiation scattering as a potential diagnostic tool for dust detection is discussed.

  • 106.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Screening in weakly ionized dusty plasmas; effect of dust density perturbations2013In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 20, no 2, p. 023702-Article in journal (Refereed)
    Abstract [en]

    The screening of the charge of a non-emitting dust grain immersed in a weakly ionized dusty plasma is studied on the basis of a self-consistent hydrodynamic description. The dust number density is considered large enough so that the test grain is not isolated from other grains and dust collective effects are important. Not only dust charge perturbations but also dust density perturbations are taken into account, the latter are shown to have a strong effect on both the short and long range part of the potential. The realization of collective attraction via the newly obtained potential is discussed, a mechanism that could be central to the understanding of phase-transitions and self-organization processes in dusty plasmas.

  • 107.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    de Angelis, U.
    Kinetic models of partially ionized complex plasmas in the low frequency regime2011In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 18, no 7, p. 073705-Article in journal (Refereed)
    Abstract [en]

    The results from three kinetic models of complex plasmas taking into account collisions with neutrals are compared in the low-frequency regime: The "full" model which considers the absorption of plasma fluxes on dust particles and dust charge fluctuations, the "multi-component" model where both these effects are neglected, and the "standard" model which takes into account the dust charge perturbations but not the absorption of fluxes. We derive and numerically evaluate expressions of the low frequency responses of these models, also taking into account the modification of the capture cross-sections due to the effect of neutrals. The role of plasma sources and collisions with neutrals is assessed by computing the plasma permittivities and static permittivities for all the three models.

  • 108.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    de Angelis, U.
    Regimes for experimental tests of kinetic effects in dust acoustic waves2010In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 17, no 10, p. 103707-Article in journal (Refereed)
    Abstract [en]

    The low frequency responses of a kinetic model of dusty plasma, taking into account the absorption of the plasma particles on the dust particles and fluctuations of dust charge, are evaluated numerically in order to identify realistic experimental parameter regimes where charging effects are dominant. A range of parameters in terms of dust number density and size as well as plasma densities, where significant differences with the multicomponent approach can be found, is proposed. General expressions for the imaginary parts of the low frequency responses are derived and numerical results for the damping rate in the corresponding ranges are provided to ensure that observations of dust-acoustic waves in those conditions are plausible.

  • 109.
    Tolias, Panagiotis
    et al.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. Sezione di Napoli, Italy.
    Ratynskaia, Svetlana
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    de Angelis, U.
    Soft mean spherical approximation for dusty plasma liquids: Level of accuracy and analytic expressions2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 8, article id 083703Article in journal (Refereed)
    Abstract [en]

    The soft mean spherical approximation is employed for the study of the thermodynamics of dusty plasma liquids, the latter treated as Yukawa one-component plasmas. Within this integral theory method, the only input necessary for the calculation of the reduced excess energy stems from the solution of a single non-linear algebraic equation. Consequently, thermodynamic quantities can be routinely computed without the need to determine the pair correlation function or the structure factor. The level of accuracy of the approach is quantified after an extensive comparison with numerical simulation results. The approach is solved over a million times with input spanning the whole parameter space and reliable analytic expressions are obtained for the basic thermodynamic quantities.

  • 110. Tracy, E. R.
    et al.
    Kaufman, A. N.
    Jaun, André
    KTH, School of Computer Science and Communication (CSC), Numerical Analysis and Computer Science, NADA.
    Local fields for asymptotic matching in multidimensional mode conversion2007In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 14, no 8Article in journal (Refereed)
    Abstract [en]

    The problem of resonant mode conversion in multiple spatial dimensions is considered. Using phase space methods, a complete theory is developed for constructing matched asymptotic expansions that fit incoming and outgoing WKB solutions. These results provide, for the first time, a complete and practical method for including multidimensional conversion in ray tracing algorithms. The paper provides a self-contained description of the following topics: (1) how to use eikonal (also known as ray tracing or WKB) methods to solve vector wave equations and how to detect conversion regions while following rays; (2) once conversion is detected, how to fit to a generic saddle structure in ray phase space associated with the most common type of conversion; (3) given the saddle structure, how to carry out a local projection of the full vector wave equation onto a local two-component normal form that governs the two resonantly interacting waves. This determines both the uncoupled dispersion functions and the coupling constant, which in turn determine the uncoupled WKB solutions; (4) given the normal form of the local two-component wave equation, how to find the particular solution that matches the amplitude, phase, and polarization of the incoming ray, to the amplitude, phase, and polarization of the two outgoing rays: the transmitted and converted rays.

  • 111. Tsypin, V. S.
    et al.
    Vladimirov, S. V.
    Galvao, R. M. O.
    Nascimento, I. C.
    Tendler, Michael
    KTH, Superseded Departments, Alfvén Laboratory.
    Kuznetsov, Y. K.
    Particle flows in dusty plasmas of the tokamak edge2004In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 11, no 8, p. 4138-4141Article in journal (Refereed)
    Abstract [en]

    In this Brief Communication the plasma flows and ambipolar electric field induced due to the temperature stresses on ions are estimated. These flows are similar to the plasma residual rotations in tokamaks, but are related to dust contamination of tokamak plasmas. The induced electric field might be very important for creating transport barriers in tokamaks.

  • 112.
    Uccello, Andrea
    et al.
    CNR, IFP, Ist Fis Plasma Piero Caldirola, Via Roberto Cozzi 53, I-20125 Milan, Italy..
    Bergsåker, Henric
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Bykov, Igor
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Elevant, Thomas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Frassinetti, Lorenzo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Garcia-Carrasco, Alvaro
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Hellsten, Torbjörn
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Ivanova, Darya
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Johnson, Thomas
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Menmuir, Sheena
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Petersson, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Ström, Petter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Tholerus, Emmi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Fusion Plasma Physics.
    Weckmann, Armin
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Zychor, I.
    Inst Plasma Phys & Laser Microfus, PL-01497 Warsaw, Poland..
    Comparison of dust transport modelling codes in a tokamak plasma2016In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 23, no 10, article id 102506Article in journal (Refereed)
    Abstract [en]

    Since the installation on the Joint European Torus of the ITER-like Wall (ILW), intense radiation spikes have been observed, especially in the discharges following a disruption, and have been associated with possible sudden injection of tungsten (W) impurities consequent to full ablation of W dust particles. The problem of dust production, mobilization, and interaction both with the plasma and the vessel tiles is therefore of great concern and requires the setting up of dedicated and validated numerical modeling tools. Among these, a useful role is played by the dust trajectory calculators, which can present in a relatively clear way the qualitative and quantitative description of the mobilization and fate of selected bunches of dust grains.

  • 113.
    Vignitchouk, Ladislas
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Delzanno, G. L.
    Los Alamos Natl Lab, Theoret Div, Los Alamos, NM 87545 USA..
    Tolias, Panagiotis
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Ratynskaia, Svetlana V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Space and Plasma Physics.
    Electron reflection effects on particle and heat fluxes to positively charged dust subject to strong electron emission2018In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 25, no 6, article id 063702Article in journal (Refereed)
    Abstract [en]

    A new model describing dust charging and heating in unmagnetized plasmas in the presence of large electron emission currents is presented. By accounting for the formation of a potential well due to trapped emitted electrons when the dust is positively charged, this model extends the so-called OML+ approach, thus far limited to thermionic emission, by including electron-induced emission processes, and in particular low-energy quasi-elastic electron reflection. Revised semi-analytical formulas for the current and heat fluxes associated with emitted electrons are successfully validated against particle-in-cell simulations and predict an overall reduction of dust heating by up to a factor of 2. When applied to tungsten dust heating in divertor-like plasmas, the new model predicts that the dust lifetime increases by up to 80%, as compared with standard orbital-motion-limited estimates.

  • 114. Webster, A. J.
    et al.
    Morris, J.
    Todd, T. N.
    Brezinsek, S.
    Coad, P.
    Likonen, J.
    Rubel, Marek
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Resonant-like behaviour during edge-localised mode cycles in the Joint European Torus2015In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 22, no 8, article id 082501Article in journal (Refereed)
    Abstract [en]

    A unique sequence of 120 almost identical plasmas in the Joint European Torus (JET) recently provided two orders of magnitude more statistically equivalent data than ever previously available. The purpose was to study movement of eroded plasma-facing material from JET's new Beryllium wall, but it has allowed the statistical detection of otherwise unobservable phenomenon. This includes a sequence of resonant-like waiting times between edge-localised plasma instabilities (ELMs), instabilities that must be mitigated or avoided in large magnetically confined plasmas such as those planned for ITER. Here, we investigate the cause of this phenomenon, using the unprecedented quantity of data to produce a detailed picture of the plasma's behaviour. After combining the data, oscillations are clearly observable in the plasma's vertical position, in edge losses of ions, and in Beryllium II (527 nm) light emissions. The oscillations are unexpected, are not obvious in data from a single pulse alone, and are all clearly correlated with each other. They are likely to be caused by a small vertical oscillation that the plasma control system is not reacting to prevent, but a more complex explanation is possible. The clearly observable but unexpected link between small changes in the plasma's position and changes to edge-plasma transport and stability suggest that these characteristics cannot always be studied in isolation. It also suggests new opportunities for ELM mitigation and control that may exist.

  • 115. Wu, D J
    et al.
    Huang, G L
    Wang, D Y
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Solitary kinetic Alfven waves in the two-fluid model1996In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 3, p. 2879-2884Article in journal (Refereed)
    Abstract [en]

    Employing the two-fluid model, a generalized Sagdeev equation governing solitary kinetic Alfven waves (SKAWs) and the criterion for the existence of SKAWs, which are valid for different ranges of plasma pressure parameter beta, are presented. In the limit cases of beta much greater than m(e)/m(i) and beta much less than m(e)/m(i), the present results correspond, respectively, with conclusions obtained by Hasegawa ct al. [Phys. Rev. Lett. 37, 690 (1976)] and by Shukla et al. [J. Plasma Phys. 28, 125 (1982)], that is, SKAWs accompanied by, respectively, hump and dip density solitons for beta much greater than m(e)/m(i) and beta much less than m(e)/m(i). However, for the case of beta similar to m(e)/m(i), the present results show that SKAWs accompanied by both hump and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying these results to electromagnetic spikes observed by the Freja scientific satellite is discussed [detailed information about the Freja satellite experiments can be found in serial papers presented in Space Sci. Rev. 70, Nos. 3/4 (1994)]. (C) 1996 American Institute of Physics.

  • 116. Wu, D.J.
    et al.
    Wang, D.Y.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    An analytical solution of finite‐amplitude solitary kinetic Alfvén waves1995In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 2, p. 4476-4481Article in journal (Refereed)
    Abstract [en]

    An analytical solution of finite-amplitude solitary kinetic Alfven waves (SKAWs) in a low-beta (beta much less than m(e)/m(i) much less than 1) plasma is presented. This solution has been compared with the solution of the Korteweg-de Vries (KdV) equation in the small-amplitude limit. It is found that the KdV soliton solution is valid only for the maximum relative density perturbation N-m<0.1. For the larger N-m, the exact analytical solution shows that the SKAWs have a much wider structure and much stronger perturbed fields than the KdV solitons with the same N-m. Moreover, the relations between the width and the amplitude of SKAWs are also considerably different from that of the KdV solitons. In addition the possibility for applying these results to some events observed from the Freja scientific satellite is discussed. (The Freja is a Swedish-German scientific project for the investigation of ionospheric and magnetospheric plasmas, and the Freja satellite was launched on a Long-March II rocket of China on October 6, 1992.) (C) 1995 American Institute of Physics.

  • 117.
    Yadikin, Dimitry
    et al.
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Brunsell, Per
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics. KTH, School of Electrical Engineering (EES), Centres, Alfvén Laboratory Centre for Space and Fusion Plasma Physics.
    Paccagnella, R.
    Advanced feedback control methods in EXTRAP T2R2006In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 13, no 7, p. 072109-Article in journal (Refereed)
    Abstract [en]

    Previous experiments in the EXTRAP T2R reversed field pinch device have shown the possibility of suppression of multiple resistive wall modes (RWM). A feedback system has been installed in EXTRAP T2R having 100% coverage of the toroidal surface by the active coil array. Predictions based on theory and the previous experimental results show that the number of active coils should be sufficient for independent stabilization of all unstable RWMs in the EXTRAP T2R. Experiments using different feedback schemes are performed, comparing the intelligent shell, the fake rotating shell, and the mode control with complex feedback gains. Stabilization of all unstable RWMs throughout the discharge duration of t(d)approximate to 10 tau(w) is seen using the intelligent shell feedback scheme. Mode rotation and the control of selected Fourier harmonics is obtained simultaneously using the mode control scheme with complex gains. Different sensor signals are studied. A feedback system with toroidal magnetic field sensors could have an advantage of lower feedback gain needed for the RWM suppression compared to the system with radial magnetic field sensors. In this study, RWM suppression is demonstrated, using also the toroidal field component as a sensor signal in the feedback system.

  • 118. Yagi, Y.
    et al.
    Frassinetti, Lorenzo
    Advanved insittute of Industrial Science and Technology (JAPAN).
    Hirano, Y.
    Koguchi, H.
    Sakakita, H.
    The magnitude of sawtooth crash events in multiple and quasi-single helicity states in a reversed-field-pinch plasma2005In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 12, no 8, p. 082507-Article in journal (Refereed)
    Abstract [en]

    Factors affecting the magnitude of sawtooth crashes in soft x-ray (SXR) signals (I-SXR) have been studied using data from high-Theta (pinch parameter) discharges in the toroidal pinch experiment TPE-1RM20 reversed-field pinch device [Y. Yagi , J. Plasma Fusion Research 69, 700 (1993)]. In TPE-1RM20, discharges with a high Theta that are free of large sawteeth (improved high-Theta mode discharges), spontaneously appeared [Y. Hirano , Nucl. Fusion 36, 721 (1996)] among typical conventional discharges exhibiting large sawtooth crashes. The reason for the spontaneous appearance of sawtooth-free discharges has been unclear. It is shown that the normalized magnitude of the SXR crashes, [Delta(I-SXR)/I-SXR], is well correlated with the m (poloidal mode number)=0 mode amplitude in the postcrash phase. It is also shown that Delta(I-SXR)/I-SXR is smaller when the quasi-single helicity state precedes the crash rather than when the multiple-helicity state precedes the crash, and Delta(I-SXR)/I-SXR is smaller when E-parallel to (the parallel electric field at the plasma surface) is approximately zero in the precrash phase rather than E-parallel to being negative.

  • 119. Yagi, Y
    et al.
    Koguchi, H
    Sakakita, H
    Sekine, S
    Brunsell, P R
    KTH, Superseded Departments, Alfvén Laboratory.
    Malmberg, J-A
    KTH, Superseded Departments, Alfvén Laboratory.
    Evolution process of the mode wall-locking and phase-locking in a reversed field pinch plasma2001In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 8, no 5, p. 1625-1635Article in journal (Refereed)
  • 120. Yaroshenko, V.
    et al.
    Ratynskaia, Svetlana V.
    Khrapak, S.
    Thoma, M. H.
    Kretschmer, M.
    Hofner, H.
    Morfill, G. E.
    Zobnin, A.
    Usachev, A.
    Petrov, O.
    Fortov, V.
    Determination of the ion-drag force in a complex plasma2005In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 12, no 9Article in journal (Refereed)
    Abstract [en]

    The ion-drag force acting on dust particles in the positive column of a dc discharge is measured in the pressure range of 20-120 Pa. The force is obtained by a method which does not require a priori knowledge of the particle charge, but uses the charge gradient determined from the same experiment. The method depends only on two experimentally determined quantities: the particle drift velocity and the electric field. The comparison of experimental results with theoretical models is presented and discussed.

  • 121. Zhao, M. L.
    et al.
    Chen, Y. P.
    Guo, H. Y.
    Ye, M. Y.
    Tendler, Michael
    KTH, School of Electrical Engineering (EES), Fusion Plasma Physics.
    Li, G. Q.
    Luo, Z. P.
    Modeling of divertor geometry effects in China fusion engineering testing reactor by SOLPS/B2-Eirene2014In: Physics of Plasmas, ISSN 1070-664X, E-ISSN 1089-7674, Vol. 21, no 5, p. 052503-Article in journal (Refereed)
    Abstract [en]

    The China Fusion Engineering Testing Reactor (CFETR) is currently under design. The SOLPS/B2-Eirene code package is utilized for the design and optimization of the divertor geometry for CFETR. Detailed modeling is carried out for an ITER-like divertor configuration and one with relatively open inner divertor structure, to assess, in particular, peak power loading on the divertor target, which is a key issue for the operation of a next-step fusion machine, such as ITER and CFETR. As expected, the divertor peak heat flux greatly exceeds the maximum steady-state heat load of 10MW/m(2), which is a limit dictated by engineering, for both divertor configurations with a wide range of edge plasma conditions. Ar puffing is effective at reducing divertor peak heat fluxes below 10MW/m(2) even at relatively low densities for both cases, favoring the divertor configuration with more open inner divertor structure.

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