Magnetic confinement experiment -- 1: Tokamaks
International Nuclear Information System (INIS)
This report reviews presentations made at the 15th IAEA Conference on Plasma Physics and Controlled Nuclear Fusion on experimental tokamak physics, particularly on advances in core plasma physics, divertor and edge physics, heating and current drive, and tokamak concept optimization
Magnetic confinement experiment. I: Tokamaks
International Nuclear Information System (INIS)
Reports were presented at this conference of important advances in all the key areas of experimental tokamak physics: Core Plasma Physics, Divertor and Edge Physics, Heating and Current Drive, and Tokamak Concept Optimization. In the area of Core Plasma Physics, the biggest news was certainly the production of 9.2 MW of fusion power in the Tokamak Fusion Test Reactor, and the observation of unexpectedly favorable performance in DT plasmas. There were also very important advances in the performance of ELM-free H- (and VH-) mode plasmas and in quasi-steady-state ELM'y operation in JT-60U, JET, and DIII-D. In all three devices ELM-free H-modes achieved nTτ's ∼ 2.5x greater than ELM'ing H-modes, but had not been sustained in quasi-steady-state. Important progress has been made on the understanding of the physical mechanism of the H-mode in DIII-D, and on the operating range in density for the H-mode in Compass and other devices
Turbulence, transport and confinement: from tokamaks to star magnetism
International Nuclear Information System (INIS)
This thesis is part of the general study of self-organization in hot and magnetized plasmas. We focus our work on two specific objects: stars and tokamaks. We use first principle numerical simulations to study turbulence, transport and confinement in these plasmas. The first part of this thesis introduces the main characteristics of stellar and tokamak plasmas. The reasons for studying them together are properly detailed. The second part is focused on stellar aspects. We study the interactions between the 3D turbulent motions in the solar convection zone with an internal magnetic field in the tachocline (the transition region between the instable and stable zones in the Sun). The tachocline is a very thin layer (less than five percent of the solar radius) that acts as a transport barrier of angular momentum. We show that such an internal magnetic field is not likely to explain the observed thickness of the tachocline and we give some insights on how to find alternative mechanisms to constrain it. We also explore the effect of the environment of star on its structure. We develop a methodology to study the influence of stellar wind and of the magnetic coupling of a star with its orbiting planets. We use the same methodology to analyse the magnetic interaction between a stellar wind and a planetary magnetosphere that acts as a transport barrier of matter. Then, the third part is dedicated to fusion oriented research. We present a numerical investigation on the experimental mechanisms that lead to the development of transport barriers in the plasma. These barriers are particularly important for the design of high performance fusion devices. The creation of transport barriers is obtained in turbulent first principle simulations for the very first time. The collaboration between the two scientific teams lead to the results presented in the fourth part of this thesis. An original spectral method is developed to analyse the saturation of stellar convective dynamos and of
Confinement of a self-stabilized tokamak under average magnetic well conditions
International Nuclear Information System (INIS)
It is well known that the average favorable magnetic curvature of a tokamak is stabilizing with respect to pressure-driven magnetohydrodynamic instabilities at low beta and that self-stabilization occurs at finite beta in the so-called second stability regime. Here we self-consistently investigate how these two effects, viz., the mean magnetic well and the self-stabilization, influence the energy confinement time in a tokamak, using the ballooning mode transport model
Confinement and diffusion in tokamaks
International Nuclear Information System (INIS)
The effect of electric field fluctuations on confinement and diffusion in tokamak is discussed. Based on the experimentally determined cross-field turbolent diffusion coefficient, D∼3.7*cTe/eB(δni/ni)rms which is also derived by a simple theory, the cross-field diffusion time, tp=a2/D, is calculated and compared to experimental results from 51 tokamak for standard Ohmic operation
Enhancement of confinement in tokamaks
International Nuclear Information System (INIS)
A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime
DEFF Research Database (Denmark)
Mantica, P.; Challis, C.; Peeters, A.G.; Strintzi, D.; Tala, T.; Tsalas, M.; deVries, P.C.; Baiocchi, B.; Baruzzo, M.; Bizarro, J.; Buratti, P.; Citrin, J.; Colyer, G.; Crisanti, F.; Garbet, X.; Giroud, C.; Hawkes, N.; Hobirk, J.; Imbeaux, F.; Joffrin, E.; Johnson, T.; Lerche, E.; Mailloux, J.; Naulin, Volker; Salmi, A.; Sozzi, C.; Staebler, G.; Van Eester, D.; Versloot, T.; Weiland, J.
2011-01-01
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...
Modular tokamak magnetic system
Yang, Tien-Fang
1988-01-01
A modular tokamak system comprised of a plurality of interlocking moldules. Each module is comprised of a vacuum vessel section, a toroidal field coil, moldular saddle coils which generate a poloidal magnetic field and ohmic heating coils.
Summary report on tokamak confinement experiments
International Nuclear Information System (INIS)
There are currently five major US tokamaks being operated and one being constructed under the auspices of the Division of Toroidal Confinement Systems. The currently operating tokamaks include: Alcator C at the Massachusetts Institute of Technology, Doublet III at the General Atomic Company, the Impurity Studies Experiment (ISX-B) at the Oak Ridge National Laboratory, and the Princeton Large Torus (PLT) and the Poloidal Divertor Experiment (PDX) at the Princeton Plasma Physics Laboratory. The Tokamak Fusion Test Reactor (TFTR) is under construction at Princeton and should be completed by December 1982. There is one major tokamak being funded by the Division of Applied Plasma Physics. The Texas Experimental Tokamak (TEXT) is being operated as a user facility by the University of Texas. The TEXT facility includes a complete set of standard diagnostics and a data acquisition system available to all users
International Nuclear Information System (INIS)
In preparation for the Frascati Tokamak Upgrade (FTU) 2007 experimental programme, the priorities were changed to some extent to allow more machine time to be allocated to new ideas and to take into account the reduced power availability. In fact a filament failure of two of the six lower hybrid (LH) gyrotrons and an unfortunate accident to one out of the four electron cyclotron gyrotrons during its transportation to the Frascati laboratories made it impossible to reach the high performance foreseen for the advanced-scenario programme. Emphasis was placed on the study of the high-density and peaked-profile regimes obtained in operations with the liquid lithium limiter (LLL) and control of magnetohydrodynamic (MHD) modes and disruptions. High priority was also given to the study of electron fishbone instability, which is theoretically expected in the presence of fast electrons generated by LH and electron cyclotron resonance heating (ECRH). Some relevance was also allocated to the study of dust dynamics in the scrape-off layer (SOL). Unfortunately, a series of contingencies affecting the spring campaign hampered the continuity of operations and hence strongly reduced the time devoted to scientific activities. Although the reliability of most of the machine subsystems allowed about seven weeks of operations, with 90% efficiency, only two weeks were effectively devoted to the scientific programme. After some problems connected with CO2 contamination of the main vacuum, the autumn campaign was not successful and then definitively cancelled because of a fault on the poloidal system power supply
Confinement scaling and ignition in tokamaks
International Nuclear Information System (INIS)
A drift wave turbulence model is used to compute the scaling and magnitude of central electron temperature and confinement time of tokamak plasmas. The results are in accord with experiment. Application to ignition experiments shows that high density (1 to 2) . 1015 cm-3, high field, B/sub T/ > 10 T, but low temperature T approx. 6 keV constitute the optimum path to ignition
Current profile control and improved confinement in JT-60 tokamak plasmas
Energy Technology Data Exchange (ETDEWEB)
Fujita, Takaaki [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
2002-08-01
In a tokamak, one of toroidal shaped magnetic confinement systems, a large toroidal current induced in a high temperature plasma produces helical magnetic fields to confine the plasma itself. Therefore, the spatial structure of confining magnetic fields can be determined by measuring the profile of the plasma current. This can lead to the understanding of the transport and stability properties of the plasma. In this review, a novel technique using the motional Stark effect to measure the current profile in the JT-60 tokamak is shown. With the aid of this technique, a new operational mode of a tokamak, with which the plasma confinement can be substantially improved, has been discovered. Recent experimental results of confinement improvement with the current profile control are presented. (author)
Current profile control and improved confinement in JT-60 tokamak plasmas
International Nuclear Information System (INIS)
In a tokamak, one of toroidal shaped magnetic confinement systems, a large toroidal current induced in a high temperature plasma produces helical magnetic fields to confine the plasma itself. Therefore, the spatial structure of confining magnetic fields can be determined by measuring the profile of the plasma current. This can lead to the understanding of the transport and stability properties of the plasma. In this review, a novel technique using the motional Stark effect to measure the current profile in the JT-60 tokamak is shown. With the aid of this technique, a new operational mode of a tokamak, with which the plasma confinement can be substantially improved, has been discovered. Recent experimental results of confinement improvement with the current profile control are presented. (author)
Tokamak plasma self-organization-synergetics of magnetic trap plasmas
Razumova, K. A.; Andreev, V. F.; Eliseev, L. G.; Kislov, A. Y.; La Haye, R. J.; Lysenko, S. E.; Melnikov, A. V.; Notkin, G. E.; Pavlov, Y. D.; Kantor, M. Y.
2011-01-01
Analysis of a wide range of experimental results in plasma magnetic confinement investigations shows that in most cases, plasmas are self-organized. In the tokamak case, it is realized in the self-consistent pressure profile, which permits the tokamak plasma to be macroscopically MHD stable. Existin
Alternative lines with magnetic plasma confinement
International Nuclear Information System (INIS)
Plasma confinement with the aid of a magnetic field is the most common and also the most frequently investigated principle on the way to controlled nuclear fusion. Apart from the Tokamak principle, which is the most advanced principle as far as fusion-relevant plasma parameters are concerned, also other approaches are being investigated, e.g. the mirror device, the bumpy tons, and the stellarator. In principle, all three concepts permit 'stationary' plasma confinement in a stationary fusion reactor. Compared with the pulsed Tokamak reactor, this is a considerable advantage. (orig./GG)
Physics of magnetic confinement fusion
Directory of Open Access Journals (Sweden)
Wagner F.
2013-06-01
Full Text Available Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — tokamaks and stellarators — will be introduced and described. The first fusion reactor, ITER, and the most modern stellarator, Wendelstein 7-X, are under construction. Their basic features and objectives will be presented.
Enhanced Energy Confinement and Performance in a Low-Recycling Tokamak
International Nuclear Information System (INIS)
Extensive lithium wall coatings and liquid lithium plasma-limiting surfaces reduce recycling, with dramatic improvements in Ohmic plasma discharges in the Current Drive Experiment-Upgrade. Global energy confinement times increase by up to 6 times. These results exceed confinement scalings such as ITER98P(y,1) by 2-3 times, and represent the largest increase in energy confinement ever observed for an Ohmic tokamak plasma. Measurements of Dα emission indicate that global recycling coefficients decrease to approximately 0.3, the lowest documented for a magnetically confined hydrogen plasma
Magnetic microtearing coherence in tokamak plasmas
International Nuclear Information System (INIS)
The analyses of the microtearing-modes coherence is effected. The tokamak characteristics, concerning fusion, electromagnetic confinement and turbulence are reviewed. The nature of the tearing modes, the variational principle of linear mode studies, a linear study in collisional and non-collisional plasma conditions are summarized, before studying the microtearing-mode coherence. The flux line configuration in the presence of a magnetic turbulence, the plasma response to a microtearing perturbation and instability, in the presence of a radial-electrons diffusion, is described. The autocoherence of microtearing modes in non-linear conditions are analyzed
Magnetic confinement fusion plasma theory, Task 1
International Nuclear Information System (INIS)
The research performed under this grant during the current year has concentrated on a few key tokamak plasma confinement and heating theory issues: extensive development of a new Chapman-Enskog-like fluid/kinetic hybrid approach to deriving rigorously valid fluid moment equations; applications (neoclassical viscous force, instabilities in the banana-plateau collisionality regime, nonlinear gyroviscous force, unified plasma microinstability equations and their implications, semi-collisional presheath modeling, etc.) of this new formalism; interactions of fluctuating bootstrap-current-driven magnetic islands; determination of net transport processes and equations for a tokamak; and some other topics (extracting more information from heat-pulse-propagation data, modeling of BES fluctuation data, exploring sawtooth effects on energy confinement in DIII-D, divertor X-point modeling). Recent progress and publications in these areas, and in the management of the local NERSC node and fusion theory DECstation 5000 at UW-Madison are summarized briefly in this report
Heating and confinement studies with ECRH in the TCV tokamak
International Nuclear Information System (INIS)
ECRH experiments have recently started on the TCV tokamak with the use of 1 MW, X2 heating. The ECW system installations is continuing and will eventually provide 3 MW X2 and 1.5 MW X3. The study of the effects of different heating localizations is possible using 1) the mobile mirrors of the launcher, 2) the large vertical room for displacing the plasma in the TCV vessel and 3) the radial displacement of the cyclotron resonance with magnetic field. Initial studies of heating and confinement have concentrated mostly on close-to-circular plasmas to allow the largest variation of beam-plasma geometry and to allow comparison with earlier results on other machines - a necessary first step before investigating more strongly shaped plasmas. For TCV parameters, the nominal field of B = 1.44 T and the frequency of 82.7 GHz of X2 gyrotrons places the resonance position on the high-field side (HFS) of the magnetic axis; while the frequency of 118 GHz of X3 gyrotrons results in a slightly low-field side (LFS) resonance position. (author) 6 figs., 4 refs
Next step tokamak physics: Confinement-oriented global database analysis
International Nuclear Information System (INIS)
We describe and analyse an international multi-tokamak confinement database, both motivated by physics and with a view toward prediction of next-step burning-plasma experiments such as ITER. Significant additional ohmic and L-mode data have been assembled from several tokamaks, which has resulted in the 'ITERL.DB2' dataset. Simple density-roll-over scalings are presented for ohmic confinement. For H-mode, the confinement time in the essentially enlarged data set ITERH.DB3 is compared with the ITERH-98P(y,2) reference scaling. A distinction is made between discharges with and without heavy gaspuff. Beyond a standard power-law scaling, the empirical 'influence' on confinement of q95=qcyl, directly related to triangularity, and of the global density peaking factor (for L- and H-mode) is quantified. A log-linear quadratic formula is given which describes physically more precisely than ITERH-98P(y,2) the relation between the isotope effect and the heating power degradation of confinement, while predicting a similar thermal confinement time for ITER (τE,th≅3:5 s.). Based on a recently provided plasma edge dataset, 'E.1', separate scalings of the plasma core and pedestal energy are derived. Finally, a class of nonlinear scalings is discussed which are suitable, in contrast to offset (non-)linear models, to fit roll-over dependence, and, simultaneously, the scaling of L-mode and H-mode confinement. (author)
Calculation about a modification to the toroidal magnetic field of the Tokamak Novillo. Part I
International Nuclear Information System (INIS)
The charged particles that constitute the plasma in the tokamaks are located in magnetic fields that determine its behavior. The poloidal magnetic field of the plasma current and the toroidal magnetic field of the tokamak possess relatively big gradients, which produce drifts on these particles. These drifts are largely the cause of the continuous lost of particles and of energy of the confinement region. In this work the results of numerical calculations of a modification to the 'traditional' toroidal magnetic field that one waits it diminishes the drifts by gradient and improve the confinement properties of the tokamaks. (Author)
Magnetic turbulence in Tokamaks
International Nuclear Information System (INIS)
From a discussion of the disruption process, it is concluded that this process plausibly consists of the onset of a fine grain turbulence. This turbulence must be able to produce the large values of the inductive electric field which are associated with the reorganization of the poloidal flux and the current density on the magnetic surfaces. It is then plausible that the turbulence belongs to a class of 'rippling' modes, that may explain the experimental values for the magnetic perturbations corresponding to a substantial radial ergodicity of the flux lines. The stability of the modes in the presence of such an ergodicity is accordingly considered. It is found that the modes may be unstable even in collisionless regime, the ergodicity playing a role similar to the resistivity to partially remove the M.H.D. constraint
Magnetic mirror confinement concepts system studies
International Nuclear Information System (INIS)
This report discusses the following topics: world survey of mirror confinement research facilities; data base on mirror confinement program budget milestone; Fokker-Planck modeling of tandem mirror confinement; review of diagnostic capabilities for tandem mirror research; tandem mirror reactor concept development; tandem mirror data base; and primer on tokamak confinement
West European magnetic confinement fusion research
International Nuclear Information System (INIS)
This report presents a technical assessment and review of the West European program in magnetic confinement fusion by a panel of US scientists and engineers active in fusion research. Findings are based on the scientific and technical literature, on laboratory reports and preprints, and on the personal experiences and collaborations of the panel members. Concerned primarily with developments during the past 10 years, from 1979 to 1989, the report assesses West European fusion research in seven technical areas: tokamak experiments; magnetic confinement technology and engineering; fusion nuclear technology; alternate concepts; theory; fusion computations; and program organization. The main conclusion emerging from the analysis is that West European fusion research has attained a position of leadership in the international fusion program. This distinction reflects in large measure the remarkable achievements of the Joint European Torus (JET). However, West European fusion prominence extends beyond tokamak experimental physics: the program has demonstrated a breadth of skill in fusion science and technology that is not excelled in the international effort. It is expected that the West European primacy in central areas of confinement physics will be maintained or even increased during the early 1990s. The program's maturity and commitment kindle expectations of dramatic West European advances toward the fusion energy goal. For example, achievement of fusion breakeven is expected first in JET, before 1995
Energy Confinement of High-Density Pellet-Fueled Plasmas in the Alcator C Tokamak
Greenwald, M.; Gwinn, D.; Milora, S.; Parker, J.; Parker, R.; Wolfe, S.; Besen, M.; Camacho, F.; Fairfax, S.; Fiore, C.; Foord, M.; Gandy, R.; Gomez, C.; Granetz, R.; Labombard, B.; Lipschultz, B.; Lloyd, B.; Marmar, E.; McCool, S.; Pappas, D.; Petrasso, R.; Pribyl, P.; Rice, J.; Schuresko, D.; Takase, Y.; Terry, J.; Watterson, R.
1984-07-01
A series of pellet-fueling experiments has been carried out on the Alcator C tokamak. High-speed hydrogen pellets penetrate to within a few centimeters of the magnetic axis, raise the plasma density, and produce peaked density profiles. Energy confinement is observed to increase over similar discharges fueled only by gas puffing. In this manner record values of electron density, plasma pressure, and Lawson number (n τ) have been achieved.
Magnetic diagnostics for the lithium tokamak experiment.
Berzak, L; Kaita, R; Kozub, T; Majeski, R; Zakharov, L
2008-10-01
The lithium tokamak experiment (LTX) is a spherical tokamak with R(0)=0.4 m, a=0.26 m, B(TF) approximately 3.4 kG, I(P) approximately 400 kA, and pulse length approximately 0.25 s. The focus of LTX is to investigate the novel low-recycling lithium wall operating regime for magnetically confined plasmas. This regime is reached by placing an in-vessel shell conformal to the plasma last closed flux surface. The shell is heated and then coated with liquid lithium. An extensive array of magnetic diagnostics is available to characterize the experiment, including 80 Mirnov coils (single and double axis, internal and external to the shell), 34 flux loops, 3 Rogowskii coils, and a diamagnetic loop. Diagnostics are specifically located to account for the presence of a secondary conducting surface and engineered to withstand both high temperatures and incidental contact with liquid lithium. The diagnostic set is therefore fabricated from robust materials with heat and lithium resistance and is designed for electrical isolation from the shell and to provide the data required for highly constrained equilibrium reconstructions. PMID:19044600
Energy confinement comparison of ohmically heated stellarators to tokamaks
International Nuclear Information System (INIS)
An empirical scaling prescribes that the energy confinement time in ohmically heated stellarators and tokamaks is proportional to the internal energy of the plasma and the minor radius, and inversely proportional to the current density. A thermal-conduction energy transport model, based on a heuristic assumption that the effective momentum transfer in the radial direction is proportional to the classical parallel momentum transfer which results in ohmic heating, is used to explain this scaling
Confinement of charged fusion products in reversed shear tokamak plasmas
International Nuclear Information System (INIS)
Full text: Recent tokamak studies indicate the attraction of operational scenarios with internal transport barriers (ITBs) that provide improved energy confinement with reversed shear (RS) in the plasma core. Whereas the presence of ITBs is beneficial to the energy confinement of the bulk plasma, RS is expected to deteriorate the confinement of fusion alphas (FA) in tokamaks with moderate plasma current, ∼2-3MA, due to enhanced first orbit and collisional loss. Experimentally, the influence of RS on the relaxation of the FA distribution function after NBI tritium blips into deuterium plasma has been observed recently in Trace Tritium Experiments on JET. In discharges with relatively high monotonic currents (>2MA) the observed FA density decay, was consistent with classical slowing down, while in 2.5MA strong RS discharges with a current hole ∼1/3 of the plasma radius the measured decay time was much shorter than the classical slowing down time, indicating a FA confinement degradation similar to that seen at 1MA current. Axisymmetric 3D Fokker-Planck modelling results presented confirm the confinement deterioration and the decay time decrease of FA distribution observed in RS JET discharges. (author)
Ohmic discharges with improved confinement in Tokamak Aditya
International Nuclear Information System (INIS)
ADITYA (R0 = 75 cm, a = 25 cm), an ohmically heated circular limiter tokamak is regularly being operated to carry out several experiments related to controlled thermonuclear fusion research. In recent experimental schedule, special efforts are made to enhance the plasma parameters to achieve Ohmic discharges with improved confinement. Repeatable plasma discharges of maximum plasma current of ∼ 160 kA and discharge duration beyond ∼ 250 ms with plasma current flattop duration of ∼ 140 ms has been obtained for the first time in the first Indian tokamak ADITYA. The discharge reproducibility has been improved with Lithium wall conditioning and much-improved plasma discharges are obtained by precisely controlling the plasma position. Improved discharges are attempted over a wider parameter range to carry out various confinement scaling experiments. In these discharges, chord-averaged electron density 1.0 - 4.0 X 1019m-3 using multiple hydrogen gas puffs, plasma temperature of the order of ∼ 400 - 700 eV has been achieved. The measured confinement time matches quite well with ALCATOR scaling for most of the discharges. It is also observed that in new discharges, the confinement time crosses the L-mode scaling. Detailed analysis of these discharges along with the possible reasons for obtaining higher confinement times will be addressed in this paper. (author)
Improvement of confinement characteristics of tokamak plasma by controlling plasma-wall interactions
International Nuclear Information System (INIS)
Relation between plasma-wall interactions and confinement characteristics of a tokamak plasma with respect to both impurity and fuel particle controls is discussed. Following results are obtained from impurity control studies: (1) Ion sputtering is the dominant mechanism of impurity release in a steady state tokamak discharge. (2) By applying carbon coating on entire first wall of DIVA tokamak, dominant radiative region is concentrated more in boundary plasma resulting a hot peripheral plasma with cold boundary plasma. (3) A physical model of divertor functions about impurity control is empilically obtained. By a computer simulation based on above model with respect to divertor functions for JT-60 tokamak, it is found that the allowable electron temperature of the divertor plasma is not restricted by a condition that the impurity release due to ion sputtering does not increase continuously. (4) Dense and cold divertor plasma accompanied with strong remote radiative cooling was diagnosed along the magnetic field line in the simple poloidal divertor of DOUBLET III tokamak. Strong particle recycling region is found to be localized near the divertor plate. by and from particle control studies: (1) The INTOR scaling on energy confinement time is applicable to high density region when a core plasma is fueled directly by solid deuterium pellet injection in DOUBLET III tokamak. (2) As remarkably demonstrated by direct fueling with pellet injection, energy confinement characteristics can be improved at high density range by decreasing particle deposition at peripheral plasma in order to reduce plasma-wall interaction. (3) If the particle deposition at boundary layer is necessarily reduced, the electron temperature at the boundary or divertor region increases due to decrease of the particle recycling and the electron density there. (J.P.N.)
Magnetic surfaces of toroidal helical fields in tokamaks
International Nuclear Information System (INIS)
It is proposed to analyse theoretically the disruptive instability that occurs in confined plasmas in tokamaks, through investigation of the influence of resonant helical fields on their equilibrium; With this aim, a superposition of the magnetic field of the plasma in static MHD equilibrium with the field associated with the resonances is considered, taking into account the toroidal geometry of the tokamak. Due to the lack of symmetry, the lines of the total magnetic field resulting from this superposition must form magnetic surfaces only around some regions of the plasma. using the averaging method, functions of approximate magnetic surfaces are obtained (analytically) around the regions of resonances of the plasma (they contain the lines of this total magnetic field). It was verified that these approximate surfaces have structures of magnetic islands. (author)
Energy Technology Data Exchange (ETDEWEB)
Chavez A, E.; Melendez L, L.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E
1991-07-15
The charged particles that constitute the plasma in the tokamaks are located in magnetic fields that determine its behavior. The poloidal magnetic field of the plasma current and the toroidal magnetic field of the tokamak possess relatively big gradients, which produce drifts on these particles. These drifts are largely the cause of the continuous lost of particles and of energy of the confinement region. In this work the results of numerical calculations of a modification to the 'traditional' toroidal magnetic field that one waits it diminishes the drifts by gradient and improve the confinement properties of the tokamaks. (Author)
Open-ended magnetic confinement systems for fusion
International Nuclear Information System (INIS)
Magnetic confinement systems that use externally generated magnetic fields can be divided topologically into two classes: ''closed'' and 'open''. The tokamak, the stellarator, and the reversed-field-pinch approaches are representatives of the first category, while mirror-based systems and their variants are of the second category. While the recent thrust of magnetic fusion research, with its emphasis on the tokamak, has been concentrated on closed geometry, there are significant reasons for the continued pursuit of research into open-ended systems. The paper discusses these reasons, reviews the history and the present status of open-ended systems, and suggests some future directions for the research
Measurement of magnetic fluctuations in the JET and TCA tokamaks
International Nuclear Information System (INIS)
The analysis of magnetic fluctuations in the JET and TCA tokamaks has been focused for this thesis on three subjects: i) magnetic turbulence and its correlation with the degradation of energy confinement ii) magnetic perturbation associated with the sawtooth iii) analysis of the magnetic coherent activity associated with stable locked-mode. The spatial structure of the turbulent magnetic activity has been investigated in JET and it is shown that the turbulent fluctuations are strongly correlated along the equilibrium magnetic field with k.Bo∼0. In TCA and JET, the level of magnetic fluctuations is observed to increase when the energy confinement time decreases. The analysis of a magnetic perturbation - the gong - appearing at the time of the sawtooth instability growth showed that the gong is in fact the magnetic signature of the instability itself. Different types of analysis are proposed which could improve our understanding of the sawtooth instability. The analysis of the coherent magnetic fluctuations allowed to deduce a toroidal plasma rotation and to estimate the radial ambipolar electric field. The results for TCA and JET are comparable with measurements performed in other tokamaks. It has been possible to show the existence of a new type of magnetic oscillations which is present during the stable phase of a locked-mode. This mode is resonant at the edge with n=1, m∼int(q(a)) and has been interpreted as an interchange mode destabilized by the new helical structure due to the locked-mode. (author) 93 figs., 4 tabs., 141 refs
Issues in tokamak/stellarator transport and confinement enhancement mechanisms
International Nuclear Information System (INIS)
At present, the mechanism for anomalous energy transport in low-β toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E x B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
International Nuclear Information System (INIS)
The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved
Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement
Energy Technology Data Exchange (ETDEWEB)
Furth, H.P.
1985-05-01
The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved.
On the scaling of magnetic plasma confinement under classical conditions
International Nuclear Information System (INIS)
Present magnetic confinement schemes based on tokamaks and similar devices are characterized by relatively large losses and low beta values. As a consequence, thermonuclear conditions can only be reached in such devices at large linear dimensions or by means of very strong magnetic fields, in combination with large heating powers. This does not rule out the possibility of realizing the same conditions on a smaller scale, i.e. by finding alternative schemes which provide classical and stable confinement of a pure plasma in a closed magnetic bottle. (author)
International Nuclear Information System (INIS)
High performance operation with Internal Transport Barrier (ITB) is effective to improve the core plasma confinement in the future fusion reactor. Numerous plasma experiments with ITB were confirmed in the reversed magnetic shear. It is considered that ITB formation could be controlled by external fueling. In this study, firstly, the feasibility of pellet injection condition is simulated in tokamak reactor. Secondly, the effect of the pellet injection on the core plasma profile and ITB formation is analyzed at tokamak and helical reactors. Simulations are carried out using the toroidal transport linkage code TOTAL. In case of the operation with pellet injection from high magnetic-field side (HFS), the feasibility of pellet injection condition for ITB formation is demonstrated in the ITER-like tokamak reactor, TR-1. In both tokamak and helical reactors, it is shown that pellet injection depth is not related to the position of ITB formation, but it has significant effect to the radial profile. In helical case, wide-ranged ITB is formed when the pellet is injected centrally. (author)
Microinstability-based model for anomalous thermal confinement in tokamaks
International Nuclear Information System (INIS)
This paper deals with the formulation of microinstability-based thermal transport coefficients (chi/sub j/) for the purpose of modelling anomalous energy confinement properties in tokamak plasmas. Attention is primarily focused on ohmically heated discharges and the associated anomalous electron thermal transport. An appropriate expression for chi/sub e/ is developed which is consistent with reasonable global constraints on the current and electron temperature profiles as well as with the key properties of the kinetic instabilities most likely to be present. Comparisons of confinement scaling trends predicted by this model with the empirical ohmic data base indicate quite favorable agreement. The subject of anomalous ion thermal transport and its implications for high density ohmic discharges and for auxiliary-heated plasmas is also addressed
Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field
Schaffer, Michael J.
1986-01-01
A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.
Some phenomena of improved impurity confinement in HT-6B tokamak
International Nuclear Information System (INIS)
The light impurity transport in HT-6B tokamak was studied by the investigation of the VUV line emissions and the visible line emissions from the impurity ions. The impurity confinement can be apparently changed with some special influence on the plasma. By the slow magnetic compression along the minor radius, the impurity diffusion coefficient was decreased from 2.5 x 104 cm2 s-1 to 1.8 x 104 cm2 s-1, the confinement time was increased and the impurity recycling flux from the edge was decreased. In other case, if we suppressed the MHD Mirnov turbulence with external resonant helical fields (RHF), the emission from OIII, CIII changed, the analysis appeared to conclude that the impurity confinement was also improved. (author). 3 refs, 8 figs
Magnetic well for plasma confinement
International Nuclear Information System (INIS)
A multipole magnetic well for plasma confinement includes a plurality of current-carrying coils placed on planes corresponding to the facets of a regular polyhedron that can be symmetrically circumscribed about a sphere. The direction of current in the coils is such as to minimize the flux density at the center of the polyhedron, thereby providing a confinement well with three-dimensional symmetry having an increasing flux density in all directions from the center. 16 claims, 18 figures
Low impurity concentrations and enhanced confinement in the Lithium Tokamak Experiment (LTX)
Boyle, D. P.; Bell, R. E.; Kaita, R.; Majeski, R.; Schmitt, J. C.; Scotti, F.; Biewer, T. M.; Gray, T. K.
2015-11-01
Significant improvements in confinement and overall performance have been shown in many devices using lithium wall-coatings, though impurities have often been an issue. Previous results with partial coatings in LTX, a modest-sized, ohmically-heated spherical tokamak, demonstrated energy confinement times exceeding ITER ELMy H-mode scalings. Here we report the results of new experiments with fully lithium coated walls, including first-ever successful operation of a tokamak plasma with a full liquid lithium wall. Energy confinement estimates based on magnetic analysis exceed the ITER98P scaling by 2-4x, and can now be confirmed with electron temperature and density profiles from Thomson scattering. Past attempts at a full liquid Li coating in LTX were unsuccessful, with difficulty achieving breakdown and short, cold, impurity dominated plasmas. Now, spectroscopic measurements in discharges with full liquid coatings indicate low core core impurity concentrations of Li, C, and O. The implications for impurity transport will be discussed. The results for confinement and impurity behavior with solid and liquid lithium on stainless steel surfaces in LTX are relevant to future devices and upgrades with all-metal walls, including NSTX-U. This work is supported by US DOE contracts DE-AC02-09CH11466 and DE- AC05-00OR22725.
THOR tokamak magnetic field system
International Nuclear Information System (INIS)
The THOR Machine is an iron cored Tokamak having a major radius of 0.52 m and a minor radius of 0.17 m giving an aspect ratio of 3:1. It has a low ripple toroidal field of 1 T and an iron core giving 0.24 Vs. The maximum plasma current is expected to be in the region of 80x103 A. The maximum toroidal field ripple on axis is of the order of 0.01% and 2.5% at the plasma edge. The equilibrium of the plasma is achieved by means of a D.C. vertical field and a 1 cm thick copper shell. The D.C. field is cancelled during the rise time of the plasma current by means of pulsed reverse vertical field windings placed between the copper shell and the vacuum vessel. The design of this field system represents a compromise between obtaining adequate field penetration through the relatively thin vacuum vessel and maintaining the mechanical strength necessary to withstand the transient magnetic forces. Energy for the toroidal field system is supplied by a 15 kV 600 kJ capacitor bank and for the ohmic heating and reverse vertical fields by 5 kV 25 kJ and 50 kJ banks respectively. The problems encountered in the design, development and manufacture of these field systems are discussed. (author)
Energy Technology Data Exchange (ETDEWEB)
Maget, P
1998-09-23
Pellet injection in the centre of tokamak plasmas can lead to an improved confinement regime called PEP (Pellet Enhanced Performance). The present work is dedicated to the mechanisms involved in the PEP regimes obtained in the tokamak Tore Supra. A neoclassical approach of transport shows that it is the anomalous transport, due to plasma turbulence, that causes the enhanced confinement. A linear model describing electrostatic instabilities has been developed in order to study the roles of density profile and current profile during the PEP, in the limit of large growth rates. The effect ofradial shear in flows is taken into account by removing the ExB shear flow rate from the linear growth rate, as suggested by non-linear numerical simulations of turbulence. A local transport coefficient is estimated from the knowledge of the linear growth rate and the mode width. We find that the peaked density profile in PEP regime lowers the diffusion coefficient, and that the velocity shear amplifies this effect. The evolution of the current profile is also stabilizing, but this parameter is not known with sufficient accuracy, so that its role in Tore Supra PEP experiments remains uncertain. (author)
High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.
Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J
2016-04-29
Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament. PMID:27176526
Tokamak with mechanical compression of toroidal magnetic field
Ohkawa, Tihiro
1981-01-01
A tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A collapsible toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. A toroidal magnetic field is developed within the toroidal space about the major axis thereof. A toroidal plasma is developed within the toroidal space about the major axis thereof. Pressure is applied to the liquid metal to collapse the liner and reduce the volume of the toroidal space, thereby increasing the toroidal magnetic flux density therein.
Fusion plasma theory grant: Task 1, Magnetic confinement fusion plasma theory
International Nuclear Information System (INIS)
The research performed under this grant during the current year has concentrated on key tokamak plasma confinement and heating theory issues: further development of neoclassical MHD; development of a new fluid/kinetic hybrid model; energy confinement degradation due to macroscopic phenomena in tokamaks; and some other topics (magnetics analysis, coherent structures, presheath structure). Progress and publications in these areas are briefly summarized in this report. 20 refs
Effect of density changes on tokamak plasma confinement
Spineanu, F
2015-01-01
A change of the particle density (by gas puff, pellets or impurity seeding) during the plasma discharge in tokamak produces a radial current and implicitly a torque and rotation that can modify the state of confinement. After ionization the newly born ions will evolve toward the periodic neoclassical orbits (trapped or circulating) but the first part of their excursion, which precedes the periodicity, is an effective radial current. It is short, spatially finite and unique for each new ion, but multiplied by the rate of ionization and it can produce a substantial total radial current. The associated torque induces rotation which modify the transport processes. We derive the magnitude of the radial current induced by ionization by three methods: the analysis of a simple physical picture, a numerical model and the neoclassical drift-kinetic treatment. The results of the three approaches are in agreement and show that the current can indeed be substantial. Many well known experimental observations can be reconsi...
Ongena, J.; Koch, R.; Wolf, R.; Zohm, H.
2016-05-01
Our modern society requires environmentally friendly solutions for energy production. Energy can be released not only from the fission of heavy nuclei but also from the fusion of light nuclei. Nuclear fusion is an important option for a clean and safe solution for our long-term energy needs. The extremely high temperatures required for the fusion reaction are routinely realized in several magnetic-fusion machines. Since the early 1990s, up to 16 MW of fusion power has been released in pulses of a few seconds, corresponding to a power multiplication close to break-even. Our understanding of the very complex behaviour of a magnetized plasma at temperatures between 150 and 200 million °C surrounded by cold walls has also advanced substantially. This steady progress has resulted in the construction of ITER, a fusion device with a planned fusion power output of 500 MW in pulses of 400 s. ITER should provide answers to remaining important questions on the integration of physics and technology, through a full-size demonstration of a tenfold power multiplication, and on nuclear safety aspects. Here we review the basic physics underlying magnetic fusion: past achievements, present efforts and the prospects for future production of electrical energy. We also discuss questions related to the safety, waste management and decommissioning of a future fusion power plant.
Physics of magnetic confinement fusion
Wagner F
2013-01-01
Fusion is the energy source of the universe. The local conditions in the core of the Sun allow the transfer of mass into energy, which is finally released in the form of radiation. Technical fusion melts deuterons and tritons to helium releasing large amounts of energy per fusion process. Because of the conditions for fusion, which will be deduced, the fusion fuel is in the plasma state. Here we report on the confinement of fusion plasmas by magnetic fields. Different confinement concepts — t...
Magnetic confinement of cosmic clouds
Azar, Michel; Thompson, W. B.
1988-01-01
The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple- and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as about 10 percent, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure 1/2 B-squared may decrease on leaving the cloud surface.
Distributed chaos and solitons at the edges of magnetically confined plasmas
Bershadskii, A
2016-01-01
It is shown, using results of measurements of ion saturation current in the plasma edges of different magnetic fusion confinement devices (tokamaks and stellarators), that the plasma dynamics in the edges is dominated by distributed chaos with spontaneously broken translational symmetry at low magnetic field, and with spontaneously broken reflexional symmetry (by helical solitons) at high magnetic field.
Influence of error fields on the plasma confining field and the plasma confinement in tokamak
International Nuclear Information System (INIS)
Influence of error fields on the plasma confining field and the plasma confinement is treated in the standpoint of design. In the initial breakdown phase before formation of the closed magnetic surfaces, the vertical field properly applied is the most important. Once the magnetic surfaces are formed, the non-axisymmetric error field is important. Effect of the shell gap associated with iron core and with pulsed vertical coils is thus studied. The formation of magnetic islands due to the external non-axisymmetric error field is studied with a simple model. A method of suppressing the islands by choosing the minor periodicity is proposed. (auth.)
International Nuclear Information System (INIS)
A collection of papers on plasma diagnostics is presented. The papers show the state of the art developments in a series of techniques: Magnetic diagnostics, Edge diagnostics, Langmuir probes, Spectroscopy, Microwave and FIR diagnostics as well as Thomson Scattering. Special interest was focused on those diagnostics oriented to fluctuations measurements in the plasma. (Author) 451 refs
Magnetic sensor for steady state tokamak
Energy Technology Data Exchange (ETDEWEB)
Neyatani, Yuzuru; Mori, Katsuharu; Oguri, Shigeru; Kikuchi, Mitsuru [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
1996-06-01
A new type of magnetic sensor has been developed for the measurement of steady state magnetic fields without DC-drift such as integration circuit. The electromagnetic force induced to the current which leads to the sensor was used for the measurement. For the high frequency component which exceeds higher than the vibration frequency of sensor, pick-up coil was used through the high pass filter. From the results using tokamak discharges, this sensor can measure the magnetic field in the tokamak discharge. During {approx}2 hours measurement, no DC drift was observed. The sensor can respond {approx}10ms of fast change of magnetic field during disruptions. We confirm the extension of measured range to control the current which leads to the sensor. (author).
International Nuclear Information System (INIS)
Recent results from confinement scaling experiments on tokamaks with ohmic and strong auxiliary heating are reviewed. An attempt is made to draw these results together into a low-density ohmic confinement scaling law, and a scaling law for confinement with auxiliary heating. The auxiliary heating confinement law may also serve to explain the saturation in tau/sub E/ vs anti n/sub e/ observed in some ohmic heating density scaling experiments
Global energy confinement scaling for neutral-beam-heated tokamaks
International Nuclear Information System (INIS)
A total of 677 representative discharges from seven neutral-beam-heated tokamaks has been used to study the parametric scaling of global energy confinement time. Contributions to this data base were from ASDEX, DITE, D-III, ISX-B, PDX, PLT, and TFR, and were taken from results of gettered, L-mode type discharges. Assuming a power law dependence of tau/sub E/ on discharge parameters kappa, I/sub p/, B/sub t/, anti n/sub e/ P/sub tot/, a, and R/a, standard multiple linear regression techniques were used in two steps to determine the scaling. The results indicate that the discharges used in the study are well described by the scaling tau/sub E/ α kappa/sup 0.28/ B/sub T//sup -0.09/ I/sub p//sup 1.24/anti n/sub e//sup -0.26/ P/sub tot//sup -0.58/ a/sup 1.16/ (R/a)/sup 1.65/
Global energy confinement scaling for neural-beam-heated tokamaks
International Nuclear Information System (INIS)
A total of 677 representative discharges from seven neutral-beam-heated tokamaks have been used to study the parametric scaling of global energy confinement time. Contributions to this data base were from Asdex, DITE, D-III, ISX-B, PDX, PLT and TFR, and were taken from results of gettered, L-mode type discharges. Assuming a power law dependence of tausub(E) on the discharge parameters kappa, Isub(p), Bsub(t), n-barsub(e)Psub(tot), a and R, standard multiple linear regression techniques were used in two steps to determine the scaling. The results indicate that the discharges used in the study are well described by the scaling tausub(E) is proportional to kappasup(0.28)Bsub(T)sup(-0.09)Isub(p)sup(1.24)n-barsub(e)sup(0.26) Psub(tot)sup(-0.58)asup(-0.49)Rsup(1.65). (author)
Improved confinement with reversed magnetic shear in TFTR
International Nuclear Information System (INIS)
Highly peaked density and pressure profiles in a new operating regime have been observed on the Tokamak Fusion Test Reactor (TFTR). The q-profile has a region of reversed magnetic shear extending from the magnetic axis to r/a ∼0.3-0.4. The central electron density rises from 0.45 x 1020 m-3 to nearly 1.2 x 1020 m-3 during neutral beam injection. The electron particle diffusivity drops precipitously in the plasma core with the onset of the improved confinement mode and can be reduced by a factor of ∼50 to near the neoclassical particle diffusivity level
Review of compact, alternate concepts for magnetic confinement fusion
International Nuclear Information System (INIS)
This report documents a study of compact alternate magnetic confinement fusion experiments and conceptual reactor designs. The purpose of this study is to identify those devices with a potential to burn tritium in the near future. The bulk of the report is made up of a review of the following compact alternates: compact toroids, high power density tokamaks, linear magnetic systems, compact mirrors, reversed field pinches and some miscellaneous concepts. Bumpy toruses and stellarators were initially reviewed but were not pursued since no compact variations were found. Several of the concepts show promise of either burning tritium or evolving into tritium burning devices by the early 1990's: RIGGATRON, Ignitor, OHTE, Frascati Tokamak upgrade, several driven (low or negative net power) mirror experiments and several Reversed Field Pinch experiments that may begin operation around 1990. Of the above only the Frascati Tokamak Upgrade has had funds allocated. Also identified in this report are groups who may have tritium burning experiments in the mid to late 1990's. There is a discussion of the differences between the reviewed devices and the mainline tokamak experiments. This discussion forms the basis of recommendations for R and D aimed at the compact alternates and the applicability of the present CFFTP program to the needs of the compact alternates. These recommendations will be presented in a subsequent report
Influence of rotating resonant magnetic perturbations on particle confinement
International Nuclear Information System (INIS)
The effect of resonant magnetic perturbations (RMPs) on particle confinement is studied in J-TEXT tokamak by using externally applied rotating RMPs. It is found that RMPs cause improved (degraded) particle confinement when its frequency is higher (lower) than the natural m/n = 2/1 tearing mode frequency, and the amount of change in electron density is proportional to the difference between these two frequencies, where m and n are the poloidal and toroidal mode number, respectively. These results reveal the important role of the relative rotation between RMPs and the electron fluid in affecting the particle confinement. The experimental results are compared to numerical ones based on nonlinear two-fluid equations, and quantitative agreement is found. (letter)
Magnetic confinement fusion energy research
Energy Technology Data Exchange (ETDEWEB)
Grad, H
1977-03-01
Controlled Thermonuclear Fusion offers probably the only relatively clean energy solution with completely inexhaustible fuel and unlimited power capacity. The scientific and technological problem consists in magnetically confining a hot, dense plasma (pressure several to hundreds of atmospheres, temperature 10/sup 8/ degrees or more) for an appreciable fraction of a second. The scientific and mathematical problem is to describe the behavior, such as confinement, stability, flow, compression, heating, energy transfer and diffusion of this medium in the presence of electromagnetic fields just as we now can for air or steam. Some of the extant theory consists of applications, routine or ingenious, of known mathematical structures in the theory of differential equations and in traditional analysis. Other applications of known mathematical structures offer surprises and new insights: the coordination between sub-supersonic and elliptic-hyperbolic is fractured; supersonic propagation goes upstream; etc. Other completely nonstandard mathematical structures with significant theory are being rapidly uncovered (and somewhat less rapidly understood) such as non-elliptic variational equations and new types of weak solutions. It is these new mathematical structures which one should expect to supply the foundation for the next generation's pure mathematics, if history is a guide. Despite the substantial effort over a period of some twenty years, there are still basic and important scintific and mathematical discoveries to be made, lying just beneath the surface.
Magnetic confinement fusion energy research
International Nuclear Information System (INIS)
Controlled Thermonuclear Fusion offers probably the only relatively clean energy solution with completely inexhaustible fuel and unlimited power capacity. The scientific and technological problem consists in magnetically confining a hot, dense plasma (pressure several to hundreds of atmospheres, temperature 108 degrees or more) for an appreciable fraction of a second. The scientific and mathematical problem is to describe the behavior, such as confinement, stability, flow, compression, heating, energy transfer and diffusion of this medium in the presence of electromagnetic fields just as we now can for air or steam. Some of the extant theory consists of applications, routine or ingenious, of known mathematical structures in the theory of differential equations and in traditional analysis. Other applications of known mathematical structures offer surprises and new insights: the coordination between sub-supersonic and elliptic-hyperbolic is fractured; supersonic propagation goes upstream; etc. Other completely nonstandard mathematical structures with significant theory are being rapidly uncovered (and somewhat less rapidly understood) such as non-elliptic variational equations and new types of weak solutions. It is these new mathematical structures which one should expect to supply the foundation for the next generation's pure mathematics, if history is a guide. Despite the substantial effort over a period of some twenty years, there are still basic and important scintific and mathematical discoveries to be made, lying just beneath the surface
International Nuclear Information System (INIS)
Radial electric field shear and poloidal plasma rotation are important factors affecting transport and confinement in tokamaks. Alteration of the electric field and plasma rotation in the vicinity of magnetic islands is also an important factor in tokamak plasma confinement. In the STOR-M tokamak, fast (∼1 ms) simultaneous alterations of the radial electric field, plasma rotation (Mparallel = 0-0.4 in the plasma current direction), floating potential fluctuations in the periphery and MHD activity generated by rotating islands have been observed experimentally during normal ohmic discharges. The observed time and magnitude of the changes depend on the average electron density and poloidal beta at the beginning of the discharge. In discharges with high initial poloidal beta these changes are accompanied by a reduction in Hα emission and an increase in the line averaged density. Drastic decreases in Hα and increases in line averaged electron density and estimation of poloidal beta suggest that STOR-M confinement is significantly affected in ohmic discharges without an external additional energy input or biasing. MHD activity in STOR-M is damped when a negative electric field is observed at the limiter region of the plasma edge. MHD frequency is observed to decrease with the negative electric field
Study of plasma rotation in Tokamak confinement. Progress report, June 1, 1997--February 28, 1998
International Nuclear Information System (INIS)
This proposal is a collaborative project between Prairie View A ampersand M University and Princeton University. The proposed tasks have been established based on close collaboration between two institutions. We studied the tasks in two aspects: analytical theory of drift current in tokamak plasmas, and computer simulation of non-neutral plasma. Some preliminary results have been presented in the 1997 APS Division of Plasma Physics Meeting, Pittsburgh. Titles of the presentations were open-quotes Magnetic Moment of Bounce Motion in Tokamak Plasmaclose quotes and open-quotes Numerical Simulation of Plasma Confinement in a Non-neutral Plasmaclose quotes. The papers for publication are in preparation. In the coming year, we will further develop the analytic theory and simulation studies. The studies will be focused on understanding of edge electric field in TFTR experiments, and attention will be paid to the effect of the a particles resulting from DT fusion reactions. In addition, in order to establish a stronger fusion plasma research and education base at Prairie View A ampersand M University, we plan to expand our current theoretical project into a coupled theoretical/experimental project. With the help of Oak Ridge National Lab we plan to build a plasma physics laboratory equipped with a small mirror machine. For the second year budget of this proposal, including the funds for the previously proposed theoretical and the newly planned experimental tasks, we request a $245,000 grant. A budget plan and its justification are included in this report
International Nuclear Information System (INIS)
The hypothesis that the heating beam fueling profile shape connects the edge condition and improved core confinement and fusion reactivity is extensively studied on TFTR and applied to other tokamaks. The derived absolute scalings based on beam fueling profile shape for the stored energy and neutron yield can be applied to the deuterium discharges at different major radii in TFTR. These include Supershot, High poloidal beta, L-mode, and discharges with a reversed shear (RS) magnetic configuration. These scalings are also applied to deuterium-tritium discharges. The role of plasma parameters, such as plasma current, Isdo2(p), edge safety factor, qsdo5(a), and toroidal field, Bsdo2(T), in the performance and stability of the discharges is explicitly studied. Based on practical and externally controllable plasma parameters, the limitation and optimization of fusion power production of the present TFTR is investigated and a path for a discharge condition with fusion power gain, Q > 1 is suggested based on this study. Similar physics interpretation is provided for beam heated discharges on other major tokamaks
International Nuclear Information System (INIS)
The Fusion Research Center (FRC) at the University Texas will operate the tokamak TEXT-U and its associated systems for experimental research in basic plasma physics. While the tokamak is not innovative, the research program, diagnostics and planned experiments are. The fusion community will reap the benefits of the success in completing the upgrades (auxiliary heating, divertor, diagnostics, wall conditioning), developing diverted discharges in both double and single null configurations, exploring improved confinement regimes including a limiter H-mode, and developing unique, critical turbulence diagnostics. With these new regimes, the authors are poised to perform the sort of turbulence and transport studies for which the TEXT group has distinguished itself and for which the upgrade was intended. TEXT-U is also a facility for collaborators to perform innovative experiments and develop diagnostics before transferring them to larger machines. The general philosophy is that the understanding of plasma physics must be part of any intelligent fusion program, and that basic experimental research is the most important part of any such program. The emphasis of the proposed research is to provide well-documented plasmas which will be used to suggest and evaluate theories, to explore control techniques, to develop advanced diagnostics and analysis techniques, and to extend current drive techniques. Up to 1 MW of electron cyclotron heating (ECH) will be used not only for heating but as a localized, perturbative tool. Areas of proposed research are: (1) core turbulence and transport; (2) edge turbulence and transport; (3) turbulence analysis; (4) improved confinement; (5) ECH physics; (6) Alfven wave current drive; and (7) diagnostic development
International Nuclear Information System (INIS)
The effect of isotope on confinement in high-recycling, L-mode plasmas is studied on the Tokamak Fusion Test Reactor (TFTR) [see D. M. Meade, J. Fusion Energy 7, 107 (1988)] by comparing hydrogen and deuterium plasmas with the same magnetic field and similar electron densities and heating power, with both Ohmic and deuterium-neutral-beam heating. Following a long operational period in deuterium, nominally hydrogen plasmas were created through hydrogen glow discharge and hydrogen gas puffing in Ohmic plasmas, which saturated the exposed limiter surface with hydrogen and raised the H/(H+D) ratio from 10±3% to 65±5%. Ohmic deuterium discharges obtained higher stored energy and lower loop voltage than hydrogen discharges with similar limiter conditions. Neutral-beam power scans were conducted in L-mode plasmas at minor radii of 50 and 80 cm, with plasma currents of 0.7 and 1.4 MA. To minimize transport differences from the beam deposition profile and beam heating, deuterium neutral beams were used to heat the plasmas of both isotopes. Total stored energy increased approximately 20% from nominally hydrogen plasmas to deuterium plasmas during auxiliary heating. Of this increase about half can be attributed to purely classical differences in the energy content of unthermalized beam ions. Kinetic measurements indicate a consistent but small increase in central electron temperature and total stored electron energy in deuterium relative to hydrogen plasmas, but no change in total ion stored energy. No significant differences in particle transport, momentum transport, and sawtooth behavior are observed. Overall, only a small improvement (∼10%) in global energy confinement time of the thermal plasma is seen between operation in hydrogen and deuterium. copyright 1996 American Institute of Physics
About the Toroidal Magnetic Field of a Tokamak Burning Plasma Experiment with Superconducting Coils
International Nuclear Information System (INIS)
In tokamaks, the strong dependence on the toroidal magnetic field of both plasma pressure and energy confinement is what makes possible the construction of small and relatively inexpensive burning plasma experiments using high-field resistive coils. On the other hand, the toroidal magnetic field of tokamaks using superconducting coils is limited by the critical field of superconductivity. In this article, we examine the relative merit of raising the magnetic field of a tokamak plasma by increasing its aspect ratio at a constant value of the peak field in the toroidal magnet. Taking ITER-FEAT as an example, we find that it is possible to reach thermonuclear ignition using an aspect ratio of approximately 4.5 and a toroidal magnetic field of 7.3 T. Under these conditions, fusion power density and neutron wall loading are the same as in ITER [International Thermonuclear Experimental Reactor], but the normalized plasma beta is substantially smaller. Furthermore, such a tokamak would be able to reach an energy gain of approximately 15 even with the deterioration in plasma confinement that is known to occur near the density limit where ITER is forced to operate
L-mode confinement model based on transport-MHD theory in tokamaks
International Nuclear Information System (INIS)
Theory of the L-mode confinement in tokamaks is developed based on the microscopic ballooning instability which is destabilized by the plasma transport below the critical pressure gradient against the ideal MHD instability. The destabilization by the current-diffusivity and the stabilization by the thermal transport and ion viscosity, are analyzed. The least stable mode determines the anomalous transport coefficients. The formula of the thermal transport coefficient is derived, which explains major experimental observations on the L-mode confinement. (author)
Czech Academy of Sciences Publication Activity Database
Van Oost, G.; Bulanin, V.V.; Donné, A.J.H.; Gusakov, E.Z.; Krämer-Flecken, A.; Krupnik, L.I.; Melnikov, A.; Peleman, P.; Razumova, K.; Stöckel, Jan; Vershkov, V.; Altukov, A.B.; Andreev, V.F.; Askinazi, L.G.; Bondarenko, I.S.; Dnestrovskij, A.Yu.; Eliseev, L.G.; Esipov, L.A.; Grashin, S.A.; Gurchenko, A.D.; Hogeweij, G.M.D.; Jachmin, S.; Khrebtov, S.M.; Kouprienko, D.V.; Lysenko, S.E.; Perfilov, S.V.; Petrov, A.V.; Popov, A.Yu.; Reiser, D.; Soldatov, S.; Stepanov, A.Yu.; Telesca, G.; Urazbaev, A.O.; Verdoolaege, G.; Zimmermann, O.
2006-01-01
Roč. 12, č. 6 (2006), s. 14-19. ISSN 1562-6016. [International Conference on Plasma Physics and Technology/11th./. Alushta, 11.9.2006-16.9.2006] Institutional research plan: CEZ:AV0Z20430508 Keywords : tokamak * plasma * improved confinement * turbulence Subject RIV: BL - Plasma and Gas Discharge Physics http://vant.kipt.kharkov.ua/TABFRAME.html
Visualization of Magnetically Confined Plasmas
International Nuclear Information System (INIS)
With the rapid developments in experimental and theoretical fusion energy research towards more geometric details, visualization plays an increasingly important role. In this paper we will give an overview of how visualization can be used to compare and contrast some different configurations for future fusion reactors. Specifically we will focus on the stellarator and tokamak concepts. In order to gain understanding of the underlying fundamental differences and similarities these two competing concepts are compared and contrasted by visualizing some key attributes
Magnetic flux reconstruction methods for shaped tokamaks
International Nuclear Information System (INIS)
The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p' and FF' functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green's function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green's functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising
Magnetic flux reconstruction methods for shaped tokamaks
Energy Technology Data Exchange (ETDEWEB)
Tsui, Chi-Wa
1993-12-01
The use of a variational method permits the Grad-Shafranov (GS) equation to be solved by reducing the problem of solving the 2D non-linear partial differential equation to the problem of minimizing a function of several variables. This high speed algorithm approximately solves the GS equation given a parameterization of the plasma boundary and the current profile (p` and FF` functions). The author treats the current profile parameters as unknowns. The goal is to reconstruct the internal magnetic flux surfaces of a tokamak plasma and the toroidal current density profile from the external magnetic measurements. This is a classic problem of inverse equilibrium determination. The current profile parameters can be evaluated by several different matching procedures. Matching of magnetic flux and field at the probe locations using the Biot-Savart law and magnetic Green`s function provides a robust method of magnetic reconstruction. The matching of poloidal magnetic field on the plasma surface provides a unique method of identifying the plasma current profile. However, the power of this method is greatly compromised by the experimental errors of the magnetic signals. The Casing Principle provides a very fast way to evaluate the plasma contribution to the magnetic signals. It has the potential of being a fast matching method. The performance of this method is hindered by the accuracy of the poloidal magnetic field computed from the equilibrium solver. A flux reconstruction package has been implemented which integrates a vacuum field solver using a filament model for the plasma, a multi-layer perception neural network as an interface, and the volume integration of plasma current density using Green`s functions as a matching method for the current profile parameters. The flux reconstruction package is applied to compare with the ASEQ and EFIT data. The results are promising.
Aspects of Tokamak toroidal magnet protection
International Nuclear Information System (INIS)
Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The ofly potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting torgidal magnets. It is found that the two general classificatigls of protectign methods are thermal and electrical. Computer programs were developed which aldow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed
Aspects of Tokamak toroidal magnet protection
Energy Technology Data Exchange (ETDEWEB)
Green, R.W.; Kazimi, M.S.
1979-07-01
Simple but conservative geometric models are used to estimate the potential for damage to a Tokamak reactor inner wall and blanket due to a toroidal magnet field collapse. The only potential hazard found to exist is due to the MHD pressure rise in a lithium blanket. A survey is made of proposed protection methods for superconducting toroidal magnets. It is found that the two general classifications of protection methods are thermal and electrical. Computer programs were developed which allow the toroidal magnet set to be modeled as a set of circular filaments. A simple thermal model of the conductor was used which allows heat transfer to the magnet structure and which includes the effect of temperature dependent properties. To be effective in large magnets an electrical protection system should remove at least 50% of the stored energy in the protection circuit assuming that all of the superconductor in the circuit quenches when the circuit is activated. A protection system design procedure based on this criterion was developed.
Review of energy confinement and local transport scaling results in neutral-beam-heated tokamaks
International Nuclear Information System (INIS)
Over the past several years, tokamak neutral beam injection experiments have evolved from the brute force study of the effects of global discharge characteristics (I/sub p/, anti n/sub e/, P/sub heat/, etc.) on energy confinement to the appreciation that there are effects more subtle, yet controllable, that may influence confinement dramatically. While this evolution from first to second generation experiments is derived from an empirical understanding of low and high energy confinement modes and how to achieve them operationally, the underlying physics is still unknown. Several theories with different physical bases appear to describe the global scaling of the low confinement mode discharges quite well. On the other hand, little agreement has been found between theoretical and experimentally deduced values of local transport coefficients. While it is known operationally how to achieve any one of several types of high confinement mode discharges, here too, the underlying physics of the transport associated with these modes is poorly understood
Murari, A.; Peluso, E.; Gelfusa, M.; Lupelli, I.; Gaudio, P.
2015-07-01
The extrapolation of the energy confinement time to the next generation of devices has been investigated both theoretically and experimentally for several decades in the tokamak community. Various scaling expressions have been proposed using dimensional and dimensionless quantities. They are all based on the assumption that the scalings are in power law form. In this paper, an innovative methodology is proposed to extract the scaling expressions for the energy confinement time in tokamaks directly from experimental databases, without any previous assumption about the mathematical form of the scalings. The approach to obtain the scaling expressions is based on genetic programming and symbolic regression. These techniques have been applied to the ITPA database of H-mode discharges and the results have been validated with a series of established statistical tools. The soundest results, using dimensional variables, are not in the form of power laws but contain a multiplicative saturation term. Also the scalings, expressed in terms of the traditional dimensionless quantities, are not in power law form and contain additive saturation terms. The extrapolation to ITER of both dimensional and dimensionless quantities indicate that the saturation effects are quite significant and could imply a non-negligible reduction in the confinement time to be expected in the next generation of devices. The results obtained with the proposed techniques therefore motivate a systematic revisiting of the scaling expressions for plasma confinement in tokamaks.
Low-Zsub(eff) plasma confinement in TFR 600 tokamak
International Nuclear Information System (INIS)
TFR 600 is a tokamak which has mainly been devoted so far to one goal: the study of stable discharges at high plasma densities average value of n approximately >7x1013cm-3 for Isub(p)=200kA, Bsub(T)=40kG. In this case, Zsub(eff) is close to one, the ions contribute to the energy balance and seem to behave non-neoclassically. By polluting the vacuum chamber, it has been possible to reproduce TRF-400-type discharges, dominated by the electrons and impurity ions (Zsub(eff) approximately 5). The MHD activity investigated is characterized by a high-level m=3 tearing mode and by the evidence of a minor disruption during the overlap of m=3, m=2 modes. (author)
Statistical analysis of the global energy confinement time in ohmic discharges in the ASDEX tokamak
International Nuclear Information System (INIS)
In ohmic discharges in all tokamaks at low plasma densities the global energy confinement time, τE, increases almost linearly with the density (LOC, linear ohmic confinement). In tokamaks with sufficiently large dimensions, τE saturates at a critical density (ASDEX bar ne- ≅ 3 x 1019 m-3) and is nearly constant at higher densities (SOC, saturated ohmic confinement). In the same density region some experiments report a further confinement regime for deuterium discharges in which τE exceeds the saturated value and is further increased (IOC, improved ohmic confinement). There the global energy confinement time roughly behaves as in the LOC regime. For both the LOC and the SOC regimes an isotope effect, i.e. the dependence of τ on the ion mass, is reported as an additional aspect of the ohmic energy confinement. A statistical analysis is performed to identify the parameters which are responsible for the properties of the energy confinement in these discharges in ASDEX. In contrast to earlier reports on confinement time scalings in ASDEX OH, only discharges with a full experimental description of kinetic electron and ion parameters, i.e. profiles of densities, temperatures and Zeff, are used to evaluate the energy contents of both species. By means of statistics it is shown that the characteristics of τE are mainly caused by the behaviour of the electron energy flux and the ohmic input power. The ion energy flux, does not play a significant role. Furthermore, the IOC regime is explained as a continuation of the low-density LOC regime. Both the isotope effect and the density dependence of τE are caused by features of the electron energy transport. (Author)
Institute of Scientific and Technical Information of China (English)
毛剑珊; 罗家融; P.Phillips; 赵君煜; 揭银先; 吴振伟; 胡立群; 李建刚
2002-01-01
The phenomena of improved ohmic confinement have been observed during the modulation of the toroidal curranton the Hefei superconducting Tokamak-7 (HT-7). In the experiment, the programming ohmic heating field wasmodulated. A toroidal frequency-modulated current induced by modulated loop voltage was added on the plasmaequilibrium current. The ratio of ac amplitude of the plasma current to the main plasma current is about 12-30%.These improved plasma confinement phenomena include the facts that the average electron density and the centralelectron temperature both increase, the Dα radiation from the edge is reduced, the magnetohydrodynamics isobviously suppressed by oscillating plasma current, eand the global energy confinement time increases by 27-45%o.It is found that the faster the modulation is, the more effective the improved ohmic confinement phase.
Magnetic properties of confined electron gas
International Nuclear Information System (INIS)
The effects of confinement by a two or three-dimensional harmonic potential on the magnetic properties of a free electron gas are investigated using the grand-canonical ensemble framework. At high temperatures an extension of Darwin's, Felderhof and Raval's works is made taking into account spin effects at low temperature. A comprehensive description of the magnetic properties of a free electron gas is given. The system is regarded as finite, but the boundary condition psi=0 is not introduced. The limits of weak and strong confinement are also analysed
Magnet design approach for pulsed tokamak reactors
International Nuclear Information System (INIS)
A choice of various operating modes of a tokamak reactor will have considerable impact on the fatigue lives and cost of ohmic heating (OH), equilibrium field (EF), and toroidal field (TF) coils. OH and EF coil requirements and their costs, as well as the effects of the fringing fields of the EF coils on the TF coils, have been studied under cyclic operation in the range of N = 102 to 106 cycles, spanning the range from a noninductively driven reactor (STARFIRE) to a conventional ohmically driven reactor. For a reference design of TF coils the design of the central OH solenoid has been studied as a function of its maximum field, B /SUP OH/. Increasing requirements for structural support lead to only negligible increases in voltseconds for B /SUP OH/greater than or equal to 10.0 T. Fatigue failure of the OH coil is not a concern for N less than or equal to 105; for N about 106 fatigue limits the strain to small values, resulting in small increases in structural requirements and modest decreases in volt-seconds. Should noninductive current drive be achievable the authors note that this not only eliminates the OH coil, but it also permits EF coil placement in the inboard region, which facilitates the creation of highly shaped plasma cross sections (large triangularity, or bean-shaped equilibria). They have computed the stored energy, coil configuration and fringing fields for a number of EF coil design options. For pulsed operation these EF coil fields result in three major problems. First, the induced eddy currents introduce additional heating to the TF magnets, which increases cryogenic demands compared to steady-state operation. Second, of greater concern, these EF coils impart out-of-plane forces and turning moments to the TF coil structure. In this case fatigue failure is a severe design constraint. Finally, pulsed operation of the EF coils requires large, expensive power supplies
Investigation of high energy runaway electron confinement in the Oak Ridge tokamak
International Nuclear Information System (INIS)
High energy runaway electrons in the Oak Ridge tokamak ORMAK have been investigated through measurement of the bremsstrahlung produced when these electrons leave the discharge and strike the limiting aperture of the torus. The experimental results have been interpreted in terms of a classical single-particle model appropriate for collisionless particles in a tokamak, and it has been found that most of the confinement properties of high energy runaways in ORMAK can be understood on this basis. An experiment designed to directly test this model has disclosed an anomalous transport which has been described by a runaway diffusion coefficient D approximately 102 to 104 cm2/sec appropriate for runaways near the outside of the plasma. A discussion of the possible mechanisms for this anomalous transport is given
Investigation of high energy runaway electron confinement in the Oak Ridge tokamak
Energy Technology Data Exchange (ETDEWEB)
Zweben, S. J.
1977-11-01
High energy runaway electrons in the Oak Ridge tokamak ORMAK have been investigated through measurement of the bremsstrahlung produced when these electrons leave the discharge and strike the limiting aperture of the torus. The experimental results have been interpreted in terms of a classical single-particle model appropriate for collisionless particles in a tokamak, and it has been found that most of the confinement properties of high energy runaways in ORMAK can be understood on this basis. An experiment designed to directly test this model has disclosed an anomalous transport which has been described by a runaway diffusion coefficient D approximately 10/sup 2/ to 10/sup 4/ cm/sup 2//sec appropriate for runaways near the outside of the plasma. A discussion of the possible mechanisms for this anomalous transport is given.
Economic evaluation of fissile fuel production using resistive magnet tokamaks
International Nuclear Information System (INIS)
The application of resistive magnet tokamaks to fissile fuel production has been studied. Resistive magnets offer potential advantages over superconducting magnets in terms of robustness, less technology development required and possibility of demountable joints. Optimization studies within conservatively specified constraints for a compact machine result in a major radius of 3.81 m and 618 MW fusion power and a blanket space envelope of 0.35 m inboard and 0.75 m outboard. This machine is called the Resistive magnet Tokamak Fusion Breeder (RTFB). A computer code was developed to estimate the cost of the resistive magnet tokamak breeder. This code scales from STARFIRE values where appropriate and calculates costs of other systems directly. The estimated cost of the RTFB is $3.01 B in 1984 dollars. The cost of electricity on the same basis as STARFIRE is 42.4 mills/kWhre vs 44.9 mills/kWhre for STARFIRE (this does not include the fuel value or fuel cycle costs for the RTFB). The breakeven cost of U3O8 is $150/lb when compared to a PWR on the once through uranium fuel cycle with no inflation and escalation. On the same basis, the breakeven cost for superconducting tokamak and tandem mirror fusion breeders is $160/lb and $175/lb. Thus, the RTFB appears to be competitive in breakeven U3O8 cost with superconducting magnet fusion breeders and offers the potential advantages of resistive magnet technology
Influence of magnetic field ripple on plasma rotation in tokamaks
International Nuclear Information System (INIS)
The problem of plasma rotation in tokamaks with injection is considered. It is shown that the experimental results obtained in the PLT and ISX-B tokamaks can be explained by the presence of the magnetic-field ripple, provided that localized particles exist. The analysis carried out is based on the general expression for the magnetic-field ripple. This expression, which is derived in the present paper, describes the ripple distribution over the plasma cross-section for both the ordinary case and the case of shunted or damaged coils. (author)
Magnetic confinement and the Linde problem
Simonov, Yu A
2016-01-01
Perturbation theory of thermodynamic potentials in QCD at $T>T_c$ is considered with the nonperturbative background vacuum taken into account. It is shown that the magnetic confinement in the QCD vacuum prevents the infrared catastrophe of the perturbation theory present in the case of the free vacuum (the "Linde problem"). A short discussion is given of the applicability of the nonperturbative formalism at large $T$ and of the relation with the HTL theory.
Role of runaway electrons in LHCD regimes with improved confinement on the CASTOR tokamak
Energy Technology Data Exchange (ETDEWEB)
Voitsekhovich, I. [Kurchatov Institute, Moscow (Russian Federation); Stoeckel, J.; Zacek, F. [Akademie Ved Ceske Republiky, Prague (Czech Republic). Ustav Fyziky Plazmatu
1993-12-31
Lower hybrid current drive (LHCD) experiments in low density plasmas on ASDEX, CASTOR, WT-3, VERSATOR and HT-6B tokamaks demonstrated an improvement of the particle confinement at moderate lower hybrid powers (P{sub LH}). Moreover, the experiments have shown that a reduction of edge electrostatic fluctuations is probably responsible for this effect. However, the mechanism behind the reduction of fluctuations has remained unclear. Here we try to explain the reduction of fluctuations by enhanced population and non-ambipolar losses of runaway electrons with LHCD. (author) 8 refs., 3 figs.
Design of Magnetic Measurement System on SUNIST Spherical Tokamak
Institute of Scientific and Technical Information of China (English)
ZENG Long; LIU Jun; WANG Ping; ZHANG Lu; HE Yexi; GAO Zhe; WANG Wenhao; XIE Lifeng; TAN Yi; ZHANG Liang; XIE Huiqiao; PENG Lili
2008-01-01
A magnetic measurement system consisting of magnetic probes and flux loops for spherical tokamak SUNIST,is uniquely designed due to the strongly shaped plasma cross section and the narrow space near the central solenoid.Plasma equilibrium reconstruction with the current filament method is performed to determine the number and positions of the magnetic probes and flux loops,as well as their design precision required.
A Steady State Tokamak Operation by Use of Magnetic Monopoles
Narihara, K.
1991-01-01
A steady state tokamak operation based on a magnetic monopole circuit is considered. Circulation of a chain of iron cubes which trap magnetic monopoles generates the needed loop voltage. The monopole circuit is enclosed by a series of solenoid coils in which the magnetic field is feedback controlled so that the force on the circuit balance against the mechanical friction. The driving power is supplied through the current sources of poloidal, ohmic and solenoid coils. The current drive efficie...
Magnetic properties of confined holographic QCD
International Nuclear Information System (INIS)
We investigate the Sakai-Sugimoto model at nonzero baryon chemical potential in a background magnetic field in the confined phase where chiral symmetry is broken. The D8-brane Chern-Simons term holographically encodes the axial anomaly and generates a gradient of the η' meson, which carries a non-vanishing baryon charge. Above a critical value of the chemical potential, there is a second-order phase transition to a mixed phase which includes also ordinary baryonic matter. However, at fixed baryon charge density, the matter is purely η'-gradient above a critical magnetic field
Distinct turbulence sources and confinement features in the spherical tokamak plasma regime
Energy Technology Data Exchange (ETDEWEB)
Wang, W. X. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Ethier, S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Ren, Y. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Kaye, S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Chen, J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Startsev, E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Lu, Z. [Univ. of California, San Diego, CA (United States). La Jolla, CA
2015-10-30
New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong ExB shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offering one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. This predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.
Volpe, F A; La Haye, R J; Lanctot, M J; Lohr, J; Prater, R; Strait, E J; Welander, A
2015-01-01
Non-rotating (`locked') magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimetre waves. The applied fields were used to control the phase of locking and so align the island O-point with the region where the injected waves generated non-inductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement and high pressure, in accordance with the expected dependencies upon wave power and relative phase between O-point and driven current.
Volpe, F A; Hyatt, A; La Haye, R J; Lanctot, M J; Lohr, J; Prater, R; Strait, E J; Welander, A
2015-10-23
Nonrotating ("locked") magnetic islands often lead to complete losses of confinement in tokamak plasmas, called major disruptions. Here locked islands were suppressed for the first time, by a combination of applied three-dimensional magnetic fields and injected millimeter waves. The applied fields were used to control the phase of locking and so align the island O point with the region where the injected waves generated noninductive currents. This resulted in stabilization of the locked island, disruption avoidance, recovery of high confinement, and high pressure, in accordance with the expected dependencies upon wave power and relative phase between the O point and driven current. PMID:26551119
Energy confinement and transport of H-mode plasmas in tokamak
International Nuclear Information System (INIS)
A characteristic feature of the high-confinement (H-mode) regime is the formation of a transport barrier near the plasma edge, where steepening of the density and temperature gradients is observed. The H-mode is expected to be a standard operation mode in a next-step fusion experimental reactor, called ITER-the International Thermonuclear Experimental Reactor. However, energy confinement in the H-mode has been observed to degrade with increasing density. This is a critical constraint for the operation domain in the ITER. Investigation of the main cause of confinement degradation is an urgent issue in the ITER Physics Research and Development Activity. A key element for solving this problem is investigation of the energy confinement and transport properties of H-mode plasmas. However, the influence of the plasma boundary characterized by the transport barrier in H-modes on the energy transport of the plasma core has not been examined sufficiently in tokamak research. The aim of this study is therefore to investigate the energy confinement properties of H-modes in a variety of density, plasma shape, seed impurity concentration, and conductive heat flux in the plasma core using the experimental results obtained in the JT-60U tokamak of Japan Atomic Energy Research Institute. Comparison of the H-mode confinement properties with those of other tokamaks using an international multi-machine database for extrapolation to the next step device was also one of the main subjects in this study. Density dependence of the energy confinement properties has been examined systematically by separating the thermal stored energy into the H-mode pedestal component determined by MHD stability called the Edge Localized Modes (ELMs) and the core component governed by gyro-Bohm-like transport. It has been found that the pedestal pressure imposed by the destabilization of ELM activities led to a reduction in the pedestal temperature with increasing density. The core temperature for each
Physical accuracy estimate of global energy confinement scaling laws for tokamaks
International Nuclear Information System (INIS)
A reliability estimate for the derived relationships is one of the most important problems in the analysis of data on global energy confinement in tokamaks. At present the problem of accuracy estimation for the scaling laws obtained on the basis of a statistical analysis of experimental data on global fact that the energy confinement in tokamaks actually depends on a greater number of parameters than the set P, B, Ip, k, R, a, n, M usually used in the statistical analysis. An additional difficulty emerges due to the fact that we don't know theoretical laws of τE dependence on experimental parameters. By these two reasons a difference between the experimental τE and any scaling law expression for τfitE is not a random quantity. Under the conditions, when τE-τfitE is not a random quantity with a zero average magnitude, the standard methods of statistical analysis turn out to be unapplicable. Unsatisfaction of this condition in practice results in a great sensitivity of statistical treatment results to the chosen set of experimental information. As a result, using somewhat different subsets of the total data base, essentially - different scaling laws have been produced. In this case, even the scaling laws of the same functional type the dependences on the experimental parameters P, B, Ip, k, R, a, n, M differ by values noticeably-exceeding the error bars for the dependences. (author) 4 refs., 3 figs., 1 tab
Runaway acceleration during magnetic reconnection in tokamaks
International Nuclear Information System (INIS)
In this paper, the basic theory of runaway electron production is reviewed and recent progress is discussed. The mechanisms of primary and secondary generation of runaway electrons are described and their dynamics during a tokamak disruption is analysed, both in a simple analytical model and through numerical Monte Carlo simulation. A simple criterion for when these mechanisms generate a significant runaway current is derived, and the first self-consistent simulations of the electron kinetics in a tokamak disruption are presented. Radial cross-field diffusion is shown to inhibit runaway avalanches, as indicated in recent experiments on JET and JT-60U. Finally, the physics of relativistic post-disruption runaway electrons is discussed, in particular their slowing down due to emission of synchrotron radiation, and their ability to produce electron-positron pairs in collisions with bulk plasma ions and electrons
Tokamak Plasmas : Internal magnetic ﬁeld measurement in tokamak plasmas using a Zeeman polarimeter
Indian Academy of Sciences (India)
M Jagadeeshwari; J Govindarajan
2000-11-01
In a tokamak plasma, the poloidal magnetic ﬁeld proﬁle closely depends on the current density proﬁle. We can deduce the internal magnetic ﬁeld from the analysis of circular polarization of the spectral lines emitted by the plasma. The theory of the measurement and a detailed design of the Zeeman polarimeter constructed to measure the poloidal ﬁeld proﬁle in the ADITYA tokamak are presented. The Fabry-Perot which we have employed in our design, with photodiode arrays followed by lock-in detection of the polarization signal, allows the measurement of the fractional circular polarization. In this system He-II line with wavelength 4686 Å is adopted as the monitoring spectral line. The line emission used in the present measurement is not well localized in the plasma, necessiating the use of a spatial inversion procedure to obtain the local values of the ﬁeld.
Some theoretical problems of magnetic diagnostics in tokamaks and stellarators
International Nuclear Information System (INIS)
The main problem of magnetic diagnostics is discussed here: which plasma characteristics can be determined from magnetic measurements in tokamaks and stellarators. The reasons are elucidated why diamagnetic measurements are reliable and easily interpreted. We discuss also the capabilities of diagnostics based on the measurements of poloidal fields outside the plasma. This article is based on a lecture delivered at the Third International School on Plasma Physics and Controlled Fusion, held 15-22 June 1993 at St. Petersburg - Kizhi, Russia. (author)
Optimization of magnetic perturbation spectra for the COMPASS tokamak
Czech Academy of Sciences Publication Activity Database
Cahyna, Pavel
Geneva : International Atomic Energy Agency, 2008. s. 247-247. ISBN N. [IAEA Fusion Energy Conference/22nd./. 13.10.2008-18.10.2008, Geneva] Institutional research plan: CEZ:AV0Z20430508 Keywords : resonant magnetic perturbations * ELM control * magnetic islands * saddle coils * COMPASS tokamak Subject RIV: BL - Plasma and Gas Discharge Physics http://www-pub.iaea.org/MTCD/Meetings/PDFplus/2008/cn165/cn165_BookOfAbstracts.pdf
International Nuclear Information System (INIS)
The lithium tokamak experiment (LTX) is a modest-sized spherical tokamak (R0=0.4 m and a=0.26 m) designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 deg. C. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.
International Nuclear Information System (INIS)
The lithium tokamak experiment (LTX) is a modest-sized spherical tokamak (R0 = 0.4 m and a = 0.26 m) designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 C. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.
Energy Technology Data Exchange (ETDEWEB)
Kaita, R.; Kozub, T.; Logan, N.; Majeski, R.; Menard, J.; Zakharov, L.
2010-12-10
The lithium tokamak experiment LTX is a modest-sized spherical tokamak R0=0.4 m and a =0.26 m designed to investigate the low-recycling lithium wall operating regime for magnetically confined plasmas. LTX will reach this regime through a lithium-coated shell internal to the vacuum vessel, conformal to the plasma last-closed-flux surface, and heated to 300-400 oC. This structure is highly conductive and not axisymmetric. The three-dimensional nature of the shell causes the eddy currents and magnetic fields to be three-dimensional as well. In order to analyze the plasma equilibrium in the presence of three-dimensional eddy currents, an extensive array of unique magnetic diagnostics has been implemented. Sensors are designed to survive high temperatures and incidental contact with lithium and provide data on toroidal asymmetries as well as full coverage of the poloidal cross-section. The magnetic array has been utilized to determine the effects of nonaxisymmetric eddy currents and to model the start-up phase of LTX. Measurements from the magnetic array, coupled with two-dimensional field component modeling, have allowed a suitable field null and initial plasma current to be produced. For full magnetic reconstructions, a three-dimensional electromagnetic model of the vacuum vessel and shell is under development.
Superconducting magnets and cryogenics for the steady state superconducting tokamak SST-1
International Nuclear Information System (INIS)
SST-1 is a steady state superconducting tokamak for studying the physics of the plasma processes in tokamak under steady state conditions and to learn technologies related to the steady state operation of the tokamak. SST-1 will have superconducting magnets made from NbTi based conductors operating at 4.5 K temperature. The design of the superconducting magnets and the cryogenic system of SST-1 tokamak are described. (author)
Laser diagnostics of magnetically confined thermonuclear plasmas
International Nuclear Information System (INIS)
Lasers in the vacuum ultraviolet (approx. 1200 A) through the far-infrared (approx. 1.2 mm) portion of the spectrum have found increasing application in the nonperturbing measurement of the properties of magnetically confined fusion plasmas. In addition to their nonperturbing nature, lasers permit the measurement of such parameters as electron-density and temperature with both high spatial temporal resolution. The purpose of the present article is to review the current state of laser plasma diagnostics as well as to project future needs and developments. Considerable emphasis is placed on the technology. The topics covered include: interferometry and polarimetry, Thomson scattering, laser fluorescent spectroscopy, and laser enhanced Zeeman polarimetry. (Auth.)
Microwave Reflectometry for Magnetically Confined Plasmas
Energy Technology Data Exchange (ETDEWEB)
Mazzucato, E.
1998-02-01
This paper is about microwave reflectometry -- a radar technique for plasma density measurements using the reflection of electromagnetic waves by a plasma cutoff. Both the theoretical foundations of reflectometry and its practical application to the study of magnetically confined plasmas are reviewed in this paper. In particular, the role of short-scale density fluctuations is discussed at length, both as a unique diagnostic tool for turbulence studies in thermonuclear plasmas and for the deleterious effects that fluctuations may have on the measurement of the average plasma density with microwave reflectometry.
Equilibrium and stability MHD in the magnetic confinement for thermonuclear fusion
International Nuclear Information System (INIS)
A survey of the mayor systems for magnetic confinement of plasmas is made. The basic concepts are reviewed briefly. The equilibrium and stability conditions for open systems (mirrors, magnetic wells, Z and Theta-pinches), for toroidal axisymmetric (Z-Pinch, Screw-Pinch, Belt-Pinch and Tokamak) and toroidal non-axisymmetric systems (High-β Stellarator and low-β Theta-Pinch) are discussed. A comparative analysis between the diferent systems is made. In the conclusions, the author's opinions about future developments in the field are included. (author)
Tokamak D-T neutron source models for different plasma physics confinement modes
Energy Technology Data Exchange (ETDEWEB)
Fausser, Clement, E-mail: clement.fausser@cea.fr [CEA, DEN, Saclay, DANS/DM2S/SERMA, F-91191 Gif-sur-Yvette (France); Puma, Antonella Li; Gabriel, Franck [CEA, DEN, Saclay, DANS/DM2S/SERMA, F-91191 Gif-sur-Yvette (France); Villari, Rosaria [Associazione EURATOM-ENEA sulla Fusione, Via Enrico Fermi 45, 00044 Frascati, Rome (Italy)
2012-08-15
Highlights: Black-Right-Pointing-Pointer HCLL DEMO neutronics is based on plasma physics L-mode, but may use H or A mode. Black-Right-Pointing-Pointer Based on Plasma Physics 0D code, H and A-mode D-T neutron sources formulae are proposed. Black-Right-Pointing-Pointer TRANSGEN code is built to create 2D source maps as input for Monte-Carlo codes. Black-Right-Pointing-Pointer A-mode neutronic impact is compared to L-mode at same power on a HCLL DEMO design. Black-Right-Pointing-Pointer Results show TBR and Me slight changes, contrary to NWL profile: from -22% to +11%. - Abstract: Neutronic studies of European demonstration fusion power plant (DEMO) have been so far based on plasma physics low confinement mode (L-mode). Future tokamaks, nevertheless, may likely use alternative confinement modes such as high or advanced confinement modes (H and A-mode). Based on analytical formulae used in plasma physics, H and A-modes D-T neutron sources formulae are proposed in this paper. For that purpose, a tokamak random neutron source generator, TRANSGEN, has been built generating bidimensional (radial and poloidal) neutron source maps to be used as input for neutronics Monte-Carlo codes (TRIPOLI-4 and MCNP5). The impact of such a source on the neutronic behavior of the European DEMO-2007 Helium-cooled lithium-lead reactor concept has been assessed and compared with previous results obtained using a L-mode neutron source. An A-mode neutron source map from TRANSGEN has been used with the code TRIPOLI-4. Assuming the same fusion power, results show that main reactor global neutronic parameters, e.g. tritium breeding ratio and neutron multiplication factor, evolved slightly when compared to present uncertainties margin. However, local parameters, such as the neutron wall loading (NWL), change significantly compared to L-mode shape: from -22% to +11% for NWL.
Recent progress towards steady state tokamak operation with improved confinement in JT-60U
Energy Technology Data Exchange (ETDEWEB)
Fujita, Takaaki [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment
2000-07-01
In the JT-60U tokamak, optimization of high {beta}{sub p} mode and reversed shear mode plasmas are being done for establishment of scientific basis for steady state operation of tokamaks. In high {beta}{sub p} H-mode plasmas, {beta}{sub N}=2.9 and H{sub 89}=2.2-2.4 were sustained sanitarily by using high triangularity configuration and pressure profile optimization. Steady state performance was limited by resistive low toroidal mode number instabilities. Stabilization of resistive modes by using a newly installed ECRF system was attempted and a decrease of mode amplitude was observed but complete stabilization could not be achieved. In reversed shear plasmas, high fusion performance with equivalent DT fusion power gain of 0.5 was sustained for 0.8 s or an energy confinement time. The duration was limited by disruptive beta collapse that was encountered when the minimum value of q became 2 even with moderate beta, {beta}{sub N} {approx}1.2. Stationary sustainment of ITB was demonstrated in a full CD reversed shear plasma with LHCD. The sustainment of reversed shear current profile by bootstrap current was demonstrated in an ELMy H-mode edge reversed shear plasma with a high triangularity in a high q regime. A confinement enhancement factor of 3.5 and {beta}{sub N} of 2 were sustained for 2.7 s with stationary current and pressure profiles. Ar puffing to H mode plasmas aiming at high confinement with high density and high radiation fraction was performed and H{sub 89}{approx}1.4 with radiation fraction of 80% was obtained at 70% of Greenwald density. (author)
Decomposition into eigenmodes: a novel approach to characterize plasma confinement in a tokamak
International Nuclear Information System (INIS)
A novel method of perturbation analysis has been developed to characterize particle and energy confinement in a tokamak plasma. Whereas the classical approach to confinement begins with an empirical model using transport coefficients, the present work uses eigenmodes to represent the dynamic response. The latter approach has been applied to density perturbations induced in the TCA tokamak by pellet injection. The observed dynamic response can be entirely reproduced by a set of three eigenmodes, thereby reducing the temporal evolution of the density to three time constants only. The scatter of these time constants allows the density to evolve on quite different time-scales, with the relaxation of the density profile being determined by the nature of the eigenmodes. Whilst a τ∼I2-3pnoe dependence is observed in the time constants, the eigenfunctions remain insensitive to plasma conditions. The density invariance is linked with a strong linearity in the dynamic response, indicating that the pellet has no significant impact on transport processes. The eigenmode representation is particularly well suited to the study of coupled variables. A coupling has been identified between density perturbations and another variable which is very likely to be the electron temperature. The strength of this coupling does not depend on plasma conditions, although it varies with the level of MHD activity. High levels of activity change the interaction between particle and heat fluxes without affecting the eigenmodes. This results in an unfavourable weighting of the eigenmodes which accelerates the density relaxation and thereby explains the observed confinement degradation. (author) 42 figs., 45 refs
Microwave Tokamak Experiment: Overview and status
International Nuclear Information System (INIS)
The Microwave Tokamak Experiment, now under construction at the Laboratory, will use microwave heating from a free-electron laser. The intense microwave pulses will be injected into the tokamak to realize several goals, including a demonstration of the effects of localized heat deposition within magnetically confined plasma, a better understanding of energy confinement in tokamaks, and use of the new free-electron laser technology for plasma heating. 3 figs., 3 tabs
Spectral confinement and current for atoms in strong magnetic fields
DEFF Research Database (Denmark)
Fournais, Søren
2007-01-01
e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B<3......e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B<3...
Dynamic effects of rotating helical magnetic field on tokamak edge
International Nuclear Information System (INIS)
Penetration processes of rotating helical magnetic perturbation (RHMP) into tokamak plasmas have been studied on a small tokamak device HYBTOK-II for dynamic ergodic divertor experiment preparing in TEXTOR. The penetration of RHMP has been discussed by using the measurements of RHMP in the plasma based on the growth of magnetic islands (i.e. tearing mode). In the case of the low Doppler-shifted frequency observed from the plasma, the amplification of RHMP in the plasma due to the spatial modification of plasma current has been found. A large Doppler-shifted frequency produces an expected attenuation of RHMP near the resonance surface due to flowing of screening current. A decrease of the amplification of RHMP originated from the suppression of the growth of magnetic islands has been also found by plasma current oscillation. (author)
Instrumentation for magnetically confined fusion plasma diagnostics
International Nuclear Information System (INIS)
Recent progress in magnetically confined plasma research has brought the goal of controlled thermonuclear fusion within reach. Simultaneously, the increased size, temperature, and density of these devices has resulted in rapid changes in diagnostic techniques. In this article, recent developments in instrumentation are reviewed together with trends for the future. The topics discussed include far-infrared laser interferometry and polarimetry, ruby laser television Thomson scattering, excimer and Nd-glass laser scattering, ion temperature determination via large-α scattering with FIR and CO2 lasers, collective scattering, Schottky diode mixer technology, synchrotron radiation diagnostics and imaging, ion beam probes, x-ray diagnostics and imaging, neutron diagnostics, resonance fluorescence scattering, ultraviolet diagnostics, and internal magnetic field measurement
Spin Dynamics in Confined Magnetic Structures III
Hillebrands, Burkard
2006-01-01
This third volume of Spin Dynamics in Confined Magnetic Structures addresses central aspects of spin-dynamic phenomena, including recent new developments, on a tutorial level. Researchers will find a comprehensive compilation of the current work in the field. Introductory chapters help newcomers to understand the basic concepts. The more advanced chapters give the current state of the art of spin dynamic issues ranging from the femtosecond to the microsecond regime. This volume concentrates on new experimental techniques such as ferromagnetic-resonance-force microscopy and two-photon photoemission, as well as on aspects of precessional switching, spin-wave excitation, vortex dynamics, spin relaxation, domain-wall dynamics in nanowires and their applications to magnetic logic devices. An important chapter is devoted to the presently very hot subject of the spin-transfer torque, combining the physics of electronic transport and micromagnetics. The comprehensive presentation of these developments makes this volu...
First Results of Movable Limiter Experiments and its Effects on the IR-T1 Tokamak Plasma Confinement
International Nuclear Information System (INIS)
Tokamak limiter plays a number of roles in its operation. It serves primarily to protect the wall from the plasma when there are disruptions, runaway electrons, or other instabilities. For this reason it is commonly made of a refractory material, such as carbon, molybdenum or tungsten, capable of withstanding high heat loads. Secondly, the limiter localizes the plasma-surface interaction. The high power and particle density at the limiter surface causes rapid removal of adsorbed gas, oxide layers and other easily desorbed impurities. When only the clean substrate remains it is possible to maintain plasmas with lower impurity levels. Plasma-surface interaction in tokamaks is important in plasma conditions such as impurities, plasma parameters, and plasma confinement. Thirdly, the limiter localizes the particle recycling. A higher neutral density and more radiation are observed in the region near the limiter, than at other positions around the torus . Movable limiter was designed, constructed, and has been used on IR-T1 tokamak to investigate the possibility of modifying the plasma confinement. In this research work we present the first results of a movable limiter experiments and its effects on the tokamak plasma confinement. For this purpose we firstly designed, constructed, and installed a movable localized poloidal limiter, and then measured the effects of limiter position on the time intervals of plasma parameters such as: plasma density, temperature, and energy confinement time. The results compared in different movable limiter positions and discussed. (author)
A probabilistic methodology for the design of radiological confinement of tokamak reactors
International Nuclear Information System (INIS)
A methodology using probabilistic risk assessment techniques is proposed for evaluating the design of multiple confinement barriers for a fusion plant within the context of a limited allowable risk. The methodology was applied to the reference design of the International Thermonuclear Experimental Reactor (ITER). Accident sequence models were developed to determine the probability of radioactive releases from each confinement barrier. The current ITER design requirements, that set environmental radioactive release limits for individual event sequences grouped in categories by frequency, is extended to derive a limit on the plant overall risk. This avoids detailed accounting for event uncertainties in both frequency and consequence. Thus, an analytical form for a limit line is derived as a complementary cumulative frequency of permissible radioactive releases to the environment. The line can be derived using risk aversion of the designer's own choice. By comparing the releases from each confinement barrier against this limit line, a decision can be made about the number of barriers required to comply with the design requirements. A decision model using multi-attribute utility function theory was constructed to help the designer in choosing the type of the tokamak building while considering preferences for attributes such as construction cost, project completion time, technical feasibility and public attitude. Sensitivity analysis on some of the relevant parameters in the model was performed
Hu, J S; Sun, Z; Guo, H Y; Li, J G; Wan, B N; Wang, H Q; Ding, S Y; Xu, G S; Liang, Y F; Mansfield, D K; Maingi, R; Zou, X L; Wang, L; Ren, J; Zuo, G Z; Zhang, L; Duan, Y M; Shi, T H; Hu, L Q
2015-02-01
A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development. PMID:25699449
Energy Technology Data Exchange (ETDEWEB)
Wang, W. X. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Ethier, S. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Ren, Y. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Kaye, S. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Chen, J. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Startsev, E. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA; Lu, Z. [University of California, San Diego, La Jolla, California 92093, USA; Li, Z. Q. [Zhejiang University, Hangzhou, People' s Republic of China
2015-10-01
Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around k(theta)rho(s) similar to 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Moreover, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport
Radiation control in fusion plasmas by magnetic confinement
International Nuclear Information System (INIS)
The present work addresses two important issues for the industrial use of fusion: plasma radiation control, as a part of the more general power handling issue, and high density tokamak operation. These two issues will be most critical in the demonstration reactor, called DEMO, intermediate step between ITER and a future commercial reactor. For DEMO, the need to radiate a large fraction of the power so as to limit the peak power load on the divertor will be a key constraint. High confinement will have to be combined with high radiated power fraction, and the required level of plasma purity. The main achievement of this thesis is to have shown experimental evidence of the existence of a stable plasma regime meeting the most critical requirements of a DEMO scenario: an electron density up to 40% above the Greenwald value, together with a fraction of radiated power close to 80%, with a good energy confinement and limited dilution. The plasma is additionally heated with ion cyclotron waves in a central electron heating scenario, featuring alpha particle heating. The original observations reported in this work bring highly valuable new pieces of information both to the physics of the tokamak edge layer and to the construction of an 'integrated operational scenario' required to successfully operate fusion devices. In the way for getting high density plasmas, the new observations involve the following topics. First, the formation of a poloidal asymmetry in the edge electron density profile, with a maximum density located close to toroidal pumped limiter. This asymmetry occurs inside the separatrix, with a constant plasma pressure on magnetic surfaces. Secondly, a correlative decrease of the electron temperature in the same edge region. Thirdly, the excellent coupling capabilities of the ICRH waves, up to a central line averaged electron density of 1.4 times the Greenwald density. Fourthly, a poloidally asymmetric edge radiation region, providing the dissipation of 80% of
Some aspects on alternative lines of magnetic confinement
International Nuclear Information System (INIS)
Facing the year 2000, some proposals for a balanced strategy of fusion research are given in this paper. Fusion research by the world community has made substantial progress, and it is now possible to build an experimental test reactor based on the tokamak confinement principle, in the form of a global commitment such as the ITER/NET project. Nevertheless further investigations are needed before the practical use of fusion energy becomes a reality. With regard to this, and to the time gap formed by the planning and construction period of ITER/NET, continued activities have to take place at the national laboratories, to preserve the quality of plasma physical research and the competence of fusion scientists and engineers, as well as to guarantee research on alternative lines aiming at an improved reactor concept. Some aspects are given in this context on the desired properties of an optimal fusion reactor, including a high plasma beta value, a minimized imposed toroidal magnetic field, controlled or non-existent disruptions, steady-state operation, minimized plasma-wall interaction, and the absence both of a stabilizing conducting wall and of active feedback systems. (au)
International Nuclear Information System (INIS)
One of the scientific success stories of fusion research over the past decade is the development of the ExB shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high)-mode to VH (very high)-mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with ExB velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of ExB shear on the growth, radial extent and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number ways to change the radial electric field Er. An important theme in this area is the synergistic effect of ExB velocity shear and magnetic shear. Although the ExB velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of ExB velocity shear and facilitate turbulence stabilization
Magnetic confinement of the solar tachocline: The oblique dipole
Antoine, Strugarek; Jean-Paul, Zahn
2011-01-01
3D MHD global solar simulations coupling the turbulent convective zone and the radiative zone have been carried out. Essential features of the Sun such as differential rotation, meridional circulation and internal waves excitation are recovered. These realistic models are used to test the possibility of having the solar tachocline confined by a primordial inner magnetic field. We find that the initially confined magnetic fields we consider open into the convective envelope. Angular momentum is transported across the two zones by magnetic torques and stresses, establishing the so-called Ferarro's law of isorotation. In the parameter space studied, the confinement of the magnetic field by meridional circulation penetration fails, also implying the failure of the tachocline confinement by the magnetic field. Three-dimensional convective motions are proven responsible for the lack of magnetic field confinement. Those results are robust for the different magnetic field topologies considered, i.e. aligned or obliqu...
Measurement of the internal magnetic field structure of tokamak plasmas
International Nuclear Information System (INIS)
The first part of this article deals with the physical fundaments and technical aspects of this polarimetric measuring method, with its diagnostic capability, but also with its limitations. The second part summarizes the essential experimental results and their feedback on the theoretical description of Tokamak plasmas, which caused a revision of the accepted ideas of the magnetic field structure and its magnetohydrodynamic stability, in particular in the area of the hot plasma core. (orig.)
Progress in application of high temperature superconductor in tokamak magnets
Czech Academy of Sciences Publication Activity Database
Gryaznevich, M.; Svoboda, V.; Stöckel, Jan; Sykes, A.; Sykes, N.; Kingham, D.; Hammond, G.; Apte, P.; Todd, T.N.; Ball, S.; Chappell, S.; Melhem, D.; Ďuran, Ivan; Kovařík, Karel; Grover, O.; Markovič, T.; Odstrčil, M.; Odstrčil, T.; Šindlery, A.; Vondrášek, G.; Kocman, J.; Lilley, M.K.; de Grouchy, P.; Kim, H.-T.
2013-01-01
Roč. 88, 9-10 (2013), s. 1593-1596. ISSN 0920-3796. [Symposium on Fusion Technology (SOFT-27)/27./. Liège, 24.09.2012-28.09.2012] Institutional support: RVO:61389021 Keywords : tokamaks * HTS * magnets Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.149, year: 2013 http://www.sciencedirect.com/science/ article /pii/S0920379613001117#
Viscosity and confinement in magnetized plasma
Johnson, Robert W
2007-01-01
An alternative to the Braginskii decomposition is proposed, one rooted in treating the viscosity as a scalar quantity in a coordinate-free representation. With appropriate application to the rate-of-shear tensor, one may solve the neoclassical force density equations for its undetermined velocity dependence, as well as the radial and poloidal profiles mentioned in [R. W. Johnson, Phys. Plasmas, under review], using an improved poloidal expansion. The pseudoplastic behavior of magnetized plasma is again obtained, and the high viscosity solution is determined to be physical. A clear relationship between confinement mode and viscosity is observed, indicating a physical origin for transport barriers, pedestals, and other phenomena. The gyroviscous contribution is found to be an effect on the order of one one-thousandth of one percent of the dominant collisional viscosity.
International Nuclear Information System (INIS)
Disruption is one of the most critical issues in tokamaks. A resonance magnetic perturbation (RMP) coil system will be installed in future tokamaks such as the International Thermonuclear Experimental Reactor to mitigate edge localized modes. In this study, the effect of RMP on tokamak disruption was investigated using the small tokamak device HYBTOK-II. It was found statistically that an externally applied RMP leads to faster current quench during disruption. (author)
Helium transport in enhanced confinement regimes on the TEXTOR and DIII-D tokamaks
International Nuclear Information System (INIS)
Comparisons of helium (He) transport and exhaust in L-mode and in an enhanced confinement regime (H-mode), which is induced by a polarizing electrode, have been made for the TEXTOR tokamak. The results show an increased tendency for He accumulation when bulk plasma energy and particle confinement are improved during the polarization induced H-mode. Since these results imply that a high He pumping efficiency may be necessary for H-mode burning plasmas, we have begun exploring He transport in a divertor H-mode, similar to that proposed for International Thermonuclear Experimental Reactor (ITER). A collaborative program has been initiated to measure He transport and scaling on DIII-D during L-mode, H-mode, and ELMing H-mode plasma conditions. To simulate the presence of He ash in DIII-D, a 25 ms He puff is injected into a DIII-D plasma resulting in a He concentration of ∼5%. The time dependence of the He2+ density profiles in the plasma core is measured by charge-exchange recombination spectroscopy at 11 radial locations
International Nuclear Information System (INIS)
These proceedings of the IAEA-sponsored meeting held in Nice, France 10-11 October, 1988, contain the manuscripts of the 21 reports dealing with research using small tokamaks. The purpose of this meeting was to highlight some of the achievements of small tokamaks and alternative magnetic confinement concepts and assess the suitability of starting new programs, particularly in developing countries. Papers presented were either review papers, or were detailed descriptions of particular experiments or concepts. Refs, figs and tabs
Controlling tokamak geometry with three-dimensional magnetic perturbations
International Nuclear Information System (INIS)
It is shown that small externally applied magnetic perturbations can significantly alter important geometric properties of magnetic flux surfaces in tokamaks. Through 3D shaping, experimentally relevant perturbation levels are large enough to influence turbulent transport and MHD stability in the pedestal region. It is shown that the dominant pitch-resonant flux surface deformations are primarily induced by non-resonant 3D fields, particularly in the presence of significant axisymmetric shaping. The spectral content of the applied 3D field can be used to control these effects
Motion of Charged Particles in Perturbed Magnetic Fields of Tokamak
Czech Academy of Sciences Publication Activity Database
Papřok, R.; Krlín, Ladislav; Cahyna, Pavel; Riccardo, V.
Vol. 2. Prague: MATFYZPRESS, Prague, 2009 - (Šafránková, J.; Pavlů, J.), s. 139-143 ISBN 978-80-7378-102-6. [Annual conference of doctoral students - WDS 2009 /18./. Prague (CZ), 02.06.2009-05.06.2009] Institutional research plan: CEZ:AV0Z20430508 Keywords : resonant magnetic perturbations * magnetic islands * electric field * runaway electrons * tokamak Subject RIV: BL - Plasma and Gas Discharge Physics http://www.mff.cuni.cz/veda/konference/wds/contents/pdf09/WDS09_223_f2_Paprok.pdf
Stability of magnetic modes in tokamaks
International Nuclear Information System (INIS)
A theoretical study is carried out concerning two experimental topics: stabilization, by a suprathermal population, of the mode ''m=1, n=1'' which induces the sawtooth effect (modelling the role of suprathermal particles in the stabilization); stability, in the non linear regime, of the magnetic islands involved in magnetic turbulence problems (micro-tearing) and in disruption phenomena (tearing), and the effects of diamagnetism, excitation threshold and saturation levels. 45 figs., 97 refs
Magnet systems for ''Bean-Shaped'' tokamak
International Nuclear Information System (INIS)
Bean-shaping of tokamak plasmas offers a method of reaching stable operation at (beta) > 10%. In order to establish the indentation of the ''bean'', a set of high- current ''pushing coils'' (> 5 MA in a reactor) must be located at the midplane as close as possible to the inboard edge of the plasma. If located in the bore of the TF coils, then maintenance of the pushing coils may be impossible, and the interlocking coils may prevent reactor modularity. If located outside, the required pushing-coil current may be unacceptably large. This dilemma is overcome with a unique TF coil design in which the inboard leg is bent outward in the form of an arc. The pushing coils are housed in the midplane indentation of this arc, just outside the TF coils but adequately close to the plasma. The arched coil transfers forces to the top and bottom legs, where it can be reacted by a clamp structure if necessary. This technique would allow demountable joints to be placed near the inoard leg (for copper TF coils). Another design approach to the pushing coils is to use liquid Li or Na as the conductor and coolant. The liquid metal ''coils'' can be placed immediately adjacent to the plasma, giving optimal control of the plasma shape with minimal coil current, although modularity of the reactor may have to be surrendered. Conceptual designs are presented of PF and TF coil systems for an ignition test reactor with about 14% and for a full-scale demonstration reactor with about 20%, both using copper TF coils
Steady state tokamak equilibrium with specified magnetic axis and two magnetic null points
International Nuclear Information System (INIS)
An analysis method of tokamak plasma equilibrium by a relaxation method with specified magnetic axis and null points (two magnetic separatrix points) is developed. The six degrees of freedom due to designated positions of the magnetic axis and null points is possible by using six poloidal field coil currents. Stable steady state tokamak plasma equilibria are calculated along with the MHD (magnetohydrodynamic) potential energy. Assuming an RF heating plasma, the plasma generates a plasma current which partially or fully cancels the magnetic field from the poloidal field coils. For low-temperature plasmas, the plasma current distribution is centrally peaked; for high-temperature plasmas, the plasma current has a hole. A centrally peaked current distribution in a low-temperature plasma is evolved into a current distribution with a hole by increasing the plasma pressure by heating. These calculations show that, under sufficient heating, the pressure driven current in tokamak plasmas form a current hole which minimizes the MHD potential energy. (author)
Upgrading of the Magnetic Confinement Plasma Device KT-5E
Institute of Scientific and Technical Information of China (English)
何迎花; 余羿; 闻一之; 刘万东; 李定; 俞昌旋; 谢锦林; 李弘; 兰涛; 王昊宇
2012-01-01
In this article we present ideas of providing appropriate poloidal magnetic field for helimaks to help to generate toroidal magnetic plasma torus. Placing a conductive ring in the center of the cross-section to induce a suitable current, we change the helical magnetic field lines in the helimak discharge into magnetic surface. In this kind of discharge, the plasma density is greatly increased, and the corresponding density fluctuation is significantly decreased, showing a better confinement by magnetic shear. It allows more flexible and efficient experimental investigations on the toroidal magnetic confinement plasmas to be carried on in this kind of device.
High Energy Electron Confinement in a Magnetic Cusp Configuration
Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni
2014-01-01
We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configur...
Rapid further heating of tokamak plasma by fast-rising magnetic pulse
International Nuclear Information System (INIS)
The object of the experiment was to study the rapid further heating of a tokamak plasma and its influence on confinement. For this purpose, a high-voltage theta-pinch pulse was applied to a tokamak plasma and production of a high-temperature (keV) plasma was ensured within a microsecond. The magnetic pulse is applied at the plasma current maximum parallel or antiparallel to the study toroidal field. In either case, the pulsed field quickly penetrates the plasma and the plasma resistivity estimated from the penetration time is about 100 times larger than the classical. A burst of energetic neutrals of approximately 1 μs duration was observed and the energy distribution had two components of the order of 1 keV and 0.1 keV in the antiparallel case. Doppler broadening measurement shows heating of ions to a temperature higher than 200 eV; however, the line profile is not always Maxwellian distribution. The X-rays disappear at the moment of applying the magnetic pulse and reappear about 100 μs later with an intensive burst, while both energy levels are the same (approximately 100 keV). (author)
Ignition of a magnetically confined D-T plasma
International Nuclear Information System (INIS)
This study extends Lawson's analysis on the ignition criteria for a magnetically confined plasma by introducing conduction losses from heat transfer theory rather than through the 3nkT/τE term (k = Boltzmann constant, T = temperature, τE = energy confinement time). It is found that ignition depends on the strength of the magnetic field that confines the plasma, but it is independent of the plasma particle density. As a consequence, an increase of reaction energy through higher particle density leads to higher conduction losses, which can be offset only by higher magnetic fields. It is found that a magnetically confined plasma cannot reach ignition with a magnetic fields considered in present normal size machines. (author)
International Nuclear Information System (INIS)
Full text: We present a study that deals with meandering curves which arise after the reconnection process (or overlap) of resonances (1), that occurs only in non-twist discrete maps (2). Meandering curves formed by this kind of process play the role of barriers for chaotic transport in phase space, because inside the meandering region there is a special torus, called shearless torus, known as the strongest torus in a dynamical system (1). We introduce an extra perturbation in the Standard Non-twist Map (3), and we call this new map Labyrinthic Standard Non-twist Map (4). The labyrinthic map proposed in this work shows multiple reconnection processes of resonances, presenting multiple barriers for chaotic transport. Having applications in important areas such as the physics of thermonuclear plasmas confined in tokamaks for the extraction of clean energy. (1) D. del-Castillo-Negrete, J. M. Greene, P. J. Morrison, Physica D 91, 1 (1996) (2) A.J. Lichtenberg and M.A. Lieberman, Regular and Chaotic Dynamics (Springer, New York, 1992) (3) D. Del-Castillo-Negrete and P. J. Morrison, Phys. Fluids A 5, 948 (1993) (4) Caroline G. L. Martins; R. Egydio de Carvalho; I. L. Caldas; M. Roberto. Labyrinthic standard non-twist map. Journal of Physics A, Mathematical and Theoretical, v. 44, p. 045102 (2011). (author)
SXR-XUV Diagnostics for Edge and Core of Magnetically Confined Plasmas
Energy Technology Data Exchange (ETDEWEB)
Stutman, Dan [Johns Hopkins University
2014-09-10
The present report summarizes the results obtained during a one-year extension of DoE grant “SXR-XUV Diagnostics for Edge and Core of Magnetically Confined Plasmas”, at Johns Hopkins University, aimed at completing the development of a new type of magnetic fusion plasma diagnostic, the XUV Transmission Grating Imaging Radiometer (TGIR). The TGIR enables simultaneous spatially and spectrally resolved measurements of the XUV/VUV radiated power from impurities in fusion plasmas, with high speed. The instrument was successfully developed and qualified in the laboratory and in experiments on a tokamak. Its future applications will be diagnostic of the impurity content and transport in the divertor and edge of advanced magnetic fusion experiments, such as NSTX Upgrade.
Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field; TOPICAL
International Nuclear Information System (INIS)
The paper gives the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integro-differential equation which takes into account the propulsion effect, viscosity and the drag force due to magnetic pumping and other interactions with the magnetic field. A criterion is obtained for the stabilization of the ''sausage'' instability of the streams by centrifugal force
Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field
International Nuclear Information System (INIS)
The paper gives the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integro-differential equation which takes into account the propulsion effect, viscosity and the drag force due to magnetic pumping and other interactions with the magnetic field. A criterion is obtained for the stabilization of the ''sausage'' instability of the streams by centrifugal force
Transport processes in magnetically confined plasmas
International Nuclear Information System (INIS)
Intensified studies of plasma transport in toroidal plasmas over the past three to five years have progressed through increased understanding in some areas and changed perceptions about the most important issues in other areas. Recent developments are reviewed for six selected topics: edge fluctuations and transport; L-H mode transition; core fluctuations; modern plasma turbulence theory; transient transport; and global scaling. Some of the developments that are highlighted include: the role of a strongly sheared poloidal flow in edge plasma turbulence, transport and the L-H transition; change of focus from κ perpendicular ρs ∼ 1 to κ perpendicular ρs much-lt 1 fluctuations in tokamak plasmas; modern Direct-Interaction-Approximation plasma turbulence and hybrid fluid/kinetic theoretical models; and transient transport experiments that are raising fundamental questions about our conceptions of local transport processes in tokamaks. 104 refs., 6 figs
Advanced diagnostics for magnetic and inertial confinement fusion
International Nuclear Information System (INIS)
This book is a collection of papers, written by specialists in the field, on advanced topics of nuclear fusion diagnostics. The 78 contributions were originally presented at the International Conference on Advanced Diagnostics for Magnetic and Inertial Fusion held at Villa Monastero, Italy in September 2001. Both magnetically confined and inertial fusion programmes are quite extensively covered, with more emphasis given to the former scheme. In the case of magnetic confinement, since the present international programme is strongly focused on next-step devices, particular attention is devoted to techniques and technologies viable in an environment with strong neutron fluxes. Indeed, in the first section, the various methods are considered in the perspective of performing the measurements of the relevant parameters in conditions approaching a burning plasma, mainly in the Tokamak configuration. The most demanding requirements, like the implications of the use of tritium and radiation resistance, are reviewed and the most challenging open issues, which require further research and development, are also clearly mentioned. The following three sections are devoted to some of the most recent developments in plasma diagnostics, which are grouped according to the following classification: 'Neutron and particle diagnostics', 'Optical and x-ray diagnostics' and 'Interferometry, Polarimetry and Thomson Scattering'. In these chapters, several of the most recent results are given, covering measurements taken on the most advanced experiments around the world. Here the developments described deal more with the requirements imposed by the physical issues to be studied. They are therefore more focused on the approaches adopted to increase the spatial and time resolution of the diagnostics, on some methods to improve the characterisation of the turbulence and on fast particles. Good coverage is given to neutron diagnostics, which are assuming increasing relevance as the plasma
On the axially symmetric equilibrium of a magnetically confined plasma
International Nuclear Information System (INIS)
The axially symmetric equilibrium of a magnetically confined plasma is reconsidered, with the special purpose of studying high-beta schemes with a purely poloidal magnetic field. A number of special solutions of the pressure and magnetic flux functions are shown to exist, the obtained results may form starting-points in a further analysis of physically relevant configurations. (Auth.)
Plasma confinement in a magnetic dipole
International Nuclear Information System (INIS)
A dipole fusion confinement device is stable to MHD interchange and ballooning modes when the pressure profile is sufficiently gentle. The plasma can be confined at high beta, is steady state and disruption free. Theory indicates that when the pressure gradient is sufficiently gentle to satisfy MHD requirements drift waves will also be stable. The dipole approach is particularly applicable for advanced fuels. A new experimental facility is presently being built to test the stability and transport properties of a dipole-confined plasma. (author)
Advancements of microwave diagnostics in magnetically confined plasmas
Mase, A.; Kogi, Y.; Ito, N.; Yokota, Y.; Akaki, K.; Kawahata, K.; Nagayama, Y.; Tokuzawa, T.; Yamaguchi, S.; Hojo, H.; Oyama, N.; N C Luhmann Jr.,; Park, H. K.; Donne, A. J. H.
2009-01-01
Microwave to millimeter-wave diagnostic techniques such as interferometry, reflectometry, scattering and radiometry have been powerful tools for diagnosing magnetically confined plasmas. Recent advances in electronic devices and components together with computer technology have enabled the developme
Escape patterns due to ergodic magnetic limiters in tokamaks with reversed magnetic shear
International Nuclear Information System (INIS)
In this work we study the ergodic magnetic limiters (EML) action on field lines from the point of view of a chaotic scattering process, considering the so-called exit basins, or sets of points in the chaotic region which originate field lines hitting the wall in some specified region. We divide the tokamak wall into three areas of equal poloidal angular length, corresponding to different exits for a chaotic field line. In order to obtain the exit basins we used a grid chosen inside a small rectangle which comprises a representative part of the chaotic region near the wall. Thus, exit basins were obtained for a tokamak wall with reversed magnetic shear. The no-twist mapping describes the perturbed magnetic field lines with two chains of magnetic islands and chaotic field lines in their vicinity. For a perturbing resonant magnetic field with a fixed helicity, the observed escape pattern changes with the perturbation intensity. (authors)
Impact of magnetic perturbation fields on tokamak plasmas
International Nuclear Information System (INIS)
Non-axisymmetric external magnetic perturbation (MP) fields arise in every tokamak e.g. due to not perfectly positioned external coils. Additionally many tokamaks, like ASDEX Upgrade (AUG), are equipped with a set of external coils, which produce a 3D MP field in addition to the equilibrium field. This field is used to either compensate for the intrinsic MP field or to influence MHD instabilities such as Edge Localised Modes (ELMs) or Neoclassical Tearing Modes (NTMs). But these MP fields can also give rise to a more global plasma response. The resonant components can penetrate the plasma and influence the stability of existing NTMs or even lead to their formation via magnetic reconnection. In addition they exert a local torque on the plasma. These effects are less pronounced at high plasma rotation where the resonant field components are screened. The non-resonant components do not influence NTMs directly but slow down the plasma rotation globally via the neoclassical toroidal viscous torque. The island formation caused by the MP field as well as the interaction of pre-existing islands with the MP field at AUG is presented. It is shown that these effects can be modelled using a simple forced reconnection theory. Also the effect of resonant and non-resonant MPs on the plasma rotation at AUG is discussed.
Conceptual design of a commercial tokamak reactor using resistive magnets
International Nuclear Information System (INIS)
The potential of resistive magnet tokamaks as commercial electricity producing power plants is investigated. Parametric studies indicate that attractive design space exists for these reactors at relatively low field (2.5 to 4.5 T), moderate wall loading (3 to 4 MW/m2) and medium to large net electric outputs (>600 MW/sub e/). High toroidal beta (20 to 25%) possible in the second regime of plasma stability may provide advantages of reduced recirculating power and plasma current but moderate beta reactors (6 to 10%) remain attractive. A conceptual design for the Resistive magnet Commercial Tokamak Reactor (RCTR) is presented. The layout of the nuclear island is driven by compatibility requirements of the demounting capability with structural and blanket design considerations. The nuclear island is fully demountable with access to all components within the toroidal field coils possible via simple vertical lifts. The blanket system, segmented for vertical removal, uses a self-cooled liquid lithium breeder/coolant with vanadium structure and an HT-9 reflector. The first wall is also lithium cooled with a vanadium structure but is constructed in a single, pre-tested unit for assembly and periodic replacement. Ohmic and equilibrium field-coils are located within the bore of the toroidal field coil for improved performance
International Nuclear Information System (INIS)
This report examines the concept and the main characteristics of the torroidal magnet in a tokamak with a strong magnetic field and combined adiabatic compression of the plasma pinch for an experiment to achieve the parameter Q = 1
Electromagnetic wave scattering from magnetic fluctuations in tokamaks
International Nuclear Information System (INIS)
Cross sections are calculated for electromagnetic wave scattering and mode transformation from magnetic and density fluctuations in the vicinity of the principal electron cutoffs and resonances in a homogeneous plasma. For the special case of scattering perpendicular to the magnetic field, density fluctuations scatter ordinary to ordinary and extraordinary to extraordinary modes -- but cannot transform these modes. On the other hand, magnetic fluctuations perpendicular to the field can transform modes but cannot scatter on a single branch. For incident frequencies on the order of the electron plasma frequency or gyrofrequency, the cross sections for scattering and transformation due to field and density fluctuations have a similar value. Estimates are given for scattering in a tokamak plasma with special emphasis on the question of how to detect and localize magnetic field fluctuations. Toroidal effects are handled by ray tracing. Ray tracing calculations and estimates of practical limitations on detection technique show that magnetic fluctuations can be detected and localized by this method -- even when the magnetic fluctuation levels are orders of magnitude lower than the density fluctuations. 33 refs., 12 figs
International Nuclear Information System (INIS)
To investigate the effects of confinement of fast electrons on poloidal beta equilibrium, experiments under different toroidal magnetic mirror ratios, MOMFC, were performed in electron cyclotron heated plasma in the spherical tokamak QUEST. The proportional constants of the relation between plasma current and vertical magnetic fields decreased with increase in MOMFC. The poloidal field null point appeared in the chamber for MOMFC > 1.8 at a plasma current value of ∼15 kA. Poloidal beta and temperature of hard X-rays increased with MOMFC. This suggests that high poloidal beta equilibrium plasma is produced by better confinement of energetic trapped particles. (author)
International Nuclear Information System (INIS)
The Microwave Tokamak Experiment, now under construction at the Laboratory, will use microwave heating from a free-electron laser. The intense microwave pulses will be injected into the tokamak to realize several goals, including a demonstration of the effects of localized heat deposition within magnetically confined plasma, a better understanding of energy confinement in tokamaks, and use of the new free-electron laser technology for plasma heating. The experiment, soon to be operational, provides an opportunity to study dense plasmas heated by powers unprecedented in the electron-cyclotron frequency range required by the especially high magnetic fields used with the MTX and needed for reactors. 1 references, 5 figures, 3 tables
Transport and confinement in the Mega Ampère Spherical Tokamak (MAST) plasma
Akers, R. J.; Ahn, J. W.; Antar, G. Y.; Appel, L. C.; Applegate, D.; Brickley, C.; Bunting, C.; Carolan, P. G.; Challis, C. D.; Conway, N. J.; Counsell, G. F.; Dendy, R. O.; Dudson, B.; Field, A. R.; Kirk, A.; Lloyd, B.; Meyer, H. F.; Morris, A. W.; Patel, A.; Roach, C. M.; Rohzansky, V.; Sykes, A.; Taylor, D.; Tournianski, M. R.; Valovi, M.; Wilson, H. R.; Axon, K. B.; Buttery, R. J.; Ciric, D.; Cunningham, G.; Dowling, J.; Dunstan, M. R.; Gee, S. J.; Gryaznevich, M. P.; Helander, P.; Keeling, D. L.; Knight, P. J.; Lott, F.; Loughlin, M. J.; Manhood, S. J.; Martin, R.; McArdle, G. J.; Price, M. N.; Stammers, K.; Storrs, J.; Walsh, M. J.; MAST, the; NBI Team
2003-12-01
A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampère Spherical Tokamak (MAST) the tools required for studying confinement and transport, from the core through to the plasma edge and scrape-off-layer (SOL). The H-mode edge transport barrier is now routinely turned on and off using a combination of poloidally localized fuelling and fine balancing of the X-points. Theory, supported by experiment, indicates that the edge radial electric field and toroidal flow velocity (thought to play an important role in H-mode access) are largest if gas fuelling is concentrated at the inboard side. H-mode plasmas show predominantly type III ELM characteristics, with confinement HH factor (w.r.t. scaling law IPB98[y, 2]) around ~1.0. Combining MAST H-mode data with the International Tokamak Physics Activities (ITPA) analyses, results in an L H power threshold scaling proportional to plasma surface area (rather than PLH ~ R2). In addition, MAST favours an inverse aspect ratio scaling PLH ~ egr0.5. Similarly, the introduction of type III ELMing H-mode data to the pedestal energy regression analysis introduces a scaling Wped ~ egr-2.13 and modifies the exponents on R, BT and kgr. Preliminary TRANSP simulations indicate that ion and electron thermal diffusivities in ELMing H-mode approach the ion-neoclassical level in the half-radius region of the plasma with momentum diffusivity a few times lower. Linear flux-tube ITG and ETG microstability calculations using GS2 offer explanations for the near-neoclassical ion diffusivity and significantly anomalous electron diffusivity seen on MAST. To complement the baseline quasi-steady-state H-mode, newly developed advanced regimes are being explored. In particular, 'broad' internal transport barriers (ITBs) have been formed using techniques developed at conventional aspect ratio. Electron and ion energy diffusivities
Transport and confinement in the Mega Ampere Spherical Tokamak (MAST) plasma
International Nuclear Information System (INIS)
A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampere Spherical Tokamak (MAST) the tools required for studying confinement and transport, from the core through to the plasma edge and scrape-off-layer (SOL). The H-mode edge transport barrier is now routinely turned on and off using a combination of poloidally localized fuelling and fine balancing of the X-points. Theory, supported by experiment, indicates that the edge radial electric field and toroidal flow velocity (thought to play an important role in H-mode access) are largest if gas fuelling is concentrated at the inboard side. H-mode plasmas show predominantly type III ELM characteristics, with confinement HH factor (w.r.t. scaling law IPB98[y, 2]) around approx. 1.0. Combining MAST H-mode data with the International Tokamak Physics Activities (ITPA) analyses, results in an L-H power threshold scaling proportional to plasma surface area (rather than PLH approx. R2). In addition, MAST favours an inverse aspect ratio scaling PLH approx. epsilon 0.5. Similarly, the introduction of type III ELMing H-mode data to the pedestal energy regression analysis introduces a scaling Wped approx. epsilon -2.13 and modifies the exponents on R, BT and Kappa. Preliminary TRANSP simulations indicate that ion and electron thermal diffusivities in ELMing H-mode approach the ion-neoclassical level in the half-radius region of the plasma with momentum diffusivity a few times lower. Linear flux-tube ITG and ETG microstability calculations using GS2 offer explanations for the near-neoclassical ion diffusivity and significantly anomalous electron diffusivity seen on MAST. To complement the baseline quasi-steady-state H-mode, newly developed advanced regimes are being explored. In particular, 'broad' internal transport barriers (ITBs) have been formed using techniques developed at conventional aspect ratio
Transport and confinement in the Mega Ampere Spherical Tokamak (MAST) plasma
Energy Technology Data Exchange (ETDEWEB)
Akers, R J; Ahn, J W; Appel, L C; Brickley, C; Bunting, C; Carolan, P G; Challis, C D; Conway, N J; Counsell, G F; Dendy, R O; Dudson, B; Field, A R; Kirk, A; Lloyd, B; Meyer, H F; Morris, A W; Patel, A; Roach, C M; Sykes, A; Taylor, D; Tournianski, M R; Valovic, M; Wilson, H R; Axon, K B; Buttery, R J; Ciric, D; Cunningham, G; Dowling J; Dunstan, M R; Gee, S J; Gryaznevich, M P; Helander, P; Keeling, D L; Knight, P J; Lott, F; Loughlin, M J; Manhood, S J; Martin, R; McArdle, G J; Price, M N; Stammers, K; Storrs, J [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Antar, G Y [Fusion Energy Research Program, University of California San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0417 (United States); Applegate, D [Imperial College of Science, Technology and Medicine, University of London, London SW7 2BZ (United Kingdom); Rohzansky, V [St. Petersburg State Politechnical University, Polytechnicheskaya 29, 195251 St. Petersburg (Russian Federation); Walsh, M J [Walsh Scientific Ltd., Abingdon, Oxon OX14 3EB (United Kingdom)
2003-12-01
A combination of recently installed state-of-the-art imaging and profile diagnostics, together with established plasma simulation codes, are providing for the first time on Mega Ampere Spherical Tokamak (MAST) the tools required for studying confinement and transport, from the core through to the plasma edge and scrape-off-layer (SOL). The H-mode edge transport barrier is now routinely turned on and off using a combination of poloidally localized fuelling and fine balancing of the X-points. Theory, supported by experiment, indicates that the edge radial electric field and toroidal flow velocity (thought to play an important role in H-mode access) are largest if gas fuelling is concentrated at the inboard side. H-mode plasmas show predominantly type III ELM characteristics, with confinement H{sub H} factor (w.r.t. scaling law IPB98[y, 2]) around approx. 1.0. Combining MAST H-mode data with the International Tokamak Physics Activities (ITPA) analyses, results in an L-H power threshold scaling proportional to plasma surface area (rather than P{sub LH} approx. R{sup 2}). In addition, MAST favours an inverse aspect ratio scaling P{sub LH} approx. epsilon 0.5. Similarly, the introduction of type III ELMing H-mode data to the pedestal energy regression analysis introduces a scaling W{sub ped} approx. epsilon -2.13 and modifies the exponents on R, B{sub T} and Kappa. Preliminary TRANSP simulations indicate that ion and electron thermal diffusivities in ELMing H-mode approach the ion-neoclassical level in the half-radius region of the plasma with momentum diffusivity a few times lower. Linear flux-tube ITG and ETG microstability calculations using GS2 offer explanations for the near-neoclassical ion diffusivity and significantly anomalous electron diffusivity seen on MAST. To complement the baseline quasi-steady-state H-mode, newly developed advanced regimes are being explored. In particular, 'broad' internal transport barriers (ITBs) have been formed using
Modified magnetic quantum dot with electric confining potentials
International Nuclear Information System (INIS)
The electronic properties of a modified magnetic quantum dot are studied. The modified magnetic quantum dot is a quantum structure that is formed by spatially inhomogeneous distributions of magnetic fields. Electrons are magnetically confined to the plane where the magnetic fields inside and outside the dot are different from each other. The energy spectrum exhibits quite different features depending on the directions of the magnetic fields inside and outside the dot. In particular, the case of opposite directions of the fields is more interesting than that of the same direction. An electrostatic potential is introduced to the system to study the effects of an electric confining potential on the eigenenergy of a single electron in the modified magnetic quantum dot. The additional potential raises the whole energy spectrum and changes its shape. The ground-state angular momentum transitions occurring in a bare modified magnetic quantum dot disappear on introduction of the additional parabolic potential
An equation describing diffusivity of liquid atoms by magnetic confinement
International Nuclear Information System (INIS)
In this work, we report an obvious low field-induced magnetic confinement effect on the diffusivity in binary metallic melts under a weak magnetic field. A quantitative description of this nontrivial dynamic behavior is given by a physical analytical model based on the Hall effect, which is in agreement with our experimental results. Meanwhile, a quadratic B dependence of the dynamic viscosity obtained in the same confined environment is observed. Our results show that one can effectively control the atomic diffusion process of metallic melts by the application of magnetic field. Meanwhile, this magnetic confinement effect at atomic scale should provide an important new ingredient to deeply understand the condensed matter physics under the external magnetic field. (paper)
Energy confinement studies of lower hybrid current driven discharges in the Alcator C tokamak
International Nuclear Information System (INIS)
The energy confinement properties of purely RF-driven plasmas on Alcator C are being investigated by experimental measurements of the bulk electron and ion temperature profiles, and by numerical modelling of the lower hybrid wave propagation and thermal energy transport. Power balance studies are performed on plasmas with parameters n-bar/sub e/ = 3-7 x 1013 cm-3, B = 7-11 T, I/sub p/ = 100-200 kA, and q(a)> or =8, and with RF powers up to 1 MW at 4.6 GHz. The temperature mesurements from RF-driven discharges are compared with those from similar ohmic discharges (identical current and density). The gross energy confinement time, defined by tau/sub E/03/2 (Σ∫n/sub j/T/sub j/ dV)/P/sub i//sub n/, is lower in the RF-driven discharges than in the ohmic ones by a factor of 1.5 to 4, depending on the plasma conditions and RF power. While tau/sub E/ in ohmic discharges increases with density and is independent of the toroidal field, the confinement time in the RF-driven discharges decreases with RF power, is independent of density in the range n-bar/sub e/ = 3-7 x 1013cm-3, and increases with the toroidal magnetic field. The confinement degrades slightly with increasing current in both RF-driven and ohmic discharges. The code used to simulate these results employs a lower hybrid ray tracing package, a Fokker-Planck code for the evolution of the fast electron tail, and enhanced thermal transport models for auxiliary-heated plasmas. In the code simulations, more than 80% of the injected RF power is absorbed by electron Landau damping in the inner half of the plasma column, the remainder being dissipated by collisions near the plasma edge
Energy confinement studies of lower hybrid current driven discharges in the Alcator C tokamak
International Nuclear Information System (INIS)
The energy confinement properties of purely rf-driven plasmas on Alcator C are being investigated by experimental measurements of the bulk electron and ion temperature profiles, and by numerical modelling of the lower hybrid wave propagation and thermal energy transport. Power balance studies are performed on plasmas with parameters n bar/sub e/ = 3 - 7 x 1013 cm-3, B = 7 - 11 T, I/sub p/ = 100 - 200 kA, and q (a) greater than or equal to 8, and with rf powers up to 1 MW at 4.6 GHz. The temperature measurements from rf-driven discharges are compared with those from similar ohmic discharges (identical current and density). The gross energy confinement time is lower in the rf-driven discharges than in the ohmic ones by a factor of 1.5 to 4, depending on the plasma conditions and rf power. While tau/sub E/ in ohmic discharges increases with density and is independent of the toroidal field, the confinement time in the rf-driven discharges decreases with rf power, is independent of density in the range n bar/sub e/ = 3 - 7 x 1013 cm-3, and increases with the toroidal magnetic field. The confinement degrades slightly with increasing current in both rf-driven and ohmic discharges. The code used to simulate these results employs a lower hybrid ray tracing package, a Fokker-Planck code for the evolution of the fast electron tail, and enhanced thermal transport models for auxiliary-heated plasmas. In the code simulations, more than 80% of the injected rf power is absorbed by electron Landau damping in the inner half of the plasma column, the remainder being dissipated by collisions near the plasma edge. To correctly simulate the experimentally observed temperatures, the electron thermal diffusivity must be increased with rf power and/or density relative to its ohmic values
Investigation of magnetic modes in the ASDEX tokamak
International Nuclear Information System (INIS)
Properties of MHD-modes in the ASDEX Tokamak have been investigated by application and further development of the MIRNOV-diagnostics, i.e. measurement of magnetic field fluctuations. In addition to evaluation methods supported by models, also a model-independent statistical data analysis makes sense. The very important physics of mode locking, i.e. the slowing-down of rotating modes is examined. An elaborated theoretical model allows an interpretation of experimental results. Especially interesting is the loss of the angular momentum of rotating plasmas by mode locking. Experiments for mode stabilisation and prevention of electric current breakdown are discussed. Additional MHD-processes under different plasma conditions are treated on the fundament of the devloped model ideas. The author shows that the main tokamak plasma is described very well by one-dimensional models with cylindrical geometry, while the boundary zone of the plasma demands a more complex analysis. In the appendix a concept for the investigation of the MHD-activity in ASDEX-Upgrade is discussed. (AH)
Neutron emission spectroscopy for magnetic confinement experiments
International Nuclear Information System (INIS)
Neutron diagnostics for plasmas of tokamaks in measurements of flux and energy distribution (spectrum) of the neutron emission are discussed. Neutron emission spectroscopy (NES) is the most exacting of these diagnostics and the one least developed relative to its potential, instrumentally and functionally. The use and results of NES are reviewed to illustrate NES diagnostic functions from the beginning of fusion research in the 50's to the latest achievements in the sub-ignited plasmas at JET 1997. The advancement of NES diagnostics are projected to the next step experiments planned to be conducted close to ignition at ITER. The potential role of NES to handle several essential diagnostic functions on ITER are compared with the present plans for a neutron diagnostics complement without employment of state-of-the-art spectrometry methods
Apparatus for magnetic and electrostatic confinement of plasma
Energy Technology Data Exchange (ETDEWEB)
Rostoker, Norman; Binderbauer, Michl
2016-07-05
An apparatus and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions ions are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Magnetic Domain Confinement by Anisotropy Modulation
Li, S. P.; Lew, W. S.; Bland, J. A.; Lopez-Diaz, L.; Vaz, C. A.; Natali, M.; Chen, Y.
2002-02-01
The spin configuration in a magnet is in general a ``natural'' consequence of both the intrinsic properties of the material and the sample dimensions. We demonstrate that this limitation can be overcome in a homogeneous ferromagnetic film by engineering an anisotropy contrast. Substrates with laterally modulated single-crystal and polycrystalline surface regions were used to induce selective epitaxial growth of a ferromagnetic Ni film. The resulting spatially varying magnetic anisotropy leads to regular perpendicular and in-plane magnetic domains, separated by a new type of magnetic wall-the ``anisotropy constrained'' magnetic wall.
Energy Technology Data Exchange (ETDEWEB)
Callen, J.D.
1978-01-01
This discussion covers the following three papers: (1) magnetic islandography in tokamaks, (2) scaling laws for energy lifetimes in tokamaks, and (3) simulation of discharge dynamics in tokamaks. (MOW)
Considerations of the high magnetic field tokamak path on the approach to fusion energy
Marmar, Earl
2015-11-01
This tutorial will review the physics basis, and its applications, for high magnetic field, compact visions of steady-state pilot plants and fusion reactors. This includes: energy and particle confinement; transport barriers; heating and current drive; scrape-off layer and divertor physics including implications for power handling, and ash/impurity control. The development of new technologies, particularly high-temperature, high critical magnetic field superconducting materials opens a new opportunity to consider the leverage of on-axis magnetic fields of 10T or more, enabling the feasibility of smaller sized devices on the path to fusion energy, including a pilot plant which could produce hundreds of megawatts of net electricity in a 10T tokamak with major radius of order 3 meter. Incorporating jointed magnetic coils, also made feasible by the high temperature superconductors, can dramatically improve flexibility of experimental superconducting facilities, and ultimately maintainability for reactor systems. Steady-state requires high bootstrap fraction, combined with efficient off-axis current drive, and existing and new approaches for RF sustainment will be covered, including Lower Hybrid Current Drive (both from the low- and high-field side), ECCD, and fast-wave techniques. External torque drive from neutral beams, routinely used in most present-day experiments to enhance confinement and suppress instabilities, will be weak or absent in reactors. Alternative, RF-based flow drive, using mode-converted ICRF waves will be discussed. All reactor concepts have extraordinary power handling requirements, combined with stringent limits on PFC erosion and impurity sources; the current state of the art in divertor configurations will be compared with emerging and new concepts, including snowflake, x-point, x-divertor and liquid metals, to meet these challenges. Supported by USDOE.
Stability properties and fast ion confinement of hybrid tokamak plasma configurations
Graves, J. P.; Brunetti, D.; Pfefferle, D.; Faustin, J. M. P.; Cooper, W. A.; Kleiner, A.; Lanthaler, S.; Patten, H. W.; Raghunathan, M.
2015-11-01
In hybrid scenarios with flat q just above unity, extremely fast growing tearing modes are born from toroidal sidebands of the near resonant ideal internal kink mode. New scalings of the growth rate with the magnetic Reynolds number arise from two fluid effects and sheared toroidal flow. Non-linear saturated 1/1 dominant modes obtained from initial value stability calculation agree with the amplitude of the 1/1 component of a 3D VMEC equilibrium calculation. Viable and realistic equilibrium representation of such internal kink modes allow fast ion studies to be accurately established. Calculations of MAST neutral beam ion distributions using the VENUS-LEVIS code show very good agreement of observed impaired core fast ion confinement when long lived modes occur. The 3D ICRH code SCENIC also enables the establishment of minority RF distributions in hybrid plasmas susceptible to saturated near resonant internal kink modes.
Magnetic islands and disruptions in the TOSCA tokamak
International Nuclear Information System (INIS)
Measurements with a magnetic probe, internal coils, soft X-rays and visible light on a small tokamak reveal the presence of tearing modes with m=4,3,2, and n=1. The modes grow, rotate and saturate at a level bsub(r)/Bsub(theta) approximately <3%, which gives rise to magnetic islands of width approximately <1.5cm for m=3. The islands are more elongated at this level than a simple calculation suggests, and field-line calculations and experiments suggest that the surfaces may be broken between them. The island width is predicted by a cylindrical initial-value calculation for the instabilities, using the measured current distribution, saturation level and magnetic Reynolds number. If the m=3 mode exceeds the 3% level a minor disruption results. An m=2 mode at a level of 6% gives rise to a major disruption whether or not an internal m=1 mode is present. No other mode appears to play a significant role in the disruptive process. (author)
Diffusive heat transport across magnetic islands and stochastic layers in tokamaks
International Nuclear Information System (INIS)
Heat transport in tokamak plasmas with magnetic islands and ergodic field lines was simulated at realistic plasma parameters in realistic tokamak geometries. This requires the treatment of anisotropic heat diffusion, which is more efficient along magnetic field lines by up to ten orders of magnitude than perpendicular to them. Comparisons with analytical predictions and experimental measurements allow to determine the stability properties of neoclassical tearing modes as well as the experimental heat diffusion anisotropy.
High-Energy Electron Confinement in a Magnetic Cusp Configuration
Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni
2015-04-01
We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.
International Nuclear Information System (INIS)
The measurement of plasma poloidal magnetic field (B) profiles in tokamaks with good temporal and spatial resolution has proven to be a difficult but important measurement. A large range of toroidal confinement phenomena is expected to depend sensitively on the radial variation of B including the tearing instability, sawtooth oscillations, disruptions, and transport. Experimental confirmation of theoretical models describing these phenomena has been hampered by the lack of detailed B measurements. A fifteen chord far-infrared (FIR) polarimeter has been developed to measure B in the Microwave Tokamak, Experiment (MTX). Polarimetry utilizes the well known Faraday rotation effect, which causes a rotation of the polarization of an FIR beam propagating in the poloidal plane. The rotation angle is proportional to the component of B parallel to the beam. A new technique for determining the Faraday rotation angle is introduced, based on phase measurements of a rotating polarization ellipse. This instrument has been used successfully to measure B profiles for a wide range of experiments on MTX. For ohmic discharges, measurements of the safety factor on axis give q0 ∼ 0.75 during sawteeth and q0 > 1 without sawteeth. Large perturbations to the polarimeter signals correlated with the sawtooth crash are observed during some discharges. Measurements in discharges with electron cyclotron heating (ECH) show a transition from a hollow to peaked J profile that is triggered by the ECH pulse. Current-ramp experiments were done to perturb the J profile from the nominal Spitzer conductivity profile. Profiles for initial current ramps and ramps starting from a stable equilibrium have been measured and are compared with a cylindrical diffusion model. Finally, the tearing mode stability equation is solved using measured J profiles. Stability predictions are in good agreement with the existence of oscillations observed on the magnetic loops
Experimental investigation of magnetically confined plasma loops
Energy Technology Data Exchange (ETDEWEB)
Tenfelde, Jan
2012-12-11
Arch-shaped magnetic flux tubes generated in a pulsed-power plasma experiment were investigated with a variety of diagnostics concerning their expansion properties. Specifically, the expansion velocity was of interest, which is observed as constant for a wide range of experimental parameters. An MHD transport mechanism is investigated as possible cause of a uniform arch cross section: Axial transport of poloidal magnetic flux along the plasma may cause a pinch force leading to a uniform diameter along the arch. Despite numerous experimental findings at a very similar experimental setup, no indication for the relevance of this process could be found. Instead, magnetic probe data showed that the plasma current in the apex region is constant. A constant expansion velocity was observed for considerably different experimental conditions. This included different plasma source designs with fundamentally different toroidal magnetic field topology and variation of the working gas, which lead to plasma densities lower by an order of magnitude. Inside the current channel of the arch, Alfven velocities were estimated. To this end, plasma density profiles obtained from interferometry were inverted to obtain local densities, which were in turn verified by means of Stark broadening of hydrogen Balmer lines. Furthermore, measurements of multiple components of the magnetic field of the plasma arch were performed. An estimate for the conductivity was obtained from Spitzer's formula for fully ionized plasma using electron temperatures obtained from elementary optical emission spectroscopy. From the presented data of ccd imaging, magnetic field probes, and to lesser extent, interferometry, the underlying assumption of residual plasma (and considerable plasma currents through it) below the actual arch structure is very plausible. Rough estimates of the electric field strength along the arch and results of the magnetic field measurements showed, that the detected expansion
Experimental investigation of magnetically confined plasma loops
International Nuclear Information System (INIS)
Arch-shaped magnetic flux tubes generated in a pulsed-power plasma experiment were investigated with a variety of diagnostics concerning their expansion properties. Specifically, the expansion velocity was of interest, which is observed as constant for a wide range of experimental parameters. An MHD transport mechanism is investigated as possible cause of a uniform arch cross section: Axial transport of poloidal magnetic flux along the plasma may cause a pinch force leading to a uniform diameter along the arch. Despite numerous experimental findings at a very similar experimental setup, no indication for the relevance of this process could be found. Instead, magnetic probe data showed that the plasma current in the apex region is constant. A constant expansion velocity was observed for considerably different experimental conditions. This included different plasma source designs with fundamentally different toroidal magnetic field topology and variation of the working gas, which lead to plasma densities lower by an order of magnitude. Inside the current channel of the arch, Alfven velocities were estimated. To this end, plasma density profiles obtained from interferometry were inverted to obtain local densities, which were in turn verified by means of Stark broadening of hydrogen Balmer lines. Furthermore, measurements of multiple components of the magnetic field of the plasma arch were performed. An estimate for the conductivity was obtained from Spitzer's formula for fully ionized plasma using electron temperatures obtained from elementary optical emission spectroscopy. From the presented data of ccd imaging, magnetic field probes, and to lesser extent, interferometry, the underlying assumption of residual plasma (and considerable plasma currents through it) below the actual arch structure is very plausible. Rough estimates of the electric field strength along the arch and results of the magnetic field measurements showed, that the detected expansion
Effects of negative magnetic shear in fusion plasma confinement. 1. A review of experimental studies
International Nuclear Information System (INIS)
A negative magnetic shear configuration is a potentially attractive mode of operation which enables an economical steady-state tokamak fusion reactor with high beta, high confinement and large bootstrap current fraction. This paper provides a review of experimental studies on the negative shear. Though negative shear configurations are formed naturally with large bootstrap current fraction, they have also been formed by current ramp-up with neutral beam heating or off-axis current drive. Formation of internal transport barrier with remarkable reduction of particle and heat transport have been observed in negative shear plasmas. Neoclassical-level ion thermal diffusivity and particle diffusivity have been realized as a result of nearly perfect disappearance of anomalous transport. The thermal transport on electrons has also been reduced in some devices. High beta values have been attained in combination with the H-mode. High fusion performance has been demonstrated. (author). 84 refs
Turbulent Generation of Flows and Magnetic Field at the Rational Magnetic Surfaces of a Tokamak
International Nuclear Information System (INIS)
Full text: Comparative analysis of generation of large-scale structures, zonal flows and streamers, by drift wave turbulence is conducted for periodic systems with magnetic shear such as a tokamak. In a strong magnetic field dynamics of quasi two-dimensional perturbations strongly depends on the value of the wave vector along the magnetic field. When the parallel wave vector is significantly large, so that the parallel phase velocity of perturbation is small compared to electron thermal velocity, the parallel electron motion results in a finite electron density perturbation. It follows the Boltzmann distribution. However, for large-scale structures with poloidal and toroidal symmetry m = n = 0, and the parallel wave vector is zero. This results in strong reduction of density perturbation for m = n = 0. This difference has profound consequences for generation of large-scale zonal flows and streamers due to different structure of the nonlinear interaction matrix. The interaction term has a structure similar to the standard convective nonlinearity for zonal flows, while for streamers it has the structure of the Hasegawa-Mima nonlinearity (which is the higher order due to a small parameter associated with a finite ion Larmor radius). Respectively, zonal flows have the larger growth rate gamma(ZF) compared to that of the streamers. It is shown that 3D electromagnetic helical perturbations will have the growth rate comparable to that of zonal flows if their symmetry coincides with the symmetry of rational magnetic surface, m = nq. The field line bending provides a stabilizing effect and thus determines the radial localization of such structures. Therefore, it is expected that three-dimensional structures of flows and magnetic field will be preferentially generated at the rational magnetic surfaces of a tokamak with a growth rate of order gamma(ZF). This theoretical result may corroborate existing experimental correlations of large-scale shear flow structures with
International Nuclear Information System (INIS)
Large sub-millisecond heat pulses due to Type-I ELMs have been eliminated reproducibly in DIII.D for periods approaching 7 energy confinement times with small dc currents driven in a simple magnetic perturbation coil. The current required to eliminate all but a few isolated Type-I ELM impulses during a coil pulse is less than 0.4% of plasma current. Based on vacuum magnetic field line modeling, the perturbation fields resonate strongly with plasma flux surfaces across most of the pedestal region (0.9 ≤ ΨN ≤ 1.0) when q95 = 3.7±0.2 creating small remnant magnetic islands surrounded by weakly stochastic field lines. The stored energy, βN, H-mode quality factor and global energy confinement time are unaltered. Although some isolated ELM-like events typically occur, long periods free of large Type-I ELMs (Δt > 4-6 τE) have been reproduced numerous times, on multiple experimental run days including cases matching the ITER scenario 2 flux surface shape. Since large Type-I ELM impulses represent a severe constraint on the survivability of the divertor target plates in future fusion devices such as ITER, a proven method of eliminating these impulses is critical for the development of tokamak reactors. Results presented in this paper indicate that non-axisymmetric edge magnetic perturbations could be a promising option for controlling ELMs in future tokamaks such as ITER. (author)
The technology and science of steady-state operation in magnetically confined plasmas
International Nuclear Information System (INIS)
The steady-state operation of magnetically confined fusion plasmas is considered as one of the 'grand challenges' of future decades, if not the ultimate goal of the research and development activities towards a new source of energy. Reaching such a goal requires the high-level integration of both science and technology aspects of magnetic fusion into self-consistent plasma regimes in fusion-grade devices. On the physics side, the first constraint addresses the magnetic confinement itself which must be made persistent. This means to either rely on intrinsically steady-state configurations, like the stellarator one, or turn the inductively driven tokamak configuration into a fully non-inductive one, through a mix of additional current sources. The low efficiency of the external current drive methods and the necessity to minimize the re-circulating power claim for a current mix strongly weighted by the internal 'pressure driven' bootstrap current, itself strongly sensitive to the heat and particle transport properties of the plasma. A virtuous circle may form as the heat and particle transport properties are themselves sensitive to the current profile conditions. Note that several other factors, e.g. plasma rotation profile, magneto-hydro-dynamics activity, also influence the equilibrium state. In the present tokamak devices, several examples of such 'advanced tokamak' physics research demonstrate the feasibility of steady-state regimes, though with a number of open questions still under investigation. The modelling activity also progresses quite fast in this domain and supports understanding and extrapolation. This high level of physics sophistication of the plasma scenario however needs to be combined with steady-state technological constraints. The technology constraints for steady-state operation are basically twofold: the specific technologies required to reach the steady-state plasma conditions and the generic technologies linked to the long pulse operation of a
International Nuclear Information System (INIS)
Intermediate between magnetic confinement (MFE) and inertial confinement (ICF) in time and density scales is an area of research now known in the US as magnetized target fusion (MTF) and in Russian as MAGO (MAGnitnoye Obzhatiye--magnetic compression). MAGO/MTF uses a magnetic field and preheated, wall-confined plasma fusion fuel within an implodable fusion target. The magnetic field suppresses thermal conduction losses in the fuel during the target implosion and hydrodynamic compression heating process. In contrast to direct, hydrodynamic compression of initially ambient-temperature fuel (i.e., ICF), MAGO/MTF involves two steps: (a) formation of a warm (e.g., 100 eV or higher), magnetized (e.g., 100 kG) plasma within a fusion target prior to implosion; (b) subsequent quasi-adiabatic compression by an imploding pusher, of which a magnetically driven imploding liner is one example. In this paper, the authors present ongoing activities and potential future activities in this relatively unexplored area of controlled thermonuclear fusion
Magnetically confined wind shocks in X-rays - A review
ud-Doula, Asif; Nazé, Yaël
2016-09-01
A subset (∼ 10%) of massive stars present strong, globally ordered (mostly dipolar) magnetic fields. The trapping and channeling of their stellar winds in closed magnetic loops leads to magnetically confined wind shocks (MCWS), with pre-shock flow speeds that are some fraction of the wind terminal speed. These shocks generate hot plasma, a source of X-rays. In the last decade, several developments took place, notably the determination of the hot plasma properties for a large sample of objects using XMM and Chandra, as well as fully self-consistent MHD modeling and the identification of shock retreat effects in weak winds. Despite a few exceptions, the combination of magnetic confinement, shock retreat and rotation effects seems to be able to account for X-ray emission in massive OB stars. Here we review these new observational and theoretical aspects of this X-ray emission and envisage some perspectives for the next generation of X-ray observatories.
Magnetically Confined Wind Shocks in X-rays - a Review
ud-Doula, Asif
2015-01-01
A subset (~ 10%) of massive stars present strong, globally ordered (mostly dipolar) magnetic fields. The trapping and channeling of their stellar winds in closed magnetic loops leads to magnetically confined wind shocks (MCWS), with pre-shock flow speeds that are some fraction of the wind terminal speed. These shocks generate hot plasma, a source of X-rays. In the last decade, several developments took place, notably the determination of the hot plasma properties for a large sample of objects using XMM-Newton and Chandra, as well as fully self-consistent MHD modelling and the identification of shock retreat effects in weak winds. Despite a few exceptions, the combination of magnetic confinement, shock retreat and rotation effects seems to be able to account for X-ray emission in massive OB stars. Here we review these new observational and theoretical aspects of this X-ray emission and envisage some perspectives for the next generation of X-ray observatories.
High Energy Electron Confinement in a Magnetic Cusp Configuration
Park, Jaeyoung; Sieck, Paul E; Offermann, Dustin T; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni
2014-01-01
We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.
Magnetic trap Tornado-X for plasma confinement and heating
International Nuclear Information System (INIS)
Description of the magnetic trap Tornado-X for plasma confinement and heating is presented. Results of the first studies on decaying plasma, which make it possible to conclude that plasma losses are determined by classic diffusion, are given. The plasma heating through charged particles drive in the crossed magnetic and electrical fields is accomplished. The rotating plasma parameters, obtained on the Tornado-650 facility, are reproduced at the initial stage
Improved energy confinement with nonlinear isotope effects in magnetically confined plasmas
Garcia, J; Jenko, F
2016-01-01
The efficient production of electricity from nuclear fusion in magnetically confined plasmas relies on a good confinement of the thermal energy. For more than thirty years, the observation that such confinement depends on the mass of the plasma isotope and its interaction with apparently unrelated plasma conditions has remained largely unexplained and it has become one of the main unsolved issues. By means of numerical studies based on the gyrokinetic theory, we quantitatively show how the plasma microturbulence depends on the isotope mass through nonlinear multiscale microturbulence effects involving the interplay between zonal flows, electromagnetic effects and the torque applied. This finding has crucial consequences for the design of future reactors since, in spite of the fact that they will be composed by multiple ion species, their extrapolation from present day experiments heavily relies on the knowledge obtained from a long experimental tradition based in single isotope plasmas.
Introduction to magnetic confinement fusion diagnostics
International Nuclear Information System (INIS)
These notes present a brief survey of some of the current diagnostic techniques used in magnetic fusion plasma devices. To give an idea of the range of parameters and geometries encountered the parameters of four representative experiments - PLT, TMX, ZT-40 and EBT-I(S) - are given. The central issue of all experiments is to understand the flow of power which can be summarized by two volume integrated equations for the ions and electrons
The Effects of Alpha Particle Confinement on Burning Plasma Tokamak Performance
Gormley, Robert P.
In this thesis, three effects of alpha particle plasma interactions on the global performance of a fusion reactor are studied, namely, (i) the energy coupling efficiency of the fast alpha particles with the bulk plasma, (ii) the relationship between imperfect alpha energy coupling to the bulk plasma and the resultant alpha particle/helium ash fuel dilution; and (iii) the neoclassical bootstrap current induced by fusion born alpha particles calculated self-consistently with the plasma equilibrium. First, the ion drift kinetic equation for the high energy alpha particles is reduced from the exact five dimensional form to a two dimensional form in radius r and energy E (plus time t). The resulting slowing-down diffusion equation is solved by a multiple energy group method. A theoretically based anomalous diffusion coefficient D_sp{alpha}{an} is then introduced from a self-consistent alpha particle Alfven wave turbulence solution (by F. Gang), in which D_sp{alpha}{an } itself depends on the gradient in alpha density. The temporal and spatial behavior of eta_ alpha is analyzed for an ITER-CDA physics phase fusion reactor. We find that eta_ alpha can be as low as 0.95 depending on the plasma operating temperature. Next, the relationship between the alpha-particle power coupling efficiency and the actual alpha-particle power that is coupled with the bulk plasma is investigated, this time taking into account the concomitant helium ash accumulation. It is found that the coupled power varies less than linearly with eta_alpha and is, in fact, significantly depressed for eta_alpha near unity. Combining these effects with a thermal power balance shows that the high temperature "thermally stable" side of the ignition boundary is pushed toward lower temperatures if either D_alpha increases (which results in a lower eta_alpha) or the helium-ash confinement time lengthens. This is a consequence of strengthened fuel dilution and imperfect alpha power coupling. Implications on the
Energy Technology Data Exchange (ETDEWEB)
Kim, Kimin [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Korea Advanced Institute of Science and Technology, Daejeon 305-701, Korea; Ahn, J-W [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Scotti, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Park, J-K [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Menard, J. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
2015-09-03
Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.
International Nuclear Information System (INIS)
The measurement of plasma poloidal magnetic field (B(theta)) profiles on tokamaks with good temporal and spatial resolution has proven to be a difficult but important measurement. A large range of toroidal confinement phenomena is expected to depend sensitively on the radial variation of B(theta) (or equivalently the current density J or safety factor q) including the tearing instability, sawtooth oscillations, disruptions, and transport. Experimental confirmation of theoretical models describing these phenomena has been hampered by the lack of detailed B(theta) measurements. A fifteen chord far-infrared (FIR) polarimeter has been developed to measure B(theta) in the Microwave Tokamak Experiment (MTX). Polarimetry utilizes the well-known Faraday rotation effect, which causes a rotation of the polarization of an FIR beam propagating in the poloidal plane. The rotation angle is proportional to the component of B(theta) parallel to the beam. A new technique for determining the Faraday rotation angle is introduced, based on phase measurements of a rotating polarization ellipse. This technique simplifies the implementation of large multi-chord systems, and minimizes the effect of amplitude variations caused by refraction. This instrument has been used successfully to measure B(theta) profiles for a wide range of experiments on MTX. For ohmic discharges, measurements of the safety factor on axis give q(0) approximately 0.75 during sawteeth and q(0) greater than 1 without sawteeth. Large perturbations to the polarimeter signals correlated with the sawtooth crash are observed during some discharges. Measurements in discharges with electron cyclotron heating (ECH) show a transition from a hollow to peaked J profile that is triggered by the ECH pulse. Heavy-metal impurity radiation is believed to be the cause of the initially hollow profile. Current-ramp experiments were done to perturb the J profile from the nominal Spitzer conductivity profile
Design study of toroidal magnets for tokamak experimental power reactors
International Nuclear Information System (INIS)
This report contains the results of a six-month study of superconducting toroidal field coils for a Tokamak Experimental Power Reactor to be built in the late 1980s. The designs are for 8 T and 12 T maximum magnetic field at the superconducting winding. At each field level two main concepts were generated; one in which each of the 16 coils comprising the system has an individual vacuum vessel and the other in which all the coils are contained in a single vacuum vessel. The coils have a D shape and have openings of 11.25 m x 7.5 m for the 8 T coils and 10.2 m x 6.8 m for the 12 T coils. All the designs utilize rectangular cabled conductor made from copper stabilized Niobium Titanium composite which operates at 4.2 K for the 8 T design and at 2.5 K for the 12 T design. Manufacturing procedures, processes and schedule estimates are also discussed
Magnetically confined plasma solar collector. [satellite based system in space
Walters, C. T.; Wolken, G., Jr.; Purvis, G. D., III
1978-01-01
The possibility of using a plasma medium for collecting solar energy in space is examined on the basis of a concept involving an orbiting magnetic bottle in which a solar-energy-absorbing plasma is confined. A basic system uses monatomic cesium as working fluid. Cesium evaporates from a source and flows into the useful volume of a magnetic bottle where it is photoionized by solar radiation. Ions and electrons lost through the loss cones are processed by a recovery system, which might be a combination of electromagnetic devices and heat engines. This study concentrates on the plasma production processes and size requirements, estimates of the magnetic field required to confine the plasma, and an estimate of the system parameters for a 10 GW solar collector using cesium.
A paramagnetic nearly isodynamic compact magnetic confinement system
International Nuclear Information System (INIS)
A coreless compact magnetic confinement system that consists of sets of helical windings and vertical magnetic field coils is investigated. The helical coils produce a small toroidal translation of the magnetic field lines and seed paramagnetism. The force-free component of the toroidal current strongly enhances the paramagnetism such that isodynamic conditions near the plasma centre can be approached. At β 5%, the configuration is stable to local MHD modes. Global MHD modes limit the toroidal current 2πJ to about 60kA for peaked J. Bootstrap-like hollow current profiles generate quasiaxisymmetric systems that require a close fitting conducting shell to satisfy external kink stability. (author)
International Nuclear Information System (INIS)
Recent advances in high-energy pulsed power capabilities, plasma formation techniques, plasma diagnostics, and multidimensional plasma computer codes make possible the evaluation of an unexplored approach to controlled thermonuclear fusion that is intermediate between magnetic confinement (MFE) and inertial confinement (ICF) in time and density scales. Existing capabilities appear adequate to explore the major physics issues in this area, perhaps up to and including fusion ignition, with relatively low operating costs and essentially no major capital investment. (author). 25 refs, 4 figs, 2 tabs
International Nuclear Information System (INIS)
Small three-dimensional (3D) magnetic perturbations can be used as a tool to control the edge plasma parameters in magnetically confined plasmas in high confinement mode (''H-mode'') to suppress edge instabilities inherent to this regime, the Edge Localized Modes (ELMs). In this work, the impact of rotating 3D resonant magnetic perturbation (RMP) fields on the edge plasma structure characterized by electron density and temperature fields is investigated. We study a low confinement (L-mode) edge plasma (r/a>0.9) with high resistivity (edge electron collisionality ν*e>4) at the TEXTOR tokamak. The plasma structure in the plasma edge is measured by a set of high resolution diagnostics: a fast CCD camera (Δt=20 μs) is set up in order to visualize the plasma structure in terms of electron density variations. A supersonic helium beam diagnostic is established as standard diagnostic at TEXTOR to measure electron density ne and temperature Te with high spatial (Δr=2 mm) and temporal resolution (Δt=20 μs). The measured plasma structure is compared to modeling results from the fluid plasma and kinetic neutral transport code EMC3-EIRENE. A sequence of five new observations is discussed: (1) Imaging of electron density variations in the plasma edge shows that a fast rotating RMP field imposes an edge plasma structure, which rotates with the external RMP rotation frequency of vertical stroke νRMP vertical stroke =1 kHz. (2) Measurements of the electron density and temperature provide strong experimental evidence that in the far edge a rotating 3D scrape-off layer (SOL) exists with helical exhaust channels to the plasma wall components. (3) Radially inward, the plasma structure at the next rational flux surface is found to depend on the relative rotation between external RMP field and intrinsic plasma rotation. For low relative rotation the plasma structure is dominated by a particle and energy loss along open magnetic field lines to the wall components. For high relative
Energy Technology Data Exchange (ETDEWEB)
Stoschus, Henning
2011-10-13
Small three-dimensional (3D) magnetic perturbations can be used as a tool to control the edge plasma parameters in magnetically confined plasmas in high confinement mode (''H-mode'') to suppress edge instabilities inherent to this regime, the Edge Localized Modes (ELMs). In this work, the impact of rotating 3D resonant magnetic perturbation (RMP) fields on the edge plasma structure characterized by electron density and temperature fields is investigated. We study a low confinement (L-mode) edge plasma (r/a>0.9) with high resistivity (edge electron collisionality {nu}{sup *}{sub e}>4) at the TEXTOR tokamak. The plasma structure in the plasma edge is measured by a set of high resolution diagnostics: a fast CCD camera ({delta}t=20 {mu}s) is set up in order to visualize the plasma structure in terms of electron density variations. A supersonic helium beam diagnostic is established as standard diagnostic at TEXTOR to measure electron density n{sub e} and temperature T{sub e} with high spatial ({delta}r=2 mm) and temporal resolution ({delta}t=20 {mu}s). The measured plasma structure is compared to modeling results from the fluid plasma and kinetic neutral transport code EMC3-EIRENE. A sequence of five new observations is discussed: (1) Imaging of electron density variations in the plasma edge shows that a fast rotating RMP field imposes an edge plasma structure, which rotates with the external RMP rotation frequency of vertical stroke {nu}{sub RMP} vertical stroke =1 kHz. (2) Measurements of the electron density and temperature provide strong experimental evidence that in the far edge a rotating 3D scrape-off layer (SOL) exists with helical exhaust channels to the plasma wall components. (3) Radially inward, the plasma structure at the next rational flux surface is found to depend on the relative rotation between external RMP field and intrinsic plasma rotation. For low relative rotation the plasma structure is dominated by a particle and energy loss
Magnetized plasma flow injection into tokamak and high-beta compact torus plasmas
Matsunaga, Hiroyuki; Komoriya, Yuuki; Tazawa, Hiroyasu; Asai, Tomohiko; Takahashi, Tsutomu; Steinhauer, Loren; Itagaki, Hirotomo; Onchi, Takumi; Hirose, Akira
2010-11-01
As an application of a magnetized coaxial plasma gun (MCPG), magnetic helicity injection via injection of a highly elongated compact torus (magnetized plasma flow: MPF) has been conducted on both tokamak and field-reversed configuration (FRC) plasmas. The injected plasmoid has significant amounts of helicity and particle contents and has been proposed as a fueling and a current drive method for various torus systems. In the FRC, MPF is expected to generate partially spherical tokamak like FRC equilibrium by injecting a significant amount of magnetic helicity. As a circumstantial evidence of the modified equilibrium, suppressed rotational instability with toroidal mode number n = 2. MPF injection experiments have also been applied to the STOR-M tokamak as a start-up and current drive method. Differences in the responses of targets especially relation with beta value and the self-organization feature will be studied.
Brillouin limit for electron plasmas confined on magnetic surfaces
International Nuclear Information System (INIS)
As is well known, the density of pure electron plasmas that are confined by a magnetic field is limited by the Brillouin density, nB ε0B2/2me. However, the electron density can be limited to a much lower value when the electrons are confined on magnetic surfaces, such as the surfaces produced by a stellarator. If the electron temperature is a spatial constant, the electron force-balance equation, me/e ν-→ ∇-→ν + ∇-→p / en = ∇-→Φ-ν-→xB-→, can be rewritten as ∇-→Φ* = ν-→xB-→*. The effective electric potential and the effective magnetic field are Φ* Φ - me/2eν2 - Tln(n) and B-→* B-→ - me/e ∇ x ν-→. The electron density for magnetic confinement in a cylinder with B-→ = Bz-circumflex is bounded by the Brillouin limit. If one assumes the electrons are pressureless and have a spatially constant density n0, then Φ = (en0/4ε0)r2. Both B-→* and Φ* vanish when n0 = nB, and the equation ∇-→Φ* = ν-→ x B-→* has no solutions for n0 > nB. The confinement of electrons on magnetic surfaces is lost when the field lines of the effective magnetic field B-→* leave the confinement region and strike the chamber walls. If the magnetic surfaces of the true field B-→ are described by the toroidal flux, ψt that they enclose, so B-→ ∇-→ψt = 0, then confinement is easily lost when ∇-→ψt ∇-→ x ν-→ has Fourier terms that resonate with the rotational transform of B-→, for then the B-→* surfaces are split by islands. The resonant Fourier terms are given by (B-→ x ∇-→ψt) ∇-→(ν||/B). In other words, resonant Fourier terms in the parallel flow of the electrons can cause a break up of the surfaces of the B-→* field. The parallel flow is determined by the condition that ∇-→ (nν-→) = 0, which implies B-→ ∇-→(v||/B) = -∇-→ (nν-→perpendicular).When n0B, the divergence of the perpendicular flow is given by ∇-→ (nν-→perpendicular) = (B-→ x ∇-→Φ) ∇-→(n/B2) . Variations
Robust Sliding Mode Control for Tokamaks
Directory of Open Access Journals (Sweden)
I. Garrido
2012-01-01
Full Text Available Nuclear fusion has arisen as an alternative energy to avoid carbon dioxide emissions, being the tokamak a promising nuclear fusion reactor that uses a magnetic field to confine plasma in the shape of a torus. However, different kinds of magnetohydrodynamic instabilities may affect tokamak plasma equilibrium, causing severe reduction of particle confinement and leading to plasma disruptions. In this sense, numerous efforts and resources have been devoted to seeking solutions for the different plasma control problems so as to avoid energy confinement time decrements in these devices. In particular, since the growth rate of the vertical instability increases with the internal inductance, lowering the internal inductance is a fundamental issue to address for the elongated plasmas employed within the advanced tokamaks currently under development. In this sense, this paper introduces a lumped parameter numerical model of the tokamak in order to design a novel robust sliding mode controller for the internal inductance using the transformer primary coil as actuator.
Centrifugal Breakout of Magnetically Confined Line-Driven Stellar Winds
ud-Doula, A; Owocki, S P
2006-01-01
We present 2D MHD simulations of the radiatively driven outflow from a rotating hot star with a dipole magnetic field aligned with the star's rotation axis. We focus primarily on a model with moderately rapid rotation (half the critical value), and also a large magnetic confinement parameter, $\\eta_{\\ast} \\equiv B_{\\ast}^2 R_{\\ast}^{2} / \\dot{M} V_{\\infty} = 600$. The magnetic field channels and torques the wind outflow into an equatorial, rigidly rotating disk extending from near the Kepler corotation radius outwards. Even with fine-tuning at lower magnetic confinement, none of the MHD models produce a stable Keplerian disk. Instead, material below the Kepler radius falls back on to the stellar surface, while the strong centrifugal force on material beyond the corotation escape radius stretches the magnetic loops outwards, leading to episodic breakout of mass when the field reconnects. The associated dissipation of magnetic energy heats material to temperatures of nearly $10^{8}$K, high enough to emit hard (...
Numerical computation of self-sustaining magnetically confined electron clouds
International Nuclear Information System (INIS)
The axisymmetrical self-sustaining magnetically confined electron clouds are studied by means of the numerical computational method on the basis of the fluid theory. The electron density distribution, electric potential distribution, drift angular frequency and electron temperature can be calculated with a simplified method in which the near-equilibrium stat approximation is necessary. The results are, in principle, in agreement with the experiments
The Swedish fusion research programme on magnetic confinement 1978
International Nuclear Information System (INIS)
A review is given on the activities and plans for research on plasma physics and controlled fusion at the Royal Institute of Technology in Stockholm, with descriptions and motivations of the research lines being conducted. These activities include investigations on plasma-neutral gas interaction, development of special principles for plasma stabilization, magnetic confinement schemes being based mainly on poloidal fields, as well as the generation, heating, and diagnostics of plasmas being ''impermeable'' to neutral gas. (author)
Path Integral Confined Dirac Fermions in a Constant Magnetic Field
Merdaci, Abdeldjalil; Jellal, Ahmed; CHETOUANI, Lyazid
2014-01-01
We consider Dirac fermion confined in harmonic potential and submitted to a constant magnetic field. The corresponding solutions of the energy spectrum are obtained by using the path integral techniques. For this, we begin by establishing a symmetric global projection, which provides a symmetric form for the Green function. Based on this, we show that it is possible to end up with the propagator of the harmonic oscillator for one charged particle. After some transformations, we derive the nor...
Quark confinement in a random color magnetic ether
International Nuclear Information System (INIS)
It is shown that there is quark confinement (in the sense that Wilson's criterion is satisfied) when the vacuum has a sufficiently fluctuating color magnetic flux PHI through any closed curve. Such a flux satisfies = 0, whereas 2> is nonvanishing and is such that fluctuations in different small regions are uncorrelated. It is argued that a previously proposed quantum liquid model for the QCD vacuum is random in this sense. It is pointed out that an important ingredient in the necessary randomness is that the number of color magnetic flux tubes is not constant. (Auth.)
The Development of RF Heating of Magnetically Confined Deuterium-Tritium Plasmas
International Nuclear Information System (INIS)
The experimental and theoretical development of ion cyclotron radiofrequency heating (ICRF) in toroidal magnetically-confined plasmas recently culminated with the demonstration of ICRF heating of D-T plasmas, first in the Tokamak Fusion Test Reactor (TFTR) and then in the Joint European Torus (JET). Various heating schemes based on the cyclotron resonances between the plasma ions and the applied ICRF waves have been used, including second harmonic tritium, minority deuterium, minority helium-3, mode conversion at the D-T ion-ion hybrid layer, and ion Bernstein wave heating. Second harmonic tritium heating was first shown to be effective in a reactor-grade plasma in TFTR. D-minority heating on JET has led to the achievement of Q = 0.22, the ratio of fusion power produced to RF power input, sustained over a few energy confinement times. In this paper, some of the key building blocks in the development of rf heating of plasmas are reviewed and prospects for the development of advanced methods of plasma control based on the application of rf waves are discussed
The development of RF heating of magnetically confined deuterium-tritium plasmas
International Nuclear Information System (INIS)
The experimental and theoretical development of ion cyclotron radiofrequency heating (ICRF) in toroidal magnetically-confined plasmas recently culminated with the demonstration of ICRF heating of D-T plasmas, first in the Tokamak Fusion Test Reactor (TFTR) and then in the Joint European Torus (JET). Various heating schemes based on the cyclotron resonances between the plasma ions and the applied ICRF waves have been used, including second harmonic tritium, minority deuterium, minority helium-3, mode conversion at the D-T ion-ion hybrid layer, and ion Bernstein wave heating. Second harmonic tritium heating was first shown to be effective in a reactor-grade plasma in TFTR. D-minority heating on JET has led to the achievement of Q=0.22, the ratio of fusion power produced to RF power input, sustained over a few energy confinement times. In this paper, some of the key building blocks in the development of rf heating of plasmas are reviewed and prospects for the development of advanced methods of plasma control based on the application of rf waves are discussed
Czech Academy of Sciences Publication Activity Database
Kovařík, Karel; Ďuran, Ivan; Stöckel, Jan; Adámek, Jiří; Spolaore, M.; Vianello, N.
Prague : MATFYZPRESS, 2014 - (Šafránková, J.; Pavlů, J.), s. 211-214 ISBN 978-80-7378-276-4. - (WDS). [Annual Conference of Doctoral Students – WDS 2014 /23./. Prague (CZ), 03.06.2014-05.06.2014] R&D Projects: GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : U-probe * tokamak * COMPASS * plasma * Langmuir probes Subject RIV: BL - Plasma and Gas Discharge Physics http://www.mff.cuni.cz/veda/konference/wds/proc/pdf14/WDS14_37_f2_Kovarik.pdf
Measurements of temperature and density in magnetic confinement fusion devices
Udintsev, Victor S.
2010-11-01
Controlled thermonuclear fusion can fulfil the demand of mankind to have an inexhaustible source of energy that does not cause any serious environmental pollution. The aim of fusion research is to build a continuously operating reactor in which the energy released by the fusion reactions is sufficiently high to keep the plasma hot and to produce more fusion reactions. The knowledge of the plasma temperature and density, together with the energy confinement time, is therefore very important for the effective control of the self-sustained fusion reactor. Various methods and diagnostics for measurements of the plasma temperature and density in present experimental fusion devices, as well as requirements for the future fusion reactors, will be discussed. A special attention will be given to the temperature and density diagnostics in ITER tokamak, which is presently under construction by several international partners at Cadarache in France. Development of these diagnostics is a major challenge because of severe environment, strict engineering requirements, safety issues and the need for high reliability in the measurements.
Environmental and Economic Assessments of Magnetic and Inertial Confinement Fusion Reactors
International Nuclear Information System (INIS)
Full text: Global warming due to rapid greenhouse gas (GHG) emission is one of the present-day crucial problems, and fusion reactors are expected as abundant electric power generation systems to reduce GHG emission amounts. To search for environment-friendly and economic fusion reactor system, comparative system studies have been done for several magnetic confinement fusion (MCF) reactors, and recently extended to include inertial confinement fusion (ICF) reactors. At first, economic assessment models for MCF reactors including tokamak (TR), helical (HR) and spherical tokamak (ST) systems are described. These MCF reactor designs strongly depend on achievable plasma beta value and magnetic field strength. In the system code we confirmed the advantage of high-beta TR designs in cost of electricity (COE). After wide parameter scans, we obtained the new COE scaling formulas for MCF reactors as functions of electric power (1-3 GW), plant availability (0.65-0.85), normalized beta (3-5) or averaged beta (3-5%), maximum magnetic field strength (10-16 T), thermal efficiency (0.37-0.59) and operation year (20-40 Year). In the case of ICF reactors, fast ignition concept is adopted here. The target gain and driver repetition rate are evaluated assuming driver energy, driver efficiency (∼ 0.075), compression efficiency (∼ 0.05) and heating efficiency (∼ 0.10), which critically determine the fusion core system. The life-cycle CO2 emissions equivalently including methane gas are also evaluated using the input-output table method. High power plant assessment and carbon tax effect on COE are also evaluated, and fusion power plants are compared with other electric power plants. The fusion reactors emit less GHG than fossil fuel thermal power plant. In comparison with fission reactors, the fusion has a disadvantage in COE, but has an advantage in GHG emission. When the carbon tax of around 3,000 yen/t-CO2equi is introduced, the COE of fusion reactor might be at the same level
Thermonuclear ignition in the next generation tokamaks
International Nuclear Information System (INIS)
The extrapolation of experimental rules describing energy confinement and magnetohydrodynamic - stability limits, in known tokamaks, allow to show that stable thermonuclear ignition equilibria should exist in this configuration, if the product aBtx of the dimensions by a magnetic-field power is large enough. Quantitative application of this result to several next-generation tokamak projects show that those kinds of equilibria could exist in such devices, which would also have enough additional heating power to promote an effective accessible ignition
Particle confinement control with resonant magnetic perturbations at TEXTOR
International Nuclear Information System (INIS)
Two very contrary particle confinement stages were obtained at TEXTOR-DED by application of resonant magnetic perturbations. On the one hand a spontaneous build up of the total number of particles Ntot with correlated increase in the particle confinement time τp was observed and on the other hand a controlled decrease of Ntot and τp - the so called stochastic particle pump out is seen. Numerical analysis of the perturbed magnetic field topology shows that both domains can be distinguished by the ratio of short connection length field lines touching a specific resonant flux surface (here the q=5/2 surface) to the complete perturbed layer width. During improved particle confinement, the hyperbolic fixed points (X-points) of the pitch resonant islands are directly connected to the DED target followed by an ≤40% increase in τp. The subsequent increase in the ExB shear rate ΩExB at the q=5/2 surface and a steepening of ∇ne(r) suggests a reduction of the radial particle transport. On the opposite, complete stochastisation of this island chain, i.e. a predominant diffusive field line characteristics, causes a ≤30% decrease of τp with a reduction in ΩExB at the q=5/2 surface and ∇ne(r) indicating enhanced effective outward particle transport.
Massive photons and Dirac monopoles: electric condensate and magnetic confinement
International Nuclear Information System (INIS)
Full text: The main objective of this presentation is to discuss how to generalize the Dirac prescription for the introduction of monopoles when the vector bosons are massive, helping to clarify some misunderstandings found in the literature like the claims that Dirac monopoles and massive photons cannot coexist, that the unphysical Dirac strings would become observable and, consequently, that it would be impossible to consistently derive the Dirac charge quantization condition when the vector bosons are massive. One of the main points involved in this issue regards the fact that the Dirac theory of monopoles was indeed developed in the context of massless vector bosons and its extension to the case of massive photons is not immediate. Another key point refers to the very general observation that a massive photon generates a Meissner effect, which confines magnetic probe sources. Aside with these observations, one must also keep in mind that being unphysical artifacts of a particular formalism, there are no physical processes that could turn the Dirac strings (or more generally, Dirac branes) into observables, since it would violate Elitzur's theorem. This point is in fact a consistency condition that must be always satisfied in order to the formalism be consistent. These basic observations can be gathered together through the use of the so-called Julia-Toulouse approach for condensation of charges and defects Here, the Julia-Toulouse approach is used to argue that massive photons can coexist consistently with Dirac monopoles. The Proca theory is obtained via the Julia-Toulouse approach as a hydrodynamic effective theory describing an electric condensate and the mass of the vector boson is responsible for generating a Meissner effect which confines the magnetic defects in pairs of monopoles-antimonopoles connected by physical open magnetic vortices instead of unphysical Dirac branes. These open vortices are brane invariants corresponding to the physical confining
Vortex confinement by magnetic domains in superconductor-ferromagnet bilayers
Cieplak, Marta Z.; Adamus, Z.; Konczykowski, M.; Zhu, L. Y.; Chien, C. L.; Cheng, X. M.
2013-03-01
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in between to avoid proximity effect. The magnetic domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature the magnetic pinning increases but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth. Supported by Polish NCS grant 2011/01/B/ST3/00462, by the French-Polish Program PICS 2012, by EU grant POIG.01.01.02-00-108/09, and by NSF grants DMR05-20491 and DMR-1053854.
Effect of magnetic perturbations on the 3D MHD self-organization of shaped tokamak plasmas
Bonfiglio, D; Veranda, M; Chacón, L; Escande, D F
2016-01-01
The effect of magnetic perturbations (MPs) on the helical self-organization of shaped tokamak plasmas is discussed in the framework of the nonlinear 3D MHD model. Numerical simulations performed in toroidal geometry with the \\textsc{pixie3d} code [L. Chac\\'on, Phys. Plasmas {\\bf 15}, 056103 (2008)] show that $n=1$ MPs significantly affect the spontaneous quasi-periodic sawtoothing activity of such plasmas. In particular, the mitigation of sawtooth oscillations is induced by $m/n=1/1$ and $2/1$ MPs. These numerical findings provide a confirmation of previous circular tokamak simulations, and are in agreement with tokamak experiments in the RFX-mod and DIII-D devices. Sawtooth mitigation via MPs has also been observed in reversed-field pinch simulations and experiments. The effect of MPs on the stochastization of the edge magnetic field is also discussed.
Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas
Energy Technology Data Exchange (ETDEWEB)
Jardin, S C
2010-09-28
Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.
Stationary shapes of confined rotating magnetic liquid droplets.
Lira, Sérgio A; Miranda, José A; Oliveira, Rafael M
2010-09-01
We study the family of steady shapes which arise when a magnetic liquid droplet is confined in a rotating Hele-Shaw cell and subjected to an azimuthal magnetic field. Two different scenarios are considered: first, the magnetic fluid is assumed to be a Newtonian ferrofluid, and then it is taken as a viscoelastic magnetorheological fluid. The influence of the distinct material properties of the fluids on the ultimate morphology of the emerging stationary patterns is investigated by using a vortex-sheet formalism. Some of these exact steady structures are similar to the advanced time patterns obtained by existing time-evolving numerical simulations of the problem. A weakly nonlinear approach is employed to examine this fact and to gain analytical insight about relevant aspects related to the stability of such exact stationary solutions. PMID:21230182
Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas
International Nuclear Information System (INIS)
Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today's magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today's computers and modern linear and non-linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.
International Nuclear Information System (INIS)
The development of nuclear fusion as an alternative energy source requires the research on magnetically confined, high temperature plasmas. In particular, the quantification of plasma flows in the domain near exposed material surfaces of the plasma container by computer simulations is of key importance, both for guiding interpretation of present fusion experiments and for aiding the ongoing design activities for large future devices such as ITER, W7-X or the DEMO reactor. There is a large number of computational issues related to the physics of hot, fully ionized and magnetized plasmas near surfaces of the vacuum chamber. This thesis is dedicated to one particular such challenge, namely the numerical quantification of self-consistent kinetic neutral gas and plasma fluid flows in very complex 3D (partially chaotic) magnetic fields, in the absence of any common symmetries for plasma and neutral gas dynamics. Such magnetic field configurations are e.g. generated by externally applied magnetic perturbations at the plasma edge, and are of great interest for the control of particle and energy exhausts. In the present thesis the 3D edge plasma and neutral particle transport code EMC3-EIRENE is applied to two distinct configurations of open chaotic magnetic system: at the TEXTOR and DIII-D tokamaks. Improvements of the edge transport model and extensions of the transport code are presented, which have allowed such simulations for the first time for 3D scenarios at DIII-D with ITER similar plasmas. A strong 3D effect of the chaotic magnetic field on the DIII-D edge plasma is found and analyzed in detail. It is found that a pronounced striation pattern of target particle and heat fluxes at DIII-D can only be obtained up to a certain upper limiting level of anomalous cross-field transport. Hence, in comparison to experimental data, these findings allow to narrow down the range of this model parameter. One particular interest at TEXTOR is the achievement of a regime with
Injection, compression and confinement of electrons in a magnetic mirror
International Nuclear Information System (INIS)
A Helmholtz coil configuration has been constructed where the magnetic field can be increased to about 10 kGauss in 20 μsec. Electrons are injected from a hot tantalum filament between two plates across which a potential of about 5 keV is applied. The electric field E is perpendicular to the magnetic field B so that the direction of the E x B drift is radial--into the magnetic mirror. About 1014 electrons were injected and about 1013 electrons were trapped. The initial electron energy was about 5 keV and after compression 500 keV x-rays were observed. The confinement time is very sensitive to vacuum. Confinement times of milliseconds and good compression were observed at vacuum of 5.10-5 torr or less. Above 5.10-5 torr there was no trapping or compression. After a compressed ring of electrons was formed, it was released by a pulse applied to one of the Helmholtz coils that reduced the field. Ejection of the electron ring was observed by x-ray measurements
Observation of a high-confinement regime in a tokamak plasma with ion cyclotron resonance heating
Steinmetz, K.; Noterdaeme, J.-M.; Wagner, F.; Wesner, F.; Bäumler, J.; Becker, G.; Bosch, H. S.; Brambilla, M.; Braun, F.; Brocken, H.; Eberhagen, A.; Fritsch, R.; Fussmann, G.; Gehre, O.; Gernhardt, J.; v. Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Hofmann, J.; Hofmeister, F.; Izvozchikov, A.; Janeschitz, G.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; van Mark, E.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Puri, S.; Rapp, H.; Röhr, H.; Ryter, F.; Schmitter, K.-H.; Schneider, F.; Setzensack, C.; Siller, G.; Smeulders, P.; Söldner, F.; Speth, E.; Steuer, K.-H.; Vollmer, O.; Wedler, H.; Zasche, D.
1987-01-01
The H mode in ion cyclotron-resonance-heated plasmas has been investigated with and without additional neutral beam injection. Ion cyclotron-resonance heating can cause the transition into a high-confinement regime (H mode) in combination with beam heating. The H mode, however, has also been realized-for the first time-with ion cyclotron-resonance heating alone in the D (H)-hydrogen minority scheme at an absorbed rf power of 1.1 MW.
Langmuir-magnetic probe measurements of ELMs and dithering cycles in the EAST tokamak
DEFF Research Database (Denmark)
Yan, Ning; Naulin, Volker; Xu, G. S.;
2014-01-01
Measurements of the dynamical behavior associated with edge localized modes (ELMs) have been carried out in the Experimental Advanced Superconducting Tokamak (EAST) by direct probing near the separatrix and far scrape-off layer (SOL) using electrostatic as well as magnetic probes. Type-III ELMs a...
Plasma vortexes induced by an external rotating helical magnetic perturbation in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Pankratov, I.M. [Institute of Plasma Physics, National Science Center ' Kharkov Institute of Physics and Technology' , Akademicheskaya str., 1, 61108 Kharkov (Ukraine)]. E-mail: pankratov@kipt.kharkov.ua; Omelchenko, A.Ya. [Institute of Plasma Physics, National Science Center ' Kharkov Institute of Physics and Technology' , Akademicheskaya str., 1, 61108 Kharkov (Ukraine); Olshansky, V.V. [Institute of Plasma Physics, National Science Center ' Kharkov Institute of Physics and Technology' , Akademicheskaya str., 1, 61108 Kharkov (Ukraine)
2005-08-01
The occurrence of two or four vortexes per one poloidal perturbation period has been found near the resonant surface as a plasma motion response on the penetration of an external low frequency helical magnetic perturbation in tokamaks. The investigation is carried out on the basis of the two-fluid MHD equations in the linear approximation for the cylindrical model.
Magnetic field measurements using the galvanomagnetic devices on Tore Supra and CASTOR tokamaks
Czech Academy of Sciences Publication Activity Database
Ďuran, Ivan; Hron, Martin; Stöckel, Jan; Sentkerestiová, Jana; Kovařík, Karel; Trosková, Zuzana; Viererbl, L.; Bolshakova, I.; Holyaka, R.; Erashok, V.; Moreau, P.J.; Saint Laurent, F.; Gunn, J. P.
Tarragona: European Physical Society, 2005 - (van Milligen, B.; Hidalgo, C.), P2.076. (29C). ISBN 2-914771-24-X. [EPS Plasma Physics Conference/32nd./. Tarragona (ES), 27.06.2005-01.07.2005] R&D Projects: GA AV ČR KJB100430504 Keywords : tokamak * magnetic field * Hall sensors Subject RIV: BL - Plasma and Gas Discharge Physics
Spin wave quantization in laterally confined magnetic structures (invited)
International Nuclear Information System (INIS)
An overview of the current status of the study of spin wave excitations in arrays of magnetic dots and wires is given. We describe both the status of theory and recent inelastic light scattering experiments addressing the most important issues; the quantization of localized spin waves due to the in-plane confinement of spin waves in elements, dipolar coupling between the quantized modes, and the localization of the modes within rectangular elements due to an inhomogeneous demagnetizing field. [copyright] 2001 American Institute of Physics
Density Functional Theory Studies of Magnetically Confined Fermi Gas
Institute of Scientific and Technical Information of China (English)
陈宇俊; 马红孺
2001-01-01
A theory is developed for magnetically confined Fermi gas at a low temperature based on the density functional theory. The theory is illustrated by the numerical calculation of the density distributions of Fermi atoms 40K with parameters according to DeMarco and Jin's experiment [Science, 285(1999)1703]. Our results are in close agreement with the experiment. To check the theory, we also performed calculations using our theory at a high temperature, which compared very well to the results of the classical limit.
Anomalous transport effects in magnetically-confined plasma columns
International Nuclear Information System (INIS)
The evolution of density structure in a magnetized plasma column is analyzed accounting for anomalous diffusion due to the lower hybrid drift instability. The plasma column is found to be divided into regions of classical, anomalous, and intermediate diffusivity. The bulk behavior, described in terms of radial confinement time, depends most sensitively upon the particle line density (ion/cm). For broad plasmas (large line density), the transport is characteristic of classical diffusion, and for slender plasmas (small line density) the transport is characteristic of anomalous diffusion. For intermediate line densities, the transport undertakes a rapid transition from classical to anomalous. Correlations between the theoretical results and past experiments are described
Test particle calculations for the Texas experimental tokamak with resonant magnetic fields
International Nuclear Information System (INIS)
This paper presents a simple test particle model that attempts to describe particle motion in the presence of intrinsic electrostatic fluctuations in a prescribed tokamak magnetic field. In particular, magnetic field configurations that include externally produced magnetic islands and stochastic regions are considered. The resulting test particle transport is compared with the predictions of analytic models and with the experimentally measured electron heat and particle transport on the Texas Experimental Tokamak (TEXT). Agreement between the test particle results and applicable analytic theories is found. However, there is only partial agreement with the experimental results, and possible reasons for the discrepancies are explored. Good agreement is found between predicted and measured spatially asymmetric particle distributions. The particle collection efficiency of an apertured limiter inside a magnetic island (an intra-island pump limiter) is discussed
International Nuclear Information System (INIS)
Up to now the direct measurement of the magnetic fluctuations in the core of tokamak plasmas has been impossible. According to various turbulence models, the estimated level of B/B lies between 10-6 (residual magnetic fluctuations due to drift wave i.e. O(βn/n) where β is the toroidal beta) and 10-4 (obtained assuming that the heat transport is only due to magnetic turbulence). We describe in this paper a tentative diagnostic to measure these fluctuations. It is based on the cross polarization scattering: Magnetic fluctuations scatter an incident electromagnetic wave with a change in polarization. In section II the basic principle of the diagnostic is explained. In section III the experimental set up is described. It will be tested on the Tore Supra Tokamak at the end of 1990. (author) 2 refs., 2 figs
Magnetic properties of electrons confined in an anisotropic cylindrical potential
International Nuclear Information System (INIS)
In the present paper a theoretical model, describing the effects of external electric and magnetic fields on an electron confined in an anisotropic parabolic potential, is considered. The exact wave functions are used to calculate electron current and orbital magnetic dipole momentum for the single electron. Exact expressions, giving the force and energy of the dipole–dipole interaction, are also determined. Further, the system is coupled to a heat bath, and mean values and fluctuations of the magnetic dipole momentum, utilizing the canonical ensemble are calculated. Influences of the temperature, as well as the external magnetic field, expressed via the Larmor frequency are analyzed. We also include the dependencies of the magnetic dipole momentum and its fluctuations on the effective mass of the electron, considering some experimental values for low-dimensional systems, that are extensively studied for various applications in electronics. Our results suggest that the average momentum or its fluctuations are strongly related to the effective mass of the electron. Having on mind that parabolically shaped potentials have very wide area of application in the low-dimensional systems, such as quantum dots and rings, carbon nanotubes, we believe that the proposed model and the consequent analysis is of general importance, since it offers exact analytical approach
Fast IR diodes thermometer for tokamak
International Nuclear Information System (INIS)
A 30 channel fast IR pyrometry array has been constructed for tokamak, which has 0.5 μs time response, 10 mm diameter spatial resolution and 5 degree C temperature resolution. The temperature measuring range is from 250 degree C to 1200 degree C. The two dimensional temperature profiles of the first wall during both major and minor disruptions can be measured with an accuracy of about 1% measuring temperature, which is adequate for tokamak experiments. This gives a very useful tool for the disruption study, especially for the divertor physics and edge heat flux research on tokamak and other magnetic confinement devices
International Nuclear Information System (INIS)
In this paper, the impact of momentum and energy conservation of the collision operator in the kinetic description for Resonant Magnetic Perturbations (RMPs) in a tokamak is studied. The particle conserving differential collision operator of Ornstein-Uhlenbeck type is supplemented with integral parts such that energy and momentum are conserved. The application to RMP penetration in a tokamak shows that energy conservation in the electron collision operator is important for the quantitative description of plasma shielding effects at the resonant surface. On the other hand, momentum conservation in the ion collision operator does not significantly change the results
Total magnetic reconnection during a tokamak major disruption
International Nuclear Information System (INIS)
The safety factor within a tokamak plasma has been measured during a major disruption. During the disruption, the central safety factor jumps from below one to above one, while the total current is unchanged. This implies that total reconnection has occurred. This observation is in contract to the absence of total reconnection observed during a sawtooth oscillation in the same device. 11 refs., 6 figs
Loss of confinement following a sawtooth internal disruption in PBX tokamak
International Nuclear Information System (INIS)
Some bean-shaped plasmas heated by neutral beam injection lose a large amount of energy (δβ/sub p perpendicular//β/sub p perpendicular/ ≤ 20%) within a short period (0.3 to 6ms) following a sawtooth internal disruption, indicating a momentary worsening of the confinement. The most severe (δβ/sub p perpendicular//β/sub p perpendicular/ > 20%) events lead to discharge termination. The internal disruptions in the PBX plasmas often have an unusually large inversion radius, up to 75% of the plasma half-width
Reactions between NO/+/ and metal atoms using magnetically confined afterglows
Lo, H. H.; Clendenning, L. M.; Fite, W. L.
1977-01-01
A new method of studying thermal energy ion-neutral collision processes involving nongaseous neutral atoms is described. A long magnetic field produced by a solenoid in a vacuum chamber confines a thermal-energy plasma generated by photoionization of gas at very low pressure. As the plasma moves toward the end of the field, it is crossed by a metal atom beam. Ionic products of ion-atom reactions are trapped by the field and both the reactant and product ions move to the end of the magnetic field where they are detected by a quadrupole mass filter. The cross sections for charge transfer between NO(+) and Na, Mg, Ca, and Sr and that for rearrangement between NO(+) and Ca have been obtained. The charge-transfer reaction is found strongly dominant over the rearrangement reaction that forms metallic oxide ions.
Design study of superconducting poloidal magnets for a tokamak experimental fusion reactor
International Nuclear Information System (INIS)
Design of superconducting poloidal magnets for a tokamak experimental fusion reactor has been studied. The purpose is to reveal engineering problems of poloidal magnets. Electrical insulation at liquid helium temperature, fatigue of reinforcement materials of the windings due to repeated electromagnetic forces, construction of FRP liquid helium containers and transfer loss of liquid helium are found to be especially important. The schedule of R and D is also presented. (auth.)
The optimization of resonant magnetic perturbation spectra for the COMPASS tokamak
Czech Academy of Sciences Publication Activity Database
Cahyna, Pavel; Pánek, Radomír; Fuchs, Vladimír; Krlín, Ladislav; Bécoulet, M.; Nardon, E.; Huysmans, G.
2009-01-01
Roč. 49, č. 5 (2009), 055024 1-055024 7. ISSN 0029-5515. [IAEA Fusion Energy Conference/22nd./. Geneva, 13.10.2008-18.10.2008] Institutional research plan: CEZ:AV0Z20430508 Keywords : resonant magnetic perturbations * ELM control * magnetic islands * saddle coils * COMPASS tokamak Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.270, year: 2009 http://dx.doi.org/10.1088/0029-5515/49/5/055024
Safety analysis of superconducting toroidal field magnet for tokamak experimental fusion reactor
International Nuclear Information System (INIS)
Safety analysis of the superconducting toroidal field magnet for a Tokamak experimental fusion reactor has been carried out. Works were accident classification, FMEA and FTA analyses, coil stability and quench behavior calculations, failure detection and coil protection system designs, structure analysis, fracture and fatigue studies, and earthquake response analysis. Accident analysis of cryostat and refrigeration system was also performed. The objective of this work is to reveal technological problems of the toroidal field magnet by safety analysis. (author)
Attainment of high confinement in neutral beam heated divertor discharges in the PDX tokamak
International Nuclear Information System (INIS)
The PDX divertor configuration has recently been converted from an open to a closed geometry to inhibit the return of neutral gas from the divertor region to the main chamber. Since then, operation in a regime with high energy confinement in neutral beam heated discharges (ASDEX H-mode) has been routine over a wide range of operating conditions. These H-mode discharges are characterized by a sudden drop in divertor density and H/sub α/ emission and a spontaneous rise in main chamber plasma density during neutral beam injection. The confinement time is found to scale nearly linearly with plasma current, but it can be degraded due to either the presence of edge instabilities or heavy gas puffing. Detailed Thomson scattering temperature profiles show high values of Te near the plasma edge (approx. 450 eV) with sharp radial gradients (approx. 400 eV/cm) near the separatrix. Density profiles are broad and also exhibit steep gradients close to the separatrix
3D-MAPTOR Code for Computation of Magnetic Fields in Tokamaks
International Nuclear Information System (INIS)
Full text: A 3D code has been developed in order to simulate the magnetic field lines in tokamaks, in two versions. In the first one, the toroidal magnetic field can be obtained from the individual fields of circular coils arranged around the torus, or alternatively, as a ripple-less field. The poloidal field is provided by a given toroidal current density profile. In an upgraded version, rectangular toroidal field coils and D-shaped plasma cross sections have been included, in order to aid in the design of spherical tokamaks. Proposing initial conditions for magnetic filed lines, they are integrated along the toroidal angle coordinate, and Poincare maps can be obtained at any desired cross section plane along the toroidal coordinate. The evolution of the field lines is also monitored from above, so the ripple due to the toroidal field coils can be appreciated. The effects of loss of axisymmetry, either originated by ripples, or by additional external coils, such as an inner coil with tilted circular loops, can therefore be studied. This is useful for the study of breaking-up of external surfaces, as in the case of ergodic divertors. The code can also be used in order to reconstruct the evolution of the plasma column, using the experimental signals of tokamak discharges. In the latter case, the results have been compared with tomographic results of the ISTTOK tokamak. (author)
Energy confinement and magnetic field generation in the SSPX spheromak
Energy Technology Data Exchange (ETDEWEB)
Hudson, B; McLean, H S; Wood, R D; Hooper, E B; Hill, D N; Jayakumar, J; Moller, J; Romero-Talamas, C; Casper, T A; LoDestro, L L; Pearlstein, L D; Johnson, III, J A; Mezonlin, E
2008-02-11
The Sustained Spheromak Physics Experiment (SSPX) [E.B. Hooper, et. al., Nuclear Fusion, Vol. 39, No. 7] explores the physics of efficient magnetic field buildup and energy confinement, both essential parts of advancing the spheromak concept. Extending the spheromak formation phase increases the efficiency of magnetic field generation with the maximum edge magnetic field for a given injector current (B/I) from 0.65 T/MA previously to 0.9 T/MA. We have achieved the highest electron temperatures (T{sub e}) recorded for a spheromak with T{sub e} > 500 eV, toroidal magnetic field {approx}1 T and toroidal current ({approx}1 MA) [R.D. Wood, D.N. Hill, H.S. McLean, E.B. Hooper, B.F. Hudson, J.M. Moller, 'Improved magnetic field generation efficiency and higher temperature spheromak plasmas', submitted to Physical Review Letters]. Extending the sustainment phase to > 8 ms extends the period of low magnetic fluctuations (< 1 %) by 50%. The NIMROD 3-D resistive MHD code [C.R. Sovinec, T.A. Gianakon, E.D. Held, S.E. Kruger and D.D. Schnack, The NIMROD Team, Phys. Plasmas 10, 1727 (2003)] reproduces the observed flux amplification {Psi}{sub pol}/{Psi}{sub gun}. Successive gun pulses are demonstrated to maintain the magnetic field in a quasi-steady state against resistive decay. Initial measurements of neutral particle flux in multi-pulse operation show charge-exchange power loss < 1% of gun input power and dominantly collisional majority ion heating. The evolution of electron temperature shows a distinct and robust feature of spheromak formation: a hollow-to-peaked T{sub e}(r) associated with q {approx} 1/2.
On the account of the nonsteady-state effect in definition of the energy confinement time in tokamak
International Nuclear Information System (INIS)
Essential updating of the system for electromagnetic diagnostics of plasma parameters and of the system of acquisition has enabled to take account of the effect of nonsteady-state of Ip plasma current radial profile, its value and W saved energy on the determination of τE based on the diamagnetic measurements and to study rapid processes occurring at L-H transition. Paper presents formula to calculate time of the energy confinement. The value of L total inductance of plasma pinch was determined on the of βJ + Ii/2 value where βJ - relation between gas-kinetic pressure and pressure of poloidal magnetic field, Ii - internal inductance. The account of nonsteady-state at determination of τE energy confinement time based on diamagnetic measurements applies the correction up to 50%
Cryogenic aspects of a demountable toroidal field magnet system for tokamak-type fusion reactors
International Nuclear Information System (INIS)
An alternative TF coil concept which should avoid the difficulties of maintenance and repair is termed the ''demountable externally anchored low stress'' (IDEALS) magnet system and is intended to provide easier coil installation for reactor construction, as well as improved accessibility for reactor maintenance and repair. This magnet appears to be the most practical and economical method for tokamak TF magnet systems. It may also be applied to other large superconducting magnet systems. The penalty of the increased refrigeration due to coil supports and high-current leads appears to be quite acceptable
Turbulence and transport in enhanced confinement regimes of tokamaks: Simulation and theory
International Nuclear Information System (INIS)
An integrated program of theory and computation has been developed to understand the physics responsible for the favorable confinement trends exhibited by, for example, enhanced reversed shear (ERS) plasmas in TFTR and DIII-D. This paper reports on (1) the quantitative assessment of ExB shear suppression of turbulence by comparison of the linear growth rate calculated from the gyrofluid/comprehensive kinetic codes and the experimentally measured shearing rate in TFTR ERS plasmas; (2) the first self-consistent nonlinear demonstration of ion temperature gradient turbulence reduction due to angle Pi driven ExB shear by the global gyrokinetic simulation; (3) a revised neoclassical analysis and gyrokinetic particle simulation results in agreement with trends in ERS plasmas; (4) Shafranov shift induced stabilization of trapped electron mode in ERS plasmas calculated by the gyrofluid code; and (5) new nonlinear gyrokinetic equations for turbulence in core transport barriers
International Nuclear Information System (INIS)
A set of in-vessel saddle coils called dynamic resonant magnetic perturbation (DRMP) for generating rotating resonant magnetic perturbations has recently been constructed on the J-TEXT tokamak. The phenomenon of tearing mode locking to DRMP and rotating together with the DRMP field has been observed. There is an apparent decrease of the island width during the locking and unlocking procedure. Similar results are obtained in the numerical simulation. (brief communication)
International Nuclear Information System (INIS)
This work is devoted to the study and optimization of the Ion Cyclotron Wall Conditioning (ICWC) technique. ICWC, operated in presence of the toroidal magnetic field, makes use of four main tokamak systems: the ICRF antennas to initiate and sustain the conditioning discharge, the gas injection valves to provide the discharge gas, the machine pumps to remove the wall desorbed particles, and the poloidal magnetic field system to optimize the discharge homogeneity. Additionally neutral gas and plasma diagnostics are required to monitor the discharge and the conditioning efficiency. In chapter 2 a general overview on ICWC is given. Chapter 3 treats the ICRF discharge homogeneity and the confinement properties of the employed magnetic field. In the first part we will discuss experimental facts on plasma homogeneity, and how experimental optimization led to its improvement. In the second part of the chapter the confinement properties of a partially ionized plasma in a toroidal magnetic field configuration with additional small vertical component are discussed. Chapter 4 gives an overview of experimental results on the efficiency of ICWC, obtained on TORE SUPRA, TEXTOR, JET and ASDEX Upgrade. In chapter 5 a 0D kinetic description of hydrogen-helium RF plasmas is outlined. The model, describing the evolution of ICRF plasmas from discharge initiation to the (quasi) steady state plasma stage, is developed to obtain insight on ICRF plasma parameters, particle fluxes to the walls and the main collisional processes. Chapter 6 presents a minimum structure for a 0D reservoir model of the wall to investigate in deeper detail the ICWC plasma wall interaction during isotopic exchange experiments. The hypothesis used to build up the wall model is that the same model structure should be able to describe the wall behavior during normal plasmas and conditioning procedures. Chapter 7 extrapolates the results to the envisaged application of ICWC on ITER
Benchmarking atomic physics models for magnetically confined fusion plasma physics experiments
International Nuclear Information System (INIS)
In present magnetically confined fusion devices, high and intermediate Z impurities are either puffed into the plasma for divertor radiative cooling experiments or are sputtered from the high Z plasma facing armor. The beneficial cooling of the edge as well as the detrimental radiative losses from the core of these impurities can be properly understood only if the atomic physics used in the modeling of the cooling curves is very accurate. To this end, a comprehensive experimental and theoretical analysis of some relevant impurities is undertaken. Gases (Ne, Ar, Kr, and Xe) are puffed and nongases are introduced through laser ablation into the FTU tokamak plasma. The charge state distributions and total density of these impurities are determined from spatial scans of several photometrically calibrated vacuum ultraviolet and x-ray spectrographs (3 - 1600 Angstrom), the multiple ionization state transport code transport code (MIST) and a collisional radiative model. The radiative power losses are measured with bolometery, and the emissivity profiles were measured by a visible bremsstrahlung array. The ionization balance, excitation physics, and the radiative cooling curves are computed from the Hebrew University Lawrence Livermore atomic code (HULLAC) and are benchmarked by these experiments. (Supported by U.S. DOE Grant No. DE-FG02-86ER53214 at JHU and Contract No. W-7405-ENG-48 at LLNL.) copyright 1999 American Institute of Physics
Benchmarking atomic physics models for magnetically confined fusion plasma physics experiments
May, M. J.; Finkenthal, M.; Soukhanovskii, V.; Stutman, D.; Moos, H. W.; Pacella, D.; Mazzitelli, G.; Fournier, K.; Goldstein, W.; Gregory, B.
1999-01-01
In present magnetically confined fusion devices, high and intermediate Z impurities are either puffed into the plasma for divertor radiative cooling experiments or are sputtered from the high Z plasma facing armor. The beneficial cooling of the edge as well as the detrimental radiative losses from the core of these impurities can be properly understood only if the atomic physics used in the modeling of the cooling curves is very accurate. To this end, a comprehensive experimental and theoretical analysis of some relevant impurities is undertaken. Gases (Ne, Ar, Kr, and Xe) are puffed and nongases are introduced through laser ablation into the FTU tokamak plasma. The charge state distributions and total density of these impurities are determined from spatial scans of several photometrically calibrated vacuum ultraviolet and x-ray spectrographs (3-1600 Å), the multiple ionization state transport code transport code (MIST) and a collisional radiative model. The radiative power losses are measured with bolometery, and the emissivity profiles were measured by a visible bremsstrahlung array. The ionization balance, excitation physics, and the radiative cooling curves are computed from the Hebrew University Lawrence Livermore atomic code (HULLAC) and are benchmarked by these experiments. (Supported by U.S. DOE Grant No. DE-FG02-86ER53214 at JHU and Contract No. W-7405-ENG-48 at LLNL.)
International Nuclear Information System (INIS)
The first edition of John Wesson's book on tokamaks, published in 1987, established itself as essential reading for researchers in the field of magnetic confinement fusion: it was an excellent introduction for students to tokamak physics and also a valuable reference work for the more experienced. The second edition, published in 1997, has been completely rewritten and substantially enlarged (680 pages compared with 300). The new edition maintains the aim of providing a simple introduction to basic tokamak physics, but also includes discussion of the substantial advances in fusion research during the past decade. The new book, like its predecessor, is well written and commendable for its clarity and accuracy. In fact many of the chapters are written by a series of co-authors bringing the benefits of a wide range of expertise but, by careful editing, Wesson has maintained a uniformity of style and presentation. The chapter headings and coverage for the most part remain the same - but are expanded considerably and brought up to date. The most substantial change is that the single concluding chapter in the first edition on 'Experiments' has been replaced by three chapters: 'Tokamak experiments' which deals with some of the earlier key experiments plus a selection of recent small and medium-sized devices, 'Large experiments' which gives an excellent summary of the main results from the four large tokamaks - TFTR, JET, JT60/JT60U and DIII-D, and 'The future' which gives a very short (possibly too short in my opinion) account of reactors and ITER. This is an excellent book, which I strongly recommend should have a place - on the desk rather than in the bookshelf - of researchers in magnetic confinement fusion. (book review)
International Nuclear Information System (INIS)
An overall review of the tokamak program is given with particular emphasis upon developments over the past five years in the theoretical and experimental elements of the program. A summary of the key operating parameters for the principal tokamaks throughout the world is given. Also discussed are key issues in plasma confinement, plasma heating, and tokamak design
Stability of magnetic modes in tokamaks; Stabilite des modes magnetiques dans les tokamaks
Energy Technology Data Exchange (ETDEWEB)
Zabiego, M.
1994-06-01
A theoretical study is carried out concerning two experimental topics: stabilization, by a suprathermal population, of the mode ``m=1, n=1`` which induces the sawtooth effect (modelling the role of suprathermal particles in the stabilization); stability, in the non linear regime, of the magnetic islands involved in magnetic turbulence problems (micro-tearing) and in disruption phenomena (tearing), and the effects of diamagnetism, excitation threshold and saturation levels. 45 figs., 97 refs.
World survey of magnetic mirror confinement research facilities
International Nuclear Information System (INIS)
A common format to present the information on each project has been adopted. Projects are selected for inclusion in this document based on knowledge of their direct relevance or contribution to the magnetic mirror confinement program. The information on each project was first compiled in draft form from published literature and reports available. The draft material was then sent to key individuals associated with each project, with the original source of information identified, to solicit their additions and corrections. The responses were then reviewed and discrepencies with previously published information clarified through further consultations. The information was then incorporated into this document with a revision date to reflect the state of currency of the information
Path Integral Confined Dirac Fermions in a Constant Magnetic Field
Merdaci, Abdeldjalil; Chetouani, Lyazid
2014-01-01
We consider Dirac fermion confined in harmonic potential and submitted to a constant magnetic field. The corresponding solutions of the energy spectrum are obtained by using the path integral techniques. For this, we begin by establishing a symmetric global projection, which provides a symmetric form for the Green function. Based on this, we show that it is possible to end up with the propagator of the harmonic oscillator for one charged particle. After some transformations, we derive the normalized wave functions and the eigenvalues in terms of different physical parameters and quantum numbers. By interchanging quantum numbers, we show that our solutions possed interesting properties. The density of current and the non-relativistic limit are analyzed where different conclusions are obtained.
Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas
International Nuclear Information System (INIS)
Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.
Passive Spectroscopic Diagnostics for Magnetically-confined Fusion Plasmas
Energy Technology Data Exchange (ETDEWEB)
Stratton, B. C.; Biter, M.; Hill, K. W.; Hillis, D. L.; Hogan, J. T.
2007-07-18
Spectroscopy of radiation emitted by impurities and hydrogen isotopes plays an important role in the study of magnetically-confined fusion plasmas, both in determining the effects of impurities on plasma behavior and in measurements of plasma parameters such as electron and ion temperatures and densities, particle transport, and particle influx rates. This paper reviews spectroscopic diagnostics of plasma radiation that are excited by collisional processes in the plasma, which are termed 'passive' spectroscopic diagnostics to distinguish them from 'active' spectroscopic diagnostics involving injected particle and laser beams. A brief overview of the ionization balance in hot plasmas and the relevant line and continuum radiation excitation mechanisms is given. Instrumentation in the soft X-ray, vacuum ultraviolet, ultraviolet, visible, and near-infrared regions of the spectrum is described and examples of measurements are given. Paths for further development of these measurements and issues for their implementation in a burning plasma environment are discussed.
Aledda, Raffaele
2015-01-01
The nuclear fusion arises as the unique clean energy source capable to meet the energy needs of the entire world in the future. On present days, several experimental fusion devices are operating to optimize the fusion process, confining the plasma by means of magnetic fields. The goal of plasma confined in a magnetic field can be achieved by linear cylindrical configurations or toroidal configurations, e.g., stellarator, reverse field pinch, or tokamak. Among the explored magnetic confinement...
Magnetic sensorless control of plasma position and shape in a tokamak
International Nuclear Information System (INIS)
Magnetic sensorless sensing and control experiments of the plasma horizontal position have been carried out in the superconducting tokamak HT-7. The sensing is made focusing on the ripple frequency component of the power supply with thyristor and directly from them without time integration. There is no drift problem of integrator of magnetic sensors. Two kinds of control experiments were carried out, to keep the position constant and swing the position in a triangular waveform. And magnetic sensorless sensing of plasma shape is discussed. (author)
Effects of the magnetic equilibrium on gyrokinetic simulations of tokamak microinstabilities
International Nuclear Information System (INIS)
The general geometry of the experimental tokamak magnetic equilibrium is implemented in the global gyrokinetic simulation code GEM. Compared to the general geometry, the well used Miller parameterization of the magnetic equilibrium is a good approximation in the core region and up to the top of the pedestal. Linear simulations indicate that results with the two geometries agree for r/a ≤ 0.9. However, in the edge region, the instabilities are sensitive to the magnetic equilibrium in both the L-mode and the H-mode plasmas. A small variation of the plasma shaping parameters leads to large changes to the edge instability
Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks
Energy Technology Data Exchange (ETDEWEB)
Peysson, Y.; Arslanbekov, R.; Basiuk, V.; Carrasco, J.; Litaudon, X.; Moreau, D. [Association Euratom-CEA, Centre d`Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Bizarro, J.P. [Instituto Superior Tecnico, Lisbon (Portugal). Lab. de Quimica Organica
1996-01-01
Using ray-tracing, a detailed investigation of the lower hybrid (LH) wave propagation in presence of toroidal magnetic field ripple is presented. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the Tore Supra tokamak. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations, such as non-thermal Bremsstrahlung emission, current profile, ripple-induced power losses in local magnetic mirrors, when plasma conditions correspond to the ` `few passes` regime. (author). 47 refs.
Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks
International Nuclear Information System (INIS)
Using ray-tracing, a detailed investigation of the lower hybrid (LH) wave propagation in presence of toroidal magnetic field ripple is presented. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the Tore Supra tokamak. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations, such as non-thermal Bremsstrahlung emission, current profile, ripple-induced power losses in local magnetic mirrors, when plasma conditions correspond to the ' 'few passes' regime. (author)
Determination of the plasma column shape in the Tokamak Novillo cross section by magnetic probes
International Nuclear Information System (INIS)
The determination of plasma cross section shape in Tokamaks is an important diagnostic method for equilibrium conditions analysis. In this work, it is obtained a time dependent variation of the plasma column cross section in Novillo Tokamak. The experimental method is based on using one magnetic probe, which is installed inside of the vacuum vessel in a 1 mm. wall thickness stainless steel tube, in the protected region of the limiter shadow. The plasma column cross section is determined measuring the poloidal magnetic field produced by the plasma current. This method, now running for determining the plasma column shape, requires the measurement of magnetic present field outside plasma column. The measurements are carried out from a set of small coils, which are located inside the vacuum chamber in the radial and poloidal direction, so we can measure magnetic field with no current attenuations produced by the penetration time of the stainless steel vacuum chamber. The magnetic probe detect a real time variation of magnetic flux passing through them. In order to obtain the magnetic field values, it is required that the electric signals coming from the magnetic probe be integrated, this operation is carried out by active circuits located between the probe signal and one oscilloscope. The integrated signals can be exhibited photographed on the oscilloscope display. (Author)
An Overview of Plasma Confinement in Toroidal Systems
Dini, Fatemeh; Baghdadi, Reza; Amrollahi, Reza; Khorasani, Sina
2009-01-01
This overview presents a tutorial introduction to the theory of magnetic plasma confinement in toroidal confinement systems with particular emphasis on axisymmetric equilibrium geometries, and tokamaks. The discussion covers three important aspects of plasma physics: Equilibrium, Stability, and Transport. The section on equilibrium will go through an introduction to ideal magnetohydrodynamics, curvilinear system of coordinates, flux coordinates, extensions to axisymmetric equilibrium, Grad-Sh...
Simulation of transition dynamics to high confinement in fusion plasmas
DEFF Research Database (Denmark)
Nielsen, Anders Henry; Xu, G. S.; Madsen, Jens;
2015-01-01
The transition dynamics from the low (L) to the high (H) confinement mode in magnetically confined plasmas is investigated using a first-principles four-field fluid model. Numerical results are in agreement with measurements from the Experimental Advanced Superconducting Tokamak - EAST. Particula...... highly relevant for developing predictive models of the transition, essential for understanding and optimizing future fusion power reactors....
International Nuclear Information System (INIS)
The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnostic signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and the equilibrium reconstruction are presented
Schmitt, J C; Bialek, J; Lazerson, S; Majeski, R
2014-11-01
The Lithium Tokamak eXperiment is a spherical tokamak with a close-fitting low-recycling wall composed of thin lithium layers evaporated onto a stainless steel-lined copper shell. Long-lived non-axisymmetric eddy currents are induced in the shell and vacuum vessel by transient plasma and coil currents and these eddy currents influence both the plasma and the magnetic diagnostic signals that are used as constraints for equilibrium reconstruction. A newly installed set of re-entrant magnetic diagnostics and internal saddle flux loops, compatible with high-temperatures and lithium environments, is discussed. Details of the axisymmetric (2D) and non-axisymmetric (3D) treatments of the eddy currents and the equilibrium reconstruction are presented. PMID:25430382
A MHD invariant with effects on the confinement regimes in Tokamak
Spineanu, Florin
2015-01-01
Fundamental Lagrangian, frozen-in and topological invariants can be useful to explain systematic connections between plasma parameters. At high plasma temperature the dissipation is small and the robust invariances are manifested. We invoke a frozen-in invariant which is an extension of the Ertel's theorem and connects the vorticity of the large scale motions with the profile of the safety factor and of particle density. Assuming ergodicity of the small scale turbulence we consider the approximative preservation of the invariant for changes of the vorticity in an annular region of finite radial extension (i.e. poloidal rotation). We find that the ionization-induced rotation triggered by a pellet requires a reversed-$q$ profile. In the $H$-mode, the invariance requires a accumulation of the current density in the rotation layer. Then this becomes a vorticity-current sheet which may explain experimental observations related to the penetration of the Resonant Magnetic Perturbation and the filamentation during th...
Nonneutralized charge effects on tokamak edge magnetohydrodynamic stability
Zheng, Linjin; Horton, W.; Miura, H.; Shi, T. H.; Wang, H. Q.
2016-08-01
Owing to the large ion orbits, excessive electrons can accumulate at tokamak edge. We find that the nonneutralized electrons at tokamak edge can contribute an electric compressive stress in the direction parallel to magnetic field by their mutual repulsive force. By extending the Chew-Goldburger-Low theory (Chew et al., 1956 [13]), it is shown that this newly recognized compressive stress can significantly change the plasma average magnetic well, so that a stabilization of magnetohydrodynamic modes in the pedestal can result. This linear stability regime helps to explain why in certain parameter regimes the tokamak high confinement can be rather quiet as observed experimentally.
Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak
Czech Academy of Sciences Publication Activity Database
Ďuran, Ivan; Hronová-Bilyková, Olena; Stöckel, Jan; Sentkerestiová, J.; Havlíček, Josef
2008-01-01
Roč. 79, č. 10 (2008), 10F123-10F123. ISSN 0034-6748. [Topical Conference on High-Temperature Plasma Diagnostics/17th./. Albuquerque, 11.05.2008-15.05.2008] R&D Projects: GA MPO 2A-1TP1/101 Institutional research plan: CEZ:AV0Z20430508 Keywords : Galvanomagnetic Sensor * Fusion Reactor * Magnetic Diagnostics * CASTOR tokamak Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.738, year: 2008
A comparison of intermittency in neutral fluids and magnetically confined plasmas
International Nuclear Information System (INIS)
Intermittency in the scrape-off layer (SOL) region of magnetically confined plasma and velocity intermittency of helium gas are compared from the aspect of global and local multifractal properties. The analysis reveals subtle differences in the global aspect between turbulent fluctuations of confined plasmas and neutral fluid as well as differences among magnetically confined devices themselves especially with respect to energy cascade mechanisms in the corresponding systems. Analysis of local multifractal characteristics reveals even more pronounced differences. (author)
Kikuchi, Y; de Bock, M. F. M.; Reiser, D.; Wolf, R C; Finken, K. H.; Jakubowski, M W.; R. Jaspers; Koslowski, H. R.; Krämer-Flecken, A; Lehnen, M.; Liang, Y.; Matsunaga, G.
2006-01-01
The magnetic field penetration process into a magnetized plasma is of basic interest both for plasma physics and astrophysics. In this context special measurements on the field penetration and field amplification are performed by a Hall probe on the dynamic ergodic divertor (DED) on the TEXTOR tokamak and the data are interpreted by a two-fluid plasma model. It is observed that the growth of the forced magnetic reconnection by the rotating DED field is accompanied by a change of the plasma fl...
Effects of Current on Behaviors of Saturated Magnetic Island in Tokamak
International Nuclear Information System (INIS)
Plasma current density gradient is known to be one of crucial parameters triggering neoclassical tearing mode in a tokamak plasma. This kind of instability can lead to a formation of magnetic islands, which results in the reduction of plasma pressure and, consequently the degradation of fusion performance. The ISLAND module, developed for determining multiple saturated island width due to different unstable modes, is used in this work. This calculation is based on a quasi-linear theory approach and can include the effect of the bootstrap cur- rent. Both geometry of tokamak and the operation conditions such as magnetic field strength, current and pressure profile are used as initial inputs. The different unstable modes (called m/n, where m and n are the poloidal and toroidal mode number, respectively) are considered. It is found in this work that the mode m/n =2/1 is found to produce the largest saturated island width in the JET and DIIID tokamaks, which agrees with what observed in those to- kamaks. The saturated width of this mode trends to get larger when the gradient of current between the magnetic axis and the mode rational surface increase. The detailed results will be investigated and discussed.
International Nuclear Information System (INIS)
The economic prospects of the tokamak are reviewed briefly and found to be favorable - if the size of ignited tokamak plasmas can be kept small and appropriate auxiliary systems can be developed. The main objectives of the Princeton Plasma Physics Laboratory tokamak program are: (1) exploration of the physics of high-temperature toroidal confinement, in TFTR; (2) maximization of the tokamak beta value, in PBX; (3) development of reactor-relevant rf techniques, in PLT
International Nuclear Information System (INIS)
This thesis is devoted to two studies of low-frequency turbulence in toroidally confined plasma. Low-frequency turbulence is believed to play an important role in anomalous transport in toroidal confinement devices. The first study pertains the development of an analytic theory of ion-temperature-gradient-driven turbulence in tokamaks. Energy conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion temperature gradient driven turbulence. Corrections to mixing length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity is derived and is found to be consistent with experimentally-deduced ion thermal diffusivities. The associated electron thermal diffusivity, particle and heat-pinch velocities are also calculated. The second study is devoted to the role of multiple helicity nonlinear interactions of tearing modes and dynamics of magnetic relaxation in a high-temperature current carrying plasma. To extend the resistive MHD theory of magnetic fluctuations and dynamo activity observed in the reversed field pinch, the fluid equations for high temperature regime are derived and basic nonlinear interaction mechanism and the effects of diamagnetic corrections to the MHD turbulence theory are studied for the case of fully developed, densely packed turbulence
Cui, Z Q; Chen, Z J; Xie, X F; Peng, X Y; Hu, Z M; Du, T F; Ge, L J; Zhang, X; Yuan, X; Xia, Z W; Hu, L Q; Zhong, G Q; Lin, S Y; Wan, B N; Fan, T S; Chen, J X; Li, X Q; Zhang, G H
2014-11-01
The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G. PMID:25430242
International Nuclear Information System (INIS)
The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G
Cui, Z. Q.; Chen, Z. J.; Xie, X. F.; Peng, X. Y.; Hu, Z. M.; Du, T. F.; Ge, L. J.; Zhang, X.; Yuan, X.; Xia, Z. W.; Hu, L. Q.; Zhong, G. Q.; Lin, S. Y.; Wan, B. N.; Fan, T. S.; Chen, J. X.; Li, X. Q.; Zhang, G. H.
2014-11-01
The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.
Dynamic effects of rotating helical magnetic field on tokamak HYBTOK-II
International Nuclear Information System (INIS)
Penetration processes of rotating helical magnetic perturbation (RHMP) into tokamak plasmas have been studied on a small tokamak device HYBTOK-II for dynamic ergodic divertor experiment preparing in TEXTOR. The radial profiles of RHMP in the plasma have been measured by inserting small magnetic probes into the plasma. The penetration of RHMP has been discussed by using the observed radial profile of RHMP in the plasma based on the growth of magnetic islands (i.e. tearing mode). In the case of the low Doppler-shifted frequency observed from the plasma, the amplification of RHMP in the plasma due to a spatial modification of plasma current has been found. A large Doppler-shifted frequency produces an expected attenuation of RHMP near the magnetic resonance surface due to screening current flow. A decrease of the amplification of RHMP originated from the suppression of the growth of magnetic islands due to a rapid spatial scan of magnetic resonance layer has been found by plasma current oscillation. (author)
A planar conducting microstructure to guide and confine magnetic beads to a sensing zone
Gooneratne, Chinthaka Pasan
2011-08-01
A novel planar conducting microstructure is proposed to transport and confine magnetic micro/nano beads to a sensing zone. Manipulation and concentration of magnetic beads are achieved by employing square-shaped conducting micro-loops, with a few hundred nano-meters in thickness, arranged in a unique fashion. These microstructures are designed to produce high magnetic field gradients which are directly proportional to the force applied to manipulate the magnetic beads. Furthermore, the size of the microstructures allows greater maneuverability and control of magnetic beads than what could be achieved by permanent magnets. The aim of the microstructures is to guide magnetic beads from a large area and confine them to a smaller area where for example quantification would take place. Experiments were performed with different concentrations of 2 μm diameter magnetic beads. Experimental results showed that magnetic beads could be successfully guided and confined to the sensing zone. © 2011 Elsevier B.V. All rights reserved.
Tearing mode suppression by using resonant magnetic perturbation coils on J-TEXT tokamak
International Nuclear Information System (INIS)
A series of experiments on the interactions between external resonant magnetic perturbations (RMP) and plasmas has recently been conducted, using static resonant magnetic perturbation (SRMP) coils on the Joint Texas Experimental Tokamak (J-TEXT). The tearing mode can be completely suppressed by applying SRMP. However, the locked mode is likely to be stimulated under a larger SRMP field even though the tearing mode has been first suppressed. A numerical simulation shows three typical regimes of RMP's effects on the tearing mode, which are consistent with experimental results.
Design of magnetic probes for MHD measurements in ASDEX tokamak
International Nuclear Information System (INIS)
The design of magnetic probes (Mirnov coils) is described in this report. These probes are used in ASDEX to investigate MHD modes and measure the plasma displacement together with magnetic flux loops. Concerning the high temperature rise during a plasma shot proper material for the coil form of the magnetic probes and the suitable wire and cable in the high vacuum chamber in conjunction with special geometrical construction have been selected. The electrical circuit updated to operate in a high noise environment is shown and first MHD mode signals demonstrate the effeciency of the system. (orig.)
International Nuclear Information System (INIS)
Theoretical and computational analyses of bootstrapped tokamaks with oscillating field current drive (OFCD) have been developed using a nonlinear magnetic helicity model. Assuming a rigid current profile, the conditions for optimal tokamak steady-state operation are derived and are shown to agree with the results of computer calculations. Generalized limit formulae for the toroidal plasma beta and bootstrap current fraction are also obtained. The results of the analyses indicate that steady-state bootstrapped tokamak operation with high toroidal plasma beta can best be achieved in tight aspect ratio A → 1 reactors with OFCD supplying as much as a quarter of the total toroidal plasma current. (author)
International Nuclear Information System (INIS)
The toroidal field (TF) system of Tore Supra (TS) is superconducting. After 16 years of operation it is possible to give an overview of the experience gained on a large superconducting system integrated in a large Tokamak. Quantitative data will be given, about the TF system for the cryogenic system and for the magnet system as well, concerning the number of plasmas shots and the availability of the machine. The origin and the number of breakdowns or incidents will be described, with emphasis on cryogenics, to document repairs and changes on the system components. Concerning the behaviour during operation, the Fast Safety Discharges (FSD) in operation are of particular interest for the Tokamak operation, as they interrupt it on a significant time of the order of one hour. This aspect is particularly documented. The approach followed to decrease the number of these FSD will be reported and explained. The Tore Supra Tokamak was the first important meeting between Superconductivity and Plasma Physics on a large scale. Overall, despite the differences in design and size, the accumulated experience over 16 years of operation is a useful tool to prepare the manufacturing and the operation of the ITER magnets. (authors)
Recent experiments on the STOR-M Tokamak
International Nuclear Information System (INIS)
Recent experiments on the STOR-M tokamak have been focused on basic tokamak physics and technology development for controlled thermonuclear fusion research. Active control of the magnetohydrodynamic (MHD) instabilities has been achieved by helical resonant magnetic perturbations (RMPs). Improved confinement has been induced by gas puffing during ohmic discharges. Modification of toroidal flow velocities by a tangentially injected compact torus (CT) plasmoid to the STOR-M discharge has been observed. (author)
Maximum entropy tokamak configurations
International Nuclear Information System (INIS)
The new entropy concept for the collective magnetic equilibria is applied to the description of the states of a tokamak subject to ohmic and auxiliary heating. The condition for the existence of steady state plasma states with vanishing entropy production implies, on one hand, the resilience of specific current density profiles and, on the other, severe restrictions on the scaling of the confinement time with power and current. These restrictions are consistent with Goldston scaling and with the existence of a heat pinch. (author)
A need for non-tokamak approaches to magnetic fusion energy
International Nuclear Information System (INIS)
Focusing exclusively on conventional tokamak physics in the quest for commercial fusion power is premature, and the options for both advanced-tokamak and non-tokamak concepts need continued investigation. The basis for this claim is developed, and promising advanced-tokamak and non-tokamak options are suggested
Woolley, Robert D.
1998-01-01
A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.
Conceptual integrated approach for the magnet system of a tokamak reactor
International Nuclear Information System (INIS)
Highlights: • We give a conceptual approach of a fusion reactor magnet system based on analytical formula. • We give design criteria for the CS and TF cable in conduit conductors and for the magnet system structural description. • We apply this conceptual approach to ITER and we crosscheck with actual characteristics. • We apply this conceptual approach to a possible version of DEMO. - Abstract: In the framework of the reflexion about DEMO, a conceptual integrated approach for the magnet system of a tokamak reactor is presented. This objective is reached using analytical formulas which are presented in this paper, coupled to a Fortran code ESCORT (Electromagnetic Superconducting System for the Computation of Research Tokamaks), to be integrated into SYCOMORE, a code for reactor modelling presently in development at CEA/IRFM in Cadarache, using the tools of the EFDA Integrated Tokamak Modelling task force. The analytical formulas deal with all aspects of the magnet system, starting from the derivation of the TF system general geometry, from the plasma main characteristics. The design criteria for the cable current density and the structural design of the toroidal field and central solenoid systems are presented, enabling to deliver the radial thicknesses of the magnets and enabling also to estimate the plasma duration of the plateau. As a matter of fact, a pulsed version DEMO is presently actively considered in the European programmes. Considerations regarding the cryogenics and the protection are given, affecting the general design. An application of the conceptual approach is presented, allowing a comparison between ESCORT output data and actual ITER parameters and giving the main characteristics of a possible version for DEMO
Conceptual integrated approach for the magnet system of a tokamak reactor
Energy Technology Data Exchange (ETDEWEB)
Duchateau, J.-L., E-mail: Jean-luc.duchateau@cea.fr; Hertout, P.; Saoutic, B.; Artaud, J.-F.; Zani, L.; Reux, C.
2014-11-15
Highlights: • We give a conceptual approach of a fusion reactor magnet system based on analytical formula. • We give design criteria for the CS and TF cable in conduit conductors and for the magnet system structural description. • We apply this conceptual approach to ITER and we crosscheck with actual characteristics. • We apply this conceptual approach to a possible version of DEMO. - Abstract: In the framework of the reflexion about DEMO, a conceptual integrated approach for the magnet system of a tokamak reactor is presented. This objective is reached using analytical formulas which are presented in this paper, coupled to a Fortran code ESCORT (Electromagnetic Superconducting System for the Computation of Research Tokamaks), to be integrated into SYCOMORE, a code for reactor modelling presently in development at CEA/IRFM in Cadarache, using the tools of the EFDA Integrated Tokamak Modelling task force. The analytical formulas deal with all aspects of the magnet system, starting from the derivation of the TF system general geometry, from the plasma main characteristics. The design criteria for the cable current density and the structural design of the toroidal field and central solenoid systems are presented, enabling to deliver the radial thicknesses of the magnets and enabling also to estimate the plasma duration of the plateau. As a matter of fact, a pulsed version DEMO is presently actively considered in the European programmes. Considerations regarding the cryogenics and the protection are given, affecting the general design. An application of the conceptual approach is presented, allowing a comparison between ESCORT output data and actual ITER parameters and giving the main characteristics of a possible version for DEMO.
Plasma edge transport with magnetic islands—a comparison between tokamak and reversed-field pinch
International Nuclear Information System (INIS)
In the reversed-field pinch (RFP) edge, measured transport and flows are strongly influenced by magnetic islands (Vianello 2013 Nucl. Fusion 53 073025). In fact, these islands determine a differential radial diffusion of electrons and ions which, interacting with the wall, give rise to a characteristic edge ambipolar potential. Such island structures also arise in tokamak plasmas, when resonant magnetic perturbations (RMPs) are applied for control of edge-localized modes. They impose a characteristic modulation to edge electron density and temperature fields, in close correlation with the local magnetic vacuum topology (Schmitz 2012 Nucl. Fusion 52 054001). In order to develop a generic picture of particle transport with magnetic islands located in the plasma edge between RFPs and tokamaks with RMP, test-particle transport simulations are done on TEXTOR with the same tool used in RFX-mod, namely, the guiding-centre code ORBIT (White and Chance 1984 Phys. Fluids 27 2455–67). A typical TEXTOR discharge in the (m, n) = (12, 4) configuration is reconstructed and analysed with ORBIT. We use Poincaré and connection length analysis of electrons and ion orbits to analyse the magnetic structure taking into account the different gyro-orbits of both constituents. Density distributions of test ions and electrons are calculated and used to obtain an initial estimate of the plasma potential and radial electric field around the island. (paper)
A magnetically driven reciprocating probe for tokamak scrape-off layer measurements
International Nuclear Information System (INIS)
A new in situ reciprocating probe system has been developed to provide scrape-off layer measurements in the Tore Supra tokamak. The probe motion is provided by the rotation of an energized coil in the tokamak magnetic field. Simple analytic approximations to the exact numerical model were used to identify the important parameters that govern the dynamics of the system, and optimize the coil geometry, the electrical circuit, and the stiffness of the retaining spring. The linear speed of the probe is directly proportional to the current induced by the coil's rotation; its integral gives the coil position, providing a means to implement real-time feedback control of the probe motion. Two probes were recently mounted on a movable outboard antenna protection limiter in Tore Supra and provided automatic measurements during the 2011 experimental campaign. (authors)
Gyrokinetic particle simulation for thermonuclear plasma turbulence studies in magnetic confinement
Janhunen, Salomon
2013-01-01
Thermal transport in a magnetised plasma is believed to be substantially enhanced due to turbulence. The ELMFIRE code has been developed for tokamak plasma turbulence studies in high temperature magnetized plasmas. ELMFIRE calculates the evolution of the Boltzmann equation in a magnetized plasma, including long scale interactions between particles calculated through field equations. In this work we concentrate on benchmarking the ELMFIRE against published results from other turbulence code...
Magnet power system for the Microwave Tokamak Experiment (MTX)
International Nuclear Information System (INIS)
The system configuration, layout, and general philosophy for the MTX magnet power system is described. The vast majority of the magnet power equipment was quite successfully used on the ALCATOR-C experiment at the Massachusetts Institute of Technology. The AC power for the magnet system at MIT was obtained from a 225MVA alternator. The power for the system at LLNL is obtained directly from the local utility's 230 kV line. This installation, therefore, necessitates the addition of a great deal of equipment in ranges from new switchgear in the substation to using existing switchgear obtained from MIT as contractors for intershop electrical isolation as well as safety isolation for personnel entry into the experimental area. Additionally, some discussion is made of the unique layout of this facility and the tradeoffs made to accommodate them. 2 refs., 6 figs
Emerging Magnetic Flux as a Trigger of a Confined Flare
Titov, Viacheslav; Wang, Yuming; Liu, Kai; Liu, Rui; Wang, Haimin; Gou, Tingyu
We present the observation of an X-class long-duration confined flare and the analysis of its magnetic structure evolution. Although it appears as a compact-loop flare in the traditional EUV passbands (171 and 195 {Å}), in the passbands sensitive to flare plasmas (94 and 131 {Å}; ˜6-10 MK), it exhibits a cusp-shaped structure above an arcade of loops like other long-duration events. Inspecting images in a running difference approach, we find that the seemingly diffuse, quasi-static cusp-shaped structure actually consists of multiple nested loops that repeatedly rise upward and disappear approaching the cusp point. Over the gradual phase of the flare, we detect numerous episodes of loop rising, each lasting tens of seconds to minutes. A differential emission measure analysis reveals that the temperature is highest at the top of the arcade and becomes cooler at higher altitudes within the cusp-shaped structure. These features are opposite to what the standard flare model predicts. To understand the actual scenario of this event, we make first a nonlinear force-free reconstruction of the active region for a sequence of vector magnetograms that covers the time period of the event’s duration and then investigate the structure of the resulting sequence of configurations, using our field-line mapping technique based on the so-called squashing factor Q. Our analysis shows that the configurations have locally a tri-polar structure, in the middle of which the negative photospheric polarity is divided in half by a high-Q line. The respective halves belong to two adjacent sheared arcades, one of which harbors a magnetic flux rope. The indicated high-Q line is a footprint of a hyperbolic flux tube (HFT) where two quasi-separatrix layers adjoin each other at a T-type junction passing through the joint arcades’ apex. Comparing UV 1600 {Å} images of the Sun's disk with photospheric Q-maps at close times, we conclude that the emergence of a new magnetic flux within one of
International Nuclear Information System (INIS)
Large edge localized modes (ELMs) typically accompany good H-mode confinement in fusion devices, but can present problems for plasma facing components because of high transient heat loads. Here the range of techniques for ELM control deployed in fusion devices is reviewed. Two strategies in the ITER baseline design are emphasized: rapid ELM triggering and peak heat flux control via pellet injection, and the use of magnetic perturbations to suppress or mitigate ELMs. While both of these techniques are moderately well developed, with reasonable physical bases for projecting to ITER, differing observations between multiple devices are also discussed to highlight the needed community R and D. In addition, recent progress in ELM-free regimes, namely quiescent H-mode, I-mode, and enhanced pedestal H-mode is reviewed, and open questions for extrapolability are discussed. Finally progress and outstanding issues in alternate ELM control techniques are reviewed: supersonic molecular beam injection, edge electron cyclotron heating, lower hybrid heating and/or current drive, controlled periodic jogs of the vertical centroid position, ELM pace-making via periodic magnetic perturbations, ELM elimination with lithium wall conditioning, and naturally occurring small ELM regimes. (paper)
Energy Technology Data Exchange (ETDEWEB)
Maingi, R [PPPL
2014-07-01
Large edge localized modes (ELMs) typically accompany good H-mode confinement in fusion devices, but can present problems for plasma facing components because of high transient heat loads. Here the range of techniques for ELM control deployed in fusion devices is reviewed. The two baseline strategies in the ITER baseline design are emphasized: rapid ELM triggering and peak heat flux control via pellet injection, and the use of magnetic perturbations to suppress or mitigate ELMs. While both of these techniques are moderately well developed, with reasonable physical bases for projecting to ITER, differing observations between multiple devices are also discussed to highlight the needed community R & D. In addition, recent progress in ELM-free regimes, namely Quiescent H-mode, I-mode, and Enhanced Pedestal H-mode is reviewed, and open questions for extrapolability are discussed. Finally progress and outstanding issues in alternate ELM control techniques are reviewed: supersonic molecular beam injection, edge electron cyclotron heating, lower hybrid heating and/or current drive, controlled periodic jogs of the vertical centroid position, ELM pace-making via periodic magnetic perturbations, ELM elimination with lithium wall conditioning, and naturally occurring small ELM regimes.
Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II
International Nuclear Information System (INIS)
Radial profile of externally applied resonant magnetic perturbation (RMP) field with mode numbers of m = 6 and n = 2 in a small tokamak device HYBTOK-II have been investigated using a magnetic probe array, which is able to measure the radial profile of magnetic field perturbation induced by applying RMP. Results of RMP penetration into the plasma show that the RMP decreased toward the plasma center, while they were amplified around the resonant surface with a safety factor q = 3 due to the formation of magnetic islands. This suggests that RMP fields for controlling edge plasmas may trigger some kind of MHD instabilities. In addition, simulation results, based on a linearized four-field model, which agrees with the experimental ones, indicates that the penetration and amplification process of RMP strongly depend on a Doppler-shifted frequency between the RMP and plasma rotation
Reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak
Sakharov, N. V.; Voronin, A. V.; Gusev, V. K.; Kavin, A. A.; Kamenshchikov, S. N.; Lobanov, K. M.; Minaev, V. B.; Novokhatsky, A. N.; Patrov, M. I.; Petrov, Yu. V.; Shchegolev, P. B.
2015-12-01
The results of reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak by means of the EFIT code and by the method of movable filaments with the use of the data from magnetic measurements are compared. The EFIT code allows one to completely reconstruct the magnetic configuration by solving the Grad-Shafranov equation. In the method of movable filaments, the distribution of the toroidal current flowing through the plasma is described by a set of infinitely thin current-carrying rings. In this method, the last closed magnetic surface (LCMS) and the open surfaces lying beyond the LCMS are calculated. Using both methods, the coordinates of the regions where the separatrix strikes the divertor plates were determined. The results obtained agree well with the distributions of the temperature over the tungsten divertor tiles measured using an IR camera.
Generation of a magnetic island by edge turbulence in tokamak plasmas
International Nuclear Information System (INIS)
We investigate, through extensive 3D magneto-hydro-dynamics numerical simulations, the nonlinear excitation of a large scale magnetic island and its dynamical properties due to the presence of small-scale turbulence. Turbulence is induced by a steep pressure gradient in the edge region [B. D. Scott, Plasma Phys. Controlled Fusion 49, S25 (2007)], close to the separatrix in tokamaks where there is an X-point magnetic configuration. We find that quasi-resonant localized interchange modes at the plasma edge can beat together and produce extended modes that transfer energy to the lowest order resonant surface in an inner stable zone and induce a seed magnetic island. The island width displays high frequency fluctuations that are associated with the fluctuating nature of the energy transfer process from the turbulence, while its mean size is controlled by the magnetic energy content of the turbulence
Reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak
Energy Technology Data Exchange (ETDEWEB)
Sakharov, N. V., E-mail: nikolay.sakharov@mail.ioffe.ru; Voronin, A. V.; Gusev, V. K. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation); Kavin, A. A.; Kamenshchikov, S. N.; Lobanov, K. M. [Efremov Research Institute of Electrophysical Apparatus (Russian Federation); Minaev, V. B.; Novokhatsky, A. N.; Patrov, M. I., E-mail: michael.patrov@mail.ioffe.ru; Petrov, Yu. V.; Shchegolev, P. B. [Russian Academy of Sciences, Ioffe Physical Technical Institute (Russian Federation)
2015-12-15
The results of reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak by means of the EFIT code and by the method of movable filaments with the use of the data from magnetic measurements are compared. The EFIT code allows one to completely reconstruct the magnetic configuration by solving the Grad−Shafranov equation. In the method of movable filaments, the distribution of the toroidal current flowing through the plasma is described by a set of infinitely thin current-carrying rings. In this method, the last closed magnetic surface (LCMS) and the open surfaces lying beyond the LCMS are calculated. Using both methods, the coordinates of the regions where the separatrix strikes the divertor plates were determined. The results obtained agree well with the distributions of the temperature over the tungsten divertor tiles measured using an IR camera.
Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II
Energy Technology Data Exchange (ETDEWEB)
Hayashi, Y., E-mail: hayashi-yuki13@ees.nagoya-u.ac.jp [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Suzuki, Y.; Ohno, N. [Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan); Okamoto, M. [Ishikawa National College of Technology, Kitachujo, Tsubata-cho, Kahoku-gun, Ishikawa 929-0392 (Japan); Kikuchi, Y. [University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280 (Japan); Sakakibara, S.; Watanabe, K.; Takemura, Y. [National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292 (Japan)
2015-08-15
Radial profile of externally applied resonant magnetic perturbation (RMP) field with mode numbers of m = 6 and n = 2 in a small tokamak device HYBTOK-II have been investigated using a magnetic probe array, which is able to measure the radial profile of magnetic field perturbation induced by applying RMP. Results of RMP penetration into the plasma show that the RMP decreased toward the plasma center, while they were amplified around the resonant surface with a safety factor q = 3 due to the formation of magnetic islands. This suggests that RMP fields for controlling edge plasmas may trigger some kind of MHD instabilities. In addition, simulation results, based on a linearized four-field model, which agrees with the experimental ones, indicates that the penetration and amplification process of RMP strongly depend on a Doppler-shifted frequency between the RMP and plasma rotation.
International Nuclear Information System (INIS)
The author analyzes the eddy currents and the electro-magnetic forces on the lower hybrid wave (LHW) launching antenna on the superconducting Tokamak HT-7 by using a finite element circuit method. A new iterative algorithm is developed to analyze the coupled magnetic fields which are very difficult to be calculated. The method and results obtained are helpful to study the eddy currents and electro-magnetic forces on metal plates which are placed in a rather complicated electro-magnetic environment
International Nuclear Information System (INIS)
A multi-pass Thomson scattering (TS) system based on confining laser pulses in an optical cavity was constructed for measuring very low-density plasma in the TST-2 spherical tokamak device. This paper describes the setup of the optical system, injection of the laser pulse into the cavity, and properties of the confined laser pulse. A combination of Pockels cell plus polarizer, which serves as an optical shutter, allows us to inject and then confine intense laser pulses in the cavity. A photodiode signal monitoring the very weak light leaking from the cavity mirrors demonstrated that the laser pulse makes many round trips, with a round-trip efficiency of approximately 0.73. The effective number of round trips (i.e., the signal enhancement factor) is approximately 3.7. For an injection efficiency of approximately 0.69, a cavity-confined laser pulse, applied to Thomson scattering, will yield a scattered signal that is five times larger than that from a single-pass laser pulse. (author)
Observation on effect of ergodic magnetic limiter for an ohmic heating plasma on JFT-2M tokamak
International Nuclear Information System (INIS)
An ergodic magnetic limiter (EML) is applied to the ohmic heating plasma in JFT-2M tokamak. Different phenomena in plasma behaviour from that during usual ohmic heating phase are reported. Three types of behaviour are observed depending on ergodic field strength and plasma surface q. The first case corresponds to small EML field, where the maximum attainable density is increased, and the ultimate density linearly increases with the strength of EML field. In the second case with larger EML field and q value, Hα emission bursts are observed. These bursts coincide with a decrease in density and electron temperature, along with a degradation of plasma confinement. Thirdly with larger EML field and lower q value, major disruption is triggered. Larger EML field is required for disruption with the increase of the surface q. Larger EML field is also required for the disruption in the discharge of higher plasma current at the constant surface q. A time delay between the onset of EML coil current and the plasma response is observed, which is consistent with the estimation of the skin effect of plasma. (author)
Model for Heat Pinch in Reversed Magnetic Shear Tokamak Plasmas
Qiu, Xiao-ming; X, Qiu M.; Wang, Ai-ke
1998-10-01
A simple model is proposed to explain the recent experiment in TFTR and the more recent one in JT-60U. In the model the significant reduction of effective thermal diffusivities of ions and electrons (χieff and χeeff) is attributed to the inward flows of drift wave energy, induced by the synergistic effects of the reversed magnetic shear and E × B velocity shear, where E is due to ion pressure gradient. Numerical results demonstrate the predictions of the present model, in particular, the numerical results for χieff are in good agreement with experimental trents.
Interaction of runaway electrons with magnetic field ripple in the HT-7 tokamak
International Nuclear Information System (INIS)
The runaway electrons have been measured in combination with hard x-ray detectors and thermographic camera in the HT-7 tokamak. The dynamics of runaways in the core and edge regions is monitored simultaneously. The HXR signals monitor the lost runaways and the dynamics of runaways in the edge region. The maximum energy of runaways in the edge region could be blocked by the resonance of gyromotion with the nth harmonic of the magnetic field ripple. This resonance interaction creates a barrier to a further increase in the energy of runaway electrons. (author)
International Nuclear Information System (INIS)
The analytical solution for global geodesic acoustic modes (GGAMs) in a tokamak with a positive magnetic shear profile and a monotonic temperature profile is found in the framework of magnetohydrodynamic theory. The axisymmetric eigenvalue problem for perturbed pressure and electrostatic potential is formulated as a recurrent set of equations for poloidal Fourier harmonics. The integral condition for the existence of GGAMs is obtained. It is shown that the traditional paradigm of having a off-axis maximum of the local geodesic acoustic frequency is not necessary for the existence of GGAMs; a representative example is designed. (paper)
Forces on liquid lithium modules in a tokamak blanket due to the pulsed poloidal magnetic field
International Nuclear Information System (INIS)
This paper treats cylindrical modules filled with liquid lithium in the presence of a steady toroidal magnetic field and a time-dependent poloidal field. Solutions for liquid lithium flows and formulas for the forces on the modules are presented for both axial and transverse poloidal fields. Numerical examples are presented for the design in the ORNL/Westinghouse Tokamak Blanket Study. The initial analysis ignores the ends of the modules and treats infinitely long pipes, but the effects of the ends are also treated. Calculations and conclusions based on the solutions for infinitely long pipes are not significantly altered by end effects
International Nuclear Information System (INIS)
The research performed under this grant over the current 11-1/2 month period has concentrated on key tokamak plasma confinement and heating theory issues: extensions of neoclassical MHD; viscosity coefficients and transport; nonlinear resistive MHD simulations of Tokapole II plasmas; ICRF and edge plasma interactions; energy confinement degradation due to macroscopic phenomena; and coordination of a new transport initiative. Progress and publications in these areas are briefly summarized in this report. 21 refs
Magnetic field analysis during breakdown phase in the low loop resistance tokamak HT-2
Energy Technology Data Exchange (ETDEWEB)
Abe, Mitsushi; Doi, Akira; Takeuchi, Kazuhiro; Otsuka, Michio (Hitachi Ltd., Ibaraki (Japan). Energy Research Lab.); Nishio, Satoshi; Sugihara, Masayoshi; Yoshino, Ryuji; Okazaki, Takashi
1994-06-01
The magnetic analysis code SHP was improved in order to understand the poloidal magnetic field during the breakdown phase of the Hitachi tokamak HT-2, which had its loop resistance modified to a very low value. The SHP code uses a model with filamental loop currents in the plasma area. Its improvements are the following. (1) The eddy currents on the vacuum vessel, which are assumed to be uniform in the toroidal direction, are expanded by distribution functions obtained by a singular value decomposition of a projection matrix from the eddy currents to the flux distribution on the plasma surface area. (2) The magnetic field due to the iron core biasing current and the stray horizontal field of the toroidal field coils are compensated. After improvements, it was confirmed that the poloidal field null point was generated before breakdown and the SHP results were consistent with discharge photographs taken by a high speed camera. (author).
Design study of superconducting toroidal field magnet for tokamak fusion power reactor
International Nuclear Information System (INIS)
Design study of the superconducting toroidal field magnet for a 2000 MW sub(t) tokamak fusion power reactor has been carried out. Performed here were conductor design, magnetic field calculation, design of coil support, stress analysis and design of refrigeration system. The maximum toroidal field at the coil is 12T, providing 6T at the plasma center. Nb3Sn superconductors are employed in the higher field zone. The operation current is 34.72 kA, and the conductors are fully stabilized. The heat load in the magnet is 21.1 kW, and the required liquefaction rate is 36,000 l/h. Many technological problems were revealed by the design study. (auth.)
Shearless bifurcation on symplectic maps of magnetic field lines in tokamaks with reversed current
Bartoloni, B.; Schelin, A. B.; Caldas, I. L.
2016-07-01
We introduce two-dimensional symplectic maps to describe the Poincaré maps of magnetic field lines in large aspect ratio tokamak equilibria with reversed non-monotonic plasma current density profiles. For these maps, we investigate the effect of the symmetry breaking due to the toroidal correction with a peculiar invariant, namely, a magnetic surface with a null rotation number, enclosing a vanishing current. We find that this rotationless invariant surface is surrounded by many small island chains. Furthermore, near such invariant, the symmetry breaking gives rise to two magnetic shearless invariants surrounded by twin island chains. We also find chaotic lines adjacent to all the observed islands created by the considered structurally unstable equilibria.
Measurement of magnetic fluctuation-induced heat transport in tokamaks and RFP
International Nuclear Information System (INIS)
It has long been recognized that fluctuations in the magnetic field are a potent mechanism for the anomalous transport of energy in confined plasmas. The energy transport process originates from particle motion along magnetic fields, which have a fluctuating component in the radial direction (perpendicular to the confining equilibrium magnetic surfaces). A key feature is that the transport can be large even if the fluctuation amplitude is small. If the fluctuations are resonant with the equilibrium magnetic field (i.e., the fluctuation amplitude is constant along an equilibrium field line) then a small fluctuation can introduce stochasticity to the field line trajectories. Particles following the chaotically wandering field lines can rapidly carry energy across the plasma
International Nuclear Information System (INIS)
Abstracts of the talks presented to the 'Energetic Particles in Magnetic Confinement Systems. 11 IAEA TM - 20th Anniversary Meeting' (Sept. 21-23, 2009) deal with the up-to-date problems: Alpha particles physics, Transport of energetic particles, Effects of energetic particles in magnetic confinement fusion devices, Collective phenomena: Alfven Eigenmodes, energetic particle modes and others, Runaway electrons and disruptions, Diagnostics for energetic particles
Stress analysis studies in optimised 'D' shaped TOKAMAK magnet designs
International Nuclear Information System (INIS)
A suite of computer programs TOK was developed which enabled simple data input to be used for computation of magnetic fields and forces in a toroidal system of coils with either D-shaped or circular cross section. An additional requirement was that input data to the Swansea stress analysis program FINESSE could be output from the TOK fields and forces program, and that graphical output from either program should be available. A further program was required to optimise the coil shape. This used the field calculating routines from the TOK program. The starting point for these studies was the proposed 40 coil Princeton design. The stresses resulting from three different shapes of D-coil were compared. (author)
International Nuclear Information System (INIS)
Full text: Non-axisymmetric magnetic perturbations can fundamentally change neoclassical transport in tokamaks by distorting particle orbits on deformed or broken flux surfaces. Understanding transport under non-axisymmetric magnetic perturbations is a critical issue for ITER and future fusion devices where non-axisymmetric perturbations are potentially important control elements to actively stabilize locked modes, edge localized modes, and resistive wall modes. Neoclassical transport with non-axisymmetry, often called Neoclassical Toroidal Viscosity (NTV) transport in tokamaks, is intrinsically non-ambipolar, and highly complex depending on parametric regimes. Thus a numerical approach is required to achieve its precise description. This paper reports the study of non-ambipolar transport and NTV torque with a new δf particle code, and the improved understanding of magnetic braking in perturbed tokamaks. Initial calculation of non-ambipolar particle flux clearly indicates the strong resonant nature of magnetic breaking, which is typically supposed as driven by non-resonant perturbations, while bootstrap current shows resonant or non-resonant features depending on collisionality. In addition, NTV torque is directly estimated by calculating anisotropic pressures and utilizing magnetic field spectrum method. Calculation results of NTV compared with theory and experiments will be reported, and detailed analyses on magnetic braking in tokamaks such as NSTX will be discussed. (author)
Klimanov, Igor; Fasoli, Ambrogio
2007-01-01
The performance of tokamaks is usually described in terms of plasma temperature, density and confinement time. The term temperature implies that the plasma is in thermal equilibrium and its particles have maxwellian (normal) velocity distribution. However, in several conditions, the plasma contains a significant number of suprathermal or 'fast' particles, whose energy is several times higher than thermal energy. The number of such particles can be significantly higher than that corresponding ...
Steady State Advanced Tokamak (SSAT): The mission and the machine
International Nuclear Information System (INIS)
Extending the tokamak concept to the steady state regime and pursuing advances in tokamak physics are important and complementary steps for the magnetic fusion energy program. The required transition away from inductive current drive will provide exciting opportunities for advances in tokamak physics, as well as important impetus to drive advances in fusion technology. Recognizing this, the Fusion Policy Advisory Committee and the US National Energy Strategy identified the development of steady state tokamak physics and technology, and improvements in the tokamak concept, as vital elements in the magnetic fusion energy development plan. Both called for the construction of a steady state tokamak facility to address these plan elements. Advances in physics that produce better confinement and higher pressure limits are required for a similar unit size reactor. Regimes with largely self-driven plasma current are required to permit a steady-state tokamak reactor with acceptable recirculating power. Reliable techniques of disruption control will be needed to achieve the availability goals of an economic reactor. Thus the central role of this new tokamak facility is to point the way to a more attractive demonstration reactor (DEMO) than the present data base would support. To meet the challenges, we propose a new ''Steady State Advanced Tokamak'' (SSAT) facility that would develop and demonstrate optimized steady state tokamak operating mode. While other tokamaks in the world program employ superconducting toroidal field coils, SSAT would be the first major tokamak to operate with a fully superconducting coil set in the elongated, divertor geometry planned for ITER and DEMO
Kikuchi, Y; de Bock, M F M; Finken, K H; Jakubowski, M; Jaspers, R; Koslowski, H R; Kraemer-Flecken, A; Lehnen, M; Liang, Y; Matsunaga, G; Reiser, D; Wolf, R C; Zimmermann, O
2006-08-25
The magnetic field penetration process into a magnetized plasma is of basic interest both for plasma physics and astrophysics. In this context special measurements on the field penetration and field amplification are performed by a Hall probe on the dynamic ergodic divertor (DED) on the TEXTOR tokamak and the data are interpreted by a two-fluid plasma model. It is observed that the growth of the forced magnetic reconnection by the rotating DED field is accompanied by a change of the plasma fluid rotation. The differential rotation frequency between the DED field and the plasma plays an important role in the process of the excitation of tearing modes. The momentum input from the rotating DED field to the plasma is interpreted by both a ponderomotive force at the rational surface and a radial electric field modified by an edge ergodization. PMID:17026312
Interdependence of magnetic islands, halo current and runaway electrons in T-10 tokamak
International Nuclear Information System (INIS)
The results of experiments on a modulation of halo current through a rail limiter and of x-ray emission from the limiter under the influence of rotating magnetic islands are presented. The external part of the halo-current circuit connected the rail limiter at one side and the discharge chamber with a circular limiter at the other side. A controllable connector that was switched on at a preprogrammed moment of time during the tokamak discharge was introduced into the circuit. In discharges with MHD activity, oscillations of the halo current were observed. The frequency of the oscillations was equal to the frequency of the dominant mode of the poloidal magnetic field perturbation. In some conditions the switching on of the connector in the halo-current circuit resulted in a shift of the MHD mode frequency. This means that the halo current can influence the rotation velocity of the magnetic islands. In the case of low plasma density, repetitive spikes of hard x-ray emission from the rail limiter were observed. These spikes were coherent with the MHD-activity signal and the halo-current oscillations. It can be concluded that besides an effect of magnetic islands resulting in halo-current and x-ray modulation with the frequency of MHD activity, an influence of halo current on the magnetic island behaviour was observed. This influence can be attributed to a coupling between the magnetic islands and the space-resonant component of the halo-current magnetic field. (author)
International Nuclear Information System (INIS)
In high density Ohmically heated discharges in the tokamak TEXTOR a transition from the saturated Ohmic confinement (SOC) to the improved Ohmic confinement (IOC) was observed triggered by a sudden reduction of the external gas flow. The SOC-IOC transition was investigated regarding the influence of the toroidal ITG instability driven by the ion temperature gradient (ITG). The ion temperature profiles were measured with high radial resolution by means of charge-exchange recombination spectroscopy (CXRS) with a high-energetic diagnostic hydrogen beam recently installed at TEXTOR. On the basis of the measured ion temperature distributions the ηi parameter (ratio of the density and ion temperature decay lengths) and the growth rate of the toroidal ITG instability were calculated. After the SOC-IOC transition ηi drops and lies in a noticeably smaller radial region over the threshold for the toroidal ITG. In consequence of it, the IOC regime is characterized by a clear reduction of the ITG growth rate γITG which was calculated including finite Larmor radius effects. The steepening of the plasma density profile after the decrease of the external gas flow is the main reason for the reduction of the ITG growth rate and the subsequent confinement transition to the IOC regime
Losses of heat and particles in the presence of strong magnetic field perturbations
Gupta, Abhinav
2009-01-01
Thermonuclear fusion has potential to offer an economically, environmentally and socially acceptable supply of energy. A promising reactor design to execute thermonuclear fusion is the toroidal magnetic confinement device, tokamak. The tokamak still faces challenges in the major areas which can be categorised into confinement, heating and fusion technology. This thesis addresses the problem of confinement, in particular the role of transport along magnetic field lines perturbed by diverse MHD...
A Midsize Tokamak As Fast Track To Burning Plasmas
International Nuclear Information System (INIS)
This paper presents a midsize tokamak as a fast track to the investigation of burning plasmas. It is shown that it could reach large values of energy gain ((ge) 10) with only a modest improvement in confinement over the scaling that was used for designing the International Thermonuclear Experimental Reactor (ITER). This could be achieved by operating in a low plasma recycling regime that experiments indicate can lead to improved plasma confinement. The possibility of reaching the necessary conditions of low recycling using a more efficient magnetic divertor than those of present tokamaks is discussed.
A Midsize Tokamak As Fast Track To Burning Plasmas
Energy Technology Data Exchange (ETDEWEB)
E. Mazzucato
2010-07-14
This paper presents a midsize tokamak as a fast track to the investigation of burning plasmas. It is shown that it could reach large values of energy gain (≥10) with only a modest improvement in confinement over the scaling that was used for designing the International Thermonuclear Experimental Reactor (ITER). This could be achieved by operating in a low plasma recycling regime that experiments indicate can lead to improved plasma confinement. The possibility of reaching the necessary conditions of low recycling using a more efficient magnetic divertor than those of present tokamaks is discussed.
International Nuclear Information System (INIS)
This paper formulates the Tokamak Magneto-Hydrodynamics (TMHD), initially outlined by X. Li and L. E. Zakharov [Plasma Science and Technology 17(2), 97–104 (2015)] for proper simulations of macroscopic plasma dynamics. The simplest set of magneto-hydrodynamics equations, sufficient for disruption modeling and extendable to more refined physics, is explained in detail. First, the TMHD introduces to 3-D simulations the Reference Magnetic Coordinates (RMC), which are aligned with the magnetic field in the best possible way. The numerical implementation of RMC is adaptive grids. Being consistent with the high anisotropy of the tokamak plasma, RMC allow simulations at realistic, very high plasma electric conductivity. Second, the TMHD splits the equation of motion into an equilibrium equation and the plasma advancing equation. This resolves the 4 decade old problem of Courant limitations of the time step in existing, plasma inertia driven numerical codes. The splitting allows disruption simulations on a relatively slow time scale in comparison with the fast time of ideal MHD instabilities. A new, efficient numerical scheme is proposed for TMHD
Zakharov, Leonid E.; Li, Xujing
2015-06-01
This paper formulates the Tokamak Magneto-Hydrodynamics (TMHD), initially outlined by X. Li and L. E. Zakharov [Plasma Science and Technology 17(2), 97-104 (2015)] for proper simulations of macroscopic plasma dynamics. The simplest set of magneto-hydrodynamics equations, sufficient for disruption modeling and extendable to more refined physics, is explained in detail. First, the TMHD introduces to 3-D simulations the Reference Magnetic Coordinates (RMC), which are aligned with the magnetic field in the best possible way. The numerical implementation of RMC is adaptive grids. Being consistent with the high anisotropy of the tokamak plasma, RMC allow simulations at realistic, very high plasma electric conductivity. Second, the TMHD splits the equation of motion into an equilibrium equation and the plasma advancing equation. This resolves the 4 decade old problem of Courant limitations of the time step in existing, plasma inertia driven numerical codes. The splitting allows disruption simulations on a relatively slow time scale in comparison with the fast time of ideal MHD instabilities. A new, efficient numerical scheme is proposed for TMHD.
Energy Technology Data Exchange (ETDEWEB)
Zakharov, Leonid E. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Li, Xujing [Institute of Computational Mathematics and Scientific/Engineering Computing, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, P.O. Box 2719, Beijing 100190 (China)
2015-06-15
This paper formulates the Tokamak Magneto-Hydrodynamics (TMHD), initially outlined by X. Li and L. E. Zakharov [Plasma Science and Technology 17(2), 97–104 (2015)] for proper simulations of macroscopic plasma dynamics. The simplest set of magneto-hydrodynamics equations, sufficient for disruption modeling and extendable to more refined physics, is explained in detail. First, the TMHD introduces to 3-D simulations the Reference Magnetic Coordinates (RMC), which are aligned with the magnetic field in the best possible way. The numerical implementation of RMC is adaptive grids. Being consistent with the high anisotropy of the tokamak plasma, RMC allow simulations at realistic, very high plasma electric conductivity. Second, the TMHD splits the equation of motion into an equilibrium equation and the plasma advancing equation. This resolves the 4 decade old problem of Courant limitations of the time step in existing, plasma inertia driven numerical codes. The splitting allows disruption simulations on a relatively slow time scale in comparison with the fast time of ideal MHD instabilities. A new, efficient numerical scheme is proposed for TMHD.
The effect of tangled magnetic fields on instabilities in tokamak plasmas
International Nuclear Information System (INIS)
The high pressure gradients in the edge of a tokamak plasma can lead to the formation of explosive plasma instabilities known as edge localised modes (ELMs). The control of ELMs is an important requirement for the next generation of fusion devices such as ITER. Experiments performed on the Mega Amp Spherical Tokamak (MAST) at Culham have shown that the application of non-axisymetric resonant magnetic perturbations (RMPs) can be used to mitigate ELMs. During the application of the RMPs, clear structures are observed in visible- light imaging of the X-point region. These lobes, or tangles, have been observed for the first time and their appearance is correlated with the mitigation of ELMs. Tangle formation is seen to be associated with the RMPs penetrating the plasma and may be important in explaining why the ELM frequency increases during ELM mitigation. Whilst the number and location of the tangles can be explained by vacuum magnetic field modelling, obtaining the correct radial extent of the tangles requires the plasma response to be taken into account
Calculation of modification to the toroidal magnetic field of the Tokamak Novillo. Part II
International Nuclear Information System (INIS)
In a cylindrical magnetic topology. the confined plasma experiences 'classic' collisional transport phenomena. When bending the cylinder with the purpose of forming a toro, the magnetic field that before was uniform now it has a radial gradient which produces an unbalance in the magnetic pressure that is exercised on the plasma in the transverse section of the toro. This gives place to transport phenomena call 'neo-classicist'. In this work the structure of the toroidal magnetic field produced by toroidal coils of triangular form, to which are added even of coils of compensation with form of half moon is analyzed. With this type of coils it is looked for to minimize the radial gradient of the toroidal magnetic field. The values and characteristics of B (magnetic field) in perpendicular planes to the toro in different angular positions in the toroidal direction, looking for to cover all the cases of importance are exhibited. (Author)
DEFF Research Database (Denmark)
Migliucci, P.; Naulin, Volker
2010-01-01
Fast magnetic pickup coils are used in forward modeling to match parameters in a simple edge localized mode (ELM) filament model. This novel method allows us to determine key parameters for the evolution of the ELM filaments, as effective mode number, radial and toroidal velocities, and average...... current from standard magnetic diagnostics. The method is employed on a number of Joint European Torus (JET) [ F. Romanelli, R. Kamendje, and JET-EFDA Contributors, Nucl. Fusion 49, 104006 (2009) ] pulses. The parameter values obtained are compared to ELM filament characterization from JET and other...... tokamaks, obtained by a range of different diagnostics. It is found that the forward modeling produces key parameters such as the number of filaments and their toroidal velocity in agreement with other observations and in addition allows an estimate of the filament current....
Synergistic effects of magnetic and velocity shear on electromagnetic drift modes in tokamaks
International Nuclear Information System (INIS)
In the fluid model, electromagnetic drift mode in low β tokamak plasmas is studied from a set of new-derived eigenequations, including magnetic shear, perpendicular and parallel velocity shears, perpendicular and parallel current density and their shears, and finite β. It is found that there exists a threshold of perpendicular velocity shear, at which the growth rate tends to zero. The threshold increases with decrease of magnetic shear. On the other hand, the increase of β reduces the growth rate but increases the velocity shear threshold. In addition, we study the effects of parallel velocity shear on the instability and find that it enhances the instability. Furthermore, the preliminary calculations show that the perpendicular current density shear suppresses the instability while the parallel current density shear strengthens it. (author)
Synergistic effects of magnetic and velocity shear on electromagnetic drift modes in tokamaks
International Nuclear Information System (INIS)
Full text: In the fluid model, electromagnetic drift mode in low beta tokamak plasmas is studied from a set of new-derived eigenequations, including magnetic shear, perpendicular and parallel velocity shears, perpendicular and parallel current density and their shears, and finite beta. It is found that there exists a threshold of perpendicular velocity shear, at which the growth rate tends to zero. The threshold increases with decrease of magnetic shear. On the other hand, the increase of beta reduces the growth rate but increases the velocity shear threshold. In addition, we study the effects of parallel velocity shear on the instability and find that it enhances the instability. Furthermore, the preliminary calculations show that the perpendicular current density shear suppresses the instability while the parallel current density shear strengthens it. (author)
Shielding of External Magnetic Perturbations By Torque In Rotating Tokamak Plasmas
Energy Technology Data Exchange (ETDEWEB)
Park, Jong-Kyu; Boozer, Allen H.; Menard, Jonathan E.; Gerhardt, Stefan P.; Sabbagh, Steve A.
2009-08-24
The imposition of a nonaxisymmetric magnetic perturbation on a rotating tokamak plasma requires energy and toroidal torque. Fundamental electrodynamics implies that the torque is essentially limited and must be consistent with the external response of a plasma equilibrium ƒ = j x B. Here magnetic measurements on National Spherical Torus eXperiment (NSTX) device are used to derive the energy and the torque, and these empirical evaluations are compared with theoretical calculations based on perturbed scalar pressure equilibria ƒ = ∇p coupled with the theory of nonambipolar transport. The measurement and the theory are consistent within acceptable uncertainties, but can be largely inconsistent when the torque is comparable to the energy. This is expected since the currents associated with the torque are ignored in scalar pressure equilibria, but these currents tend to shield the perturbation.
Browning, P K; Evans, M; Lucini, F Arese; Lukin, V S; McClements, K G; Stanier, A
2015-01-01
Twisted magnetic flux ropes are ubiquitous in space and laboratory plasmas, and the merging of such flux ropes through magnetic reconnection is an important mechanism for restructuring magnetic fields and releasing free magnetic energy. The merging-compression scenario is one possible start up scheme for spherical tokamaks, which has been used on the Mega Amp Spherical Tokamak MAST. Two current-carrying plasma rings, or flux ropes, approach each other through the mutual attraction of their like currents, and merge, through magnetic reconnection, into a single plasma torus, with substantial plasma heating. 2D resistive MHD and Hall MHD simulations of this process are reported, and new results for the temperature distribution of ions and electrons are presented. A model of the based on relaxation theory is also described, which is now extended to tight aspect ratio geometry. This model allows prediction of the final merged state and the heating. The implications of the relaxation model for heating of the solar ...
Design study of superconducting magnets for tokamak experimental fusion reactor, (1)
International Nuclear Information System (INIS)
Design study has been made of superconducting magnets for a Tokamak experimental fusion reactor: toroidal field magnet design, poloidal field magnet design, refrigeration system design, magnet safety analysis, and magnet assembling and disassembling system design. A maximum toroidal field in the coil is 11.0 T, providing 5.5 T at plasma center. Nb3Sn superconducting cable is used to attain the toroidal field of 11 T. The coil bore is 7.3 x 11.2 m, and the coil shape is deformed constant-tension D-shape. The magnetomotive force is 185.6 MAT, and the operational current is 25.9 kA. In poloidal field magnet design, the coil is pancake-wound Nb3Sn conductor. The conductor is enclosed in Ti-alloy sheath, which serves also as helium containment vessel. The conductor is cooled by forced flow supercritical helium of 7 atm and 4.6 K, and the operational current is 25 -- 27 kA. (author)
Nuclear Fusion: half a century of magnetic confinement research
International Nuclear Information System (INIS)
This book is written by physicists, whose distinguished carrers span most of the past half-century of fusion research. The book might be described as a scientific history. In giving a physicist's view of of fusion history, the authors are careful to document their souces, with twenty seven pages of references. They outline the roots of nuclear energy and plasma physics leading to the classification of fusion research and its declassification in 1958 in Geneva. Continuing from the profusion ideas disclosed at that time, they deal in succeding chapters with open systems, pulsed toroidal configurations and other alternatives, stellarators, and tokamaks. The concluding chapter, which is remarkably up to date, discusses the steps to a fusion reactor and th ehistory and status of ITER
Nuclear Fusion: half a century of magnetic confinement research
Energy Technology Data Exchange (ETDEWEB)
Hutchinson, I.H
2002-08-01
This book is written by physicists, whose distinguished carrers span most of the past half-century of fusion research. The book might be described as a scientific history. In giving a physicist's view of of fusion history, the authors are careful to document their souces, with twenty seven pages of references. They outline the roots of nuclear energy and plasma physics leading to the classification of fusion research and its declassification in 1958 in Geneva. Continuing from the profusion ideas disclosed at that time, they deal in succeding chapters with open systems, pulsed toroidal configurations and other alternatives, stellarators, and tokamaks. The concluding chapter, which is remarkably up to date, discusses the steps to a fusion reactor and th ehistory and status of ITER.
Forming and confinement of a dense electron cloud in an open magnetic trap
International Nuclear Information System (INIS)
Problems of formation and confinement of an electron cloud in a magnetic field of the mirror configuration are discussed in detail. The experiments show that it is possible to form a dense prolonged electron cloud by injecting electrons into the rising-in-time magnetic field. The magnetic mirror configuration may be used to confine the cloud in the system for a long time. An electron cloud with a density up to 8x109 cm-3, confinement time up to 400 μs and potential well up to 300 kV has been formed in a magnetic mirror of the open type of 50 cm long with a mirror ratio of 2 and a magnetic field up to 1.6x103 Oe rising during 4x10-4 s. Numbers of trapped particles as H functions of injected electron density, injection energy and the rate of the magnetic field rising have been studied. It is shown that a long-lived prolonged electron cloud can be formed by injecting electrons into a rising-in-time magnetic field in an open magnetic mirror and that the efficiency of cloud confinement increases with the electron injection density, the mirror length and cross section
A magnetic confinement versus rotation classification of massive-star magnetospheres
V. Petit; S.P. Owocki; G.A. Wade; D.H. Cohen; J.O. Sundqvist; M. Cagné; J. Maiz Apellaniz; M.E. Oksala; D.A. Bohlender; T. Rivinius; H.F. Henrichs; E. Alecian; R.H.D. Townsend; A. ud-Doula
2013-01-01
Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfvén radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) p
Sensing magnetic nanoparticles using nano-confined ferromagnetic resonances in a magnonic crystal
Metaxas, P. J.; Sushruth, M.; Begley, R. A.; Ding, J.; Woodward, R. C.; Maksymov, I. S.; Albert, M.; Wang, W.; Fangohr, H.; Adeyeye, A. O.; Kostylev, M.
2015-06-01
We experimentally demonstrate the use of the magnetic-field-dependence of highly spatially confined, GHz-frequency ferromagnetic resonances for the detection of magnetic nanoparticles using an anti-dot-based magnonic crystal. The stray magnetic fields of nanoparticles within the anti-dots modify nano-confined ferromagnetic resonances in the surrounding periodically nanopatterned magnonic crystal, generating easily measurable resonance peak shifts. The shifts are comparable to the resonance linewidths for high anti-dot filling fractions with their signs and magnitudes dependent upon the mode localization, consistent with micromagnetic simulation results. This is an encouraging result for the development of frequency-based nanoparticle detectors for nano-scale biosensing.
Magnetic and electrostatic confinement of plasma with tuning of electrostatic field
Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang
2008-10-21
A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.
Magnetic shielding for FEL microwave electric field diagnostic in MTX tokamak
International Nuclear Information System (INIS)
A diagnostic system for measurement of microwave electric field from free electron laser (FEL) is in preparation at JAERI under JAERI-DOE collaborative program in the Microwave Tokamak Experiment (MTX) being held at Lawrence Livermore National Laboratory in U.S.A.. That is called LAPPS (Laser Aided Particle Probe Spectroscopy). This is consist of helium neutral beam source, a dye laser and viewing optics. It is required that 1000 gauss of the magnetic field must be shielded to less than 1 gauss in order to operate these LAPPS components. New high performance soft ferrous magnetic material 'FERROPERM' and PERMALLOY are used on this purpose. This paper proposes a new method to estimate a required thickness of the magnetic shielding in a saturated region of B-H curve, that is, 'magnetic shielding calculation by Virtual Divided Layers Method (VDLM)', where the shielding layer is virtually divided in many layers in the calculation. The results are compared with a computer simulation using 'three dimensional static magnetic field code' and with experimental results in a uniform static field. (author)
International Nuclear Information System (INIS)
This part of the electricity uses chapter of the Engineers Techniques collection is entirely devoted to the technical description of Tore Supra tokamak. A thermonuclear fusion device with magnetic confinement control such as Tore Supra concentrates a huge amount of high power electro-technical and electronic equipments. These power systems play a major role and are sometimes boosted to their extreme limits. From these equipments we can find: big superconducting magnets, big cooled copper magnets, high-voltage power supplies with thyristors (320 MVA installed), several MW hyper-frequency sources, several MW accelerated atom injectors, cryogenic, heat extraction, high-vacuum pumping systems, etc.. The components developed for these applications are numerous and frequently original: superconductor for variable magnetic field, DC static circuit breaker with high switch-off capability (0.7 GVA), 2 MW tetrodes, 500 kW klystrons, 500 kW gyrotrons, very low temperature (3 deg. K) electromechanical pumps, etc.. Tore Supra is a good example of the various applications of electricity and a testimony of the constant progress of the techniques mastered by electricians. This chapter is divided in 5 parts. Part 1 gives some general informations about thermonuclear fusion research, tokamak principles and electrotechnical systems of fusion research devices. Part 2 describes the Tore Supra tokamak, its aims and specificities, its internal components, the poloidal field system and the plasma heating systems. Part 3 concerns the power pulse sources: distribution network, poloidal field power supply, plasma heating systems, and ergodic divertor power supply. Part 4 describes the permanent electric power supplies for the auxiliary systems: toroidal field, cryogenic installation, cooling-drying loops. The last chapter briefly summarizes the perspectives of nuclear fusion research. (J.S.)
International Nuclear Information System (INIS)
The research performed under this contract over the current 15 month period has concentrated on some key Phaedrus tandem mirror plasma confinement and heating issues (ambipolar potential formation due to ICRF, second harmonic ECH, ponderomotive force effects, drift-pumping calculations, moment approach to transport), on development of tokamak neoclassical MHD theory (equations, instabilities, transport), and on some tokamak-specific topics (ballooning modes on a divertor separatrix, equilibrium and resistive evolution codes for Tokapole II). Progress in these and some other miscellaneous areas are briefly summarized in this final progress report for this contract, which is to evolve into a special research grant in the future
Diamagnetic measurements on the Alcator C tokamak
International Nuclear Information System (INIS)
A procedure for determining the total thermal energy content of a magnetically confined plasma from a measurement of the plasma magnetization has been successfully implemented on the Alcator C tokamak. When a plasma is confined by a magnetic field, the kinetic pressure of the plasma is supported by an interaction between the confining magnetic field and drift currents which flow in the plasma. These drift currents induce an additional magnetic field which can be measured by means of appropriately positioned pickup coils. From a measurement of this magnetic field and of the confining magnetic field, one can calculate the spatially averaged plasma pressure, which is related to the thermal energy content of the plasma by the equation of state of the plasma. The theory on which this measurement is based is described in detail. The fields and currents which flow in the plasma are related to the confining magnetic field and the plasma pressure by requiring that the plasma be in equilibrium, i.e., by balancing the forces due to pressure gradients against those due to magnetic interactions. The apparatus used to make this measurement is described and some example data analyses are carried out
Measurement of magnetic properties of confined compact toroid plasma (spheromak)
International Nuclear Information System (INIS)
The theoretical aspect of the spheromak is described in this paper. The MS machine hardware will be explored along with the formation scheme and diagnostic systems. The magnetic pickup probes, their calibration procedures and the data analysis methods will be discussed. Observations from the probe measurements and magnetic properties of the MS spheromak are considered. The axisymmetric Grad-Shafranov equilibrium code calculations are presented and compared with the measurements. Magnetic helicity and its correlation with the experimental observations is described
Frascati Tokamak Upgrade (FTU): Results and developments
International Nuclear Information System (INIS)
In the present note the relation is examined between the FTU experimental programme and the most important issues in controlled thermonuclear fusion researches. FTU is a high-density, high magnetic field tokamak devoted to the study of plasma heating and current drive, energy and particle confinement and plasma-wall interaction. The most important FTU results and their relevance for ITER will be discussed
Tokamak with liquid metal toroidal field coil
Ohkawa, Tihiro; Schaffer, Michael J.
1981-01-01
Tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. Electric current is passed through the liquid metal over a conductive path linking the toroidal space to produce a toroidal magnetic field within the toroidal space about the major axis thereof. Toroidal plasma is developed within the toroidal space about the major axis thereof.
Magnetic surfaces and flux coordinates for omnogeneous open confinement systems
International Nuclear Information System (INIS)
For studying high β effect on a magnetic configuration it is necessary to develop approaches to numerical simulation of plasma equilibrium in open magnetic traps with in principle anisotropic plasma pressure. Information, necessary for solution of the problem, is summarized. Flux magnetic coordinates are introduced which are based on the determination of an equilibrium magnetic surface. A connection is shown of the open trap orthogonality condition with the condition of closed toroidal system quasisymmetry. The last condition follows from the requirement on existence of the charged particles drift motion equations integral. Iterative schemes are outlined for numerical solution of the equilibrium equation of plasma with anisotropic pressure and high β
Energy Technology Data Exchange (ETDEWEB)
NONE
1995-09-22
This System Design Description, prepared in accordance with the TPX Project Management Plan provides a summary or TF Magnet System design features at the conclusion of Phase I, Preliminary Design and Manufacturing Research. The document includes the analytical and experimental bases for the design, and plans for implementation in final design, manufacturing, test, and magnet integration into the tokamak. Requirements for operation and maintenance are outlined, and references to sources of additional information are provided.
International Nuclear Information System (INIS)
This System Design Description, prepared in accordance with the TPX Project Management Plan provides a summary or TF Magnet System design features at the conclusion of Phase I, Preliminary Design and Manufacturing Research. The document includes the analytical and experimental bases for the design, and plans for implementation in final design, manufacturing, test, and magnet integration into the tokamak. Requirements for operation and maintenance are outlined, and references to sources of additional information are provided
International Nuclear Information System (INIS)
Analytic calculations of the magnetic fields available to magnetic diagnostics are performed for tokamaks with circular and elliptical cross sections. The explicit dependence of the magnetic fields on the poloidal beta and internal inductances is sought. For tokamaks with circular cross sections, Shafranov's results are reproduced and extended. To first order in the inverse aspect ratio expansion of the magnetic fields, only a specific combination of beta poloidal and internal inductance is found to be measurable. To second order in the expansion, the measurements of beta poloidal and the internal inductance are demonstrated to be separable but excessively sensitive to experimental error. For tokamaks with elliptical cross sections, magnetic measurements are found to determine beta poloidal and the internal inductance separately. A second harmonic component of the zeroth order field in combination with the dc harmonic of the zeroth order field specifies the internal inductance. The internal inductance in hand, measurement of the first order, first harmonic component of the magnetic field then determined beta poloidal. The degeneracy implicit in Shafranov's result (i.e. that only a combination of beta poloidal and internal inductance is measurable for a circular plasma cross section) reasserts itself as the elliptic results are collapsed to their circular limits
Stochastization of Magnetic Field Surfaces in Tokamaks by an Inner Coil
International Nuclear Information System (INIS)
A 3-D code has been developed in order to simulate the magnetic field lines in circular cross-section tokamaks. The toroidal magnetic field can be obtained from the individual fields of circular coils arranged around the torus, or alternatively, as a ripple-less field. The poloidal field is provided by a given toroidal current density profile. Proposing initial conditions for a magnetic filed line, it is integrated along the toroidal angle coordinate, and Poincare maps can be obtained at any desired cross section plane. Following this procedure, the code allows the mapping of magnetic field surfaces for the axisymmetric case. For this work, the density current profile is chosen to be bell-shaped, so that realistic safety factor profiles can be obtained. This code is used in order to study the braking up of external surfaces when the symmetry is broken by an inner coil with tilted circular loops, with the purpose of modelling the behaviour of ergodic divertors, such as those devised for TEXTOR
Accelerating the numerical simulation of magnetic field lines in tokamaks using the GPU
International Nuclear Information System (INIS)
Highlights: → Tokamak magnetic field lines are simulated on a GPU. → Numerical integration of a set of nonlinear differential equations is required. → Using the GPU yields a significant reduction in processing time compared to the CPU. → Computational runs that took days now take hours. → These gains have been accomplished without significant hardware expense. - Abstract: TRIP3D is a field line simulation code that numerically integrates a set of nonlinear magnetic field line differential equations. The code is used to study properties of magnetic islands and stochastic or chaotic field line topologies that are important for designing non-axisymmetric magnetic perturbation coils for controlling plasma instabilities in future machines. The code is very computationally intensive and for large runs can take on the order of days to complete on a traditional single CPU. This work describes how the code was converted from Fortran to C and then restructured to take advantage of GPU computing using NVIDIA's CUDA. The reduction in computing time has been dramatic where runs that previously took days now take hours allowing a scale of problem to be examined that would previously not have been attempted. These gains have been accomplished without significant hardware expense. Performance, correctness, code flexibility, and implementation time have been analyzed to gauge the success and applicability of these methods when compared to the traditional multi-CPU approach.
Design and calibration of high-frequency magnetic probes for the SUNIST spherical tokamak.
Liu, Yangqing; Tan, Yi; Pan, Ou; Ke, Rui; Wang, Wenhao; Gao, Zhe
2014-11-01
A new high-frequency magnetic diagnostic system is designed, installed, and calibrated in the Sino-United Spherical Tokamak (SUNIST) to investigate Alfvén waves (AWs). The system consists of a fixed toroidal array and a movable radial array of high-frequency magnetic probes (HFMPs) with 21 and 60 probes, respectively. Based on the method of vacuum enameled wire wound on ceramic bobbins, the fixed toroidal array is located as near as possible to the plasma and carefully shielded to reduce the attenuation of high-frequency magnetic field. Meanwhile, by using the technology of commercial chip inductors mounted on printed circuit boards, the movable radial array is inserted into a thin quartz tube that allows positioning along radial direction. A Helmholtz coil is utilized to calibrate the effective areas as well as the frequency response of each HFMP. The calibration results are consistent with the calculated results of an equivalent probe-and-cable circuit model. High-frequency magnetic signals related to AW are detected with these HFMPs. These HFMPs are expected to play a key role in analyzing Alfvén eigenmodes excited by AW antenna in the SUNIST. PMID:25430367
Classification of particle orbits near the magnetic axis in a tokamak by using constants of motion
International Nuclear Information System (INIS)
A classification of particle orbits near the magnetic axis in a tokamak is presented in a space of constants of motion (COM), which is important to apply Lagrangian formulation of neoclassical transport theory to the region near the axis. Orbit types are distinguished by the number of the turning points of σsub(parallel)=υsub(parallel)/|υsub(parallel)| and σθ=θ-bar/|θ-bar| on each orbit, where υsub(parallel) is the velocity parallel to the magnetic field, and θ-bar(≡v·∇θ) is the poloidal angular velocity. As a set of COM, (ε, μ, ) is taken, where ε is the energy of a particle, μ is the magnetic moment, and is the bounce-averaged minor radius position of a particle orbit. Compared with a familiar set of COM (υ, ξs, rs), where υ is the particle velocity, rs is the minor radius at which an orbit crosses the mid-plane, and ξs=υsub(parallel)/υ evaluated at the crossing point, the set of COM (ε, μ, ) is more suitable in practice for Lagrangian formulation of neoclassical transport theory, in which the particle diffusion is described by the change of average position of particles by collisions. Near the magnetic axis, it is found that there are overlaps in regions of orbit types in the (ε, μ, ) space and that has a minimum value for a given ε. (author)
Magnetic monopole and confinement/deconfinement phase transition in SU(3) Yang-Mills theory
Shibata, Akihiro; Kato, Seikou; Shinohara, Toru
2015-01-01
We have proposed the non-Abelian dual superconductivity in SU(3) Yang-Mills theory for the mechanism of quark confinement,and we presented the numerical evidences in preceding lattice conferences by using the proposed gauge link decomposition to extract magnetic monopole in the gauge invariant way. In this talk, we focus on the dual Meissner effects in view of the magnetic monopole in SU(3) Yang-Mills theory. We measure the chromoelectric and chromomagnetic flux due to a pair of quark and antiquark source at finite temperature. Then, we measure the correlation function of Polyakov loops and Polyakov loop average at various temperatures, and investigate chromomagnetic monopole current induced by chromo-magnetic flux in both confinement and deconfinement phase. We will discuss the role of the chromoelectric monopole in confinement/deconfinement phase transition.
Stability analysis of tokamak plasmas
International Nuclear Information System (INIS)
In a tokamak plasma, the energy transport is mainly turbulent. In order to increase the fusion reactions rate, it is needed to improve the energy confinement. The present work is dedicated to the identification of the key parameters leading to plasmas with a better confined energy in order to guide the future experiments. For this purpose, a numerical code has been developed. It calculates the growth rates characterizing the instabilities onset. The stability analysis is completed by the evaluation of the shearing rate of the rotation due to the radial electric field. When this shearing rate is greater than the growth rate the ion turbulence is fully stabilised. The shearing rate and the growth rate are determined from the density, temperature and security factor profiles of a given plasma. Three types of plasmas have been analysed. In the Radiative Improved modes of TEXTOR, high charge number ions seeding lowers the growth rates. In Tore Supra-high density plasmas, a strong magnetic shear and/or a more efficient ion heating linked to a bifurcation of the toroidal rotation direction (which is not understood) trigger the improvement of the confinement. In other Tore Supra plasmas, locally steep electron pressure gradients have been obtained following magnetic shear reversal. This locally negative magnetic shear has a stabilizing effect. In these three families of plasmas, the growth rates decrease, the confinement improves, the density and temperature profiles are steeper. This steepening induces an increase of the rotation shearing rate, which then maintains the confinement high quality. (author)
Outgassing tests on materials used in the DIII-D magnetic fusion tokamak
International Nuclear Information System (INIS)
In order to achieve high performance plasma discharges in the DIII-D magnetic fusion tokamak, impurity levels must be carefully controlled. Since first wall materials can desorb volatile impurities during these discharges, it is important to characterize and control the outgassing of these materials. An outgassing chamber was built to measure the outgassing properties of various materials used in the DIII-D vessel. The results of pump-down tests performed on ATJ graphite, thin Grafoil reg-sign gaskets, and MgO coaxial cables will be presented. In addition to pumpdown tests it was desired to study the behavior of the materials at temperatures up to 400 C, which is the maximum temperature to which the DIII-D vessel is baked. The station was modified to include independent heating control of the sample and a simple load-lock chamber
Evaluation of Possible Nuclear Magnetic Resonance Diagnostic Techniques for Tokamak Experiments
International Nuclear Information System (INIS)
Potential applications of nuclear magnetic resonance (NMR) diagnostic techniques to tokamak experiments are evaluated. NMR frequencies for hydrogen isotopes and low-Z nuclei in such experiments are in the frequency range approximately equal to 20-200 MHz, so existing RF [radio-frequency] antennas could be used to rotate the spin polarization and to make the NMR measurements. Our tentative conclusion is that such measurements are possible if highly spin polarized H or (superscript)3He gas sources (which exist) are used to fuel these plasmas. In addition, NMR measurements of the surface layers of the first wall (without plasma) may also be possible, e.g., to evaluate the inventory of tritium inside the vessel
International Nuclear Information System (INIS)
Oscillations of the parallel and perpendicular neutral fluxes that are observed during pre-disruption stage in recent experiments, show possibility of a structure in pre-disruption phase of tokamak plasmas. This structure oscillates simultaneously with the m=2 mode until the damping of this mode. The perpendicular component of this structure is greater than the parallel one. From other side, there are a good correlation between MHD activity and behavior of charge exchange neutrals, and an enough good correlation between time behavior of charge exchange flux with high energy and OV line radiation in pre-disruption phase. These may witness possibility of a mechanism of losses-excitation of inner transition with help of heavy particles in pre-disruption phase. This mechanism plays an important role in magnetic structures in pre-disruption phase. (author)
A novel flexible field-aligned coordinate system for tokamak edge plasma simulation
Leddy, Jarrod; Romanelli, Michele; Shanahan, Brendan; Walkden, Nick
2016-01-01
Tokamak plasmas are confined by a magnetic field that limits the particle and heat transport perpendicular to the field. Parallel to the field the ionised particles can move freely, so to obtain confinement the field lines are "closed" (ie. form closed surfaces of constant poloidal flux) in the core of a tokamak. Towards, the edge, however, the field lines begin to intersect physical surfaces, leading to interaction between neutral and ionised particles, and the potential melting of the material surface. Simulation of this interaction is important for predicting the performance and lifetime of future tokamak devices such as ITER. Field-aligned coordinates are commonly used in the simulation of tokamak plasmas due to the geometry and magnetic topology of the system. However, these coordinates are limited in the geometry they allow in the poloidal plane due to orthogonality requirements. A novel 3D coordinate system is proposed herein that relaxes this constraint so that any arbitrary, smoothly varying geometry...
Poloidal and parallel plasma viscosities in tokamak geometry
International Nuclear Information System (INIS)
The poloidal and parallel plasma viscosities in tokamak geometry in Hamada coordinates are calculated from the drift kinetic equation, including a large mass flow velocity without imposing the usual constraint that VpB/(vtiBp) be small. Here, Vp is the poloidal plasma flow velocity, vti is the ion thermal speed, B is the magnetic field strength, and Bp is the poloidal magnetic field strength. With this extended validity, the poloidal and parallel viscosities are useful in modeling the radial electric field in the edge region of a tokamak in the enhanced confinement regime
International Nuclear Information System (INIS)
The 9th IAEA technical meeting on 'Energetic particles in Magnetic Confinement Systems' was held from 9 November to 11 November 2005 at Takayama, Japan. This meeting was organized by National Institute for Fusion Science, Toki, Japan. Over 60 participants attended this international meeting. 16 invited talks, 13 oral talks and 24 posters were presented. The 36 of the presented papers are indexed individually. In this meeting, the present status of experimental and theoretical studies on energetic ions and runaway electrons in various magnetic confinement geometries were discussed toward future burning plasma experiments. (J.P.N.)
Sanchez, R.; Newman, D. E.
2015-12-01
The high plasma temperatures expected at reactor conditions in magnetic confinement fusion toroidal devices suggest that near-marginal operation could be a reality in future devices and reactors. By near-marginal it is meant that the plasma profiles might wander around the local critical thresholds for the onset of instabilities. Self-organized criticality (SOC) was suggested in the mid 1990s as a more proper paradigm to describe the dynamics of tokamak plasma transport in near-marginal conditions. It advocated that, near marginality, the evolution of mean profiles and fluctuations should be considered simultaneously, in contrast to the more common view of a large separation of scales existing between them. Otherwise, intrinsic features of near-marginal transport would be missed, that are of importance to understand the properties of energy confinement. In the intervening 20 years, the relevance of the idea of SOC for near-marginal transport in fusion plasmas has transitioned from an initial excessive hype to the much more realistic standing of today, which we will attempt to examine critically in this review paper. First, the main theoretical ideas behind SOC will be described. Secondly, how they might relate to the dynamics of near-marginal transport in real magnetically confined plasmas will be discussed. Next, we will review what has been learnt about SOC from various numerical studies and what it has meant for the way in which we do numerical simulation of fusion plasmas today. Then, we will discuss the experimental evidence available from the several experiments that have looked for SOC dynamics in fusion plasmas. Finally, we will conclude by identifying the various problems that still remain open to investigation in this area. Special attention will be given to the discussion of frequent misconceptions and ongoing controversies. The review also contains a description of ongoing efforts that seek effective transport models better suited than traditional
Recent experiments and upgradation plans for Aditya Tokamak
International Nuclear Information System (INIS)
Several experiments relevant to the operation of future big tokamaks including ITER and also contributing significantly to the tokamak based thermonuclear fusion research have been carried out in Aditya tokamak recently. Low loop voltage start-up of plasma current has been successfully obtained with ICR and ECR preionization. Reduced runaway generation is achieved by applying a local vertical magnetic field at one toroidal location. Plasma disruptions, a sudden loss of equilibrium and confinement, has been successfully mitigated through application of bias voltage on a Molybdenum (Mo) electrode placed inside the last closed flux surface (LCFS). Extensive studies on plasma flows, effect of gas puff on flows in the Scrape off layer (SOL) and impurity transport has been carried out. Effect of Helium glow discharge cleaning (GDC) on partial pressures and plasma parameters have also been studied for plasma performance improvement. To contribute more to the bigger tokamaks operated in the divertor configuration, the existing Aditya tokamak with limiter configuration, which is in operation for 24 years, is planned to be upgraded to a divertor machine. The main aim of the Aditya-U tokamak is to have a small/mid-size tokamak with divertor operation and higher duty cycle, which will be test bed for new diagnostics, the students can be trained and those experiments can be tried out which are not desirable in big tokamaks, such as runaway mitigation and disruption control. Details of experimental results and upgradation plan will be discussed in the talk. (author)
Multimode observations and 3D magnetic control of the boundary of a tokamak plasma
Levesque, J. P.; Rath, N.; Shiraki, D.; Angelini, S.; Bialek, J.; Byrne, P. J.; DeBono, B. A.; Hughes, P. E.; Mauel, M. E.; Navratil, G. A.; Peng, Q.; Rhodes, D. J.; Stoafer, C. C.
2013-07-01
We present high-resolution detection and control of the 3D magnetic boundary in the High Beta Tokamak-Extended Pulse (HBT-EP) device. Measurements of non-axisymmetric radial and poloidal fields are made using 216 magnetic sensors positioned near the plasma surface. Control of 3D fields is accomplished using 40 independent saddle coils attached to the passive stabilizing wall. The control coils are energized with high-power solid-state amplifiers, and massively parallel, high-throughput feedback control experiments are performed using low-latency connections between PCI Express analogue input and output modules and a graphics processing unit. The time evolution of unstable and saturated wall-stabilized external kink modes are studied with and without applying magnetic perturbations using the control coils. The 3D dynamic structure of the magnetic field surrounding the plasma is determined through biorthogonal decomposition using the full set of magnetic sensors without the need to fit either a Fourier or a model-based basis. Naturally occurring external kinks are composed of multiple independent helical modes. Smooth transitions between dominant poloidal mode numbers are observed for simultaneous n = 1 and n = 2 modes as the edge safety factor changes. Relative amplitudes of coexistent m/n = 3/1 and 6/2 modes depend on the plasma's major radius and edge safety factor. When stationary 3/1 magnetic perturbations are applied, the resonant response can be linear, saturated, or disruptive, depending upon the perturbation amplitude and the edge safety factor; increased plasma-wall interactions from the perturbed plasma are proposed as a saturation mechanism. Initial feedback experiments have used 40 sensors and 40 control coils, producing mode amplification or suppression, and acceleration or deceleration depending on the feedback phase angle.
International Nuclear Information System (INIS)
The behaviour of the FTU tokamak plasma has been analyzed by using two reconstructive MHD equilibrium codes: the first code works by using the magnetic data alone and the second one by including as well the shape of the kinetic pressure profile, as obtained from the measured profiles of electron temperature Te and density ne. The code that analyzes the magnetic data alone provides a good evaluation of the macroscopic quantities such as the poloidal beta Bp and the internal inductance li, if the plasma elongation is greater than 1. 04. No detailed information about the toroidal current density profile Jφ and the safety factor profile q can be obtained from the magnetic data alone. On the other hand, the coupling of magnetic and kinetic data is able to provide a reasonable estimate of the toroidal current density profile and of its behaviour during the plasma discharge. The reliability of the Jφ and q profiles reconstruction has been explored and validated by a detailed comparison with the observed MHD behaviour of the FTU plasma discharges. A good agreement between the appearance of the sawtooth activity and the drop of the safety factor on the magnetic axis qo to unity is observed. Also, at least for edge safety factors qψ less than four, the sawtooth inversion radius is found to be very close to the q=1 surface. A remarkable correspondence between Jφ and Te3/2 is found in sawtoothing discharges. The structure of the snake oscillation in pellet injected discharges is found to be strictly correlated to the position of the q=1 surface. A cylindrical linear tearing mode stability calculation applied to the reconstructed Jφ profile has shown qualitative agreement with the appearance of the Mirnov oscillations. Finally the magnetic reconnections between double resonant surfaces during the rise of the plasma current or after the pellet injection have provided an interesting validation of the Jφ profile reconstruction. 56 tabs
Energy Technology Data Exchange (ETDEWEB)
Melendez L, L.; Chavez A, E.; Colunga S, S.; Valencia A, R.; Lopez C, R.; Gaytan G, E
1992-03-15
In a cylindrical magnetic topology. the confined plasma experiences 'classic' collisional transport phenomena. When bending the cylinder with the purpose of forming a toro, the magnetic field that before was uniform now it has a radial gradient which produces an unbalance in the magnetic pressure that is exercised on the plasma in the transverse section of the toro. This gives place to transport phenomena call 'neo-classicist'. In this work the structure of the toroidal magnetic field produced by toroidal coils of triangular form, to which are added even of coils of compensation with form of half moon is analyzed. With this type of coils it is looked for to minimize the radial gradient of the toroidal magnetic field. The values and characteristics of B (magnetic field) in perpendicular planes to the toro in different angular positions in the toroidal direction, looking for to cover all the cases of importance are exhibited. (Author)
Thermal Event Recognition Applied to Protection of Tokamak Plasma-Facing Components
Martin, Vincent; Travere, Jean-Marcel; Bremond, François; Moncada, Victor; Dunand, Gwenaël
2010-01-01
Magnetic confinement fusion tokamaks are complex devices where a large amount of power is required to make the fusion reactions happen. In such experimental conditions, plasma facing components (PFCs) are subjected to high heat fluxes that can damage them. Machine protection functions must then be developed to operate current and future devices like ITER inthe safest way. In current tokamaks like Tore Supra, IR thermographic diagnostics based on image analysis and feedback control are used to...
Equilibria, Dynamics and Current Sheets Formation in Magnetically Confined Coronae
Rappazzo, A F
2015-01-01
The dynamics of magnetic fields in closed regions of solar and stellar coronae are investigated with a reduced magnetohydrodynamic (MHD) model in the framework of Parker scenario for coronal heating. A novel analysis of reduced MHD equilibria shows that their magnetic fields have an asymmetric structure in the axial direction with variation length-scale $z_\\ell \\sim \\ell B_0/b$, where $B_0$ is the intensity of the strong axial guide field, $b$ that of the orthogonal magnetic field component, and $\\ell$ the scale of $\\mathbf{b}$. Equilibria are then quasi-invariant along the axial direction for variation scales larger than approximatively the loop length $z_\\ell \\gtrsim L_z$, and increasingly more asymmetric for smaller variation scales $z_\\ell \\lesssim L_z$. The $critical$ $length$ $z_\\ell \\sim L_z$ corresponds to the magnetic field intensity threshold $b \\sim \\ell B_0/L_z$. Magnetic fields stressed by photospheric motions cannot develop strong axial asymmetries. Therefore fields with intensities below such t...
Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks
Raghunathan, M.; Graves, J. P.; Cooper, W. A.; Pedro, M.; Sauter, O.
2016-09-01
We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D effects such as non-resonant internal kink modes. The first approach relies on known neoclassical coefficients in ideal MHD equilibria, using the Sauter (Sauter et al 1999 Phys. Plasmas 6 2834) expression valid for all collisionalities in axisymmetry, and the second approach being the quasi-analytic Shaing–Callen (Shaing and Callen 1983 Phys. Fluids 26 3315) model in the collisionless regime for 3D. Using the ideal free-boundary magnetohydrodynamic code VMEC, we compute the flux-surface averaged bootstrap current density, with the Sauter and Shaing–Callen expressions for 2D and 3D ideal MHD equilibria including an edge pressure barrier with the application of resonant magnetic perturbations, and equilibria possessing a saturated non-resonant 1/1 internal kink mode with a weak internal pressure barrier. We compare the applicability of the self-consistent iterative model on the 3D applications and discuss the limitations and advantages of each bootstrap current model for each type of equilibrium.
Fitzpatrick, Richard
2016-05-01
The effect of the perturbed ion polarization current on the stability of neoclassical tearing modes in tokamak plasmas is calculated using an improved, neoclassical, four-field, drift-magnetohydrodynamical model. The calculation involves the self-consistent determination of the pressure and scalar electric potential profiles in the vicinity of the associated magnetic island chain, which allows the chain's propagation velocity to be fixed. Two regimes are considered. First, a regime in which neoclassical ion poloidal flow damping is not strong enough to enhance the magnitude of the polarization current (relative to that found in slab geometry). Second, a regime in which neoclassical ion poloidal flow damping is strong enough to significantly enhance the magnitude of the polarization current. In both regimes, two types of solution are considered. First, a freely rotating solution (i.e., an island chain that is not interacting with a static, resonant, magnetic perturbation). Second, a locked solution (i.e., an island chain that has been brought to rest in the laboratory frame via interaction with a static, resonant, magnetic perturbation). In all cases, the polarization current is found to be either always stabilizing or stabilizing provided that ηi≡d ln Ti/d ln ne does not exceed some threshold value. In certain ranges of ηi, the polarization current is found to have a stabilizing effect on a freely rotating island, but a destabilizing effect on a corresponding locked island.
International Nuclear Information System (INIS)
Diagnostic of plasmas confined by magnetic fields for fusion research based on neutral lithium beam (NLB) is presently considered to be one of the most appropriate methods to carry out the important measurements of edge density and its fluctuation profiles without plasma perturbation. In this CRP project we proposed the development of an NLB source with 1-10 KeV based on a traditional β-eucryptite surface emission source coupled to a Pierce gun geometry accelerator and subsequent neutralization of the Li+ beam by a Li-oven neutralizer. Possible application of such an NLB probe in a medium term (2-3 years) in our country would be in a small RFP in operation and in a low-aspect-ratio tokamak in construction both at LAP/INPE and in other hot plasma devices operating at brazilian universities of Sao Paulo (USP) and Campinas (UNICAMP) with whom we maintain strong collaboration efforts in plasma research. (author). 8 refs
Holographic equilibration in confining gauge theories under external magnetic fields
Demircik, Tuna
2016-01-01
We investigate the effect of external magnetic fields on equilibration in the improved holographic QCD theory in the deconfined phase using the AdS/CFT correspondence. In particular we calculate the quasinormal mode spectra in the corresponding black brane solutions and study their dependence on temperature, momentum and magnetic field, both in the scalar and the shear channels. We find complex patterns in the motion of quasinormal modes on the complex plane, including certain cross overs between the lowest lying modes under varying momentum. We also find a curious dynamical instability that arise at a certain value of momentum.
Magnetic mirror confinement of high-energy, high-density plasma
Energy Technology Data Exchange (ETDEWEB)
Coensgen, F.H.; Simonen, T.C.
1979-08-21
This paper summarizes results obtained from and work in progress on those experiments which have contributed significantly toward the confinement in single-cell magnetic mirror systems of plasmas close to thermonuclear conditions. Because the mirror confinement of such high-energy, high-density plasmas has been studied most extensively in the 2XIIB experiment, discussion of 2XIIB results forms a major portion of this paper. In these experiments, injection of low-energy plasma has been shown to suppress microinstabilities to sufficiently low levels that high-beta (..beta.. approx. = 1) plasmas could be achieved and sustained by cross-field injection of beams of neutral particles. Plasma confinement was found to improve with ion energy, electron temperature, and plasma size. Based on these results, a larger Mirror Fusion Test Facility (MFTF) was designed to pursue confinement scaling to higher energies and larger plasma dimensions. MFTF design parameters and construction status are briefly reviewed.
Magnetic ripple and the modeling of lower-hybrid current drive in tokamaks
International Nuclear Information System (INIS)
Using ray tracing, a detailed investigation of the lower-hybrid (LH) wave propagation in presence of toroidal magnetic field ripple is presented. The local ray behavior is first depicted for a cylindrical equilibrium periodically modulated along the axial direction. Variations along ray trajectories in the component of the wave vector parallel to the equilibrium magnetic field are observed, with a maximum relative amplitude that is locally of the order of the ripple level. For the full rippled toroidal equilibrium, a similar local behavior is found when the ray trajectory crosses a high ripple region. Despite the modest amplitude of the local ray perturbation, its global influence on ray trajectories may be strong, as a consequence of the combined effects of toroidal and poloidal inhomogeneities. By coupling ray tracing with a one-dimensional relativistic Fokker-Planck code, simulations of LH experiments have been performed for the TORE SUPRA tokamak [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995), Vol. 1, p. 105, Paper IAEA-CN-60/A1-5]. It is shown that magnetic ripple may induce significant modifications in the LH power deposition profiles, mainly in the open-quote open-quote few passes close-quote close-quote regime when the wave makes some, but not many, passes inside the plasma before being absorbed. The effect of magnetic ripple leads then to a broadening of the power deposition profile and a shift towards the center of the plasma, and a better coupling with high energy electrons. This behavior may be explained by an increase in the overall ray stochasticity. Taking into account magnetic ripple in LH simulations, a better agreement is found between numerical predictions and experimental observations. copyright 1996 American Institute of Physics
12th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems
Energy Technology Data Exchange (ETDEWEB)
Berk, Herbert L.; Breizman, Boris N.
2014-02-21
The 12th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems took place in Austin, Texas (7–11 September 2011). This meeting was organized jointly with the 5th IAEA Technical Meeting on Theory of Plasma Instabilities (5–7 September 2011). The two meetings shared one day (7 September 2011) with presentations relevant to both groups. Some of the work reported at these meetings was then published in a special issue of Nuclear Fusion [Nucl. Fusion 52 (2012)]. Summaries of the Energetic Particle Conference presentations were given by Kazuo Toi and Boris Breizman. They respectively discussed the experimental and theoretical progress presented at the meeting. Highlights of this meeting include the tremendous progress that has been achieved in the development of diagnostics that enables the ‘viewing’ of internal fluctuations and allows comparison with theoretical predictions, as demonstrated, for example, in the talks of P. Lauber and M. Osakabe. The need and development of hardened diagnostics in the severe radiation environment, such as those that will exist in ITER, was discussed in the talks of V. Kiptily and V.A. Kazakhov. In theoretical studies, much of the effort is focused on nonlinear phenomena. For example, detailed comparison of theory and experiment on D-III-D on the n = 0 geodesic mode was reported in separate papers by R. Nazikian and G. Fu. A large number of theoretical papers were presented on wave chirping including a paper by B.N. Breizman, which notes that wave chirping from a single frequency may emanate continuously once marginal stability conditions have been established. Another area of wide interest was the detailed study of alpha orbits in a burning plasma, where losses can come from symmetry breaking due to finite coil number or magnetic field imperfections introduced by diagnostic or test modules. An important area of development, covered by M.A. Hole and D.A. Spong, is concerned with the self
International Nuclear Information System (INIS)
This report deals with investigations of plasma confinement carried out on the ASDEX divertor tokamak. It is comprised of two sections: The first section deals with the study of the condinement degradation in auxiliary heated sicharges; in the second section a regime will be described where the severe deterioration of the confinement quality at high heating power is avoided. This regime is called the H-mode because of the high confinement characteristics in contrast to the low confinement L-mode. There is evidence that the L-mode characteristics will not lead to sufficient confinement quality for successful plasma burning. The H-mode was observed for the first time on ASDEX. At present it is considered as the confinement regime with the best prospects for future tokamak operation. But both the study of L- and H-mode confinement physics have increased our understanding on energy transport in tokamaks. (orig./GG)
Fusion in a magnetically-shielded-grid inertial electrostatic confinement device
Hedditch, John; Bowden-Reid, Richard; Khachan, Joe
2015-01-01
Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented that shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively-biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales....
Mechanisms of plasma disruption and runaway electron losses in tokamaks
Abdullaev, S. S.; Finken, K. H.; Wongrach, K.; Tokar, M.; Koslowski, H. R.; Willi, O.; Zeng, L.; Team, the TEXTOR
2015-01-01
Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak the mechanisms of the formation of runaway electron beams and their losses are proposed. The plasma disruption is caused by strong stochastic magnetic field formed due to nonlinearly excited low-mode number magnetohydrodynamic (MHD) modes. It is hypothesized that the runaway electron beam is formed in the central plasma region confined by an intact magnetic surface due to the acce...
On the theory of stochastic dynamics of magnetically confined plasma
International Nuclear Information System (INIS)
This work is devoted to a study of the motion of plasma electrons in a system of two fields, a magnetic field along z-axis and wave-packet field, which propagates in the x-z plane. The strongest interaction between plasma electrons and both fields is due to their resonance with these fields. The motion of plasma electrons become stochastic when a set of resonance overlapping. Conditions for stochasticity are obtained. (orig.)
Rasouli, H; Fatehi, A; Zamanian, H
2015-03-01
In this paper, a routine algorithm is presented to design a fractional order controller for tracking the reference model. Using this algorithm, a pole placement controller can be designed by assigning the desired integer and fractional order closed loop transfer functions. Considering the desired time response and using the generalized characteristic ratio assignment (CRA) method for fractional order systems and coefficient diagram method (CDM) for integer order systems, the desired closed loop system can be achieved. For various practical experiments, having the desired time responses is vital for magnetic flux in Damavand tokamak. To approach this, at first, the desired reference models are obtained based on CRA and CDM methods. After that, a fractional order pole placement controller is designed and simulated by this algorithm. At last, this controller is implemented on a digital signal processor to control the vertical magnetic flux of Damavand tokamak plant. The practical results show the satisfactory performance of the controller. PMID:25832225
The Power Supply System for HL-2A Tokamak's Magnetic Field
Institute of Scientific and Technical Information of China (English)
XUAN Weimin; YAO Lieying; CHEN Yuhong; SHAO Kui; WANG Yingqiao
2007-01-01
The highpower pulsed power supply system for the magnetic field of the HL-2A Tokamak is described in this paper.The total output power of its eight magnetic field power supply units of nearly 250 MW.Their highest DC output voltage and current are 3510 V and 45 kA,respectively. All the units are operated in a pulsed mode.The pulse duration is 5 s,and the cyclic period is 15 min.The power supply system consists mainly of pulsed flywheel motor generators,rectifying transformers,thyristor converters,diode rectifiers and switches.The system incorporates many key technologies-supply equalization with two generators and four diode bridges,constant-angle phase triggers with a wide frequency range,current equalization,a status detector for the high current 6-phase converter,and advanced monitoring based on a programmable logic computer and engineering parameter measurement.The experimental results show that the performance of the power supply system satisfies the requirements of HL-2A experiments very well.
Classification of particle orbits near the magnetic axis in a tokamak by using constants of motion
Energy Technology Data Exchange (ETDEWEB)
Satake, Shinsuke [Department of Fusion Science, Graduate Univ. for Advanced Studies, Toki, Gifu (Japan); Sugama, Hideo; Okamoto, Masao [National Inst. for Fusion Science, Toki, Gifu (Japan); Wakatani, Masahiro [Graduate School of Energy Science, Kyoto Univ., Uji, Kyoto (Japan)
2001-01-01
A classification of particle orbits near the magnetic axis in a tokamak is presented in a space of constants of motion (COM), which is important to apply Lagrangian formulation of neoclassical transport theory to the region near the axis. Orbit types are distinguished by the number of the turning points of {sigma}sub(parallel)={upsilon}sub(parallel)/|{upsilon}sub(parallel)| and {sigma}{sub {theta}}={theta}-bar/|{theta}-bar| on each orbit, where {upsilon}sub(parallel) is the velocity parallel to the magnetic field, and {theta}-bar({identical_to}v{center_dot}{nabla}{theta}) is the poloidal angular velocity. As a set of COM, ({epsilon}, {mu},
Observation of plasma rotation driven by static nonaxisymmetric magnetic fields in a tokamak.
Garofalo, A M; Burrell, K H; DeBoo, J C; deGrassie, J S; Jackson, G L; Lanctot, M; Reimerdes, H; Schaffer, M J; Solomon, W M; Strait, E J
2008-11-01
We present the first evidence for the existence of a neoclassical toroidal rotation driven in a direction counter to the plasma current by nonaxisymmetric, nonresonant magnetic fields. At high beta and with large injected neutral beam momentum, the nonresonant field torque slows down the plasma toward the neoclassical "offset" rotation rate. With small injected neutral beam momentum, the toroidal rotation is accelerated toward the offset rotation, with resulting improvement in the global energy confinement time. The observed magnitude, direction, and radial profile of the offset rotation are consistent with neoclassical theory predictions. PMID:19113280
Intense ion beam applications to magnetic confinement fusion
International Nuclear Information System (INIS)
The ion ring project objective is to trap a ring of high energy, axis-encircling ions in a magnetic mirror. The number of ring ions should be such as to produce deltaB/B on the ring axis of order 10%. The second experiment, LONGSHOT, is directed to producing a long pulse ion beam source so that the total number of protons required for an ion ring can be provided a lower diode power and, hence, at much less cost than that of 100 nsec pulsed power generators like the NRL GAMBLE II. A detailed report of the progress on IREX and LONGSHOT is given
Wagner, F.; Becker, G.; Behringer, K.; Campbell, D.; Eberhagen, A.; Engelhardt, W.; Fussmann, G.; Gehre, O.; Gernhardt, J.; Gierke, G. V.; Haas, G.; Huang, M.; Karger, F.; Keilhacker, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lisitano, G.; Lister, G. G.; Mayer, H. M.; Meisel, D.; Müller, E. R.; Murmann, H.; Niedermeyer, H.; Poschenrieder, W.; Rapp, H.; Röhr, H.; Schneider, F.; Siller, G.; Speth, E.; Stäbler, A.; Steuer, K. H.; Venus, G.; Vollmer, O.; Yü, Z.
1982-11-01
A new operational regime has been observed in neutral-injection-heated ASDEX divertor discharges. This regime is characterized by high βp values comparable to the aspect ratio A (βp=1.9 MW, a mean density n¯e>=3×1013 cm-3, and a q(a) value >=2.6. Beyond these limits or in discharges with material limiter, low βp values and reduced particle and energy confinement times are obtained compared to the Ohmic heating phase.
Characteristics of various confinement regimes obtained with EC and LH heating on the TdeV tokamak
International Nuclear Information System (INIS)
Steady-state H-modes in type III ELM regime on TdeV with electron cyclotron and lower hybrid heating are investigated with respect to lower hybrid wave coupling, threshold power, helium pumping and separation between separatrix and surrounding structures. Energy confinement is found to improve as the distance between separatrix and divertor baffle is reduced. With off-axis EC heating, reduced particle transport is observed inside the deposition zone, but no energy transport barrier is obtained. New measurements on compact toroid fuelling are reported which indicate that further optimization of the injector is required. (author)
International Nuclear Information System (INIS)
The requirement for magnet sensors to verify the TF magnet system operation and aid in diagnostic assessment are defined. However, generally one does not specify such a system in the absence of a definition of the local I ampersand C system. Also, one would expect that there would be great benefit (economy, redundancy, compatibility, etc.) in specifying common components for all of the magnet system. Thus specifying the sensors requirement we have tried to be flexible to accommodate future adjustments to these systems
Hough Transform to study the magnetic confinement of Solar Spicules
Tavabia, E
2012-01-01
One of the important parameters of the ubiquitous spicules rising intermittently above the surface of the Sun is the variation of spicule spline orientation with respect to the solar coordinates, presumably reflecting the focusing of ejection by the coronal magnetic field. Here we first use a method of tracing limb spicules using a combination of second derivative operators in multiple directions around each pixel to enhance the visibility of fine linear part of spicules. Furthermore, the Hough transform is used for a statistical analysis of spicule orientations in different regions around the solar limb, from the pole to the equator. Our results show a large difference of spicule apparent tilt angles in regions of: (i) the solar poles, (ii) the equator, (iii) the active regions and (iv) the coronal holes. Spicules are visible in a radial direction in polar regions with a tilt angle <20 degree. The tilt angle is even reduced inside a coronal hole (open magnetic field lines) to 10 degrees and at the lower l...
Computational challenges in magnetic-confinement fusion physics
Fasoli, A.; Brunner, S.; Cooper, W. A.; Graves, J. P.; Ricci, P.; Sauter, O.; Villard, L.
2016-05-01
Magnetic-fusion plasmas are complex self-organized systems with an extremely wide range of spatial and temporal scales, from the electron-orbit scales (~10-11 s, ~ 10-5 m) to the diffusion time of electrical current through the plasma (~102 s) and the distance along the magnetic field between two solid surfaces in the region that determines the plasma-wall interactions (~100 m). The description of the individual phenomena and of the nonlinear coupling between them involves a hierarchy of models, which, when applied to realistic configurations, require the most advanced numerical techniques and algorithms and the use of state-of-the-art high-performance computers. The common thread of such models resides in the fact that the plasma components are at the same time sources of electromagnetic fields, via the charge and current densities that they generate, and subject to the action of electromagnetic fields. This leads to a wide variety of plasma modes of oscillations that resonate with the particle or fluid motion and makes the plasma dynamics much richer than that of conventional, neutral fluids.
Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid
International Nuclear Information System (INIS)
Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations
Effect of low transverse magnetic field on the confinement strength in a quasi-1D wire
Energy Technology Data Exchange (ETDEWEB)
Kumar, Sanjeev [London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH (United Kingdom); Thomas, K. J. [London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK and Department of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Smith, L. W.; Farrer, I.; Ritchie, D. A.; Jones, G. A. C.; Griffiths, J. [Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 OHE (United Kingdom); Pepper, M. [London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK and Department of Electrical and Electronic Engineering, Torrington Place, London WC1E 7JE (United Kingdom)
2013-12-04
Transport measurements in a quasi-one dimensional (1D) quantum wire are reported in the presence of low transverse magnetic field. Differential conductance shows weak quantised plateaus when the 2D electrons are squeezed electrostatically. Application of a small transverse magnetic field (0.2T) enhances the overall degree of quantisation due to the formation of magneto-electric subbands. The results show the role of magnetic field to fine tune the confinement strength in low density wires when interaction gives rise to double row formation.
Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid
Energy Technology Data Exchange (ETDEWEB)
Hedditch, John, E-mail: john.hedditch@sydney.edu.au; Bowden-Reid, Richard, E-mail: rbow3948@physics.usyd.edu.au; Khachan, Joe, E-mail: joe.khachan@sydney.edu.au [School of Physics, The University of Sydney, Sydney, New South Whales 2006 (Australia)
2015-10-15
Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations.
Confinement of ultra-cold neutron in a multiple cusp magnetic field
Energy Technology Data Exchange (ETDEWEB)
Akiyama, Nobumichi; Inoue, Nobuyuki; Nihei, Hitoshi; Kinosita, Ken-ichi [Tokyo Univ. (Japan). Faculty of Engineering
1996-08-01
A new confinement system of ultra-cold neutrons is proposed. The neutron bottle is made of a rectangular vacuum chamber with the size of 40 cm x 40 cm x 30 cm covered with arrays of bar type permanent magnets. The operation of bottle requires neither cooling system nor high electric power supply, and thereby the bottle is appropriate to use in the room which is located in controlled area. The maximum kinetic energy of neutrons confined is 20 neV. Experimental scheme to test the performance of the bottle is described. (author)
The field line map approach for simulations of magnetically confined plasmas
Stegmeir, Andreas; Maj, Omar; Hallatschek, Klaus; Lackner, Karl
2015-01-01
In the presented field line map approach the simulation domain of a tokamak is covered with a cylindrical grid, which is Cartesian within poloidal planes. Standard finite-difference methods can be used for the discretisation of perpendicular (w.r.t.~magnetic field lines) operators. The characteristic flute mode property $\\left(k_{\\parallel}\\ll k_{\\perp}\\right)$ of structures is exploited computationally by a grid sparsification in the toroidal direction. A field line following discretisation of parallel operators is then required, which is achieved via a finite difference along magnetic field lines. This includes field line tracing and interpolation or integration. The main emphasis of this paper is on the discretisation of the parallel diffusion operator. Based on the support operator method a scheme is constructed which exhibits only very low numerical perpendicular diffusion. The schemes are implemented in the new code GRILLIX, and extensive benchmarks are presented which show the validity of the approach ...
Effects of 3D Toroidally Asymmetric Magnetic Field on Tokamak Magnetic Surfaces
Lao, L. L.
2005-10-01
The effects of 3D error magnetic field on magnetic surfaces are investigated using the DIII-D internal coils (I-Coils). Slowly rotating n=1 traveling waves at 5 Hz and various amplitudes were applied to systematically perturb the edge surfaces by programming the I-Coil currents. The vertical separatrix location difference between EFIT magnetic reconstructions that assumes toroidal symmetry and Thomson scattering Te measurements responds in phase to the applied perturbed field. The oscillation amplitudes increase with the strength of the applied field but are much smaller than those expected from the applied field alone. The results indicate that plasma response is important. Various plasma response models based on results from the MHD codes MARS and GATO are being developed and compared to the experimental observations. To more accurately evaluate the effects of magnetic measurement errors, a new form of the magnetic uncertainty matrix is also being implemented into EFIT. Details will be presented.
Tokamaks: from A D Sakharov to the present (the 60-year history of tokamaks)
International Nuclear Information System (INIS)
The paper is prepared on the basis of the report presented at the session of the Physical Sciences Division of the Russian Academy of Sciences (RAS) at the Lebedev Physical Institute, RAS on 25 May 2011, devoted to the 90-year jubilee of Academician Andrei D Sakharov - the initiator of controlled nuclear fusion research in the USSR. The 60-year history of plasma research work in toroidal devices with a longitudinal magnetic field suggested by Andrei D Sakharov and Igor E Tamm in 1950 for the confinement of fusion plasma and known at present as tokamaks is described in brief. The recent (2006) agreement among Russia, the EU, the USA, Japan, China, the Republic of Korea, and India on the joint construction of the international thermonuclear experimental reactor (ITER) in France based on the tokamak concept is discussed. Prospects for using the tokamak as a thermonuclear (14 MeV) neutron source are examined. (conferences and symposia)
Tokamaks: from A D Sakharov to the present (the 60-year history of tokamaks)
Azizov, E. A.
2012-02-01
The paper is prepared on the basis of the report presented at the session of the Physical Sciences Division of the Russian Academy of Sciences (RAS) at the Lebedev Physical Institute, RAS on 25 May 2011, devoted to the 90-year jubilee of Academician Andrei D Sakharov - the initiator of controlled nuclear fusion research in the USSR. The 60-year history of plasma research work in toroidal devices with a longitudinal magnetic field suggested by Andrei D Sakharov and Igor E Tamm in 1950 for the confinement of fusion plasma and known at present as tokamaks is described in brief. The recent (2006) agreement among Russia, the EU, the USA, Japan, China, the Republic of Korea, and India on the joint construction of the international thermonuclear experimental reactor (ITER) in France based on the tokamak concept is discussed. Prospects for using the tokamak as a thermonuclear (14 MeV) neutron source are examined.
Energy Technology Data Exchange (ETDEWEB)
Strait, E. J. [General Atomics, San Diego, CA (United States); Park, J. -K. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Marmar, E. S. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Ahn, J. -W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Berkery, J. W. [Columbia Univ., New York, NY (United States); Burrell, K. H. [General Atomics, San Diego, CA (United States); Canik, J. M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Delgado-Aparicio, L. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Ferraro, N. M. [General Atomics, San Diego, CA (United States); Garofalo, A. M. [General Atomics, San Diego, CA (United States); Gates, D. A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Greenwald, M. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Kim, K. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); King, J. D. [General Atomics, San Diego, CA (United States); Lanctot, M. J. [General Atomics, San Diego, CA (United States); Lazerson, S. A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Liu, Y. Q. [Culham Science Centre, Abingdon (United Kingdom). Euratom/CCFE Association; Logan, N. C. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Lore, J. D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Menard, J. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Nazikian, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Shafer, M. W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Paz-Soldan, C. [General Atomics, San Diego, CA (United States); Reiman, A. H. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Rice, J. E. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Sabbagh, S. A. [Columbia Univ., New York, NY (United States); Sugiyama, L. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Turnbull, A. D. [General Atomics, San Diego, CA (United States); Volpe, F. [Columbia Univ., New York, NY (United States); Wang, Z. R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Wolfe, S. M. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2014-09-30
The goal of the 2014 Joint Research Target (JRT) has been to conduct experiments and analysis to investigate and quantify the response of tokamak plasmas to non-axisymmetric (3D) magnetic fields. Although tokamaks are conceptually axisymmetric devices, small asymmetries often result from inaccuracies in the manufacture and assembly of the magnet coils, or from nearby magnetized objects. In addition, non-axisymmetric fields may be deliberately applied for various purposes. Even at small amplitudes of order 10^{-4} of the main axisymmetric field, such “3D” fields can have profound impacts on the plasma performance. The effects are often detrimental (reduction of stabilizing plasma rotation, degradation of energy confinement, localized heat flux to the divertor, or excitation of instabilities) but may in some case be beneficial (maintenance of rotation, or suppression of instabilities). In general, the magnetic response of the plasma alters the 3D field, so that the magnetic field configuration within the plasma is not simply the sum of the external 3D field and the original axisymmetric field. Typically the plasma response consists of a mixture of local screening of the external field by currents induced at resonant surfaces in the plasma, and amplification of the external field by stable kink modes. Thus, validated magnetohydrodynamic (MHD) models of the plasma response to 3D fields are crucial to the interpretation of existing experiments and the prediction of plasma performance in future devices. The non-axisymmetric coil sets available at each facility allow well-controlled studies of the response to external 3D fields. The work performed in support of the 2014 Joint Research Target has included joint modeling and analysis of existing experimental data, and collaboration on new experiments designed to address the goals of the JRT. A major focus of the work was validation of numerical models through quantitative comparison to experimental data, in
Resonant fields created by spiral electric currents in Tokamaks
International Nuclear Information System (INIS)
The influence of the resonant magnetic perturbations, created by electric currents in spirals, on the plasma confinement in a tokamak with circular section and large aspect ratio is investigated. These perturbations create magnetic islands around the rational magnetic surface which has the helicity of the helicoidal currents. The intensities of these currents are calculated in order to the magnetic islands reach the limiter or others rational surfaces, what could provoke the plasma disrupture. The electric current intensities are estimated, in two spiral sets with different helicities, which create a predominantly stocastic region among the rational magnetic surfaces with these helicities. (L.C.)
International Nuclear Information System (INIS)
In present fusion devices, the H-mode is the most promising operational regime. It is characterized by a very hot core and a much colder edge. This is due to the presence of an edge transport barrier. In this thin zone located at the edge of the plasma, the turbulent flux is strongly reduced. However, this barrier is unstable and exhibits quasi-periodic relaxation oscillations. In this work, we study the control of these relaxations by resonant magnetic perturbations. We perform 3D turbulence simulations to investigate the influence of these magnetic perturbations (MP) on the barrier relaxations. In particular, we present two configurations created respectively by a multiple harmonic MP and a single harmonic MP. We find that stabilization of the relaxation oscillations can be achieved with both single and multiple harmonic MP. However, with the single harmonic MP, the energy confinement is always degraded whereas with the multiple harmonic MP, the confinement can be maintained. The different competing mechanisms at the origin of these results will be discussed (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Inertial confinement fusion implosions with imposed magnetic field compression using the OMEGA Laser
International Nuclear Information System (INIS)
Experiments applying laser-driven magnetic-flux compression to inertial confinement fusion (ICF) targets to enhance the implosion performance are described. Spherical plastic (CH) targets filled with 10 atm of deuterium gas were imploded by the OMEGA Laser, compare Phys. Plasmas 18, 056703 or Phys. Plasmas 18, 056309. Before being imploded, the targets were immersed in an 80-kG magnetic seed field. Upon laser irradiation, the high implosion velocities and ionization of the target fill trapped the magnetic field inside the capsule, and it was amplified to tens of megagauss through flux compression. At such strong magnetic fields, the hot spot inside the spherical target was strongly magnetized, reducing the heat losses through electron confinement. The experimentally observed ion temperature was enhanced by 15%, and the neutron yield was increased by 30%, compared to nonmagnetized implosions [P. Y. Chang et al., Phys. Rev. Lett. 107, 035006 (2011)]. This represents the first experimental verification of performance enhancement resulting from embedding a strong magnetic field into an ICF capsule. Experimental data for the fuel-assembly performance and magnetic field are compared to numerical results from combining the 1-D hydrodynamics code LILAC with a 2-D magnetohydrodynamics postprocessor.
Magnetic fields and thermal flux inhibition in inertial confinement fusion
International Nuclear Information System (INIS)
Of critical concern in directly driven laser fusion systems is the understanding of electron thermal transport between the region where laser light is absorbed and the ablation layer where the high pressures which accelerate the imploding shell are generated. Evidence has accumulated over the past several years which indicates that the heat flow may be strongly inhibited. Computer hydrodynamics models used to interpret experimental results have typically employed, in an ad hoc fashion, strong flux-limited diffusion which has led to fairly widespread acceptance of a flux inhibition value near f=0.03. It is shown in this paper that the observed flux inhibition can stem directly from the strong magnetic fields generated at the ablation layer as a result of modest laser asymmetries. These fields are shed from the ablation layer and fill the overdense region which strongly influences the thermal transport. The self-consistent numerical simulation of thermal transport in this environment shows strong thermal flux inhibition as interpreted from the following computational measurements: (1) reduced ablation pressures, (2) reduced implosion velocities, (3) reduced mass ablation rates, (4) density profile flattening, and (5) reduced classical absorption; all of which have been experimentally observed. The mass ablation rates obtained from the self-consistent two-dimensional model agree well with a one-dimensional model using an imposed flux inhibition factor of 0.03. (author)
Scalings of energy confinement and density limit in stellarator/heliotron
International Nuclear Information System (INIS)
Empirical scaling of energy confinement observed experimentally in stellarator/heliotron (Heliotron E, Wendelstein 7A, L2, Heliotron DR) under the condition that plasmas are heated by ECH and/or NbI is proposed. Empirical scaling of density limit obtainable under the optimum condition is proposed. These scalings are compared with those of tokamaks. The energy confinement scaling has similar power dependence as 'L mode scaling' of tokamaks. The density limit scaling seems also to indicate the upper limit of achievable density in many tokamaks. Combining the energy confinement time and the density limit scaling a transport-limited beta value is also deduced. Thus, from the viewpoint of designing a machine, there should be some compromise in determing magnetic field strength on plasma axis, average minor radius and major radius, because their dependence on confinement time and transport-limited beta value is contradicting. (J.P.N.)
Carbajal, L; Chapman, S C; Cook, J W S
2016-01-01
Ion cyclotron emission (ICE) offers unique promise as a diagnostic of the fusion born alpha-particle population in magnetically confined plasmas. Pioneering observations from JET and TFTR found that ICE intensity $P_{ICE}$ scales approximately linearly with the measured neutron flux from fusion reactions, and with the inferred concentration, $n_\\alpha/n_i$, of fusion-born alpha-particles confined within the plasma. We present fully nonlinear self-consistent kinetic simulations that reproduce this scaling for the first time. This resolves a longstanding question in the physics of fusion alpha-particle confinement and stability in MCF plasmas. It confirms the magnetoacoustic cyclotron instability (MCI) as the likely emission mechanism and greatly strengthens the basis for diagnostic exploitation of ICE in future burning plasmas.
Seiberg-Witten and 'Polyakov-like' Magnetic Bion Confinements are Continuously Connected
Energy Technology Data Exchange (ETDEWEB)
Poppitz, Erich; /Toronto U.; Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.
2012-06-01
We study four-dimensional N = 2 supersymmetric pure-gauge (Seiberg-Witten) theory and its N = 1 mass perturbation by using compactification on S{sup 1} x R{sup 3}. It is well known that on R{sup 4} (or at large S{sup 1} size L) the perturbed theory realizes confinement through monopole or dyon condensation. At small S{sup 1}, we demonstrate that confinement is induced by a generalization of Polyakov's three-dimensional instanton mechanism to a locally four-dimensional theory - the magnetic bion mechanism - which also applies to a large class of nonsupersymmetric theories. Using a large- vs. small-L Poisson duality, we show that the two mechanisms of confinement, previously thought to be distinct, are in fact continuously connected.
Quasi-2D confinement of a BEC in a combined optical and magnetic potential
International Nuclear Information System (INIS)
We have added an optical potential to a conventional time-averaged orbiting potential (TOP) trap to create a highly anisotropic hybrid trap for ultracold atoms. Axial confinement is provided by the optical potential; the maximum frequency currently obtainable in this direction is 2.2 kHz for rubidium. The radial confinement is independently controlled by the magnetic trap and can be a factor of 700 times smaller than in the axial direction. This large anisotropy is more than sufficient to confine condensates with ∼105 atoms in a quasi-2D (Q2D) regime, and we have verified this by measuring a change in the free expansion of the condensate; our results agree with a variational model
Institute of Scientific and Technical Information of China (English)
Wang Ai-Ke
2005-01-01
In the fluid model, we derive a dispersion relation for the toroidal drift modes of tokamak plasmas, including the ion pressure gradient and the magnetic field gradient and curvature. It is shown that the magnetic field gradient and curvature (MFGC) can cause instabilities at the rational surface, which are of toroidicity-induced (TI) modes. On the other hand, it is discovered that the ion pressure gradient can stabilize the present MFGC instabilities. The critical threshold of ion pressure gradient, which makes the growth rate reduced to zero, is obtained both analytically and numerically.
Inverse Magnetic Catalysis within a Confining Contact Interaction Model for Quarks
Ahmad, Aftab
2016-01-01
We evaluate the impact of an external magnetic field on the chiral symmetry and confinement-deconfinement transition temperatures by using a vector-vector contact interaction model for quarks regularized so as to include an explicit confining scale in the corresponding gap equation. Exploring the evolution of the chiral condensate and the confining scale with temperature $T$ and magnetic field strength $eB$ ($e$ represents the fundamental electric charge), we determine the pseudo-critical temperatures for the chiral ($T_c^\\chi$) and deconfinement ($T_c^c$) transitions from their inflection points, respectively. By construction, $T_c^\\chi= T_c^c$ in the chiral limit. Within a mean field approximation, we observe the magnetic catalysis phenomenon, characterized by a rising behavior of $T_c^\\chi$ and $T_c^c$ with growing $eB$. Considering a lattice inspired running coupling which monotonically decreases with $eB$, inverse magnetic catalysis takes place in our model. Our findings are also in agreement with predic...
Tanabe, Hiroshi; Inomoto, Michiaki; Ono, Yasushi; Yamada, Takuma; Imazawa, Ryota; Cheng, Chio-Zong
2016-07-01
We present results of recent studies of high power heating of magnetic reconnection, the fundamental process of several astrophysical events such as solar flare, in the Mega Amp Spherical Tokamak (MAST) - the world largest merging experiment. In addition to the previously reported significant reconnection heating up to ˜1keV [1], detailed local profiles of electron and ion temperature have been measured using a ultra-fine 300 channel Ruby- and a 130 channel YAG-Thomson scattering and a new 32 channel ion Doppler tomography diagnostics [2]. 2D profile measurement of electron temperature revealed highly localized heating structure at the X point with the characteristic scale length of 0.02-0.05m0.3T), a thick layer of closed flux surface surrounding the current sheet sustains the temperature profile for longer time than the electron and ion energy relaxation time ˜4-10ms, finally forming triple peak structures of ion and electron temperatures at the X point and in the downstream. While the peak electron temperature at the X point increases with toroidal field, the bulk electron temperature and the ion temperature in the downstream are unaffected. [1] Y. Ono et.al., Plasma Phys. Control. Fusion 54, 124039 (2012) [2] H. Tanabe et. al., Nucl. Fusion 53, 093027 (2013). [3] H. Tanabe et.al., Phys. Rev. Lett. 115, 215004 (2015)
International Nuclear Information System (INIS)
This report presents the results of ''Conceptual Studies of Toroidal Field Magnets for the Tokamak Experimental Power Reactor'' performed for the Energy Research and Development Administration, Oak Ridge Operations. Two conceptual coil designs are developed. One design approach to produce a specified 8 Tesla maximum field uses a novel NbTi superconductor design cooled by pool-boiling liquid helium. For a highest practicable field design, a unique NbSn3 conductor is used with forced-flow, single-phase liquid helium cooling to achieve a 12 Tesla peak field. Fabrication requirements are also developed for these approximately 7 meter horizontal bore by 11 meter vertical bore coils. Cryostat design approaches are analyzed and a hybrid cryostat approach selected. Structural analyses are performed for approaches to support in-plane and out-of-plane loads and a structural approach selected. In addition to the conceptual design studies, cost estimates and schedules are prepared for each of the design approaches, major uncertainties and recommendations for research and development identified, and test coil size for demonstration recommended
Calculations of alpha particle loss for reversed magnetic shear in the Tokamak Fusion Test Reactor
Energy Technology Data Exchange (ETDEWEB)
Redi, M.H.; White, R.B.; Batha, S.H.; Levinton, F.M.; McCune, D.C.
1997-03-01
Hamiltonian coordinate, guiding center code calculations of the toroidal field ripple loss of alpha particles from a reversed shear plasma predict both total alpha losses and ripple diffusion losses to be greater than those from a comparable non-reversed magnetic shear plasma in the Tokamak Fusion Test Reactor (TFTR) [Fusion Technol. 21, 1324 (1992)]. High central q is found to increase alpha ripple losses as well as first orbit losses of alphas in the reversed shear simulations. A simple ripple loss model, benchmarked against the guiding center code, is found to work satisfactorily in transport analysis modelling of reversed and monotonic shear scenarios. Alpha ripple transport on TFTR affects ions within r/a=0.5, not at the plasma edge. The entire plasma is above threshold for stochastic ripple loss of alpha particles at birth energy in the reversed shear case simulated, so that all trapped 3.5 MeV alphas are lost stochastically or through prompt losses. The 40% alpha particle loss predictions for TFTR suggest that reduction of toroidal field ripple will be a critical issue in the design of a reversed shear fusion reactor.
Design study of toroidal magnets for tokamak experimental power reactors. [NbTi alloys
Energy Technology Data Exchange (ETDEWEB)
Stekly, Z.J.J.; Lucas, E.J. (eds.)
1976-12-01
This report contains the results of a six-month study of superconducting toroidal field coils for a Tokamak Experimental Power Reactor to be built in the late 1980s. The designs are for 8 T and 12 T maximum magnetic field at the superconducting winding. At each field level two main concepts were generated; one in which each of the 16 coils comprising the system has an individual vacuum vessel and the other in which all the coils are contained in a single vacuum vessel. The coils have a D shape and have openings of 11.25 m x 7.5 m for the 8 T coils and 10.2 m x 6.8 m for the 12 T coils. All the designs utilize rectangular cabled conductor made from copper stabilized Niobium Titanium composite which operates at 4.2 K for the 8 T design and at 2.5 K for the 12 T design. Manufacturing procedures, processes and schedule estimates are also discussed.
Evaluation of hydrodynamic instabilities in inertial confinement fusion target in a magnetic field
International Nuclear Information System (INIS)
Magneto-inertial fusion (MIF) or inertial confinement fusion with magnetized target implosion is considered. Laser-driven MIF allows to compress the preseeded magnetic field to thousands of teslas. Model of high pulse energy laser target interaction is presented. Richtmyer-Meshkov (R-M) instability is investigated for MIF systems. We have shown that there is a possibility to suppress the R-M instability by magnetic field. Modeling the impact of magnetic field on a single plasma jet formed at the ICF laser target compression is performed. It is shown that at the compression and heating of a plasma target by using a rapidly growing external magnetic field and laser radiation the R-M instability can be suppressed.
Diagnostics with emissive probes in small tokamaks
International Nuclear Information System (INIS)
The toroidal magnetic confinement of a hot fusion plasma still poses extremely difficult physical problems. Especially in the edge region, where strong gradients of the plasma density, potential and temperature are present, electrostatic instabilities, appearing as oscillations, waves or fluctuations, determine the stability of the entire plasma ring and the plasma loss perpendicular to the magnetic field. Here we present a new method for a direct measurement of the electric plasma potential and its fluctuations by means of electron emissive probes, which has successfully been used in two small tokamaks, the CASTOR in Prague and the ISTTOK in Lisbon.(author)
An observational evaluation of magnetic confinement in the winds of BA supergiants
Shultz, M.; Wade, G. A.; Petit, V.; Grunhut, J.; Neiner, C.; Hanes, D.; MiMeS Collaboration
2014-02-01
Magnetic wind confinement has been proposed as one explanation for the complex wind structures of supergiant stars of spectral types B and A. Observational investigation of this hypothesis was undertaken using high-resolution (λ/Δλ ˜ 65 000) circular polarization (Stokes V) spectra of six late B- and early A-type supergiants (β Ori, B8Iae; 4 Lac, B9Iab; η Leo, A0Ib; HR1040, A0Ib; α Cyg, A2Iae; ν Cep, A2Iab), obtained with the instruments ESPaDOnS and Narval at the Canada-France-Hawaii Telescope and the Bernard Lyot Telescope. Least-squares deconvolution (LSD) analysis of the Stokes V spectra of all stars yields no evidence of a magnetic field, with best longitudinal field 1σ error bars ranging from ˜0.5 to ˜4.5 G for most stars. Spectrum synthesis analysis of the LSD profiles using Bayesian inference yields an upper limit with 95.4 per cent credibility on the polar strength of the (undetected) surface dipole fields of individual stars ranging from 3 to 30 G. These results strongly suggest that magnetic wind confinement due to organized dipolar magnetic fields is not the origin of the wind variability of BA supergiant stars. Upper limits for magnetic spots may also be inconsistent with magnetic wind confinement in the limit of large spot size and filling factor, depending on the adopted wind parameters. Therefore, if magnetic spots are responsible for the wind variability of BA supergiant stars, they likely occupy a small fraction of the photosphere.
Tokamak with liquid metal for inducing toroidal electrical field
Ohkawa, Tihiro
1981-01-01
A tokamak apparatus includes a vessel for defining a reservoir and confining liquid therein. A toroidal liner disposed within said vessel defines a toroidal space within the liner confines gas therein. Liquid metal fills the reservoir outside the liner. A magnetic field is established in the liquid metal to develop magnetic flux linking the toroidal space. The gas is ionized. The liquid metal and the toroidal space are moved relative to one another transversely of the space to generate electric current in the ionized gas in the toroidal space about its major axis and thereby heat plasma developed in the toroidal space.
International Nuclear Information System (INIS)
Nonlinear competition of turbulent structures and their roles in transport are investigated by using three-dimensional simulation code of resistive drift wave turbulence in magnetized cylindrical plasmas. Selective formation of zonal flows and streamers has been obtained by controlling the strength of damping of the zonal flow. In addition, there is an energy path from the drift waves to a flute type structure, which is linearly stable, and it becomes effective just below the stability boundary of the zonal flow. The flute structure directly induces transport effectively, and affects the drift waves and the zonal flow. A large amplitude zonal flow is formed selectively even with existence of the flute structure. The property of the particle confinement is investigated by changing the particle source intensity, which controls the strength of driving of the drift waves. The characteristic of the particle confinement changes according to turbulent states, and an improved confinement regime is obtained in the zonal flow dominant state. Study on cylindrical plasmas reveals the fundamental mechanism of improved confinement in the magnetized plasma with influence of turbulent structural formation. (paper)
Cardinali, A.; Coppi, B.; Sonnino, G.
2015-11-01
A surprising result of the most recent theory of the thermonuclear instability, which can take place in D-T plasmas close to ignition, is that it can develop with tridimensional structures emerging from an axisymmetric toroidal confinement configurations. These structures are helical filaments (``snakes'') that are localized radially around a given rational magnetic surface. Until now well known analyses of fusion burning processes in magnetically confined plasmas, that include the thermonuclear instability, have been carried out by 1+1/2 D transport codes and, consequently, the onset of tri-dimensional structures has not been investigated. The importance of the electron thermal conductivities anisotropy is pointed out also for the inhomogeneous thermonuclear burning of plasmas on the surface of pulsars and for the formation of the observed bright spots on some of them. Sponsored in part by the U.S. DoE.
Force-free magnetic system for a tokamak with superstrong magnetic field
International Nuclear Information System (INIS)
Principles of construction of the ''force-free'' magnetic system and optimization of solenoid mechanical operation are chosen according to criteria of material strength, exclusion of interturn slipping and gap opening. It is shown that induction of 20 T may be achieved in the solenoid with large torr radius (0.70-73 m)
Magnetic Bion Condensation: A New Mechanism ofConfinement and Mass Gap in Four Dimensions
Energy Technology Data Exchange (ETDEWEB)
Unsal, Mithat; /SLAC /Stanford U., Phys. Dept.
2007-09-25
In recent work, we derived the long distance confining dynamics of certain QCD-like gauge theories formulated on small S{sup 1} x R{sup 3} based on symmetries, an index theorem and abelian duality. Here, we give the microscopic derivation. The solution reveals a new mechanism of confinement in QCD(adj) in the regime where we have control over both perturbative and nonperturbative aspects. In particular, consider SU(2) QCD(adj) theory with 1 {le} n{sub f} {le} 4 Majorana fermions, a theory which undergoes gauge symmetry breaking at small S{sup 1}. If the magnetic charge of the BPS monopole is normalized to unity, we show that confinement occurs due to condensation of objects with magnetic charge 2, not 1. Due to index theorems, we know that such an object cannot be a two identical monopole configuration. Its net topological charge must vanish, and hence it must be topologically indistinguishable from the perturbative vacuum. We construct such objects, the magnetically charged, topologically null molecules of a BPS monopole and {bar K}{bar K} antimonopole, which we refer as magnetic bions. An immediate puzzle with this proposal is the apparent Coulomb repulsion between BPS-{bar K}{bar K} pair. An attraction which overcomes the Coulomb repulsion between the two is induced by 2n{sub f} -fermion exchange. Bion condensation is also the mechanism of confinement in N = 1 SYM on the same four-manifold. The SU(N) generalization hints a possible hidden integrability behind nonsupersymmetric QCD of affine Toda type, and allows us to analytically compute the string tensions and thicknesses. We currently do not know the extension to R{sup 4}.
An Observational Evaluation of Magnetic Confinement in the Winds of BA Supergiants
Shultz, M.; Wade, G. A.; Petit, V.; Grunhut, J.; Neiner, C.; Hanes, D.; collaboration, the MiMeS
2013-01-01
Magnetic wind confinement has been proposed as one explanation for the complex wind structures of supergiant stars of spectral types B and A. Observational investigation of this hypothesis was undertaken using high-resolution ({\\lambda}/{\\Delta}{\\lambda} {\\sim} 65,000) circular polarization (Stokes V ) spectra of six late B and early A type supergiants ({\\beta} Ori, B8Iae; 4 Lac, B9Iab; {\\eta} Leo, A0Ib; HR1040, A0Ib; {\\alpha} Cyg, A2Iae; {\
Development of 2D/3D equilibrium codes for magnetically confined fusion experiments
Trevisan, Gregorio Luigi
2013-01-01
The present work is the result of a three-year Ph.D. research project carried out at Consorzio RFX on magnetically confined plasmas. Research on controlled thermonuclear fusion is currently being pursued by many countries throughout the world, thanks to its promise of a relatively clean and abundant energy source. The next steps for the international community are the construction and operation of a large device, ITER, considered as the last fusion physics experiment with respect to the tokam...
An assessment of relativistic electron beam for plasma heating in magnetically confined devices
International Nuclear Information System (INIS)
The status and progress of various techniques employed for heating the plasma to thermonuclear temperature in magnetically confined devices are presented. The merits and demerits of each technique are critically studied with a view to assess the potential of Relativistic Electron Beam (REB) heating technique, which is a new comer in the field. It has been concluded that REB heating is very much suitable for linear solenoidal reactor devices and is also a potential future candidate for plasma heating for torodial devices. (auth.)
On the balance of a linear plasma column confined in a transverse magnetic field
International Nuclear Information System (INIS)
The equilibrium features are investigated of a straight plasma column being confined in a purely transverse magnetic field, part of which is being generated by external conductors. Provided that stability can be secured at high beta values, the reduced transport of particles and heat in the axial direction should allow for large axial temperature gradients. It is then expected that temperatures even leading to ignition can be achieved in a pure plasma, at technically realistic column lengths. (author)
Measurements of plasma composition in the TEXTOR tokamak by collective Thomson scattering
Stejner, M.; Korsholm, S. B.; Nielsen, S.K.; Salewski, M.; Bindslev, H.; Brezinsek, S.; Furtula, V.; Leipold, F.; Michelsen, P. K.; Meo, F.; Moseev, D.; Burger, A.; Kantor, M.; M.R. de Baar,
2012-01-01
We demonstrate the use of collective Thomson scattering (CTS) for spatially localized measurements of the isotopic composition of magnetically confined fusion plasmas. The experiments were conducted in the TEXTOR tokamak by scattering millimeter-wave probe radiation off plasma fluctuations with wave
Transport of energetic ions in MHD-active high-beta plasmas of spherical tokamaks
International Nuclear Information System (INIS)
It is shown that high β (β is the ratio of plasma pressure to the magnetic field pressure) may deteriorate the confinement of trapped energetic ions in spherical tokamaks (ST) during MHD events, such as sawtooth oscillations and internal reconnection events (IRE). This result indicates that moderate rather than very high β may be preferable in STs. (author)
Measurements of plasma composition in the TEXTOR tokamak by collective Thomson scattering
DEFF Research Database (Denmark)
Stejner Pedersen, Morten; Korsholm, Søren Bang; Nielsen, Stefan Kragh; Salewski, Mirko; Bindslev, Henrik; Brezinsek, S.; Furtula, Vedran; Leipold, Frank; Michelsen, Poul; Meo, Fernando; Moseev, Dmitry; Bürger, A.; Kantor, M.; de Baar, M.
2012-01-01
We demonstrate the use of collective Thomson scattering (CTS) for spatially localized measurements of the isotopic composition of magnetically confined fusion plasmas. The experiments were conducted in the TEXTOR tokamak by scattering millimeter-wave probe radiation off plasma fluctuations with...
Fast-ion dynamics in the TEXTOR tokamak measured by collective Thomson scattering
DEFF Research Database (Denmark)
Bindslev, H.; Nielsen, S.K.; Porte, L.; Hoekzema, J.A.; Korsholm, Søren Bang; Meo, F.; Michelsen, Poul; Michelsen, S.; Oosterbeek, J.W.; Tsakadze, E.L.; Westerhof, E.; Woskov, P.
2006-01-01
Here we present the first measurements by collective Thomson scattering of the evolution of fast-ion populations in a magnetically confined fusion plasma. 150 kW and 110 Ghz radiation from a gyrotron were scattered in the TEXTOR tokamak plasma with energetic ions generated by neutral beam injection...
Future directions of magnetic fusion research
International Nuclear Information System (INIS)
The results from the worldwide research on tokamaks together with the engineering design of the International Thermonuclear Experimental Reactor (ITER) and power plant systems studies have identified opportunities and challenges not only for the tokamak concept but for most toroidal magnetic confinement concepts. Though the tokamak configuration has been the most intensely studied to date, other magnetic configurations have been pursued to identify their potential as power plants. The experimental results from a variety of magnetic configurations together with theoretical work has deepened our understanding and has provided insights into the directions future research will take to develop an economically attractive energy source. (author). 76 refs
International Nuclear Information System (INIS)
Results of experiments on measuring mechanical stresses in a conducting turn of a model of a toroidal tokamak magnet with a strong field and combined adiabatic compression of plasma filament by a photoelastic coating method for pulse magnetic fields up to 10Tl are stated. The photoelastic method is based on that some isotropic transparent materials gain the temporary double refraction property i.e. become anisotropic. A thin layer of an optically active material is coated or glued on the object under investigation. Displacements of corresponding points of the surface of an optically active (photoelastic) layer appear during the surface deformation of the object investigated. Possibility for using photoelastic coating method for diagnostics of the model of the toroidal tokamak magnet with a strong magnetic field and combined adiabatic compression of plasma filament in the range of pulse magnetic fields up to 10Tl is shown. Regimes with fast (t approximately 0.25ms) and slow (t approximately 1.5ms) growths of a magnetic field in the magnet model were investigated
International Nuclear Information System (INIS)
The technical reports in this document were presented at the IAEA Technical Committee Meeting ''Research on Small Tokamaks'', September 1990, in three sessions, viz., (1) Plasma Modes, Control, and Internal Phenomena, (2) Edge Phenomena, and (3) Advanced Configurations and New Facilities. In Section (1) experiments at controlling low mode number modes, feedback control using external coils, lower-hybrid current drive for the stabilization of sawtooth activity and continuous (1,1) mode, and unmodulated and fast modulated ECRH mode stabilization experiments were reported, as well as the relation to disruptions and transport of low m,n modes and magnetic island growth; static magnetic perturbations by helical windings causing mode locking and sawtooth suppression; island widths and frequency of the m=2 tearing mode; ultra-fast cooling due to pellet injection; and, finally, some papers on advanced diagnostics, i.e., lithium-beam activated charge-exchange spectroscopy, and detection through laser scattering of discrete Alfven waves. In Section (2), experimental edge physics results from a number of machines were presented (positive biasing on HYBTOK II enhancing the radial electric field and improving confinement; lower hybrid current drive on CASTOR improving global particle confinement, good current drive efficiency in HT-6B showing stabilization of sawteeth and Mirnov oscillations), as well as diagnostic developments (multi-chord time resolved soft and ultra-soft X-ray plasma radiation detection on MT-1; measurements on electron capture cross sections in multi-charged ion-atom collisions; development of a diagnostic neutral beam on Phaedrus-T). Theoretical papers discussed the influence of sheared flow and/or active feedback on edge microstability, large edge electric fields, and two-fluid modelling of non-ambipolar scrape-off layers. Section (3) contained (i) a proposal to construct a spherical tokamak ''Proto-Eta'', (ii) an analysis of ultra-low-q and runaway
Magnetic bion condensation: A new mechanism of confinement and mass gap in four dimensions
Unsal, Mithat
2007-01-01
In recent work, we derived the long distance confining dynamics of certain QCD-like gauge theories formulated on small $S^1 \\times \\R^3$ based on symmetries, an index theorem and abelian duality. Here, we give the microscopic derivation. The solution reveals a new mechanism of confinement in QCD(adj) in the regime where we have control over both perturbative and nonperturbative aspects. In particular, consider $SU(2) QCD(adj)$ theory with $1 \\leq n_f \\leq 4$ Majorana fermions, a theory which undergoes gauge symmetry breaking at small $S^1$. If the magnetic charge of the BPS monopole is normalized to unity, we show that confinement occurs due to condensation of objects with magnetic charge 2, not 1. Due to index theorems, we know that such an object cannot be a two identical monopole configuration. Its net topological charge must vanish, and hence it must be topologically indistinguishable from the perturbative vacuum. We construct such objects, the magnetically charged, topologically null molecules of a BPS m...
International Nuclear Information System (INIS)
A magnetic analysis to determine plasma surface position is applied to the magnetic data of the Hitachi Tokamak (HT-2). The analysis takes account of toroidal eddy currents on the vacuum vessel wall. Magnetic probes in HT-2 are placed on both sides of the wall (plasma side and outside), making it possible to determine magnitudes of eddy currents which flow in the toroidal direction. The magnitudes of the coil currents and eddy currents are determined so as to reproduce the measured magnetic fields, and to reconstruct flux surfaces and plasma surface are reconstructed. Taking into account the eddy currents, the determination errors of the plasma surface position are reduced by up to 1/2.3 during start-up and terminating phases, compared with the case without eddy currents. (author)
A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
Petit, V; Wade, G A; Cohen, D H; Sundqvist, J O; Gagné, M; Apellániz, J Maíz; Oksala, M E; Bohlender, D A; Rivinius, Th; Henrichs, H F; Alecian, E; Townsend, R H D; ud-Doula, A
2012-01-01
Building on results from the Magnetism in Massive Stars (MiMeS) project, this paper shows how a two-parameter classification of massive-star magnetospheres in terms of the magnetic wind confinement (which sets the Alfv\\'en radius RA) and stellar rotation (which sets the Kepler co-rotation radius RK) provides a useful organisation of both observational signatures and theoretical predictions. We compile the first comprehensive study of inferred and observed values for relevant stellar and magnetic parameters of 64 confirmed magnetic OB stars with Teff > 16 kK. Using these parameters, we locate the stars in the magnetic confinement-rotation diagram, a log-log plot of RK vs. RA. This diagram can be subdivided into regimes of centrifugal magnetospheres (CM), with RA > RK, vs. dynamical magnetospheres (DM), with RK > RA. We show how key observational diagnostics, like the presence and characteristics of Halpha emission, depend on a star's position within the diagram, as well as other parameters, especially the expe...
International Nuclear Information System (INIS)
Experimental comparison of the m = 2, n = 1 mode and plasma rotation velocities at q = 2 magnetic surface in a wide range of the mode amplitudes is presented. Phase velocity of the mode rotation is measured with a set of poloidal magnetic field sensors located at the inner side of the vacuum vessel wall. Plasma rotation velocity at the q = 2 magnetic surface in the direction of the mode phase velocity is measured with the heavy ion beam probe diagnostics. In the presence of a static Resonant Magnetic Perturbation (RMP), the rotation is irregular that appears as cyclical variations of the mode and plasma instantaneous velocities. The period of these variations is equal to the period of the mode oscillations. In the case of high mode amplitude, the rotation irregularity of the mode is consistent with the rotation irregularity of the resonant plasma layer. On the contrary, the observed rise of the mode rotation irregularity in the case of low mode amplitude occurs without an increase of the rotation irregularity of the resonant plasma layer. The experimental results are simulated and analyzed with the TEAR code based on the two-fluid MHD approximation. Calculated irregularities of the mode and plasma rotation depend on the mode amplitude similar to the experimental data. For large islands, the rotation irregularity is attributed to oscillations of the electromagnetic torque applied to the resonant plasma layer. For small islands, the deviation of the mode rotation velocity from the plasma velocity occurs due to the effect of finite plasma resistivity
A procedure for the design of snowflake magnetic configurations in tokamaks
International Nuclear Information System (INIS)
This paper deals with the design of snowflake (SF) plasma configurations in tokamaks. The SF configuration represents a promising solution for the power exhaust and divertor design problem due to its ability to flare the scrape-off layer in the vicinity of the SF point. SF plasma configurations have been successfully achieved in tokamaks like Tokamak à Configuration Variable (TCV), DIII-D and National Spherical Torus Experiment (NSTX), and are under investigation for future tokamaks such as DEMO. The first attempts to determine such new plasma configurations have picked out the inherent difficulties in obtaining them with low coil currents and in controlling the associated equilibria against external disturbances and modeling errors. This paper presents a novel procedure based on the linearized model of the plasma for the design of an SF divertor configuration. Moreover, a procedure for the optimization of the poloidial field coil system is proposed. The effectiveness of the techniques is demonstrated with an application to DEMO. (paper)
Energy Technology Data Exchange (ETDEWEB)
Park, HK; Luhmann, NC; Donne, AJH; Classen, IGJ; Domier, CW; Mazzucato, E; Munsat, T; van de Pol, MJ; Xia, Z
2005-12-01
High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an "X-point" reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic.
International Nuclear Information System (INIS)
High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an 'X-point' reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic
International Nuclear Information System (INIS)
The new method that reconstructs the polar two-dimensional structure of the magnetic island using magnetic pickup coils data is introduced on HL-2A tokamak and dynamic analysis method that set up based on it for tearing mode is also introduced. In this experiment, the perturbation current which is the source of the perturbation magnetic field can be determined using the data measured by magnetic probes. Superimposing the perturbation flux and equilibrium flux reconnected by EFIT, the structure and the width of the magnetic islands can be obtained. Then two-dimensional structure maps are set up chronologically and recorded in turn. After that these maps are revealed in turn and magnetic island can be analyzed dynamically. This method is applied to analyzing tearing mode. The conclusion that magnetic island rotating direction is in accordance with electronic diamagnetic drift direction is reached. The relationship between the magnetic island width and the magnetic perturbation field is proved and the suppression of magnetic island by ECRH is also verified.It shows the immediacy of the method of inversion of magnetic island structure by magnetic probes and it is very useful for watching and controlling MHD instability. (authors)
Thermal Event Recognition Applied to Tokamak Protection during Plasma Operation
Martin, Vincent; Bremond, François; Travere, Jean-Marcel; Moncada, Victor; Dunand, Gwenaël
2009-01-01
Magnetic confinement fusion reactors are complex devices where a large amount of energy is required to make the fusion reactions happen. In such experimental conditions, the Plasma Facing Components (PFC) are subjected to high heat fluxes. In current tokamaks like Tore Supra, infrared thermographic diagnostics based on image analysis and feedback control are used to measure and monitor the heating of the PFC during plasma operation. The system consists in detecting high increase of the IR lum...
Rotation, turbulence and transport in the Tokamak de Varennes
International Nuclear Information System (INIS)
This work was undertaken to achieve greater understanding of the process of transport in a plasma under magnetic confinement in a tokamak while measuring different characteristics (speed, poloidal and toroidal rotation, ionic temperature, local emissivity, etc.) of different ionic populations (carbon, oxygen, hydrogen, etc.). An attempt was made to establish at what point transport behaviour diverges from the neoclassical theory and becomes anomalous. (L.L.) (5 figs., 1 ref.)
International Nuclear Information System (INIS)
In this paper, a simple method is presented for tuning weighted PIλ + Dμ controller parameters based on the pole placement controller of pseudo-second-order fractional systems. One of the advantages of this controller is capability of reducing the disturbance effects and improving response to input, simultaneously. In the following sections, the performance of this controller is evaluated experimentally to control the vertical magnetic flux in Damavand tokamak. For this work, at first a fractional order model is identified using output-error technique in time domain. For various practical experiments, having desired time responses for magnetic flux in Damavand tokamak, is vital. To approach this, at first the desired closed loop reference models are obtained based on generalized characteristic ratio assignment method in fractional order systems. After that, for the identified model, a set-point weighting PIλ + Dμ controller is designed and simulated. Finally, this controller is implemented on digital signal processor control system of the plant to fast/slow control of magnetic flux. The practical results show appropriate performance of this controller
Rasouli, H; Fatehi, A
2014-12-01
In this paper, a simple method is presented for tuning weighted PI(λ) + D(μ) controller parameters based on the pole placement controller of pseudo-second-order fractional systems. One of the advantages of this controller is capability of reducing the disturbance effects and improving response to input, simultaneously. In the following sections, the performance of this controller is evaluated experimentally to control the vertical magnetic flux in Damavand tokamak. For this work, at first a fractional order model is identified using output-error technique in time domain. For various practical experiments, having desired time responses for magnetic flux in Damavand tokamak, is vital. To approach this, at first the desired closed loop reference models are obtained based on generalized characteristic ratio assignment method in fractional order systems. After that, for the identified model, a set-point weighting PI(λ) + D(μ) controller is designed and simulated. Finally, this controller is implemented on digital signal processor control system of the plant to fast/slow control of magnetic flux. The practical results show appropriate performance of this controller. PMID:25554294
International Nuclear Information System (INIS)
Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the ∇ne×∇Te term in the generalized Ohm’s law. Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.
Tuning vortex confinement by magnetic domains in a superconductor/ferromagnet bilayer
Cieplak, Marta Z.; Adamus, Z.; Kończykowski, M.; Zhu, L. Y.; Cheng, X. M.; Chien, C. L.
2013-01-01
We use a line of miniature Hall sensors to study the effect of magnetic-domain-induced vortex confinement on the flux dynamics in a superconductor/ferromagnet bilayer. A single tunable bilayer is built of a ferromagnetic Co/Pt multilayer with perpendicular magnetic anisotropy and a superconducting Nb layer, with the insulating layer in-between to avoid the proximity effect. The magnetic-domain patterns of various geometries are reversibly predefined in the Co/Pt multilayer using the appropriate magnetization procedure. The magnetic-domain geometry strongly affects vortex dynamics, leading to geometry-dependent trapping of vortices at the sample edge, nonuniform flux penetration, and strongly nonuniform critical current density. With the decreasing temperature, the magnetic pinning increases, but this increase is substantially weaker than that of the intrinsic pinning. The analysis of the initial flux penetration suggests that vortices may form various vortex structures, including disordered Abrikosov lattice or single and double vortex chains, in which minimal vortex-vortex distance is comparable to the magnetic penetration depth.
Water confined in carbon nanotubes: Magnetic response and proton chemical shieldings
Huang, Patrick; Schwegler, Eric; Galli, Giulia
2009-03-01
Carbon nanotubes (CNT) provide a well-defined environment for the study of confined water, whose behavior can differ markedly from bulk water. The application of nuclear magnetic resonance (NMR) to probe the local water structure and dynamics in these cases is hindered by ambiguities in the interpretation of the NMR spectra. We employ linear response theory to evaluate the ^1H chemical shieldings of liquid water in semiconducting CNTs, where the electronic structure is derived from density functional theory with periodic boundary conditions. The shieldings are sampled from trajectories generated via first-principles molecular dynamics simulations at ambient conditions, for water in CNTs with diameters d=11 åand 14.9 å@. We find a large (˜-23 ppm) upfield shift relative to bulk liquid water, which is a consequence of strongly anisotropic magnetic fields induced in the CNT by the applied magnetic field.
Linear patterning of magnetically labeled Dictyostelium cells to display confined development
Energy Technology Data Exchange (ETDEWEB)
Frasca, Guillaume; Raynaud, Franck; Bacri, Jean-Claude; Gazeau, Florence; Wilhelm, Claire [Laboratoire Matiere et Systemes Complexes (MSC), UMR 7057 CNRS et Universite Paris-Diderot, Paris (France)], E-mail: claire.wilhelm@univ-paris-diderot.fr
2008-05-21
In severe nutriment conditions, the social amoeba Dictyostelium discoideum enters a particular life cycle where it forms multicellular patterns to achieve aggregation. Extensively observed from an initial dispersed state, its developmental program can usefully be studied from a confined population to implement theoretical developments regarding biological self-organization. The challenge is then to form a cell assembly of well-defined geometrical dimensions without hindering cell behavior. To achieve this goal, we imposed transient constraints by applying temporary external magnetic gradients to trap magnetically labeled cells. Deposits of various numbers of cells were geometrically characterized for different magnetic exposure conditions. We demonstrated that the cell deposit was organized as a three-dimensional (3D) structure by both stacking layers of cells and extending these layers in the substrate plane. This structure evolves during the aggregation phase, forming periodic aggregative centers along the linear initial pattern.
Evidence for Critical Energy for Ion Confinement in Magnetic Fusion Reactors
Maglich, Bogdan; Hester, Tim; Scott, Dan; Calsec Collaboration
2015-03-01
It is shown here that fusion test reactors could not ignite for half-a-century because trials were conducted at thermonuclear ion energies 10-30 KeV, an order of magnitude lower than critical energy, Ec ~ 200 KeV. At subcritical energies, plasma is destroyed by neutralization of ions via overlooked atomic (non-nuclear) charge transfer collisions with giant cross-section, 109 barns, 100 times greater than that for ionization collisions that counters neutralization. Neutral injection sets limit on ion magnetic confinement time 1 s required for ignition. In contrast, at energies above Ec, ionization prevails; near ~ 1 MeV, stable confinement of 20 s was routinely observed with charged injection. - To render ITER viable, ion energy must be increased to >/ = 1 MeV; neutral radioactive DT fuel replaced with charged, nonradioactive deuterium, giving rise to compact aneutronicreactor with direct conversion into RF power.
Observation of finite-. beta. MHD phenomena in tokamaks
Energy Technology Data Exchange (ETDEWEB)
McGuire, K.M.
1984-09-01
Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n > 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q/sub 0/ and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.
Experimental study of external kink instabilities in the Columbia High Beta Tokamak
International Nuclear Information System (INIS)
The generation of power through controlled thermonuclear fusion reactions in a magnetically confined plasma holds promise as a means of supplying mankind's future energy needs. The device most technologically advanced in pursuit of this goal is the tokamak, a machine in which a current-carrying toroidal plasma is thermally isolated from its surroundings by a strong magnetic field. To be viable, the tokamak reactor must produce a sufficiently large amount of power relative to that needed to sustain the fusion reactions. Plasma instabilities may severely limit this possibility. In this work, I describe experimental measurements of the magnetic structure of large-scale, rapidly-growing instabilities that occur in a tokamak when the current or pressure of the plasma exceeds a critical value relative to the magnetic field, and I compare these measurements with theoretical predictions
International Nuclear Information System (INIS)
The JSPS-CAS Core University Program (CUP) seminar on 'Production and steady-state confinement of high performance plasmas in magnetic confinement systems' was held from 27 July to 29 July 2005 in Institute of Plasma Physics, the Chinese Academy of Sciences, Hefei, China. This seminar was organized in the framework of CUP in the field of plasma and nuclear fusion. About 50 persons including 20 Japanese attendees attended this seminar. Long time sustainment of high confinement and high beta plasmas is crucial for realization of an advanced nuclear fusion reactor. This seminar was motivated to summarize the results of CUP obtained in four years activities of CUP, and to extract crucial issues to be resolved near future, which must drive near and mid- term collaborations in the framework of CUP. The 32 of presented papers are indexed individually. (J.P.N.)
Trützschler, Julia; Sentosun, Kadir; Mozooni, Babak; Mattheis, Roland; McCord, Jeffrey
2016-01-01
High density magnetic domain wall gratings are imprinted in ferromagnetic-antiferromagnetic thin films by local ion irradiation by which alternating head-to-tail-to-head-to-tail and head-to-head-to-tail-to-tail spatially overlapping domain wall networks are formed. Unique magnetic domain processes result from the interaction of anchored domain walls. Non-linear magnetization response is introduced by the laterally distributed magnetic anisotropy phases. The locally varying magnetic charge distribution gives rise to localized and guided magnetization spin-wave modes directly constrained by the narrow domain wall cores. The exchange coupled multiphase material structure leads to unprecedented static and locally modified dynamic magnetic material properties. PMID:27487941
Evolution of high-density particle clouds in magnetically confined plasmas
International Nuclear Information System (INIS)
The subject of this study is the spatial and time evolution of initially low-temperature high-density particle clouds in magnetically confined hot plasmas, such as those produced by ablating cryogenic hydrogen pellets in fusion machines. Particular attention is given to such physical processes as heating of the cloud by the energy fluxes carried by incident plasma particles (classical flux-limited energy transport by thermal electrons along the magnetic field lines, anomalous heat conduction across them), gasdynamic expansion with j vectorxB vector-produced deceleration in the transverse direction, finite-rate ionization and recombination (collisional and radiative) processes, and magnetic field convection and diffusion. The Lagrangian approximation used allows one to take into account all relevant physical processes that affect the radial expansion and deceleration of the cloud particles, including the change of the magnetic field topology. The results show the existence of a distinct structure in the ablatant cloud surrounding an ablating pellet: A hollow temperature profile coupled to a peaked density profile in the plane normal to the magnetic field direction. The lifetime of this structure is measured on hydrodynamic time scales. The basic properties of the cloud, such as its radial extent, average temperature, bulk density, etc., are complex functions of the pellet ablation rate, the parameters of the background plasma, and the magnetic field strength applied. Simple analytical or ad hoc description of this functionality, as done in present ablation models, does not seem to be possible. (orig.)
International Nuclear Information System (INIS)
We report on the magnetization of ensembles of etched quantum dots with a lateral diameter of 460 nm, which we prepared from InGaAs/InP heterostructures. The quantum dots exhibit 1/B-periodic de-Haas–van-Alphen-type oscillations in the magnetization M(B) for external magnetic fields B > 2 T, measured by torque magnetometry at 0.3 K. We compare the experimental data to model calculations assuming different confinement potentials and including ensemble broadening effects. The comparison shows that a hard wall potential with an edge depletion width of 100 nm explains the magnetic behavior. Beating patterns induced by Rashba spin–orbit interaction (SOI) as measured in unpatterned and nanopatterned InGaAs/InP heterostructures are not observed for the quantum dots. From our model we predict that signatures of SOI in the magnetization could be observed in larger dots in tilted magnetic fields. (paper)
International Nuclear Information System (INIS)
A new concept of hot plasma confinement in a miniature magnetic bottle induced by circularly polarized laser light is suggested in this work. Magnetic fields generated by circularly polarized laser light may be of the order of megagauss. In this configuration the circularly polarized laser light is used to get confinement of a plasma contained in a good conductor vessel. The poloidal magnetic field induced by the circularly polarized laser and the efficiency of laser absorption by the plasma are calculated in this work. The confinement in this scheme is supported by the magnetic forces and the Lawson criterion for a DT plasma might be achieved for number density n=5*1021 cm-3 and confinement time τ= 20 nsec. The laser and the plasma parameters required to get an energetic gain are calculated. (authors)
Ogane, S; Shikama, T; Zushi, H; Hasuo, M
2015-10-01
In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 2(3)S-2(3)P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet. PMID:26520955
Energy Technology Data Exchange (ETDEWEB)
Ogane, S.; Shikama, T., E-mail: shikama@me.kyoto-u.ac.jp; Hasuo, M. [Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University, Kyoto 615-8540 (Japan); Zushi, H. [Research Institute for Applied Mechanics, Kyushu University, Fukuoka 816-8580 (Japan)
2015-10-15
In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 2{sup 3}S–2{sup 3}P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet.
International Nuclear Information System (INIS)
In magnetically confined torus plasmas, the local emission intensity, temperature, and flow velocity of atoms in the inboard and outboard scrape-off layers can be separately measured by a passive emission spectroscopy assisted by observation of the Zeeman splitting in their spectral line shape. To utilize this technique, a near-infrared interference spectrometer optimized for the observation of the helium 23S–23P transition spectral line (wavelength 1083 nm) has been developed. The applicability of the technique to actual torus devices is elucidated by calculating the spectral line shapes expected to be observed in LHD and QUEST (Q-shu University Experiment with Steady State Spherical Tokamak). In addition, the Zeeman effect on the spectral line shape is measured using a glow-discharge tube installed in a superconducting magnet
International Nuclear Information System (INIS)
Rayleigh-Taylor (RT) instabilities at interfaces of disparate mass densities have long been known to generate magnetic fields during inertial confinement fusion implosions. An externally applied magnetic field can also be efficiently amplified by RT instabilities. The focus here is on magnetic field generation and amplification at the gas-ice interface which is RT unstable during the deceleration phase of the implosion. RT instabilities lead to undesirable mix of hot and cold plasmas which enhances thermal energy loss and tends to produce a more massive warm-spot instead of a hot-spot. Two mechanisms are shown here to mitigate the thermal energy loss from the hot-spot. The first mechanism is the reduction of electron thermal conductivity with interface-aligned magnetic fields. This can occur through self-generated magnetic fields via the Biermann battery effect as well as through externally applied magnetic fields that undergo an exponential growth via the stretch-and-fold magnetohydrodynamic dynamo. Self-generated magnetic fields during RT evolution can result in a factor of 2−10 decrease in the electron thermal conductivity at the gas-ice interface, while externally applied magnetic fields that are compressed to 6–1000 T at the onset of deceleration (corresponding to pre-implosion external fields of 0.06–10 T) could result in a factor of 2–500 reduction in electron thermal conductivity at the gas-ice interface. The second mechanism to mitigate thermal energy loss from the hot-spot is to decrease the interface mixing area between the hot and cold plasmas. This is achieved through large external magnetic fields of 1000 T at the onset of deceleration which damp short-wavelength RT modes and long-wavelength Kelvin-Helmholtz modes thus significantly slowing the RT growth and reducing mix
Self-organized criticality as a paradigm for transport in magnetically confined plasmas
International Nuclear Information System (INIS)
Many models of natural phenomena manifest the basic hypothesis of self-organized criticality (SOC) [P. Bak, C. Tang, and K. Weisenfeld, Phys. Rev. Lett., 1987, vol. 59, p. 381]. The SOC concept brings together the self-similarity on space and time scales that are common to many of these phenomena. The application of the SOC modeling concept to the plasma dynamics near marginal stability opens new possibilities of understanding issues such as Bohm scaling, profile consistency, broad-band fluctuation spectra with universal characteristics, and fast time scales. In this paper, we review the SOC concept and its possible applications to the study of transport in magnetically confined plasmas
Stimulated emission of fast Alfv\\'en waves within magnetically confined fusion plasmas
Cook, J W S; Chapman, S C
2016-01-01
A fast Alfv\\'en wave with finite amplitude is shown to grow by a stimulated emission process that we propose for exploitation in toroidal magnetically confined fusion plasmas. Stimulated emission occurs while the wave propagates inward through the outer mid-plane plasma, where a population inversion of the energy distribution of fusion-born ions is observed to arise naturally. Fully nonlinear first principles simulations, which self-consistently evolve particles and fields under the Maxwell-Lorentz system, demonstrate this novel "alpha-particle channelling" scenario for the first time.
International Nuclear Information System (INIS)
This work aims at identifying common potential problems that future fusion devices will encounter for both magnetic and inertial confinement approaches in order to promote joint efforts and to avoid duplication of research. Firstly, a comparison of radiation environments found in both fusion reaction chambers will be presented. Then, wall materials, optical components, cables and electronics will be discussed, pointing to possible future areas of common research. Finally, a brief discussion of experimental techniques available to simulate the radiation effect on materials is included.
International Nuclear Information System (INIS)
Small tokamaks may significantly contribute to the better understanding of phenomena in a wide range of fields such as plasma confinement and energy transport; plasma stability in different magnetic configurations; plasma turbulence and its impact on local and global plasma parameters; processes at the plasma edge and plasma-wall interaction; scenarios of additional heating and non-inductive current drive; new methods of plasma profile and parameter control; development of novel plasma diagnostics; benchmarking of new numerical codes and so on. Furthermore, due to the compactness, flexibility, low operation costs and high skill of their personnel small tokamaks are very convenient to develop and test new materials and technologies, which because of the risky nature cannot be done in large machines without preliminary studies. Small tokamaks are suitable and important for broad international cooperation, providing the necessary environment and manpower to conduct dedicated joint research programmes. In addition, the experimental work on small tokamaks is very appropriate for the education of students, scientific activities of post-graduate students and for the training of personnel for large tokamaks. All these tasks are well recognised and reflected in documents and understood by the large tokamak teams. Recent experimental results will be presented of contributions to mainstream fusion physics and technology research on small tokamaks involved in the IAEA Coordinated Research Project 'Joint Research using small tokamaks', started in 2004
Electric-field manipulation of spin states in confined non-magnetic/magnetic heterostructures
Energy Technology Data Exchange (ETDEWEB)
Borza, S [Departement Fysica, Universiteit Antwerpen (Campus Groenenborger), Groenenborgerlaan 171 B-2020 Antwerpen (Belgium); Peeters, F M [Departement Fysica, Universiteit Antwerpen (Campus Groenenborger), Groenenborgerlaan 171 B-2020 Antwerpen (Belgium); Vasilopoulos, P [Departement Fysica, Universiteit Antwerpen (Campus Groenenborger), Groenenborgerlaan 171 B-2020 Antwerpen (Belgium); Papp, G [Departement Fysica, Universiteit Antwerpen (Campus Groenenborger), Groenenborgerlaan 171 B-2020 Antwerpen (Belgium)
2007-04-30
The energy spectrum and states of an electron in a non-magnetic/magnetic heterostructure placed between two materials (e.g. oxides) acting as barriers is studied in the presence of a magnetic field perpendicular or parallel to the well. A potential step is formed at the interface between the non-magnetic and magnetic material in the presence of a magnetic field since spin-up electrons see a barrier whereas the spin-down ones see a well. A rich band structure is obtained which can be tuned by a perpendicular electric field. Numerical results are presented for a ZnSe/Zn{sub 1-x}Mn{sub x}Se heterostructure and their pertinence to spin-polarized transport is pointed out.
Electric-field manipulation of spin states in confined non-magnetic/magnetic heterostructures.
Borza, S; Peeters, F M; Vasilopoulos, P; Papp, G
2007-04-30
The energy spectrum and states of an electron in a non-magnetic/magnetic heterostructure placed between two materials (e.g. oxides) acting as barriers is studied in the presence of a magnetic field perpendicular or parallel to the well. A potential step is formed at the interface between the non-magnetic and magnetic material in the presence of a magnetic field since spin-up electrons see a barrier whereas the spin-down ones see a well. A rich band structure is obtained which can be tuned by a perpendicular electric field. Numerical results are presented for a ZnSe/Zn(1-x)Mn(x)Se heterostructure and their pertinence to spin-polarized transport is pointed out. PMID:21690966
Electric-field manipulation of spin states in confined non-magnetic/magnetic heterostructures
International Nuclear Information System (INIS)
The energy spectrum and states of an electron in a non-magnetic/magnetic heterostructure placed between two materials (e.g. oxides) acting as barriers is studied in the presence of a magnetic field perpendicular or parallel to the well. A potential step is formed at the interface between the non-magnetic and magnetic material in the presence of a magnetic field since spin-up electrons see a barrier whereas the spin-down ones see a well. A rich band structure is obtained which can be tuned by a perpendicular electric field. Numerical results are presented for a ZnSe/Zn1-xMnxSe heterostructure and their pertinence to spin-polarized transport is pointed out
High βp bootstrap tokamak reactor
International Nuclear Information System (INIS)
Basic characteristics of a steady state tokamak fusion reactor is presented. The minimum required energy multiplication factor Q is found to be 20 to 30 for the feasibility of the fusion reactor. Such a high Q steady state tokamak operation is possible, within our present knowledge of the operational constraints and the current drive physics, when a large fraction of the plasma current is carried by the bootstrap current. Operation at high βp (≥2.0) and high qψ (=4-5) with relatively small εβp (3) and fusion output power (2.5 GW) and is consistent with the present knowledges of the plasma physics of the tokamak, namely the Troyon limit, the energy confinement scalings, the bootstrap current, the current drive efficiency (NB current drive with the total power of 70 MW and the beam energy of 1 MeV) with a favorable aspect on the formation of the cold and dense diverter plasma-condition. From the economical aspect of the tokamak fusion reactor, a more compact reactor is favorable. The use of the high field magnet with Bmax = 16T (for example Ti-doped Nb3Sn conductor) enables to reduce the total machine size to 50% of the above-described conventional design, namely Rp = 7m, Vp = 760m-3, PF = 2.8 GW. (author)
Explosive Ballooning Flux Tubes in Tokamaks
Ham, C J; Brochard, G; Wilson, H R
2016-01-01
Tokamak stability to, potentially explosive, `ballooning' displacements of elliptical magnetic flux tubes is examined in large aspect ratio equilibrium. Above a critical pressure gradient the energy stored in the plasma may be lowered by finite (but not infinitesimal) displacements of such tubes (metastability). Above a higher pressure gradient, the linear stability boundary, such tubes are linearly and nonlinearly unstable. The flux tube displacement can be of the order of the pressure gradient scale length. Plasma transport from displaced flux tubes may result in rapid loss of confinement.
Electron cyclotron emission imaging in tokamak plasmas
Energy Technology Data Exchange (ETDEWEB)
Munsat, Tobin; Domier, Calvin W.; Kong, Xiangyu; Liang, Tianran; Luhmann, Jr.; Neville C.; Tobias, Benjamin J.; Lee, Woochang; Park, Hyeon K.; Yun, Gunsu; Classen, Ivo. G. J.; Donne, Anthony J. H.
2010-07-01
We discuss the recent history and latest developments of the electron cyclotron emission imaging diagnostic technique, wherein electron temperature is measured in magnetically confined plasmas with two-dimensional spatial resolution. The key enabling technologies for this technique are the large-aperture optical systems and the linear detector arrays sensitive to millimeter-wavelength radiation. We present the status and recent progress on existing instruments as well as new systems under development for future experiments. We also discuss data analysis techniques relevant to plasma imaging diagnostics and present recent temperature fluctuation results from the tokamak experiment for technology oriented research (TEXTOR).
International Nuclear Information System (INIS)
This document consists of a collection of papers presented at the IAEA Technical Committee Meeting on Research Using Small Tokamaks. It contains 22 papers on a wide variety of research aspects, including diagnostics, design, transport, equilibrium, stability, and confinement. Some of these papers are devoted to other concepts (stellarators, compact tori). Refs, figs and tabs
Kinetic transport in a magnetically confined and flux-constrained fusion plasma
International Nuclear Information System (INIS)
This work deals with the kinetic transport in a fusion plasma magnetically confined and flux-constrained. The author proposes a new interpretation of the dynamics of zonal flows. The model that has been studied is a gyrokinetic model reduced to the transport of trapped ions. The inter-change stability that is generated allows the study of the kinetic transport of trapped ions. This model has a threshold instability and can be simulated over a few tens confining time for either thermal bath constraint or flux constraint. For thermal baths constraint, the simulation shows a metastable state where zonal flows are prevailing while turbulence is non-existent. In the case of a flux-constraint, zonal flows appear and relax by exchanging energy with system's kinetic energy and turbulence energy. The competition between zonal flows and turbulence can be then simulated by a predator-prey model. 2 regimes can be featured out: an improved confining regime where zonal flows dominate transport and a turbulent regime where zonal flows and turbulent transport are of the same magnitude order. We show that flux as well as the Reynolds tensor play an important role in the dynamics of the zonal flows and that the gyrokinetic description is relevant for all plasma regions. (A.C.)
A midsize tokamak as a fast track to burning plasmas
Directory of Open Access Journals (Sweden)
E. Mazzucato
2011-03-01
Full Text Available This paper describes the conceptual design of a midsize tokamak as a fast track to the investigation of burning plasmas. It is shown that it could reach large values of energy gain (≥ 10 with only a modest improvement in confinement over the scaling that was used for designing the International Thermonuclear Experimental Reactor (ITER. This can be achieved by operating in a low plasma recycling regime that experiments indicate can lead to improved plasma confinement. The possibility of reaching the necessary conditions of low recycling using a different magnetic divertor from those currently employed in present experiments is discussed.
International Nuclear Information System (INIS)
The merging/ reconnection startup of high-beta ST has been developed in the TS-3/4 experiments, leading us to its new extension to the pulsed high-power heating for burning plasma formation. Two STs were produced inductively by swing-down of two or four PF coil currents without using any center solenoid (CS) and they were merged together for high-power reconnection heating. The reconnection outflow speed equals to the Alfven speed under no guiding field condition. The outflow energy is converted mostly into ion thermal energy through ion viscosity and/or fast shock, indicating that the ion temperature increment (and the thermal energy increment) scales with squares of reconnecting magnetic field (Alfven speed). This unique method has the highest heating power MW-GW among all CS-less startups and the heating time much shorter than the energy confinement time and the electron-ion collision time. These facts indicate that the merging of two STs possibly provides a direct path to the burning plasma formation. The TS-3/4 scaling data suggest that two merging STs with B=1-3T, n=1020m-3 will be transformed into an ITER-like ST with T∼20keV within reconnection time. (author)
Albert, Christopher G; Kapper, Gernot; Kasilov, Sergei V; Kernbichler, Winfried; Martitsch, Andreas F
2016-01-01
Toroidal torque generated by neoclassical viscosity caused by external non-resonant, non-axisymmetric perturbations has a significant influence on toroidal plasma rotation in tokamaks. In this article, a derivation for the expressions of toroidal torque and radial transport in resonant regimes is provided within quasilinear theory in canonical action-angle variables. The proposed approach treats all low-collisional quasilinear resonant NTV regimes including superbanana plateau and drift-orbit resonances in a unified way and allows for magnetic drift in all regimes. It is valid for perturbations on toroidally symmetric flux surfaces of the unperturbed equilibrium without specific assumptions on geometry or aspect ratio. The resulting expressions are shown to match existing analytical results in the large aspect ratio limit. Numerical results from the newly developed code NEO-RT are compared to calculations by the quasilinear version of the code NEO-2 at low collisionalities. The importance of the magnetic shea...
International Nuclear Information System (INIS)
Four sets of magnetic diagnostic coils, which are printed on machinable ceramic printed circuit boards (PCB), are designed, fabricated, installed, and tested in the Joint Texas Experimental Tokamak (J-TEXT) vacuum vessel for detecting the plasma radial and vertical displacements relative to the geometric center of the vacuum vessel in Ohmic discharges. Each coordinate is determined by a pair of variable cross-section Rogowski and saddle coils, which measure the tangential and normal magnetic fields (relative to the coil surface). These coils are suitable for mass production and offer advantages in vacuum compatibility and temperature tolerance that are important for J-TEXT. Position measurements using PCB coils are compared with those from soft x-ray image system and match the position well.
International Nuclear Information System (INIS)
The radial profiles of electrostatic and magnetic Reynolds stress (Maxwell stress) have been measured in the plasma boundary region of HT-7 tokamak. Experimental results show that the radial gradient of electrostatic Reynolds stress (ERS) changes sign across the last closed flux surface, and the neoclassical flow damping and the damping due to charge exchange processes are balanced by the radial gradient of ERS, which sustains the equilibrium sheared flow structure in a steady state. The contribution of magnetic Reynolds stress was found unimportant in a low β plasma. Detailed analyses indicate that the propagation properties of turbulence in radial and poloidal directions and the profiles of potential fluctuation level are responsible for the radial structure of ERS. (author)
International Nuclear Information System (INIS)
Fusion-product alpha particles will dominate the behavior of the next generation of ignited D-T fusion reactors. Advanced diagnostics will be required to characterize the energy deposition of these fast alpha particles in the magnetically confined plasma. For small-angle coherent Thomson scattering of a CO2 laser beam from such a plasma, a resonance in the scattered power occurs near 900 with respect to the magnetic field direction. This spatial concentration permits a simplified detection of the scattered laser power from the plasma using a heterodyne system. The signal produced by the presence of fusion-product alpha particles in an ignited plasma is calculated to be well above the noise level, which results from statistical variations of the background signal produced by scattering from free electrons. 7 refs
Energy Technology Data Exchange (ETDEWEB)
Johnson, D.J.; Crawford, M.T.; Maenchen, J.E. [Sandia National Labs., Albuquerque, NM (United States)
1996-12-31
Time resolved photographs of the visible light from the Magnetically Confined Anode Plasma (MAP) source for Ion Beam Surface Treatment (IBEST) are presented. The MAP source utilizes a fast (2 {micro}s rise time) magnetic field to create a plasma in a radially injected disc shaped gas puff and subsequently inject this plasma into the accelerating gap of a 10-cm-radius high power pulsed extraction ion diode. The 600 kV, 10 kA, 100 ns duration pulse for the beam is generated by a marx generator, cable feed, and linear induction voltage adder. The application of this technology is the generation of repetitively pulsed ion beams for government and industrial treatment of metal and polymer surfaces.
Fourth annual progress report on special-purpose materials for magnetically confined fusion reactors
International Nuclear Information System (INIS)
The scope of Special Purpose Materials covers fusion reactor materials problems other than the first-wall and blanket structural materials, which are under the purview of the ADIP, DAFS, and PMI task groups. Components that are considered as special purpose materials include breeding materials, coolants, neutron multipliers, barriers for tritium control, materials for compression and OH coils and waveguides, graphite and SiC, heat-sink materials, ceramics, and materials for high-field (>10-T) superconducting magnets. The Task Group on Special Purpose Materials has limited its concern to crucial and generic materials problems that must be resolved if magnetic-fusion devices are to succeed. Important areas specifically excluded include low-field (8-T) superconductors, fuels for hybrids, and materials for inertial-confinement devices. These areas may be added in the future when funding permits
Energy Technology Data Exchange (ETDEWEB)
Sarazin, Y
2004-03-01
This document gathers the lectures made in the framework of a Ph.D level physics class dedicated to plasma physics. This course is made up of 3 parts : 1) collisions and transport, 2) transport and turbulence, and 3) study of a few exchange instabilities. More precisely the first part deals with the following issues: thermonuclear fusion, Coulomb collisions, particles trajectories in a tokamak, neo-classical transport in tokamaks, the bootstrap current, and ware pinch. The second part involves: particle transport in tokamaks, quasi-linear transport, resonance islands, resonance in tokamaks, from quasi to non-linear transport, and non-linear saturation of turbulence. The third part deals with: shift velocities in fluid theory, a model for inter-change instabilities, Rayleigh-Benard instability, Hasegawa-Wakatani model, and Hasegawa-Mima model. This document ends with a series of appendices dealing with: particle-wave interaction, determination of the curvature parameter G, Rossby waves.
Confined partial filament eruption and its reformation within a stable magnetic flux rope
Energy Technology Data Exchange (ETDEWEB)
Joshi, Navin Chandra; Kayshap, Pradeep; Uddin, Wahab [Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263 002, Uttarakhand (India); Srivastava, Abhishek K.; Dwivedi, B. N. [Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India); Filippov, Boris [Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow (Russian Federation); Chandra, Ramesh [Department of Physics, D.S.B. Campus, Kumaun University, Nainital 263 002, Uttarakhand (India); Choudhary, Debi Prasad, E-mail: navin@aries.res.in, E-mail: njoshi98@gmail.com [California State University Northridge, 18111 Nordhoff Street, Northridge, CA 91330 (United States)
2014-05-20
We present observations of a confined partial eruption of a filament on 2012 August 4, which restores its initial shape within ≈2 hr after eruption. From the Global Oscillation Network Group Hα observations, we find that the filament plasma turns into dynamic motion at around 11:20 UT from the middle part of the filament toward the northwest direction with an average speed of ≈105 km s{sup –1}. A little brightening underneath the filament possibly shows the signature of low-altitude reconnection below the filament eruptive part. In Solar Dynamics Observatory/Atmospheric Imaging Assembly 171 Å images, we observe an activation of right-handed helically twisted magnetic flux rope that contains the filament material and confines it during its dynamical motion. The motion of cool filament plasma stops after traveling a distance of ≈215 Mm toward the northwest from the point of eruption. The plasma moves partly toward the right foot point of the flux rope, while most of the plasma returns after 12:20 UT toward the left foot point with an average speed of ≈60 km s{sup –1} to reform the filament within the same stable magnetic structure. On the basis of the filament internal fine structure and its position relative to the photospheric magnetic fields, we find filament chirality to be sinistral, while the activated enveloping flux rope shows a clear right-handed twist. Thus, this dynamic event is an apparent example of one-to-one correspondence between the filament chirality (sinistral) and the enveloping flux rope helicity (positive). From the coronal magnetic field decay index, n, calculation near the flux rope axis, it is evident that the whole filament axis lies within the domain of stability (i.e., n < 1), which provides the filament stability despite strong disturbances at its eastern foot point.
DEFF Research Database (Denmark)
Draghici, Mihai; Stamate, Eugen
2010-01-01
Highly electronegative plasmas were produced in Ar/SF6 gas mixtures in a dc discharge with multipolar magnetic confinement and transversal magnetic filter. Langmuir probe and mass spectrometry were used for plasma diagnostics. Plasma potential drift, the influence of small or large area biased...... electrodes on plasma parameters, the formation of the negative ion sheath and etching rates by positive and negative ions have been investigated for different experimental conditions. When the electron temperature was reduced below 1 eV the density ratio of negative ion to electron exceeded 100 even for very...... low amounts of SF6 gas. The plasma potential drift could be controlled by proper wall conditioning. A large electrode biased positively had no effect on plasma potential for density ratios of negative ions to electrons larger than 50. For similar electronegativities or higher a negative ion sheath...
Curling probe measurement of large-volume pulsed plasma confined by surface magnetic field
Pandey, Anil; Sakakibara, Wataru; Matsuoka, Hiroyuki; Nakamura, Keiji; Sugai, Hideo; Chubu University Team; DOWA Thermotech Collaboration
2015-09-01
Curling probe (CP) has recently been developed which enables the local electron density measurement even in plasma for non-conducting film CVD. The electron density is obtained from a shift of resonance frequency of spiral antenna in discharge ON and OFF monitored by a network analyzer (NWA). In case of a pulsed glow discharge, synchronization of discharge pulse with frequency sweep of NWA must be established. In this paper, we report time and space-resolved CP measurement of electron density in a large volume plasma (80 cm diameter, 110 cm length) confined by surface magnetic field (multipole cusp field ~0.03 T). For plasma-aided modification of metal surface, the plasma is produced by 1 kV glow discharge at pulse frequency of 0.3 - 25 kHz with various duty ratio in gas (Ar, N2, C2H2) at pressure ~ 1 Pa. A radially movable CP revealed a remarkable effect of surface magnetic confinement: detach of plasma from the vessel wall and a fairly uniform plasma in the central region. In afterglow phase, the electron density was observed to decrease much faster in C2H2 discharge than in Ar discharge.
Energy Technology Data Exchange (ETDEWEB)
Sadat, M E [University of Cincinnati; Patel, Ronak [University of Cincinnati; Sookoor, Jason [University of Cincinnati; Bud' ko, Sergey L [Ames Laboratory; Ewing, Rodney C [Stanford University; Zhang, Jiaming [Stanford University; Xu, Hong [Shanghai Jiao Tong University; Wang, Yilong [Tongji University School of Medicine; Pauletti, Giovanni M [University of Cincinnati; Mast, David B [University of Cincinnati; Shi, Donglu [University of Cincinnati
2014-09-01
In this work, the effect of nanoparticle confinement on the magnetic relaxation of iron oxide (Fe3O4) nanoparticles (NP) was investigated by measuring the hyperthermia heating behavior in high frequency alternating magnetic field. Three different Fe3O4 nanoparticle systems having distinct nanoparticle configurations were studied in terms of magnetic hyperthermia heating rate and DC magnetization. All magnetic nanoparticle (MNP) systems were constructed using equivalent ~10nm diameter NP that were structured differently in terms of configuration, physical confinement, and interparticle spacing. The spatial confinement was achieved by embedding the Fe3O4 nanoparticles in the matrices of the polystyrene spheres of 100 nm, while the unconfined was the free Fe3O4 nanoparticles well-dispersed in the liquid via PAA surface coating. Assuming the identical core MNPs in each system, the heating behavior was analyzed in terms of particle freedom (or confinement), interparticle spacing, and magnetic coupling (or dipole-dipole interaction). DC magnetization data were correlated to the heating behavior with different material properties. Analysis of DC magnetization measurements showed deviation from classical Langevin behavior near saturation due to dipole interaction modification of the MNPs resulting in a high magnetic anisotropy. It was found that the Specific Absorption Rate (SAR) of the unconfined nanoparticle systems were significantly higher than those of confined (the MNPs embedded in the polystyrene matrix). This increase of SAR was found to be attributable to high Néel relaxation rate and hysteresis loss of the unconfined MNPs. It was also found that the dipole-dipole interactions can significantly reduce the global magnetic response of the MNPs and thereby decrease the SAR of the nanoparticle systems.
Sadat, M E; Patel, Ronak; Sookoor, Jason; Bud'ko, Sergey L; Ewing, Rodney C; Zhang, Jiaming; Xu, Hong; Wang, Yilong; Pauletti, Giovanni M; Mast, David B; Shi, Donglu
2014-09-01
In this work, the effect of nanoparticle confinement on the magnetic relaxation of iron oxide (Fe3O4) nanoparticles (NP) was investigated by measuring the hyperthermia heating behavior in high frequency alternating magnetic field. Three different Fe3O4 nanoparticle systems having distinct nanoparticle configurations were studied in terms of magnetic hyperthermia heating rate and DC magnetization. All magnetic nanoparticle (MNP) systems were constructed using equivalent ~10nm diameter NP that were structured differently in terms of configuration, physical confinement, and interparticle spacing. The spatial confinement was achieved by embedding the Fe3O4 nanoparticles in the matrices of the polystyrene spheres of 100 nm, while the unconfined was the free Fe3O4 nanoparticles well-dispersed in the liquid via PAA surface coating. Assuming the identical core MNPs in each system, the heating behavior was analyzed in terms of particle freedom (or confinement), interparticle spacing, and magnetic coupling (or dipole-dipole interaction). DC magnetization data were correlated to the heating behavior with different material properties. Analysis of DC magnetization measurements showed deviation from classical Langevin behavior near saturation due to dipole interaction modification of the MNPs resulting in a high magnetic anisotropy. It was found that the Specific Absorption Rate (SAR) of the unconfined nanoparticle systems were significantly higher than those of confined (the MNPs embedded in the polystyrene matrix). This increase of SAR was found to be attributable to high Néel relaxation rate and hysteresis loss of the unconfined MNPs. It was also found that the dipole-dipole interactions can significantly reduce the global magnetic response of the MNPs and thereby decrease the SAR of the nanoparticle systems. PMID:25063092
Bifurcated Helical Core Equilibrium States in Tokamaks
International Nuclear Information System (INIS)
Full text: Tokamaks with weak to moderate reversed central magnetic shear in which the minimum of the inverse rotational transform qmin is in the neighbourhood of unity can trigger bifurcated MagnetoHydroDynamic (MHD) equilibrium states. In addition to the standard axisymmetric branch that can be obtained with standard Grad-Shafranov solvers, a novel branch with a three-dimensional (3D) helical core has been computed with the ANIMEC code, an anisotropic pressure extension of the VMEC code. The solutions have imposed nested magnetic flux surfaces and are similar to saturated ideal internal kink modes. The difference in energy between both possible branches is very small. Plasma elongation, current and β enhance the susceptibility for bifurcations to occur. An initial value nonlinear ideal MHD evolution of the axisymmetric branch compares favourably with the helical core equilibrium structures calculated. Peaked prescribed pressure profiles reproduce the 'snake' structures observed in many tokamaks which has led to a new explanation of the snake as a bifurcated helical equilibrium state that results from a saturated ideal internal kink in which pellets or impurities induce a hollow current profile. Snake equilibrium structures are computed in free boundary TCV tokamak simulations. Magnetic field ripple and resonant magnetic perturbations in MAST free boundary calculations do not alter the helical core deformation in a significant manner when qmin is near unity. These bifurcated solutions constitute a paradigm shift that motivates the application of tools developed for stellarator research in tokamak physics investigations. The examination of fast ion confinement in this class of equilibria is performed with the VENUS code in which a coordinate independent noncanonical phase-space Lagrangian formulation of guiding centre drift orbit theory has been implemented. (author)
Study of energy transport in Tore Supra Tokamak
International Nuclear Information System (INIS)
The goal of this thesis is to characterize the energy confinement and the heat transport in Tore Supra tokamak. The first chapter is an introduction to the different plasma confinement regimes: ohmic, low confinement and improved confinement regimes. The second chapter is devoted to the presentation of the different theoretical and empirical approaches about energy confinement and heat transport. In the third chapter an attempt of explanations for non-local transport phenomenons is given. A turbulence correlation length greater than the ionic Larmor radius seams to be a reasonable explanation. This theoretical study focusses on the possibility for modes coupling in a tokamak. This study tries to determine a radial correlation length considering the two principal coupling modes: toroidal and non-linear. Different transport regimes are discussed using an analytical model and considering the influence of one coupling with respect to the other. In chapter four, the measurements of current profiles and transport coefficients are presented. The codes used for the reconstruction of equilibrium and for the experimental determination of the diffusivity are briefly presented. In chapter five, experimental results of energy transport studies for Tore Supra plasmas are presented. The different modes are analysed in detail and the study focusses on the influence of magnetic shear in the improved confinement regime. Finally, the different parametric dependences of the electronic thermal diffusivity are compared to local transport models. 165 refs., 57 figs., 2 tabs., 2 appendix
Magnetic Reconnection Rates and Energy Release in a Confined X-class Flare
Veronig, A M
2015-01-01
We study the energy-release process in the confined X1.6 flare that occurred on 22 October 2014 in AR 12171. Magnetic-reconnection rates and reconnection fluxes are derived from three different data sets: space-based data from the Atmospheric Imaging Assembly (AIA) 1600 {\\AA} filter onboard the Solar Dynamics Observatory (SDO) and ground-based H$\\alpha$ and Ca II K filtergrams from Kanzelh\\"ohe Observatory. The magnetic-reconnection rates determined from the three data sets all closely resemble the temporal profile of the hard X-rays measured by the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), which are a proxy for the flare energy released into high-energy electrons. The total magnetic-reconnection flux derived lies between $4.1 \\times 10^{21}$ Mx (AIA 1600 {\\AA}) and $7.9 \\times 10^{21}$ Mx (H$\\alpha$), which corresponds to about 2 to 4% of the total unsigned flux of the strong source AR. Comparison of the magnetic-reconnection flux dependence on the GOES class for 27 eruptive events collected fr...
International Nuclear Information System (INIS)
Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage
Natural organic matter removal by adsorption onto magnetic permanently confined micelle arrays
International Nuclear Information System (INIS)
Highlights: → New nanostructured material for removing pollutants from water. → Confined surfactant micelle array allows for reuse of surfactant and reduces loss. → Magnetic core allows easy removal from solution with lower separation costs. → High removal efficiency of natural organic matter. → Low energy use for regeneration of adsorbent. - Abstract: To remove natural organic matter (NOM) from water, magnetic permanently confined micelle arrays (Mag-PCMAs) were synthesized by coating the surface of Fe3O4 particles with a silica/surfactant mesostructured hybrid layer. An environmental scanning electron microscope (ESEM) was used to characterize the particle size and surface morphology of the Mag-PCMAs. The zeta potential was used to assess the surface charge. Batch experiments were performed to investigate the adsorption of NOM by Mag-PCMAs. It was determined that NOM removal efficiency by Mag-PCMAs could be as high as 80% at a wide range of initial pH values (∼6.0-10.0). The adsorption isotherm was fitted well by a Langmuir model. Although Fe3O4 had a high positive charge and Mag-PCMAs a small negative charge, Mag-PCMAs had a higher removal efficiency of NOM than uncoated Fe3O4 particles (which are also magnetic), which indicated that the adsorption of NOM onto Mag-PCMAs was not dominated by electrostatic interactions. Possible mechanisms of the adsorption of NOM onto Mag-PCMAs were hydrophobic interactions and hydrogen bonding. It was feasible to reuse Mag-PCMAs after regeneration. These results indicate that Mag-PCMAs can be very attractive for the removal of NOM from aqueous matrices.
SCR-1: Design and construction of a small modular stellarator for magnetic confinement of plasma
International Nuclear Information System (INIS)
This paper describes briefly the design and construction of a small modular stellarator for magnetic confinement of plasma, called Stellarator of Costa Rica 1, or SCR-1; developed by the Plasma Physics Group of the Instituto Tecnológico de Costa Rica, PlasmaTEC. The SCR-1 is based on the small Spanish stellarator UST1, created by the engineer Vicente Queral. The SCR-1 will employ stainless steel torus-shaped vacuum vessel with a major radius of 460.33 mm and a cross section radius of 110.25 mm. A typical SCR-1 plasma will have an average radius 42.2 mm and a volume of 8 liters (0.01 m3), and an aspect ratio of 5.7. The magnetic resonant field will be 0.0878 T, and a period of 2 (m=2) with a rotational transform of 0.3. The magnetic field will be provided by 12 modular coils, with 8 turns each, with an electrical current of 8704 A per coil (1088 A per turn of each coil). This current will be fed by a bank of cell batteries. The plasma will be heated by ECRH with magnetrons of a total power of 5 kW, in the first harmonic at 2.45 GHz. The expected electron temperature and density are 15 eV and 1017 m−3 respectively with an estimated confinement time of 7.30 x 10−4 ms. The initial diagnostics on the SCR-1 will consist of a Langmuir probe, a heterodyne microwave interferometer, and a field mapping system. The first plasma of the SCR-1 is expected at the end of 2011.
Stability analysis of tokamak plasmas; Analyse de stabilite de plasmas de tokamak
Energy Technology Data Exchange (ETDEWEB)
Bourdelle, C
2000-10-01
In a tokamak plasma, the energy transport is mainly turbulent. In order to increase the fusion reactions rate, it is needed to improve the energy confinement. The present work is dedicated to the identification of the key parameters leading to plasmas with a better confined energy in order to guide the future experiments. For this purpose, a numerical code has been developed. It calculates the growth rates characterizing the instabilities onset. The stability analysis is completed by the evaluation of the shearing rate of the rotation due to the radial electric field. When this shearing rate is greater than the growth rate the ion turbulence is fully stabilised. The shearing rate and the growth rate are determined from the density, temperature and security factor profiles of a given plasma. Three types of plasmas have been analysed. In the Radiative Improved modes of TEXTOR, high charge number ions seeding lowers the growth rates. In Tore Supra-high density plasmas, a strong magnetic shear and/or a more efficient ion heating linked to a bifurcation of the toroidal rotation direction (which is not understood) trigger the improvement of the confinement. In other Tore Supra plasmas, locally steep electron pressure gradients have been obtained following magnetic shear reversal. This locally negative magnetic shear has a stabilizing effect. In these three families of plasmas, the growth rates decrease, the confinement improves, the density and temperature profiles are steeper. This steepening induces an increase of the rotation shearing rate, which then maintains the confinement high quality. (author)
Energy Technology Data Exchange (ETDEWEB)
Guiziou, L.
1995-12-18
The goal of this thesis is to characterize the energy confinement and the heat transport in Tore Supra tokamak. The first chapter is an introduction to the different plasma confinement regimes: ohmic, low confinement and improved confinement regimes. The second chapter is devoted to the presentation of the different theoretical and empirical approaches about energy confinement and heat transport. In the third chapter an attempt of explanations for non-local transport phenomenons is given. A turbulence correlation length greater than the ionic Larmor radius seams to be a reasonable explanation. This theoretical study focusses on the possibility for modes coupling in a tokamak. This study tries to determine a radial correlation length considering the two principal coupling modes: toroidal and non-linear. Different transport regimes are discussed using an analytical model and considering the influence of one coupling with respect to the other. In chapter four, the measurements of current profiles and transport coefficients are presented. The codes used for the reconstruction of equilibrium and for the experimental determination of the diffusivity are briefly presented. In chapter five, experimental results of energy transport studies for Tore Supra plasmas are presented. The different modes are analysed in detail and the study focusses on the influence of magnetic shear in the improved confinement regime. Finally, the different parametric dependences of the electronic thermal diffusivity are compared to local transport models. 165 refs., 57 figs., 2 tabs., 2 appendix.
International Nuclear Information System (INIS)
The modified Rogowski sine-coil (MRSC) has been designed and implemented for the plasma column horizontal displacement measurements on small IR-T1 tokamak. MRSC operation has been examined on test assembly and tokamak. Obtained results show high sensitivity to the plasma column horizontal displacement and negligible sensitivity to the vertical displacement; linearity in wide, ±0.1 m, range of the displacements; and excellent, 1.5%, agreement with the results of numerical solution of Biot-Savart and magnetic flux equations.
Wahlberg, C.; Graves, J. P.
2016-07-01
Ideal magnetohydrodynamic (MHD) theory is used to investigate some of the fundamental properties of the geodesic acoustic continuum modes (GAMs) in tokamaks, including their global structure, their associated magnetic components both inside and outside the plasma, and effects of a non-circular cross section of the plasma. In addition to the well-known m=1 side-bands in the perturbed density and pressure of the (electrostatic) GAM, the MHD continuum GAM also includes a m=1 side-band in the perturbed toroidal magnetic field as well as m=2 side-bands in the perturbed density, pressure, poloidal flow and in the magnetic components δ {{B}r} and δ {{B}θ} (m is the poloidal mode number). These m=2 side-bands exist within the whole plasma and the magnetic components also outside the plasma, and the magnitudes of these components in the vacuum region are calculated in the paper. It is shown that, for plasmas with a conducting wall not too far from the plasma surface, the perturbed magnetic field in the vacuum region is dominated by its poloidal component δ {{B}θ} , with poloidal dependence \\sin 2θ , in agreement with experiments. Aspects of the plasma equilibrium that affect the magnitude of the perturbed magnetic field in the vacuum region are discussed in the paper. Furthermore, the influence of a non-circular plasma cross section on the GAM frequency and on the spectrum of the global, perturbed magnetic field is analysed. It is found that the only significant effect of a non-circular cross section on the GAM frequency comes from elongation and its variation across the plasma radius. However, higher-order shaping effects, as well as finite aspect ratio, induce other Fourier components than m=2 in the magnetic halo that surrounds the GAM surface.
ICRF wave propagation and absorption in tokamak and mirror magnetic fields: a full-wave calculation
International Nuclear Information System (INIS)
Global solutions for the ion cyclotron resonant frequency (ICRF) wave fields in a straight tokamak with rotational transform and in a poloidally symmetric mirror are calculated in the cold plasma limit. The component of the wave electric field parallel to B vector is assumed zero. Symmetry in each problem allows Fourier decomposition in one ignorable coordinate, and the remaining set of two coupled, two-dimensional partial differential equations is solved by finite differencing. Energy absorption and antenna impedance are calculated using a simple collisional absorption model. When large gradients in absolute value B along B vector are present in either geometry, ICRF heating at the fundamental ion cyclotron resonance is observed. For the mirror, such gradients are always present. But for the tokamak, the rotational transform must be large enough that B vector . delB greater than or equal to 0(1). For smaller transforms more typical of real tokamaks, only heating at the two-ion hybrid resonance is observed. This suggests that direct resonant absorption at the fundamental ion cyclotron resonance may be possible in stellarators where B vector . delB approx. 0(1) naturally. 13 refs., 23 figs
International Nuclear Information System (INIS)
Suppression of neoclassical tearing modes in tokamaks under anomalous transverse transport conditions when the magnetic well effect predominates over the bootstrap drive is studied. Reduced equations of transfer are used in the description. Geodetic effects are considered during the magnetic well calculation. A criterion for the stabilization of neoclassical tearing modes by the compound effect at an arbitrary level of the transverse heat transport by electrons and ions is derived