Ergodic divertor impact on Tore Supra plasma edge
International Nuclear Information System (INIS)
Grosman, A.; Ghendrih, P.; Agostini, E.; Bruneau, J.L.; Michelis, C. De; Fall, T.; Gil, C.; Guilhem, D.; Hess, W.; Hutter, T.
1990-01-01
Present ergodic divertor experiments in TORE SUPRA have been devoted to benchmarking the operational regimes of the apparatus. Two major effects are reported; on one hand, strong changes occur in the ergodized boundary layer (up to 20% of the minor radius), and on the other hand, the central plasma and especially the confinement is not directly affected, i.e. the observed modifications are induced by edge effects. The basic trends, which are recorded are a decrease of both the edge electronic temperature and the edge density gradient while the radiated power is increased at the very edge of the ergodic region. The latter feature is in agreement with the impurity line emission characterized by an increase of the peripheral lines with a strong decrease of the central lines
Edge plasma control: Particle channeling in Tore Supra pump limiter and ergodic divertor
International Nuclear Information System (INIS)
Ghendrih, P.; Samain, A.; Grosman, A.; Capes, H.; Morera, J.P.
1989-01-01
Improved pumping efficiency can be achieved on Tore Supra by channeling process for particles, i.e. channeling of neutrals in the throat of pump limiters and channeling of plasma towards neutralizer plates in the ergodic divertor. The plugging length for the pump limiter throat is computed and numerical evidence of plasma flux channeling between the conductor bars of the ergodic divertor is presented. The effect of the Tore Supra ergodic divertor on edge plasma state and edge plasma transport is discussed. (orig.)
Progress in ergodic divertor operation on Tore Supra
International Nuclear Information System (INIS)
Ghendrih, Ph.; Becoulet, M.; Colas, L.; Grosman, A.; Guirlet, R.; Gunn, J.; Loarer, T.; Azeroual, A.; Basiuk, V.; Beaumont, B.; Becoulet, A.; Bremond, S.; Bucalossi, J.; Capes, H.; Corre, Y.; Costanzo, L.; Michelis, C. de; Devynck, P.; Feron, S.; Friant, C.; Garbet, X.; Giannella, R.; Grisolia, C.; Hess, W.; Hogan, J.; Ladurelle, L.; Laugier, F.; Martin, G.; Mattioli, M.; Meslin, B.; Monier-Garbet, P.; Moulin, D.; Nguyen, F.; Pascal, J.Y.; Pecquet, A.L.; Pegourie, B.; Reichle, R.; Saint-Laurent, F.; Vallet, J.C.; Zabiego, M.
1999-09-01
Upgrade of the Tore ergodic divertor has led to significant progress in ergodic divertor physics. The disruptive limit governed by the stochastization of the outer magnetic surfaces is found to occur for a value of the Chirikov parameter reaching 2 on the magnetic surface q = 2 + 3 / 12. This experimentally observed robustness allows one to operate at very low safety factor on the separatrix (q ∼ 2). Numerical analysis of ballooning turbulence in a stochastic layer indicates that the decay of the density fluctuations is in associated with an increase of the fluctuating electric drift velocity. The bottom line is then an enhanced cross-field transport in the vicinity of the target plates. This lowering of confinement appears to be compensated by an intrinsic transport barrier on the electron temperature. The 3-D response of the temperature field is computed with a fluid code. The intrinsic transport barrier at the separatrix, reported experimentally, can be recovered together with small amplitude temperature modulations in the divertor volume. Experimental evidence of the 3 density regimes (linear, high recycling and detachment) is reported. The low critical density values for these transitions indicate that similar parallel physics govern the axisymmetric and ergodic divertor, despite the open configuration of the latter. Measurement and understanding of these density regimes provide a means for feedback control of plasma density and an improvement in ICRH coupling scenarios. Experimental data also indicated that particle control with the vented target plates is effective. Increase of impurity control and radiation efficiency are recalled. Global power balance has been analysed. These results confirm the enhanced radiation capacity of the ergodic divertor. (author)
International Nuclear Information System (INIS)
Grosman, A.; Ghendrih, P.; DeMichelis, C.; Monier-Garbet, P.; Vallet, J.C.; Capes, H.; Chatelier, M.; Geraud, A.; Goniche, M.; Grisolia, C.; Guilhem, D.; Harris, G.; Hess, W.; Nguyen, F.; Poutchy, L.; Samain, A.
1992-01-01
The ergodic divertor experiments in TORE SUPRA can be analysed along two main lines. The first one refers to the change of the heat and particle transport in the ergodized zone. This is especially true for the electron heat transport which is enhanced in the edge layer. But other distinctive features give evidence of the importance of the parallel connexion length between the plasma edge and the wall. The field lines, which are stochastic in the major part of the perturbed layer (10-15 cm) are such that, in the outermost layer (3 cm), the connexion topology is regular. This has obvious effects on the particle and power deposition, but also on the plasma parameters, and consequently influences the particle recycling and impurity shielding processes. The TORE SUPRA ergodic divertor experiments are reviewed in this framework
Mechanical design and manufacture of magnetic ergodic divertor for the TORE SUPRA tokamak
International Nuclear Information System (INIS)
Lipa, M.; Aymar, R.; Deschamps, P.; Hertout, P.; Portafaix, C.; Samain, A.
1989-01-01
A configuration of six equally spaced ergodic divertors has been chosen to control the plasma impurities in the TORE SUPRA tokamak since the control of these impurities is essential to the long pulse duration envisioned for the machine. Each of the six indentical modules is composed of (8) conductor bars arranged in a poloidal direction forming a resonant helical winding. The proximity of the conductors to the plasma requires that each copper assembly be water cooled, enclosed in a stainless steel casing and protected by pure graphite tiles attaches to the inner surface of the casing. Particles which drift between the coil bars are neutralized on actively water cooled neutralizer plates and then pumped out by titanium getter pumps which are located on each toroidal end of a divertor modul. (author). 5 refs.; 7 figs.; 1 tab
Experimental study of the topological aspect of the ergodic divertor in Tore-supra tokamak
International Nuclear Information System (INIS)
Costanzo, L.
2001-10-01
The control of power deposition onto plasma facing components in tokamaks is a determining factor for future thermonuclear fusion reactors. Plasma surface interaction can be performed using limiters or divertors. The ergodic divertor installed on Tore Supra is an atypical example of a magnetic divertor. It consists in applying a magnetic perturbation which establishes a particular topology of the plasma in contact with the wall (edge plasma). We carried out dedicated experiments in order to study parallel heat flux which strike the divertor neutralizers. This quantitative and qualitative analysis of heat flux as a function of experimental conditions allows to determine the profiles of power deposition along the neutralizers. The influence of plasma electron density, additional heating, impurities and injected gas was established. An experimental study of the sheath heat transmission factor γ was carried out by correlating measurements made with Langmuir probes and infrared imaging. This study gave rise to a major conclusion: for ohmic discharges with deuterium injection and most of the time with helium, it was experimentally confirmed that γ=7 in agreement with classical sheath theory. However, an increase of this factor with additional power has been shown. Detached plasma, which is an attractive regime in order to reduce the power deposition, requires an optimized control. A new measurement of the detachment onset has been developed. It is based on the variation of heat flux onto the plates derived from infrared measurements. A detachment cartography with the determination of a new 2D 'IR' Degree of Detachment was carried out allowing to locate the zone where the detachment starts. We can apply this concept both to other tokamaks such as JET and ITER. A comparison between the axisymmetric divertor and the ergodic divertor is also presented concerning the power deposition in the two configurations. Low heat flux with the ergodic divertor is a major advantage
Particle exhaust with vented structures: application to the ergodic divertor of Tore Supra
International Nuclear Information System (INIS)
Azeroual, A.
2000-01-01
In a thermonuclear reactor, one must continuously fuel the discharge and extract the ashes resulting from fusion reactions. To avoid the risk of discharge poisoning, α-particle concentration is limited to ∼ 10 %. To allow for steady-state conditions requires then to extract ≥2 % of the helium out flux. In Tore Supra, the ergodic divertor is the main component managing the heat and particle fluxes at the edge. Its principle consists in generating a resonant perturbation able to destroy magnetic surfaces at the plasma periphery. In this region, the field lines are open and connected at both ends to neutralizers which are wetted by the major part of the heat and particle fluxes and are the structures through which a part of the plasma out flux is pumped for maintaining the discharge in steady-state conditions. This work describes the neutral recirculation around the ergodic divertor and is based on a data base of 56 discharges. One discuss the two processes allowing for particle exhaust: the ballistic collection of ions and that of neutrals backscattered by atomic reactions. These two processes are modelled accounting for a realistic description of the divertor geometry. A comparison between simulations and experiments is presented for measurements characterising the three main actors of plasma-wall interaction: the edge plasma, the D α light emission and the neutral pressure in the divertor plenum. Last, one question how such a system can be extrapolated to next step machines, for which one must account for technical constraints linked to the presence of the shield protecting the coils from the high neutron flux. (author)
Energy Technology Data Exchange (ETDEWEB)
Meslin, B
1998-04-30
Plasma density control on the tokamak Tore Supra is important for the optimization of every experimental scenario dealing with the improvement of plasma performances. Specific conditions are required both in the plasma bulk and at the edge. Within the framework of the present study, a magnetic configuration is used in the e plasma edge of Tore Supra: the ergodic divertor configuration. A magnetic perturbation which is resonant with the permanent field destroys the plasma confinement locally, opening the field lines onto the material components. They aim of the study is the characterization of the edge density in every relevant scenario for Tore Supra. The first part of this work is dedicated to density and temperature measurements by a series of fixed Langmuir probes located at the very edge of the plasma. Thanks to them, density regimes have been put in evidence during experiments where the volume averaged density
Energy Technology Data Exchange (ETDEWEB)
Costanzo, L
2001-10-01
The control of power deposition onto plasma facing components in tokamaks is a determining factor for future thermonuclear fusion reactors. Plasma surface interaction can be performed using limiters or divertors. The ergodic divertor installed on Tore Supra is an atypical example of a magnetic divertor. It consists in applying a magnetic perturbation which establishes a particular topology of the plasma in contact with the wall (edge plasma). We carried out dedicated experiments in order to study parallel heat flux which strike the divertor neutralizers. This quantitative and qualitative analysis of heat flux as a function of experimental conditions allows to determine the profiles of power deposition along the neutralizers. The influence of plasma electron density, additional heating, impurities and injected gas was established. An experimental study of the sheath heat transmission factor {gamma} was carried out by correlating measurements made with Langmuir probes and infrared imaging. This study gave rise to a major conclusion: for ohmic discharges with deuterium injection and most of the time with helium, it was experimentally confirmed that {gamma}=7 in agreement with classical sheath theory. However, an increase of this factor with additional power has been shown. Detached plasma, which is an attractive regime in order to reduce the power deposition, requires an optimized control. A new measurement of the detachment onset has been developed. It is based on the variation of heat flux onto the plates derived from infrared measurements. A detachment cartography with the determination of a new 2D 'IR' Degree of Detachment was carried out allowing to locate the zone where the detachment starts. We can apply this concept both to other tokamaks such as JET and ITER. A comparison between the axisymmetric divertor and the ergodic divertor is also presented concerning the power deposition in the two configurations. Low heat flux with the ergodic divertor is a
International Nuclear Information System (INIS)
Zabiego, M.; Friant, C.; Ghendrih, P.; Becoulet, M.; Bucalossi, J.; Saint-Laurent, F.
1999-01-01
Although ergodic divertors are primarily designed to control particle and heat fluxes at the plasma edge, they also happen to affect the MHD stability of tokamak discharges. On Tore Supra, the ergodic divertor has long been known to stabilize the m/n=2/1 tearing mode induced, for instance, by edge radiation and detachment processes, thus allowing safe high-current and high-density operations. More recently, though, in discharges where ergodic divertor operations were optimised relative to the control of the edge-plasma (i.e., with large divertor perturbation), a detrimental increase in the disruptiveness has been observed. The action that the ergodic divertor has on the MHD activity is interpreted in terms of a redistribution of the current profile. The latter results from a large increase in the edge resistivity, primarily induced by the degradation of the electron energy confinement in the ergodic layer. The possibility that a transport barrier develops in the vicinity of the separatrix strongly affects the considered modelling. (authors)
Tore Supra: technical description
International Nuclear Information System (INIS)
1985-08-01
This report is aimed, after a brief recall of physics and technologic perspectives of Tore Supra, at giving a detailed description of the basic machine; details of each component are defined. Volume 1 is specifically concerned with the general aspects of Tore Supra and the toroidal field system [fr
International Nuclear Information System (INIS)
Corre, Y.
2001-11-01
In a Tokamak thermonuclear reactor, the impurity control is essential to keep the plasma in fusion conditions. Indeed, the impurities which enter the bulk are responsible for the fuel dilution (and hence a significant reduction of the number of fusion reactions). The pollution of fusion plasma by impurities has thus to be as low as possible. In the Tokamak Tore Supra, as in most present day Tokamaks, the main impurity is carbon. First, we have studied the carbon production mechanisms on the Neutralizer Plates of the Tore Supra Ergodic Divertor (where the plasma surface interaction is the most important). For this purpose we have used an endoscope during an experimental campaign in order to measure spectral line brightnesses emitted in the visible wavelength range by low charge carbon ions. The quantitative analysis of the pictures provided by this endoscope, together with measurements by other plasma edge diagnostics, has allowed us to estimate the atom flux extracted from the neutralizer plates during the various density regimes accessed in ED configuration. We have deduced from these calculations an experimental sputtering yield. A comparison with the theoretical sputtering yield allows us to determine the dominant erosion mechanism as a function of the edge plasma density and temperature. This comparative analysis shows that when the edge electron temperature is above 30 eV, the self-sputtering process is the dominant phenomenon for impurity production and bulk contamination. When T e bord is high, the effective erosion is bigger than the erosion due to deuterium ion impacts. This information has then been used to study transport and radiation of this impurity near the neutralizer plates with the 3-D Monte Carlo code BBQ (grill) and other carbon radiation measurements. It has allowed us to characterise the circulation of carbon in the plasma edge and to determine the carbon fraction which enters the confined plasma and the fraction which is rapidly driven back
Tore Supra: technical description
International Nuclear Information System (INIS)
1985-08-01
Cryogenic system of Tore Supra is described with its principal functions and operation modes. Data control and acquisition with on line data processing is presented. Radiation dose and induced radioactivity evaluation is studied. Cooling system is detailed together with characteristics of facilities and circuits to cool. Then machine assembly and buildings are presented [fr
Ciel, a new breath for Tore Supra
International Nuclear Information System (INIS)
Garin, P.
1998-01-01
In view of preparing next generation of tokamaks, a new goal has been given to Tore Supra, initially designed for 30 second operation. In order to fulfill this target, with the ultimate aim of injecting in the plasma 25 MW for 1000 s shots: all existing components (including the 6 ergodic divertor modules) present inside the inner vessel of Tore Supra will be removed by the end of 1999, they will be replaced in 2000 by a set of up to date technology components, designed to withstand an overall power of 25 MW for shots up to 1000 s constituting the so-called 'CIEL' project (French acronym for 'Composants Internes Et Limiteur'). It is planned to stop present Tore Supra's operation in autumn 1999, and start again with CIEL environment at the end of 2000. Full capacity (pumping and cooling) will be available in 2002. (author)
Plasma Edge Control in Tore Supra
International Nuclear Information System (INIS)
Evans, T.E.; Mioduszewski, P.K.; Foster, C.; Haste, G.; Horton, L.; Grosman, A.; Ghendrih, P.; Chatelier, M.; Capes, H.; Michelis, C. De; Fall, T.; Geraud, A.; Grisolia, C.; Guilhem, D.; Hutter, T.
1990-01-01
TORE SUPRA is a large superconducting tokamak designed for sustaining long inductive pulses (t∼ 30 s). In particular, all the first wall components have been designed for steady-state heat and particle exhaust, particle injection, and additional heating. In addition to these technological assets, a strict control of the plasma-wall interactions is required. This has been done at low power: experiments with ohmic heating have been mainly devoted to the pump limiter, ergodic divertor and pellet injection experiments. Some specific problems arising in large tokamaks are encountered; the pump limiter and the ergodic divertor yield the expected effects on the plasma edge. The effects on the bulk are discussed
Particles pumping in Tore Supra
International Nuclear Information System (INIS)
Bonnel, P.; Chappuis, P.; Lipa, M.
1989-01-01
TORE SUPRA and its peripheral equipments are provided with routine clean high vacuum by turbomolecular pumping. During plasma discharges large quantity of very hot gases activating at plasma edge and plasma density in scrape off layer has to be controlled before they strike violently solid wall provoking increase in impurities content and make density up to disruptive level. A Magnetic Ergodic Divertor made of six winding structures - MED - six Vertical Pumped Limiters - VPL - and one Horizontal Pumped Limiter - HPL - are set in the vacuum chamber in order to cope with plasma-wall interactions and neutral gas recycling. Each apparatus is equipped at front side with thermal shield respectively made of polycristallin and pyrolitic graphite bolted on stainless steel support for MED and HPL whereas for VPL it is made of CFC Aerolor 05 brazed on hardened copper. The total heat removal capacity of these plasma facing components is 12 MW. Design of particles collection openings and ducts conductance allow 10% of capture efficiency, that means for TORE SUPRA a flux of 3 x 10 21 particles/second has to be sorbed by water cooled titanium getter pumps, settled at rear side. All those facilities were put into plasma operation at the beginning of 1989 for a short time. Preliminary observations go along with theoretical predictions, that actions in scrappe-off layer may provoke effects in bulk plasma. Very first results drawn out, show that particle collection and heat removal were effective by MED, VPL and HPL and that plasma behaviour was not disturbed by their presence and actions but instead tendency to improvement was observed
International Nuclear Information System (INIS)
Cristofani, P.; Desgranges, C.; Garbet, X.; Geraud, A.; Gil, C.; Hoang, G.T.; Joffrin, E.; Pecquet, A.L.
1995-01-01
Snakes have been achieved after pellet injection in Tore Supra during ohmic as well as ICRH discharges as it has already been observed in other machines. On Tore Supra, high speed H 2 pellets were injected into D 2 plasmas under the specified experimental conditions, the matter is deposited in the centre and snakes are produced in 50% of the cases, but they are created on a second much more internal q=1 surface leading probably to a non monotonic current profile. The properties of the snake, induced current modification and the important role of the bootstrap current in the snake formation are described. (K.A.) 5 refs.; 7 figs
Tore supra first wall conditioning
International Nuclear Information System (INIS)
Gauthier, E.; Achard, M.H.; Grosman, A.; Monier, P.
1989-01-01
The procedures and the results obtained concerning impurity and isotopic control in Tore Supra tokamak are summarized. The conditioning of the vessel, mainly achieved by glow discharges, is described. The impurity control of the discharge was monitored with a VUV-X spectrometer. The in situ blasting degassing procedure applied is explained. In the sequence of the conditioning process, the hydrogen and the helium glow discharges and the carbonization method are discussed. The He glow discharges allowed to limit the H content of the He plasma shot below 20%
Disruption mitigation on Tore Supra
International Nuclear Information System (INIS)
Martin, G.; Sourd, F.; Saint-Laurent, F.; Bucalossi, J.; Eriksson, L.G.
2004-01-01
During disruptions, the plasma energy is lost on the first wall within 1 ms, forces up to hundred tons are applied to the structures and kA of electrons are accelerated up to 50 MeV (runaway electrons). Already sources of concern in present day tokamaks, extrapolation to ITER shows the necessity of mitigation procedures, to avoid serious damages to in-vessel components. Massive gas injection was proposed, and encouraging tests have been done on Textor and DIII-D. Similar experiments where performed on Tore Supra, with the goal to validate their effect on runaway electrons, observed during the majority of disruptions. 0.1 mole of helium was injected within 5 ms in ohmic plasmas, up to 1.2 MA, either stable, or in a pre-disruptive phase (argon puffing). Beneficial effects where obtained: reduction of the current fall rate and eddy currents, total disappearance of runaway electrons and easy recovery for the next pulse, without noticeable helium pollution of following plasmas. Analysis of the 4 ms period between injection and disruption indicates that to reach these goals, one need to inject enough helium to keep it only partially ionised. It corresponds to 0.1 g for Tore Supra, and extrapolate to hundreds of grams for ITER. (authors)
Disruption mitigation on Tore Supra
International Nuclear Information System (INIS)
Martin, G.; Sourd, F.; Saint-Laurent, F.; Bucalossi, J.; Eriksson, L.G.
2005-01-01
During disruptions, the plasma energy is lost on the first wall within 1 ms, forces up to hundred tons are applied to the structures and kA of electrons are accelerated up to 50 MeV (runaway electrons). Already sources of concern in present day tokamaks, extrapolation to ITER shows the necessity of mitigation procedures, to avoid serious damages to in-vessel components. Massive gas injection was proposed, and encouraging tests have been done on Textor and DIII-D. Similar experiments where performed on Tore Supra, with the goal to validate their effect on runaway electrons, observed during the majority of disruptions. 0.1 mole of helium was injected within 5 ms in ohmic plasmas, up to 1.2 MA, either stable, or in a pre-disruptive phase (argon puffing). Beneficial effects where obtained: reduction of the current fall rate and eddy currents, total disappearance of runaway electrons and easy recovery for the next pulse, without noticeable helium pollution of following plasmas. Analysis of the 4 ms period between injection and disruption indicates that to reach these goals, one need to inject enough helium to keep it only partially ionised. It correspond to 0.1 g for Tore Supra, and extrapolate to hundred's of grams for ITER. (author)
Particle control studies on Tore Supra
International Nuclear Information System (INIS)
Mioduszewski, P.
1987-01-01
The report consists of viewgraphs. The goal of the particle control program at Tore Supra is to study plasma performance with strong pellet fueling and corresponding particle exhaust in a limiter tokamak
Pellet injection requirements for TORE SUPRA
International Nuclear Information System (INIS)
Lafferranderie, J.
1986-01-01
The main parameters of TORE SUPRA are outlined and pellet injection requirements to meet plasma density goals are discussed. Topics considered include plasma buildup, plasma refueling and penetration depth
Edge plasma diagnostics on Tore Supra tokamak
International Nuclear Information System (INIS)
Fujita, Junji
1991-01-01
From 1988 to 1991, the international scientific research 'Diagnosis of peripheral plasma in Tore Supra tokamak' was carried out as a three-year plan receiving the support of the scientific research expense of the Ministry of Education. This is to apply the method of measuring electron density distribution by neutral lithium beam probe spectroscopy to the measurement of the electron density distribution in the peripheral plasma in Tore Supra Tokamak in France. Among many tokamaks in operation doing respective characteristics researches, the Tore Supra generates the toroidal magnetic field by using superconducting coils, and aims at the long time discharge for 30 sec. for the time being, and for 300 sec. in future. In the plasma generators for long time discharge like this, the technology of particle control is a large problem. For this purpose, a divertor was added to the Tore Supra. In order to advance the research on particle control, it is necessary to examine the behavior of plasma in the peripheral part in detail. The measurement of peripheral plasma in tokamaks, beam probe spectroscopy, the Tore Supra tokamak, the progress of the joint research, the problems in the joint research and the perspective of hereafter are reported. (K.I.)
Nuclear fusion TORE SUPRA, a new stage
International Nuclear Information System (INIS)
Gregoire, M.; Laurent, L.
1995-01-01
Since almost forty years, the scientists try and neutralize in a pacific aim thermonuclear fusion energy and therefore they use the magnetic confinement of hot plasmas.In France, since 1960 the achieved studies permitted in 1988 to bring into service the TORE SUPRA TOKAMAK, which used, for the first time a superconducting magnet to generate the confinement magnetic field. TORE SUPRA, which didn't still explore its maximal potentialities, will be one of the apparatuses which will be used as basis of the international project ITER development. 5 figs
Remote experiment participation on Tore-Supra
International Nuclear Information System (INIS)
Theis, J.-M.; Larsen, J.-M.
2004-01-01
The DRFC has traditionally had a very large external collaboration involvement. In particular, 15% of the DRFC work is directed towards the JET programme. As a consequence substantial telecommunications facilities have been installed [F.E.D. 60/3 (2002) 449; F.E.D. 60/3 (2002) 459]. A specific station for remote communication has been set up in the Tore-Supra control room, closely coupled to a collaborating team at INRS Que., Canada. This paper describes our pilot experience with the Canadian participation, which gives details of the communication and data sharing tools used to fully work on Tore-Supra
TORE SUPRA: programme of development, qualifying tests
International Nuclear Information System (INIS)
Aymar, R.; Bareyt, B.; Bon Mardion, G.
1982-02-01
TORE SUPRA is a Tokamak under construction in France. It is designed as a useful complement to JET. In this paper, we review the development work and test programme, and summarize its main objectives and conclusions. This concerns first the more conventional parts of the Tokamak (vacuum vessel technology and high power circuit breaker for the poloidal field system) followed by a large amount of work about the superconducting coils
Electron cyclotron emission measurement in Tore Supra
International Nuclear Information System (INIS)
Javon, C.
1991-06-01
Electron cyclotron radiation from Tore-Supra is measured with Michelson and Fabry-Perot interferometers. Calibration methods, essential for this diagnostic, are developed allowing the determination of electron temperature in the plasma. In particular the feasibility of Fabry-Perot interferometer calibration by an original method is demonstrated. A simulation code is developed for modelling non-thermal electron population in these discharges using measurements in non-inductive current generation regime [fr
Global analysis of ICRF wave coupling on Tore Supra
International Nuclear Information System (INIS)
Goniche, M.; Bremond, S.; Colas, L.
2003-01-01
The Tore Supra tokamak is equipped with a multi-megawatt ion cyclotron range of frequency (ICRF) system for heating and current drive. The coupling of the fast wave to the plasma, characterized by the distributed coupling resistance along the radiating straps, is a crucial issue in order to launch large RF powers. Many factors can have an effect on ICRF wave coupling. Quantitative prediction from theoretical modelling requires the knowledge of the local inhomogeneous plasma density profile in front of the antenna for running sophisticated antenna codes. In this work, we have rather followed a 'global' approach, based on Tore Supra experimental results, for the parametric study of the coupling resistance. From a large data base covering seven experimental campaigns (∼2250 shots), a scaling law of the coupling resistance including the main parameters of the plasma and of the antenna configuration is established. This approach is found to be reliable for the analysis of coupling in the different scenarios: He/D 2 gas filling, gas/pellets for plasma fuelling, plasma leaning on inner wall/low field side limiter, limiter/ergodic divertor configuration, minority heating/direct electron heating. From one scenario to another, a significant variation of the coefficients of the scaling law is found. The study of these variations allows to get some insight on the main physical mechanisms which influence the ICRF wave coupling in a tokamak operation, such as the wall conditioning and recycling conditions, RF sheaths or frequency. (author)
International Nuclear Information System (INIS)
Moreau, D.
1995-01-01
Recent results regarding heating, confinement, current drive and profile modifications, heat and particle exhaust are reported. Improved core confinement is obtained after pellet injection (PEP) or Lower Hybrid current drive (LHEP) and may be linked with small - or reversed - central magnetic shear. Conversely, by increasing the magnetic shear in the gradient region, both LHCD and fast wave electron heating (FWEH) have produced improved global confinement was carried by the bootstrap current. Fast wave current drive has been observed at the level of 80 kA in a 0.4 MA discharge. In the ergodic divertor configuration, stable radiative layers were obtained with neon injection. At least 80% of a total of 7 MW injected power were radiated without confinement degradation or impurity accumulation. Finally, the heat exhaust capability of the various actively cooled plasma facing components is briefly described. (author) 14 refs.; 13 figs
The acquisition system for Tore Supra 1000 s discharges
International Nuclear Information System (INIS)
Guillerminet, B.; How, J.
2000-01-01
Long duration discharges are planned for Tore Supra in the near future. A study has been made to detect and correct all the possible limitations of the data acquisition system. Results and analysis of a few 1000 s 'dry-run' test pulses are presented in this paper as well as the solutions foreseen for Tore Supra
The TORE SUPRA fast reciprocating RF probe
International Nuclear Information System (INIS)
Thomas, C.E. Jr.; Harris, J.H.; Haste, G.R.
1994-01-01
A fast reciprocating ICRF (Ion Cyclotron Range of Frequencies) probe was installed and operated on TORE SUPRA during 1992/1993. The body of the probe was originally used on the ATF experiment at ORNL. The probe was adapted for use on TORE SUPRA, and mounted on one of the two fast reciprocating probe mounts. The probe consists of two orthogonal single-turn wire loops, mounted so that one loop senses toroidal RF magnetic fields and the other senses poloidal RF magnetic fields. The probe began operation in June, 1993. The probe active area is approximately 5 cm long by 2 cm, and the reciprocating mount has a slow stroke (5 cm/sec) of 30 cm by 2 cm, and the reciprocating mount has a slow stroke (5 cm/sec) of 30 cm and a fast stroke (1.5 m/sec) of about 10 cm. The probe was operated at distances from the plasma edge ranging from 30 cm to -5 cm (i.e., inside the last closed flux surface). The probe design, electronics, calibration, data acquisition and data processing are discussed. First data from the probe are presented as a function of ICRF power, distance from the plasma, loop orientation, and other plasma parameters. Initial data shows parametric instabilities do not play an important role for ICRF in the TORE SUPRA edge and scrape-off-layer (SOL) plasmas. Additionally it is observed that the probe signal has little or no dependence on position in the SOL/plasma edge
Microwave transmission measurements in Tore Supra
International Nuclear Information System (INIS)
Segui, J.L.; Giruzzi, G.
1991-01-01
A microwave transmission diagnostic system below the electron gyrofrequency is now operating on Tore-Supra. In low density Lower-Hybrid current drive discharges the refraction effects are weak and the measurement of the wave transmission coefficient provides an estimate of the non inductive current. For higher densities, the signal is modulated by refraction effects related to sawteeth and MHD modes. In this case, more elaborated computational techniques are required in order to isolate the absorption effect from the apparent wave attenuation due to refraction. Conversely, at frequencies low enough to avoid cyclotron absorption, microwave transmission can be used as a diagnostic of sawteeth and MHD activity
Ripple losses during ICRF heating in Tore Supra
International Nuclear Information System (INIS)
Basiuk, V.; Eriksson, L.-G.; Bergeaud, V.; Chantant, M.; Martin, G.; Nguyen, F.; Reichle, R.; Vallet, J.C.; Delpeche, L.; Surle, F.
2004-01-01
The toroidal field coils in Tore Supra are supra-conducting, and their number is restricted to 18. As a result, the ripple is fairly large, about 7% at the plasma boundary. Tore Supra has consequently been equipped with dedicated ripple loss diagnostics, which has allowed ripple loss studies. This paper reports on the measurements made with these diagnostics and provides an analysis of the experimental results, comparing them with theoretical expectations whenever possible. Furthermore, the main heating source accelerating ions in Tore Supra is ion cyclotron resonance range of frequency (ICRF) heating, and the paper provides new information on the ripple losses of ICRF accelerated ions. (author)
MHD stability and mode locking in pre-disruptive plasmas on TORE SUPRA
International Nuclear Information System (INIS)
Vallet, J.C.; Edery, D.; Joffrin, E.; Lecoustey, P.; Mohamed-Benkadda, M.S.; Pecquet, A.L.; Samain, A.; Talvard, M.
1991-01-01
Experiments devoted to the study of MHD activity have been carried out on TORE SUPRA. The observed disruptions are preceded by the growth of an m=2 N=1 rotating mode which locks when the magnetic field perturbation exceeds a critical value. The mode locking is interpreted as a bifurcation of the mode frequency. In addition, stabilization of the m=2 N=1 tearing mode has been obtained with the Ergodic Divertor (ED)
Power deposition to the facing components in Tore-Supra
International Nuclear Information System (INIS)
Guilhem, D.; Chatelier, M.; Chappuis, P.; Koski, J.; Watkins, J.
1990-01-01
The modifications of the power scrape-off length, λ q and power deposition are studied for various configurations in ohmic Tore-Supra plasmas. The plasma is either touching the horizontal limiter alone, the full set of six pump limiters or the inner bumper limiter. All configurations are with and without the ergodic divertor system energized. From a comparison of the infrared images of the limiter we derived that the λ q for power deposition was slightly less than 9±1 mm in ohmic plasmas which is in agreement with the predicted design value of 10 mm. Using the six limiters, instead of one, does not modify λ q significantly, but leads to small asymmetries. The power is shared by all the limiters and the maximum surface temperature on the horizontal limiter decreases. These λ q values have been independently determined by calorimetric measurements on the integrated energy deposition on the horizontal limiter and other internal structures 5 cm into the scrape-off layer. These values agree with the infrared measurements in the two cases. In the presence of the ergodic divertor we observe a broadening of the scrape-off layer, the e-folding length for power deposition reaching 2.5 cm. Large asymmetries in the power deposition can be seen on the front face of the limiter, leading to the formation of hot spots at the leading edges. (orig.)
Runaway electrons dynamics and confinement in Tore-Supra
International Nuclear Information System (INIS)
Chatelier, M.; Geraud, A.; Joyer, P.; Martin, G.; Rax, J.M.
1989-01-01
The lack of energy of runaway electrons, confined in Tore Supra tokamak, is studied. Ohmic discharges, obtained with helium gas, exhibit a small amount of runaway electrons on both hard X-ray monitors and neutron sensors. The observations show an important lack of energy for runaway electrons confined in Tore Supra. It is assumed to be dued to a small pitch-angle scattering (a few degrees), and many candidates for this are compared: the strongest known one collisions seems not to be enough by an order of magnitude. Density and magnetic scans on Tore Supra are needed to discriminate between enhanced collisional scattering processes and purely magnetic phenomena
International Nuclear Information System (INIS)
Fumelli, M.; Jequier, F.; Bottiglioni, F.
1986-01-01
The Tore-Supra neutral beam injectors required an ion source with an extraction area of 113 x 6.6 cm 2 . 40 A in deuterium must be available during up to 30 s. Fitted to these requirements, a plasma source with a multipolar magnetic configuration has been constructed and operated at FAR, firstly in H 2 , on a test stand and then, in D 2 , on the prototype injector. The nominal ion current density of 150 mA/cm 2 has been achieved with a uniformity better than 10%, in pulses of 1 s. Two discharge regimes, depending on different magnetic topologies, have been studied with regard to the discharge efficiency, deuterons yield and plasma uniformity. Proton contents up to 85% at 100 mA/cm 2 have been measured. (author)
International Nuclear Information System (INIS)
Fumelli, M.; Jequier, F.; Bottiglioni, F.
1987-01-01
The Tore-Supra neutral beam injectors require an ion source with an extraction area of 113 x 6.6 cm 2 . 40 A in deuterium must be available during up to 30 s. Fitted to these requirements, a plasma source with a multipolar magnetic configuration has been constructed and operated at FAR, firstly in H 2 , on a test strand and then, in D 2 , on the prototype injector. The nominal ion current density of 150 mAcm 2 has been achieved with a uniformity better than 10%, in pulses of 1 s. Two discharge regimes, depending on different magnetic topologies, have been studied with regard to the discharge efficiency, deuterons yield and plasma uniformity. Proton contents up to 85% at 100 mAcm 2 have been measured
First ECRH modulation experiments in Tore Supra
International Nuclear Information System (INIS)
Zou, X.L.; Artaud, J. F.; Bouquey, F.; Clary, J.; Darbos, C.; Giruzzi, G.; Lennholm, M.; Magne, R.; Segui, J.L.
2003-01-01
The modulation of Electron Cyclotron Resonance Heating (ECRH) is a powerful tool to investigate the crucial problem of heat transport in tokamaks. This method consists in producing perturbations in the electron temperature by means of highly localised electron heating. By studying the propagation of the heat pulse associated with such perturbations, it is possible to determine both the heat transport coefficient and, as a by-product, the ECRH power deposition. In this work, three methods have been used for electron transport analysis: i) the well-known FFT method; ii) an analytical method, consisting in the simulation of the temperature modulation by an analytical solution of the heat transport equation in cylindrical geometry; iii) the power balance method with the profile analysis. The three methods are applied to the analysis of recent experiments performed on Tore Supra, and their advantages and drawbacks are discussed. (authors)
Pellet fuelling in Tore Supra long discharges
Géraud, A.; Bucalossi, J.; Loarer, T.; Pégourié, B.; Grisolia, C.; Gros, G.; Gunn, J.
2005-03-01
A new pellet injector, able to inject continuously hydrogen or deuterium pellets, was installed on Tore Supra in 2003 and preliminary experiments aiming to fuel long discharges were performed. In combination with Lower Hybrid (LH) Current Drive, pure pellet fuelled discharges lasting up to 2 min were achieved. The LH power was switched off just before each pellet injection (LH notching) to maintain a relatively deep pellet penetration by reducing the energy of the super-thermal electrons driven by the LH wave. A comparison, based on a particle balance study, between two comparable pellet fuelled and gas fuelled discharges has been done. In the two cases, the volume average density is the same and the analysis shows that the particle source, the pumped flux and the wall retention are similar and appear to be independent of the fuelling method for the low plasma current and density conditions considered ( Ip = 0.6 MA, = 1.5 × 10 19 m -3).
Water leak localization and recovery in Tore Supra
International Nuclear Information System (INIS)
Martinez, A.; Samaille, F.; Chantant, M.; Hatchressian, J.C.
2007-01-01
For almost 20 years at Tore Supra, plasma facing components (PFCs) are actively cooled by a pressurized water primary loop. Tore Supra can be considered as ITER relevant on this particular aspect. During plasma operation, it happened, that unexpected localized power deposits damaged a PFC leading to more or less large water leaks in the vacuum vessel. The improvement of the procedure to localize the leaky circuits, the investigation of technical solutions for minimizing the amount of water from steam condensation in the vacuum vessel and the optimisation of the quality of the draining and the drying of Tore Supra cooling loop circuits are the result of the experience gained during several years by the analysis of the water leak from plasma facing components (PFCs) and their consequences. Different new specific systems designed and installed during this year to fulfil these objectives are described in this paper
New developments on Tore Supra data acquisition units
International Nuclear Information System (INIS)
Leroux, F.; Caulier, G.; Ducobu, L.; Goniche, M.; Antar, G.
2012-01-01
The Tore Supra data acquisition system (DAS) was designed in the early eighties and has considerably evolved since then. Three generations of data acquisition units still coexist. As cost and maintenance of different operating systems is expensive, it was decided to explore an alternative solution based on an open source operating system (OS) with a disk-less system for the fourth generation. In 2010, Linux distributions for VME bus and PCI bus systems have been evaluated and compared to Lynx OS TM real time OS. The results obtained allowed to choose a version of Linux for VME and PC platform for DAS on Tore Supra. In 2011, the Tore Supra DAS dedicated software was ported on a Linux disk-less PCI platform. The new generation was successfully tested during real plasma experiments on one diagnostic, called DCEDRE. (authors)
Control and monitoring of the Tore Supra toroidal superconducting coils
International Nuclear Information System (INIS)
Prou, M.
1989-07-01
Light nuclei controlled fusion reactions are seen as a possible way to produce nuclear energy. For this reason, the interest in hot plasma researches in tokamaks has increased. The Tore Supra main characteristic is related to the superconducting magnet coils. They allow a suitable energy balance, however, they require an accurate and preventive fault detection. The Tore Supra machine and the different methods to detect a transition (from superconducting to normal mode) in the toroidal coils are described. The voltage of the coils, the pressure of the helium superfluid at 1.8 K and the electric current in the circuit parallel resistances, are measured. A computer aided control system allows the toroidal field monitoring (current in the coils, fault detection). The superconducting magnet configuration chosen for Tore Supra seems to be suitable for future large Tokamak devices [fr
Ion temperature profiles along a hydrogen diagnostic beam in a TORE SUPRA tokamak plasma
International Nuclear Information System (INIS)
Romannikov, A.; Petrov, Yu.; Platts, P.; Khess, V.; Khutter, T.; Farzhon, Zh.; Moro, F.
2002-01-01
By means of corpuscular diagnostics one studies temperature of ions along a diagnostic hydrogen beam. Paper presents comparison of temperature of plasma (deuterium) basic ions measures by means of the active corpuscular diagnostics with temperature of C + carbon ions along a beam. One studies behavior peculiarities of T i ion temperature profiles for TORE-SUPRA different modes, such as: formation of plane and even hollow T i profiles for ohmic modes, variation of T i profiles under operation of an ergodic diverter, difference of temperature of basic ions measured by means of the active corpuscular diagnostics from C +5 temperature. Paper offers clear explanation of these peculiarities [ru
Ohmic discharges in Tore Supra - Marfes and detached plasmas
International Nuclear Information System (INIS)
Vallet, J.C.
1990-01-01
The Tore Supra plasma characteristics are given. The observed discharges are either leaning on the graphite inner first wall or limited by movable pump limiters located outboard and at the bottom of the vacuum chamber. The particular plasma conditions which lead to marfes and detached plasmas in ohmically heated He and D2 discharges limited by the inner wall are investigated. The results show that the ratio of radiated power to ohmic power increase linearly with M.g. As M.g rises, attached plasma, marfe and detached plasma are sequentially observed. Detached plasma with an effective radius as small as. 7 times the limiter radius was observed on Tore Supra
Heat Loads On Tore Supra ICRF Launchers Plasma Facing Components
International Nuclear Information System (INIS)
Bremond, S.; Colas, L.; Chantant, M.; Beaumont, B.; Ekedahl, A.; Goniche, M.; Moreau, P.; Mitteau, R.
2005-01-01
Understanding the heat loads on Ion Cyclotron Range of Frequency launchers plasma facing components is a crucial task both for operating present tokamaks and for designing ITER ICRF launchers as these loads may limit the RF power coupling capability. Tore Supra facility is particularly well suited to take this issue. Parametric studies have been performed which enables to get an overall detailed picture of the different heat loads on several areas, pointing to different mechanisms at the origin of the heat power fluxes. Lessons are drawned both with regards to Tore Supra possible operational limits and to ITER ICRF launcher design
Self consistent description of plasma equilibrium evolution in Tore Supra
International Nuclear Information System (INIS)
Blum, J.; Le Foll, J.; Leloup, C.
1984-01-01
A model is presented which describes in a self-consistent way the evolution of the plasma equilibrium in a Tokamak. Numerical simulations are presented for ohmic heating discharges, neutral beam injection, lower hybrid electron heating and current drive in Tore Supra. The various control systems (plasma current, shape and position, coil current sharing) are tested with the code. (author)
Simulation of core turbulence measurement in Tore Supra ohmic regimes
Hacquin, S.; Citrin, J.; Arnichand, H.; Sabot, R.; Bourdelle, C.; Garbet, X.; Kramer-Flecken, A.; Tore Supra team,
2016-01-01
This paper reports on a simulation of reflectometry measurement in Tore Supra ohmic discharges, for which the experimental observations as well as gyrokinetic non-linear computations predict a modification of turbulence spectrum between the linear (LOC) and the saturated ohmic confinement (SOC)
Runaway electrons dynamics and confinement in TORE-SUPRA
International Nuclear Information System (INIS)
Chatelier, M.; Geraud, A.; Joyer, P.; Martin, G.; Rax, J.M.
1989-01-01
Ohmic discharges in TORE-SUPRA are sufficiently long (∼ 6 s) for runaway electrons (R.E.) to reach a steady energy state: their energy limit is determined by the balance between parallel electric field acceleration (20 MeV/V.s in TORE-SUPRA) and radiation losses due to the curvature of the trajectories. When R.E. energy is supposed to be only parallel, this provides estimate of order of 70 MeV (value usually called 'synchrotron limit') reached in less than 2 seconds. Experimental observations on TORE-SUPRA of photoneutron emission together with residual induced radioactivity in the first wall components tend to prove that the actual value is much lower than 70 MeV (i.e. 15-35 MeV). Earlier observations in ORMAK, PLT and TFR already showed R.E. energy a slightly less than expected from standard loop voltage acceleration calculations. Explanations given for this lack of energy (as skin-effect lowering the electric field during the ramp-up phase or balance between continuous creation and losses) seems not to hold on TORE-SUPRA and therefore another mechanism must be considered to explain the R.E. energy limitation. 4 refs., 2 figs
Heat loads on Tore Supra ICRF Launchers Plasma Facing Components
International Nuclear Information System (INIS)
Bremond, S.; Colas, L.; Beaumont, B.; Chantant, M.; Goniche, M.; Mitteau, R.
2005-01-01
Understanding the heat loads on Ion Cyclotron Range of Frequency (ICRF) launchers plasma-facing components is a crucial task both for operating present tokamaks and for designing ITER ICRF launchers as these loads may limit the RF power coupling capability. Tore Supra facility is particularly well suited to take this issue. Parametric studies have been performed which enables to get an overall detailed picture of the different heat loads on several areas, pointing to different mechanisms at the origin of the heat power fluxes. It is found that the most critical items for Tore-Supra operation are localized heat loads on the Faraday screen top left corner and vertical edges. Warming up close to maximum temperature limit originally set for protection of the plasma-facing components is found of high power pulses, but no erosion was observed after detailed inspection of the launcher in Tore-Supra vessel. Yet, the associated heat loads could be limiting for Tore-Supra operation in the future, and some dedicated work is under progress to improve the understanding of these power fluxes, pointing out the importance of getting a better knowledge of particle flows in the scrape of layer
Lower hybrid current drive in Tore Supra and JET
International Nuclear Information System (INIS)
Moreau, D.; Gormezano, C.
1991-01-01
Recent Lower Hybrid Current Drive (LHCD) experiments in TORE SUPRA and JET are reported. Large multijunction launchers have allowed the coupling of 5MW to the plasma for several seconds with a maximum of 3.8 kW/cm 2 . Measurements of the scattering matrices of the antennae show good agreement with theory. The current drive efficiency in TORE SUPRA is about 0.2 x 10 20 Am -2 /W with LH power alone and reaches 0.4 x 10 20 Am -2 /W in JET thanks to a high volume-averaged electron temperature (1.9 keV) and also to a synergy between Lower Hybrid and Fast Magnetosonic Waves. At n e = 1.5 x 10 19 m -3 in TORE SUPRA, sawteeth are suppressed and m = 1MHD oscillations the frequency of which clearly depends on the amount of LH power are observed on soft X-rays, and also on non-thermal ECE. In Jet ICRH produced sawtooth free periods are extended by the application of LHCD and current profile broadening has been clearly observed consistent with off-axis fast electron populations. LH power modulation experiments performed in TORE SUPRA at n e = 4 x 10 19 m -3 show a delayed central electron heating despite the off-axis creation of suprathermal electrons, thus ruling out the possibility of a direct heating through central wave absorption. A possible explanation in terms of anomalous fast electron transport and classical slowing down would yield a diffusion coefficient of the order of 10 m 2 /s for the fast electrons. Finally, successful pellet fuelling of a partially LH driven plasma was obtained in TORE SUPRA, 28 successive pellets allowing the density to rise to n e = 4 x 10 19 m -3 . This could be achieved by switching the LH power off for 90 ms before each pellet injection, i.e. without modifying significantly the current density profile
Infrared thermography of the Tore Supra inner chamber: data acquisition and interpretation
International Nuclear Information System (INIS)
Fleury, I.
1990-03-01
Plasma-wall interactions occur in Tore Supra and undesirable effects take place in the plasma. Moreover, the damage of components may be induced by high energy concentrations. By means of the infrared Tomography diagnostic the components under high thermal flow can be controlled. The design and application of this diagnostic technique is presented. The optical and mechanical structure of the already installed endoscope are described. Three endoscopes are to be used in Tore Supra. The surveillance of the plasma limiters and ergodic divertors can be performed. The monitoring of the temperature variation on the head of the horizontal pumped limiter, during shocks, is carried out. The favourable effect of the ergodic divertor on the power stored on the head is confirmed. The heat decreasing radial length (λ Q ) and the limiter maximal temperatures (Tmax) are evaluated during shocks without a divertor (λ Q = 0.9 cm, Tmax = 440 deg C) or with a divertor current of 40 RA (λ Q = 2.5 cm, Tmax = 230 deg C). Different structures of power concentration, obtained under the effect of the magnetic perturbations induced by the divertor, are shown by means of infrared thermography [fr
Energy Technology Data Exchange (ETDEWEB)
Turlur, S.
1996-09-20
In tokamaks such as Tore Supra, the plasma confinement magnetic structure can be severely affected when Magnetohydrodynamic (M.H.D.) instabilities are destabilized. Experimentally, these instabilities are detected as magnetic fluctuations with captors located against the inner wall of the vacuum vessel. Fourier analysis provides amplitude, frequency and wave numbers of magnetic modes. In case of fast or transient phenomena, the analysis of magnetic fluctuations is completed using the singular value decomposition. In this dissertation, these analysis techniques are used to study two specific examples of M.H.D. activity related to the m = 2, n = 1 mode. On Tore Supra, the onset of this mode have strong consequences on the stability of partially or fully non inductive discharges. A regular and persistent sawtooth-like regime is observed on the electronic temperature leading to a significant degradation of the central confinement. Heat exhaust and particle balance are also essential parameters to achieve stationary discharges. On Tore Supra, these are studied with the ergodic divertor which produces stochastic magnetic field lines at the plasma edge. For optimal operating conditions of the ergodic divertor, the growth of the m = 2, N = 1 mode can lead to sudden destruction of magnetic equilibrium. For both cases, understanding and characterization of mechanisms leading to the observed m = 2, n = 1 M.H.D. activity are fundamental to obtain stationary discharges. (author). 115 refs.
Tore Supra. Basic design Tokamak system
International Nuclear Information System (INIS)
Aymar, R.; Bareyt, B.; Bon Mardion, G.
1980-10-01
This document describes the basic design for the main components of the Tokamak system of Tora Supra. As such, it focuses on the engineering problems, and refers to last year report on Tora Supra (EUR-CEA-1021) for objectives and experimental programme of the apparatus on one hand, and for qualifying tests of the main technical solutions on the other hand. Superconducting toroidal field coil system, vacuum vessels and radiation shields, poloidal field system and cryogenic system are described
Methodology for the design of diagnostic windows for Tore Supra
International Nuclear Information System (INIS)
Missirlian, Marc; Lipa, M.; Portafaix, C.; Gil, C.; Rey, G.
2003-01-01
The next generation of fusion experiments will operate for much longer pulse lengths within a context of high power density, introducing several new requirements for diagnostics compared with existing experiments. In this context, the upgrade of Tore Supra (CIEL Project) foresees high power and high radiating plasma scenario during very long pulse operation. This long plasma operation imposes the improvement of diagnostic systems and the design of thermally resistant in-vessel components with reliable window assemblies. Hence, the specific requirements and the methodology adopted to design Tore Supra/CIEL (TS) high thermal loaded diagnostic windows are summarised in this paper. Thermal and mechanical analyses are reported for different window materials and assembling methods
The plasma facing components of the Tore Supra ICRF antenna
International Nuclear Information System (INIS)
Beaumont, B.; Agarici, G.; Gauthier, E.; Kuus, H.; Schlosser, J.
1994-01-01
Two generations of Faraday shields for the Tore Supra ICRH antennas interacting with the edge plasma are presented. The last one, using a film of boron carbide as protective material performs well, proving the relevance of this technique for in vessel equipment submitted to low power fluxes. The different lateral protections used on Tore Supra are submitted to high power fluxes. Finite element calculations allow to assess their performances. One type, using Boron Carbide, can be used to measure the local heat flux. The estimation of this flux confirm the specificity of the edge/RF interaction, which is more than one order of magnitude above the exponential decay observed in ohmic plasmas. (author) 11 refs.; 1 fig
Experience from Tore Supra acquisition system and evolutions
International Nuclear Information System (INIS)
Guillerminet, B.; Buravand, Y.; Chatelier, E.; Leroux, F.
2004-01-01
The Tore Supra tokamak has been upgraded to explore long duration plasma discharges up to 1000s. Since summer 2001, the acquisition system operates in continuous mode apart of the data processing which is still done after the pulse. In the first part, we explore a few solutions to process continuously the data during the pulse, based on parallel processing on a Linux farm and then on a CONDOR system. The second part is devoted to the Web service exposing the Tore Supra operation. In the last part, the VME acquisition system has been redesigned to keep up with the high data rates required by a few diagnostics. The workflow is now distributed among a few computers. At the end, we give the current status of the realisation and the future planning
Transport and turbulence in TORE SUPRA ohmic discharges
International Nuclear Information System (INIS)
Garbet, X.; Payan, J.; Laviron, C.; Devynck, P.; Saha, S.K.; Capes, H.; Chen, X.P.; Coulon, J.P.; Gil, C.; Harris, G.; Hutter, T.; Pecquet, A.L.
1992-01-01
The mechanisms underlying the energy confinement behaviour in ohmic tokamak discharges are not yet understood. It is well known that the confinement time increases with the average density and saturates above a critical value of the density, but several explanations exist for this saturation. The present study is an analysis of a set of ohmic discharges in Tore Supra with I p =1.6 MA, B=4 T, R=2.35 m and a=0.78 m, where the average density was increased from 0.9 to 4.2 10 19 m -3 . For these plasma parameters, the energy confinement time given by magnetic measurements saturates for e > ≥ 2.5 10 19 m -3 . It is emphasized here that the onset of ionic turbulence is unlikely in Tore Supra. This conclusion relies on a transport analysis and turbulence measurements by CO 2 laser scattering, whose results are presented in this paper
MHD activity triggered by monster sawtooth crashes on Tore Supra
International Nuclear Information System (INIS)
Maget, P; Artaud, J-F; Eriksson, L-G; Huysmans, G; Lazaros, A; Moreau, P; Ottaviani, M; Segui, J-L; Zwingmann, W
2005-01-01
The crash of monster sawteeth in Tore Supra ion cyclotron resonance heated plasmas is observed to trigger long-lived magneto hydrodynamic (MHD) activity, dominated by a (m = 3, n = 2) magnetic perturbation at the edge. This phenomenon is reminiscent of the triggering of neoclassical tearing modes, although in Tore Supra the MHD activity decays and eventually vanishes. It can be explained by the linear destabilization of the (3, 2) mode as the current sheet developed in the non-linear stage of the internal kink relaxation gets closer to q = 3/2. However, the lifetime of the (3, 2) island is longer than the period of linear instability. We find that the neoclassical drive is essential for explaining the observed lifetime and width of the island, although the overall dynamics is controlled by the relaxation of the current profile on a resistive time scale
The TORE SUPRA 300 W - 1.75 K refrigerator
International Nuclear Information System (INIS)
Gistav, G.M.
1986-01-01
The TORE SUPRA refrigerator design and manufacture have both been governed by several strict design criteria. These include reliable operation over long periods (8,000 hours per year), pulsed thermal loads at 1.75 K and 4.0 K (every 4 minutes), fully automatic control in the various operating modes, low operating costs and acting as a technical demonstration so that larger future designs could be extrapolated from this base. The paper reviews these criteria, and presents the current status
Steady state operation and control experiments on Tore Supra
International Nuclear Information System (INIS)
Saint-Laurent, F.
2000-01-01
The main programme of the Tore Supra tokamak is to investigate the route towards long pulse plasma discharges. Tore Supra is thus equipped with a superconducting toroidal magnet, a full set of actively cooled plasma facing components, and a heating and current drive capability based on high power RF systems connected to actively cooled antennas. After pioneering investigations using the LHCD system alone (2 min and zero loop voltage discharges), recent efforts have concentrated on finding scenarios to couple the two RF heating systems in order to perform high power, long duration discharges. To this aim, 6.5 MW, 25 s as well as 4 MW, 60 s discharges have been successfully achieved. At these high power levels, the plasma-wall interaction becomes a critical issue, and recycling fluxes must be controlled to maintain density and to avoid plasma contamination. All these results contributed to the validation of the upgrade of the Tore Supra first wall components (CIEL project) scheduled for 2000. (author)
ORNL compact loop antenna design for TFTR and Tore Supra
International Nuclear Information System (INIS)
Taylor, D.J.; Baity, F.W.; Bryan, W.E.; Hoffman, D.J.; McIlwain, R.L.; Ray, J.M.
1987-01-01
The goal supplemental ion cyclotron resonance heating (ICRH) of fusion plasma is to deliver power at high efficiencies deep within the plasma. The technology for fast-wave ICRH has reached the point of requiring ''proof-of-performance'' demonstration of specific antenna configurations of specific antenna configurations and their mechanical adequacy for operating in a fusion environment. Oak Ridge National Laboratory (ORNL) has developed the compact loop antenna concept based on a resonant double loop (RDL) configuration for use in both Tokamak Fusion Test Reactor (TFTR) and the Tore Supra ICRH programs. A description and a comparison of the technologies developed in the two designs are presented. The electrical circuit and the mechanical philosophy employed are the same for both antennas, but different operating environments result in substantial differences in the design of specific components. The ORNL TFTR antenna is designed to deliver 4 MW over a 2-s pulse, and the ORNL Tore Supra antenna is designed for 4 MW and essentially steady-state conditions. The TFTR design embodies the first operations compact RDL antenna, and the Tore Supra antenna extends the technology to an operational duty cycle consistent with reactor-relevant applications. 7 refs., 5 figs
3400 m/s deuterium pellet injector for Tore Supra
International Nuclear Information System (INIS)
Perin, J.P.; Geraud, A.
1995-01-01
This paper reports on the Tore Supra high velocity pellet injector which was built in Grenoble and after qualification tests installed on Tore Supra Tokomak where it is used for plasma and ablation studies. By using a two stage light gas gun (TSG) and two cells (φ = 3 mm or 4 mm), unsupported pellets pellets (1 to 3.5 10 21 atoms) made directly in the gun by > [1] have been launched into Tore Supra plasma at speeds between 2400m/s and 3400m/s with a reliability of 80%. These higher pellets velocities (> 2500 m/s) [2] are obtained by the optimization of a TSG and the search for the cryogenic conditions of freezing deuterium with good mechanical properties. In particular, the impurities concentration in deuterium during the condensation process has been studied. Several tens pellets have been injected into ohmically and ICR heated plasma and during LH current drive experiments with a good reliability in the range of 3000m/s. These experiments allowed us to extend significantly the ablation data base. Central penetrations can be reached even for high temperatures plasma (3-5 keV) and very peaked density profiles have been obtained in ohmically and ICR heated plasmas A transient improved confinement regime is then observed, which presents some features similar to the PEP regime obtained on JET. (orig.)
Excitation of beta Alfven eigenmodes in Tore-Supra
International Nuclear Information System (INIS)
Nguyen, C; Garbet, X; Sabot, R; Goniche, M; Maget, P; Basiuk, V; Decker, J; Elbeze, D; Huysmans, G T A; Macor, A; Segui, J-L; Schneider, M; Eriksson, L-G
2009-01-01
Modes oscillating at the acoustic frequency and identified as beta Alfven eigenmodes (BAEs) have been observed in Tore-Supra under ion cyclotron resonant heating. In this paper, the linear excitation threshold of these modes, thought to be driven by suprathermal ions, is calculated and compared with Tore-Supra observations. Similar studies of the linear excitation threshold of energetic particles driven modes were carried out previously for toroidal Alfven eigenmodes or fishbones. In the case of BAEs, the main point is to understand whether the energetic particle drive is able to exceed ion Landau damping, which is expected to be important in the acoustic frequency range. For this, the BAE dispersion relation is computed and simplified in order to derive a tractable excitation criterion suitable for comparison with experiments. The observation of BAEs in Tore-Supra is found to be in agreement with the calculated criterion and confirms the possibility to trigger these modes in the presence of ion Landau damping. Moreover, the conducted analysis clearly puts forward the role of the global tunable parameters which play a role in the BAE excitation (the magnetic field, the density etc), as well as the role of some plasma profiles. In particular, the outcome of a modification of the shear or of the heating localization is found to be non-negligible and it is discussed in the paper.
Lower hybrid current drive in Tore Supra and jet
International Nuclear Information System (INIS)
Moreau, D.; Gormezano, C.
1991-07-01
Recent Lower Hybrid Current Drive (LHCD) experiments in TORE SUPRA and JET are reported. Large multijunction launchers have allowed the coupling of 5 MW to the plasma for several seconds with a maximum of 3.8 kW/cm 2 . Measurements of the scattering matrices of the antennae show good agreement with theory. The current drive efficiency in TORE SUPRA is about 0.2 x 10 20 Am -2 /W with LH power alone and reaches 0.4 x 10 20 Am -2 /W in JET thanks to a high volume-averaged electron temperature (1.9 keV) and also to a synergy between Lower Hybrid and Fast Magnetosonic Waves. At average n e = 1.5 x 10 19 m -3 in TORE SUPRA, sawteeth are suppressed and m = 1 MHD oscillations the frequency of which clearly depends on the amount of LH power are observed on soft X-rays, and also on non-thermal ECE. In JET ICRH produced sawtooth-free periods are extended by the application of LHCD (2.9 s. with 4 MW ICRH) and current profile broadening has been clearly observed consistent with off-axis fast electron populations. LH power modulation experiments performed in TORE SUPRA at average n e = 4 x 10 19 m -3 show a delayed central electron heating despite the off-axis creation of suprathermal electrons, thus ruling out the possibility of a direct heating through central wave absorption. A possible explanation in terms of anomalous fast electron transport and classical slowing down would yield a diffusion coefficient of the order of 10 m 2 /s for the fast electrons. Other interpretations such as an anomalous heat pinch or a central confinement enhancement cannot be excluded. Finally, successful pellet fuelling of a partially LH driven plasma was obtained in TORE SUPRA, 28 successive pellets allowing the density to rise to average n e = 4 x 10 19 m -3 . This could be achieved by switching the LH power off for 90 ms before each pellet injection, i.e. without modifying significantly the current density profile
Collection and Characterization of Particulate from the Tore Supra Tokamak (Dec. 1999 Vent)
International Nuclear Information System (INIS)
Sharpe, John Phillip
2002-01-01
Particulate generated during the operation of a fusion device contributes to the radiological source term associated with accident scenarios in the device. Understanding the mechanisms generating the particulate and correctly describing its physical and chemical behavior is essential for safety analyses of future fusion devices. Knowledge of these mechanisms is gained by collecting and characterizing particulate matter from operating fusion facilities. Tokamak dust, the particulate matter generated during the operation of a tokamak fusion device, was collected from Tore Supra in December 1999, during the initial phase of the scheduled shutdown for installation of advanced plasma facing components. Tore Supra, located at CEA Cadarache, France, is presently the third largest operating tokamak with the capability of long-pulse operation. Eighteen super-conducting coils produce the 4.5 T magnetic field inside a vessel 2.4 m in major radius and 1.2 m in minor radius. Limiter and divertor regimes of operation are possible. In the divertor regime, the circular magnetic configuration is ergodized by six outboard resonant divertor modules that are covered with 12 m2 of carbon fiber composite (CFC) tiles. In addition, some field lines are diverted to actively cooled neutralizing plates made of CuCrZr bars covered with B4C. In the limiter regime, the plasma leans on the actively cooled inboard first wall or on a set of inertially cooled pumped limiters. The first wall area of 12 m2 is covered with both polycrystalline graphite tiles (83%) and CFC tiles (17%). The single outboard limiter is constructed of pyrolitic graphite, and the four toroidally symmetric bottom limiters are constructed of CFC. Figure 1.1 displays the relative location of plasma facing components within the plasma chamber of Tore Supra. In this report, we present in Section 2 the methods used to collect and analyze this dust and describe the selection of sampling locations. Section 3 includes a discussion
A step towards controlled fusion reactors: Tore Supra tokamak with superconducting magnets
International Nuclear Information System (INIS)
Turck, B.
1988-01-01
Tore Supra technology has to solve all the problems related to the development and the installaion of superconducting coils and associated cryogenic devices. Tore Supra will allow to get a significative experience to prepare next machines. Specifications and needs of tokamaks concerning the superconducting coils of future machines are recalled [fr
The Tore Supra Lower Hybrid Test Bed : improvements and applications
International Nuclear Information System (INIS)
Delpech, L.; Achard, J.; Beaumont, B.
2006-01-01
Within the CIMES project framework in Tore Supra, a klystron TH2103C (3.7 GHz) is under development at THALES ELECTRON DEVICES. It differs from the previous klystrons used in Tore Supra generator mainly in that it has no modulating anode, the RF output power will reach 700 kW CW, by raising the High Voltage value to 76 kV and a beam current up to 23 A. The Tore Supra test bed is a dedicated facility used for high power tests on RF components or on RF transmitters. It has been improved to integrate the TH2103C klystron and a specific 100 kV solide state switch which control the beam current. Since April 2005, the integration of the first tube (without modulating anode) and the 100 kV switch has been completed in the Test Bed and has allowed the modifications and tests of the interfaces and security system for the devices. Improvements were also made on the cooling loop flow to dissipate a power of 1750 kW CW. With these devices, the RF power routinely available in the Lower Hybrid Test Bed is 400 kW CW. With the development of the TH2103C, detailed studies and tests on RF components which will be used up to 750 kW CW on match load or 700 kW on VSWR = 1.4, are necessary to evaluate their performances and thermal behaviour. The test a crucial component, the recombiner, which adds the RF powers coming from the two RF outputs of the TH2103C and inject the resulted power into one WR284 waveguide to a test load or to the plasma, was completed. Two tests have been performed : a thermal study with 400 kW during 1000 s, and RF pulsed tests on short cuts to increase the value of the electric field inside the component. The experiments and calculations (ANSYS and HFSS codes) validate the use of this device with the TH2103C. A module made with two different Beryllium Oxide RF windows, has been under test. The losses on each window are measured by calorimetric measurements and evaluated by computation with HFSS and ANSYS code. The results are compared. In this paper, the
First results from the Tore-Supra prototype injector
International Nuclear Information System (INIS)
Fumelli, M.; Bottiglioni, F.; Jequier, F.; Pamela, J.
1987-01-01
The first results of the Tore-Supra neutral injector prototype line are presented. The beam was extracted from a 6.6 x 113 cm 2 surface, the plasma source being grounded. The residual fast ion component was electrostatically deflected out of the beam at the exit of the neutralizer. In the first phase of the experiment we operated the injector up to 70 kV and 17 A of extracted deuterium beam. The measured neutral beam power fraction transmitted at 6.4 meter on a 24 x 40 cm 2 target was about 45% of the total extracted power, for a beam divergence of 0.7 0 .te
First results from the Tore-Supra prototype injector
International Nuclear Information System (INIS)
Fumelli, M.; Bottiglioni, F.; Jequier, F.; Pamela, J.
1986-01-01
The first results of the Tore-Supra neutral injector prototype line are presented. The beam extracted from a 6.6 x 113 cm 2 surface, the plasma source being grounded. The residual fast ion component was electrostatically deflected out of the beam at the exit of the neutralizer. In the first phase of experiment we operated the injector up to 70 kV and 17 A of extracted deuterium beam. The measured neutral beam power fraction transmitted at 6.4 meter on a 24 x 40 cm 2 target was about 45% of the total extracted power, for a beam divergence of 0.7 0 . (author)
Effect of Magnetic Field on Pellet Penetration in Tore Supra
International Nuclear Information System (INIS)
Klaywittaphat, P.; Pegourie, B.; Onjun, T.; Imbeaux, F.; Artaud, J. F.; Ge raud, A.; Picha, R.; Poolyarat, N.
2011-06-01
Full text: In this work, we aim to study the effect of magnetic field on pellet penetration in Tore Supra Tokamak using CRONOS integrated predictive modeling code. The Tore Supra plasma discharges with LFS pellet injection (discharges 45072-45085 and 45716-45734) are simulated. In these discharges, the toroidal magnetic field varies from 1.9 to 3.8 tesla. Consecutively, 4 to 6 pellets per discharge are applied. The experimental pellet deposition and penetration can be measured by using CCD camera and interferometer. The CRONOS code with pellet module is used to simulate these experimental results. In these simulations, the core transport is calculated using a combination of the GLF23 anomalous core transport model and the NLCASS neoclassical transport model. The pellet ablation in the hot plasma is described using NGPS pellet ablation model. It is found that the simulation results of pellet penetration agree well with experimental data obtained from the CCD camera. In addition, the result shows that the toroidal magnetic field does not have strong influence on pellet penetration
Calibration procedures of the Tore-Supra infrared endoscopes
Desgranges, C.; Jouve, M.; Balorin, C.; Reichle, R.; Firdaouss, M.; Lipa, M.; Chantant, M.; Gardarein, J. L.; Saille, A.; Loarer, T.
2018-01-01
Five endoscopes equipped with infrared cameras working in the medium infrared range (3-5 μm) are installed on the controlled thermonuclear fusion research device Tore-Supra. These endoscopes aim at monitoring the plasma facing components surface temperature to prevent their overheating. Signals delivered by infrared cameras through endoscopes are analysed and used on the one hand through a real time feedback control loop acting on the heating systems of the plasma to decrease plasma facing components surface temperatures when necessary, on the other hand for physics studies such as determination of the incoming heat flux . To ensure these two roles a very accurate knowledge of the absolute surface temperatures is mandatory. Consequently the infrared endoscopes must be calibrated through a very careful procedure. This means determining their transmission coefficients which is a delicate operation. Methods to calibrate infrared endoscopes during the shutdown period of the Tore-Supra machine will be presented. As they do not allow determining the possible transmittances evolution during operation an in-situ method is presented. It permits the validation of the calibration performed in laboratory as well as the monitoring of their evolution during machine operation. This is possible by the use of the endoscope shutter and a dedicated plasma scenario developed to heat it. Possible improvements of this method are briefly evoked.
Particle retention during long discharges in Tore Supra and JET
International Nuclear Information System (INIS)
Loarer, T.; Tsitrone, E.; Brosset, C.; Bucalossi, J.; Gunn, J.; Joffrin, E.; Monier-Garbet, P.; Pegourie, B.; Thomas, P.; Lomas, P.; Ongena, J.
2003-01-01
The particle balances and the associated particle retentions for the long discharge experiments performed in Tore-Supra and for the L and H mode discharges carried out in JET are reported in this paper. From the reported experiments, the same particle retention behaviors are observed in Tore-Supra and JET in spite of the differences between the plasma geometry and the confinement mode (respectively limiter L-mode and divertor H-mode). A particle retention up to 70-80% of Γ(puff) for the larger gas injection has been obtained in JET. The particle retention behavior observed with the gas puff appears to be strongly dominant in the particle retention process. Indeed, no influence has been noticed from the active pumping, the saturation of the recycling area (0.4 D/C), the precedent discharges history (in terms of total 'particles retained' in the vessel) and even from the disruptions (conditioning). Also, the outgassing between discharges becomes negligible in terms of particle recovering when Γ(puff) and/or the discharge duration are increased. Finally, neither the edge localized modes (ELMs type-I or III) nor the disruptions modify the reported behaviour. For ITER, the particle retention is strictly limited and from the presented results it seems that strong gas injection should be avoided. (A.C.)
Integration of advanced feedback control techniques on Tore Supra
International Nuclear Information System (INIS)
Barana, O.; Basiuk, V.; Bucalossi, J.
2006-01-01
Tore Supra tokamak plays an important role in development and optimisation of steady-state scenarios. Its real-time feedback control system is a key instrument to improve plasma performances. For this reason, new feedback control schemes have been recently put into operation and others are being developed. This work deals with the implementation in Tore Supra of these advanced algorithms, reports the technical details and shows the first positive results that have been achieved. For instance, encouraging results have been obtained in the field of profiles control. Controls of the full width at half maximum of the suprathermal electrons local emission profile at very low loop voltage and of the maximum of the thermal Larmor radius, normalised to the characteristic length of the electron temperature gradient, have been attained. While the first quantity can be directly associated to the current profile, the second one characterises the pressure profile. A new feedback control algorithm, employed to maximise a given quantity by means of a '' Search Optimisation '' technique, has been effectively tested too: the hard X-ray width has been maximised with simultaneous use of lower hybrid heating power and wave parallel index as actuators. These and other promising results, whose detailed description will be given in the article, have been obtained thanks to the real-time availability of several diagnostic systems. Using a shared memory network as communication layer, they send their measurements to a central computing unit that, in its turn, dispatches the necessary requirements to the actuators. A key issue is the possibility to integrate these controls in such a way as to cope with different requests at the same time. As an example, simultaneous control of the plasma current by means of the lower hybrid heating power, of the loop voltage by means of the poloidal field system and of the hard X-ray width through the lower hybrid heating phase shift has been successfully
Energy Technology Data Exchange (ETDEWEB)
Ruggieri, R
2000-01-01
In tokamaks the interaction between wall and plasma generates impurities that affect the thermonuclear fusion. This thesis is divided into 2 parts. The first part describes the physico-chemical processes that are involved in chemical erosion, the second part deals with the study of the wear of Tore-supra's walls due to chemical erosion. Chapter 1 presents the wall-plasma interaction and reviews the different processes between plasma and carbon that occur in Tore-supra. Chapter 2 considers the various crystallographic and electronic structures of the carbon that interferes with Tore-supra plasma, the evolution of these structures during irradiation and their temperature dependence are studied. Chapter 3 presents a crystallo-chemical study of graphite samples that have undergone different surface treatments: ionic bombardment, annealing and air exposure. This experimental study has been performed by using energy-loss spectroscopy. It is shown that air exposure modifies the crystallo-chemical structure of surfaces, so it is necessary to prevent air from contaminating wall samples from Tore-supra. Chapter 4 presents a parametric study of chemical erosion rate of plasma facing components (LPM) of Tore-supra. A relation such as Y{sub cd4}{alpha}{gamma}{sup -0.1} gives a good agreement for chemical erosion rate between measurements and the numerical values of the simulation. (A.C.)
Replacement of the instrumentation and control system of Tore Supra
International Nuclear Information System (INIS)
Leveque, P.
1995-02-01
The control system of the Tore-Supra is a wide and complex system that cannot be interrupted while running without significant consequences on the operating of the machine. Replacing the current system cannot be achieved in a global way without immobilisation and high costs. Therefore partial changes have been decided on. This work presents the detailed analysis of the arrangements and the operating of the system that will be replaced: the pro's and con's that have appeared through experience are related. The possibilities that the new apparatus offers are also examined. A method of step by step replacements had to be set up in order to assess the means, funds, term of achievement, performance and quality of the overall project. (TEC). 15 refs., 29 figs
Pneumatic injector of deuterium macroparticles for TORE-SUPRA tokamak
International Nuclear Information System (INIS)
Vinyar, I.V.; Umov, A.P.; Lukin, A.Ya.; Skoblikov, S.V.; Reznichenko, P.V.; Krasil'nikov, I.A.
2006-01-01
The pneumatic injector for periodic injection of fuel-solid-deuterium pellets into the plasma of the TORE-SUPRA tokamak in a steady-state mode is described. The deuterium pellet injection with an unlimited duration is ensured by a screw extruder in which gaseous deuterium is frozen and squeezed outwards in the form of a rod with a rectangular cross section. A cutter installed on the injector's barrel cuts a cylinder with a diameter of 2 mm and a length of 1.0-3.5 mm out from this rod. The movement of the cutter is controlled by a pulsed electromagnetic drive at a pulse repetition rate of 10 Hz. In the injector's barrel, a compressed gas accelerates a deuterium pellet to a velocity of 100-650 m/s [ru
Current diffusion and flux consumption in Tore Supra
International Nuclear Information System (INIS)
Van Houtte, D.; Talvard, M.; Agostini, E.; Gil, C.; Hoang, G.T.; Lecoustey, P.; Parlange, F.; Rodriguez, L.; Vallet, J.C.
1991-01-01
TORE SUPRA has been designed to study long pulse plasmas (t > 30 s) at high plasma current (Ip < 2 MA) associated with high additional power (20 MW). Current diffusion studies are essentially based on the analysis of the plasma discharge paths. The current diffusion rate during the current rise phase is analysed with a numerical code using plasma resistivity profiles from Te profiles measured by the ECE diagnostic. Owing to the fact that the quantity of magnetic flux available in a tokamak is limited, perfect knowledge is required of the various components of the flux consumed in order to minimize consumption and to be able to define a suitable transformer size for future high current tokamak projects
ITER-like PAM launcher for tore supra's LHCD system
International Nuclear Information System (INIS)
Belo, J.H.; Bibet, Ph.; Missirlian, M.; Achard, J.; Beaumont, B.; Bertrand, B.; Chantant, M.; Chappuis, Ph.; Doceul, L.; Durocher, A.; Gargiulo, L.; Saille, A.; Samaille, F.; Villedieu, E.
2004-01-01
A new launcher based upon the PAM concept (Passive-Active Multijunction) already proposed for ITER has been developed and is currently under realisation at Tore Supra. It was designed for an injection power capability of 2.7 MW CW at 3.7 GHz, a power density of 25 MW/m 2 , to radiate a power spectrum peaked at N || = 1.7 with a maximum power directivity near the electron cut-off density and with very good coupling properties on a wide range of electron densities. In this paper an overall description of the antenna as well as the foreseen manufacturing and assembling processes are given, followed by the results from studies and optimizations of its RF components, and by a stress analysis of its thermomechanical behaviour. (authors)
Edge plasma density convection during ICRH on Tore Supra
International Nuclear Information System (INIS)
Becoulet, M.; Colas, L.; Gunn, J.; Ghendrih, Ph.; Becoulet, A.; Pecoul, S.; Heuraux, S.
2001-11-01
The 2D edge plasma density distribution around ion cyclotron resonance heating (ICRH) antennae is studied experimentally and numerically in the tokamak Tore Supra (TS). A local density decrease in front of the loaded ICRH antenna ('pump-out' effect) is demonstrated by Langmuir probe measurements in a low recycling regime. An up-down asymmetry in the heat-flux and in the antenna erosion is also observed, and is associated with poloidal variations of the local density. These density redistributions are ascribed to an ExB convection process linked with RF-sheaths. To assess this interpretation, the 2D transport code CELLS was developed for modeling the density distribution near an antenna. The code takes into account perpendicular diffusion, parallel transport and convection in RF-sheath-driven potentials given by the 3D-antenna code ICANT. The strong density differences obtained in simulations reproduce up-down asymmetries of the heat fluxes. (authors)
Scrape-off layer flows in the Tore Supra tokamak
International Nuclear Information System (INIS)
Gunn, J.P.; Loarer, T.; Saint-Laurent, F.; Bucalossi, J.; Devynck, P.; Hertout, P.; Moreau, P.; Nanobashvili, I.; Rimini, F.; Duran, I.; Fuchs, V.; Panek, R.; Stockel, J.; Adamek, J.; Dejarnac, R.; Hron, M.; Sarkissian, A.
2005-01-01
Near-sonic parallel flows are systematically observed in the scrape-off layer (SOL) of the limiter tokamak Tore Supra, as in many X-point divertor tokamaks. The poloidal variation of the Mach number of the parallel flow has been measured by moving the contact point of a small circular plasma onto limiters at different poloidal angles. The resulting variations of flow are consistent with the existence of a poloidally nonuniform core-to-SOL out-flux concentrated near the outboard midplane. Strong variations of the SOL width up to a factor of 10 suggest that this localized out-flux is due to enhanced radial transport. The plasma that gets ejected into the SOL can expand radially to the wall if magnetic field lines have long connection lengths and pass unobstructed across the outboard midplane. (authors)
An advanced plasma control system for Tore Supra
International Nuclear Information System (INIS)
Wijnands, T.; Martin, G.
1996-01-01
First results on plasma control with the new plasma control system of Tore Supra are presented. The system has been especially designed for long pulse operation: plasmas are controlled on reference signals, which can be varied in real time by using diagnostic measurements. On line determination of the global plasma equilibrium has enabled new operation scenarios in which both the power from the poloidal field generators and the total Lower Hybrid (LH) power are used to control the plasma. Experiments with feedback control of the safety factor on the plasma boundary, control of the LH driven current, control of the flux on the plasma boundary and control of the internal inductance are discussed. (author)
Current density profile inside q=1 on Tore Supra
International Nuclear Information System (INIS)
Joffrin, E.; Desgranges, C.; Sabot, R.; Dubois, M.A.
1995-01-01
The Tore Supra polarimeter used to measure the poloidal field distribution is described. The current density profiles are computed in two different ways using the interferometric and polarimetric data in conjunction with the magnetic data and the location of the inversion radius determined by the soft X-ray camera. The current density inside the q=1 surface is investigated for normal and monster sawteeth. Its variation are also measured by the polarimeter and compared with that predicted by the current diffusion equation assuming complete reconnection. Finally, the safety factor profile is compared with that obtained with the striation data of the pellet ablation. The results of the evolution of the q profile during sawteeth are in good agreement with those obtained in other devices. (author) 9 refs.; 4 figs
Study of heat flux deposition in the Tore Supra Tokamak
International Nuclear Information System (INIS)
Carpentier, S.
2009-02-01
Accurate measurements of heat loads on internal tokamak components is essential for protection of the device during steady state operation. The optimisation of experimental scenarios also requires an in depth understanding of the physical mechanisms governing the heat flux deposition on the walls. The objective of this study is a detailed characterisation of the heat flux to plasma facing components (PFC) of the Tore Supra tokamak. The power deposited onto Tore Supra PFCs is calculated using an inverse method, which is applied to both the temperature maps measured by infrared thermography and to the enthalpy signals from calorimetry. The derived experimental heat flux maps calculated on the toroidal pumped limiter (TPL) are then compared with theoretical heat flux density distributions from a standard SOL-model. They are two experimental observations that are not consistent with the model: significant heat flux outside the theoretical wetted area, and heat load peaking close to the tangency point between the TPL and the last closed field surface (LCFS). An experimental analysis for several discharges with variable security factors q is made. In the area consistent with the theoretical predictions, this parametric study shows a clear dependence between the heat flux length λ q (estimated in the SOL (scrape-off layer) from the IR measurements) and the magnetic configuration. We observe that the spreading of heat fluxes on the component is compensated by a reduction of the power decay length λ q in the SOL when q decreases. On the other hand, in the area where the derived experimental heat loads are not consistent with the theoretical predictions, we observe that the spreading of heat fluxes outside the theoretical boundary increases when q decreases, and is thus not counterbalanced. (author)
Parametric dependences of impurity transport in the Tore Supra tokamak
International Nuclear Information System (INIS)
Parisot, Th.
2007-09-01
During this Ph.D. work, a full setup of tools for an experimental investigation of impurity transport has been developed on the Tore Supra tokamak. It includes a laser blow-off system for metallic impurity injections and developments for ITC (Impurity Transport Code), a transport code which allows the extraction of the experimental impurity transport coefficients (diffusion and convection velocity). This tool has been used to perform and analyse several experiments, to evidence parametric dependences of impurity transport. In a first experiment, a confinement time law for nickel in Tore Supra has been obtained as a function of collisionality ν * and normalized Larmor radius ρ * . Then the impurity charge Z role has been investigated in various conditions: ohmic regime with or without sawteeth, and sawtooth less L-mode with LH power. No Z effect is observed, consistently with theoretical predictions, whether neoclassical (NCLASS) or for turbulent transport with both non linear gyro-fluid (TRB) and quasilinear gyrokinetic (QuaLiKiz) simulations. An exception is found for LH heated plasmas where the confinement time seems to decrease for the heaviest impurities. This is not explained by any model available. The observed transport is close to neoclassical between sawtooth relaxations, in the centre (r q-1 ) of ohmic plasmas, turbulent outside. Without sawteeth, it is turbulent in the whole plasma, for ohmic or L mode discharges. The profile shape of the diffusion coefficient is here qualitatively different, with a stronger and deeper transition between the low diffusion central region and a more turbulent peripheral region for LH heated plasmas. (author)
International Nuclear Information System (INIS)
Javon, C.; Talvard, M.
1990-01-01
The electron temperature is routinely measured on TORE SUPRA using Fabry-Perot cavities. These have been calibrated using a technique involving coherent addition and Fourier analysis of a chopped black-body source. Comparison with conventional techniques is reported
Energy Technology Data Exchange (ETDEWEB)
Leveque, P.
1995-02-01
The control system of the Tore-Supra is a wide and complex system that cannot be interrupted while running without significant consequences on the operating of the machine. Replacing the current system cannot be achieved in a global way without immobilisation and high costs. Therefore partial changes have been decided on. This work presents the detailed analysis of the arrangements and the operating of the system that will be replaced: the pro`s and con`s that have appeared through experience are related. The possibilities that the new apparatus offers are also examined. A method of step by step replacements had to be set up in order to assess the means, funds, term of achievement, performance and quality of the overall project. (TEC). 15 refs., 29 figs.
Energy Technology Data Exchange (ETDEWEB)
Carpentier, S.
2009-02-15
Accurate measurements of heat loads on internal tokamak components is essential for protection of the device during steady state operation. The optimisation of experimental scenarios also requires an in depth understanding of the physical mechanisms governing the heat flux deposition on the walls. The objective of this study is a detailed characterisation of the heat flux to plasma facing components (PFC) of the Tore Supra tokamak. The power deposited onto Tore Supra PFCs is calculated using an inverse method, which is applied to both the temperature maps measured by infrared thermography and to the enthalpy signals from calorimetry. The derived experimental heat flux maps calculated on the toroidal pumped limiter (TPL) are then compared with theoretical heat flux density distributions from a standard SOL-model. They are two experimental observations that are not consistent with the model: significant heat flux outside the theoretical wetted area, and heat load peaking close to the tangency point between the TPL and the last closed field surface (LCFS). An experimental analysis for several discharges with variable security factors q is made. In the area consistent with the theoretical predictions, this parametric study shows a clear dependence between the heat flux length lambda{sub q} (estimated in the SOL (scrape-off layer) from the IR measurements) and the magnetic configuration. We observe that the spreading of heat fluxes on the component is compensated by a reduction of the power decay length lambda{sub q} in the SOL when q decreases. On the other hand, in the area where the derived experimental heat loads are not consistent with the theoretical predictions, we observe that the spreading of heat fluxes outside the theoretical boundary increases when q decreases, and is thus not counterbalanced. (author)
Energy Technology Data Exchange (ETDEWEB)
NONE
2008-07-01
After a recall of the interest in the fusion for the development of energy sources, the document presents the fusion from the solar reaction to the nuclear fusion in laboratory. Then it discusses the great challenges of this technology and the Tore Supra installation. The last part is devoted to ITER and DEMO projects. (A.L.B.)
Improvement of density control by feedback on Langmuir probe signals in Tore Supra
International Nuclear Information System (INIS)
Gunn, J.; Bucalossi, J.; Costanzo, L.; Grisolia, C.; Ghendrih, Ph.; Grosman, A.; Loarer, T.; Martin, G.; Monier-Garbet, P.; Moulin, D.; Pascal, J.Y.; Saint-Laurent, F.
1999-12-01
Real time control of deuterium or helium gas injection by feedback on Langmuir probe signals is implemented in Tore Supra ergodic divertor discharges. The feedback schemes are based on the robust experimental observation that the density limit coincides with edge temperature T e ∼ 10 eV. Three control algorithms are used: (1) proportional feedback on the central line-averaged density with real-time attenuation of the system gain and security cut-off of the gas injection if the edge temperature becomes too low; (2) proportional feedback on the central line-averaged density with security cut-off controlled by the degree of detachment (DoD); (3) proportional feedback on edge temperature with security cut-off on the DoD. The DoD is defined for deuterium discharges, but not for helium since those do not detach. All three feedback modes permit operation close to the density limit and have been successfully applied for plasma currents 0.4 p p =1.4 MA with up to 4 MW of ICRH power. (author)
Snake-like phenomena in Tore Supra following pellet injection
International Nuclear Information System (INIS)
Pecquet, A.L.; Cristofani, P.; Mattioli, M.; Garbet, X.; Laurent, L.; Geraud, A.; Gil, C.; Joffrin, E.; Sabot, R.
1996-01-01
Snakes are observed in Tore-Supra, after injection of high velocity solid hydrogen or deuterium pellets ablated inside the q=1 surface. They are detected, immediately after the ablation, as oscillations on the line integrated densities of the central interferometer channels. The corresponding oscillations on the soft X-ray signals detach from the noise about 70 ms later. Snakes survive sawtooth crashes, but are nevertheless affected by them. Variations, during the about 500 ms long lifetime, of the snake radius τ s , of the rotation frequency and of the rotation direction are discussed, stressing the effects of the sawtooth crashes. In many snakes τ s /τ q =1 is of the order of 0.5. Since the snake has a m=1, n=1 helicity, this points out the existence of a flat or inverted safety factor profile, confirmed by calculation of the current profile using Spitzer's resistivity. Combined simulations of the snake oscillations on both interferometer and soft X-ray signals have indicated that, starting about 80 ms after the snake formation, the impurity (carbon) density inside the snake is much larger than outside it. Since a change of regime seems to appear about 80 ms after the snake formation on the soft X-ray, it seems plausible that impurity (carbon) accumulation takes place at this time. A stability criterion taking into account both impurity and bootstrap effects is presented, the result agrees with the model proposed by Wesson. (authors)
Technical and human feedbacks about Tore Supra control system
Energy Technology Data Exchange (ETDEWEB)
Fejoz, P.; Baudet, J.; Lebourg, P. [CEA Cadarache, IRFM, 13 - Saint-Paul-lez-Durance (France)
2009-07-01
Full text of publication follows: During the 23 years of the Tore Supra tokamak operation, we went through several technological boom in many domains such as electronics, software development, robotics and automatics. Even if the initial control-command system fitted all the requirements and satisfied the users, it was not possible to maintain such a system over the years without deep changes. Important issues have appeared: some software or hardware were no more maintained by the suppliers, the performances were not up to date, the human interface were outdated, requirements evolved. The goals were to upgrade and make durable the application programming interface park and the related human-machine interfaces. To reach these objectives we had to face several challenges: -) The training of the staff (programmers and end-users); -) The integration of new equipment in the current architecture; -) The cohabitation between new and old systems; -) The continuity of the operation; -) Make the good choice to go along without any new overhaul. (authors)
Turbulence and energy confinement in TORE SUPRA ohmic discharges
International Nuclear Information System (INIS)
Garbet, X.; Payan, J.; Laviron, C.; Devynck, P.; Saha, S.K.; Capes, H.; Chen, X.P.; Coulon, J.P.; Gil, C.; Harris, G.; Hutter, T.; Pecquet, A.L.
1992-06-01
Results on confinement and turbulence from a set of ohmic discharges in Tore Supra are discussed. The attention is focused on the saturation of the energy confinement time and it is emphasized that this saturation could be explained by a saturation of the electron heat diffusivity. Ion behaviour is indeed governed by dilution and equipartition effects. Although the ion heat transport is never neoclassical, there is no enhanced degradation at the saturation. This behaviour is confirmed by turbulence measurements given by CO 2 laser coherent scattering. The density fluctuations level follows the electron heat diffusivity variations with the average density. Waves propagating in the ion diamagnetic direction are always present in turbulence frequency spectra. Thus, the saturation cannot be explained by the onset of an ion turbulence. The existence of an ion turbulence at the edge at all densities cannot be excluded. However, this ion feature in scattering spectra could be explained by a Doppler shift associated to an inversion point of the radial electric field at the edge
Structural design of the Tore Supra Phase III limiter head
International Nuclear Information System (INIS)
Dempsey, J.F.; Koski, J.A.; Watson, R.D.
1992-01-01
The Sandia National Laboratories Fusion Technology Division has designed and fabricated an actively cooled pumped limiter for use in Tore Supra. The limiter head is composed of an integrated high tolerance contoured surface of pyrolytic graphite (PG) tiles brazed to 14 independent OFHC (oxygen free high conductivity) copper tube segments. The limiter is designed to absorb up to 2 MW of incident power and peak heat fluxes up to 30 MW/m 2 under nominal plasma operating conditions. The limiter will also receive vibrational loads induced by plasma disruptions. This paper discusses innovative support techniques that are used to prevent misalignment of the tubes in the limiter head during plasma operations. Thermal misalignment of the limiter with respect to the toroidal field will damage the limiter, therefore, all tubes in the tube bank must be maintained in good alignment with each other. In order to minimize limiter damage due to misalignment and dynamic chattering loads without increasing eddy current loads, a design which weaves the limiter head together with flexible strands of inconel wire evolved
Multichannel and multicolor infrared thermography in Tore Supra
International Nuclear Information System (INIS)
Reichle, R.; Pocheau, C.; Balorin, C.; Delchambre, E.; Desgrange, C.; Guilhem, D.; Messina, P.; Roche, H.
2004-01-01
An imaging spectrometer using a sapphire prism as dispersing element has been conceived at Tore Supra for the spectral range of 1 - 4 μm. It measures simultaneously at various wavelengths the temperature on distributed high heat-flux elements under plasma impact with 36 optical fibres, 4 of which are ZrF 4 fibres. It employs an InSb focal plane array detector (256*320 pixels) behind a silicon filter and a ZnS window yielding a dynamic range of 200 to 1500 deg C with 20 ms temporal resolution. The fibre transmission and the spatial variation of gain and background of the camera are calibrated using a light source with integrating sphere. With a black body source one determines the non linearity of the average gain and controls its stability during operation. The spectral dispersion of about 30 nm/pixel is determined with interference filters and controlled with a spectral lamp. The measurements at various wavelengths allow to determine the temperature distribution in the held of view. (author)
Improvement of the Gyrotron TH 1506B for Tore Supra
Energy Technology Data Exchange (ETDEWEB)
Magne, R.; Bouquey, F.; Clary, J.; Darbos, C.; Jung, M.; Lambert, R.; Lennholm, M.; Roux, D. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Alberti, S.; Hogge, J.P. [Association Euratom-Confederation Suisse, EPFL - CRPP, Lausanne (Switzerland); Bariou, D.; Legrand, F.; Lievin, C. [Thales Electron Devices, Microwave Tubes and Devices, 78 - Velizy (France); Arnold, A.; Thumm, M. [Association Euratom-FZK, IHM, Karlsruhe (Germany)
2004-07-01
For heating and current drive experiments by electron cyclotron resonance interaction on Tore Supra tokamak, a new generator is presently under construction. The generator is made of 6 gyrotrons TH-1506B. Tests made on the first series gyrotron have revealed some unexpected limitations: the most visible was an insufficient cooling of the mirror box, another one was the observation of a spurious oscillation at the output of the gyrotron at a frequency close to 119,7 GHz. The design of the mirror box has been modified, it was decided to use a double-wall structure with water flowing between. As for preventing the spurious oscillation, calculations have shown that it would be sufficient to add a very small conical angle to the launcher profile. A new generator has been built according to this new design. Tests have shown that previous limitations have disappeared but the output beam seems to be not perfectly Gaussian probably due to the launcher. Studies are being made to understand this problem in order to optimize the design for the following 5 gyrotrons. (A.C.)
Towards high-power long-pulse operation on Tore Supra
International Nuclear Information System (INIS)
2000-01-01
The Tore Supra tokamak was given the main mission to investigate the route towards long pulse plasma discharges. This includes the problem of heat exhaust and particle control (via the development of high-performance plasma facing components), and in parallel the physics of fully non inductive discharges and its optimization with respect to the confinement. Tore Supra is thus equipped with a superconducting toroidal magnet (maximum magnetic field on axis 4.5T), a full set of actively cooled plasma facing components (PFC), and a heating and current drive capability based on high power RIF systems connected to actively cooled antennas. The encouraging results already obtained, as well as recent progress in PFC, allowed us to envisage a significant improvement in the heat exhaust capability of Tore Supra. The so-called CIEL-project consists in a complete upgrade of the inner chamber of Tore Supra, planned to be installed during the year 2000. The present paper deals with the experimental and modeling activity linked to the preparation of the long-pulse high-power discharges using the present Tore Supra equipment: heating and current drive scenarios, power coupling, confinement and transport studies, discharge control... An overview of the results obtained in that field is presented, as well as the progress required in the coming years, and the expected performance, for the CIEL phase, in terms of current drive and confinement. (author)
Towards high-power long-pulse operation on Tore Supra
International Nuclear Information System (INIS)
2001-01-01
The Tore Supra tokamak was given the main mission to investigate the route towards long pulse plasma discharges. This includes the problem of heat exhaust and particle control (via the development of performant plasma facing components), and in parallel the physics of fully non inductive discharges and its optimisation with respect to the confinement. Tore Supra is thus equipped with a superconducting toroidal magnet (maximum magnetic field on axis 4.5T), a full set of actively cooled plasma facing components (PFC), and a heating and current drive capability based on high power RF systems connected to actively cooled antennas. The encouraging results already obtained, as well as recent progress in PFC, allowed us to envisaged a significant improvement in the heat exhaust capability of Tore Supra. The so-called CIEL-project consists in a complete upgrade of the inner chamber of Tore Supra, planned to be installed during the year 2000. The present paper deals with the experimental and modelling activity linked to the preparation of the long-pulse high-power discharges using the present Tore Supra equipment: heating and current drive scenarios, power coupling, confinement and transport studies, discharge control,... An overview of the results obtained in that field is presented, as well as the progress required in the coming years, and the expected performance, for the CIEL phase, in terms of current drive and confinement. (author)
Towards operations on Tore Supra of an ITER relevant inspection robot and associated processes
International Nuclear Information System (INIS)
Gargiulo, L.; Cordier, J.J.; Friconneau, J.P.; Grisolia, C.; Palmer, J.D.; Perrot, Y.; Samaille, F.
2007-01-01
The aim of the project is to demonstrate on Tore Supra the reliability of a multi-purpose in-vessel remote handling inspection system using a long reach, limited payload carrier. The robot prototype is fully representative of the deployment carrier system that could be required on ITER. The demonstration on Tore Supra will help in the understanding of operation issues that could occur in the tokamak vacuum vessel equipped of actively cooled components. The viewing process that is currently under development will allow close inspection of the Tore Supra plasma facing components that are representative of the ITER divertor targets in terms of confined environment and identification of possible tiles failure of CFC carbon tiles. One of the other potential inspection processes that is foreseen to be tested using the AIA carrier in Tore Supra is the laser ablation system of the CFC armour. It could be fully relevant for the ITER wall detritiation issues. Such process can be simulated on Tore Supra through the deuterium inventory under long-time plasma discharges. The in situ leakage localisation of a damaged plasma facing component is also one of the major ITER maintenance challenges that could use remote handling inspection tools
Towards operations on Tore Supra of an ITER relevant inspection robot and associated processes
Energy Technology Data Exchange (ETDEWEB)
Gargiulo, L. [Association Euratom-CEA, DSM/Departement de Recherche sur la Fusion Controlee, CEA/Cadarache, F-13108 Saint Paul Lez Durance Cedex (France)], E-mail: laurent.gargiulo@cea.fr; Cordier, J.J. [Association Euratom-CEA, DSM/Departement de Recherche sur la Fusion Controlee, CEA/Cadarache, F-13108 Saint Paul Lez Durance Cedex (France); Friconneau, J.P. [CEA-LIST Robotics and Interactive Systems Unit, BP6 F-92265 Fontenay aux Roses Cedex (France); Grisolia, C. [Association Euratom-CEA, DSM/Departement de Recherche sur la Fusion Controlee, CEA/Cadarache, F-13108 Saint Paul Lez Durance Cedex (France); Palmer, J.D. [EFDA CSU, Max-Planck-Institut fuer Plasma Physik Boltzmannstr. 2, D-85748 Garching (Germany); Perrot, Y. [CEA-LIST Robotics and Interactive Systems Unit, BP6 F-92265 Fontenay aux Roses Cedex (France); Samaille, F. [Association Euratom-CEA, DSM/Departement de Recherche sur la Fusion Controlee, CEA/Cadarache, F-13108 Saint Paul Lez Durance Cedex (France)
2007-10-15
The aim of the project is to demonstrate on Tore Supra the reliability of a multi-purpose in-vessel remote handling inspection system using a long reach, limited payload carrier. The robot prototype is fully representative of the deployment carrier system that could be required on ITER. The demonstration on Tore Supra will help in the understanding of operation issues that could occur in the tokamak vacuum vessel equipped of actively cooled components. The viewing process that is currently under development will allow close inspection of the Tore Supra plasma facing components that are representative of the ITER divertor targets in terms of confined environment and identification of possible tiles failure of CFC carbon tiles. One of the other potential inspection processes that is foreseen to be tested using the AIA carrier in Tore Supra is the laser ablation system of the CFC armour. It could be fully relevant for the ITER wall detritiation issues. Such process can be simulated on Tore Supra through the deuterium inventory under long-time plasma discharges. The in situ leakage localisation of a damaged plasma facing component is also one of the major ITER maintenance challenges that could use remote handling inspection tools.
Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak
International Nuclear Information System (INIS)
Jakubowski, L.; Sadowski, M. J.; Zebrowski, J.; Rabinski, M.; Malinowski, K.; Mirowski, R.; Lotte, Ph.; Gunn, J.; Pascal, J-Y.; Colledani, G.; Basiuk, V.; Goniche, M.; Lipa, M.
2010-01-01
The paper presents a schematic design and tests of a system applicable for measurements of fast electron pulses emitted from high-temperature plasma generated inside magnetic confinement fusion machines, and particularly in the TORE-SUPRA facility. The diagnostic system based on the registration of the Cherenkov radiation induced by fast electrons within selected solid radiators is considered, and electron low-energy thresholds for different radiators are given. There are some estimates of high thermal loads, which might be deposited by intense electron beams upon parts of the diagnostic equipment within the TORE-SUPRA device. There are some proposed measures to overcome this difficulty by the selection of appropriate absorption filters and Cherenkov radiators, and particularly by the application of a fast-moving reciprocating probe. The paper describes the measuring system, its tests, as well as some results of the preliminary measurements of fast electrons within TORE-SUPRA facility.
Implementation of FCI heating system to the control system of Tore-Supra
International Nuclear Information System (INIS)
Wisniewski, S.
2001-11-01
This report presents the implementation of the ion cyclotron resonance heating system (FCI) to the instrumentation and control system of the Tore-Supra tokamak. The new plasma heating system involves 3 antennas delivering 12 MW that are required to maintain fusion reactions. This paper is divided into 8 chapters: 1) thermonuclear fusion and Tore-Supra tokamak; 2) hardware system around Tore-Supra, in this chapter the control system and the data acquisition and processing systems are presented; 3) functional analysis, this analysis defines the different needs concerning timing and pilot-controlling, a preliminary proposition of hardware equipment is made; 4) operating modes of FCI; 5) communication within the control system network; 6) communication with the supervisory system of the power stations; 7) management of data exchange with SMX generators; and 8) control of the rate of stationary waves during the injection of power into the plasma
Major progress on tore supra toward steady state operation of tokamaks
International Nuclear Information System (INIS)
Saoutic, Y.
2003-01-01
During winter 2000-2001, a major upgrade of the internal components of Tore Supra has been completed that increased the heat extraction capability to 25 MW in steady state. Operating Tore Supra in this new configuration has produced a wealth of new results. The highlights of the 2002 long duration discharges campaign are: 4 minutes 25 seconds long discharges with an integrated energy of 0.75 GJ, which is three time higher than the old Tore Supra world record; recharge of the primary transformer by Lower Hybrid Current Drive (LHCD) for about 1 minute; 4 minutes long LHCD pulses; 1 minute long Ion Cyclotron Resonant Heating (ICRH) pulse (0.11 GJ of ICRH injected energy). Beyond the quantitative step, significant qualitative progress in the steady state nature of the discharge has been accomplished: contrary to the situation in the old Tore Supra configuration, the plasma density is perfectly controlled by active pumping over the overall shot duration. The duration of Tore Supra discharges is sufficient to allow the complete diffusion of the resistive current. Surprising new physics is revealed in such discharges when approaching zero loop voltage. Slow central electron temperature oscillations have been observed in a variety of situations. Such oscillations are not likely to be linked to any MHD instabilities and probably results from an interplay between current profile shape, LHCD power deposition and transport. Analysis of the temperature gradient in the core region shows a very interesting behaviour and the normalised temperature gradient length is compared to the critical thresholds. Finally, the performance of heating and current drive systems and the observations made of the interior of Tore Supra after the long duration discharges campaign are reported. (author)
Long Discharge Particle Balance and Fuel Retention in Tore Supra
Pégourié, B.; Brosset, C.; Delchambre, E.; Loarer, T.; Roubin, P.; Tsitrone, E.; Bucalossi, J.; Gunn, J.; Khodja, H.; Lafon, C.; Martin, C.; Parent, P.; Reichle, R.
In the new CIEL configuration of Tore Supra, all the plasma facing components are actively cooled. The surface area of the wall that is covered with carbon measures about 15 m2 (2 to 4 m2 of which in close interaction with the plasma). Steady-state plasma conditions up to 4 min 25 s have been maintained in this configuration. In these experiments, the required gas injection to maintain the prescribed density remains constant during the whole discharge. The exhausted flux is also constant and equal to 40 A~· 50% of the injected flux. Therefore, 50 A~· 60% of the injected particles remain trapped in the vessel, the total retention being proportional to the plasma duration. Since the amount of gas recovered between shots or by He-glow discharges does not always balance the injected gas, it follows that a quantity of deuterium remains indefinitely trapped in the vessel, which appears as an infinite reservoir. This reservoir is believed to be dominated by co-deposited layers, as observed in several places of the vessel. The thickest deposits (up to 800 Î 1/4 m) are observed on the leading edge of the neutralizers of the pump limiter. They display a column-like shape (typical growth rate âe 1/4 20 nm/s) and have a graphite-like structure. Their deuterium concentration is D/C âe 1/4 1%. Conversely, in regions that are shadowed from the direct plasma flux, the deposits show a smoother shape and their deuterium content is typically âe 1/4 10 A~· 15%.
Validation of the LH antenna code ALOHA against Tore Supra experiments
International Nuclear Information System (INIS)
Hillairet, J.; Ekedahl, A.; Kocan, M.; Gunn, J. P.; Goniche, M.
2009-01-01
Comparisons between ALOHA code predictions and experimental measurements of reflection coefficients for the two different Lower Hybrid Current Drive (LHCD) antennas (named C2 and C3) in Tore Supra are presented. A large variation of density in front of the antennas was obtained by varying the distance between the plasma and the antennas. Low power ( 2 ) was used in order to avoid non-linear effects on the wave coupling. Results obtained with ALOHA are in good agreement with the experimental measurements for both Tore Supra antennas and show that ALOHA is an efficient LH predictive tool.
Spatially resolved charge exchange flux calculations on the Toroidal Pumped Limiter of Tore Supra
International Nuclear Information System (INIS)
Marandet, Y.; Tsitrone, E.; Boerner, P.; Reiter, D.; Beaute, A.; Delchambre, E.; Escarguel, A.; Brezinsek, S.; Genesio, P.; Gunn, J.; Monier-Garbet, P.; Mitteau, R.; Pegourie, B.
2009-01-01
A spatially resolved calculation of the charge exchange particle and energy fluxes on the Toroidal Pumped Limiter (TPL) of Tore Supra is presented, as a first step towards a better understanding and modelling of carbon erosion, migration, as well as deuterium codeposition and bulk diffusion of deuterium in Tore Supra. The results are obtained with the EIRENE code run in a 3D geometry. Physical and chemical erosion maps on the TPL are calculated, and the contribution of neutrals to erosion, especially in the self-shadowed area, is calculated.
Ion Temperature Measurements in the Tore Supra Scrape-Off Layer Using a Retarding Field Analyzer
International Nuclear Information System (INIS)
Kocan, M.; Gunn, J.P.; Pascal, J.Y.; Gauthier, E.
2010-01-01
The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measuring the ion temperature T i )in the tokamak scrape-off layer. An overview of the outstanding RFA performance over ten years of operation in Tore Supra tokamak is given and the validation of T i measurements is addressed. The RFA measurements in Tore Supra are found to be well reproducible. The ion-to-electron temperature ratio is higher than one at low-to-moderate ion-electron collisionality regime and converges to unity at high collisionality regime. (authors)
Towards operations on Tore Supra of an ITER relevant inspection robot and associated processes
International Nuclear Information System (INIS)
Laurent Gargiulo, L.; Cordier, J.-J.; Samaille, F.; Grisolia, Ch.; Perrot, Y.; Olivier, D.; Friconneau, J.-P.; Palmer, J.
2006-01-01
The aim of the project is to demonstrate on Tore Supra the reliability of a multi-purpose in-vessel Remote Handling inspection system using a long reach, limited payload carrier. This project called AIA (Articulated Inspection Arm) is currently being developed at CEA under a European EFDA work program. The paper describes the detailed design, the manufacturing processes and the results of the first module test campaign in the CEA Tore Supra ME60 facility, at representative vacuum, temperature and nominal loading conditions. The second part of this work that is reported in the paper, concerns the description of the whole integration of the device on the Tore Supra tokamak that is foreseen to be operated on Tore Supra early 2007. The deployer system and the 10 m long storage vacuum vessel are presented. The robot prototype is fully representative of the deployment carrier system that could be required on ITER. The demonstration on Tore Supra will help in the understanding of operation issues that could occur in the tokamak vacuum vessel equipped of actively cooled components. The viewing process that is currently under development is presented in the paper. It will allow close inspection of the Tore Supra Plasma Facing Components that are representative of the ITER divertor targets in terms of confined environment and identification of possible tiles failure of CFC carbon tiles. Such viewing process could be used on ITER during the early stage of operation under a limited radiation level. The AIA technology is also showing promising potential for generic application in alternative systems for ITER. The feasibility study for viewing inspection of the beam line components in the neutral beam test facility is presented. One of the other potential inspection processes that is foreseen to be tested using the AIA carrier in Tore Supra is the laser ablation system of the CFC armour. It could be fully relevant for the ITER wall detritiation issues. Such process can be
First lower hybrid current drive experiments at 3.7 GHz in Tore Supra
International Nuclear Information System (INIS)
Tonon, G.; Goniche, M.; Moreau, D.
1989-01-01
The results of electromagnetic waves injection in the Tore Supra plasma, at a frequency of 3.7 GHz, are reported. The process is applied for current generation and plasma heating, through Landau damping on the electron population. The experimental set-up is described. The lower hybrid current drive experiments in Tore Supra are carried out under the following conditions: major and minor radii of the plasma are respectively 2.37 m and 0.77 m and the toroidal magnetic field is 1.8 Teslas. A multijunction-grill composed of 128 waveguides is applied. Up to 1.25 MW of rf power is injected in Tore Supra, after less than 30 plasma shots. The results lead to the conclusion that the coupling, not yet optimized, is good enough for safe klystron operation with no circulator. The measured value RIp P RF -1 (δV L /V L ) obtained on Tore Supra (Bt = 1.8 T) is closed to one observed on PETULA-B (Bt = 2.75 T) at the same frequency and density
Radio frequency additional heating systems issues for the TORE-SUPRA WEST project
Guilhem, D.; Argouarch, A.; Bernard, J.M.; Bouquey, F.; Colas, L.; Delpech, L.; Durodié, F.; Ekedahl, A.; Helvoirt, J.; Hillairet, J.; Joffrin, E.; Litaudon, X.; Magne, R.; Milanesio, D.; Moerel, J.; Mollard, P.; Wittebol, E.; Achard, J.; Armitano, A.; Berger-By, G.; Charabot, N.; Goniche, M.; Jacquot, J.; Lombard, G.; Prou, M.; Traisnel-Corbel, E.; Volpe, R.; Vulliez, K.
2013-01-01
This year TORE-SUPRA celebrated its 25 years of operation. During this long time a number of technologies have been developed [1]. First of all it was mandatory to develop reliable superconducting magnets at ∼ - 4 K, with superfluid helium as efficient coolant. For the production of steady state
Steady-state operation of tokamaks: Key physics and technology developments on Tore Supra
International Nuclear Information System (INIS)
Jacquinot, J.
2005-01-01
Important technological and physics issues related to long pulse operation required for a reactor are now being addressed in Tore Supra. experimental results in conditions where all the plasma facing components are actively cooled during pulses exceeding six minutes. Important physics issues related to continuous operation are observed in non inductively driven plasmas. (author)
Upgraded ECE radiometer on the Tore Supra Tokamak
Energy Technology Data Exchange (ETDEWEB)
Segui, J.L.; Molina, D.; Goniche, M.; Maget, P.; Udintsev, V.S. [Association Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Antar, G.Y. [Center for Energy Research, UCSD, La Jolla CA (United States); Kraemer-Flecken, A. [Forschungszentrum Juelich GmbH (Germany). Inst. fuer Plasmaphysik
2004-07-01
An upgraded 32-channel heterodyne radiometer, 1 GHz spaced, is used on the Tore-Supra tokamak to measure the electron cyclotron emission (ECE) in the frequency range 78-110 GHz for the ordinary mode (O1) and 94-126.5 GHz for the extraordinary mode (X2). From now radial resolution is essentially limited by ECE relativistic effects related to electron temperature and density, not by the channels frequency spacing. For example, this leads to precise electron temperature mapping during magneto hydrodynamic activities (MHD). In the equatorial plane, we use a dual polarisation Gaussian optics lens antenna. It has low spreading and a perpendicular line-of-sight that gives ECE measurements very low refraction and Doppler effects. Assuming that the plasma is a black body and there is no overlap between ECE harmonics, one can deduce the electron temperature profile by using the first harmonic ordinary mode (O1) or the second harmonic extraordinary mode (X2). The principle radio frequency emitter (RF) has its frequencies down shifted into intermediary frequencies (IF) that span from 2 to 18 GHz in the single side band mode (SSB). It is amplified by low noise IF amplifiers before forming channels. A separate O/X mode RF front-end allows the use of an IF electronic mode selector. This gives the potentiality of simultaneous O/X mode measurements in the 94-110 GHz. RF and IF filters reject the gyrotron frequency (118 GHz) in order to perform electron temperature measurements during electron cyclotron resonance heated plasmas. A precise absolute spectral calibration is performed outside the tokamak vacuum vessel by using a 600 deg C black body hot source, a double coherent digital signal averaging (trigger, turn and clock) on the waveform generated by a mechanical chopper, and a simulated tokamak window. The use of differential electronics and strong electromagnetic shielding improves also the calibration precision. The fast and slow data acquisition systems are free of aliasing
Upgraded ECE radiometer on the Tore Supra Tokamak
International Nuclear Information System (INIS)
Segui, J.L.; Molina, D.; Goniche, M.; Maget, P.; Udintsev, V.S.; Kraemer-Flecken, A.
2004-01-01
An upgraded 32-channel heterodyne radiometer, 1 GHz spaced, is used on the Tore-Supra tokamak to measure the electron cyclotron emission (ECE) in the frequency range 78-110 GHz for the ordinary mode (O1) and 94-126.5 GHz for the extraordinary mode (X2). From now radial resolution is essentially limited by ECE relativistic effects related to electron temperature and density, not by the channels frequency spacing. For example, this leads to precise electron temperature mapping during magneto hydrodynamic activities (MHD). In the equatorial plane, we use a dual polarisation Gaussian optics lens antenna. It has low spreading and a perpendicular line-of-sight that gives ECE measurements very low refraction and Doppler effects. Assuming that the plasma is a black body and there is no overlap between ECE harmonics, one can deduce the electron temperature profile by using the first harmonic ordinary mode (O1) or the second harmonic extraordinary mode (X2). The principle radio frequency emitter (RF) has its frequencies down shifted into intermediary frequencies (IF) that span from 2 to 18 GHz in the single side band mode (SSB). It is amplified by low noise IF amplifiers before forming channels. A separate O/X mode RF front-end allows the use of an IF electronic mode selector. This gives the potentiality of simultaneous O/X mode measurements in the 94-110 GHz. RF and IF filters reject the gyrotron frequency (118 GHz) in order to perform electron temperature measurements during electron cyclotron resonance heated plasmas. A precise absolute spectral calibration is performed outside the tokamak vacuum vessel by using a 600 deg C black body hot source, a double coherent digital signal averaging (trigger, turn and clock) on the waveform generated by a mechanical chopper, and a simulated tokamak window. The use of differential electronics and strong electromagnetic shielding improves also the calibration precision. The fast and slow data acquisition systems are free of aliasing
The 118-GHz electron cyclotron heating system on Tore Supra
Energy Technology Data Exchange (ETDEWEB)
Darbos, C.; Magne, R.; Bouquey, F.; Lambert, R.; Lennholm, M.; Traisnel, E. [CEA, IRFM, F-13108 St Paul Les Durance, (France); Arnold, A.; Thumm, M. [Univ Karlsruhe, Inst Hochfrequenztech and Elect, Karlsruhe, (Germany); Prinz, H.O.; Thumm, M. [EURATOM, Forschungszentrum Karlsruhe, Inst Hochleistungsimpuls und Mikrowellentech, Karlsruhe, (Germany); Hogge, J.P. [Assoc Euratom Confederat Suisse, Lausanne, (Switzerland); Lievin, C. [Thales Electron Devices, Velizy Villacoublay, (France)
2009-07-01
An electron cyclotron resonance heating (ECRH) system capable of delivering 2.4 MW cw has been designed to be built at Commissariat a l'Energie Atomique. Cadarache, for the Tore Supra (TS) experiment, to provide plasma heating and current drive by electron cyclotron resonance interaction. The planned system was composed of a generator using six gyrotrons 500 kW for 5 s or 400 kW cw working at 118 GHz. Six transmission lines made of corrugated waveguide, 63.5-mm diameter, carry. the HE11 mode to one antenna composed of six fixed mirrors and three independently movable mirrors for the adjustment of the injection angles of the rf beams. The antenna was built and installed in TS., and all transmission line components ordered and installed between the gyrotron locations and the antenna. In the same way, the required six oil tanks, the six cryo-magnets, and the six modulating anode devices were designed and manufactured. In parallel, after demonstration in the factory of proper operation of the prototype gyrotron, the manufacture of a first so-called series gyrotron was made. Bill this gyrotron experienced hard limitations (overheating inducing prohibited outgassing, parasitic oscillations) during the long-pulse tests in Cadarache, and the achieved performance was 300 kW for 110 s. A new study was then carried out in collaboration with Thales Electron Devices, the EURATOM-CEA Association. and the EURATOM-Confederation Suisse Association to understand and overcome the limitations, which led to the construction of a nest, modified gyrotron. During the tests in factory of this new gyrotron, the output beam showed two peaks, a pattern never predicted by simulations. The gyrotron was nevertheless transferred to Cadarache for long-pulse testing, but all arc oil the windows definitely stopped the tests. To understand the cause of the observed two peaks, various low-level tests were then performed oil a model of the mode converter with different shapes for the launcher; but
International Nuclear Information System (INIS)
Anon.
1982-01-01
The decision to grant priority operation status to the French Tokamak Tore Supra will make it possible to start on the construction of this large machine and to bring together at the Cadarache Nuclear Study Centre all the facilities of the CEA for their research on fusion by magnetic confinement. The work is scheduled to begin in 1982 and to last until 1985. The financing is indicated and Tore Supra is briefly described [fr
Management of water leaks on Tore Supra actively cooled fusion device
International Nuclear Information System (INIS)
Hatchressian, J.C.; Gargiulo, L.; Samaille, F.; Soler, B.
2005-01-01
Up to now, Tore Supra is the only fusion device fully equipped with actively cooled Plasma Facing Components (PFCs). In case of abnormal events during a plasma discharge, the PFCs could be submitted to a transient high power density (run away electrons) or to a continuous phenomena as local thermal flux induced by trapped suprathermal electrons or ions). It could lead to a degradation of the PFC integrity and in the worst case to a water leak occurrence. Such water leak has important consequence on the tokamak operation that concerns PFCs themselves, monitoring equipment located in the vacuum vessel or connected to the ports as RF antennas, diagnostics or pumping systems. Following successive water leak events (the most important water leak, that occurred in September 2002, is described in the paper), a large feedback experience has been gained on Tore supra since more than 15 years that could be useful to actively cooled next devices as W7X and ITER. (authors)
Conceptual design of a high heat flux toroidal pumped limiter for Tore Supra
International Nuclear Information System (INIS)
Doceul, L.; Schlosser, J.; Chappuis, Ph.; Chatelier, M.; Cocat, J.P.; Deck, C.; Faisse, F.; Grosman, A.; Mitteau, R.; Tonon, G.
1994-01-01
In the frame of the Tore-Supra upgrade, where it is planned to inject up to 25 MW during a time up to 1000 s, a complete toroidal pumped limiter covered of CFC (Carbon Fiber Composite) tiles is being designed. The design is based on the important experience gained from the operation on Tore Supra of actively cooled plasma facing components and pumped limiters. This toroidal limiter covers 7.5 m 2 of the bottom part of the inner vessel and is composed of 576 elementary components. Each element is built from dispersion strengthened copper (DSCu) protected by brazed CFC flat tiles and cooled by pressurised water at 150 deg C. This limiter is designed to sustain 15 MW of convective power. (author) 7 refs.; 5 figs., 3 tabs
Experience gained from high heat flux actively cooled PFCs in Tore Supra
International Nuclear Information System (INIS)
Grosman, A.; Bayetti, P.; Brosset, C.; Bucalossi, J.; Cordier, J.J.; Durocher, A.; Escourbiac, F.; Ghendrih, Ph.; Guilhem, D.; Gunn, J.; Loarer, T.; Lipa, M.; Mitteau, R.; Pegourie, B.; Reichle, R.; Schlosser, J.; Tsitrone, E.; Vallet, J.C.
2005-01-01
The implementation of actively cooled high heat flux plasma facing components (PFCs) is one of the major ingredients required for operating the Tore Supra tokamak with very long pulses. A pioneering activity has been developed in this field from the very beginning of the device operation that is today culminating with the routine operation of an actively cooled toroidal pumped limiter (TPL) capable to sustain up to 10 MW/m 2 of nominal convected heat flux. Technical information is drawn from the whole development up to the industrialisation and focuses on a number of critical issues, such as bonding technology analysis, manufacture processes, repair processes, destructive and non-destructive testing. The actual experience in Tore Supra allows to address the question of D retention on carbon walls. Redeposition on surfaces without plasma flux is suspected to cause the final 'burial' of about half of the injected gas during long discharges
First results of the Tore Supra ITER like ICRF antenna prototype
International Nuclear Information System (INIS)
Vulliez, K.; Bosia, G.; Bremond, S.; Agarici, G.; Beaumont, B.; Lombard, G.; Millon, L.; Mollard, P.; Volpe, D.
2005-01-01
The project of an ITER-like (IL) ion cyclotron (IC) prototype antenna was initiated in mid 2002 in Cadarache, to assess the operational characteristics of the IL scheme in a Tore Supra (TS)-sized array. The prototype was developed by modifying an existing Tore Supra resonant double loop (RDL) antenna. This strategy, chosen to reduce cost and manufacturing time, allowed the completion of the array construction at the end of 2003. The array was installed on TS in January 2004, at the beginning of the new experimental campaign. After a few comments on the design, the paper reports results on low-power characterisation, high-power commissioning and preliminary tests on TS plasmas, prior to the array dis-assembly for inspection
Development and calibration of the fast neutral particle analyzer of the Tore Supra tokamak
International Nuclear Information System (INIS)
Siri, B.
1989-10-01
The design and construction of an analyzer for the Tore Supra tokamak fast neutral particles are presented. The energy analysis of the hydrogen and deuterium fast neutrals from the plasma allows the obtention of the plasma ionic temperature. The principle of the analysis is described. The analysis maximal energy is 300 keV for the protons and 150 keV for the deuterons. The measurement of the flow of neutrals in a given energy gap requires the knowledge of the energy of analysis, energy resolution and efficiency of the analyzer. The determination of these parameters needed the utilization of a neutral particle beam of 0 to 50 KeV energy. The energy spectra of the neutrals and the plasma ionic temperature at Tore Supra were obtained [fr
Carbon source from the toroidal pumped limiter during long discharge operation in Tore Supra
International Nuclear Information System (INIS)
Dufour, E.; Brosset, C.; Lowry, C.; Bucalossi, J.; Chappuis, P.; Corre, Y.; Desgranges, C.; Guirlet, R.; Gunn, J.; Loarer, T.; Mitteau, R.; Monier-Garbet, P.; Pegourie, B.; Reichle, R.; Thomas, P.; Tsitrone, E.; Hogan, J.; Roubin, P.; Martin, C.; Arnas, C.
2005-01-01
A better understanding of deuterium retention mechanisms requires the knowledge of carbon sources in Tore-Supra. The main source of carbon in the vacuum vessel during long discharges is the toroidal pumped limiter (TPL). This work is devoted to the experimental characterisation of the carbon source from the TPL surface during long discharges using a visible spectroscopy diagnostic. Moreover, we present an attempt to perform a carbon balance over a typical campaign and we discuss it with regards to the deuterium in-vessel inventory deduced from particle balance and the deuterium content of the deposited layers. The study shows that only a third of the estimated deuterium trapped in the vessel is trapped in the carbon deposits. Thus, in the present state of our knowledge and characterisation of the permanent retention, one has to search for mechanisms other than co-deposition to explain the deuterium retention in Tore Supra. (A.C.)
MHD limits in non-inductive tokamak plasmas: simulations and comparison to experiments on Tore Supra
International Nuclear Information System (INIS)
Maget, P.; Huysmans, G.; Ottaviani, M.; Garbet, X.; Moreau, Ph.; Segui, J.-L.; Luetjens, H.
2008-01-01
Non-inductive tokamak discharges with a flat or hollow current profile are prone to the triggering of large tearing modes when the minimum of the safety factor is just below a low order rational. This issue is of particular importance for discussing the optimal safety factor for MHD modes avoidance in Steady-State reactor plasmas. Different non-linear regimes of such magnetic configurations in Tore Supra are studied using the full MHD code XTOR. Numerical simulations show that the non-linear stage of the Double-Tearing Mode (DTM) is governed by the full reconnection model, but a single tearing mode in a low magnetic shear configuration can have a similar impact on the confinement. The different regimes observed experimentally are recovered in the simulations: a small amplitude (2,1) DTM for close resonant surfaces as seen in Tore Supra, a sawtooth-like behaviour of the (2,1) Double-Tearing Mode as first seen in TFTR, or a large amplitude (2,1) tearing mode that severely degrades the energy confinement, as reported in Tore Supra, JET or DIII-D. Situations where q min ≅1.5 with a stable n = 1 mode, as seen in Tore Supra longest discharges, seem to put specific constraints on the MHD model that is used. Indeed, curvature stabilisation without transport terms as could explain linear stability, but such effect vanishes in presence of heat transport. Electron diamagnetic rotation effect is investigated as a possible mechanism for n = 1 mode stabilization.
The response of the Tore Supra edge plasma to supersonic pulsed gas injection
Czech Academy of Sciences Publication Activity Database
Pánek, Radomír; Gunn, J. P.; Bucalossi, J.; Ďuran, Ivan; Geraud, A.; Hron, Martin; Loarer, T.; Pégourié, B.; Stöckel, Jan; Tsitrone, E.
337-339, č. 16 (2005), s. 530-534 ISSN 0022-3115. [Plasma Surface Interactions /16./. Portland, 24.5.2005-28.5.2005] R&D Projects: GA ČR(CZ) GP202/03/P062 Institutional research plan: CEZ:AV0Z20430508 Keywords : Edge plasma * Gas injection and fuelling * probes * Plasma flow * Tore Supra Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.414, year: 2005
A long-period analog integrator for magnetic measurements in Tore Supra
International Nuclear Information System (INIS)
Prou, M.; Barth, E.; Couturier, P.; Ouvrier-Buffet, P.
1998-01-01
A new analog integrator, called 'Integrateur 2000', has been developed for precise integration over long periods for the magnetic signals of Tore Supra with the aim of 1000 s discharges for the CIEL project. This new integrator is already in routine use for the present pulse lengths of up to 200 s in T-S, and tests have been carried out up to 1000 s with less than 2 mV of drift. (author)
Towards high-power long-pulse operation on Tore Supra
International Nuclear Information System (INIS)
Becoulet, A.
1999-01-01
The present paper deals with the experimental and modelling activity linked to the preparation of the long-pulse high-power discharges using the present Tore Supra equipment: heating and current drive scenarios, power coupling, confinement and transport studies, discharge control,... An overview of the results obtained in that field is presented, as well as the progress required in the coming years, and the expected performance, for the CIEL phase, in terms of current drive and confinement
Experimental results of Tore Supra neutral beam injector in the line testing system
International Nuclear Information System (INIS)
Fumelli, M.; Jequier, F.
1991-04-01
Results of the tests carried out on one of the six Tore Supra neutral beam injectors are reported. Several minor modifications of the injector design allowed us to operate up to 92 keV - 30 A beams limited by the high voltage power supplies. Results of studies on different topics like new titanium pumping system, neutron yield from neutraliser and target, beam conditioning and breakdown statistical analysis are also reported [fr
ICRF plasma production in Tore Supra: analysis of antenna coupling and plasma properties
International Nuclear Information System (INIS)
Beaumont, B.; Becoulet, A.; Lyssoivan, A.
1999-01-01
A study of RF plasma production frequency range ω. 2ω ci has been undertaken on Tore Supra taking into account antenna coupling predictions of theory and the TEXTOR-94 database. Two scenarios for RF discharges have been tested (fixed frequency of the RF generator): operation with pure toroidal magnetic field, at standard and lower B T and operation in the magnetic configuration with a small vertical (B V ) field superimposed on B T (B V T ). (authors)
Energy Technology Data Exchange (ETDEWEB)
Lennholm, M; Bouquey, F; Chantant, M; Chappuis, P; Clary, J; Darbos, C; Doceul, L; Faisse, F; Jung, M; Lambert, R; Magne, R; Montecot, A; Poli, S; Roux, D; Samaille, F; Traisnel, E; Villedieu, E [Association Euratom-CEA, DSM/DRFC, CEA/Cadarache, 13108 St. Paul-lez-Durance (France)
2005-01-01
The long pulse capability of Tore Supra and its ECRH system makes it an ideal machine to prove steady state feedback control as required in ITER. Although Neoclassical Tearing Modes (NTMs) have not yet been observed on Tore Supra, the control of other MHD modes represents a very similar task from a control point of view and the stabilisation of such modes for long periods using ECRH will provide essential experience for the implementation of such control schemes on ITER. For this work to progress on Tore Supra, it must be possible to vary the injection angles in real time under feedback control from measured plasma parameters. At Tore Supra the front mirror position - and hence the injection angles - is adjusted using stepper motors controlled through a serial link. The use of a serial link limiting the sampling time for the control system to 50-100 ms and the dynamic response of the stepper motors results in a system frequency response <5 Hz. For following the evolution of the current profile this seems fully acceptable though it could prove somewhat slow for reacting to fast beta changes. In any case the time constants typically associated with growth rate of NTMs on ITER would not require a significantly faster system. Initial commissioning of such real time control was performed in 2004. Unfortunately, following a limited number of cycles and prior to using the system for plasma experiments, one water bellows in the antenna ruptured indicating a major weakness in the design of the water-cooling system for the antenna. As a consequence the water-cooling of the mobile mirror has been redesigned. Careful calculations and subsequent tests have been used to optimise the trajectories of the flexible water connections and a more robust layout is being implemented, ready for operation in the summer 2005.
The Tore Supra control, computer system : six years of operation and improvements
International Nuclear Information System (INIS)
Journeaux, J.Y.; Badie, O.; Chatelier, E.; Hennion, F.; Lebourg, P.; Leveque, P.; Hernandez, M.; Moulin, D.
1995-01-01
The Tore Supra control computer system has been providing a good operation of the Tore Supra machine for six years. It controls all of the sub-systems, the continuous ones as well as the sequential ones, and the automatic operation is very efficient. The control system has been programmed by the users themselves thanks to its user-friendly qualities, in order to keep the full control and knowledge of the automatisms. Nevertheless, some improvements are now necessary. Their main principles are : to choose ergonomic and powerful tools, industrial standards, and to keep the users's participation. The whole control system will be upgraded : the automatism level as well as the display level and the communication networks. The operator's driving job is analysed as supervisory and diagnostic tasks which have an effect on the Tore Supra machine efficiency. So a very powerful driving software has been chosen and linked with an expert system, which is to be designed and implemented with the aim to give an immediate accurate and global understanding of the process and situations, in particular in case of trouble. The method is based on an artificial intelligence approach, and it exploits both the process' informations and automatisms' steps, to determine the process state, next possible states and diagnosis of the process troubles. (orig.)
International Nuclear Information System (INIS)
Barbuti, A.; Gil, C.; Pastor, P.; Spuig, P.; Vincent, B.; Volpe, D.
2013-06-01
The Tore Supra tokamak real-time plasma control is based on measurements coming from various diagnostics. The complexity of all the events that occur during plasma is at the origin of measurements disturbances which have to be corrected in real time in order to ensure an optimal control. The signal correction does not just mean processing but requires complex algorithms. Electronics does not only need to process and adapt electrical signals, but it has to include corrections by mathematical calculation. The FPGA (field-programmable gate array) technology, with the help of basic adapted electronics, allows integrating the entire real time calculation and digital data transmission on the network. FMC (FPGA Mezzanine Card) coupled with in-house motherboard, which is used both as the interface with Tore Supra specific systems and as the support for other signals processing options, is the perfect answer to this request. The FMC includes a FPGA, memory, Ethernet port and multiple I/O for interfacing with the motherboard and Tore Supra signals. The algorithms are developed in VHDL (Very high speed integrated circuit Hardware Description Language), parallel process management that promotes faster calculation than a common μC (Micro-controller) in one clock pulse. The flexibility, the low cost and the implementation speed allow fitting a large number of various applications in fields where no 'off-theshelf' component can be found. And more specifically, in research and experimentation, algorithms can be continuously improved or modified for new requirements. (authors)
Numerical modelling of pump limiter biasing on TEXTOR-94 and Tore Supra
International Nuclear Information System (INIS)
Gerhauser, H.; Claassen, H.A.; Mank, G.; Zagorski, R.; Loarer, T.; Gunn, J.; Boucher, C.
2002-01-01
The two-dimensional multifluid code TECXY has been used to model the biasing (with respect to the first wall) of the toroidal belt limiter ALT-II on the tokamak TEXTOR-94 and of the new toroidal pump limiter being installed on Tore Supra tokamak in the framework of the CIEL project. It is well known that the edge flow pattern can be influenced by the poloidal electric drifts from imposing radial electric fields. The modelling with TECXY introduces imprinted bias currents in the scrape-off layer (SOL) for the case of negative (limiter) biasing, and imprinted bias potentials for the case of positive biasing. This allowed us to simulate sufficiently well the experimental I-V characteristics for either biasing of ALT-II and also reproduced the essential features and trends of the observed plasma profiles in the SOL of TEXTOR-94. For negative biasing a moderate improvement of the pumping exhaust efficiency can be achieved in the case of TEXTOR. For Tore Supra, however, only a negligible improvement of the limiter performance with biasing can be predicted, which is explained by the relatively weak drift flows in Tore Supra. (author)
Engineering studies for the installation of an axi-symmetric metallic divertor in Tore Supra
International Nuclear Information System (INIS)
Doceul, L.; Portafaix, C.; Bucalossi, J.; Saille, A.; Bertrand, B.; Lipa, M.; Missirlian, M.; Jiolat, G.; Samaille, F.; Soler, B.
2011-01-01
Tore Supra (TS) has been designed to operate using technologies that allow long plasma operation (a few minutes), by means of superconducting magnets and actively-cooled high heat flux plasma facing components (PFCs). Actively cooled tungsten PFC will be used in the baffle area of the first ITER divertor. In order to validate such a technology fully (industrial manufacturing, operation with long plasma duration), the implementation of a tungsten axi-symmetric divertor in the tokamak Tore Supra has been studied . With this second major upgrade, Tore Supra should be able to address the problematic of long plasma discharges with a metallic divertor. The proposed divertor is made up of two stainless steel casings containing a copper coil winding located at the top and bottom area of the vacuum vessel. These casings are firmly maintained by connection beams and protected by PFC. This paper describes the mechanical design of this major component and its integration in TS, the associated electromagnetic and thermomechanical analysis, the manufacturing issues and finally the integration of ITER representative PFCs.
The data acquisition and interlock system for Tore Supra infrared imaging
International Nuclear Information System (INIS)
Moulin, D.; Balorin, C.; Buravand, Y.; Caulier, G.; Ducobu, L.; Guilhem, D.; Jouve, M.; Roche, H.
2003-01-01
The data acquisition for the infrared measurement system on Tore-Supra is a key element in ensuring the supervision of the new actively-cooled plasma facing components of the CIEL project. It will allow us to follow the thermal evolution of components of Tore-Supra, in particular the toroidal pumped limiter (LPT) (360 deg.-15 m long) and the five additional heating launchers. When fully installed, the infrared measurement system will be composed of 12 digital 16-bit infrared cameras. They cover a 100-1200 deg.C temperature range and each picture has a definition of 320x240 pixels with a 20 ms time resolution. The objectives of the data acquisition system is real-time recording and analysis of each view element for further post-pulse analysis in order to understand the physics phenomenon and ensure the supervision of the plasma facing components and also to be part of the global feedback control system of Tore Supra
Articulated inspection arm for ITER, a demonstration in the Tore Supra tokamak
International Nuclear Information System (INIS)
Cordier, J.J.; Gargiulo, L.; Grisolia, C.; Samaille, F.; Palmer, J.D.
2003-01-01
The aim of this program is to demonstrate for ITER the feasibility of an in-vessel remote handling inspection using a long reach, limited payload carrier (1 to 10 kg) for penetration of the ITER chamber through the openings. This device is dedicated to close inspection of the Plasma Facing Components (PFC). An articulated demonstrator called articulated inspection arm (AIA) has been manufactured. A feasibility study of a full AIA operation in Tore Supra was performed, taking into account ITER reference requirements. A scale one demonstration of the AIA under ITER relevant condition is feasible on Tore Supra and would give significant improvement in research results for ITER remote Handling equipment. The test of the AIA demonstrator behaviour is foreseen in 2005 in real Tokamak conditions. The paper presents the full robot concept, the results of the first test campaign, the AIA new design and its integration on Tore Supra. Several potential uses of the AIA for the in vessel components inspection are being studied such as PFC visual inspection, water loop leak testing, laser ablation for wall detritiation and carbon dust and flakes removal are foreseen as utilities to be placed at the AIA head. These various systems are described in the paper
Articulated inspection arm for ITER, a demonstration in the Tore Supra tokamak
Energy Technology Data Exchange (ETDEWEB)
Cordier, J.J.; Gargiulo, L.; Grisolia, C.; Samaille, F. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Friconneau, J.P.; Perrot, Y. [CEA Fontenay-aux-Roses, LIST Robotics and Interactive Systems Unit, 92 (France); Palmer, J.D. [Max-Planck-Institut fuer Plasmaphysik Boltzmannstr.2, Garching (Germany)
2003-07-01
The aim of this program is to demonstrate for ITER the feasibility of an in-vessel remote handling inspection using a long reach, limited payload carrier (1 to 10 kg) for penetration of the ITER chamber through the openings. This device is dedicated to close inspection of the Plasma Facing Components (PFC). An articulated demonstrator called articulated inspection arm (AIA) has been manufactured. A feasibility study of a full AIA operation in Tore Supra was performed, taking into account ITER reference requirements. A scale one demonstration of the AIA under ITER relevant condition is feasible on Tore Supra and would give significant improvement in research results for ITER remote Handling equipment. The test of the AIA demonstrator behaviour is foreseen in 2005 in real Tokamak conditions. The paper presents the full robot concept, the results of the first test campaign, the AIA new design and its integration on Tore Supra. Several potential uses of the AIA for the in vessel components inspection are being studied such as PFC visual inspection, water loop leak testing, laser ablation for wall detritiation and carbon dust and flakes removal are foreseen as utilities to be placed at the AIA head. These various systems are described in the paper.
Poloidal asymmetries of flows in the Tore Supra tokamak
Vermare, L.; Hennequin, P.; Gürcan, Ö. D.; Garbet, X.; Honoré, C.; Clairet, F.; Giacalone, J. C.; Morel, P.; Storelli, A.; Tore Supra Team
2018-02-01
Simultaneous measurements of binormal velocity of density fluctuations using two separate Doppler backscattering systems at the low field side and at the top of the plasma show significant poloidal asymmetry. The measurements are performed in the core region between the radii 0.7 Supra tokamak. A possible generation mechanism by the ballooned structure of the underlying turbulence, in the form of convective cells, is proposed for explaining the observation of these poloidally asymmetric mean flows.
Energy Technology Data Exchange (ETDEWEB)
Wisniewski, S
2001-11-01
This report presents the implementation of the ion cyclotron resonance heating system (FCI) to the instrumentation and control system of the Tore-Supra tokamak. The new plasma heating system involves 3 antennas delivering 12 MW that are required to maintain fusion reactions. This paper is divided into 8 chapters: 1) thermonuclear fusion and Tore-Supra tokamak; 2) hardware system around Tore-Supra, in this chapter the control system and the data acquisition and processing systems are presented; 3) functional analysis, this analysis defines the different needs concerning timing and pilot-controlling, a preliminary proposition of hardware equipment is made; 4) operating modes of FCI; 5) communication within the control system network; 6) communication with the supervisory system of the power stations; 7) management of data exchange with SMX generators; and 8) control of the rate of stationary waves during the injection of power into the plasma.
Energy Technology Data Exchange (ETDEWEB)
Harauchamps, E
2004-07-01
This work presents analytical solutions to the electron heat transport equation involving a damping term and a convection term in a cylindrical geometry. These solutions, processed by Matlab, allow the determination of the evolution of the radial profile of electron temperature in tokamaks during heating. The modulated injection of waves around the electron cyclotron frequency is an efficient tool to study heat transport experimentally in tokamaks. The comparison of these analytical solutions with experimental results from Tore-Supra during 2 discharges (30550 and 31165) shows the presence of a sudden change for the diffusion and damping coefficients. The hypothesis of the presence of a pinch spread all along the plasma might explain the shape of the experimental temperature profiles. These analytical solutions could be used to determine the time evolution of plasma density as well or of any parameter whose evolution is governed by a diffusion-convection equation. (A.C.)
International Nuclear Information System (INIS)
Reichle, R; Desgranges, C; Faisse, F; Pocheau, C; Lasserre, J-P; Oelhoffen, F; Eupherte, L; Todeschini, M
2009-01-01
Tore Supra has-like ITER-reflecting internal surfaces, which can perturb the machine protection systems based on infrared (IR) thermography. To ameliorate this situation, we have measured and modelled in the 3-5 μm wavelength range the bi-directional reflection distribution function (BRDF) of wall material samples from Tore Supra and conducted in situ reflection measurements and simulated them with the CEA COSMOS code. BRDF results are presented for B 4 C and carbon fibre composite (CFC) tiles. The hemispherical integrated reflection ranges from 0.12 for the B 4 C sample to 0.39 for a CFC tile from the limiter erosion zone. In situ measurements of the IR reflection of a blackbody source off an ICRH and an LHCD antenna of Tore Supra are well reproduced by the simulation.
International Nuclear Information System (INIS)
Agarici, G.; Beaumont, B.; Bibet, Ph.; Bremond, S.; Bucalossi, J.; Colas, L.; Durocher, A.; Gargiulo, L.; Ladurelle, L.; Lombard, G.; Martin, G.; Mollard, P.
2000-01-01
During the 1997 and 1998 Tore Supra shutdown, a first set of new antenna guard limiters was installed on one of the three ion cyclotron resonance heating (ICRH) antennas of Tore Supra. This limiter, which was one of the main technological studies of the 1998 campaign, was widely experimented in real plasma conditions, thus allowing the validation in situ, for the first time, of the technology of active metal casting (AMC) for plasma facing components. The huge improvement in the thermal response of the new limiter generation, compared to the old one, is shown on plasma pulses made identical in terms of antenna position and injected RF power profile. By using the infrared cameras installed inside Tore Supra and viewing the antennas front, the power density fluxes received by the carbon fibre composite (CFC) surface of the limiter were evaluated by correlation with the heat load tests made on the electrons beam facility of CEA/Framatome
Cybele: a large size ion source of module construction for Tore-Supra injector
International Nuclear Information System (INIS)
Simonin, A.; Garibaldi, P.
2005-01-01
A 70 keV 40 A hydrogen beam injector has been developed at Cadarache for plasma diagnostic purpose (MSE diagnostic and Charge exchange) on the Tore-Supra Tokamak. This injector daily operates with a large size ions source (called Pagoda) which does not completely fulfill all the requirements necessary for the present experiment. As a consequence, the development of a new ion source (called Cybele) has been underway whose objective is to meet high proton rate (>80%), current density of 160 mA/cm 2 within 5% of uniformity on the whole extraction surface for long shot operation (from 1 to 100 s). Moreover, the main particularity of Cybele is the module construction concept: it is composed of five source modules vertically juxtaposed, with a special orientation which fits the curved extraction surface of the injector; this curvature ensures a geometrical focalization of the neutral beam 7 m downstream in the Tore-Supra chamber. Cybele will be tested first in positive ion production for the Tore-Supra injector, and afterward in negative ion production mode; its modular concept could be advantageous to ensure plasma uniformity on the large extraction surface (about 1 m 2 ) of the ITER neutral beam injector. A module prototype (called the Drift Source) has already been developed in the past and optimized in the laboratory both for positive and negative ion production, where it has met the ITER ion source requirements in terms of D-current density (200 A/m 2 ), source pressure (0.3 Pa), uniformity and arc efficiency (0.015 A D-/kW). (authors)
Tore-Supra infrared thermography system, a real steady-state diagnostic
International Nuclear Information System (INIS)
Guilhem, D.; Bondil, J.L.; Bertrand, B.; Desgranges, C.; Lipa, M.; Messina, P.; Missirlian, M.; Portafaix, C.; Reichle, R.; Roche, H.; Saille, A.
2005-01-01
Tore-Supra Tokamak (I p = 1.5 MA, B t = 4 T) has been constructed with a steady-state magnetic field using super-conducting magnets and water-cooled plasma facing components (PFCs) for high-performance long pulse plasma discharges. When not actively cooled, plasma facing components can only accumulate a limited amount of energy since the temperature increases continuously during the discharge until radiation cooling equals the incoming heat flux. Such an environment is found in the JET Tokamak [JET Team, IAEA-CN-60/A1-3, Seville, 1994] and on TRIAM [M. Sakamoto, H. Nakashima, S. Kawasaki, A. Iyomasa, S.V. Kulkarni, M. Hasegawa, E. Jotaki, H. Zushi, K. Nakamura, K. Hanada, S. Itoh, Static and dynamic properties of wall recycling in TRIAM-1M, J. Nucl. Mater. 313-316 (2003) 519-523] [Y. Kamada, et al., Nucl. Fusion 3 (1999) 1845]. In Tore-Supra, the surface temperature of the actively cooled plasma facing components reach steady state within a second. We present here the Tore-Supra thermographic system, made of seven endoscope bodies equipped so far with eight infrared (IR) cameras. It has to be noted that this diagnostic is the first diagnostic to be actively cooled, as required for steady state. The main purpose of such a diagnostic is to prevent the plasma to damage the actively cooled plasma facing components (ACPFCs), which consist of the toroidal pumped limiter (TPL), 7 m 2 , and of five radio-frequency antennae, 1.5 m 2 each
Ion temperature measurements in the scrape-off layer of the Tore Supra Tokamak
International Nuclear Information System (INIS)
Kocan, M.
2009-10-01
The thesis describes measurements of the scrape-off layer (SOL) ion temperature T i with a retarding field analyzer (RFA) in the limiter tokamak Tore Supra. Considerable emphasis is placed on study of the instrumental effects of RFAs and their influence on T i measurements. In general, the influence of instrumental effects on T i measurements is found to be relatively small. The instrumental study is followed by systematic measurements of T i (as well as other parameters) in the Tore Supra SOL. This includes the scaling of SOL temperatures and electron density with the main plasma parameters (such as the plasma density, toroidal magnetic field, working gas, and the radiated power fraction). Except at very high densities or in detached plasmas, SOL T i is found to be higher than T e by up to a factor of 7. While SOL T i is found to vary by almost two orders of magnitude, following the variation of the core temperatures, SOL T e changes only little and seems to be decoupled from the core plasma. The first continuous T i /T e profile from the edge of the confined plasma into the SOL is constructed using data from different tokamaks. It is shown that T i /T e > 1 in the SOL but also in the confined plasma, and increases with radius. The first evidence of poloidal asymmetry of the radial ion and electron energy transport in the SOL is reported. Implications for ITER start-up phase are discussed. Correlation of the asymmetries of SOL T i and T e measured from both directions along the magnetic field lines with changes of the parallel Mach number is studied. SOL T i was measured for the first time in Tore Supra by charge exchange recombination spectroscopy (CXRS) and compared to RFA data. A factor of 4 higher T i measured by CXRS is a subject of further analysis. (A.C.)
Copper alloy-stainless steel bonds and recent developments for Tore Supra
International Nuclear Information System (INIS)
Lipa, M.; Chappuis, Ph.; Mitteau, R.; Reindl, G.
1998-01-01
High strength high conductivity copper alloys such as CuCrZr are used in Tore Supra as structural heat sink material for high heat flux plasma facing components. Although friction welded pipes on these components have shown a satisfactory in-service reliability, it came out that recently produced CuCrZr-stainless steel bonds showed very poor results in ductility. This led to a more detailed investigation of friction weldments. Finally, a more ductile joint has been developed with 'Plansee AG' on the basis of electron beam welded nickel adapters inserted between the two materials. Characterisation of such bonds is reported. (author)
Controlled irradiation of CFC samples in the scrape-off layer of Tore Supra
Energy Technology Data Exchange (ETDEWEB)
Gunn, J.P. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France)]. E-mail: jamie.gunn@cea.fr; Begrambekov, L. [Moscow Engineering and Physics Institute, 115409 Moscow (Russian Federation); Brosset, C. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France); Gordeev, A. [Moscow Engineering and Physics Institute, 115409 Moscow (Russian Federation); Loarer, T. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France); Miljavina, E. [Moscow Engineering and Physics Institute, 115409 Moscow (Russian Federation); Shigin, P. [Moscow Engineering and Physics Institute, 115409 Moscow (Russian Federation); Khodja, H. [Laboratoire Pierre Suee, CEA/CNRS, CEA Saclay, 91191 Gif sur Yvette (France); Oddon, P. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France); Pascal, J.-Y. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France); Vartanian, S. [DRFC, Bat. 508, Association Euratom - CEA, CEA/DSM/DRFC, Centre de Cadarache, 13108 Saint Paul Lez Durance (France)
2005-03-01
The first experiments with a mobile sample holder in Tore Supra are described. It exposes 10 CFC samples to direct irradiation by the scrape-off layer plasma. The plasma parameters are measured simultaneously by two Langmuir probes, and the temperature of the samples by embedded thermocouples. The cumulated irradiation dose during the first brief campaign was enough to exceed the classical saturation of the ion stopping zone, as verified by thermodesorption spectroscopy and nuclear reaction analysis. Scanning electron microscopy of some of the samples was performed before and after irradiation in order to investigate the evolution of the surface structure due to ion bombardment.
Synergy between electron cyclotron and lower hybrid current drive on Tore Supra
International Nuclear Information System (INIS)
Giruzzi, G.; Artaud, J.F.; Dumont, R.J.; Imbeaux, F.; Bibet, P.; Berger-By, G.; Bouquey, F.; Clary, J.; Darbos, C.; Ekedahl, A.; Hoang, G.T.; Lennholm, M.; Maget, P.; Magne, R.; Segui, J.L.; Bruschi, A.; Granucci, G.
2005-01-01
Improvement (up to a factor ∼ 4) of the electron cyclotron (EC) current drive efficiency in plasmas sustained by lower hybrid (LH) current drive has been demonstrated in stationary conditions on the Tore Supra tokamak. This was made possible by feedback controlled discharges at zero loop voltage, constant plasma current and density. This effect, predicted by kinetic theory, results from a favorable interplay of the velocity space diffusions induced by the two waves: the EC wave pulling low-energy electrons out of the Maxwellian bulk, and the LH wave driving them to high parallel velocities. (author)
Analytical and numerical studies of sawtooth stabilization with on-axis ICRH on Tore Supra
International Nuclear Information System (INIS)
Zabiego, M.; Basiuk, V.; Becoulet, A.; Garbet, X.; Saoutic, B.; White, R.B.; Wu, Y.
1995-01-01
Sawtooth stabilization has recently been achieved with on-axis ICRH on Tore Supra. Analytic and numerical tools have been developed that allow analysis of these data, with the emphasis on the energetic-particle contribution. The latter is calculated on the basis of an original expression for the hot-ion distribution function, mostly-passing, deduced from theoretical and experimental ICRH studies, and compared to the usual mostly-trapped model. Both models account for stabilization, but for different reasons: with the mostly-passing distribution, stabilization is essentially driven by barely-passing hot ions. (author) 9 refs.; 2 figs
International Nuclear Information System (INIS)
Moreau, F.
1996-01-01
In the Tokamak TORE-SUPRA, the plasma facing components absorbs and evacuate (active cooling) high power fluxes (up to 10 MW/m 2 ). Their thermal behavior study is essential for the success of controlled thermonuclear fusion line. The first part is devoted to the study of power deposition on the TORE-SUPRA actively cooled limiters. A model of power deposition on one of the limiters is developed. It Takes into account the magnetic topology and a description of the plasma edge. The model is validated with experimental calorimetric data obtained during a series of shots. This will allow to compare the surface temperature measurements with the predicted ones. The main purpose of this thesis was to evaluate and develop a new surface temperature measurement system. It works in the near infrared range (890 nm) and is designed to complete the existing thermographic diagnostic of TORE-SUPRA. By using the radiation laws (for a blackbody and the plasma) ant the laboratory calibration one can estimate the surface temperature of the observed object. We evaluate the performances and limits of such a device in the harsh conditions encountered in a Tokamak environment. On the one hand, in a quasi ideal situation, this analysis shows that the range of measurement is 600 deg. C to 2500 deg. C. On the other hand, when one takes into account of the plasma radiation (with an averaged central plasma density of 6.10 19 m -3 ), we find that the minimum surface temperature rise to 900 deg. C. In the near future, according to the development of IR-CCD cameras working in the near infrared range up to 2 micrometers, we will be able to keep the good spatial resolution with an improved lower limit for the temperature down to 150 deg. C. The last section deals with a number of computer tools to process the images obtained from experiments on TORE-SUPRA. A pattern recognition application was especially developed to detect a complex plasma iso-intensity structure. (author)
Rapid global response of the electron temperature during pellet injection on Tore Supra
International Nuclear Information System (INIS)
Talvard, M.
1993-06-01
During pellet injection in the Tore Supra tokamak, a very quick electron temperature drop in the whole plasma column has been observed by means of a fast acquisition ECE Fabry-Perot interferometers system. The time delay of the temperature drop between plasma edge and center is less than 20 microseconds, corresponding to a propagation velocity of the order of 25 km/s, much larger than both the pellet velocity and the ordinary diffusion velocity. A model of neutral atom diffusion, in which charge-exchange process plays a key role, is proposed to explain such phenomena
Thermal electron transport in regimes with low and negative magnetic shear in Tore Supra
International Nuclear Information System (INIS)
Voitsekhovitch, I.; Litaudon, X.; Moreau, D.; Aniel, T.; Becoulet, A.; Erba, M.; Joffrin, E.; Kazarian-Vibert, F.; Peysson, Y.
1997-01-01
The magnetic shear effect on thermal electron transport is studied in a large variety of non-inductive plasmas in Tore Supra. An improved confinement in the region of low and negative shear was observed and quantified with an exponential dependence on the magnetic shear (Litaudon, et al., Fusion Energy 1996 (Proc. 16th Int. Conf. Montreal, 1996), Vol. 1, IAEA, Vienna (1997) 669). This is interpreted as a consequence of a decoupling of the global modes (Romanelli and Zonca, Phys. Fluids B 5 (1993) 4081) that are thought to be responsible for anomalous transport. This dependence is proposed in order to complete the Bohm-like L mode local electron thermal diffusivity so as to describe the transition from Bohm-like to gyroBohm transport in the plasma core. The good agreement between the predictive simulations of the different Tore Supra regimes (hot core lower hybrid enhanced performance, reversed shear plasmas and combined lower hybrid current drive and fast wave electron heating) and experimental data provides a basis for extrapolation of this magnetic shear dependence in the local transport coefficients to future machines. As an example, a scenario for non-inductive current profile optimization and control in ITER is presented. (author)
International Nuclear Information System (INIS)
Duchateau, J.L.; Gravil, B.; Tena, E.; Henry, D.; Journeaux, J.Y.; Libeyre, P.
2004-01-01
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)
International Nuclear Information System (INIS)
Artaud, J.F.; Giruzzi, G.; Dumont, R.J.; Imbeaux, F.; Bibet, P.; Bouquey, F.; Clary, J.; Ekedahl, A.; Hoang, G.T.; Lennholm, M.; Magne, R.; Segui, J.L.
2004-01-01
Non-inductive current drive (CD) has two main applications in tokamaks: sustainment of a substantial fraction of the toroidal plasma current necessary for the plasma confinement and control of the plasma stability and transport properties by appropriate shaping of the current density profile. For the first kind of applications, lower hybrid (LH) waves are known to provide the highest efficiency (defined as the ratio of the driven current to the injected wave power), although with limited control capability. Conversely, electron cyclotron (EC) waves drive highly localized currents, and are therefore particularly suited for control purposes, but their CD efficiency is much lower than that of LH waves (typically, an order of magnitude in present day experiments). Various calculations have demonstrated an interesting property: the current driven by the simultaneous use of the two waves, I(LH+EC), can be significantly larger than the sum I(LH)+I(EC) of the currents separately driven by the two waves in the same plasma conditions. This property, called synergy effect. The peculiar experimental conditions attainable on the Tore Supra tokamak have allowed the first experimental demonstration of the synergy between EC and LH current drive. The significant improvement of the electron cyclotron current drive (ECCD) efficiency in the presence of low hybrid current drive (LHCD), predicted by kinetic theory and confirmed by stationary experiments on Tore Supra, opens up the possibility of using ECCD as an efficient current profile control tool in LHCD plasmas
Study of plasma turbulence by ultrafast sweeping reflectometry on the Tore Supra Tokamak
International Nuclear Information System (INIS)
Hornung, Gregoire
2013-01-01
The performance of a fusion reactor is closely related to the turbulence present in the plasma. The latter is responsible for anomalous transport of heat and particles that degrades the confinement. The measure and characterization of turbulence in tokamak plasma is therefore essential to the understanding and control of this phenomenon. Among the available diagnostics, the sweeping reflectometer installed on Tore Supra allows to access the plasma density fluctuations from the edge to the centre of the plasma discharge with a fine spatial (mm) and temporal resolution (μs), that is of the order of the characteristic turbulence scales.This thesis consisted in the characterization of plasma turbulence in Tore Supra by ultrafast sweeping reflectometry measurements. Correlation analyses are used to quantify the spatial and temporal scales of turbulence as well as their radial velocity. In the first part, the characterization of turbulence properties from the reconstructed plasma density profiles is discussed, in particular through a comparative study with Langmuir probe data. Then, a parametric study is presented, highlighting the effect of collisionality on turbulence, an interpretation of which is proposed in terms of the stabilization of trapped electron turbulence in the confined plasma. Finally, it is shown how additional heating at ion cyclotron frequency produces a significant though local modification of the turbulence in the plasma near the walls, resulting in a strong increase of the structure velocity and a decrease of the correlation time. The supposed effect of rectified potentials generated by the antenna is investigated via numerical simulations. (author) [fr
Near infrared spectra of carbon deposited layers from Tore Supra under plasma particle bombardment
International Nuclear Information System (INIS)
Delchambre, E.; Reichle, R.; Loarer, T.
2003-01-01
The authors present the results of laboratory investigations that show spectral luminance distributions similar to those emitted by plasma facing components in Tore-Supra experiments. The device used to produce plasma impact on the target is an Helicon source, where the gas is ionised with a 13.56 MHz RF generator. Different targets were tested: highly oriented pyrolytic graphite (HOPG) and pyrolytic graphite sampled from the MPL (modular pump limiter) neutralizer covered with flakes (a loosely attached deposited carbon layer). The target, placed in the centre of the vacuum vessel, was positively biased to ensure an electron bombardment only. NIR (near infra-red) spectral luminance deformation phenomena as observed in Tore-Supra, have been reproduced in the laboratory. Additional NIR luminance, with a maximum around 1.3 μm considering T(1.55 μm) as temperature reference, has shown up on the same carbon deposited layer that actually gave rise to the first reports on the phenomenon but not on HOPG. The phenomenon occurs in Ar and in H 2 when the current collected on the target exceeds 20 or 30 mA/cm 2 respectively. The intensity of the effect increases with growing target temperature and seemingly with growing collected current density and it disappears after electron bombardment with a time constant of 0.34 s. It shows some linear behaviour in Arrhenius plot
Thermal electron transport in the regimes with low and negative magnetic shear on tore supra
International Nuclear Information System (INIS)
Voitsekhovitch, I.; Litaudon, X.; Moreau, D.; Aniel, T.; Becoulet, A.; Erba, M.; Joffrin, E.; Kazarian-Vibert, F.; Peysson, Y.
1997-04-01
The magnetic shear effect on the thermal electron transport is studied in a large variety of non-inductive plasmas of Tore Supra. An improved confinement in the region of low and negative shear was observed and quantified with an exponential dependence on the magnetic shear [Litaudon et al. in Plasma Physics and Controlled Nuclear Fusion Research, 1996, Montreal (International Atomic Energy Agency, Vienna, 1997) to be published]. This is interpreted as the consequence of a decoupling of the global modes [Romanelli and Zonka, Phys. Fluids B5 (1993), 4081] which are thought to be responsible for anomalous transport. This dependence is proposed to complete the Bohm-like L-mode local electron thermal diffusivity to describe the transition from the Bohm-like to the gyro-Bohm transport in the plasma core. The good agreement between the predictive simulations of the different Tore Supra regimes (hot core lower hybrid enhanced performance, reversed shear plasmas and combined lower hybrid current drive and fast wave electron heating) and experimental data gives a basis for the extrapolation of this magnetic shear dependence in the local transport coefficients for future machines. As an example a scenario for non-inductive current profile optimisation and control in ITER is presented. (author)
International Nuclear Information System (INIS)
Grosman, A.
2004-01-01
The development, design, manufacture and testing of actively cooled high heat flux plasma facing components (PFC) has been an essential stage towards long powerful tokamak operations for Tore-Supra, it lasted about 10 years. This paper deals with the toroidal pumped limiter (TPL) that is able to sustain up to 10 MW/m 2 of nominal heat flux. This device is based on hardened copper alloy heat sink structures covered by a carbon fiber composite armour, it resulted in the manufacturing of 600 elementary components, called finger elements, to achieve the 7.6 m 2 TPL. This assembly has been operating in Tore-Supra since spring 2002. Some difficulties occurred during the manufacturing phase, the valuable industrial experience is summarized in the section 2. The permanent monitoring of PFC surface temperature all along the discharge is performed by a set of 6 actively cooled infrared endoscopes. The heat flux monitoring and control issue but also the progress made in our understanding of the deuterium retention in long discharges are described in the section 3. (A.C.)
Energy Technology Data Exchange (ETDEWEB)
Grosman, A. [Association Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee
2004-07-01
The development, design, manufacture and testing of actively cooled high heat flux plasma facing components (PFC) has been an essential stage towards long powerful tokamak operations for Tore-Supra, it lasted about 10 years. This paper deals with the toroidal pumped limiter (TPL) that is able to sustain up to 10 MW/m{sup 2} of nominal heat flux. This device is based on hardened copper alloy heat sink structures covered by a carbon fiber composite armour, it resulted in the manufacturing of 600 elementary components, called finger elements, to achieve the 7.6 m{sup 2} TPL. This assembly has been operating in Tore-Supra since spring 2002. Some difficulties occurred during the manufacturing phase, the valuable industrial experience is summarized in the section 2. The permanent monitoring of PFC surface temperature all along the discharge is performed by a set of 6 actively cooled infrared endoscopes. The heat flux monitoring and control issue but also the progress made in our understanding of the deuterium retention in long discharges are described in the section 3. (A.C.)
The control of plasma density profile in Tore Supra. Comparison of different fueling techniques
International Nuclear Information System (INIS)
Commaux, N.
2007-09-01
The behaviour of a reactor-class plasma when fuelled using the existing techniques (gas puffing, supersonic molecular beam injection and pellet injection) is still very difficult to foresee. The present work has been initiated on Tore Supra in order to extrapolate the consequences of the different fuelling systems on ITER. Two main topics have been studied: the comparison of the plasma behaviour when fuelled using the different techniques at high Greenwald density fractions and the study of the homogenization following a pellet injection (main fuelling technique for ITER burning plasmas). The experiments at high Greenwald density fractions performed on Tore Supra showed that the plasma behaviour is very dependent on the fuelling method. The plasma energy confinement is following the scaling laws determined at low density when fuelled using pellet injection. which is better than for gas puffing and SMBI. both inducing a significant confinement loss. This behaviour is nor related to a transport modification: the ratio between effective diffusion and convection is similar to the pellet case. The difference between these shots is related only to the position of the matter source (at the edge for gas and close to the center for pellets). The study concerning the homogenization phenomena following a pellet injection aims mainly to study the ∇B-drift effect that expels the mater deposited by a pellet toward the low field side. A new phenomenon. which appears to be particularly important for the ∇B-drift during low field side injections. was then discovered: the influence of magnetic surfaces with an integer-valued safety factor (q). When the mater drifting toward low field side crosses an integer q surface. it experiences an important braking effect which stops the drift motion. It implies that the pellet material is mainly deposited on the last integer q surface crossed by the pellet during its injection. This study allows also to determine that the
The Tore Supra control, computer system: six years of operation and improvements
International Nuclear Information System (INIS)
Journeaux, J.Y.; Badie, O.; Chatelier, E.; Hennion, F.; Lebourg, P.; Leveque, P.; Hernandez, M.; Moulin, D.
1994-01-01
Some necessary improvements of the Tore Supra control computer system are discussed. Their main principles are: to choose ergonomic and powerful tools, industrial standards, and to keep the users's participation. The whole control system will be upgraded: the automatism level as well as the display level and the communication networks. A very powerful driving software has been chosen and linked with an expert system, which is to be designed and implemented with the aim to give an immediate accurate and global understanding of the process and situations, in particular in case of trouble. The method is based on an artificial intelligence approach, and it exploits both the process' informations and automatism' steps, to determine the process state, next possible states and diagnosis of the process troubles. (author) 3 refs., 2 figs
Measurements of RF-induced sol modifications in Tore Supra tokamak
International Nuclear Information System (INIS)
Kubic, Martin; Gunn, James P.; Colas, Laurent; Heuraux, Stephane; Faudot, Eric
2012-01-01
Since spring 2011, one of the three ion cyclotron resonance heating (ICRH) antennas in the Tore Supra (TS) tokamak is equipped with a new type of Faraday screen (FS). Results from Radio Frequency (RF) simulations of the new Faraday screen suggest the innovative structure with cantilevered bars and 'shark tooth' openings significantly changes the current flow pattern on the front of the antenna which in turn reduces the RF potential and RF electrical field in particular parallel to the magnetic field lines which contributes to generating RF sheaths. Effects of the new FS operation on RF-induced scrape-off layer (SOL) modifications are studied for different plasma and antenna configurations - scans of strap power ratio imbalance, phasing, injected power and SOL density. (authors)
Test model of the fast thyristor circuit breaker, for TORE SUPRA
International Nuclear Information System (INIS)
Bareyt, B.; Leloup, C.; Rijnoudt, E.
1984-01-01
The tokamak TORE SUPRA, permits, owing to the toroidal superconducting coils and to the poloidal field system performances, long discharges (30 s and more), for a plasma current of typically 2 MA. The poloidal field system uses the magnetic energy initially stored, for the ignition and the fast rise of the plasma current, by forcing the primary current to flow through a resistor after breaking the main rectifier current by a fast thyristor circuit breaker. In order to test the technical capabilities of such a breaker system made of fast thyristors, in series and in parallel, after a single thyristor test model T1 the series arrangement was studied on a 24 thyristor test model T2 and the parallel arrangement problems, led the manufacturer CGEE Alsthom, to build a new test model T3. (author)
Real time plasma feedback control: An overview of Tore-Supra achievements
International Nuclear Information System (INIS)
Martin, G.; Bucalossi, J.; Ekedahl, A.; Gil, C.; Grisolia, C.; Guilhem, D.; Gunn, J.; Kazarian, F.; Moulin, D.; Pascal, J.Y.; Saint-Laurent, F.
2001-01-01
Stable and reliable fusion plasma operation requires increasingly advanced control systems. This is especially true for steady-state operation in advanced modes, when several parameters are to be simultaneously optimised: e.g. the current profile, which has been related to the formation of internal transport barrier, and the density, which plays a crucial role both in the fusion power and in the plasma wall interactions. At a more technological level, good management of the power entering and leaving the plasma is required, by efficient additional heating coupling, and with a full control of radiation and convection losses and distribution to the first wall elements. For these goals, several feed-back mechanisms have been developed with success on Tore-Supra, in the past four years. Most of them are based on software, implemented in a set of micro-computers connected through a VME network. (author)
Determination of q during sawtooth from inverse evolution of BAEs in Tore Supra
Amador, C. H. S.; Sabot, R.; Garbet, X.; Guimarães-Filho, Z. O.; Ahn, J.-H.
2018-01-01
Measuring the value of the safety factor (q) in the core during sawtooth cycles is still an open issue. A new method to measure q in Tore Supra plasma core is presented here. It relies on the analysis of the time evolution of a set of MHD modes detected after the sawtooth crashes. These modes are in the frequency range of previously observed Beta-induced Alfvén Eigenmodes, but with a frequency declining in time. The mode frequency analysis shows that the q profile is reversed when we have ICRH, after the sawtooth crash. In high current discharges (I_p>1.15 MA), the q-profile remains reversed for a longer time compared with lower plasma current discharges. Non-linear 3D MHD simulations of sawteeth performed with the XTOR-2F code (Lütjens and Luciani 2010 J. Comput. Phys. 229 8130-43) exhibit features that are similar to these observations.
Runaway electron damage to the Tore Supra Phase III outboard pump limiter
International Nuclear Information System (INIS)
Nygren, R.; Lutz, T.; Walsh, D.; Martin, G.; Chatelier, M.; Loarer, T.; Guilhem, D.
1996-01-01
Operation of the Phase III outboard pump limiter (OPL) in Tore Supra in 1994 was terminated prematurely when runaway electrons during the current decay following a disruption pierced leading edge tube on the electron side and caused a water leak. The location, about 20 mm outside the last closed flux surface during normal operation, and the infrared (IR) images of the limiter indicate that the runaways moved in large outward steps, i.e. tens of millimeters, in one toroidal revolution. For plasma (runaway) currents in the range of 155 to 250 kA, the drift orbits open to the outside. Basic trajectory computations suggest that such motion is possible under the conditions present for this experiment. Activation measurements made on sections of the tube to indicate the area of local damage are presented here. An understanding of this event may provide important guidance regarding the potential damage from runaways in future tokamaks
International Nuclear Information System (INIS)
Begrambekov, L.; Brosset, C.; Bucalossi, J.; Delchambre, E.; Gunn, J.P.; Grisolia, C.; Lipa, M.; Loarer, T.; Mitteau, R.; Moner-Garbet, P.; Pascal, J.-Y.; Shigin, P.; Titov, N.; Tsitrone, E.; Vergazov, S.; Zakharov, A.
2007-01-01
The uniform layer with thickness at least 50-100 μm was found on the CFC tiles from the inboard midplane after more than four years of tokamak operation. The upper part of the uniform layer was amorphous, but at the depth of ∼5 μm a structure consisting of micro-size regions with aromatic chains located parallel to the surface was found. Gradual transition from uniform layer to underlying CFC structure was observed. The reciprocating material probe was used for installation of CFC samples in the Tore Supra deuterium plasma. The thermal desorptional spectra of these samples are compared with the spectra of the samples irradiated in the laboratory stand and with the spectra of hydrogenated carbon film. The peculiarities of hydrogen isotope trapping under plasma irradiation and at the atmosphere are presented and discussed
Raman study of CFC tiles extracted from the toroidal pump limiter of Tore Supra
Pardanaud, C.; Giacometti, G.; Martin, C.; Ruffe, R.; Angot, T.; Aréou, E.; Pégourié, B.; Tsitrone, E.; Dittmar, T.; Hopf, C.; Jacob, W.; Schwarz-Selinger, T.; Roubin, P.
2011-08-01
The structure of six tiles extracted from the erosion and deposition zones (thin and thick deposition) of the Tore Supra toroidal pump limiter (TPL) have been analyzed in the framework of the DITS campaign using micro-Raman spectroscopy. This post-mortem analysis gives information on both carbon structure and D content. We have found that the carbon structure is most often similar to that of plasma-deposited hard amorphous carbon layers. The role of the surface temperature during the discharge in the D content is investigated: in all locations where the temperature does not reach more than 500 °C the D content seems to be roughly uniform with D/D + C ≈ 20%.
Modelling the erosion/deposition pattern of the Tore Supra Toroidal Pumped Limiter
International Nuclear Information System (INIS)
Panayotis, S.; Pégourié, B.; Borodin, D.; Kirschner, A.; Gunn, J.; Marandet, Y.; Mellet, N.
2015-01-01
This paper aims at understanding the main processes responsible for the erosion/deposition pattern observed on the surface of the Toroidal Pumped Limiter of Tore Supra, using the 3D local impurity transport code ERO. The influence of the plasma impurity content, CX-flux and surface temperature on the global carbon balance and erosion/deposition pattern is discussed. Main results are (1) that considering medium-range transport of C ions is mandatory for reproducing the main characteristics of the global C balance and erosion/deposition pattern, (2) that impurities and CX-atoms increase the erosion by a factor ⩽2 (without changing the net/gross erosion ratio), and (3) that chemical erosion is governed by the re-erosion of deposits, which depends strongly on the surface temperature
Thermal and non-thermal particle interaction with the LHCD launchers in Tore Supra
International Nuclear Information System (INIS)
Ekedahl, A.; Goniche, M.; Balorin, C.; Basiuk, V.; Bibet, Ph.; Chantant, M.; Colas, L.; Delpech, L.; Desgranges, C.; Eriksson, L.-G.; Joffrin, E.; Kazarian, F.; Lowry, C.; Moreau, Ph.; Petrzilka, V.; Portafaix, C.; Prou, M.; Roche, H.
2007-01-01
The interaction between the lower hybrid current drive (LHCD) launchers and the plasma has been studied during long pulse, high power operation in the Tore Supra tokamak. The main diagnostics used for characterising the plasma-launcher interaction are calorimetry of the energy extracted by the launchers and infrared (IR) imaging of the launchers and their side limiters. The calorimetry has allowed to identify three different heat sources on the LHCD launchers, namely the RF losses in the waveguides, a fraction (∼0.8%) of the total injected energy and, finally, fast ion losses during ion cyclotron resonance heating (ICRH), accounting for ∼1% of the injected ICRH energy. The interaction by fast ions is identified by infrared imaging of the LHCD launchers as a localised hotspot on the ion drift side, below or at the mid-plane
Determination of ion temperatures from Zeeman broadened spectral lines in the edge of Tore Supra
Energy Technology Data Exchange (ETDEWEB)
Klepper, C.C.; Isler, R.C.; Tobin, S.J.; Hogan, J.T. [Oak Ridge National Lab., TN (United States). Fusion Energy Div.; Hess, W.R. [Association EURATOM-CEA sur la Fusion Controlee, St-Paul-lez-Durance (France). Centre d`Etudes de Cadarache
1994-09-01
The authors have examined a {sup 3}P {yields} {sup 3}S multiplet of C III in Tore Supra in order to assess the possibility of determining the ion temperatures from transitions where the Zeeman effect cannot be neglected compared to the Doppler broadening. The preliminary studies lead them to believe that with good quality data the temperatures can be determined within about 20% in the 20--30 eV range and within about 50% in the neighborhood of 5 eV by fitting the entire multiplet rather than a semi-isolated feature, even though certain parameters important for the analysis, such as polarization effects of the optics, are not well characterized. In order to quantify these conclusions more precisely, future work will concentrate on developing numerical fitting routines and on examining the validity of the assumption that the distribution function for low ionization stages is Maxwellian.
Determination of ion temperatures from Zeeman broadened spectral lines in the edge of Tore Supra
International Nuclear Information System (INIS)
Klepper, C.C.; Isler, R.C.; Tobin, S.J.; Hogan, J.T.; Hess, W.R.
1994-01-01
The authors have examined a 3 P → 3 S multiplet of C III in Tore Supra in order to assess the possibility of determining the ion temperatures from transitions where the Zeeman effect cannot be neglected compared to the Doppler broadening. The preliminary studies lead them to believe that with good quality data the temperatures can be determined within about 20% in the 20--30 eV range and within about 50% in the neighborhood of 5 eV by fitting the entire multiplet rather than a semi-isolated feature, even though certain parameters important for the analysis, such as polarization effects of the optics, are not well characterized. In order to quantify these conclusions more precisely, future work will concentrate on developing numerical fitting routines and on examining the validity of the assumption that the distribution function for low ionization stages is Maxwellian
Measurement of the mean ionic charge on Tore supra by visible bremsstrahlung radiation
International Nuclear Information System (INIS)
Thieyacine Fall, M.
1991-01-01
The effective plasma charge Zeff (proportional to plasma impurity ratio) is of prime importance for controlled fusion by magnetic confinement because it is involved for plasma ignition. From bremsstrahlung radiation theory in the visible part of the spectrum it is shown how effective charge in the plasma is deduced. A validity criterion is established from experiments (radiation at λ = 5235 A) to obtain Zeff profile and error estimation. This profile allows the calculation of resistivity profiles from different theories which are compared to a magnetohydrodynamic code. Calculation time is reduced by a fast analysis method from global parameters given time evolution of Zeff. This last measurement is essentially used for interpretation of experimental results of the Tore Supra physical program [fr
Ultra fast frequency sweep heterodyne reflectometer on the Tore Supra tokamak
Energy Technology Data Exchange (ETDEWEB)
Moreau, Ph.; Clairet, F.; Chareau, J.M.; Paume, M.; Laviron, C
1998-09-01
A new O-Mode dual frequency heterodyne reflectometer has been installed on Tore Supra, introducing outstanding improvement of the phase determination due high dynamic heterodyne detection, and ultra fast sweeps capabilities (10 {mu}s) provided by the solid state source HTOs. This system operates with O-mode electric field polarization in the range of 26 - 36 GHz and has been designed for density profile measurements. The reflectometer launches simultaneously into the plasma two frequencies separated by 320 MHz. The heterodyne detection improves the dynamic, up to 60 db, and is associated with an I.Q. detection to allow separate analysis of amplitude and phase of each reflected signals of both probing waves. Therefore, to calculate the density profile, the group delay can be defined in two different ways: from the derivative of the absolute phase of one of the two probing waves or by calculating the phase difference between the two probing waves. It is explained how ultra fast sweep operations (down to 10 {mu}s) significantly reduce the influence of the plasma turbulence upon the phase measurements. It is also pointed out the importance of filtering carefully the detected signal in order to keep only the information coming from the reflection at the cut-off and to get rid of parasitic reflections. It is shown that the phase difference technique does not remove completely fluctuations such as long radial correlation MHD perturbation. Density profiles determined by the heterodyne reflectometer are in good agreement with the measurements from the other diagnostics of Tore Supra. (author) 16 refs.
Deuterium inventory in Tore Supra: reconciling particle balance and post-mortem analysis
Tsitrone, E.; Brosset, C.; Pégourié, B.; Gauthier, E.; Bouvet, J.; Bucalossi, J.; Carpentier, S.; Corre, Y.; Delchambre, E.; Desgranges, L.; Dittmar, T.; Douai, D.; Ekedahl, A.; Escarguel, A.; Ghendrih, Ph.; Grisolia, C.; Grosman, A.; Gunn, J.; Hong, S. H.; Jacob, W.; Kazarian, F.; Kocan, M.; Khodja, H.; Linez, F.; Loarer, T.; Marandet, Y.; Martinez, A.; Mayer, M.; Meyer, O.; Monier Garbet, P.; Moreau, P.; Pascal, J. Y.; Pasquet, B.; Rimini, F.; Roche, H.; Roure, I.; Rosanvallon, S.; Roubin, P.; Roth, J.; Saint-Laurent, F.; Samaille, F.; Vartanian, S.
2009-07-01
Fuel retention, a crucial issue for next step devices, is assessed in present-day tokamaks using two methods: particle balance performed during shots and post-mortem analysis carried out during shutdowns between experimental campaigns. Post-mortem analysis generally gives lower estimates of fuel retention than integrated particle balance. In order to understand the discrepancy between these two methods, a dedicated experimental campaign has been performed in Tore Supra to load the vessel walls with deuterium (D) and monitor the trapped D inventory through particle balance. The campaign was followed by an extensive post-mortem analysis phase of the Tore Supra limiter. This paper presents the status of the analysis phase, including the assessment of the D content in the castellated tile structure of the limiter. Indeed, using combined surface analysis techniques, it was possible to derive the relative contributions of different zones of interest on the limiter (erosion, thick deposits, thin deposits), showing that the post-mortem inventory is mainly due to codeposition (90% of the total), in particular due to gap deposits. However, deuterium was also evidenced deep into the material in erosion zones (10% of the total). At the present stage of the analysis, 50% of the inventory deduced from particle balance has been found through post-mortem analysis, a significant progress with respect to previous studies (factor 8-10 discrepancy). This shows that post-mortem analysis can be consistent with particle balance provided specific procedures are implemented (dedicated campaign followed by extensive post-mortem analysis). Both techniques are needed for a reliable assessment of fuel retention in tokamaks, giving complementary information on how much and where fuel is retained in the vessel walls.
Study of heat transfer and particle transport in Tore Supra and HL-2A tokamaks
International Nuclear Information System (INIS)
Song, S.
2011-12-01
This thesis reports on experimental studies of heat and particles transport performed on 2 large tokamaks: Tore Supra (based at CEA/Cadarache, France) and HL-2A (based at the Southwestern Institute of Physics, Chengdu, China). The modulated source is the Electron Cyclotron Resonance Heating (ECRH) for the heat pinch and density pump-out studies, while the non-local transport experiments use the Supersonic Molecular Beam Injection (SMBI) as source of modulation. The emphasis is put on the inward heat pinch. In the off-axis ECRH modulation experiments on Tore Supra with low frequency (1 Hz), strong heat inward transport has been observed, in particular for low density. Two transport models have been applied in order to analyze the experimental behavior. The first one is the linear pinch model (LPM) and the second one is an empirical model based on micro-instabilities theory, named Critical Gradient Model (CGM). Good agreement has been found for all harmonics between the experimental data and the simulation using LPM. On the other hand, good agreement has not been achieved using CGM. The density pump-out with large particles and energy losses during ECRH is commonly observed in tokamaks. A new dynamic approach using the modulation technique has been used in HL-2A for analyzing the transient phase of the density pump-out. A correlation between the turbulence increase and the density pump-out has been found. The non-local transport phenomenon, characterized by a fast transient process compared to the normal diffusive response to the perturbation is observed. Both phenomena, i.e., pump-out and non-locality, show as simultaneous variation of density and temperature. This can be an inspiration for the usage of a transport matrix which considers the density and temperature evolution together. Simulations with a simple transport matrix, with non-diagonal terms coupling temperature and density qualitatively reproduce the non-local and pump-out effects qualitatively
Energy measurement of fast ions trapped in the toroidal field ripple of Tore Supra
International Nuclear Information System (INIS)
Basiuk, V.; Becoulet, A.; Hutter, T.; Martin, G.; Pecquet, A.L.; Saoutic, B.
1993-09-01
During additional heating in Tore Supra (ICRF or NBI) fast ion losses due to the toroidal field ripple were clearly measured by a set of graphite probes. This diagnostic collects the flow of fast ions entering a vertical port and usually shows a maximum flux for ions originating from the vicinity of surface δ * = 0. During the monster sawteeth regime, achieved with ICRF, a remarkable phenomenon was observed: the ejection of fast ions, not correlated with any measured MHD activity. The radial distribution of these ions is quite different from that usually observed exhibiting a peak located in the central section of the plasma. In order to measure the energy distribution of these ions, from 80 keV (energy of the neutral beam injected in Tore Supra) up to 1 MeV (expected during ICRF), a new diagnostic is under construction. The principle of the diagnostic is to discriminate the ions in energy using their Larmor radius (p = 1.3 cm for 100 keV → p = 3.6 cm for 700 keV, B = 4T). The detector is made of a hollow graphite cylinder with a small entrance slot, located in a vertical port on the ion drift side. An array of six metallic collectors placed inside the graphite cylinder intercepts the ions. The current on each collector was estimated at 10 → 100 nA, during ICRF heating. The energy resolution of this diagnostic is expected to be about 20 keV for the lowest energy range and 100 keV for the highest. This type of ruggedized detector might be extrapolated for the measurements of alpha particle losses in future DT experiments. It should also be suitable for the studies of stochastic ripple diffusion. (authors). 3 refs., 9 figs
Deuterium inventory in Tore Supra: reconciling particle balance and post-mortem analysis
International Nuclear Information System (INIS)
Tsitrone, E.; Brosset, C.; Pegourie, B.; Gauthier, E.; Bouvet, J.; Bucalossi, J.; Carpentier, S.; Corre, Y.; Delchambre, E.; Dittmar, T.; Douai, D.; Ekedahl, A.; Ghendrih, Ph.; Grisolia, C.; Grosman, A.; Gunn, J.; Hong, S.H.; Desgranges, L.; Escarguel, A.; Jacob, W.
2009-01-01
Fuel retention, a crucial issue for next step devices, is assessed in present-day tokamaks using two methods: particle balance performed during shots and post-mortem analysis carried out during shutdowns between experimental campaigns. Post-mortem analysis generally gives lower estimates of fuel retention than integrated particle balance. In order to understand the discrepancy between these two methods, a dedicated experimental campaign has been performed in Tore Supra to load the vessel walls with deuterium (D) and monitor the trapped D inventory through particle balance. The campaign was followed by an extensive post-mortem analysis phase of the Tore Supra limiter. This paper presents the status of the analysis phase, including the assessment of the D content in the castellated tile structure of the limiter. Indeed, using combined surface analysis techniques, it was possible to derive the relative contributions of different zones of interest on the limiter (erosion, thick deposits, thin deposits), showing that the post-mortem inventory is mainly due to codeposition (90% of the total), in particular due to gap deposits. However, deuterium was also evidenced deep into the material in erosion zones (10% of the total). At the present stage of the analysis, 50% of the inventory deduced from particle balance has been found through post-mortem analysis, a significant progress with respect to previous studies (factor 8-10 discrepancy). This shows that post-mortem analysis can be consistent with particle balance provided specific procedures are implemented (dedicated campaign followed by extensive post-mortem analysis). Both techniques are needed for a reliable assessment of fuel retention in tokamaks, giving complementary information on how much and where fuel is retained in the vessel walls.
Energy Technology Data Exchange (ETDEWEB)
Richou, M
2007-06-15
Tokamaks are devices aimed at studying magnetic fusion. They operate with high temperature plasmas containing hydrogen, deuterium or tritium. One of the major issue is to control the plasma-wall interaction. The plasma facing components are most often in carbon. The major drawback of carbon is the existence of carbon deposits and dust, due to erosion. Dust is potentially reactive in case of an accidental opening of the device. These deposits also contain H, D or T and induce major safety problems when tritium is used, which will be the case in ITER. Therefore, the understanding of the deposit formation and structure has become a main issue for fusion researches. To clarify the role of the deposits in the retention phenomenon, we have done different complementary characterizations for deposits collected on similar places (neutralizers) in tokamaks Tore Supra (France) and TEXTOR (Germany). Accessible microporous volume and pore size distribution of deposits has been determined with the analysis of nitrogen and methane adsorption isotherms using the BET, Dubinin-Radushkevich and {alpha}{sub s} methods and the Density Functional Theory (DFT). To understand growth mechanisms, we have studied the deposit structure and morphology. We have shown using Transmission Electron Microscopy (TEM) and Raman micro-spectrometry that these deposits are non amorphous and disordered. We have also shown the presence of nano-particles (diameter between 4 and 70 nm) which are similar to carbon blacks: nano-particle growth occurs in homogeneous phase in the edge plasma. We have emphasised a dual growth process: a homogenous and a heterogeneous one. (author)
Real time control of fully non-inductive 6 minute, 1 Gigajoule plasma discharges in Tore Supra
International Nuclear Information System (INIS)
Houtte, D. van; Martin, G.; Bucalossi, J.; Saint-Laurent, F.
2005-01-01
The experimental programme of Tore Supra has been devoted in 2003 to study simultaneously heat removal capability and particle exhaust in steady-state fully non-inductive current drive discharges. This required both advanced technology integration and steady-state real time plasma control. In particular, an improvement of the plasma position within a few millimetres range, and new real time cross controls between RF power and various actuators built around a shared memory network, have allowed Tore Supra to access a powerful steady-state regime with an improved safety level for the actively cooled plasma facing components. Feedback controlled fully non-inductive plasma discharges have been sustained in a steady-state regime up to 6 minutes with a new world record of injected-extracted energy exceeding 1 GJ. Advanced tools, experimental results and brief physics analysis of these discharges are presented. (author)
International Nuclear Information System (INIS)
Schunke, B.; Voytsenya, V.; Gil, C.; Lipa, M.
2003-01-01
Plasma diagnostics using visible or ultra-violet or infra-red radiations require mirrors to probe the plasma. These mirrors have to sustain very hostile environment and despite that must maintain good optical properties. Mirror samples made of 3 different metals: copper, stainless steel and molybdenum have been designed and installed in Tore Supra tokamak and will be exposed to plasmas till mid 2004. This project will allow fusion engineers to assess the impact of plasma ion bombardment on mirror reflectivity. Optical properties and parameters concerning the surface state of the samples have been measured before the installation in Tore Supra and are presented in the paper. Simulations with a Monte-Carlo code predict the particle flux and spectra near the samples. A specific back mirror reflector has been designed to probe mirror reflectivity changes. (A.C.)
Czech Academy of Sciences Publication Activity Database
Gunn, J. P.; Boucher, C.; Dionne, M.; Ďuran, Ivan; Fuchs, Vladimír; Loarer, T.; Nanobashvili, I.; Pánek, Radomír; Pascal, J.-Y.; Saint-Laurent, F.; Stöckel, Jan; Van Rompuy, T.; Zagórski, R.; Adámek, Jiří; Bucalossi, J.; Dejarnac, Renaud; Devynck, P.; Hertout, P.; Hron, Martin; Lebrun, G.; Moreau, P.; Rimini, F.; Sarkissian, A.; Van Oost, G.
363-365, - (2007), s. 484-490 ISSN 0022-3115. [International Conference on Plasma-Surface Interactions in Controlled Fusion Devices/17th./. Hefei, 22.05.2006-26.05. 2006] R&D Projects: GA ČR GP202/03/P062 Institutional research plan: CEZ:AV0Z20430508 Keywords : Cross-field transport * Edge plasma * Plasma flow * Tore Supra Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.643, year: 2007
Measurements of scrape-off layer ion-to-electron temperature ratio in Tore Supra ohmic plasmas
Czech Academy of Sciences Publication Activity Database
Kočan, M.; Gunn, J. P.; Pascal, J.-Y.; Bonhomme, G.; Devynck, P.; Ďuran, Ivan; Gauthier, E.; Ghendrih, P.; Marandet, Y.; Pegourie, B.; Vallet, J.-C.
390-391, - (2009), s. 1074-1077 ISSN 0022-3115. [International Conference on Plasma-Surface Interactions in Controlled Fusion Devices/18th./. Toledo, 26.05.2008-30.05. 2008] Institutional research plan: CEZ:AV0Z20430508 Keywords : Ion temperature * Electron temperature * Edge plasma * Tore Supra Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.933, year: 2009
International Nuclear Information System (INIS)
Dittmar, T.; Tsitrone, E.; Pegourie, B.; Cadez, I.; Pelicon, P.; Gauthier, E.; Languille, P.; Likonen, J.; Litnovsky, A.; Markelj, S.; Martin, C.; Mayer, M.; Pascal, J.-Y.; Pardanaud, C.; Philipps, V.; Roth, J.; Roubin, P.; Vavpetic, P.
2011-01-01
A dedicated study on fuel retention has been launched in Tore Supra, which includes a D wall-loading campaign and the dismantling of the main limiter (Deuterium Inventory in Tore Supra, DITS project). This paper presents new results from a second post-mortem analysis campaign on 40 tiles with special emphasis on the D retention in the gaps. SIMS analysis reveals that only 1/3 of the thickness of deposits in the plasma shadowed zones are due to the DITS wall-loading campaign. As pre-DITS deposits contain less D than DITS deposits, the contribution of DITS to the D inventory is about 30-50%. The new estimate for the total amount of D retained in the Tore Supra limiter is 1.7 x 10 24 atoms, close to the previous estimate, with the gap surfaces contributing about 33%. NRA measurements show a stepped decrease of D along the gap with strong asymmetries between different gap orientations.
Energy Technology Data Exchange (ETDEWEB)
Cambe, A
2002-06-28
The work presented in this thesis focuses on the interactions between energetic particles coming from thermonuclear plasma and the inner components of a fusion machine. This interaction induces two major problems: erosion of the wall, and tritium retention. This report treats the erosion of carbon based materials. The first part is devoted to chemical sputtering, that appears to be the principal erosion mechanism, compared to physical sputtering and radiation enhanced sublimation that both can be limited. Chemical sputtering has been studied in situ in the tokamak Tore-Supra for ohmic and lower hybrid (LH) heated discharges, by means of mass spectrometry and optical spectroscopy. We have shown that it is necessary to take into account both methane and heavier hydrocarbons (C{sub 2}D{sub x} and C{sub 3}D{sub y}) in the determination of the chemical sputtering yield. It is found that for the ohmic discharges, the sputtering yield of CD{sub 4} (Y{sub CD4}) is highly flux ({phi}) dependent, showing a variation of the form: Y{sub CD4} {proportional_to} {phi}{sup -0.23}. The experimental study also reveals that an increase of the surface temperature induces an augmentation of Y{sub CD4}. The interpretation and the modelling of the experimental results have been performed with a Monte Carlo code (BBQ. In the second part of this work, we have developed and installed an infrared spectroscopy diagnostic in the 0.8-1.6, {mu}m wavelength range dedicated to the measurement of surface temperature, and the identification of atomic and molecular lines emitted during plasma/wall interactions. In the third part, we present the feasibility study of an in situ tungsten deposition process at low temperature(<80 deg C) in order to suppress the chemical sputtering. This study shows that, with this method call Plasma Assisted Chemical Vapor Deposition (PACVD), we are able to coat the whole inner vessel of a tokamak with 1 {mu}m of tungsten. (author)
Energy Technology Data Exchange (ETDEWEB)
Colas, L
1996-09-23
Internal small-scale magnetic turbulence is a serious candidate to explain the anomalous heat transport in tokamaks. This turbulence is badly known in the gradient region of large machines. In this work internal magnetic fluctuations are measured on Tore Supra with an original diagnostic : Cross Polarization Scattering (CPS). This experimental tool relies on the Eigenmode change of a probing polarised microwave beam scattered by magnetic fluctuations, close to a cut-off layer for the incident wave. In this work, the diagnostic is first qualified to assess its sensitivity to magnetic fluctuations, and the spatial localisation for its measurements. The magnetic fluctuation behaviour is then analysed over a wide range of plasma current, density and additional power, and interpreted with a simple 1-D scattering model. A scan of the plasma density or magnetic field is used to move the CPS measurement location from r/a = 0.3 to r/a = 0.75. A fluctuation radial profile is obtained by two means. In L-mode discharges, the relation between magnetic fluctuations, temperature profiles and local heat diffusivities is investigated. With all measurements, it is also possible to look for a local parameter correlated to the turbulence in a large domain of plasma conditions. The fluctuation-induced local heat diffusivity expected from the measured fluctuations is estimated using the non-collisional quasi-linear formula: X{sup mag}{sub e} = {pi}qRV{sub te}({delta}B / B){sup 2}. Both the absolute values and the parametric dependence of calculated X{sup mag}{sub e} are close to the electron thermal diffusivities Xe determined by transport analysis. In particular, a threshold is evidenced in the dependence of fluctuation-induced heat fluxes on local {nabla}T{sub e}, which is analogous to the critical gradient for measured heat fluxes. The experimental setup is also sensitive to the Thomson scattering of the probing wave by density fluctuations. Its measurements are analysed as the
Experience feedback from high heat flux component manufacturing for Tore Supra
International Nuclear Information System (INIS)
Schlosser, J.; Durocher, A.; Huber, T.; Garin, P.; Schedler, B.; Agarici, G.
2001-01-01
Tore Supra is involved in flat tile carbon armoured plasma facing components (PFCs) since 1985. In 1997, a third generation of components, based on the original concept developed with Plansee Company, called active metal casting (AMC[reg]), has been launched. Since 1998, 660 elementary components for the toroidal pump limiter (TPL) are in production. The route of the manufacture is rather complex and many controls were requested all along the fabrication to insure a high reliability of the elements. One of the main controls is the final infrared (IR) test allowing to determine the quality of the bonding between the carbon fibre composite (CFC) tiles and the heat sink made of copper-chromium-zirconium alloy (CuCrZr). Although results for the first batch of elements were as expected (less than 5% rejected at the final test), unexpected defects appeared with the followings batches. Investigations on the fabrication processes underlined the importance of having a better heat treatment of the pieces in copper alloy (CuCrZr), however this was not sufficient to completely explain the observed defects
Power exhaust and edge control in steady state Tore Supra plasma
International Nuclear Information System (INIS)
Mitteau, R.
2002-01-01
Tore Supra is operated since 2001 with a flat limiter which is designed for 10 MW/m 2 . The limiter is located in the bottom of the vacuum vessel. It was only partial in 2001, but it is now fully toroidal without poloidal leading edges. Part of the experimental campaign of 2001 was devoted to the physical as well as technological qualification of the limiter. For 4 MW injected, the limiter extracted 2.5 MW and heat flux densities reached 2.5 MW/m 2 . It is still modest compared to the design value, but nonetheless enables a comparison to the modelling as surface temperature increased locally to 400 deg C. Thermal steady state is reached in 5-8 seconds. The values of heat flux and the deposition pattern are in very good accordance with design simulations. The heat flux pattern is a combination of parallel and perpendicular flow components which are roughly of equal magnitude. Insights on the heat flux deposition pattern as well as on the tiles behaviour are given. Operation with such a large size high heat flux component sets renewed emphasis on issues such as feed back systems, active security, cooling parameter and in situ assessment of the elements. They are dealt with in the paper. (author)
Spectral broadening measurement of the lower hybrid waves during long pulse operation in Tore Supra
Berger-By, G.; Decampy, J.; Antar, G. Y.; Goniche, M.; Ekedahl, A.; Delpech, L.; Leroux, F.; Tore Supra Team
2014-02-01
On many tokamaks (C-Mod, EAST, FTU, JET, HT-7, TS), a decrease in current drive efficiency of the Lower Hybrid (LH) waves is observed in high electron density plasmas. The cause of this behaviour is believed to be: Parametric Instabilities (PI) and Scattering from Density Fluctuations (SDF). For the ITER LH system, our knowledge must be improved to avoid such effects and to maintain the LH current drive efficiency at high density. The ITPA IOS group coordinates this effort [1] and all experimental data are essential to validate the numerical codes in progress. Usually the broadening of the LH wave frequency spectrum is measured by a probe located in the plasma edge. For this study, the frequency spectrum of a reflected power signal from the LH antenna was used. In addition, the spectrum measurements are compared with the density fluctuations observed on RF probes located at the antenna mouth. Several plasma currents (0.6 to 1.4 MA) and densities up to 5.2 × 1019 m-3 have been realised on Tore Supra (TS) long pulses and with high injected RF power, up to 5.4 MW-30s. This allowed using a spectrum analyser to make several measurements during the plasma pulse. The side lobe amplitude, shifted by 20-30MHz with respect to the main peak, grows with increasing density. Furthermore, for an increase of plasma current at the same density, the spectra broaden and become asymmetric. Some parametric dependencies are shown in this paper.
Power exhaust and edge control in steady state tore supra plasma
International Nuclear Information System (INIS)
Mitteau, R.; Guilhem, D.; Vallet, J.C.
2003-01-01
Tore Supra is operated since 2001 with a toroidal limiter designed to remove continuously a heat power of 15 MW at a maximum (ITER relevant) heat flux density of 10 MW/m 2 . The limiter is located in the bottom of the vacuum vessel and is actively cooled by a pressurised water loop. For an injection of 6 MW of additional power, the limiter extracts 3.6 MW and the surface temperature stabilises typically at 400 deg C in 5 seconds during discharges lasting up to 260 seconds. The maximum heat flux density reach 3 MW/m 2 which is still modest compared to the design value, but nevertheless enables a comparison to the modelling. Heat flux and deposition pattern are in very good accordance with design simulations. Additional heat load concentrations specific to radio-frequency heating superimpose to the convection heat load at levels that are commensurable with the elements thermal capability. Insights on the tiles behaviour are given. Operation with such a large size high heat flux component sets an renewed emphasis on issues such as feed back systems, active security, cooling parameters and in situ assessment of the elements. These issues are dealt with in this paper. (author)
Actively cooled pump limiters and power scrape-off length measurements in Tore-Supra
International Nuclear Information System (INIS)
Guilhem, D.; Seigneur, A.; Chappuis, P.; Chatelier, M.; DeMichelis, C.; Deschamps, P.; Grosman, A.; Hess, W.; Lecoustey, P.; Loarer, T.; Poutchy, L.; Schlosser, J.
1992-01-01
TORE-SUPRA is a superconducting Tokamak aimed at studying long plasma pulses (>30 s). It is equipped with two types of pump limiters (PL). A provisional type, semi-inertially cooled between shots, has been used for plasma scrape off characterization. The e-folding length λq for power deposition on these components has been unfolded (1.0cm 19 m -3 19 m -3 ), of power level up to 4 MW and of toroidal magnetic field (1.5 T -1/2 ). The second type used for long pulse operation, is actively cooled during shots, its thermal time constant being less than 2 seconds. Experiments using this ITER relevant technology are presented. Three of the actively cooled limiters have been successfully tested in a steady state regime with a surface temperature less than 1000 deg C (I p =1.6 MA). The design value for power removal on this type of limiters has been obtained. Peak power fluxes of 10 MW/m 2 have been estimated. This represents a breakthrough for high heat flux components since critical heat flux and burnout with subcooled flow boiling are major aspects for this kind of design
Assessing braze quality in the actively cooled Tore Supra Phase III outboard pump limiter
International Nuclear Information System (INIS)
Nygren, R.E.; Lutz, T.L.; Miller, J.D.; McGrath, R.; Dale, G.
1994-01-01
The quality of brazing of pyrolytic graphite armor brazed to copper tubes in Tore Supra's Phase III Outboard Pump Limiter was assessed through pre-service qualification testing of individual copper/tile assemblies. The evaluation used non-destructive, hot water transient heating tests performed in the high-temperature, high-pressure flow loop at Sandia's Plasma Materials Test Facility. Surface temperatures of tiles were monitored with an infrared camera as water at 120 degrees C at about 2.07 MPa (300 psi) passed through a tube assembly initially at 30 degrees C. For tiles with braze voids or cracks, the surface temperatures tagged behind those of adjacent well-bonded tiles. Temperature tags were correlated with flaw sizes observed during repairs based upon a detailed 2-D heat transfer analyses. open-quotes Badclose quotes tiles, i.e., temperature tags of 10-20 degrees C depending upon tile's size, were easy to detect and, when removed, revealed braze voids of roughly 50% of the joint area. Eleven of the 14 tubes were rebrazed after bad tiles were detected and removed. Three tubes were rebrazed twice
Modeling of neutral transport and impurity generation in the Tore Supra pump limiter
International Nuclear Information System (INIS)
Klepper, C.C.; Owen, L.W.; Mioduszewski, P.K.; Grosman, A.
1989-01-01
A system of modular pump limiters is employed in Tore Supra for particle control. It includes one large outboard module which is instrumented with an optical multi-channel analyzer viewing the neutralizer plate, in addition to pressure, temperature and particle diagnostics. The transport of neutrals in both the particle scoop mode and in the pump limiter mode with active pumping is modeled with the DEGAS code. Equilibrium neutral pressure and density, H α -intensity at the neutralizer plate, and particle back-flow into the scrape-off layer are calculated for typical projected plasma edge conditions. Effects on neutral particle transport of varying the length of the ''shelf'' separating the throat region from the pumping chamber are investigated. The generation and transport of carbon impurities arising from ion impact sputtering at the neutralizer plate are estimated. The short mean-free-path for ionization of sputtered carbon atoms suggests the possibility of spectroscopically measuring the effects of poloidal flux variations arising from shadowing of the modular limiter system. (orig.)
Assessing braze quality in the actively cooled Tore Supra phase III outboard pump limiter
International Nuclear Information System (INIS)
Hygren, R.; Lutz, T.; Miller, J.
1994-01-01
This paper discusses the assessment of quality of brazing of pyrolytic graphite (PG) armor brazed to copper tubes in Tore Supra's Phase III Outboard Pump Limiter (OPL). The limiter head is a bank of 14 water-cooled copper tubes with several hundred brazed PG tiles. Braze quality was first assessed through pre-service qualification testing of individual copper/tiles assemblies. The quality of brazes was evaluated using (non-destructive) transient heating (open-quotes hot waterclose quotes) tests performed in the high temperature, high pressure flow loop at Sandia's Plasma Materials Test Facility. The surface temperatures of tiles were monitored with an infra-red (IR) camera as water at 120 degrees C water at about 2.07 MPa (300 psi) passed through a tube assembly initially at 30 degrees C. For tiles with braze voids or cracks, the surface temperatures lagged behind those of adjacent well bonded tiles. Temperature lags were correlated with flaw sizes observed during repairs using a detailed 2-D heat transfer analyses. open-quotes Badclose quotes tiles, i.e., temperature lags of 10-20 degrees C depending upon tile's size, were easy to detect and, when removed, revealed braze voids of roughly 50% of the joint area. 11 of the 14 tubes were rebrazed after bad tiles were detected and removed. Three tubes were re-brazed twice
Deuterium in-vessel retention characterisation through the use of particle balance on Tore Supra
International Nuclear Information System (INIS)
Bucalossi, J.; Brosset, C.; Pegourie, B.; Tsitrone, E.; Dufour, E.; Eckedahl, A.; Geraud, A.; Goniche, M.; Gunn, J.; Loarer, T.; Monier-Garbet, P.; Vallet, J.C.; Vartanian, S.
2007-01-01
Fuel retention inside plasma facing components will be a crucial issue not only in fusion reactors of the future, but also in ITER. The estimation of the fraction of the fuel which remains trapped inside the vessel is quite a difficult task. Particle balance analysis provides information for the whole vacuum chamber as a function of time and can be use to monitor the tritium in-vessel retention in real-time. On Tore Supra with a careful choice and position of pressure sensors, proper calibration procedures, the accuracy of the balance is around 10%. Particle balance analysis have been performed on many long pulse discharges and deuterium in-vessel retention has been found to be a constant around 5 x 10 20 D/s after several minutes of plasma. The evolution of the retention rate with plasma parameters indicates that deuterium bulk implantation and diffusion could dominate codeposition with carbon atoms. Particle balance is a powerful tool that should be implemented in ITER
Study of fusion plasma microturbulence by reflectometry in Tore Supra tokamak
International Nuclear Information System (INIS)
Gerbaud, Th.
2008-11-01
Fast-sweeping reflectometry in extraordinary mode allows direct measurement of radial wave-number local spectra S(δ n /n](k r ,r), and radial profiles of density fluctuations, on Tore Supra tokamak. Wavelet-based approach - a mathematical tool for position-frequency analysis - made possible to consider the strong radial variation of the measured turbulence. Special consideration was given to the validation of spectra and turbulent profiles measurements, by comparing with experimental measurements (reflectometry, probes) and numerical non-linear gyrokinetic simulations. This density fluctuations measurement method has been used to analyse the local transport, by performing a dimensionless scaling on collisionality, ν * . The scaling experiments allow direct comparisons of plasmas from different tokamaks. A clear decrease of the normalized confinement time of the plasma energy with the normalized collisionality was observed: Bτ E ∼ ν *-0.5±0.15 . These new measurements of density fluctuations profiles have shown an intense rise of the edge turbulence (r/a > 0.8) when increasing - also observed by Doppler reflectometry diagnostic - providing a physical explanation of the loss of confinement with the normalized collisionality. More central regions did not present apparent variations (δ n /n, χ(eff)). Core plasma simulations (linear stability code KineZero and non-linear gyrokinetic GYRO) were performed, in order to analyse the experimental behaviour of the plasma. (author)
Kinetic Monte-Carlo modeling of hydrogen retention and re-emission from Tore Supra deposits
International Nuclear Information System (INIS)
Rai, A.; Schneider, R.; Warrier, M.; Roubin, P.; Martin, C.; Richou, M.
2009-01-01
A multi-scale model has been developed to study the reactive-diffusive transport of hydrogen in porous graphite [A. Rai, R. Schneider, M. Warrier, J. Nucl. Mater. (submitted for publication). http://dx.doi.org/10.1016/j.jnucmat.2007.08.013.]. The deposits found on the leading edge of the neutralizer of Tore Supra are multi-scale in nature, consisting of micropores with typical size lower than 2 nm (∼11%), mesopores (∼5%) and macropores with a typical size more than 50 nm [C. Martin, M. Richou, W. Sakaily, B. Pegourie, C. Brosset, P. Roubin, J. Nucl. Mater. 363-365 (2007) 1251]. Kinetic Monte-Carlo (KMC) has been used to study the hydrogen transport at meso-scales. Recombination rate and the diffusion coefficient calculated at the meso-scale was used as an input to scale up and analyze the hydrogen transport at macro-scale. A combination of KMC and MCD (Monte-Carlo diffusion) method was used at macro-scales. Flux dependence of hydrogen recycling has been studied. The retention and re-emission analysis of the model has been extended to study the chemical erosion process based on the Kueppers-Hopf cycle [M. Wittmann, J. Kueppers, J. Nucl. Mater. 227 (1996) 186].
Comparison of two regularization methods for soft x-ray tomography at Tore Supra
International Nuclear Information System (INIS)
Jardin, A; Mazon, D; Bielecki, J
2016-01-01
Soft x-ray (SXR) emission in the range 0.1–20 keV is widely used to obtain valuable information on tokamak plasma physics, such as particle transport, magnetic configuration or magnetohydrodynamic activity. In particular, 2D tomography is the usual plasma diagnostic to access the local SXR emissivity. The tomographic inversion is traditionally performed from line-integrated measurements of two or more cameras viewing the plasma in a poloidal cross-section, like at Tore Supra (TS). Unfortunately, due to the limited number of measured projections and presence of noise, the tomographic reconstruction of SXR emissivity is a mathematical ill-posed problem. Thus, obtaining reliable results of the tomographic inversion is a very challenging task. In order to perform the reconstruction, inversion algorithms implemented in present tokamaks use a priori information as additional constraints imposed on the plasma SXR emissivity. Among several potential inversion methods, some of them have been identified as well suited to tokamak plasmas. The purpose of this work is to compare two promising inversion methods, i.e. the minimum fisher information method already used at TS and planned for WEST configuration, and the alternative 2nd order Phillips–Tikhonov regularization with smoothness constraints imposed on the second derivative norm. Respective accuracy of both reconstruction methods as well as overall robustness and computational time are studied, using several synthetic SXR emissivity profiles. Finally, a real case is studied through tomographic reconstruction from TS SXR database. (paper)
2-D mapping of ICRF-induced SOL perturbations in Tore Supra tokamak
International Nuclear Information System (INIS)
Colas, L.; Gunn, J.P.; Nanobashvili, I.; Petrzilka, V.; Goniche, M.; Ekedahl, A.; Heuraux, S.; Joffrin, E.; Saint-Laurent, F.; Balorin, C.; Lowry, C.; Basiuk, V.
2007-01-01
ICRF-induced SOL modifications are mapped for the first time in 2-D around Tore Supra ICRF antennas using reciprocating Langmuir probes. When probe heads are magnetically connected to powered antennas, radical modifications of floating potentials V float , effective temperatures T eff and ion saturation currents are observed. V float perturbations are located radially near antenna limiters, with a typical extension 2 cm. Poloidally they are locally minimal near the equatorial plane, and maximal near antenna box corners. Two possible interpretations for increased T eff are proposed: localised electron heating and RF loop voltage induced along probe circuit. Both interpretations rely on the generation of parallel RF fields by parallel RF currents on the antenna structure. The topology of such currents could explain the 2-D structure of T eff maps. Both interpretations also imply a positive DC biasing of the antenna environment. Differential biasing of nearby flux tubes drives DC E x B 0 convection that could explain 2-D density patterns
International Nuclear Information System (INIS)
Mitteau, R.; Guilhem, D.; Reichle, R.; Vallet, J.C.; Roche, H.; Buravand, Y.; Chantant, M.; Tsitrone, E.; Brosset, C.; Grosman, A.; Chappuis, P.
2006-01-01
Fusion devices with carbon as the main armour material are experiencing a growth in carbonaceous deposits at the surface of the plasma facing components. Tore Supra presents such deposits, and has specific features which influence their growth: long pulse operation and cooled walls. Deposits have a low thermal transfer to the cooled structure so that they appear as hot areas with the infrared imaging system looking at the elements surface temperature during plasma discharges. A 'degree of (carbon) deposit' on the toroidal pumped limiter is estimated by establishing the ratio between the apparent power on the limiter derived from the infrared measure and the actual one, deduced from a power balance analysis between the injected and the radiated power. This criterion is used to monitor the evolution of the deposit average thermal resistance. Successive shots have a similar 'degree of deposit', showing that the evaluation makes sense. Two years of data have been compiled (2003 and 2004), representing 3000 discharges (13 h of plasma, including 30 discharges longer than one minute). A three-fold increase in the 'degree of deposit' over six months is evidenced, following a limiter clean-up early in 2003. A comparison with calorimetric data produces a similar result, albeit less pronounced. Large steps in the degree of deposit are sometimes observed, usually correlated with identified events such as disruption, vessel opening, conditioning or plasma parameters change. It indicates that the deposit thermal resistance can change rapidly, although a systematic correlation with the above mentioned events could not be established
Mitteau, R.; Guilhem, D.; Reichle, R.; Vallet, J. C.; Roche, H.; Buravand, Y.; Chantant, M.; Tsitrone, E.; Brosset, C.; Grosman, A.; Chappuis, P.
2006-03-01
Fusion devices with carbon as the main armour material are experiencing a growth in carbonaceous deposits at the surface of the plasma facing components. Tore Supra presents such deposits, and has specific features which influence their growth: long pulse operation and cooled walls. Deposits have a low thermal transfer to the cooled structure so that they appear as hot areas with the infrared imaging system looking at the elements surface temperature during plasma discharges. A 'degree of (carbon) deposit' on the toroidal pumped limiter is estimated by establishing the ratio between the apparent power on the limiter derived from the infrared measure and the actual one, deduced from a power balance analysis between the injected and the radiated power. This criterion is used to monitor the evolution of the deposit average thermal resistance. Successive shots have a similar 'degree of deposit', showing that the evaluation makes sense. Two years of data have been compiled (2003 and 2004), representing 3000 discharges (13 h of plasma, including 30 discharges longer than one minute). A three-fold increase in the 'degree of deposit' over six months is evidenced, following a limiter clean-up early in 2003. A comparison with calorimetric data produces a similar result, albeit less pronounced. Large steps in the degree of deposit are sometimes observed, usually correlated with identified events such as disruption, vessel opening, conditioning or plasma parameters change. It indicates that the deposit thermal resistance can change rapidly, although a systematic correlation with the above mentioned events could not be established.
X mode reflectometry for edge density profile measurements on Tore Supra
International Nuclear Information System (INIS)
Clairet, F.; Bottereau, C.; Chareau, J.M.; Paume, M.; Sabot, R.
1999-01-01
X mode heterodyne reflectometry associated with fast sweep capabilities demonstrates very precise measurement on Tore Supra and a high sensitivity (∼10 17 m -3 ) to density variations. Very good agreement with Thomson scattering measurement is observed. Fluctuations of the radial positions of the profile are no more than ± 0.5 cm. However, edge magnetic field ripple can be a concern since it is not easy to stand precisely for the wave trajectory into the plasma and for the toroidal position of the cutoff layer; nevertheless if the error can be estimated to be less than than 3 cm in the position of the whole profile, addition work is needed combining 3-D ray tracing and different antenna systems. Additional LH heating generates an ECE noise in the same frequency range of the reflectometer and is detected. This emission throughout the plasma is fortunately stopped by the upper X mode cutoff and is also reabsorbed by the electron cyclotron resonance. But at the very edge, due to a misalignment of the antenna to the plasma magnetic field and the low optical thickness of the plasma, the first cutoff frequency, i.e. the profile initialization, may be determined less precisely. (authors)
Role of the pump limiter throat-ergodic divertor effect on edge plasma
International Nuclear Information System (INIS)
Grosman, A.; Samain, A.; Ghendrih, P.; Capes, H.; Morera, J.P.
1988-01-01
A large part of the Tore Supra programme is devoted to plasma edge studies. Two types of such density control apparatus have been implemented, a set of pumps limiters and the ergodic divertor. The goal of the present paper is to investigate the effect of the pump limiter throat on pumping efficiency. We present also the possibilities of the ergodic divertor device to facilitate plasma pumping and power exhaust
Energy Technology Data Exchange (ETDEWEB)
Moreau, F.
1996-06-07
In the Tokamak TORE-SUPRA, the plasma facing components absorbs and evacuate (active cooling) high power fluxes (up to 10 MW/m{sup 2}). Their thermal behavior study is essential for the success of controlled thermonuclear fusion line. The first part is devoted to the study of power deposition on the TORE-SUPRA actively cooled limiters. A model of power deposition on one of the limiters is developed. It takes into account the magnetic topology and a description of the plasma edge. The model is validated with experimental calorimetric data obtained during a series of shots. This will allow to compare the surface temperature measurements with the predicted ones. The main purpose of this thesis was to evaluate and develop a new temperature measurement system. It works in the near infrared range (890 nm) and is designed to complete the existing thermographic diagnostic of TORE-SUPRA. By using the radiation laws (for a blackbody and the plasma) and the laboratory calibration one can estimate the surface temperature of the observed object. We evaluate the performances and limits of such a device in the harsh conditions encountered in a Tokamak environment. On the one hand, in a quasi ideal situation, this analysis shows that the range of measurements is 600 deg. C to 2500 deg. C. On the other hand, when one takes into account of the plasma radiation (with an averaged central plasma density of 6.10{sup 19} m{sup -3}), we find that the minimum surface temperature rise to 900 deg. C instead of 700 deg. C. In the near future, according to the development of IR-CCD cameras working in the near infrared range up to 2 micrometers, we will be able to keep the good spatial resolution with an improved lower limit for the temperature down to 150 deg. C. The last section deals with a number of computer tools to process the images obtained from experiments on TORE-SUPRA. A pattern recognition application was developed to detect a complex plasma iso-intensity structure. 87 refs.
International Nuclear Information System (INIS)
Guilhem, D.; Adjeroud, B.; Balorin, C.; Buravand, Y.; Bertrand, B.; Bondil, J.L.; Desgranges, C.; Gauthier, E.; Lipa, M.; Messina, P.; Missirlian, M.; Mitteau, R.; Moulin, D.; Pocheau, C.; Portafaix, C.; Reichle, R.; Roche, H.; Saille, A.; Vallet, S.
2004-01-01
Tore-Supra has a steady-state magnetic field using super-conducting magnets and water-cooled plasma facing components for high performances long pulse plasma discharges. When not actively cooled, plasma-facing components can only accumulate a limited amount of energy since the temperature increase continuously (T proportional to √(t)) during the discharge until radiation cooling is equal to the incoming heat flux (T > 1800 K). Such an environment is found in most today Tokamaks. In the present paper we report the recent results of Tore-Supra, especially the design of the new generation of infrared endoscopes to measure the surface temperature of the plasma facing components. The Tore-Supra infrared thermography system is composed of 7 infrared endoscopes, this system is described in details in the paper, the new JET infrared thermography system is presented and some insights of the ITER set of visible/infrared endoscope is given. (authors)
Energy Technology Data Exchange (ETDEWEB)
Guilhem, D.; Adjeroud, B.; Balorin, C.; Buravand, Y.; Bertrand, B.; Bondil, J.L.; Desgranges, C.; Gauthier, E.; Lipa, M.; Messina, P.; Missirlian, M.; Mitteau, R.; Moulin, D.; Pocheau, C.; Portafaix, C.; Reichle, R.; Roche, H.; Saille, A.; Vallet, S
2004-07-01
Tore-Supra has a steady-state magnetic field using super-conducting magnets and water-cooled plasma facing components for high performances long pulse plasma discharges. When not actively cooled, plasma-facing components can only accumulate a limited amount of energy since the temperature increase continuously (T proportional to {radical}(t)) during the discharge until radiation cooling is equal to the incoming heat flux (T > 1800 K). Such an environment is found in most today Tokamaks. In the present paper we report the recent results of Tore-Supra, especially the design of the new generation of infrared endoscopes to measure the surface temperature of the plasma facing components. The Tore-Supra infrared thermography system is composed of 7 infrared endoscopes, this system is described in details in the paper, the new JET infrared thermography system is presented and some insights of the ITER set of visible/infrared endoscope is given. (authors)
International Nuclear Information System (INIS)
Preynas, M.; Goniche, M.; Hillairet, J.; Litaudon, X.; Ekedahl, A.; Colas, L.
2013-01-01
To achieve steady-state operation on future fusion devices, in particular on ITER, the coupling of the lower hybrid wave must be optimized on a wide range of edge conditions. However, under some specific conditions, deleterious effects on the lower hybrid current drive (LHCD) coupling are sometimes observed on Tore Supra. In this way, dedicated LHCD experiments have been performed using the LHCD system of Tore Supra, composed of two different conceptual designs of launcher: the fully active multi-junction (FAM) and the new passive active multi-junction (PAM) antennas. A non-linear interaction between the electron density and the electric field has been characterized in a thin plasma layer in front of the two LHCD antennas. The resulting dependence of the power reflection coefficient (RC) with the LHCD power is not predicted by the standard linear theory of the LH wave coupling. A theoretical model is suggested to describe the non-linear wave–plasma interaction induced by the ponderomotive effect and implemented in a new full wave LHCD code, PICCOLO-2D (ponderomotive effect in a coupling code of lower hybrid wave-2D). The code self-consistently treats the wave propagation in the antenna vicinity and its interaction with the local edge plasma density. The simulation reproduces very well the occurrence of a non-linear behaviour in the coupling observed in the LHCD experiments. The important differences and trends between the FAM and the PAM antennas, especially a larger increase in RC for the FAM, are also reproduced by the PICCOLO-2D simulation. The working hypothesis of the contribution of the ponderomotive effect in the non-linear observations of LHCD coupling is therefore validated through this comprehensive modelling for the first time on the FAM and PAM antennas on Tore Supra. (paper)
Multi scale study of carbon deposits collected in Tore-Supra and TEXTOR tokamaks
International Nuclear Information System (INIS)
Richou, M.
2007-06-01
Tokamaks are devices aimed at studying magnetic fusion. They operate with high temperature plasmas containing hydrogen, deuterium or tritium. One of the major issue is to control the plasma-wall interaction. The plasma facing components are most often in carbon. The major drawback of carbon is the existence of carbon deposits and dust, due to erosion. Dust is potentially reactive in case of an accidental opening of the device. These deposits also contain H, D or T and induce major safety problems when tritium is used, which will be the case in ITER. Therefore, the understanding of the deposit formation and structure has become a main issue for fusion researches. To clarify the role of the deposits in the retention phenomenon, we have done different complementary characterizations for deposits collected on similar places (neutralizers) in tokamaks Tore Supra (France) and TEXTOR (Germany). Accessible microporous volume and pore size distribution of deposits has been determined with the analysis of nitrogen and methane adsorption isotherms using the BET, Dubinin-Radushkevich and α s methods and the Density Functional Theory (DFT). To understand growth mechanisms, we have studied the deposit structure and morphology. We have shown using Transmission Electron Microscopy (TEM) and Raman micro-spectrometry that these deposits are non amorphous and disordered. We have also shown the presence of nano-particles (diameter between 4 and 70 nm) which are similar to carbon blacks: nano-particle growth occurs in homogeneous phase in the edge plasma. We have emphasised a dual growth process: a homogenous and a heterogeneous one. (author)
Evolution of the Tore Supra Lower Hybrid Current Drive System for WEST
Energy Technology Data Exchange (ETDEWEB)
Delpech, Léna, E-mail: lena.delpech@cea.fr [CEA, IRFM, F-13108 St Paul-Lez-Durance (France); Achard, Joelle; Armitano, Arthur; Berger-By, Gilles; Ekedahl, Annika; Gargiulo, Laurent; Goniche, Marc; Guilhem, Dominique; Hertout, Patrick; Hillairet, Julien; Magne, Roland; Mollard, Patrick [CEA, IRFM, F-13108 St Paul-Lez-Durance (France); Piluso, P. [CNIM Industrial Systems, 83507 La Seyne-sur-Mer (France); Poli, Serge; Prou, Marc; Saille, Alain; Samaille, Franck [CEA, IRFM, F-13108 St Paul-Lez-Durance (France)
2015-10-15
Highlights: • Describe the state of the Lower Hybrid heating system for the WEST project. • Detailed the experiments to assess the coupling in WEST configuration. • Give the modifications required on the launchers to be adapted to WEST configuration. • Detailed the technical modifications with the CNIM company on the launchers. - Abstract: The WEST-project (W-tungsten Environment in Steady-state Tokamak) involves equipping Tore Supra with a full tungsten divertor, capable of withstanding heat load of 10 MW/m{sup 2} in steady-state conditions, in discharges sustained by Lower Hybrid Current Drive (LHCD). The LHCD generator, recently upgraded to deliver 9.2 MW/1000 s, is equipped with sixteen TH2103C klystrons powering two launchers. The WEST transformation involves reducing the plasma volume, thus moving the launchers ∼10 cm closer to the tokamak centre. The toroidal curvature of the launchers no longer fits the plasma curvature due to the strong magnetic field ripple effect, leading to a degradation of the LH wave coupling, especially with the Full Active Multijunction Launcher (FAM). The toroidal curvature radius of the FAM launcher mouth will therefore be reshaped from 1700 mm to 2300 mm. The machining process is described in this article. In order to improve the coupling of the LH wave, the local gas injection has been modified to help to meet the requirement of 7 MW/1000 s of LH power coupled to the plasma in the WEST scenarios. Finally, the curvature radius of the waveguide septa are rounded to minimize the excitation of suprathermal electrons near the plasma edge, which can induce high power loads on the plasma facing components.
High power lower hybrid current drive experiment in TORE SUPRA tokamak
International Nuclear Information System (INIS)
Peysson, Y.
2001-01-01
A review of the Lower Hybrid (LH) current drive experiments carried out on the TORE SUPRA tokamak is presented. This work highlights the issues for an effective application of the LH wave at high power in reactor relevant conditions. Very promising performances have been obtained with the new launcher that is designed to couple up to 4 MW during 1000 s at a power density of 25 MWm -2 . The heat load on the guard limiter of the antenna and the fast electron acceleration in the near electric field of the grill mouth remain at a low level, while the mean reflection coefficient never exceeds 10%. The powerful diagnosis capabilities of the hard x-ray (HXR) fast electron bremsstrahlung tomography has led to significant progresses in the understanding of the LH wave dynamics. The role of the fastest electrons driven by the LH wave is clearly identified. From HXR measurements, an increase of the LH current drive efficiency with the plasma current is predicted and confirmed by a direct determination at zero loop voltage. LH power absorption is observed to be off-axis in almost all plasma conditions, and its radial width clearly depends of antenna phasing conditions. A correlation between the HXR profiles and the onset of an improved core confinement is identified in fully non-inductive discharges. This regime ascribed to some vanishing of the magnetic shear is found to be transient and usually ends when the minimum of the safety factor becomes very close to 2, leading to a large MHD activity. Experimental observations and numerical simulations suggest that LH power is absorbed in a few number of passes. However, besides toroidal mode coupling, additional mechanisms may likely contribute to a spectral broadening to the LH wave. (author)
Energy Technology Data Exchange (ETDEWEB)
Houy, P
1999-10-15
The aim of this work is to propose a real-time control of the current profile in order to achieve reproducible operating modes with improved energetic confinement in tokamaks. The determination of the profile is based on measurements given by interferometry and polarimetry diagnostics. Different ways to evaluate and improve the accuracy of these measurements are exposed. The position and the shape of a plasma are controlled by the poloidal system that forces them to cope with standard values. Gas or neutral ions or ice pellet or extra power injection are technical means used to control other plasma parameters. These controls are performed by servo-controlled loops. The poloidal system of Tore-supra is presented. The main obstacle to a reliable determination of the current profile is the fact that slightly different Faraday angles lead to very different profiles. The direct identification method that is exposed in this work, gives the profile that minimizes the square of the margin between measured and computed values. The different algorithms proposed to control current profiles on Tore-supra have been validated by using a plasma simulation. The code Cronos that solves the resistive diffusion equation of current has been used. (A.C.)
International Nuclear Information System (INIS)
Lipa, M.; Blanchet, J.
2007-01-01
Full text of publication follows: Tore supra (TS) has used from the beginning of operation in 1989 actively cooled plasma facing components. Since the operation and baking temperature of all in vessel components has been defined to be up to 230 deg. C at 40 bars, a special water chemistry of the cooling water plant was suggested in order to avoid eventual water leaks due to corrosion (general corrosion, galvanic corrosion, stress corrosion, etc.) at relative high temperatures and pressures in tubes, pipes, bellows, water boxes, coils, etc. From the beginning of TS operation, in vessel components (e.g. wall protection panels, limiters, ergodic divertor coils, neutralisers and diagnostics) represented a unique combination of metals in the hydraulic circuit mainly such as stainless steel, Inconel, CuCrZr, Nickel and Copper. These different materials were joined together by welding (St to St, Inconel to Inconel, CuCrZr to CuCrZr and CuCrZr to St-St via a Ni sleeve adapter), brazing (St-St to Cu and Cu-LSTP), friction (CuCrZr and Cu to St-St), explosion (CuCrZr to St-St) and memory metal junction (Cryo-fit to Cu - only test sample). Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralized water with adjustment of the pH value to about 9.0/ 7.0 (25 deg. C/ 200 deg. C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 deg. C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal
Energy Technology Data Exchange (ETDEWEB)
Lipa, M.; Blanchet, J. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Cellier, F. [Framatome, Centre Technique, 71 - Saint Marcel (France)
2007-07-01
Full text of publication follows: Tore supra (TS) has used from the beginning of operation in 1989 actively cooled plasma facing components. Since the operation and baking temperature of all in vessel components has been defined to be up to 230 deg. C at 40 bars, a special water chemistry of the cooling water plant was suggested in order to avoid eventual water leaks due to corrosion (general corrosion, galvanic corrosion, stress corrosion, etc.) at relative high temperatures and pressures in tubes, pipes, bellows, water boxes, coils, etc. From the beginning of TS operation, in vessel components (e.g. wall protection panels, limiters, ergodic divertor coils, neutralisers and diagnostics) represented a unique combination of metals in the hydraulic circuit mainly such as stainless steel, Inconel, CuCrZr, Nickel and Copper. These different materials were joined together by welding (St to St, Inconel to Inconel, CuCrZr to CuCrZr and CuCrZr to St-St via a Ni sleeve adapter), brazing (St-St to Cu and Cu-LSTP), friction (CuCrZr and Cu to St-St), explosion (CuCrZr to St-St) and memory metal junction (Cryo-fit to Cu - only test sample). Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralized water with adjustment of the pH value to about 9.0/ 7.0 (25 deg. C/ 200 deg. C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 deg. C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal
International Nuclear Information System (INIS)
Diop, C.M'B.
1984-01-01
This thesis presents a global shielding calculation scheme for neutron and gamma rays arising from the Tokamak TORE SUPRA fusion device, in which a deuterium plasma is used. To study the shield parameters we have elabored a important chaining of neutron and gamma transport codes, TRIPOLI, ANISN, MERCURE 4, allowing to evaluate the radial and skyshine components of the dose rate behind the concrete shield. The study of thermonuclear neutron activation is fundamental to define a tokamak exploitation strategy. For this, two formalisme have been developed. They are based on a modelization of the activation reaction rates according to TRIPOLI, ANISN, and MERCURE 4 codes capabilities. The first one calculates, in one dimensional geometry, the desactivation gamma dose rate inside the vacuum chamber. The second one is a tridimensional model which determines the spatial variation of the gamma dose rate in the machine room. The problem of the existence of runaway electrons and associated secondaries radiations, bremsstrahlung gamma rays particularly, is approched. The results which are presented have contributed to define the parameters of the concrete shield and a strategy for TORE SUPRA Tokamak exploitation [fr
Experimental study of turbulence on Tore Supra by plasma micro-waves interaction
International Nuclear Information System (INIS)
Colas, L.
1996-01-01
Internal small-scale magnetic turbulence is a serious candidate to explain the anomalous heat transport in tokamaks. This turbulence is badly known in the gradient region of large machines. In this work internal magnetic fluctuations are measured on Tore Supra with an original diagnostic : Cross Polarization Scattering (CPS). This experimental tool relies on the Eigenmode change of a probing polarised microwave beam scattered by magnetic fluctuations, close to a cut-off layer for the incident wave. In this work, the diagnostic is first qualified to assess its sensitivity to magnetic fluctuations, and the spatial localisation for its measurements. The magnetic fluctuation behaviour is then analysed over a wide range of plasma current, density and additional power, and interpreted with a simple 1-D scattering model. A scan of the plasma density or magnetic field is used to move the CPS measurement location from r/a = 0.3 to r/a = 0.75. A fluctuation radial profile is obtained by two means. In L-mode discharges, the relation between magnetic fluctuations, temperature profiles and local heat diffusivities is investigated. With all measurements, it is also possible to look for a local parameter correlated to the turbulence in a large domain of plasma conditions. The fluctuation-induced local heat diffusivity expected from the measured fluctuations is estimated using the non-collisional quasi-linear formula: X mag e = πqRV te (δB / B) 2 . Both the absolute values and the parametric dependence of calculated X mag e are close to the electron thermal diffusivities Xe determined by transport analysis. In particular, a threshold is evidenced in the dependence of fluctuation-induced heat fluxes on local ∇T e , which is analogous to the critical gradient for measured heat fluxes. The experimental setup is also sensitive to the Thomson scattering of the probing wave by density fluctuations. Its measurements are analysed as the fluctuations of the amplitude and the phase of
Energy Technology Data Exchange (ETDEWEB)
Commaux, N
2007-09-15
The behaviour of a reactor-class plasma when fuelled using the existing techniques (gas puffing, supersonic molecular beam injection and pellet injection) is still very difficult to foresee. The present work has been initiated on Tore Supra in order to extrapolate the consequences of the different fuelling systems on ITER. Two main topics have been studied: the comparison of the plasma behaviour when fuelled using the different techniques at high Greenwald density fractions and the study of the homogenization following a pellet injection (main fuelling technique for ITER burning plasmas). The experiments at high Greenwald density fractions performed on Tore Supra showed that the plasma behaviour is very dependent on the fuelling method. The plasma energy confinement is following the scaling laws determined at low density when fuelled using pellet injection. which is better than for gas puffing and SMBI. both inducing a significant confinement loss. This behaviour is nor related to a transport modification: the ratio between effective diffusion and convection is similar to the pellet case. The difference between these shots is related only to the position of the matter source (at the edge for gas and close to the center for pellets). The study concerning the homogenization phenomena following a pellet injection aims mainly to study the {nabla}B-drift effect that expels the mater deposited by a pellet toward the low field side. A new phenomenon. which appears to be particularly important for the {nabla}B-drift during low field side injections. was then discovered: the influence of magnetic surfaces with an integer-valued safety factor (q). When the mater drifting toward low field side crosses an integer q surface. it experiences an important braking effect which stops the drift motion. It implies that the pellet material is mainly deposited on the last integer q surface crossed by the pellet during its injection. This study allows also to determine that the {nabla
International Nuclear Information System (INIS)
Hoang, G.T.; Bourdelle, C.; Pegourie, B.; Artaud, J.F.; Bucalossi, J.; Clairet, F.; Fenzi-Bonizec, C.; Garbet, X.; Gil, C.; Guirlet, R.; Imbeaux, F.; Lasalle, J.; Loarer, T.; Lowry, C.; Schunke, B.; Travere, J.M.; Tsitrone, E.
2003-01-01
These slides present some characteristics concerning peaked density profile observed in Tore-Supra. It appears that density profile remains peaked for more than 3 minutes in fully LHCD (lower hybrid current drive) discharges. The absence of toroidal electric field and the fact that the ware pinch has vanished across the entire plasma show that toroidal electric field and ware pinch are not the cause of the peaked profile. It is shown that peaked profile is linked to transport properties and can only be explained by a particle pinch velocity 2 orders of magnitude above the neoclassical pinch. It is also shown that the radial profile is in agreement with Isitchenko's formula. (A.C.)
International Nuclear Information System (INIS)
Kazarian, F.; Litaudon, X.; Moreau, D.; Arslanbekov, R.; Hoang, G.T.; Joffrin, E.; Peysson, Y.; Allibert, J.P.; Ane, J.M.; Bremond, S.
1995-01-01
The main objective of the Lower Hybrid (LH) experiments performed on Tore Supra is to provide large flux savings for long pulse operation while controlling the plasma current density profile. This goal will be best achieved by applying LH wave directly during the current ramp-up phase. Experiments have been performed where a large fraction of the current is driven non-inductively during the ramp-up phase. A theoretical flux consumption scaling is presented and compared to experimental data. The time evolutions of the current density profiles are analysed with a new current diffusion code (CRONOS). In view to achieve fully non-inductive current drive discharges in a fast, systematic and reproducible way, experiments where the primary voltage is imposed have been carried out. In a complementary approach, an appropriate transformer flux feedback scheme has been also studied. (author) 6 refs.; 6 figs
International Nuclear Information System (INIS)
Tsitrone, E.; Reiter, D.; Loarer, T.; Brosset, C.; Bucalossi, J.; Begrambekov, L.; Grisolia, C.; Grosman, A.; Gunn, J.; Hogan, J.; Mitteau, R.; Pegourie, B.; Ghendrih, P.; Reichle, R.; Roubin, P.
2005-01-01
In Tore Supra long pulses, particle balance gives evidence that a constant fraction of the injected gas (typically 50%) is retained in the wall for the duration of the shot, showing no sign of wall saturation after more than 6 min of discharge. During the discharge, the retention rate first decreases (phase 1), then remains constant throughout the pulse (phase 2). Phase 1 could be interpreted as implantation of particles combined with a constant codeposition rate, while phase 2 could correspond to codeposition alone, once the implanted surfaces are saturated with deuterium. This paper presents a possible contribution of charge exchange neutrals to the implantation process, based on modelling results with the Eirene neutral transport code. A complex pattern of particle implantation is evidenced, with saturation time constants ranging from less than one to several hundreds seconds, compatible with the experimental behaviour during phase 1
International Nuclear Information System (INIS)
Wauters, T.; Douai, D.; Lyssoivan, A.; Philipps, V.; Bremond, S.; Freisinger, M.; Kreter, A.; Lombard, G.; Marchuk, O.; Mollard, P.; Paul, M.K.; Pegourie, B.; Reimer, H.; Sergienko, G.; Tsitrone, E.; Vervier, M.; Van Wassenhove, G.; Wuenderlich, D.; Van Schoor, M.; Van Oost, G.
2011-01-01
This contribution reports on isotope exchange studies with both Ion Cyclotron Wall Conditioning (ICWC) and Glow Discharge Conditioning (GDC) in TEXTOR and TORE SUPRA. The discharges have been carried out in H 2 , D 2 (ICWC and GDC) and He/H 2 mixtures (ICWC). The higher reionization probability in ICWC compared to GDC, following from the 3 to 4 orders of magnitude higher electron density, leads to a lower pumping efficiency of wall desorbed species. GDC has in this analysis (5-10) times higher removal rates of wall desorbed species than ICWC, although the wall release rate is 10 times higher in ICWC. Also the measured high retention during ICWC can be understood as an effect of the high reionization probability. The use of short RF pulses (∼1 s) followed by a larger pumping time significantly improves the ratio of implanted over recovered particles, without severely lowering the total amount of removed particles.
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Fenzi, C.; Devynck, P.; Garbet, X.; Antar, G.; Capes, H.; Laviron, C.; Truc, A.; Gervais, F.; Hennequin, P.; Quemeneur, A.
1999-01-01
In magnetic fusion devices, the effect of plasma facing components on plasma turbulence is a key issue for several reasons. Firstly, the edge turbulence controls the power deposition on plasma facing components. Secondly, the possible influence of the edge parameters on the core fluctuations is a central question, since the core turbulent transport is responsible for the confinement degradation. It is in practice difficult to determine whether the plasma core influences the edge, or the opposite. We show here that spatial edge asymmetries of density fluctuations, and particularly up-down asymmetries, provide a powerful tool to investigate this problem. In TORE SUPRA, previous scaling analyses with various plasma parameters have emphasized that a very clear effect on the asymmetry level appears when the plasma leans on the lower modular limiter located close to the measurement chord. We present here recent measurement results concerning that specific case. They tend to show that the limiter configuration has some effect on the core turbulence. (authors)
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Colas, L.; Paume, M.; Zou, X.L.; Chareau, J.M.; Guiziou, L.; Hoang, G.T.; Michelot, Y.; Gresillon, D.
1997-03-01
Magnetic fluctuations (radial size ∼ 5 mm) are measured by a cross polarisation scattering (CPS) diagnostic in TORE SUPRA. These fluctuations are investigated quantitatively in the ohmic and low confinement regimes over a wide range of plasma currents, densities and additional heating powers. Simultaneously, electron heat diffusivities expected from these fluctuations are compared to those obtained by profile analysis. A radial profile of the magnetic fluctuations in the gradient region ( 0.3 e mag = πqRv th (δ B r / B) 2 . Both the order of magnitude and the parametric dependence of χ e mag show similarities with electron diffusivities determined by transport analysis. In particular, a threshold is observed for the dependence of fluctuation-induced heat fluxes on the local temperature gradient, which is close to the critical gradient observed for the measured heat fluxes. (author)
Progress report of the Research Group. 1st part: Tore Supra. 2nd part: Fontenay-aux-Roses
International Nuclear Information System (INIS)
1981-01-01
Three major events dominated the activities of the EURATOM/CEA association during 1980: the decision to launch the realization of the TORE SUPRA project, the progressive recognition of high frequency heating as a solution for the future, and the increasing support given to the development of heating methods and diagnostics in the JET project. It is estimated that project studies are sufficiently advanced and that industrial fabrication problems have been sufficiently covered for the realization of Tore Supra to begin in 1981. One of the successes of the work carried out is the complete validation for the superfluid helium cooling system. The satisfactory development of high frequency heating and the increasing credibility of this form of heating for future work are very important factors. In this context, the decision of the JET to envisage a large amount of ionic cyclotron heating is particularly important. The results obtained in 1980 are in fact very encouraging. The maximum power of the 500 kW T.F.R. generator was coupled with the plasma and it was possible to establish an energy Q-value. Even though the injection of neutral particles can now be considered as a proved heating method, studies of the accompanying physical phenomena are still important. The T.F.R. experiments carried out in this field in 1980 were very useful. The importance of the realization and development activities conducted during 1980, should not mask the enormous effort that made, both experimentally and theoretically, in order to understand key physical phenomena in plasma. The main peoccupation concerned small and large disruptions and all aspects of the associated instabilities. A detailed analysis of the experimental results using numerical models has led to improved empirical knowledge on the elementary transport phenomena taking place. Increasingly detailed studies on microinstabilities were also fruitful and have even led to a complete reversal in some of the ideas held about the
Energy Technology Data Exchange (ETDEWEB)
Gomez, P
1999-12-01
This thesis aims at characterizing the dynamics of fast electrons generated by the Landau absorption of the hybrid wave and studying their effects on electron cyclotron radiation. The different processes involved in the propagation and resonant absorption of the hybrid wave in plasmas are described. A method such as ray-tracing allows the characterization of the dynamics of heating but this method relies on the hypothesis of geometrical optics. Whenever absorption rate is low as it is in Tore-Supra, the hybrid wave undergoes a series of successive reflections on the edge of the plasma before being completely absorbed. These reflections generate an electromagnetic chaos in which geometrical optics hypothesis are no longer valid. A statistical treatment of the Fokker-Planck equation allows the calculation of the mean distribution function of electrons in the plasma submitted to hybrid wave. The electron cyclotron radiation is then deduced and by assuming that plasma behaves like a black body, a theoretical radiative temperature is calculated. The confrontation of this theoretical temperature profile with experimental values allows the validation of this modeling and the estimation of the effects of fast electrons on temperature measurements. (A.C.)
Contributions to the design and to the fabrication of the magnet of the toroidal field of Tore Supra
International Nuclear Information System (INIS)
Turck, B.
1992-03-01
This report is a collection of published papers in French and in English about the design and the qualification of the magnet of the toroidal field of Tore Supra. The development test programme, the controls during conductor manufacturing and the acceptance tests have shown to be the bases for achieving a very low level of rejection for the whole production. A systematic study of the performances correlated to the fabrication conditions has provided valuable informations for the optimization of the manufacturing processes of superconductors. The tests of single coils have enabled the commissioning of a monitoring and protection system specially adapted for this magnet of 18 coils cooled in a superfluid helium bath. After the accident caused by an arcing in one coil of the Torus, and the replacement of the faulty coil, the monitoring and safety discharge system have been adapted. The current in the magnet has been increased up to 1 455 A for 9.3 T on the conductors (nominal values 1 400 A and 9 T). During the last three years (1989-1991) only one transition to normal state has been observed in one coil strongly irradiated after a severe plasma disruption. In these conditions the protection system acted very well and as expected
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Nygren, R.; Koski, J.; Lutz, T.; McGrath; Miller, J.; Watkins, J.; Guilhem, D.; Chappuis, P.; Cordier, J.; Loarer, T.
1995-01-01
Tore Supra's Phase III outboard pump limiter (OPL) is a modular actively-cooled mid-plane limiter, designed for heat and particle removal during long pulse operation. During its initial operation in 1993, the OPL successfully removed about 1 MW of power during ohmicly heated shots of up to 10 s duration and reached (steady state) thermal equilibrium. The particle pumping of the Phase III OPL was found to be about 50% greater than the Phase II OPL which had a radial distance between the last closed flux surface and the entrance of the pumping throat of 3.5 cm compared with only 2.5 cm for the Phase III OPL. This paper gives examples of power distribution over the limiter from IR measurements of surface temperature and from extensively calorimetry (34 thermocouples and 10 flow meters) and compares the distributions with values predicted by a 3D model (HF3D) with a detailed magnetic configuration (e.g., includes field ripple). ((orig.))
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Gunn, J.P.; Boucher, C.; Dionne, M.; Duran, I.; Fuchs, V.; Loarer, T.; Nanobashvili, I.; Panek, R.; Pascal, J.-Y.; Saint-Laurent, F.; Stoeckel, J.; Rompuy, T. van; Zagorski, R.; Adamek, J.; Bucalossi, J.; Dejarnac, R.; Devynck, P.; Hertout, P.; Hron, M.; Lebrun, G.; Moreau, P.; Rimini, F.; Sarkissian, A.; Oost, G. van
2007-01-01
Near-sonic parallel flows are systematically observed in the far scrape-off layer (SOL) of the limiter tokamak Tore Supra, as in many L-mode X-point divertor tokamak plasmas. The poloidal variation of the parallel flow has been measured by moving the contact point of a small circular plasma onto limiters at different poloidal angles. The resulting variations of flow are consistent with the existence of a poloidally localized enhancement of radial transport concentrated in a 30 deg. sector near the outboard midplane. If the plasma contact point is placed on the inboard limiters, then the SOL expands to fill all the space between the plasma and the outboard limiters, with density decay lengths between 10 and 20 cm. On the other hand, if the contact point lies on the outboard limiters, the localized plasma outflux is scraped off and the SOL is very thin with decay lengths around 2-3 cm. The outboard radial transport would have to be about two orders of magnitude stronger than inboard to explain these results
International Nuclear Information System (INIS)
Litaudon, X.; Peysson, Y.; Aniel, T.; Huysmans, G.; Imbeaux, F.; Joffrin, E.; Lasalle, J.; Lotte, Ph.; Schunke, B.; Segui, J.; Tresset, G.; Zabiego, M.
2000-12-01
The formation of a core region with improved electron confinement is reported in the recent full current drive operation of Tore Supra where the plasma current is sustained with the Lower Hybrid, LH, wave. Current profile evolution and thermal electron transport coefficients are directly assessed using the data of the new fast electron Bremsstrahlung tomography that provides the most accurate determination of the LH current and power deposition profiles. The spontaneous rise of the core electron temperature observed a few seconds after the application of the LH power is ascribed to a bifurcation towards a state of reduced electron transport. The role of the magnetic shear is invoked to partly stabilize the anomalous electron turbulence. The electron temperature transition occurs when the q-profile evolves towards a non-inductive state with a non-monotonic shape i.e. when the magnetic shear is reduced close to zero in the plasma core. The improved core confinement phase is often terminated by a sudden MHD activity when the minimum q approaches two. (authors)
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Vezinet, D.; Mazon, D.; Malard, P.
2013-01-01
This paper presents an experimental protocol for absolute calibration of photo-detectors. Spectral characterization is achieved by a methodology that unlike the usual line emissions-based method, hinges on the Bremsstrahlung radiation of a Soft X-Ray (SXR) tube only. Although the proposed methodology can be applied virtually to any detector, the application presented in this paper is based on Tore Supra's SXR diagnostics, which uses Silicon Surface Barrier Diodes. The spectral response of these n-p junctions had previously been estimated on a purely empirical basis. This time, a series of second-order effects, like the spatial distribution of the source radiated power or multi-channel analyser non linearity, are taken into account to achieve accurate measurements. Consequently, a parameterised physical model is fitted to experimental results and the existence of an unexpected dead layer (at least 5 μm thick) is evidenced. This contribution also echoes a more general on-going effort in favour of long-term quality of passive radiation measurements on Tokamaks
Boundary plasma control with the ergodic divertor
International Nuclear Information System (INIS)
Ghendrih, Ph.; Becoulet, M.; Beyer, P.
1999-01-01
Ergodic divertor experiments on Tore Supra provide evidence of significant control of plasma-wall interaction. Theoretical investigation of the laminar region (i.e. governed by parallel transport) indicates that control of the plasma state at the target plate can be achieved with plasma states similar to that observed with the axisymmetric divertor. Analysis of the temperature field with a 2-D test particle code allows one to recover the observed spatial modulation and shows that an intrinsic barrier appears to develop at the separatrix. Energy deposition peaking, analysed with a 3-D code, is strongly reduced when moderate transverse transport is considered. Possible control of upstream parameters can thus be achieved in the ergodic region, for instance a lowering of the parallel energy flux by cross field transport. (author)
Boundary plasma control with the ergodic divertor
International Nuclear Information System (INIS)
Ghendrih, Ph.; Becoulet, M.; Beyer, P.
2001-01-01
Ergodic divertor experiments on Tore Supra provide evidence of significant control of plasma-wall interaction. Theoretical investigation of the laminar region (i.e. governed by parallel transport) indicates that control of the plasma state at the target plate can be achieved with plasma states similar to that observed with the axisymmetric divertor. Analysis of the temperature field with a 2-D test particle code allows one to recover the observed spatial modulation and shows that an intrinsic barrier appears to develop at the separatrix. Energy deposition peaking, analysed with a 3-D code, is strongly reduced when moderate transverse transport is considered. Possible control of upstream parameters can thus be achieved in the ergodic region, for instance a lowering of the parallel energy flux by cross field transport. (author)
Energy Technology Data Exchange (ETDEWEB)
Bregeon, R
1999-03-01
In Tokamak plasma physics, current profile shaping has now become a key issue to improve the confinement properties of the plasma discharge. The objective of this work is to study the processes governing the current diffusion when non-inductive current are playing a major role in the discharge. Ultimately, this study aims to identify the key parameters to control the plasma current density profile with external current drive heating systems such as Lower Hybrid Current drive (LHCD) or self generated current drive such as the bootstrap current. Principles of non inductive current drive and heating systems are introduced as well as bootstrap current mechanisms. Then we present the experimental study of plasma parallel electric conductivity to validate existing models. Using these results, the poloidal magnetic field flux diffusion is modelled, using toroidal co-ordinates in order to give an accurate description of the current density profiles evolution. The initial and boundary conditions required for numerical resolution of the diffusion equation are also presented. Finally, we conclude this work with the simulations of two discharges: one with Fast Wave Electron Heating and the second using Lower Hybrid Current Drive. These simulations have multiples aims: validity test of our numerical tool and to show some limits of cylindrical models. Test of electric conductivity and bootstrap current models. To identify the key parameters involved in the current diffusion processes of a high performance plasma discharge on Tore Supra. Such simulations are crucial to determine the amount of non-inductive current required to control and sustain long plasma discharges in steady state. (author)
Energy Technology Data Exchange (ETDEWEB)
Cristofani, P.
1996-02-12
In order to increase the temperature, density and confinement time of the plasma energy inside tokamak devices, several heating and fuel injection techniques have been used. However, the increase of the energy content of the central part of the plasma leads to instabilities in the confinement magnetic structure which can degrade the confinement properties and the temperature performances. Inside the plasma, the ``q=1`` surface plays an important role in the confinement process. The aim of this thesis is to study the experimental physics related to this surface with the analysis of the ``saw-tooth`` periodical internal relaxations and of the ``snake`` structure. The first chapter gives a general introduction about thermonuclear fusion and a description of the plasma and of its equilibrium. Chapter 2 is devoted to the description of the soft X-ray tomography, the diagnostic technique used in this work. In chapter 3, a theoretical presentation of plasma stability and a comparison with experimental results obtained in the Tore-Supra tokamak are given. The observations of saw-tooth instabilities are presented with the principal theoretical models which are used to explain this phenomenon. The snake density instability localized in the central part of the plasma is described in chapter 4 with an attempt of interpretation. The equation of the size evolution of a magnetic island was modified to test different models which can explain the snake stability. One model is based on the modification of the bootstrap current induced by the presence of the snake, and on the local modification of the current induced by the accumulation of impurities inside the snake. (J.S.). 107 refs.
Energy Technology Data Exchange (ETDEWEB)
Courtois, L
2001-03-09
Electron cyclotron resonance heating (ECRH) in the Tore Supra tokamak constitutes an important step in the research aimed at obtaining thermonuclear fusion reactions. Electron heating is achieved by transmitting an electromagnetic wave from the oscillators (gyrotrons) to the plasma via the fundamental mode, propagating in oversized corrugated waveguides. Maximizing the proportion of the gyrotron power coupled to the fundamental waveguide mode is essential for the good functioning of the transmission line and for maximizing the effect on the plasma. This thesis gives all necessary tools for finding the proportion of the fundamental mode and all other modes present in passive components and at the output of the gyrotron as installed in the Tore Supra ECRH plant. This characterisation is based on obtaining amplitude and phase diagrams of the electric field on a plane transverse to the propagation axis. The most difficult part of obtaining these diagrams is measuring the phase which, despite the very short wavelength, is measured directly at low power levels. At high power levels the phase is numerically reconstructed from amplitude measurements for gyrotron characterisation. A complete theoretical study of the phase reconstruction code is given including its validation with theoretical diagrams. This study allows the realisation of a modal characterisation unit electromagnetic for measurement of radiated beams and usable in each part of the ECRH installation. At the end, the complete modal characterisation is given at low level for a mode converter and also at high level for the first series gyrotron installed at TORE SUPRA. (author)
M.H.D. activity associated with the q=1 surface in the Tore-Supra tokamak
International Nuclear Information System (INIS)
Cristofani, P.
1996-01-01
In order to increase the temperature, density and confinement time of the plasma energy inside tokamak devices, several heating and fuel injection techniques have been used. However, the increase of the energy content of the central part of the plasma leads to instabilities in the confinement magnetic structure which can degrade the confinement properties and the temperature performances. Inside the plasma, the ''q=1'' surface plays an important role in the confinement process. The aim of this thesis is to study the experimental physics related to this surface with the analysis of the ''saw-tooth'' periodical internal relaxations and of the ''snake'' structure. The first chapter gives a general introduction about thermonuclear fusion and a description of the plasma and of its equilibrium. Chapter 2 is devoted to the description of the soft X-ray tomography, the diagnostic technique used in this work. In chapter 3, a theoretical presentation of plasma stability and a comparison with experimental results obtained in the Tore-Supra tokamak are given. The observations of saw-tooth instabilities are presented with the principal theoretical models which are used to explain this phenomenon. The snake density instability localized in the central part of the plasma is described in chapter 4 with an attempt of interpretation. The equation of the size evolution of a magnetic island was modified to test different models which can explain the snake stability. One model is based on the modification of the bootstrap current induced by the presence of the snake, and on the local modification of the current induced by the accumulation of impurities inside the snake. (J.S.)
Energy Technology Data Exchange (ETDEWEB)
Delchambre, E
2004-03-01
< 40 {mu}m. These results are confirmed by the laser ablation experiment's on CFC of A. Hermann et al. in which it is inferred that the size of hot spots is less than the 30 {mu}m spatial resolution of the IR camera which is used. Additional results are exhibited describing the micro-analysis of deposition samples removed from Tore Supra. The analyses have shown that the characteristics forms are due to deposition process and not to in situ surface alterations. The deposition is characterized and a ballistic model for the observed orientation and morphology is proposed and the global growth rate of these samples is evaluated. Correlations with the evolution of the infrared emission spectrum have been made, outlining the sequence of layer growth and the corresponding spectral deformation characteristics. (author)
International Nuclear Information System (INIS)
Cai Laizhong; Gauthier, Eric; Corre, Yann; Loarer, Thierry; Missirlian, Marc; Martin, Vincent; Moncada, Victor
2012-01-01
The bonding of plasma-facing component (PFC) tiles and their possible defects need to be monitored to evaluate the safety during long pulse plasma operations and prevent critical failure, which is very important for ITER and next-step fusion devices. The defect evolutions of two toroidal pumped limiter (TPL) tiles are investigated by analysing the infrared images obtained during Tore Supra experiments from 2006 to 2010 (about 10 000 plasma discharges). The evolution of the defect is characterized by the surface temperature reached in stationary discharge conditions. The comparison of the defect tiles with neighbouring tiles (with no defect) and the evolutions are carried out through the thermal time constants of the tiles. The results show that the two tiles are slowly deteriorating during plasma operation and no plateau of the deterioration is observed in the considered period. By comparing the defect evolutions with the modelling results calculated by CAST3M, the current state of the defect tiles is identified. The defects are significant (about 30% of the tile length or area) and need to be followed and monitored further in the next experimental campaigns of Tore Supra.
International Nuclear Information System (INIS)
Van Houtte, D.; Martin, G.; Becoulet, A.; Saoutic, B.
2004-01-01
The experimental programme of Tore Supra (a = 0.72 m, R = 2.4 m, I p T < 4.5 T) has been devoted in 2003 to study simultaneously heat removal capability and particle exhaust in steady-state fully non-inductive current drive discharges. This required both advanced technology integration and steady-state real time plasma control. In particular, an improvement of the plasma position within a few millimetre range, and new real time cross controls between radio frequency (RF) power and various actuators built around a shared memory network, have allowed Tore Supra to access a powerful steady-state regime with an improved safety level for the actively cooled plasma facing components. Feedback controlled fully non-inductive plasma discharges have been sustained in a steady-state regime up to 6 minutes with a new world record of injected-extracted energy exceeding 1 GJ. Advanced tools, experimental results and brief physics analysis of these discharges are presented and discussed. (authors)
Tore Supra: technical description
International Nuclear Information System (INIS)
1985-08-01
This report volume is devoted to system composed of vacuum vessel and thermal shields, and to poloidal field system. Mocks realized to study feasibility and structure properties are presented, mechanical calculations (with different cases of static and dynamic loads for vacuum vessel) are resumed, first wall components are described. Techniques designed to dissipate plasma power, to control recycling and maintain a good impuritiy rate are examined. Principal fabrication process are described together with pumping systems; and control of pumping circuits. For poloidal field, electrical power supplies, operation and use priciples, field coils and magnetic circuits are described [fr
International Nuclear Information System (INIS)
Maget, P.; Luetjens, H.; Huysmans, G.; Moreau, Ph.; Schunke, B.; Segui, J.-L.; Garbet, X.; Joffrin, E.; Luciani, J.F.
2007-01-01
The early phase of a tokamak plasma discharge can have a dramatic impact on the main heating phase. This has been a persistent problem for the development of the steady state, fully non-inductive scenario using lower hybrid current drive (LHCD) on Tore Supra. The present paper reports on recent experimental and numerical investigations showing that a tearing mode coupled to the internal kink grows on q = 2 in the ohmic phase when the total current is too low, due to the weakening of field line curvature stabilization. Then, the application of LHCD drives the island to a larger size and undermines the development of the non-inductive phase. Decreasing the edge safety factor or increasing the Lundquist number S is found to be beneficial in both the linear and non-linear MHD analyses. The experimental database, which allows covering the edge safety factor dependence, supports this interpretation
International Nuclear Information System (INIS)
Schlosser, J.; Chappuis, P.; Chatelier, M.; Durocher, A.; Guilheim, D.; Lipa, M.; Mitteau, R.; Tonon, G.; Tsitrone, E.
1998-01-01
Actively cooled plasma facing components (PFC) have been developed and used in Tore Supra since 1985. One of the main technological problem is due to the expansion mismatch between graphite armour and metallic heat sink material. A first technology used graphite tiles with or without a reinforcement and a compliant layer, brazed with titanium copper-silver (TiCuAg) alloy. The next technology used carbon fiber material (CFC) tiles with a 2 mm pure copper compliant layer, since the good mechanical strength of the CFC allowed the reinforcement layer to be suppressed. No destructive inspection during the manufacturing procedure was found to be essential to insure a good reliability of the elements. (orig.)
Martin, E. H.; Goniche, M.; Klepper, C. C.; Hillairet, J.; Isler, R. C.; Bottereau, C.; Colas, L.; Ekedahl, A.; Panayotis, S.; Pegourie, B.; Lotte, Ph; Colledani, G.; Caughman, J. B.; Harris, J. H.; Hillis, D. L.; Shannon, S. C.; Clairet, F.; Litaudon, X.
2015-06-01
Interaction of radio-frequency (RF) waves with the plasma in the near-field of a high-power wave launcher is now seen to be an important topic, both in understanding the channeling of these waves through the plasma boundary and in avoiding power losses in the edge. In a recent Letter, a direct non-intrusive measurement of a near antenna RF electric field in the range of lower hybrid (LH) frequencies (ELH) was announced (2013 Phys. Rev. Lett. 110 215005). This measurement was achieved through the fitting of Balmer series deuterium spectral lines utilizing a time dependent (dynamic) Stark effect model. In this article, the analysis of the spectral data is discussed in detail and applied to a larger range of measurements and the accuracy and limitations of the experimental technique are investigated. It was found through an analysis of numerous Tore Supra discharges that good quantitative agreement exists between the measured and full-wave modeled ELH when the launched power exceeds 0.5 MW. For low power the measurement becomes inaccurate utilizing the implemented passive spectroscopic technique because the spectral noise overwhelms the effect of the RF electric field on the line profile. Additionally, effects of the ponderomotive force are suspected at sufficiently high power.
Boundary layer physics considerations for the TEXTOR dynamic ergodic divertor experiment
Energy Technology Data Exchange (ETDEWEB)
Evans, T.E. [General Atomics, San Diego, CA (United States)
1997-09-01
The proposed arrangement of the TEXTOR dynamic ergodic divertor coils is quite different from that of previous stochastic boundary layer experiments. These coils are located on the high field side and have continuous helical windings. The basic resonant magnetic field line structure is not substantially affected by the location of the perturbation coils but the non-resonant near field effects, such as those related to helical divertor effects and the interaction of the near field with the stochastic layer, are different. Differences with the TORE SUPRA ergodic divertor coils are discussed. Based on these differences we expect that the plasma positioning will play an important role in: (i) the onset of MARFE`s; (ii) the impurity screening efficiency; (iii) the onset of disruptions; and (iii) the transport properties of the boundary layer plasma. (orig.) 17 refs.
Energy Technology Data Exchange (ETDEWEB)
Kazarian-Vibert, F.
1996-07-05
Lower Hybrid Current Drive in tokamak plasmas allows to obtain continuous operations, which constitute a necessary step towards a definition of a thermonuclear fusion reactor. The objectives of this work is to define and study fully non inductive steady-state scenarios on Tore Supra. The current diffusion equation is solved to determined precisely the inductive and non inductive current density profiles and their influence on thee time evolution of a discharge. Then, a new operation mode is studied theoretically and experimentally. In this scenario, the transformer primary circuit voltage is controlled in such a way that the flux consumption vanishes. It allows to achieve full steady-state discharges in a fast and reproducible manner. A theoretical flux consumption scaling law during plasma current ramp-up assisted by Lower-Hybrid waves is presented and validated by experimental data, in view to minimized this consumption. The influence of a non monotonic current profile on the confinement and the transport of energy in the plasma is also clearly illustrated by experiments. (author). 138 refs., 16 figs., 1 tab.
Energy Technology Data Exchange (ETDEWEB)
Fenzi, Ch
1999-10-29
In magnetic fusion devices, the optimisation of the power deposition profile on plasma facing components crucially depends on the heat diffusivity across the magnetic field fines, which is determined by the plasma edge turbulence. In this regard, spatial asymmetries of plasma edge turbulence are of great interest. In this work, we interest in up-down asymmetries of density fluctuations which are usually observed in Tore Supra, using a coherent light scattering experiment. It is shown that these asymmetries are correlated to the plasma edge geometrical configuration (plasma facing components, limiters). In fact, the plasma-limiter interaction induces locally in the plasma edge and the SOL (r/a > 0.9) an additional turbulence with short correlation length along the magnetic field fines, which spreads in the plasma core (0.9 {>=} r/a {>=} 0.5). The resultant up-down asymmetry weakly depends on density, increases with the edge safety factor, and inverts when the plasma current direction is reversed. Such up-down asymmetry observations bring strong impact on edge turbulence and transport models, which usually predict a ballooning of the turbulence in the high-field side but not an up-down asymmetry. A possible model is proposed here, based on the Kelvin Helmholtz instability. (author)
TORE SUPRA neutral injection system
International Nuclear Information System (INIS)
Bayetti, P.; Becherer, R.; Bottiglioni, F.; Jacquot, C.; Jequier, F.; Fumelli, M.; Lotte, P.; Pamela, J.; Sledziewski, Z.
1989-01-01
The Neutral Beam Injection on TS consists of three boxes, each housing two injectors. Each of them is designed to accelerate 40 A at 100 kV in D 2 ar 40A at 80 kV in H 2 , in shots of 30 s. The power on the plasma is expected to be 7.5 MW (full energy) and 9 MW (total) for the D-beams; 2.5 MW and 3.8 MW for H-beams. This for a species mix of 0.85 19 m -2 and a transmission efficiency of 0.7. Four injectors are in co and two through another one, and they are tilted of 20 deg from the radial direction. Injectors are designed for the energy recovery of the full energy ions. A prototype line, operated in 1987-88, has given the imput for the demensioning of the present system.First injectors are expected to be operational by the end of 1988. The present contribution describes the injection boxes, injection line, magnetic shielding, electrical circuity and power supplies, control and data acquisition systems, and the Fast Interlock Safety System (FISS). 7 refs.; 6 figs
Vector Valued Martingale-Ergodic and Ergodic-Martingale Theorems
Shahidi, Farruh; Ganiev, Inomjon
2012-01-01
We prove martingale-ergodic and ergodic-martingale theorems for vector valued Bochner integrable functions. We obtain dominant and maximal inequalities. We also prove weighted and multiparameter martingale-ergodic and ergodic martingale theorems.
New Tore Supra steady state operating scenario
International Nuclear Information System (INIS)
Martin, G.; Parlange, F.; van Houtte, D.; Wijnands, T.
1995-01-01
This document deals with plasma control in steady state conditions. A new plasma control systems enabling feedback control of global plasma equilibrium parameters has been developed. It also enables to operate plasma discharge in steady state regime. (TEC). 4 refs., 5 figs
Halmos, Paul R
2017-01-01
This concise classic by a well-known master of mathematical exposition covers recurrence, ergodic theorems, ergodicity and mixing properties, and the relation between conjugacy and equivalence. 1956 edition.
The division of plasma physics
International Nuclear Information System (INIS)
Evans, T.E.; Guilhem, D.; Klepper, C.C.
1990-07-01
The investigations presented in the 31th meeting on plasma physics were: the main results and observations during the ergodic divertor experiments in Tore Supra tokamak; the modifications of power scrape-off-length and power deposition during various configurations in Tore Supra plasmas; the results of pressure measurements and particle fluxes in the Tore Supra pump limiter
Nadkarni, M G
2013-01-01
This is an introductory book on Ergodic Theory. The presentation has a slow pace and the book can be read by any person with a background in basic measure theory and metric topology. A new feature of the book is that the basic topics of Ergodic Theory such as the Poincare recurrence lemma, induced automorphisms and Kakutani towers, compressibility and E. Hopf's theorem, the theorem of Ambrose on representation of flows are treated at the descriptive set-theoretic level before their measure-theoretic or topological versions are presented. In addition, topics around the Glimm-Effros theorem are discussed. In the third edition a chapter entitled 'Additional Topics' has been added. It gives Liouville's Theorem on the existence of invariant measure, entropy theory leading up to Kolmogorov-Sinai Theorem, and the topological dynamics proof of van der Waerden's theorem on arithmetical progressions.
Coupling structure calculations for ion cyclotron heating of Tore Supra
International Nuclear Information System (INIS)
Bannelier, P.
1986-12-01
Two structures are studied: antennas and waveguides. After some recalls on transmission lines with losses, the theory is applied to antennas with inner adaptation: the problem is to calculate the impedance necessary for complete adaptation of antenna to the power line and the generator. The Faraday screen role is detailed and studied: the per-unit length loss resistance due to ohmic losses in the screen which lower the plasma-coupled maximum power. Waveguide coupling theory is also presented. Coupling between wave guide and plasma is evaluated [fr
Scrape-off layer flows in the Tore Supra tokamak
Czech Academy of Sciences Publication Activity Database
Gunn, J. P.; Boucher, C.; Dionne, M.; Ďuran, Ivan; Fuchs, Vladimír; Loarer, T.; Pánek, Radomír; Saint Laurent, F.; Stöckel, Jan; Adámek, Jiří; Bucalossi, J.; Dejarnac, Renaud; Devynck, P.; Hertout, P.; Hron, Martin; Nanobashvili, I.; Rimini, F.G.; Sarkissian, A.
2006-01-01
Roč. 812, - (2006), s. 27-34 ISSN 0094-243X. [AIP Conference Proceedings. Opole-Turawa, 06.09.2006-09.09.2006] R&D Projects: GA ČR GP202/03/P062 Institutional research plan: CEZ:AV0Z20430508 Keywords : tokamak * scrape-off layer * plasma flow * radial transport * Mach probe Subject RIV: BL - Plasma and Gas Discharge Physics http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=812&Issue=1
Plasma turbulence measured by fast sweep reflectometry on Tore Supra
International Nuclear Information System (INIS)
Clairet, F.; Vermare, L.; Leclert, G.
2004-01-01
Traditionally devoted to electron density profile measurement we show that fast frequency sweeping reflectometry technique can bring valuable and innovative measurements onto plasma turbulence. While fast frequency sweeping technique is traditionally devoted to electron density radial profile measurements we show in this paper how we can handle the fluctuations of the reflected signal to recover plasma density fluctuation measurements with a high spatial and temporal resolution. Large size turbulence related to magneto-hydrodynamic (MHD) activity and the associated magnetic islands can be detected. The radial profile of the micro-turbulence, which is responsible for plasma anomalous transport processes, is experimentally determined through the fluctuation of the reflected phase signal. (authors)
Plasma turbulence measured by fast sweep reflectometry on Tore Supra
International Nuclear Information System (INIS)
Clairet, F.; Vermare, L.; Heuraux, S.; Leclert, G.
2004-01-01
Traditionally devoted to electron density profile measurement we show that fast frequency sweeping reflectometry technique can bring valuable and innovative measurements onto plasma turbulence. While fast frequency sweeping technique is traditionally devoted to electron density radial profile measurements we show in this paper how we can handle the fluctuations of the reflected signal to recover plasma density fluctuation measurements with a high spatial and temporal resolution. Large size turbulence related to magneto-hydrodynamic (MHD) activity and the associated magnetic islands can be detected. The radial profile of the micro-turbulence, which is responsible for plasma anomalous transport processes, is experimentally determined through the fluctuation of the reflected phase signal
Recent results on current profile shaping on tore supra
Energy Technology Data Exchange (ETDEWEB)
Becoulet, A.
1994-12-31
The link between the current profile and the confinement is studied, involving various regimes: high power minority ion cyclotron resonant heating, high power lower hybrid current drive, fast wave direct electron heating and current drive and pellet enhanced performance. It is shown that the electron heat diffusivity decreases when the magnetic shear increases in the confinement zone and/or when it decreases in the plasma centre. (authors). 13 refs., 6 figs.
RF heating and current drive in Tore Supra
International Nuclear Information System (INIS)
Litaudon, X.
1995-01-01
Recent RF heating and current drive experiments in the Lower Hybrid (LH) and Ion Cyclotron (IC) frequency ranges are reported. In the 4T improved confinement LHEP regime, steady-state LHCD operation has been realized with a new ''constant-flux'' scenario. A new, reversed shear, 2T improved confinement plasma regime has also been investigated when the core plasma is inaccessible to the LH waves. Stable, LH driven 0.4 MA discharges were obtained with H rlw = 2 at βp = 0.8, q o above 2 and with a reduced electron thermal diffusivity in the central reversed shear region. Efficient direct coupling of the fast magnetosonic wave to the electrons for heating and current drive is observed during 48 MHz/2T operation. Fast wave electron heating has produced improved confinement with H rlw = 2 at βp = 1.6, and a bootstrap current fraction up to 45%. Fast wave current drive has been observed at the level of 80 kA in a 0.4 MA discharge. (authors). 28 refs., 7 figs
Carbon migration and deuterium retention in Tore Supra
International Nuclear Information System (INIS)
Panayotis, Stephanie
2013-01-01
Three reasons can be invoked to characterize and control plasma-surface interaction in thermonuclear fusion devices: 1/ the plasma erosion limits the lifetime of the first wall components, 2/ the penetration of eroded particles in the plasma is the cause of fuel dilution and loss of performance and 3/ part of the fuel (D/T) is trapped in the wall or layers resulting from the redeposition of eroded particles. In carbon wall devices, points 1/ and 3/ are strongly coupled due to the chemical affinity of carbon with hydrogen or its isotopes. If the erosion/redeposition balance is often obtained from post-mortem analyses of samples extracted from the vacuum chamber, two methods are currently used to build the fuel balance, and particularly to quantify the amount of which trapped in the vessel: the post-mortem analyses cited above, and discharge per discharge gas balance. Estimations by these two methods exhibit a significant discrepancy, the amount of trapped hydrogen estimated by post-mortem being typically four times lower than that obtained from gas balance. The main reason is that the former value is resolved in space (it depends of the location of the sample in the vacuum vessel) but integrated in time (it concerns the whole period during which the sample was in the device), when the latter is a global value for the whole machine but is resolved discharge per discharge. For solving the discrepancy, one must perform post-mortem analyses on a number of samples large enough for covering the whole vessel and extend gas balance measurements to the whole period during which the considered first wall elements were used, including the period in between plasmas and vents. (author) [fr
Ergodic theory and dynamical systems
Coudène, Yves
2016-01-01
This textbook is a self-contained and easy-to-read introduction to ergodic theory and the theory of dynamical systems, with a particular emphasis on chaotic dynamics. This book contains a broad selection of topics and explores the fundamental ideas of the subject. Starting with basic notions such as ergodicity, mixing, and isomorphisms of dynamical systems, the book then focuses on several chaotic transformations with hyperbolic dynamics, before moving on to topics such as entropy, information theory, ergodic decomposition and measurable partitions. Detailed explanations are accompanied by numerous examples, including interval maps, Bernoulli shifts, toral endomorphisms, geodesic flow on negatively curved manifolds, Morse-Smale systems, rational maps on the Riemann sphere and strange attractors. Ergodic Theory and Dynamical Systems will appeal to graduate students as well as researchers looking for an introduction to the subject. While gentle on the beginning student, the book also contains a number of commen...
Convergence of multiple ergodic averages
Host, Bernard
2006-01-01
These notes are based on a course for a general audience given at the Centro de Modeliamento Matem\\'atico of the University of Chile, in December 2004. We study the mean convergence of multiple ergodic averages, that is, averages of a product of functions taken at different times. We also describe the relations between this area of ergodic theory and some classical and some recent results in additive number theory.
Ergodic averages via dominating processes
DEFF Research Database (Denmark)
Møller, Jesper; Mengersen, Kerrie
2006-01-01
We show how the mean of a monotone function (defined on a state space equipped with a partial ordering) can be estimated, using ergodic averages calculated from upper and lower dominating processes of a stationary irreducible Markov chain. In particular, we do not need to simulate the stationary...... Markov chain and we eliminate the problem of whether an appropriate burn-in is determined or not. Moreover, when a central limit theorem applies, we show how confidence intervals for the mean can be estimated by bounding the asymptotic variance of the ergodic average based on the equilibrium chain....
On the entangled ergodic theorem
Eisner, T.; Kunszenti-kovács, D.
2013-01-01
We study the convergence of the so-called entangled ergodic averages 1 Nk !N n1,...,nk=1 T n!(m) m Am−1T n!(m−1) m−1 Am−2 . . . A1T n!(1) 1 , where k " m and ! : {1, . . . ,m} #{1, . . . , k} is a surjective map.We show that, on general Banach spaces and without any restriction on the partition !,
Operator theoretic aspects of ergodic theory
Eisner, Tanja; Haase, Markus; Nagel, Rainer
2015-01-01
Stunning recent results by Host–Kra, Green–Tao, and others, highlight the timeliness of this systematic introduction to classical ergodic theory using the tools of operator theory. Assuming no prior exposure to ergodic theory, this book provides a modern foundation for introductory courses on ergodic theory, especially for students or researchers with an interest in functional analysis. While basic analytic notions and results are reviewed in several appendices, more advanced operator theoretic topics are developed in detail, even beyond their immediate connection with ergodic theory. As a consequence, the book is also suitable for advanced or special-topic courses on functional analysis with applications to ergodic theory. Topics include: •an intuitive introduction to ergodic theory •an introduction to the basic notions, constructions, and standard examples of topological dynamical systems •Koopman operators, Banach lattices, lattice and algebra homomorphisms, and the Gelfand–Naimark theorem •m...
The large deviations theorem and ergodicity
International Nuclear Information System (INIS)
Gu Rongbao
2007-01-01
In this paper, some relationships between stochastic and topological properties of dynamical systems are studied. For a continuous map f from a compact metric space X into itself, we show that if f satisfies the large deviations theorem then it is topologically ergodic. Moreover, we introduce the topologically strong ergodicity, and prove that if f is a topologically strongly ergodic map satisfying the large deviations theorem then it is sensitively dependent on initial conditions
The ergodic theory of lattice subgroups
Gorodnik, Alexander
2010-01-01
The results established in this book constitute a new departure in ergodic theory and a significant expansion of its scope. Traditional ergodic theorems focused on amenable groups, and relied on the existence of an asymptotically invariant sequence in the group, the resulting maximal inequalities based on covering arguments, and the transference principle. Here, Alexander Gorodnik and Amos Nevo develop a systematic general approach to the proof of ergodic theorems for a large class of non-amenable locally compact groups and their lattice subgroups. Simple general conditions on the spectral theory of the group and the regularity of the averaging sets are formulated, which suffice to guarantee convergence to the ergodic mean
Speckle dynamics under ergodicity breaking
Sdobnov, Anton; Bykov, Alexander; Molodij, Guillaume; Kalchenko, Vyacheslav; Jarvinen, Topias; Popov, Alexey; Kordas, Krisztian; Meglinski, Igor
2018-04-01
Laser speckle contrast imaging (LSCI) is a well-known and versatile approach for the non-invasive visualization of flows and microcirculation localized in turbid scattering media, including biological tissues. In most conventional implementations of LSCI the ergodic regime is typically assumed valid. However, most composite turbid scattering media, especially biological tissues, are non-ergodic, containing a mixture of dynamic and static centers of light scattering. In the current study, we examined the speckle contrast in different dynamic conditions with the aim of assessing limitations in the quantitative interpretation of speckle contrast images. Based on a simple phenomenological approach, we introduced a coefficient of speckle dynamics to quantitatively assess the ratio of the dynamic part of a scattering medium to the static one. The introduced coefficient allows one to distinguish real changes in motion from the mere appearance of static components in the field of view. As examples of systems with static/dynamic transitions, thawing and heating of Intralipid samples were studied by the LSCI approach.
Intuitionistic supra fuzzy topological spaces
International Nuclear Information System (INIS)
Abbas, S.E.
2004-01-01
In this paper, We introduce an intuitionistic supra fuzzy closure space and investigate the relationship between intuitionistic supra fuzzy topological spaces and intuitionistic supra fuzzy closure spaces. Moreover, we can obtain intuitionistic supra fuzzy topological space induced by an intuitionistic fuzzy bitopological space. We study the relationship between intuitionistic supra fuzzy closure space and the intuitionistic supra fuzzy topological space induced by an intuitionistic fuzzy bitopological space
Ergodicity of the generalized lemon billiards
Energy Technology Data Exchange (ETDEWEB)
Chen, Jingyu [Department of Computer Science, University of Illinois at Urbana-Champaign, Champaign, Illinois 61801-2302 (United States); Mohr, Luke; Zhang, Hong-Kun, E-mail: hongkun@math.umass.edu; Zhang, Pengfei [Department of Mathematics and Statistics, UMass Amherst, Amherst, Massachusetts 01003 (United States)
2013-12-15
In this paper, we study a two-parameter family of convex billiard tables, by taking the intersection of two round disks (with different radii) in the plane. These tables give a generalization of the one-parameter family of lemon-shaped billiards. Initially, there is only one ergodic table among all lemon tables. In our generalized family, we observe numerically the prevalence of ergodicity among the some perturbations of that table. Moreover, numerical estimates of the mixing rate of the billiard dynamics on some ergodic tables are also provided.
The ergodicity landscape of quantum theories
Ho, Wen Wei; Radičević, Đorđe
2018-02-01
This paper is a physicist’s review of the major conceptual issues concerning the problem of spectral universality in quantum systems. Here, we present a unified, graph-based view of all archetypical models of such universality (billiards, particles in random media, interacting spin or fermion systems). We find phenomenological relations between the onset of ergodicity (Gaussian-random delocalization of eigenstates) and the structure of the appropriate graphs, and we construct a heuristic picture of summing trajectories on graphs that describes why a generic interacting system should be ergodic. We also provide an operator-based discussion of quantum chaos and propose criteria to distinguish bases that can usefully diagnose ergodicity. The result of this analysis is a rough but systematic outline of how ergodicity changes across the space of all theories with a given Hilbert space dimension. As a particular example, we study the SYK model and report on the transition from maximal to partial ergodicity as the disorder strength is decreased.
Quantum ergodicity in the SYK model
Altland, Alexander; Bagrets, Dmitry
2018-05-01
We present a replica path integral approach describing the quantum chaotic dynamics of the SYK model at large time scales. The theory leads to the identification of non-ergodic collective modes which relax and eventually give way to an ergodic long time regime (describable by random matrix theory). These modes, which play a role conceptually similar to the diffusion modes of dirty metals, carry quantum numbers which we identify as the generators of the Clifford algebra: each of the 2N different products that can be formed from N Majorana operators defines one effective mode. The competition between a decay rate quickly growing in the order of the product and a density of modes exponentially growing in the same parameter explains the characteristics of the system's approach to the ergodic long time regime. We probe this dynamics through various spectral correlation functions and obtain favorable agreement with existing numerical data.
Ergodic Theory, Open Dynamics, and Coherent Structures
Bose, Christopher; Froyland, Gary
2014-01-01
This book is comprised of selected research articles developed from a workshop on Ergodic Theory, Probabilistic Methods and Applications, held in April 2012 at the Banff International Research Station. It contains contributions from world leading experts in ergodic theory, dynamical systems, numerical analysis, fluid dynamics, and networks. The volume will serve as a valuable reference for mathematicians, physicists, engineers, physical oceanographers, atmospheric scientists, biologists, and climate scientists, who currently use, or wish to learn how to use, probabilistic techniques to cope with dynamical models that display open, coherent, or non-equilibrium behavior.
SUPRA SOFT SEPARATION AXIOMS AND SUPRA IRRESOLUTENESS BASED ON SUPRA B-SOFT SETS
Abd El-latif, Alaa Mohamed; Hosny, Rodyna Ahmed
2016-01-01
This paper introduces supra soft b-separation axioms based on the supra b-open soft sets which are more general than supra open soft sets. We investigate the relationships between these supra soft separation axioms. Furthermore, with the help of examples it is established that the converse does not hold. We show that, a supra soft topological space (X; t;E) is supra soft b-T1-space, if xE is supra b-closed soft set in for each x 2 X. Also, we prove that xE is supra b-closed soft set for each ...
Ergodicity of a single particle confined in a nanopore
DEFF Research Database (Denmark)
Bernardi, S.; Hansen, Jesper Schmidt; Frascolli, F.
2012-01-01
-ergodic component of the phase space for energy levels typical of experiments, is surprisingly small, i.e. we conclude that the ergodic hypothesis is a reasonable approximation even for a single particle trapped in a nanopore. Due to the numerical scope of this work, our focus will be the onset of ergodic behavior...
Smooth Rényi Entropy of Ergodic Quantum Information Sources
Schoenmakers, Berry; Tjoelker, Jilles; Tuyls, Pim; Verbitskiy, Evgeny
2007-01-01
We investigate the recently introduced notion of smooth Rényi entropy for the case of ergodic information sources, thereby generalizing previous work which concentrated mainly on i.i.d. information sources. We will actually consider ergodic quantum information sources, of which ergodic classical
Ergodic Interference Alignment with Delayed Feedback
Kang, Myung Gil; Choi, Wan
2013-01-01
We propose new ergodic interference alignment techniques for $K$-user interference channels with delayed feedback. Two delayed feedback scenarios are considered -- delayed channel information at transmitter (CIT) and delayed output feedback. It is proved that the proposed techniques achieve total $2K/(K+2)$ DoF which is higher than that by the retrospective interference alignment for the delayed feedback scenarios.
Ergodic theory of amenable semigroup actions
Indian Academy of Sciences (India)
) (1984). [16] Riazi A and Wong J C S, Characterizations of amenable locally compact semigroups,. Pacific J. Math. 108 (1983) 479–496. [17] Rudin W, Functional analysis (New York: McGraw Hill) (1991). [18] Wong J C S, An ergodic property ...
International Nuclear Information System (INIS)
Russell, F.M.
1989-05-01
Energetic particles moving with a solid, either from nuclear reactions or externally injected, deposit energy by inelastic scattering processes which eventually appears as thermal energy. If the transfer of energy occurs in a crystalline solid then it is possible to couple some of the energy directly to the nuclei forming the lattice by generating phonons. In this paper the transfer of energy from a compound excited nucleus to the lattice is examined by introducing a virtual particle Π. It is shown that by including a Π in the nuclear reaction a substantial amount of energy can be coupled directly to the lattice. In the lattice this particle behaves as a spatially localized phonon of high energy, the so-called supra-ballistic phonon. By multiple inelastic scattering the supra-ballistic phonon eventually thermalizes. Because both the virtual particle Π and the equivalent supra-ballistic phonon have no charge or spin and can only exist within a lattice it is difficult to detect other than by its decay into thermal phonons. The possibility of a Π removing excess energy from a compound nucleus formed by the cold fusion of deuterium is examined. (Author)
On Supra-Additive and Supra-Multiplicative Maps
Jin Xi Chen; Zi Li Chen
2013-01-01
Let A and B be ordered algebras over ℝ, where A has a generating positive cone and B satisfies the property that b2>0 if 0≠b∈B. We give some conditions for a map T:A→B which is supra-additive and supra-multiplicative for all positive and negative elements to be linear and multiplicative; that is, T is a homomorphism of algebras. Our results generalize some known results on supra-additive and supra-multiplicative maps between spaces of real functions.
Probability, random processes, and ergodic properties
Gray, Robert M
1988-01-01
This book has been written for several reasons, not all of which are academic. This material was for many years the first half of a book in progress on information and ergodic theory. The intent was and is to provide a reasonably self-contained advanced treatment of measure theory, prob ability theory, and the theory of discrete time random processes with an emphasis on general alphabets and on ergodic and stationary properties of random processes that might be neither ergodic nor stationary. The intended audience was mathematically inc1ined engineering graduate students and visiting scholars who had not had formal courses in measure theoretic probability . Much of the material is familiar stuff for mathematicians, but many of the topics and results have not previously appeared in books. The original project grew too large and the first part contained much that would likely bore mathematicians and dis courage them from the second part. Hence I finally followed the suggestion to separate the material and split...
Are there ergodic limits to evolution? Ergodic exploration of genome space and convergence.
McLeish, Tom C B
2015-12-06
We examine the analogy between evolutionary dynamics and statistical mechanics to include the fundamental question of ergodicity-the representative exploration of the space of possible states (in the case of evolution this is genome space). Several properties of evolutionary dynamics are identified that allow a generalization of the ergodic dynamics, familiar in dynamical systems theory, to evolution. Two classes of evolved biological structure then arise, differentiated by the qualitative duration of their evolutionary time scales. The first class has an ergodicity time scale (the time required for representative genome exploration) longer than available evolutionary time, and has incompletely explored the genotypic and phenotypic space of its possibilities. This case generates no expectation of convergence to an optimal phenotype or possibility of its prediction. The second, more interesting, class exhibits an evolutionary form of ergodicity-essentially all of the structural space within the constraints of slower evolutionary variables have been sampled; the ergodicity time scale for the system evolution is less than the evolutionary time. In this case, some convergence towards similar optima may be expected for equivalent systems in different species where both possess ergodic evolutionary dynamics. When the fitness maximum is set by physical, rather than co-evolved, constraints, it is additionally possible to make predictions of some properties of the evolved structures and systems. We propose four structures that emerge from evolution within genotypes whose fitness is induced from their phenotypes. Together, these result in an exponential speeding up of evolution, when compared with complete exploration of genomic space. We illustrate a possible case of application and a prediction of convergence together with attaining a physical fitness optimum in the case of invertebrate compound eye resolution.
Convective Replica-Exchange in Ergodic Regimes.
Signorini, Giorgio F; Giovannelli, Edoardo; Spill, Yannick G; Nilges, Michael; Chelli, Riccardo
2014-03-11
In a recent article (J. Comput. Chem. 2013, 34, 132-140), convective replica-exchange (convective-RE) has been presented as an alternative to the standard even-odd transition scheme. Computations on systems of various complexity have shown that convective-RE may increase the number of replica round-trips in temperature space with respect to the standard exchange scheme, leading to a more effective sampling of energy basins. Moreover, it has been shown that the method may prevent the formation of bottlenecks in the diffusive walk of replicas through the space of temperature states. By using an ideal temperature-RE model and a classical harmonic-oscillator RE scheme, we study the performances of convective-RE when ergodicity is not broken and convergence of acceptance probabilities is attained. In this dynamic regime, the round-trip ratio between convective and standard-RE is at maximum ∼ 1.5, a value much smaller than that observed in nonergodic simulations. For large acceptance probabilities, the standard-RE outperforms convective-RE. Our observations suggest that convective-RE can safely be used in either ergodic or non-ergodic regimes; however, convective-RE is advantageous only when bottlenecks occur in the state-space diffusion of replicas, or when acceptance probabilities are globally low. We also show that decoupling of the state-space dynamics of the stick replica from the dynamics of the remaining replicas improves the efficiency of convective-RE at low acceptance probability regimes.
Association Contributions to the 21th EPS Conference
International Nuclear Information System (INIS)
1995-01-01
A wide range of topics concerning plasma physics at Tore Supra tokamak device is covered. Different ways of plasma heating, such as current drive, electron and ion cyclotron-resonance heating and lower hybrid heating, plasma confinement, different topics on transport theory and plasma diagnostics are discussed. The new ergodic divertor at Tore Supra is studied from different aspects. 35 items have been separately indexed for the INIS database. (K.A.)
Measurement of lower hybrid hot spots using a retarding field analyzer in Tore Supra
Czech Academy of Sciences Publication Activity Database
Gunn, J. P.; Petržílka, Václav; Ekedahl, A.; Fuchs, Vladimír; Gauthier, E.; Goniche, M.; Kočan, M.; Pascal, J.Y.; Saint Laurent, F.
390-391, č. 1 (2009), s. 904-906 ISSN 0022-3115. [International Conference on Plasma-Surface Interactions in Controlled Fusion Devices/18th./. Toledo, 26.05.2008-30.5.2008] R&D Projects: GA ČR GA202/07/0044 Institutional research plan: CEZ:AV0Z20430508 Keywords : Lower Hybrid * hot spots * ELECTRONS * POWER Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.933, year: 2009 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TXN-4VG7MW6-7&_user=6542793&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000070123&_version=1&_urlVersion=0&_userid=6542793&md5=944ed4d95df86a149fa36439db6215db
Experimental Investigation of Nonlinear Coupling of Lower Hybrid Waves on Tore Supra
Czech Academy of Sciences Publication Activity Database
Goniche, M.; Frincu, B.; Ekedahl, A.; Petržílka, Václav; Berger-By, G.; Hillairet, J.; Litaudon, X.; Preynas, M.; Voyer, D.
2012-01-01
Roč. 62, č. 2 (2012), s. 322-332 ISSN 1536-1055 R&D Projects: GA ČR GA202/07/0044 Institutional research plan: CEZ:AV0Z20430508 Keywords : LHwave * plasma * lower hybrid * wave coupling * nonlinear coupling Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.517, year: 2012
Tore Supra: a tokamak with superconducting coils for the toroidal field
International Nuclear Information System (INIS)
Turck, B.
1984-01-01
It is under construction on the site of CEN/Cadarache for the EURATOM-CEA Association. The design has been lead by a group including teams of the DRFC of Fontenay-aux-Roses and Grenoble and the DPh/PE-STI of CEN/Saclay [fr
Thermal and non-thermal particle interaction with the LHCD launchers in Tore Supra
Czech Academy of Sciences Publication Activity Database
Ekedahl, A.; Goniche, M.; Balorin, C.; Basiuk, V.; Bibet, Ph.; Chantant, M.; Colas, L.; Delpech, L.; Desgranges, C.; Eriksson, L.-G.; Joffrin, E.; Kazarian, F.; Lowry, C.; Moreau, Ph.; Petržílka, Václav; Portafaix, C.; Prou, M.; Roche, H.
363-365, č. 8 (2007), s. 1329-1333 ISSN 0022-3115 R&D Projects: GA ČR(CZ) GA202/07/0044 Institutional research plan: CEZ:AV0Z20430508 Keywords : LH grill * plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.643, year: 2007
Parallel expansion of the ablation cloud during pellet injection in Tore Supra
International Nuclear Information System (INIS)
Pegourie, B.; Bruneau, J.L.; Picchiottino, J.M.
1991-01-01
The ablated matter propagation along the field lines during pellet ablation is observed with a five chords interferometer toroidally located at -π/3 of the pellet injector. The time resolution is 16μs and the sensitivity better than 3 10 17 m -2 . The beginning of the fast acquisition is triggered by the pellet itself and its maximum duration is 20ms. About 500μs after the pellet enters the discharge, the experimental signals exhibit a steep increase. Excepted in a few cases for which a strong oscillation at a typical frequency of 0.5kHz was detected during several ms, a new quasi-steady state is reached after about lms. The importance of the measured perturbation and the details of the sequence described above depends, for each chord, on both the Q profile and pellet penetration
International Nuclear Information System (INIS)
Lediankine, A.
1996-01-01
The profiles of temperature and electronic density at the plasma edge are important to study the wall-plasma interaction and the radiative layers in the Tokamak plasmas. The laser ablation technique of the lithium allows to measure the profile of electronic density. To measure the profile of temperature, it has been used for the first time, the injection of a fluorine neutral atoms beam. The experiments, the results are described in this work. (N.C.)
Experiments on steady state particle control in Tore Supra and DIII-D
Mioduszewski, P. K.; Hogan, J. T.; Owen, L. W.; Maingi, R.; Lee, D. K.; Hillis, D. L.; Klepper, C. C.; Menon, M. M.; Thomas, C. E.; Uckan, T.; Wade, M. R.; Chatelier, M.; Grisolia, C.; Ghendrih, Ph.; Grosman, A.; Hutter, T.; Loarer, T.; Pégourié, B.; Mahdavi, M. A.; Schaffer, M.
1995-04-01
Particle control is playing an increasingly important role in tokamak plasma performance. The present paper discusses particle control of hydrogen/deuterium by wall pumping on graphite or carbonized surfaces, as well as by external exhaust with pumped limiters and pumped divertors. Wall pumping is ultimately a transient effect and by itself not suitable for steady state particle exhaust. Therefore, external exhaust techniques with pumped divertors and limiters are being developed. How wall pumping phenomena interact and correlate with these inherently steady state, external exhaust techniques, is not well known to date. In the present paper, the processes involved in wall pumping and in external pumping are investigated in an attempt to evaluate the effect of external exhaust on wall pumping. Some of the key elements of this analysis are: (1) charge-exchange fluxes to the wall play a crucial role in the core-wall particle dynamics, (2) the recycling fluxes of thermal molecules have a high probability of ionization in the scrape-off layer, (3) thermal particles originating from the wall, which are ionized within the scrape-off layer, can be directly exhausted, thus providing a direct path between wall and exhaust which can be used to control the wall inventory. This way, the wall can be kept in a continuous pumping state in the sense that it continuously absorbs energetic particles and releases thermal molecules which are then removed by the external exhaust mechanism. While most of the ingredients of this analysis have been observed individually before, the present evaluation is an attempt to correlate effects of wall recycling and external exhaust.
International Nuclear Information System (INIS)
Dubois, M.A.; Sabot, R.; Pegourie, B.; Drawin, H.W.; Geraud, A.
1992-01-01
Striations in H α (D α ) light observed across the ablation cloud of injected hydrogen pellets can be explained in most cases by the presence of resonant magnetic surfaces. We show that it is possible to identify them and to obtain a very detailed profile of the safety factor. This q- profile shows shear plateaus related to rational q-values, thus suggesting the presence of magnetic turbulence
Theory and experiments on RF plasma heating, current drive and profile control in TORE SUPRA
Energy Technology Data Exchange (ETDEWEB)
Moreau, D.
1994-01-01
This paper reviews the main experimental and theoretical achievements related to the study of RF heating and non-inductive current drive and particularly phenomena related to the current density profile control and the potentiality of producing stationary enhanced performance regimes: description of the Lower Hybrid (LH) and Ion Cyclotron Resonant Frequency (ICRF) systems; long pulse coupling performance of the RF systems; observation of the transition to the so-called ``stationary LHEP regime`` in which the (flat) central current density and (peaked) electron temperature profiles are fully decoupled; experiments on ICRF sawtooth stabilization with the combined effect of LHCD modifying the current density profile; diffusion of fast electrons generated by LH waves; ramp-up experiments in which the LH power provided a significant part of the resistive poloidal flux and flux consumption scaling; theory of spectral wave diffusion and multipass absorption; fast wave current drive modelling with the Alcyon full wave code; a reflector LH antenna concept. 18 figs., 48 refs.
Theory and experiments on RF plasma heating, current drive and profile control in TORE SUPRA
International Nuclear Information System (INIS)
Moreau, D.
1994-01-01
This paper reviews the main experimental and theoretical achievements related to the study of RF heating and non-inductive current drive and particularly phenomena related to the current density profile control and the potentiality of producing stationary enhanced performance regimes: description of the Lower Hybrid (LH) and Ion Cyclotron Resonant Frequency (ICRF) systems; long pulse coupling performance of the RF systems; observation of the transition to the so-called ''stationary LHEP regime'' in which the (flat) central current density and (peaked) electron temperature profiles are fully decoupled; experiments on ICRF sawtooth stabilization with the combined effect of LHCD modifying the current density profile; diffusion of fast electrons generated by LH waves; ramp-up experiments in which the LH power provided a significant part of the resistive poloidal flux and flux consumption scaling; theory of spectral wave diffusion and multipass absorption; fast wave current drive modelling with the Alcyon full wave code; a reflector LH antenna concept. 18 figs., 48 refs
Investigation of steady-state tokamak issues by long pulse experiments on Tore Supra
Czech Academy of Sciences Publication Activity Database
Giruzzi, G.; Abgrall, R.; Allegretti, L.; Ané, J.M.; Angelino, P.; Aniel, T.; Argouarch, A.; Artaud, J.F.; Balme, S.; Basiuk, V.; Bayetti, P.; Bécoulet, A.; Bécoulet, M.; Begrambekov, L.; Benkadda, M.S.; Benoit, F.; Berger-by, G.; Bertrand, B.; Beyer, P.; Blum, J.; Boilson, D.; Bottollier-Curtet, H.; Bouchand, C.; Bouquey, F.; Bourdelle, C.; Brémond, F.; Brémond, S.; Brosset, C.; Bucalossi, J.; Buravand, Y.; Cara, P.; Carpentier, S.; Casati, A.; Chaibi, O.; Chantant, M.; Chappuis, P.; Chatelier, M.; Chevet, G.; Ciazynski, D.; Ciraolo, G.; Clairet, F.; Clary, J.; Colas, L.; Corre, Y.; Courtois, X.; Crouseilles, N.; Darmet, G.; Davi, M.; Daviot, R.; De Esch, H.; Decker, J.; Decool, P.; Delchambre, E.; Delmas, E.; Delpech, L.; Desgranges, C.; Devynck, P.; Doceul, L.; Dolgetta, N.; Douai, D.; Dougnac, H.; Duchateau, J.L.; Dumont, R.; Dunand, A.; Durocher, A.; Ekedahl, A.; Elbeze, D.; Eriksson, L.G.; Escarguel, A.; Escourbiac, F.; Faisse, F.; Falchetto, G.; Farge, M.; Farjon, L.J.; Fedorczak, N.; Fenzi-Bonizec, C.; Garbet, X.; Garcia, J.; Gardarein, J.L.; Gargiulo, L.; Garibaldi, P.; Gauthier, E.; Géraud, A.; Gerbaud, T.; Geynet, M.; Ghendrih, P.; Gil, C.; Goniche, M.; Grandgirard, V.; Grisolia, C.; Gros, G.; Grosman, A.; Guigon, R.; Guilhem, D.; Guillerminet, B.; Guirlet, R.; Gunn, J.; Hacquin, S.; Hatchressian, J.C.; Hennequin, P.; Henry, D.; Hernandez, C.; Hertout, P.; Heuraux, S.; Hillairet, J.; Hoang, G.T.; Hong, S.H.; Honore, C.; Hourtoule, J.; Houry, M.; Hutter, T.; Huynh, P.; Huysmans, G.; Imbeaux, F.; Joffrin, E.; Johner, J.; Journeaux, J.Y.; Jullien, F.; Kazarian, F.; Kočan, M.; Lacroix, B.; Lamaison, V.; Lasalle, J.; Latu, G.; Lausenaz, Y.; Laviron, C.; Le Niliot, C.; Lennholm, M.; Leroux, F.; Linez, F.; Lipa, M.; Litaudon, X.; Loarer, T.; Lott, F.; Lotte, P.; Luciani, J.F.; Lütjens, H.; Macor, A.; Madeleine, S.; Magaud, P.; Maget, P.; Magne, R.; Manenc, L.; Marandet, Y.; Marbach, G.; Maréchal, J.L.; Martin, C.; Martin, V.; Martinez, A.; Martins, J.P.; Masset, R.; Mazon, D.; Meunier, L.; Meyer, O.; Million, L.; Missirlian, M.; Mitteau, R.; Mollard, P.; Moncada, V.; Monier-Garbet, P.; Moreau, D.; Moreau, P.; Nannini, M.; Nardon, E.; Nehme, H.; Nguyen, C.; Nicollet, S.; Ottaviani, M.; Pacella, D.; Pamela, S.; Parisot, P.; Parrat, H.; Pastor, P.; Pecquet, A.L.; Pégourié, B.; Petržílka, Václav; Peysson, Y.; Portafaix, C.; Prou, M.; Ravenel, N.; Reichle, R.; Reux, C.; Reynaud, P.; Richou, M.; Rigollet, F.; Rimini, F.; Roche, H.; Rosanvallon, S.; Roth, J.; Roubin, P.; Sabot, R.; Saint-Laurent, F.; Salasca, S.; Salmon, T.; Samaille, F.; Santagiustina, A.; Saoutic, B.; Sarazin, Y.; Schlosser, J.; Schneider, K.; Schneider, M.; Schwander, F.; Ségui, J.L.; Signoret, J.; Simonin, A.; Song, S.; Sonnendruker, E.; Spuig, P.; Svensson, L.; Tamain, P.; Tena, M.; Theis, J.M.; Thonnat, M.; Torre, A.; Travère, J.M.; Trier, E.; Tsitrone, E.; Turco, F.; Vallet, J.C.; Vatry, A.; Vermare, L.; Villecroze, F.; Villegas, D.; Voyer, D.; Vulliez, K.; Xiao, W.; Yu, D.; Zani, L.; Zou, X.L.; Zwingmann, W.
2009-01-01
Roč. 49, č. 10 (2009), s. 104010-104010 ISSN 0029-5515 Institutional research plan: CEZ:AV0Z20430508 Keywords : SOL * LH wave * plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.270, year: 2009 http://www.iop.org/EJ/ toc /0029-5515/49/10
Scrape-off layer power flux measurements in the Tore Supra tokamak
Czech Academy of Sciences Publication Activity Database
Gunn, J. P.; Dejarnac, Renaud; Devynck, P.; Fedorczak, N.; Fuchs, Vladimír; Gil, C.; Kočan, M.; Komm, Michael; Kubič, M.; Lunt, T.; Monier-Garbet, P.; Pascal, J.-Y.; Saint-Laurent, F.
2013-01-01
Roč. 438, suppl (2013), S184-S188 ISSN 0022-3115. [International Conference on Plasma-Surface Interactions in Controlled Fusion Devices/20./. Aachen, 21.05.2012-25.05.2012] Institutional support: RVO:61389021 Keywords : plasma * tokamak Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.016, year: 2013 http://www.sciencedirect.com/science/article/pii/S0022311513000639#
Avoiding ergodicity and turbulence in R3 vector fields
International Nuclear Information System (INIS)
Ancochea, J.M.; Campoamor-Stursberg, R.; Gonzalez-Gascon, F.
2003-01-01
We show that analytic R 3 vector fields having the property of being transversal to either analytic functions or foliations F 2 , or parallel to a foliation, are free from ergodicity and turbulence. The absence of turbulence and ergodicity via induced vector fields is also proven
Generalized continued fractions and ergodic theory
International Nuclear Information System (INIS)
Pustyl'nikov, L D
2003-01-01
In this paper a new theory of generalized continued fractions is constructed and applied to numbers, multidimensional vectors belonging to a real space, and infinite-dimensional vectors with integral coordinates. The theory is based on a concept generalizing the procedure for constructing the classical continued fractions and substantially using ergodic theory. One of the versions of the theory is related to differential equations. In the finite-dimensional case the constructions thus introduced are used to solve problems posed by Weyl in analysis and number theory concerning estimates of trigonometric sums and of the remainder in the distribution law for the fractional parts of the values of a polynomial, and also the problem of characterizing algebraic and transcendental numbers with the use of generalized continued fractions. Infinite-dimensional generalized continued fractions are applied to estimate sums of Legendre symbols and to obtain new results in the classical problem of the distribution of quadratic residues and non-residues modulo a prime. In the course of constructing these continued fractions, an investigation is carried out of the ergodic properties of a class of infinite-dimensional dynamical systems which are also of independent interest
On Bitopological Supra B-Open Sets
M.Lellis Thivagar; B.Meera Devi
2012-01-01
In this paper, we introduce and investigate a new class of sets and maps be- tween bitopological spaces called supra(1,2) b-open, and supra (1,2) b-continuous maps, respectively. Furthermore, we introduce the concepts of supra(1,2) locally-closed, supra(1,2) locally b-closed sets. We also introduce supra(1,2) extremely disconnected. Finally, additional properties of these sets are investigated.
Ergodic theory of expanding thurston maps
Li, Zhiqiang
2017-01-01
Thurston maps are topological generalizations of postcritically-finite rational maps. This book provides a comprehensive study of ergodic theory of expanding Thurston maps, focusing on the measure of maximal entropy, as well as a more general class of invariant measures, called equilibrium states, and certain weak expansion properties of such maps. In particular, we present equidistribution results for iterated preimages and periodic points with respect to the unique measure of maximal entropy by investigating the number and locations of fixed points. We then use the thermodynamical formalism to establish the existence, uniqueness, and various other properties of the equilibrium state for a Holder continuous potential on the sphere equipped with a visual metric. After studying some weak expansion properties of such maps, we obtain certain large deviation principles for iterated preimages and periodic points under an additional assumption on the critical orbits of the maps. This enables us to obtain general eq...
Oseledec multiplicative ergodic theorem for laminations
Nguyên, Viêt-Anh
2017-01-01
Given a n-dimensional lamination endowed with a Riemannian metric, the author introduces the notion of a multiplicative cocycle of rank d, where n and d are arbitrary positive integers. The holonomy cocycle of a foliation and its exterior powers as well as its tensor powers provide examples of multiplicative cocycles. Next, the author defines the Lyapunov exponents of such a cocycle with respect to a harmonic probability measure directed by the lamination. He also proves an Oseledec multiplicative ergodic theorem in this context. This theorem implies the existence of an Oseledec decomposition almost everywhere which is holonomy invariant. Moreover, in the case of differentiable cocycles the author establishes effective integral estimates for the Lyapunov exponents. These results find applications in the geometric and dynamical theory of laminations. They are also applicable to (not necessarily closed) laminations with singularities. Interesting holonomy properties of a generic leaf of a foliation are obtained...
Ergodic directional switching in mobile insect groups
Escudero, Carlos
2010-07-29
We obtain a Fokker-Planck equation describing experimental data on the collective motion of locusts. The noise is of internal origin and due to the discrete character and finite number of constituents of the swarm. The stationary probability distribution shows a rich phenomenology including nonmonotonic behavior of several order and disorder transition indicators in noise intensity. This complex behavior arises naturally as a result of the randomness in the system. Its counterintuitive character challenges standard interpretations of noise induced transitions and calls for an extension of this theory in order to capture the behavior of certain classes of biologically motivated models. Our results suggest that the collective switches of the group\\'s direction of motion might be due to a random ergodic effect and, as such, they are inherent to group formation. © 2010 The American Physical Society.
Uniform ergodicities and perturbation bounds of Markov chains on ordered Banach spaces
Erkursun Özcan, Nazife; Mukhamedov, Farrukh
2017-03-01
In this paper, we consider uniformly mean ergodic and uniformly asymptotical stable Markov operators on ordered Banach spaces. In terms of the ergodicity coefficient, we show the equivalence of uniform and weak mean ergodicities of Markov operators. This result allowed us to establish a category theorem for uniformly mean ergodic Markov operators. Furthermore, using properties of the ergodicity coefficient, we develop the perturbation theory for uniformly asymptotical stable Markov chains in the abstract scheme.
On reducibility and ergodicity of population projection matrix models
DEFF Research Database (Denmark)
Stott, Iain; Townley, Stuart; Carslake, David
2010-01-01
1. Population projection matrices (PPMs) are probably the most commonly used empirical population models. To be useful for predictive or prospective analyses, PPM models should generally be irreducible (the associated life cycle graph contains the necessary transition rates to facilitate pathways...... structure used in the population projection). In our sample of published PPMs, 15·6% are non-ergodic. 3. This presents a problem: reducible–ergodic models often defy biological rationale in their description of the life cycle but may or may not prove problematic for analysis as they often behave similarly...... to irreducible models. Reducible–non-ergodic models will usually defy biological rationale in their description of the both the life cycle and population dynamics, hence contravening most analytical methods. 4. We provide simple methods to evaluate reducibility and ergodicity of PPM models, present illustrative...
Non-ergodicity of Nosé-Hoover dynamics
Legoll, Frédéric; Luskin, Mitchell; Moeckel, Richard
2009-07-01
The Nosé-Hoover dynamics is a deterministic method that is commonly used to sample the canonical Gibbs measure. This dynamics extends the physical Hamiltonian dynamics by the addition of a 'thermostat' variable, which is coupled nonlinearly with the physical variables. The accuracy of the method depends on the dynamics being ergodic. Numerical experiments have been published earlier that are consistent with non-ergodicity of the dynamics for some model problems. The authors recently proved the non-ergodicity of the Nosé-Hoover dynamics for the one-dimensional harmonic oscillator. In this paper, this result is extended to non-harmonic one-dimensional systems. We also show that, for some multidimensional systems, the averaged dynamics for the limit of infinite thermostat 'mass' has many invariants, thus giving theoretical support for either non-ergodicity or slow ergodization. Numerical experiments for a two-dimensional central force problem and the one-dimensional pendulum problem give evidence for non-ergodicity. This paper is published as part of a collection in honour of Todd Dupont's 65th birthday.
Temaet folkemord i forfatterskapet til Tore Linne Eriksen. Festskrift til Tore Linne Eriksen
Balsvik, Randi Rønning
2015-01-01
Published version also available at https://journals.hioa.no/index.php/fleks/article/view/1494 This work is licensed under a Creative Commons Attribution 4.0 International License. This article points to the responsibility historians have in the formation of what we may call the collective memory of persons, groups and states. What are the images of “the other” conveyed in textbooks and media? In Norway, the historian Tore Linné Eriksen has – more than any other scholar – used ...
SUPRA - Enhanced upset recovery simulation
Groen, E.; Ledegang, W.; Field, J.; Smaili, H.; Roza, M.; Fucke, L.; Nooij, S.; Goman, M.; Mayrhofer, M.; Zaichik, L.E.; Grigoryev, M.; Biryukov, V.
2012-01-01
The SUPRA research project - Simulation of Upset Recovery in Aviation - has been funded by the European Union 7th Framework Program to enhance the flight simulation envelope for upset recovery simulation. Within the project an extended aerodynamic model, capturing the key aerodynamics during and
EURATOM-CEA association contributions to the 18. IAEA fusion energy conference
International Nuclear Information System (INIS)
Ghendrih, Ph.; Peysson, Y.; Hoang, G.T.
2000-12-01
The 9 contributions of EURATOM-Cea association to the fusion energy conference hold at Sorrento are gathered in this document with 7 additional papers. The different titles are: 1) Ergodic divertor experiments on the route to steady state operation of Tore-Supra, 2) High power lower hybrid current drive experiments in Tore-Supra tokamak, 3) Electron transport and improved confinement on Tore-Supra, 4) ECRH experiments and developments for long pulse in Tore-Supra, 5) Impurity penetration and contamination in Tore-Supra ergodic divertor experiments, 6) Real time plasma feed-back control: an overview of Tore-Supra achievements, 7) Numerical assessment of the ion turbulent thermal transport scaling laws, 8) Design of next step tokamak: consistent analysis of plasma flux consumption and poloidal, 9) Large superconducting conductors and joints for fusion magnets: from conceptual design to test at full size scale, 10) Burst-prone transport in tokamaks with internal transport barriers, 11) Electrostatic turbulence with finite parallel correlation length and radial electric field generation, 12) Theoretical issues in tokamak confinement: internal-edge transport barriers and runaway avalanche confinement, 13) Core and edge confinement studies with different heating methods in JET, 14) Confinement and transport studies of conventional scenarios in ASDEX upgrade, 15) First test results for the ITER central solenoid model coil, and 16) Progress of the ITER central solenoid model coil program
EURATOM-CEA association contributions to the 18. IAEA fusion energy conference
Energy Technology Data Exchange (ETDEWEB)
Ghendrih, Ph.; Peysson, Y.; Hoang, G.T. [and others
2000-12-01
The 9 contributions of EURATOM-Cea association to the fusion energy conference hold at Sorrento are gathered in this document with 7 additional papers. The different titles are: 1) Ergodic divertor experiments on the route to steady state operation of Tore-Supra, 2) High power lower hybrid current drive experiments in Tore-Supra tokamak, 3) Electron transport and improved confinement on Tore-Supra, 4) ECRH experiments and developments for long pulse in Tore-Supra, 5) Impurity penetration and contamination in Tore-Supra ergodic divertor experiments, 6) Real time plasma feed-back control: an overview of Tore-Supra achievements, 7) Numerical assessment of the ion turbulent thermal transport scaling laws, 8) Design of next step tokamak: consistent analysis of plasma flux consumption and poloidal, 9) Large superconducting conductors and joints for fusion magnets: from conceptual design to test at full size scale, 10) Burst-prone transport in tokamaks with internal transport barriers, 11) Electrostatic turbulence with finite parallel correlation length and radial electric field generation, 12) Theoretical issues in tokamak confinement: internal-edge transport barriers and runaway avalanche confinement, 13) Core and edge confinement studies with different heating methods in JET, 14) Confinement and transport studies of conventional scenarios in ASDEX upgrade, 15) First test results for the ITER central solenoid model coil, and 16) Progress of the ITER central solenoid model coil program.
International Conference on Ergodic Theory and Related Topics
Richter, Karin; Warstat, Volker
1992-01-01
The purpose of the conference was to represent recent developments in measure theoretic, differentiable and topological dynamical systems as well as connections to probability theory, stochastic processes, operator theory and statistical physics. Only original research papers that do not appear elsewhere are included in the proceedings. Their topics include: C(2)-diffeomorphisms of compact Riemann manifolds, geodesic flows, chaotic behaviour in billards, nonlinear ergodic theory, central limit theorems for subadditive processes, Hausdorff measures for parabolic rational maps, Markov operators, periods of cycles, Julia sets, ergodic theorems. From the Contents: L.A. Bunimovich: On absolutely focusing mirrors.- M. Denker, M. Urbanski: The dichotomy of Hausdorff measures and equilibrium states for parabolic rational maps.- F. Ledrappier: Ergodic properties of the stable foliations.- U. Wacker: Invariance principles and central limit theorems for nonadditive stationary processes.- J. Schmeling, R. Siegmund-Schult...
Ergodic optimization in the expanding case concepts, tools and applications
Garibaldi, Eduardo
2017-01-01
This book focuses on the interpretation of ergodic optimal problems as questions of variational dynamics, employing a comparable approach to that of the Aubry-Mather theory for Lagrangian systems. Ergodic optimization is primarily concerned with the study of optimizing probability measures. This work presents and discusses the fundamental concepts of the theory, including the use and relevance of Sub-actions as analogues to subsolutions of the Hamilton-Jacobi equation. Further, it provides evidence for the impressively broad applicability of the tools inspired by the weak KAM theory.
On Neutrosophic Semi-Supra Open Set and Neutrosophic Semi-Supra Continuous Functions
R. Dhavaseelan; M. Parimala; S. Jafari; F. Smarandache
2017-01-01
In this paper, we introduce and investigate a new class of sets and functions between topological space called neutrosophic semi-supra open set and neutrosophic semi-supra open continuous functions respectively.
A stochastic Ergodic Theorem in Von-Neumann algebras | Tijani ...
African Journals Online (AJOL)
In this paper we introduce the notion of stochastic convergence of τ- measurable operators and prove a noncommutative extension of pointwise ergodic theorem of G. D. Birkhoff by means of it by using the techniques developed by Petz in [12] Journal of the Nigerian Association of Mathematical Physics Vol. 9 2005: pp.
Strong ergodic theorem for commutative semigroup of non ...
Indian Academy of Sciences (India)
M Azhini
2017-08-14
Aug 14, 2017 ... group of asymptotically nonexpansive in the intermediate sense mappings in a uniformly convex multi-Banach space. Our results enable us to handle simultaneously ergodic theo- rem for asymptotically nonexpansive type mappings and semigroups in the intermediate sense, i.e., we can establish the ...
Mean ergodic operators and reflexive Fréchet lattices
Bonet, J.; De Pagter, B.; Ricker, W.J.
2011-01-01
Connections between (positive) mean ergodic operators acting in Banach lattices and properties of the underlying lattice itself are well understood (see the works of Emel'yanov, Wolff and Zaharopol). For Fréchet lattices (or more general locally convex solid Riesz spaces) there is virtually no
On Some Maps in Supra Topological Ordered Spaces
Al-shami, Tareq Mohammed
2018-01-01
In [6] the notion of supra semi open sets was presented and some of its properties were discussed. In this study, we introduce and investigate four main concepts namely supra continuous (supra open, supra closed, supra homeomorphism) maps via supra topological ordered spaces. Our findings in this work generalize some previous results in ([1], [13]). Many examples are considered to show the concepts introduced and main results obtained herein.
Plasma surface interactions in controlled fusion devices
Energy Technology Data Exchange (ETDEWEB)
Ghendrih, Ph.; Becoulet, M.; Costanzo, L. [and others
2000-07-01
This report brings together all the contributions of EURATOM/CEA association to the 14. international conference on plasma surface interactions in controlled fusion devices. 24 papers are presented and they deal mainly with the ergodic divertor and the first wall of Tore-supra tokamak.
Super convergence of ergodic averages for quasiperiodic orbits
Das, Suddhasattwa; Yorke, James A.
2018-02-01
The Birkhoff ergodic theorem asserts that time averages of a function evaluated along a trajectory of length N converge to the space average, the integral of f, as N\\to∞ , for ergodic dynamical systems. But that convergence can be slow. Instead of uniform averages that assign equal weights to points along the trajectory, we use an average with a non-uniform distribution of weights, weighting the early and late points of the trajectory much less than those near the midpoint N/2 . We show that in quasiperiodic dynamical systems, our weighted averages converge far faster provided f is sufficiently differentiable. This result can be applied to obtain efficient numerical computation of rotation numbers, invariant densities and conjugacies of quasiperiodic systems.
Generic singular continuous spectrum for ergodic Schr\\"odinger operators
Avila, Artur; Damanik, David
2004-01-01
We consider Schr\\"odinger operators with ergodic potential $V_\\omega(n)=f(T^n(\\omega))$, $n \\in \\Z$, $\\omega \\in \\Omega$, where $T:\\Omega \\to \\Omega$ is a non-periodic homeomorphism. We show that for generic $f \\in C(\\Omega)$, the spectrum has no absolutely continuous component. The proof is based on approximation by discontinuous potentials which can be treated via Kotani Theory.
Ergodicity and slow diffusion in a supercooled liquid
Bidhoodi, Neeta; Das, Shankar P.
2015-01-01
A model for the slow dynamics of the supercooled liquid is formulated in terms of the standard equations of fluctuating nonlinear hydrodynamics (FNH) with the inclusion of an extra diffusive mode for the collective density fluctuations. If the compressible nature of the liquid is completely ignored, this diffusive mode sets the longest relaxation times in the supercooled state and smooths off a possible sharp ergodicity-nonergodicity (ENE) transition predicted in a mode coupling theory. The s...
Ergodicity of the LLR method for the Density of States
Directory of Open Access Journals (Sweden)
Cossu Guido
2018-01-01
Full Text Available The LLR method is a novel algorithm that enables us to evaluate the density of states in lattice gauge theory. We present our study of the ergodicity properties of the LLR algorithm for the model of Yang Mills SU(3. We show that the use of the replica exchange method alleviates significantly the topological freeze-out that severely affects other algorithms.
Ergodic time-reversible chaos for Gibbs' canonical oscillator
International Nuclear Information System (INIS)
Hoover, William Graham; Sprott, Julien Clinton; Patra, Puneet Kumar
2015-01-01
Nosé's pioneering 1984 work inspired a variety of time-reversible deterministic thermostats. Though several groups have developed successful doubly-thermostated models, single-thermostat models have failed to generate Gibbs' canonical distribution for the one-dimensional harmonic oscillator. A 2001 doubly-thermostated model, claimed to be ergodic, has a singly-thermostated version. Though neither of these models is ergodic this work has suggested a successful route toward singly-thermostated ergodicity. We illustrate both ergodicity and its lack for these models using phase-space cross sections and Lyapunov instability as diagnostic tools. - Highlights: • We develop cross-section and Lyapunov methods for diagnosing ergodicity. • We apply these methods to several thermostatted-oscillator problems. • We demonstrate the nonergodicity of previous work. • We find a novel family of ergodic thermostatted-oscillator problems.
International Nuclear Information System (INIS)
Escourbiac, F.; Missirlian, M.; Schlosser, J.; Bobin-Vastra, I.; Kuznetsov, V.; Schedler, B.
2004-01-01
The use of flat tile technology to handle heat fluxes in the range of 20 MW/m 2 with components relevant for fusion experiment applications is technically possible with the hypervapotron cooling concept. This paper deals with recent high heat flux performances operated with success on 2 identical mock-ups, based on this concept, that were tested in 2 different electron gun facilities. Each mock-up consisted of a CuCrZr heat sink armored with 25 flat tiles of the 3D carbon fibre composite material SEPcarb NS31 assembled with pure copper by active metal casting (AMC). The AMC tiles were electron beam welded on the CuCrZr bar, fins and slots on the neutral beam JET design were machined into the bar, then the bar was closed with a thick CuCrZr rear plug including hydraulic connections then the bar was electron beam welded onto the sidewalls. The testing results show that full ITER design specifications were achieved with margins, the critical heat flux limit was even higher than 30 MW/m 2 . These results highlight the high potential of this technology for ITER divertor application
International Nuclear Information System (INIS)
Lipa, M.; Blanchet, J.; Cellier, F.
2007-01-01
Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralised water with adjustment of the pH value to about 9.0/7.0 (25 C/200 C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal combinations survived the test campaign without stress corrosion cracking, with the exception of the memory metal junction (creep in Cu) and the bellows made of St-St 316L and Inconel 625 while 316 Ti bellows survived. In contrary to the vacuum brazed Cu-LSTP to St-St samples, some of flame brazed Cu to St-St samples failed either in the braze joint or in the copper structure itself. For comparison, a spot weld of an inflated 316L panel sample, filled voluntary with a caustic solution of pH 11.5 (25 C), failed after 90 h of testing (intergranular cracking at the spot weld), while an identical sample containing AVT water of pH 9.0 (25 C) survived without damage. The results of these tests, performed during 1986 and 1997, have never been published and therefore are presented more in detail in this paper since corrosion in hydraulic circuits is also an issue of ITER. Up to day, the TS cooling water plant operates with an above mentioned water treatment and no water leaks have been detected on in-vessel components originating from water corrosion at high temperature and high pressure. (orig.)
Czech Academy of Sciences Publication Activity Database
Ekedahl, A.; Delpech, L.; Goniche, M.; Guilhem, D.; Hillairet, J.; Preynas, M.; Sharma, P.K.; Achard, J.; Bae, Y.S.; Bai, X.; Balorin, C.; Baranov, Y.; Basiuk, V.; Bécoulet, A.; Belo, J.; Berger-By, G.; Brémond, S.; Castaldo, C.; Ceccuzzi, S.; Cesario, R.; Corbel, E.; Courtois, X.; Decker, J.; Delmas, E.; Ding, X.; Douai, D.; Goletto, C.; Gunn, J. P.; Hertout, P.; Hoang, G.T.; Imbeaux, F.; Kirov, K.K.; Litaudon, X.; Magne, R.; Mailloux, J.; Mazon, D.; Mirizzi, F.; Mollard, P.; Moreau, P.; Oosako, T.; Petržílka, Václav; Peysson, Y.; Poli, S.; Prou, M.; Saint-Laurent, F.; Samaille, F.; Saoutic, B.
2010-01-01
Roč. 50, č. 11 (2010), s. 112002-112002 ISSN 0029-5515 Institutional research plan: CEZ:AV0Z20430508 Keywords : LH wave * plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010 http://iopscience.iop.org/0029-5515/50/11/112002/pdf/0029-5515_50_11_112002.pdf
International Nuclear Information System (INIS)
van Houtte, D.; Hoang, G.T.; Joffrin, E.; Lecoustey, P.; Moreau, D.; Parlange, F.; Tonon, G.; Vallet, J.C.
1992-01-01
Resistive flux saving at densities n e = (1 - 2) x 10 19 m -3 has been studied. High flux saving efficiency (0.7 x 10 13 Wb/J/m -1 ) can be achieved for a low rf power (P LH = 0.5 MW) due to the beneficial effect of the electric field on the suprathermal electrons. However for power higher than 1 MW, the efficiency is 0.25 x 10 13 Wb/J/m -1 . This flux saving efficiency is comparable to the one obtained during the flat top phase. The application of the LH power during a low density current ramp-up tends to peak the electron temperature and current density profiles. The rf power level, the parallel wavenumber and the current ramp rate allow to control the trajectories of the plasma discharges during the current rise inside the MHD stable domain
Czech Academy of Sciences Publication Activity Database
Corre, Y.; Dejarnac, Renaud; Gardarein, J.-L.; Gaspar, J.; Escourbiac, F.; Gauthier, E.; Gunn, J. P.; Komm, Michael; Lipa, M.; Loarer, T.; Missirlian, M.; Rigollet, F.
2015-01-01
Roč. 463, August (2015), s. 832-836 ISSN 0022-3115. [PLASMA-SURFACE INTERACTIONS 21: International Conference on Plasma-Surface Interactions in Controlled Fusion Devices. Kanazawa, 26.05.2014-30.05.2014] Institutional support: RVO:61389021 Keywords : Heat loads * IR thermography * misalignment * limiter Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 2.199, year: 2015 http://www.sciencedirect.com/science/article/pii/S002231151400720X
Energy Technology Data Exchange (ETDEWEB)
Lipa, M. [CEA/DSM/DRFC Centre de Cadarache, 13 - Saint-Paul lez Durance (France); Blanchet, J.; Cellier, F. [Framatome, 71 - Saint Marcel (France). Centre Technique
2007-07-01
Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralised water with adjustment of the pH value to about 9.0/7.0 (25 C/200 C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal combinations survived the test campaign without stress corrosion cracking, with the exception of the memory metal junction (creep in Cu) and the bellows made of St-St 316L and Inconel 625 while 316 Ti bellows survived. In contrary to the vacuum brazed Cu-LSTP to St-St samples, some of flame brazed Cu to St-St samples failed either in the braze joint or in the copper structure itself. For comparison, a spot weld of an inflated 316L panel sample, filled voluntary with a caustic solution of pH 11.5 (25 C), failed after 90 h of testing (intergranular cracking at the spot weld), while an identical sample containing AVT water of pH 9.0 (25 C) survived without damage. The results of these tests, performed during 1986 and 1997, have never been published and therefore are presented more in detail in this paper since corrosion in hydraulic circuits is also an issue of ITER. Up to day, the TS cooling water plant operates with an above mentioned water treatment and no water leaks have been detected on in-vessel components originating from water corrosion at high temperature and high pressure. (orig.)
Czech Academy of Sciences Publication Activity Database
Mazon, D.; Vezinet, D.; Pacella, D.; Moreau, D.; Gabelieri, L.; Romano, A.; Malard, P.; Mlynář, Jan; Masset, R.; Lotte, P.
2012-01-01
Roč. 83, č. 6 (2012), 063505-063505 ISSN 0034-6748 Institutional research plan: CEZ:AV0Z20430508 Keywords : Tokamak * tomography X-ray * diagnostics Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.602, year: 2012 http://rsi.aip.org/resource/1/rsinak/v83/i6/p063505_s1
Selvaraj, Loganathan
2016-01-01
This technical report describes a simple and innovative surgical technique for supra-alar sidewall region constriction and supra-alar crease attenuation by cinching technique through intraoral approach.
Selvaraj, Loganathan
2016-01-01
This technical report describes a simple and innovative surgical technique for supra-alar sidewall region constriction and supra-alar crease attenuation by cinching technique through intraoral approach.
Topology, ergodic theory, real algebraic geometry Rokhlin's memorial
Turaev, V
2001-01-01
This book is dedicated to the memory of the outstanding Russian mathematician, V. A. Rokhlin (1919-1984). It is a collection of research papers written by his former students and followers, who are now experts in their fields. The topics in this volume include topology (the Morse-Novikov theory, spin bordisms in dimension 6, and skein modules of links), real algebraic geometry (real algebraic curves, plane algebraic surfaces, algebraic links, and complex orientations), dynamics (ergodicity, amenability, and random bundle transformations), geometry of Riemannian manifolds, theory of Teichmüller
Asymptotic Ergodic Capacity Analysis of Composite Lognormal Shadowed Channels
Ansari, Imran Shafique
2015-05-01
Capacity analysis of composite lognormal (LN) shadowed links, such as Rician-LN, Gamma-LN, and Weibull-LN, is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single composite link transmission system is presented in terms of well- known elementary functions. Capitalizing on these new moments expressions, we present asymptotically tight lower bounds for the ergodic capacity at high SNR. All the presented results are verified via computer-based Monte-Carlo simulations. © 2015 IEEE.
Efficient estimation for ergodic diffusions sampled at high frequency
DEFF Research Database (Denmark)
Sørensen, Michael
A general theory of efficient estimation for ergodic diffusions sampled at high fre- quency is presented. High frequency sampling is now possible in many applications, in particular in finance. The theory is formulated in term of approximate martingale estimating functions and covers a large class...... of parameters in the drift coefficient, and for efficiency. The conditions turn out to be equal to those implying small Δ-optimality in the sense of Jacobsen and thus gives an interpretation of this concept in terms of classical sta- tistical concepts. Optimal martingale estimating functions in the sense...
A role for a Brachistochrone in the broken ergodicity scenario
Appignanesi, Gustavo A.
2000-02-01
We show that the time evolution of ergodic decomposition is outlined by a variational principle for a rather universal class of complex systems with a quasicontinuous spectrum of intrinsic relaxation timescales. In turn, this variational approach enables us to single out a logarithmic scaling law for the barriers on the hierarchical level. Such a logarithmic dependence has already been shown to hold valid for certain complex systems. Moreover, it represents a key factor to explain the experimentally ubiquitous Debye-Kohlrausch relaxation law and plays a central role on different theoretical model descriptions within this field.
Equilibrium states and the ergodic theory of Anosov diffeomorphisms
2008-01-01
For this printing of R. Bowen's book, J.-R. Chazottes has retyped it in TeX for easier reading, thereby correcting typos and bibliographic details. From the Preface by D. Ruelle: "Rufus Bowen has left us a masterpiece of mathematical exposition... Here a number of results which were new at the time are presented in such a clear and lucid style that Bowen's monograph immediately became a classic. More than thirty years later, many new results have been proved in this area, but the volume is as useful as ever because it remains the best introduction to the basics of the ergodic theory of hyperbolic systems."
Ergodicity breaking in frustrated disordered systems: replicas in mean-field spin-glass models
Czech Academy of Sciences Publication Activity Database
Janiš, Václav; Kauch, Anna; Klíč, Antonín
2015-01-01
Roč. 88, č. 3 (2015), s. 245-263 ISSN 0141-1594 Institutional support: RVO:68378271 Keywords : ergodicity and thermodynamic homogeneity * real replicas * ergodicity and replica-symmetry breaking * asymptotic solution Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.858, year: 2015
Ergodic theory, interpretations of probability and the foundations of statistical mechanics
van Lith, J.H.
2001-01-01
The traditional use of ergodic theory in the foundations of equilibrium statistical mechanics is that it provides a link between thermodynamic observables and microcanonical probabilities. First of all, the ergodic theorem demonstrates the equality of microcanonical phase averages and infinite time
Fluctuation, stationarity, and ergodic properties of random-matrix ensembles
International Nuclear Information System (INIS)
Pandey, A.
1979-01-01
The properties of random-matrix ensembles and the application of such ensembles to energy-level fluctuations and strength fluctuations are discussed. The two-point correlation function for complex spectra described by the three standard Gaussian ensembles is calculated, and its essential simplicity, displayed by an elementary procedure that derives from the dominance of binary correlations. The resultant function is exact for the unitary case and a very good approximation to the orthogonal and symplectic cases. The same procedure yields the spectrum for a Gaussian orthogonal ensemble (GOE) deformed by a pairing interaction. Several extensions are given and relationships to other problems of current interest are discussed. The standard fluctuation measures are rederived for the GOE, and their extensions to the unitary and symplectic cases are given. The measures are shown to derive, for the most part, from the two-point function, and new relationships between them are established, answering some long-standing questions. Some comparisons with experimental values are also made. All the cluster functions, and therefore the fluctuation measures, are shown to be stationary and strongly ergodic, thus justifying the use of random matrices for individual spectra. Strength fluctuations in the orthogonal ensemble are also considered. The Porter-Thomas distribution in its various forms is rederived and its ergodicity is established
Ergodicity, hidden bias and the growth rate gain
Rochman, Nash D.; Popescu, Dan M.; Sun, Sean X.
2018-05-01
Many single-cell observables are highly heterogeneous. A part of this heterogeneity stems from age-related phenomena: the fact that there is a nonuniform distribution of cells with different ages. This has led to a renewed interest in analytic methodologies including use of the ‘von Foerster equation’ for predicting population growth and cell age distributions. Here we discuss how some of the most popular implementations of this machinery assume a strong condition on the ergodicity of the cell cycle duration ensemble. We show that one common definition for the term ergodicity, ‘a single individual observed over many generations recapitulates the behavior of the entire ensemble’ is implied by the other, ‘the probability of observing any state is conserved across time and over all individuals’ in an ensemble with a fixed number of individuals but that this is not true when the ensemble is growing. We further explore the impact of generational correlations between cell cycle durations on the population growth rate. Finally, we explore the ‘growth rate gain’—the phenomenon that variations in the cell cycle duration leads to an improved population-level growth rate—in this context. We highlight that, fundamentally, this effect is due to asymmetric division.
Controlled thermonuclear reactions and Tora Supra program
International Nuclear Information System (INIS)
1988-01-01
The research programs for the nuclear energy production by means of thermonuclear fusion are shown. TORA SUPRA, Joint European Torus, Next European Torus and those developed at the Atomic Energy Center are described. The controlled fusion necessary conditions, the energy and confinement balance, and the research of a better tokamak configuration are discussed. A description of TORA SUPRA, the ways of achieving the project and the expected delays are shown. The Controlled Fusion Research Department functions, concerning these programs, are described. The importance of international cooperation and the perspectives about the use of controlled fusion are underlined [fr
The Non-Ergodic Nature of Internal Conversion
DEFF Research Database (Denmark)
Kuhlman, Thomas Scheby
The absorption of light by molecules can induce ultrafast dynamics of coupled electronic and nuclear vibrational motion. The ultrafast nature in many cases rests on the importance of several potential energy surfaces in guiding the nuclear dynamics – a concept of central importance in many aspects...... of chemical reaction dynamics. In this thesis, we focus on the non-ergodic nature of internal conversion, i.e. the concept that the nuclear dynamics only sample a reduced phase space potentially resulting in localization of the dynamics in real space. In essence, this is a consequence of vibrational energy...... redistribution simply not being able to compete with the rate of internal conversion. The work employ the experimental methods of time-resolved mass spectrometry and photoelectron spectroscopy supplemented by electronic structure calculations and quantum dynamics simulations on seven cycloketones, three...
Asymptotic behaviour of time averages for non-ergodic Gaussian processes
Ślęzak, Jakub
2017-08-01
In this work, we study the behaviour of time-averages for stationary (non-ageing), but ergodicity-breaking Gaussian processes using their representation in Fourier space. We provide explicit formulae for various time-averaged quantities, such as mean square displacement, density, and analyse the behaviour of time-averaged characteristic function, which gives insight into rich memory structure of the studied processes. Moreover, we show applications of the ergodic criteria in Fourier space, determining the ergodicity of the generalised Langevin equation's solutions.
Directory of Open Access Journals (Sweden)
Miguel Carvalhais
2015-11-01
Full Text Available Procedural systems allow unique modes of authorship and singular aesthetic experiences. As creators and users of these systems, we need to be aware that their aesthetic potential is not solely defined by interaction but that interpretation, and the capacity to understand and simulate the processes taking place within these artefacts is highly significant. This paper argues that although direct interaction is usually the most discernible component in the relationship between ergodic artefacts and their users, ergodicity does not necessarily imply interaction. Non-interactive procedural artefacts may allow the development of ergodic experiences through interpretation, and the probing of the system by its reader through simulations. We try to set the grounds for designing towards virtuosic interpretation, an activity that we may describe as the ergodic experience developed by means of mental simulation through the development of theories of systems.
Rates of convergence and asymptotic normality of curve estimators for ergodic diffusion processes
J.H. van Zanten (Harry)
2000-01-01
textabstractFor ergodic diffusion processes, we study kernel-type estimators for the invariant density, its derivatives and the drift function. We determine rates of convergence and find the joint asymptotic distribution of the estimators at different points.
Upper and lower bounds for the ergodic capacity of MIMO Jacobi fading channels.
Nafkha, Amor; Bonnefoi, Rémi
2017-05-29
In multi-(core/mode) optical fiber communication, the transmission channel can be modeled as a complex sub-matrix of the Haar-distributed unitary matrix (complex Jacobi unitary ensemble). In this letter, we present new analytical expressions of the upper and lower bounds for the ergodic capacity of multiple-input multiple-output Jacobi-fading channels. Recent results on the determinant of the Jacobi unitary ensemble are employed to derive a tight lower bound on the ergodic capacity. We use Jensen's inequality to provide an analytical closed-form upper bound to the ergodic capacity at any signal-to-noise ratio (SNR). Closed-form expressions of the ergodic capacity, at low and high SNR regimes, are also derived. Simulation results are presented to validate the accuracy of the derived expressions.
Let the Game Begin: Ergodic as an Approach for Video Game Translation
SF. Lukfianka Sanjaya Purnama; SF. Luthfie Arguby Purnomo; Dyah Nugrahani
2016-01-01
This paper attempts to propose ergodic as an approach for video game translation. The word approach here refers to an approach for translation products and to an approach for the translation process. The steps to formulate ergodic as an approach are first, Aarseth’sergodic literature is reviewed to elicit a basis for comprehension toward its relationship with video games and video game translation Secondly, taking the translation of Electronic Arts’Need for Speed: Own the City, Midway’s Morta...
Ergodicity and Parameter Estimates for Infinite-Dimensional Fractional Ornstein-Uhlenbeck Process
International Nuclear Information System (INIS)
Maslowski, Bohdan; Pospisil, Jan
2008-01-01
Existence and ergodicity of a strictly stationary solution for linear stochastic evolution equations driven by cylindrical fractional Brownian motion are proved. Ergodic behavior of non-stationary infinite-dimensional fractional Ornstein-Uhlenbeck processes is also studied. Based on these results, strong consistency of suitably defined families of parameter estimators is shown. The general results are applied to linear parabolic and hyperbolic equations perturbed by a fractional noise
Characterisation of Supra- and Infratentorial ICP Profiles.
Moyse, Emmanuel; Ros, Maxime; Marhar, Fouad; Swider, Pascal; Schmidt, Eric Albert
2016-01-01
In pathophysiology and clinical practice, the intracranial pressure (ICP) profiles in the supratentorial and infratentorial compartments are unclear. We know that the pressure within the skull is unevenly distributed, with demonstrated ICP gradients. We recorded and characterised the supra- and infratentorial ICP patterns to understand what drives the transtentorial ICP gradient.A 70-year-old man was operated on for acute cerebellar infarction. One supratentorial probe and one cerebellar probe were implanted. Both signals were recorded concurrently and analysed off-line. We calculated mean ICP, ICP pulse amplitude, respiratory waves, slow waves and the RAP index of supra- and infratentorial ICP signals. Then, we measured transtentorial difference and performed correlation analysis for every index.Supratentorial ICP mean was 8.5 mmHg lower than infratentorial ICP, but the difference lessens for higher values. Both signals across the tentorium showed close correlation. Supra- and infratentorial pulse amplitude, respiratory waves and slow waves also showed a high degree of correlation. The compensatory reserve (RAP) showed good correlation. In this case report, we demonstrate that the mean value of ICP is higher in the posterior fossa, with a strong correlation across the tentorium. All other ICP-derived parameters display a symmetrical profile.
Fractional Feynman-Kac equation for weak ergodicity breaking.
Carmi, Shai; Barkai, Eli
2011-12-01
The continuous-time random walk (CTRW) is a model of anomalous subdiffusion in which particles are immobilized for random times between successive jumps. A power-law distribution of the waiting times, ψ(τ) ~ τ(-(1+α)), leads to subdiffusion (x(2) ~ t(α)) for 0 CTRW in a binding potential. We use our equations to study two specific time averages: the fraction of time spent by a particle in half-box, and the time average of the particle's position in a harmonic field. In both cases, we obtain the probability density function of the time averages for t → ∞ and the first two moments. Our results show that both the occupation fraction and the time-averaged position are random variables even for long times, except for α = 1, when they are identical to their ensemble averages. Using our fractional Feynman-Kac equation, we also study the dynamics leading to weak ergodicity breaking, namely the convergence of the fluctuations to their asymptotic values.
Temaet folkemord i forfatterskapet til Tore Linné Eriksen
Directory of Open Access Journals (Sweden)
Randi Rønning Balsvik
2015-10-01
Full Text Available This article points to the responsibility historians have in the formation of what we may call the collective memory of persons, groups and states. What are the images of “the other” conveyed in textbooks and media? In Norway, the historian Tore Linné Eriksen has – more than any other scholar – used his research, writings and enormous capacity for work to educate students, youth and the public in general and to create a more just image of “the other”. His driving force has been an extraordinary ability to be at the forefront in spotting international research, as well as his sense of justice and respect for the non-western world. His last extensive work on global history (Globalhistorie 1750–1900 clearly demonstrates these capabilities.In the early 1980s, long before the wave of genocide studies after the Rwanda catastrophe of 1994, Eriksen’s two works on Namibia –Namibia: Kolonialisme, apartheid og frigjøringskamp i det sørlige Afrika (1982 and The Political Economy of Namibia: An Annotated Critical Bibliography (1985 – used the concept of genocide to describe German conduct in Namibia in the early 20th century. In 2007, Eriksen published his book about what he calls the first genocide of the 20th century, Det første folkemordet i det tjuende århundret. Namibia 1903–1908. German and African history is woven into the question of whether the dangerous relations that developed between German settlers and Africans can be labelled genocide. The present article attempts to present Eriksen’s arguments. An introductory section deals with the trends in the international research literature and establishes a link between colonialism and genocide. In 2008, Eriksen’s article on the extinction of the Herero people in Namibia – “Utslettelse av Hererofolket i Namibia 1903– 1908” – was published in Bernt Hagtvets collection of articles, Folkemordenes svarte bok. The following year, Tore Linné Eriksen’s article in the
Tore : [luuletused] / Betti Alver ; [Impressioonid] : Viiu Härm
Alver, Betti, 1906-1989
2004-01-01
Sisu: Tore ; Algav päev ; Allikal ; Maru 1 ; Lähen müüjaks ; Noorus ; Tulipunane vihmavari ; Pedja ; Äkki ilm läks sulale ; Läbi lillede ; Suvi ; Sõnarine ; Ja see oli kõik ; Asjad ; Muusale ; Hambad ; "Vaim, kandes kord triumfipärgi..." ; Hääled ; Vilepuhuja ; Tüli ; Helde andja ; Pühapäevalaps ; Froufrou ; Vooruse võlu ; Sügis 1 ; Talv ; Kuuljale ; Meistrile ; Ei vaibu ; Ilus õde ; Kahepaikne ; Kannibal ; Tuhm kalender ; Raudne taevas ; Koguja ; Inimhetk ; Su nägu ; Läkitus ; Kaks saarlast ; Hing ; Kuus kildu ; Räägi tasa minuga ; Lõppude lõpuks ; Kaduv käsi ; Vana teater ; Raudsed närvid ; Linna taga ; Külm puhang lõõtsub ; Rätsep mure ; Mina ise ; Puust palitu ; Kerjus ; Öölaul ; Pilvele ; Põdural põllul ; Üle tuhande tõkke ; Päikeses ; "Ma nägin und: mind jättis jumal maha..." ; Uni ; Kiivas kuu ; Viimne soov ; Raudahjus põlesid puud ; Linnud naersid ; Arbujate aegu 1 ; Arbujate aegu 2 ; Korallid Emajões ; Udus ; Võlg ; Raugad ; Pähklikoor ; Ekstaas ; "Maailma saatust alati..." ; Tige valgus ; "Selle ilma igav kainus..." ; Sidemed ; "Jäägu teistele alandlik jaatus..." ; Mu juurde voogas ; Suurest haardest ; Laulik ; Suur Nimetu ; Ei tea ; "Mulle meenuvad kauged hommikud..." ; Peegel ; Ime 1936 ; Võrdlus ; Ime 1988 ; Suured voogajad ; Elul on väikene hingemaa ; Ebausklik ; Priiskaja ; Tähetund ; Elu on alles uus ; Kuristikulill ; Süda ; Sa hapramast hapram ; Eluhelbed ; Lootus ; Kes oli su kaitsja ; Lehekuu lumi ; Sügis 2
Ergodic theory and negative curvature CIRM Jean-Morlet Chair, Fall 2013
2017-01-01
Focussing on the mathematics related to the recent proof of ergodicity of the (Weil–Petersson) geodesic flow on a nonpositively curved space whose points are negatively curved metrics on surfaces, this book provides a broad introduction to an important current area of research. It offers original textbook-level material suitable for introductory or advanced courses as well as deep insights into the state of the art of the field, making it useful as a reference and for self-study. The first chapters introduce hyperbolic dynamics, ergodic theory and geodesic and horocycle flows, and include an English translation of Hadamard's original proof of the Stable-Manifold Theorem. An outline of the strategy, motivation and context behind the ergodicity proof is followed by a careful exposition of it (using the Hopf argument) and of the pertinent context of Teichmüller theory. Finally, some complementary lectures describe the deep connections between geodesic flows in negative curvature and Diophantine approximatio...
On the Ergodic Capacity of Dual-Branch Correlated Log-Normal Fading Channels with Applications
Al-Quwaiee, Hessa
2015-05-01
Closed-form expressions of the ergodic capacity of independent or correlated diversity branches over Log-Normal fading channels are not available in the literature. Thus, it is become of an interest to investigate the behavior of such metric at high signal-to-noise (SNR). In this work, we propose simple closed-form asymptotic expressions of the ergodic capacity of dual-branch correlated Log- Normal corresponding to selection combining, and switch-and-stay combining. Furthermore, we capitalize on these new results to find new asymptotic ergodic capacity of correlated dual- branch free-space optical communication system under the impact of pointing error with both heterodyne and intensity modulation/direct detection. © 2015 IEEE.
A class of regular invariants as asymptotical limits or ergodic means
International Nuclear Information System (INIS)
Courbage, M.
1977-01-01
The asymptotic or ergodic behavior of a class of initial states for quantum statistical systems where the collision operator, introduced by Prigogine and coworkers, is non-vanishing is studied. In this case, they distinguish two particular classes of invariants, called respectively regular and collisionnal invariants, among the invariants of the motion. A class of initial states which tend to those invariants asymptotically or in the ergodic mean is caracterized using the destruction operator and some spectral properties of the representation in the case of systems whose hamiltonians have an absolutely continuous part in their spectrum. Furthermore, collisional invariants which can be obtained as ergodic means of some equivalence class of one initial state are characterized in terms of the GAMMA + Friedrichs operator. Uniqueness of that initial state is lost when the asymptotic collision operator is non-vanishing [fr
EURATOM-CEA association contributions to the 21st symposium on fusion technology
Energy Technology Data Exchange (ETDEWEB)
Garin, P.; Grosman, A.; Beaumont, B. [and others
2000-11-01
The 27 contributions of EURATOM-Cea association have been gathered with 6 additional papers and 1 invited paper in this document. Most papers concern Tore-Supra and deal with the ergodic divertor, particle injection, impedance concept for ICRF antennas, low hybrid current drive, RF systems, the 118 GHz ECRH experiment, the inner first wall, improved vacuum vessel protection, pellet injection, material activation, and the CIEL project. 3 of the additional papers concern the model coil of ITER.
EURATOM-CEA association contributions to the 21st symposium on fusion technology
International Nuclear Information System (INIS)
Garin, P.; Grosman, A.; Beaumont, B.
2000-11-01
The 27 contributions of EURATOM-Cea association have been gathered with 6 additional papers and 1 invited paper in this document. Most papers concern Tore-Supra and deal with the ergodic divertor, particle injection, impedance concept for ICRF antennas, low hybrid current drive, RF systems, the 118 GHz ECRH experiment, the inner first wall, improved vacuum vessel protection, pellet injection, material activation, and the CIEL project. 3 of the additional papers concern the model coil of ITER
Can future systemic financial risks be quantified?: ergodic vs nonergodic stochastic processes
Directory of Open Access Journals (Sweden)
Paul Davidson
2009-12-01
Full Text Available Different axioms underlie efficient market theory and Keynes's liquidity preference theory. Efficient market theory assumes the ergodic axiom. Consequently, today's decision makers can calculate with actuarial precision the future value of all possible outcomes resulting from today's decisions. Since in an efficient market world decision makers "know" their intertemporal budget constraints, decision makers never default on a loan, i.e., systemic defaults, insolvencies, and bankruptcies are impossible. Keynes liquidity preference theory rejects the ergodic axiom. The future is ontologically uncertain. Accordingly systemic defaults and insolvencies can occur but can never be predicted in advance.
Directory of Open Access Journals (Sweden)
Bernard Wong
2009-01-01
martingale component is based on an ergodic diffusion with a specified stationary distribution. These models are particularly useful for long horizon asset-liability management as they allow the modelling of long term stock returns with heavy tail ergodic diffusions, with tractable, time homogeneous dynamics, and which moreover admit a complete financial market, leading to unique pricing and hedging strategies. Unfortunately the standard specifications of these models in literature admit arbitrage opportunities. We investigate in detail the features of the existing model specifications which create these arbitrage opportunities and consequently construct a modification that is arbitrage free.
Self-averaging and ergodicity of subdiffusion in quenched random media
Dentz, Marco; Russian, Anna; Gouze, Philippe
2016-01-01
We study the self-averaging properties and ergodicity of the mean square displacement m (t ) of particles diffusing in d dimensional quenched random environments which give rise to subdiffusive average motion. These properties are investigated in terms of the sample to sample fluctuations as measured by the variance of m (t ) . We find that m (t ) is not self-averaging for d 2 obeys a CTRW, which by itself displays weak ergodicity breaking. This paradox is resolved by the observation that the CTRW as an average model does not reflect the disorder sampling by random motion in a single medium realization.
International Nuclear Information System (INIS)
1999-10-01
This report references the EURATOM-CEA association contributions presented at the 26. EPS conference on controlled fusion and plasma physics, in Maastricht (Netherlands) the 14-18 June 1999. Two invited papers and 24 contributed papers are proposed. They deal with: tokamak devices; particle recirculation in ergodic divertor; current profile control and MHD stability in Tore Supra discharges; edge-plasma control by the ergodic divertor; electron heat transport in stochastic magnetic layer; bolometry and radiated power; particle collection by ergodic divertor; study and simulation of plasma impurities; line shape modelling for plasma edge conditions; dynamical study of the radial structure of the fluctuations measured by reciprocating Langmuir probe in Tore Supra; up-down asymmetry of density fluctuations; Halo currents in a circular tokamak; real time measurement of the position, density, profile and current profile at Tore Supra; poloidal rotation measurement by reflectometry; interpretation of q-profile dependence of the LH power deposition profile during LHCD experiments; ICFR plasma production and optimization; improved core electron confinement; measurement of hard X-ray emission profile; modelling of shear effects on thermal and particles transport; ion turbulence; current drive generation based on autoresonance and intermittent trapping mechanisms. (A.L.B.)
Energy Technology Data Exchange (ETDEWEB)
NONE
1999-10-15
This report references the EURATOM-CEA association contributions presented at the 26. EPS conference on controlled fusion and plasma physics, in Maastricht (Netherlands) the 14-18 June 1999. Two invited papers and 24 contributed papers are proposed. They deal with: tokamak devices; particle recirculation in ergodic divertor; current profile control and MHD stability in Tore Supra discharges; edge-plasma control by the ergodic divertor; electron heat transport in stochastic magnetic layer; bolometry and radiated power; particle collection by ergodic divertor; study and simulation of pa impurities; line shape modelling for plasma edge conditions; dynamical study of the radial structure of the fluctuations measured by reciprocating Langmuir probe in Tore Supra; up-down asymmetry of density fluctuations; Halo currents in a circular tokamak; real time measurement of the position, density, profile and current profile at Tore Supra; poloidal rotation measurement by reflectometry; interpretation of q-profile dependence of the LH power deposition profile during LHCD experiments; ICFR plasma production and optimization; improved core electron confinement; measurement of hard X-ray emission profile; modelling of shear effects on thermal and particles transport; ion turbulence; current drive generation based on autoresonance and intermittent trapping mechanisms. (A.L.B.)
Supra-personal cognitive control and metacognition
Shea, Nicholas; Boldt, Annika; Bang, Dan; Yeung, Nick; Heyes, Cecilia; Frith, Chris D.
2014-01-01
The human mind is extraordinary in its ability not merely to respond to events as they unfold but also to adapt its own operation in pursuit of its agenda. This ‘cognitive control’ can be achieved through simple interactions among sensorimotor processes, and through interactions in which one sensorimotor process represents a property of another in an implicit, unconscious way. So why does the human mind also represent properties of cognitive processes in an explicit way, enabling us to think and say ‘I’m sure’ or ‘I’m doubtful’? We suggest that ‘system 2 metacognition’ is for supra-personal cognitive control. It allows metacognitive information to be broadcast, and thereby to coordinate the sensorimotor systems of two or more agents involved in a shared task. PMID:24582436
In vivo Anomalous Diffusion and Weak Ergodicity Breaking of Lipid Granules
DEFF Research Database (Denmark)
Jeon, J.-H.; Tejedor, V.; Burov, S.
2011-01-01
according to the laws of continuous time random walk theory. The associated violation of ergodicity leads to a characteristic turnover between two scaling regimes of the time averaged mean squared displacement. At longer times the granule motion is consistent with fractional Brownian motion....
Ergodicity and parameter estimates for infinite-dimensional fractional Ornstein-Uhlenbeck process
Czech Academy of Sciences Publication Activity Database
Maslowski, Bohdan; Pospíšil, J.
2008-01-01
Roč. 57, č. 3 (2008), s. 401-429 ISSN 0095-4616 R&D Projects: GA ČR GA201/07/0237 Institutional research plan: CEZ:AV0Z10190503 Keywords : ergodicity * fractional OU process * parameter estimates Subject RIV: BA - General Mathematics Impact factor: 0.667, year: 2008
Non-ergodic delocalized phase in Anderson model on Bethe lattice and regular graph
Kravtsov, V. E.; Altshuler, B. L.; Ioffe, L. B.
2018-02-01
We develop a novel analytical approach to the problem of single particle localization in infinite dimensional spaces such as Bethe lattice and random regular graph models. The key ingredient of the approach is the notion of the inverted order thermodynamic limit (IOTL) in which the coupling to the environment goes to zero before the system size goes to infinity. Using IOTL and Replica Symmetry Breaking (RSB) formalism we derive analytical expressions for the fractal dimension D1 that distinguishes between the extended ergodic, D1 = 1, and extended non-ergodic (multifractal), 0 graphs with the branching number K. We also employ RSB formalism to derive the analytical expression ln Styp-1 = - 〈 ln S 〉 ∼(Wc - W) - 1 for the typical imaginary part of self-energy Styp in the non-ergodic phase close to the Anderson transition in the conventional thermodynamic limit. We prove the existence of an extended non-ergodic phase in a broad range of disorder strength and energy and establish the phase diagrams of the models as a function of disorder and energy. The results of the analytical theory are compared with large-scale population dynamics and with the exact diagonalization of Anderson model on random regular graphs. We discuss the consequences of these results for the many body localization.
Extinction and Ergodic Property of Stochastic SIS Epidemic Model with Nonlinear Incidence Rate
Directory of Open Access Journals (Sweden)
Qixing Han
2013-01-01
Full Text Available We investigate a stochastic SIS model with nonlinear incidence rate. We show that there exists a unique nonnegative solution to the system, and condition for the infectious individuals I(t to be extinct is given. Moreover, we prove that the system has ergodic property. Finally, computer simulations are carried out to verify our results.
Ruin probability with claims modeled by a stationary ergodic stable process
Mikosch, T; Samorodnitsky, G
2000-01-01
For a random walk with negative drift we study the exceedance probability (ruin probability) of a high threshold. The steps of this walk (claim sizes) constitute a stationary ergodic stable process. We study how ruin occurs in this situation and evaluate the asymptotic behavior of the ruin
Let the Game Begin: Ergodic as an Approach for Video Game Translation
Directory of Open Access Journals (Sweden)
Sf. Lukfianka Sanjaya Purnama, Sf. Luthfie Arguby Purnomo, Dyah Nugrahani
2017-01-01
Full Text Available This paper attempts to propose ergodic as an approach for video game translation. The word approach here refers to an approach for translation products and to an approach for the translation process. The steps to formulate ergodic as an approach are first, Aarseth’sergodic literature is reviewed to elicit a basis for comprehension toward its relationship with video games and video game translation Secondly, taking the translation of Electronic Arts’Need for Speed: Own the City, Midway’s Mortal Kombat: Unchained, and Konami’s Metal Gear Solid, ergodic based approach for video game translation is formulated. The formulation signifies that ergodic, as an approach for video game translation, revolves around the treatment of video games as a cybertext from which scriptons, textons, and traversal functions as the configurative mechanism influence the selection of translation strategies and the transferability of variables and traversal function, game aesthetics, and ludus and narrative of the games. The challenges countered when treating video games as a cybertext are the necessities for the translators to convey anamorphosis, mechanical and narrative hidden meaning of the analyzed frame, to consider the textonomy of the games, and at the same time to concern on GILT (Globalization, Internationalization, Localization, and Translation.
A Simple Proof of the Theorem Concerning Optimality in a One-Dimensional Ergodic Control Problem
International Nuclear Information System (INIS)
Fujita, Y.
2000-01-01
We give a simple proof of the theorem concerning optimality in a one-dimensional ergodic control problem. We characterize the optimal control in the class of all Markov controls. Our proof is probabilistic and does not need to solve the corresponding Bellman equation. This simplifies the proof
Strong laws for generalized absolute Lorenz curves when data are stationary and ergodic sequences
R. Helmers (Roelof); R. Zitikis
2004-01-01
textabstractWe consider generalized absolute Lorenz curves that include, as special cases, classical and generalized L - statistics as well as absolute or, in other words, generalized Lorenz curves. The curves are based on strictly stationary and ergodic sequences of random variables. Most of the
arXiv Ergodicity of the LLR method for the Density of States
Cossu, Guido; Pellegrini, Roberto; Rago, Antonio
2018-01-01
The LLR method is a novel algorithm that enables us to evaluate the density of states in lattice gauge theory. We present our study of the ergodicity properties of the LLR algorithm for the model of Yang Mills SU(3). We show that the use of the replica exchange method alleviates significantly the topological freeze-out that severely affects other algorithms.
DEFF Research Database (Denmark)
Truelsen, Jimi Lee
W. Luo and P. Sarnak have proved quantum unique ergodicity for Eisenstein series on $PSL(2,Z) \\backslash H$. We extend their result to Eisenstein series on $PSL(2,O) \\backslash H^n$, where $O$ is the ring of integers in a totally real field of degree $n$ over $Q$ with narrow class number one, using...
Electron heat diffusivity in radially-bounded ergodic region of toroidal plasma
Kanno, Ryutaro; Nunami, Masanori; Satake, Shinsuke; Matsuoka, Seikichi; Takamaru, Hisanori
2018-01-01
Drift-kinetic δ f simulations are performed to investigate effect of ergodic field lines caused by resonant magnetic perturbations (RMPs) on radial heat diffusivity of electrons in the edge region of toroidal plasma of collisionality ν_\\ast ∼ 0.1 . The following is assumed in the simulations. The ergodic region is bounded radially on both sides by closed magnetic surfaces. The pressure gradient remains nonzero in the ergodic region because of an incomplete flattening of the pressure profile, and the characteristic scale length of the pressure gradient is of larger order than the overlapping width of the neighbouring magnetic islands. It is found in the quasi-steady state of δ f that the electron heat diffusivity is of smaller order than the theoretical estimate derived by the Rechester–Rosenbluth model (Rechester and Rosenbluth 1978 Phys. Rev. Lett. 40 38). The radial heat conduction is dominated not only by parallel motions along the ergodic field lines, but also by trapped particle motions generated by the RMP field. The contribution of the trapped particles reduces the radial heat conduction enhanced by the parallel motions.
A noncommutative mean ergodic theorem for partial W*-dynamical semigroups
International Nuclear Information System (INIS)
Ekhaguere, G.O.S.
1992-12-01
A noncommutative mean ergodic theorem for dynamical semigroups of maps on partial W*-algebras of linear operators from a pre-Hilbert space into its completion is proved. This generalizes a similar result of Watanabe for dynamical semigroups of maps on W*-algebras of operators. (author). 14 refs
Ghannam, Khaled; Poggi, Davide; Porporato, Amilcare; Katul, Gabriel G.
2015-12-01
Connections between the spatial and temporal statistics of turbulent flow, and their possible convergence to ensemble statistics as assumed by the ergodic hypothesis, are explored for passive scalars within a rod canopy. While complete ergodicity is not expected to apply over all the spatial domain within such heterogeneous flows, the fact that canopy turbulence exhibits self-similar characteristics at a given depth within the canopy encourages a discussion on necessary conditions for an `operational' ergodicity framework. Flows between roughness elements such as within canopies exhibit features that distinguish them from their well-studied classical boundary-layer counterparts. These differences are commonly attributed to short-circuiting of the energy cascade and the prevalence of intermittent von Kármán vortex streets in the deeper layers of the canopy. Using laser-induced fluorescence measurements at two different depths within a rod canopy situated in a large flume, the spatio-temporal statistical properties and concomitant necessary conditions for ergodicity of passive scalar turbulence statistics are evaluated. First, the integral time and length scales are analyzed and their corresponding maximum values are used to guide the construction of an ensemble of independent realizations from repeated spatio-temporal concentration measurements. As a statistical analysis for an operational ergodicity check, a Kolmogorov-Smirnov test on the distributions of temporal and spatial concentration series against the ensemble was conducted. The outcome of this test reveals that ergodicity is reasonably valid over the entire domain except close to the rod elements where wake-induced inhomogeneities and damped turbulence prevail. The spatial concentration statistics within a grid-cell (square domain formed by four corner rods) appear to be less ergodic than their temporal counterparts, which is not surprising given the periodicity and persistence of von Kármán vortices in
Pigeard de Almeida Prado, Fernando; Schütz, Gunter M.
2011-03-01
We consider a kinetic Ising model which represents a generic agent-based model for various types of socio-economic systems. We study the case of a finite (and not necessarily large) number of agents N as well as the asymptotic case when the number of agents tends to infinity. The main ingredient are individual decision thresholds which are either fixed over time (corresponding to quenched disorder in the Ising model, leading to nonlinear deterministic dynamics which are generically non-ergodic) or which may change randomly over time (corresponding to annealed disorder, leading to ergodic dynamics). We address the question how increasing the strength of annealed disorder relative to quenched disorder drives the system from non-ergodic behavior to ergodicity. Mathematically rigorous analysis provides an explicit and detailed picture for arbitrary realizations of the quenched initial thresholds, revealing an intriguing "jumpy" transition from non-ergodicity with many absorbing sets to ergodicity. For large N we find a critical strength of annealed randomness, above which the system becomes asymptotically ergodic. Our theoretical results suggests how to drive a system from an undesired socio-economic equilibrium (e.g. high level of corruption) to a desirable one (low level of corruption).
An Amylase-Responsive Bolaform Supra-Amphiphile.
Kang, Yuetong; Cai, Zhengguo; Tang, Xiaoyan; Liu, Kai; Wang, Guangtong; Zhang, Xi
2016-02-01
An amylase-responsive bolaform supra-amphiphile was constructed by the complexation between β-cyclodextrin and a bolaform covalent amphiphile on the basis of host-guest interaction. The bolaform covalent amphiphile could self-assemble in solution, forming sheet-like aggregates and displaying weak fluorescence because of aggregation-induced quenching. The addition of β-cyclodextrin led to the formation of the bolaform supra-amphiphile, prohibiting the aggregation of the bolaform covalent amphiphile and accompanying with the significant recovery of fluorescence. Upon the addition of α-amylase, with the degradation β-cyclodextrin, the fluorescence of the supra-amphiphile would quench gradually and significantly, and the quenching rate linearly correlated to the concentration of α-amylase. This study enriches the field of supra-amphiphiles on the basis of noncovalent interactions, and moreover, it may provide a facile way to estimate the activity of α-amylase.
Directory of Open Access Journals (Sweden)
Igor de Castro
2005-03-01
Full Text Available In spite of significant advancements in imaging technology, monitoring, and microsurgical techniques, complete and safe removal of tentorial meningiomas remains a challenge for most neurosurgeons. Classifications of tentorial meningiomas are revised. The combined supra/infratentorial approach to resects tentorial meningioma is discussed. This approach provides a wider exposure of the supra/infratentorial region with less brain retraction. With this approach the occipital lobe and the cerebellum are exposed along the tentorium. Two illustrative cases are presented. The patients were studied with computerized tomography, magnetic resonance and angiography. The anatomy of the transverse sinus and the confluence of the sinus could be appreciated with these studies. The operative technique is described stepwise. Emphasis is placed on pre-operative evaluation and surgical technique, leading to a total surgical removal of the lesion with margins of safety. The goal of surgical treatment of tentorial meningiomas is their complete and safe removal. With this unique approach we sought to confirm that it offers a safe means of resection not only the neoplasm but also the infiltrated dura.Apesar dos significativos avanços na tecnologia de imagens, nas técnicas de monitorização e microcirúrgicas, a ressecção completa e segura dos meningiomas tentoriais permanece um desafio para maioria dos neurocirurgiões. A abordagem supra e infra-tentorial proporciona ampla exposição das regiões supra e infratentoriais diminuindo a retração cerebral. Com esse tipo de abordagem o lobo occiptal e o cerebelo são expostos ao longo da superficie tentorial. Dois casos ilustrativos são apresentados. Os pacientes foram avaliados com tomografia computadorizada, ressonância magnética e angiografia, o que permitiu estudar a anatomia do seio transverso, a confluência e dominancia dos seios. O objetivo do tratamento cirúrgico dos meningiomas tentoriais é a remo
supraHex: An R/Bioconductor package for tabular omics data analysis using a supra-hexagonal map☆
Fang, Hai; Gough, Julian
2014-01-01
Biologists are increasingly confronted with the challenge of quickly understanding genome-wide biological data, which usually involve a large number of genomic coordinates (e.g. genes) but a much smaller number of samples. To meet the need for data of this shape, we present an open-source package called ‘supraHex’ for training, analysing and visualising omics data. This package devises a supra-hexagonal map to self-organise the input data, offers scalable functionalities for post-analysing the map, and more importantly, allows for overlaying additional data for multilayer omics data comparisons. Via applying to DNA replication timing data of mouse embryogenesis, we demonstrate that supraHex is capable of simultaneously carrying out gene clustering and sample correlation, providing intuitive visualisation at each step of the analysis. By overlaying CpG and expression data onto the trained replication-timing map, we also show that supraHex is able to intuitively capture an inherent relationship between late replication, low CpG density promoters and low expression levels. As part of the Bioconductor project, supraHex makes accessible to a wide community in a simple way, what would otherwise be a complex framework for the ultrafast understanding of any tabular omics data, both scientifically and artistically. This package can run on Windows, Mac and Linux, and is freely available together with many tutorials on featuring real examples at http://supfam.org/supraHex. PMID:24309102
Wang, Guangtong; Wu, Guanglu; Wang, Zhiqiang; Zhang, Xi
2014-02-18
A series of bolaform supra-amphilphiles with different symmetries were fabricated through dynamic benzoic imine bond formation. The pH dependence of imine formations of these supra-amphiphiles were characterazied. We found that the extent of the imine formation of these supra-amphiphies were different. The supra-amphiphiles with a poorer symmetry always exhibited a lower imine formation at a given pH. Therefore, the varied extent of imine bond formation indicate the different aggregations of these supra-amphilphiles, which are controlled by the molecular symmetry of the supra-amphiphiles.
Divertor plasma modification by divertor biasing and edge ergodization in JFT-2M
International Nuclear Information System (INIS)
Shoji, T.; Nagashima, K.; Tamai, H.; Ohdachi, S.; Miura, Y.; Ohasa, K.; Maeda, H.; Ohyabu, N.; Leonard, A.W.; Aikawa, H.; Fujita, T.; Hoshino, K.; Kawashima, H.; Matsuda, T.; Maeno, M.; Mori, M.; Ogawa, H.; Shimada, M.; Uehara, K.; Yamauchi, T.
1995-01-01
The effects of divertor biasing and edge ergodization on the divertor plasma have been investigated in the JFT-2M tokamak. Experimental results show; (1) The differential divertor biasing can change the in/out asymmetry of the divertor plasma. It especially changes the density on the ion side divertor plasma. The in/out electron pressure difference has a good correlation with the biasing current. (2) The unipolar divertor biasing can change the density profile of divertor plasma. The radial electric field and shear flow are the cause for this change. (3) The electron temperature of the divertor plasma in the H-mode with frequent ELMs induced by edge ergodization is lower than that of usual H-mode. That is due to the enhancement of the radial particle flux by frequent ELMs, ((orig.))
Ergodic averages for monotone functions using upper and lower dominating processes
DEFF Research Database (Denmark)
Møller, Jesper; Mengersen, Kerrie
We show how the mean of a monotone function (defined on a state space equipped with a partial ordering) can be estimated, using ergodic averages calculated from upper and lower dominating processes of a stationary irreducible Markov chain. In particular, we do not need to simulate the stationary...... Markov chain and we eliminate the problem of whether an appropriate burn-in is determined or not. Moreover, when a central limit theorem applies, we show how confidence intervals for the mean can be estimated by bounding the asymptotic variance of the ergodic average based on the equilibrium chain. Our...... methods are studied in detail for three models using Markov chain Monte Carlo methods and we also discuss various types of other models for which our methods apply....
Ergodic averages for monotone functions using upper and lower dominating processes
DEFF Research Database (Denmark)
Møller, Jesper; Mengersen, Kerrie
2007-01-01
We show how the mean of a monotone function (defined on a state space equipped with a partial ordering) can be estimated, using ergodic averages calculated from upper and lower dominating processes of a stationary irreducible Markov chain. In particular, we do not need to simulate the stationary...... Markov chain and we eliminate the problem of whether an appropriate burn-in is determined or not. Moreover, when a central limit theorem applies, we show how confidence intervals for the mean can be estimated by bounding the asymptotic variance of the ergodic average based on the equilibrium chain. Our...... methods are studied in detail for three models using Markov chain Monte Carlo methods and we also discuss various types of other models for which our methods apply....
Thermodynamics and ergodicity of finite one-dimensional Toda and Morse lattices
International Nuclear Information System (INIS)
Likhachev, V.N.; Astakhova, T.Yu.; Vinogradov, G.A.
2006-01-01
The thermodynamics of finite one-dimensional lattices of particles interacting via Toda or Morse potentials is considered. An analysis is performed in canonical and microcanonical ensembles in 'temperature-lattice deformation' variables. Analytical results are obtained for thermodynamical values. It is demonstrated that small number of particles, e.g. N=10, is enough to get accurate approximation in the thermodynamical limit N->∼. The problem of the deformation rate is also investigated. It is found that the temperature increases at high deformation rate, and decreases at slow deformations. The Morse lattice was analyzed in numerical MD simulations in both canonical and microcanonical ensembles. The results are in qualitative agreement with the results for the Toda lattice. The finite Morse lattice is ergodic and the Toda lattice is non-ergodic. An excellent agreement between analytical and numerical results is obtained
Novel relations between the ergodic capacity and the average bit error rate
Yilmaz, Ferkan
2011-11-01
Ergodic capacity and average bit error rate have been widely used to compare the performance of different wireless communication systems. As such recent scientific research and studies revealed strong impact of designing and implementing wireless technologies based on these two performance indicators. However and to the best of our knowledge, the direct links between these two performance indicators have not been explicitly proposed in the literature so far. In this paper, we propose novel relations between the ergodic capacity and the average bit error rate of an overall communication system using binary modulation schemes for signaling with a limited bandwidth and operating over generalized fading channels. More specifically, we show that these two performance measures can be represented in terms of each other, without the need to know the exact end-to-end statistical characterization of the communication channel. We validate the correctness and accuracy of our newly proposed relations and illustrated their usefulness by considering some classical examples. © 2011 IEEE.
Yilmaz, Ferkan
2012-06-01
Ergodic capacity is an important performance measure associated with reliable communication at the highest rate at which information can be sent over the channel with a negligible probability of error. In the shadow of this definition, diversity receivers (such as selection combining, equal-gain combining and maximal-ratio combining) and transmission techniques (such as cascaded fading channels, amplify-and-forward multihop transmission) are deployed in mitigating various performance impairing effects such as fading and shadowing in digital radio communication links. However, the exact analysis of ergodic capacity is in general not always possible for all of these forms of diversity receivers and transmission techniques over generalized composite fading environments due to it\\'s mathematical intractability. In the literature, published papers concerning the exact analysis of ergodic capacity have been therefore scarce (i.e., only [1] and [2]) when compared to those concerning the exact analysis of average symbol error probability. In addition, they are essentially targeting to the ergodic capacity of the maximal ratio combining diversity receivers and are not readily applicable to the capacity analysis of the other diversity combiners / transmission techniques. In this paper, we propose a novel moment generating function-based approach for the exact ergodic capacity analysis of both diversity receivers and transmission techniques over generalized composite fading environments. As such, we demonstrate how to simultaneously treat the ergodic capacity analysis of all forms of both diversity receivers and multihop transmission techniques. © 2012 IEEE.
A new fuzzy Monte Carlo method for solving SLAE with ergodic fuzzy Markov chains
Directory of Open Access Journals (Sweden)
Maryam Gharehdaghi
2015-05-01
Full Text Available In this paper we introduce a new fuzzy Monte Carlo method for solving system of linear algebraic equations (SLAE over the possibility theory and max-min algebra. To solve the SLAE, we first define a fuzzy estimator and prove that this is an unbiased estimator of the solution. To prove unbiasedness, we apply the ergodic fuzzy Markov chains. This new approach works even for cases with coefficients matrix with a norm greater than one.
Ergodicity for a Stochastic Geodesic Equation in the Tangent Bundle of the 2D Sphere
Czech Academy of Sciences Publication Activity Database
Baňas, L.; Brzezniak, Z.; Neklyudov, M.; Ondreját, Martin; Prohl, A.
2015-01-01
Roč. 65, č. 3 (2015), s. 617-657 ISSN 0011-4642 R&D Projects: GA ČR GAP201/10/0752 Institutional support: RVO:67985556 Keywords : geometric stochastic wave equation * stochastic geodesic equation * ergodicity * attractivity * invariant measure * numerical approximation Subject RIV: BA - General Mathematics Impact factor: 0.284, year: 2015 http://library.utia.cas.cz/separaty/2015/SI/ondrejat-0451399.pdf
Impact of nonzero boresight pointing error on ergodic capacity of MIMO FSO communication systems.
Boluda-Ruiz, Rubén; García-Zambrana, Antonio; Castillo-Vázquez, Beatriz; Castillo-Vázquez, Carmen
2016-02-22
A thorough investigation of the impact of nonzero boresight pointing errors on the ergodic capacity of multiple-input/multiple-output (MIMO) free-space optical (FSO) systems with equal gain combining (EGC) reception under different turbulence models, which are modeled as statistically independent, but not necessarily identically distributed (i.n.i.d.) is addressed in this paper. Novel closed-form asymptotic expressions at high signal-to-noise ratio (SNR) for the ergodic capacity of MIMO FSO systems are derived when different geometric arrangements of the receive apertures at the receiver are considered in order to reduce the effect of nonzero inherent boresight displacement, which is inevitably present when more than one receive aperture is considered. As a result, the asymptotic ergodic capacity of MIMO FSO systems is evaluated over log-normal (LN), gamma-gamma (GG) and exponentiated Weibull (EW) atmospheric turbulence in order to study different turbulence conditions, different sizes of receive apertures as well as different aperture averaging conditions. It is concluded that the use of single-input/multiple-output (SIMO) and MIMO techniques can significantly increase the ergodic capacity respect to the direct path link when the inherent boresight displacement takes small values, i.e. when the spacing among receive apertures is not too big. The effect of nonzero additional boresight errors, which is due to the thermal expansion of the building, is evaluated in multiple-input/single-output (MISO) and single-input/single-output (SISO) FSO systems. Simulation results are further included to confirm the analytical results.
Supra Arcade Downflows in the Earth's Magnetotail
Kobelski, A.; Savage, S. L.; Malaspina, D.
2017-12-01
Pinpointing the location of a single reconnection event in the corona is difficult due to observational constraints, although features directly resulting from this rapid reconfiguration of the field lines can be observed beyond the reconnection site. One set of such features are outflows in the form of post-reconnection loops, which have been linked to observations of supra-arcade downflows (SADs). SADs appear as sunward-traveling, density-depleted regions above flare arcades that develop during long duration eruptions. The limitations of remote sensing methods inherently results in ambiguities regarding the interpretation of SAD formation. Of particular interest is how these features are related to post-reconnection retracting magnetic field lines. In planetary magnetospheres, similar events to solar flares occur in the form of substorms, where reconnection in the anti-sunward tail of the magnetosphere causes field lines to retract toward the planet. Using data from the Time History of Events and Macroscopic Interactions during Substorms (THEMIS), we compare one particular aspect of substorms, dipolarization fronts, to SADs. Dipolarization fronts are observed as rapid but temporary changes in the magnetic field of the magnetotail plasma sheet into a more potential-like dipolar shape. These dipolarization fronts are believed to be retracting post-reconnection field lines. We combine data sets to show that the while the densities and magnetic fields involved vary greatly between the regimes, the plasma βs and Alfvén speeds are similar. These similarities allow direct comparison between the retracting field lines and their accompanying wakes of rarified plasma observed with THEMIS around the Earth to the observed morphological density depletions visible with XRT and AIA on the Sun. These results are an important source of feedback for models of coronal current sheets.
Two-way DF relaying assisted D2D communication: ergodic rate and power allocation
Ni, Yiyang; Wang, Yuxi; Jin, Shi; Wong, Kai-Kit; Zhu, Hongbo
2017-12-01
In this paper, we investigate the ergodic rate for a device-to-device (D2D) communication system aided by a two-way decode-and-forward (DF) relay node. We first derive closed-form expressions for the ergodic rate of the D2D link under asymmetric and symmetric cases, respectively. We subsequently discuss two special scenarios including weak interference case and high signal-to-noise ratio case. Then we derive the tight approximations for each of the considered scenarios. Assuming that each transmitter only has access to its own statistical channel state information (CSI), we further derive closed-form power allocation strategy to improve the system performance according to the analytical results of the ergodic rate. Furthermore, some insights are provided for the power allocation strategy based on the analytical results. The strategies are easy to compute and require to know only the channel statistics. Numerical results show the accuracy of the analysis results under various conditions and test the availability of the power allocation strategy.
Directory of Open Access Journals (Sweden)
Bahrami Hamid Reza
2007-01-01
Full Text Available The ergodic capacity of MIMO frequency-flat and -selective channels depends greatly on the eigenvalue distribution of spatial correlation matrices. Knowing the eigenstructure of correlation matrices at the transmitter is very important to enhance the capacity of the system. This fact becomes of great importance in MIMO wireless systems where because of the fast changing nature of the underlying channel, full channel knowledge is difficult to obtain at the transmitter. In this paper, we first investigate the effect of eigenvalues distribution of spatial correlation matrices on the capacity of frequency-flat and -selective channels. Next, we introduce a practical scheme known as linear precoding that can enhance the ergodic capacity of the channel by changing the eigenstructure of the channel by applying a linear transformation. We derive the structures of precoders using eigenvalue decomposition and linear algebra techniques in both cases and show their similarities from an algebraic point of view. Simulations show the ability of this technique to change the eigenstructure of the channel, and hence enhance the ergodic capacity considerably.
Deterministic time-reversible thermostats: chaos, ergodicity, and the zeroth law of thermodynamics
Patra, Puneet Kumar; Sprott, Julien Clinton; Hoover, William Graham; Griswold Hoover, Carol
2015-09-01
The relative stability and ergodicity of deterministic time-reversible thermostats, both singly and in coupled pairs, are assessed through their Lyapunov spectra. Five types of thermostat are coupled to one another through a single Hooke's-law harmonic spring. The resulting dynamics shows that three specific thermostat types, Hoover-Holian, Ju-Bulgac, and Martyna-Klein-Tuckerman, have very similar Lyapunov spectra in their equilibrium four-dimensional phase spaces and when coupled in equilibrium or nonequilibrium pairs. All three of these oscillator-based thermostats are shown to be ergodic, with smooth analytic Gaussian distributions in their extended phase spaces (coordinate, momentum, and two control variables). Evidently these three ergodic and time-reversible thermostat types are particularly useful as statistical-mechanical thermometers and thermostats. Each of them generates Gibbs' universal canonical distribution internally as well as for systems to which they are coupled. Thus they obey the zeroth law of thermodynamics, as a good heat bath should. They also provide dissipative heat flow with relatively small nonlinearity when two or more such temperature baths interact and provide useful deterministic replacements for the stochastic Langevin equation.
Occupation times and ergodicity breaking in biased continuous time random walks
Energy Technology Data Exchange (ETDEWEB)
Bel, Golan; Barkai, Eli [Physics Department, Bar-Ilan University, Ramat-Gan 52900 (Israel)
2005-12-14
Continuous time random walk (CTRW) models are widely used to model diffusion in condensed matter. There are two classes of such models, distinguished by the convergence or divergence of the mean waiting time. Systems with finite average sojourn time are ergodic and thus Boltzmann-Gibbs statistics can be applied. We investigate the statistical properties of CTRW models with infinite average sojourn time; in particular, the occupation time probability density function is obtained. It is shown that in the non-ergodic phase the distribution of the occupation time of the particle on a given lattice point exhibits bimodal U or trimodal W shape, related to the arcsine law. The key points are as follows. (a) In a CTRW with finite or infinite mean waiting time, the distribution of the number of visits on a lattice point is determined by the probability that a member of an ensemble of particles in equilibrium occupies the lattice point. (b) The asymmetry parameter of the probability distribution function of occupation times is related to the Boltzmann probability and to the partition function. (c) The ensemble average is given by Boltzmann-Gibbs statistics for either finite or infinite mean sojourn time, when detailed balance conditions hold. (d) A non-ergodic generalization of the Boltzmann-Gibbs statistical mechanics for systems with infinite mean sojourn time is found.
Supra-National Organisations and Conflict Resolution during the ...
African Journals Online (AJOL)
More importantly, due to the various crises that plagued the world ranging from civil wars to border clashes etc., the importance or roles of Supra-national organisations in conflict resolution through mediatory diplomacy or otherwise cannot be over-emphasised. This is especially geared towards making the World a Haven of ...
Supra-auricular versus Sinusectomy Approaches for Preauricular Sinuses.
El-Anwar, Mohammad Waheed; ElAassar, Ahmed Shaker
2016-10-01
Introduction Several surgical techniques and modifications have been described to reduce the high recurrence rate after excision of preauricular sinus. Objectives The aim of this study is to review the literature regarding surgical approaches for preauricular sinus. Data Synthesis We performed searches in the LILACS, MEDLINE, SciELO, PubMed databases and Cochrane Library in September, 2015, and the key words used in the search were "preauricular sinus," "sinusectomy," "supra-auricular approach," "methylene blue," and/or "recurrence." We revised the results of 17 studies, including 1270 preauricular sinuses that were surgically excised by sinusectomy in 937 ears and by supra-auricular approach in 333 ears. Recurrence with supra-auricular was 4 (1.3%) while sinusectomy was 76 (8.1%) with significant difference ( p Supra-auricular approach had significantly less recurrence rate than tract sinusectomy approaches. Thus, it could be regularly chosen as the standard procedure for preauricular sinus excision. As such, it would be helpful for surgeons to be familiar with this approach.
Supra-transumbilical laparotomy (STL) approach for small bowel ...
African Journals Online (AJOL)
Background: Supra-Transumbilical Laparotomy (STL) has been used in paediatric surgery for a broad spectrum of abdominal procedures. We report our experience with STL approach for small bowel atresia repair in newborns and review previous published series on the topic. Patients and Methods: Fourteen patients with ...
Acometimento da supra-renal associado à paracoccidioidomicose
Directory of Open Access Journals (Sweden)
Leonardo Maurício Diniz
1988-12-01
Full Text Available A supra-renal foi estudada em 60pacientes com paracoccidioidomicose. Dentre eles, 10(16,7% apresentavam alterações anatômicas ou funcionais das supra-renais. As lesões glandulares associaram-se à paracoccidioidomicose disseminada, com evolução da doença de pelo menos cinco anos sem tratamento e com hipotensão arterial sistêmica. Não houve associação entre alterações anatomoclínicas supra-renais e alterações raáiolôgicaspulmonares. Esses dados revelam a importância da avaliação sistemática da função supra-renal em portadores de formas disseminadas da paracoccidioidomicose.Sixty patients with paracoccidioidomycosis (PCM were studied, with special regard to adrenal involvement. Ten patients (16.7% had adrenal ab-normalities associated with hypotension, a disseminated form of the disease and more than five years of evolution without treatment. No statistical association between adrenal anatomo-clinical alterations and radiological pulmonary abnormalities was observed. These data point out to the importance of systematic evaluation of adrenal function in patients with disseminated PCM.
Myositis Ossificans Circumscripta of the Supra-orbital Region: A ...
African Journals Online (AJOL)
ANNALS
Abstract. Myositis ossificans circumscripta is a pathological condition characterized by formation of bony tissue within the skeletal muscles following repeated trauma. A case of myositis ossificans circumscripta of the supra-orbital region in a 25-year-old man is presented and the pertinent literature is reviewed. To the best.
Supra-Ethnic Nationalism: The Case of Eritrea | Bereketeab | African ...
African Journals Online (AJOL)
African Sociological Review / Revue Africaine de Sociologie. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 6, No 2 (2002) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Supra-Ethnic Nationalism: The ...
Simulation of sub-molecular and supra-molecular fluids
Frenkel, D.
1991-01-01
Computer simulations indicate that many forms of liquid crystalline order in lyotropic systems may be due to simple excluded volume effects. Yet, there is more to liquid crystalline ordering than simple hard-core repulsion. In order to understand liquid crystalline order in supra-molecular systems
Supra-annular mitral valve replacement in children.
Kanter, Kirk R; Kogon, Brian E; Kirshbom, Paul M
2011-12-01
Despite improved mitral repair techniques, some children need mitral valve replacement (MVR). Due to small annulus size, supra-annular MVR is useful. From 2003 to 2010, 15 children had 23 supra-annular MVRs. At first supra-annular MVR, median age was 6.5 months (28 days to 47 months); median weight was 5.4 kg (3.3-11.8 kg). Twelve (80%) had prior operations, 8 (53%) had previous mitral repair. Eight had congenital mitral anomalies (4 with Shone's), 5 had atrioventricular septal defects, 1 had endocarditis, and 1 had a repaired anomalous left coronary artery. All primary MVRs used mechanical valves (≤ 17 mm in 9 patients). There was one early death (93% survival) in an 11-month-old with congenital pulmonary vein stenosis. One intraoperative conversion from annular to supra-annular MVR developed heart block. Three pacemakers were implanted for supraventricular rhythm disturbances. Three children had valve thrombosis early postoperatively treated medically. On follow-up of 4.3 ± 2.8 years, 8 had reoperation including redo MVR in 6 for pannus formation or thrombus (1 had three redo MVRs). At redo, a larger valve was used in 5 and a bioprosthetic valve in 4 patients. There was one late death after third redo MVR with pulmonary vein stenosis relief (overall survival 87%). Supra-annular MVR is useful for children with a small annulus. Operative survival is good with infrequent heart block. Complications are common, including redo MVR and need for left ventricular outflow tract obstruction relief. Pulmonary vein stenosis is a marker for poor outcome; all patients without pulmonary vein stenosis survive long term. Copyright © 2011 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.
On the asymptotic ergodic capacity of FSO links with generalized pointing error model
Al-Quwaiee, Hessa
2015-09-11
Free-space optical (FSO) communication systems are negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. To quantize the effect of these two factors on FSO system performance, we need an effective mathematical model for them. Scintillations are typically modeled by the log-normal and Gamma-Gamma distributions for weak and strong turbulence conditions, respectively. In this paper, we propose and study a generalized pointing error model based on the Beckmann distribution. We then derive the asymptotic ergodic capacity of FSO systems under the joint impact of turbulence and generalized pointing error impairments. © 2015 IEEE.
Dynamical analysis of the magnetic field line evolution in tokamaks with ergodic limiters
Energy Technology Data Exchange (ETDEWEB)
Ullmann, Kai; Caldas, Ibere L. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica
1997-12-31
Full text. Magnetic ergodic limiters are commonly used to control chaos in the tokamak border and several models have been developed to study the influence of these limiters on the magnetic field line evolution in the tokamak vessel. In this work we derive a bidimensional symplectic mapping describing this evolution with toroidal corrections. Poincare plots presenting typical Hamiltonian behaviour, such as island chains and hetero clinic and homo clinic orbits are obtained. Then we perform the dynamical analysis of these Poincare plots using standard algorithms such as calculation of Lyapunov exponents, safety factors, FFT spectra and parameters space plots to perform the dynamical analysis. (author)
DEFF Research Database (Denmark)
Truelsen, Jimi Lee
2011-01-01
W. Luo and P. Sarnak have proved the quantum unique ergodicity property for Eisenstein series on PSL(2, )\\. Their result is quantitative in the sense that they find the precise asymptotics of the measure considered. We extend their result to Eisenstein series on , where is the ring of integers...... in a totally real field of degree n over with narrow class number one, using the Eisenstein series considered by I. Efrat. We also give an expository treatment of the theory of Hecke operators on non-holomorphic Hilbert modular forms....
Stationary distribution and ergodicity of a stochastic food-chain model with Lévy jumps
Yu, Jingyi; Liu, Meng
2017-09-01
In this paper, a three-species stochastic food-chain model with Lévy jumps is proposed and analyzed. Sharp sufficient criteria for the existence and uniqueness of an ergodic stationary distribution are established. The effects of Lévy jumps on the existence of the stationary distribution are revealed: in some cases, the Lévy jumps could make the stationary distribution appear, while in some cases, the Lévy jumps could make the stationary distribution disappear. Some numerical simulations are introduced to illustrate the theoretical results.
Extended abstract: ergodic magnetic limiter experiments on TEXT with a 7/3 resonance
International Nuclear Information System (INIS)
deGrassie, J.S.; Ohyabu, N.; Brooks, N.H.
1984-05-01
The ergodic magnetic limiter coils on TEXT have been reconfigured to produce the primary helical perturbation resonance at m = 7 / n = 3. The experiments continue to demonstrate that the weak resonant perturbations modify the edge conditions in keeping with model predictions. We observe a reduction in the intrinsic impurity levels accompanying the helical current pulse, presumably the result of a reduction in the electron temperature in the edge. Heat follows the perturbed field lines to the limiter, generating heat load patterns which reflect the geometry of a magnetic island - limiter intersection. A strong spatial modulation of the electron density in the scrape-off-layer also reflects the helical mode structure
Fluctuations around equilibrium laws in ergodic continuous-time random walks.
Schulz, Johannes H P; Barkai, Eli
2015-06-01
We study occupation time statistics in ergodic continuous-time random walks. Under thermal detailed balance conditions, the average occupation time is given by the Boltzmann-Gibbs canonical law. But close to the nonergodic phase, the finite-time fluctuations around this mean are large and nontrivial. They exhibit dual time scaling and distribution laws: the infinite density of large fluctuations complements the Lévy-stable density of bulk fluctuations. Neither of the two should be interpreted as a stand-alone limiting law, as each has its own deficiency: the infinite density has an infinite norm (despite particle conservation), while the stable distribution has an infinite variance (although occupation times are bounded). These unphysical divergences are remedied by consistent use and interpretation of both formulas. Interestingly, while the system's canonical equilibrium laws naturally determine the mean occupation time of the ergodic motion, they also control the infinite and Lévy-stable densities of fluctuations. The duality of stable and infinite densities is in fact ubiquitous for these dynamics, as it concerns the time averages of general physical observables.
On the ergodic secrecy capacity of the wiretap channel under imperfect main channel estimation
Rezki, Zouheir
2011-11-01
The ergodic secrecy capacity of the wiretap channel is known when the main channel (between the transmitter and the legitimate receiver) state information (CSI) is perfect at the transmitter and the coherence period is sufficiently large to enable random coding arguments in each block. In a fast fading scenario, when the codeword length spans many coherence periods, the secrecy capacity is still not known. In this paper, we present a framework that characterizes this secrecy capacity under imperfect main channel estimation at the transmitter. Inner and outer bounds on the ergodic secrecy capacity are derived for a class of independent identically distributed (i.i.d.) fading channels. The achievable rate is a simple on-off scheme using a Gaussian input. The upper bound is obtained using an appropriate correlation scheme of the main and the eavesdropper channels. The upper and the lower bounds coincide with recently derived ones in the perfect main CSI extreme. Furthermore, the lower bound matches the upper bound in no main CSI extreme, where the secrecy capacity is equal to zero. Numerical results are provided for independent identically distributed (i.i.d.) Rayleigh fading channels. © 2011 IEEE.
Ergodic Capacity of Cognitive Radio Under Imperfect Channel-State Information
Rezki, Zouheir
2012-09-08
A spectrum-sharing communication system where the secondary user is aware of the instantaneous channel-state information (CSI) of the secondary link but knows only the statistics and an estimated version of the secondary transmitter-primary receiver link is investigated. The optimum power profile and the ergodic capacity of the secondary link are derived for general fading channels [with a continuous probability density function (pdf)] under the average and peak transmit power constraints and with respect to the following two different interference constraints: 1) an interference outage constraint and 2) a signal-to-interference outage constraint. When applied to Rayleigh fading channels, our results show, for example, that the interference constraint is harmful at the high-power regime, because the capacity does not increase with the power, whereas at the low-power regime, it has a marginal impact and no-interference performance, which corresponds to the ergodic capacity under average or peak transmit power constraint in the absence of the primary user, may be achieved. © 2012 IEEE.
A Unified Framework for the Ergodic Capacity of Spectrum Sharing Cognitive Radio Systems
Sboui, Lokman
2012-12-29
We consider a spectrum sharing communication scenario in which a primary and a secondary users are communicating, simultaneously, with their respective destinations using the same frequency carrier. Both optimal power profile and ergodic capacity are derived for fading channels, under an average transmit power and an instantaneous interference outage constraints. Unlike previous studies, we assume that the secondary user has a noisy version of the cross link and the secondary link Channel State Information (CSI). After deriving the capacity in this case, we provide an ergodic capacity generalization, through a unified expression, that encompasses several previously studied spectrum sharing settings. In addition, we provide an asymptotic capacity analysis at high and low signal-to-noise ratio (SNR). Numerical results, applied for independent Rayleigh fading channels, show that at low SNR regime, only the secondary channel estimation matters with no effect of the cross link on the capacity; whereas at high SNR regime, the capacity is rather driven by the cross link CSI. Furthermore, a practical on-off power allocation scheme is proposed and is shown, through numerical results, to achieve the full capacity at high and low SNR regimes and suboptimal rates in the medium SNR regime.
The influence of the dynamic ergodic divertor on the radial electric field at the Tokamak TEXTOR
Energy Technology Data Exchange (ETDEWEB)
Coenen, Jan Willem
2009-11-06
In this work the influence of external Resonant Magnetic Perturbations (RMPs) on the radial electric field Er in magnetically confined plasmas is investigated by Charge Exchange Recombination Spectroscopy (CXRS) at the Tokamak TEXTOR. Here, the RMPs are produced with the Dynamic Ergodic Divertor (DED), a set of 16 helical perturbation coils located at the high field side of TEXTOR. Within this work, the base mode number of perturbations has been m/n=6/2. We have first investigated the influence of external torque from neutral heating beams on plasma rotation and E{sub r}. The ergodic zone causes an electron loss, and subsequently a (vector)j x (vector)B force driven by the compensating ion return current. In addition, the DED changes the global confinement properties. Depending on the edge safety factor (''field line twist'') q{sub a}, either increased or decreased particle confinement is observed. In case of the increased particle confinement (IPC) the increase in density (40%) and particle confinement time {tau}{sub p} (30%) is correlated to the connection of field lines at the q=5/2 surface to the DED target, locally changing the transport properties and the E{sub r}. Transport is reduced and the E{sub r} shear is increased locally at q=5/2 up to 1.5 . 10{sup 5}s{sup -1}, while the E{sub r} becomes more positive. (orig.)
A novel image encryption scheme based on the ergodicity of baker map
Ye, Ruisong; Chen, Yonghong
2012-01-01
Thanks to the exceptionally good properties in chaotic systems, such as sensitivity to initial conditions and control parameters, pseudo-randomness and ergodicity, chaos-based image encryption algorithms have been widely studied and developed in recent years. A novel digital image encryption scheme based on the chaotic ergodicity of Baker map is proposed in this paper. Different from traditional encryption schemes based on Baker map, we permute the pixel positions by their corresponding order numbers deriving from the approximating points in one chaotic orbit. To enhance the resistance to statistical and differential attacks, a diffusion process is suggested as well in the proposed scheme. The proposed scheme enlarges the key space significantly to resist brute-force attack. Additionally, the distribution of gray values in the cipher-image has a random-like behavior to resist statistical analysis. The proposed scheme is robust against cropping, tampering and noising attacks as well. It therefore suggests a high secure and efficient way for real-time image encryption and transmission in practice.
Shyshkin, Oleg A.; Schneider, Ralf; Beidler, Craig D.
2007-11-01
The radial transport of tungsten ions in a fusion plasma of the HELIAS stellarator with five magnetic field periods is studied by means of a new numerical code. The code solves guiding center equations for test particles (tungsten ions) with the use of a Runge-Kutta integrating scheme. Coulomb scattering of the tungsten ions on the background plasma particles (electrons, deuterons and tritons) is simulated by means of a discretized collision operator based on the binomial distribution and presented in terms of pitch-angle scattering and energy slowing down and scattering. The coronal model is used to determine the mean charge state of the tungsten ion ensemble langZ(Te, ne)rang as a function of background electron temperature and density. Two plasma configurations with and without ergodic confinement regions and both with finite plasma pressure of β = 3% are considered. The nonergodic configuration possesses closed nested magnetic surfaces throughout the entire confinement volume. The ergodic magnetic field configuration is represented through additional magnetic field perturbations. Comparative analysis of the radial transport is performed for a time interval greater by a factor of 15 than the energy confinement time τE = 1.62 s required for the HELIAS reactor. In spite of the fact that the tendency of impurities to penetrate towards the plasma core is observed in both cases, the stochastic scenario exhibits reduced inward impurity flux.
On the ergodic capacity of legacy systems in the presence of next generation interference
Mahmood, Nurul Huda
2011-11-01
Next generation wireless systems facilitating better utilization of the scarce radio spectrum have emerged as a response to inefficient rigid spectrum assignment policies. These are comprised of intelligent radio nodes that opportunistically operate in the radio spectrum of existing legacy systems; yet unwanted interference at the legacy receivers is unavoidable. In order to design efficient next generation systems and to minimize their harmful consequences, it is necessary to realize their impact on the performance of legacy systems. In this work, a generalized framework for the ergodic capacity analysis of such legacy systems in the presence of interference from next generation systems is presented. The analysis is built around a model developed for the statistical representation of the interference at the legacy receivers, which is then used to evaluate the ergodic capacity of the legacy system. Moreover, this analysis is not limited to the context of legacy systems, and is in fact applicaple to any interference limited system. Findings of analytical performance analyses are confirmed through selected computer-based Monte-Carlo simulations. © 2011 IEEE.
Cochlear neuropathy and the coding of supra-threshold sound.
Bharadwaj, Hari M; Verhulst, Sarah; Shaheen, Luke; Liberman, M Charles; Shinn-Cunningham, Barbara G
2014-01-01
Many listeners with hearing thresholds within the clinically normal range nonetheless complain of difficulty hearing in everyday settings and understanding speech in noise. Converging evidence from human and animal studies points to one potential source of such difficulties: differences in the fidelity with which supra-threshold sound is encoded in the early portions of the auditory pathway. Measures of auditory subcortical steady-state responses (SSSRs) in humans and animals support the idea that the temporal precision of the early auditory representation can be poor even when hearing thresholds are normal. In humans with normal hearing thresholds (NHTs), paradigms that require listeners to make use of the detailed spectro-temporal structure of supra-threshold sound, such as selective attention and discrimination of frequency modulation (FM), reveal individual differences that correlate with subcortical temporal coding precision. Animal studies show that noise exposure and aging can cause a loss of a large percentage of auditory nerve fibers (ANFs) without any significant change in measured audiograms. Here, we argue that cochlear neuropathy may reduce encoding precision of supra-threshold sound, and that this manifests both behaviorally and in SSSRs in humans. Furthermore, recent studies suggest that noise-induced neuropathy may be selective for higher-threshold, lower-spontaneous-rate nerve fibers. Based on our hypothesis, we suggest some approaches that may yield particularly sensitive, objective measures of supra-threshold coding deficits that arise due to neuropathy. Finally, we comment on the potential clinical significance of these ideas and identify areas for future investigation.
Left Hand Dominance Affects Supra-Second Time Processing
Vicario, Carmelo Mario; Bonní, Sonia; Koch, Giacomo
2011-01-01
Previous studies exploring specific brain functions of left- and right-handed subjects have shown variances in spatial and motor abilities that might be explained according to consistent structural and functional differences. Given the role of both spatial and motor information in the processing of temporal intervals, we designed a study aimed at investigating timing abilities in left-handed subjects. To this purpose both left- and right-handed subjects were asked to perform a time reproduction of sub-second vs. supra-second time intervals with their left and right hand. Our results show that during processing of the supra-second intervals left-handed participants sub-estimated the duration of the intervals, independently of the hand used to perform the task, while no differences were reported for the sub-second intervals. These results are discussed on the basis of recent findings on supra-second motor timing, as well as emerging evidence that suggests a linear representation of time with a left-to-right displacement. PMID:22028685
Jennings, Robert C; Zucchelli, Giuseppe
2014-01-01
We examine ergodicity and configurational entropy for a dilute pigment solution and for a suspension of plant photosystem particles in which both ground and excited state pigments are present. It is concluded that the pigment solution, due to the extreme brevity of the excited state lifetime, is non-ergodic and the configurational entropy approaches zero. Conversely, due to the rapid energy transfer among pigments, each photosystem is ergodic and the configurational entropy is positive. This decreases the free energy of the single photosystem pigment array by a small amount. On the other hand, the suspension of photosystems is non-ergodic and the configurational entropy approaches zero. The overall configurational entropy which, in principle, includes contributions from both the single excited photosystems and the suspension which contains excited photosystems, also approaches zero. Thus the configurational entropy upon photon absorption by either a pigment solution or a suspension of photosystem particles is approximately zero. Copyright © 2014 Elsevier B.V. All rights reserved.
Ergodic Capacity Analysis of Free-Space Optical Links with Nonzero Boresight Pointing Errors
Ansari, Imran Shafique
2015-04-01
A unified capacity analysis of a free-space optical (FSO) link that accounts for nonzero boresight pointing errors and both types of detection techniques (i.e. intensity modulation/ direct detection as well as heterodyne detection) is addressed in this work. More specifically, an exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, we present approximate and simple closedform results for the ergodic capacity at high and low SNR regimes. All the presented results are verified via computer-based Monte-Carlo simulations.
Threshold dynamics and ergodicity of an SIRS epidemic model with Markovian switching
Li, Dan; Liu, Shengqiang; Cui, Jing'an
2017-12-01
This paper studies the spread dynamics of a stochastic SIRS epidemic model with nonlinear incidence and varying population size, which is formulated as a piecewise deterministic Markov process. A threshold dynamic determined by the basic reproduction number R0 is established: the disease can be eradicated almost surely if R0 disease persists almost surely if R0 > 1. The existing method for analyzing ergodic behavior of population systems has been generalized. The modified method weakens the required conditions and has no limitations for both the number of environmental regimes and the dimension of the considered system. When R0 > 1, the existence of a stationary probability measure is obtained. Furthermore, with the modified method, the global attractivity of the Ω-limit set of the system and the convergence in total variation to the stationary measure are both demonstrated under a mild extra condition.
The dynamic ergodic divertor in TEXTOR-A novel tool for studying magnetic perturbation field effects
International Nuclear Information System (INIS)
Neubauer, O.; Czymek, G.; Finken, K.H.; Giesen, B.; Huettemann, P.W.; Lambertz, H.T.; Schruff, J.
2005-01-01
Recently TEXTOR has been upgraded by the installation of the dynamic ergodic divertor (DED). The purpose of the DED is to influence transport parameters in plasma edge and core and to study the resulting effects on heat exhaust, edge cooling, impurity screening, plasma confinement and stability. Alternatively, the DED creates static or rotating multipolar helical magnetic perturbation fields of different mode patterns. A set of 16 helical coils has been installed on the inboard high-field side of the vacuum vessel. Rotating fields of up to 10 kHz can be generated. A novel coil design has been developed which fulfills the various mechanical, electrical, high frequency, thermal, and vacuum requirements. In addition to the various technical aspects of the DED design, implementation and commissioning, highlights of recent experiments will be presented. In particular the impact of the perturbation field on MHD stability and plasma rotation will be addressed
Escape patterns due to ergodic magnetic limiters in tokamaks with reversed magnetic shear
International Nuclear Information System (INIS)
Roberto, M.; Da Silva, E.C.; Caldas, I.L.; Viana, R.L.
2004-01-01
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)
On the continuing relevance of Mandelbrot's non-ergodic fractional renewal models of 1963 to 1967
Watkins, Nicholas W.
2017-12-01
The problem of "1/f" noise has been with us for about a century. Because it is so often framed in Fourier spectral language, the most famous solutions have tended to be the stationary long range dependent (LRD) models such as Mandelbrot's fractional Gaussian noise. In view of the increasing importance to physics of non-ergodic fractional renewal models, and their links to the CTRW, I present preliminary results of my research into the history of Mandelbrot's very little known work in that area from 1963 to 1967. I speculate about how the lack of awareness of this work in the physics and statistics communities may have affected the development of complexity science, and I discuss the differences between the Hurst effect, "1/f" noise and LRD, concepts which are often treated as equivalent. Contribution to the "Topical Issue: Continuous Time Random Walk Still Trendy: Fifty-year History, Current State and Outlook", edited by Ryszard Kutner and Jaume Masoliver.
Outage Probability and Ergodic Capacity of Spectrum-Sharing Systems with MRC Diversity
Jarrouj, Jiana; Blagojevic, Vesna; Ivanis, Predrag
2016-03-01
The spectrum sharing system employing maximum ratio combining (MRC) is analyzed in Nakagami fading environment, for the case when the interference from the primary user is present at the input of the secondary user receiver. The closed-form expressions for the probability density function of the signal-to-interference-and-noise ratio, the outage probability and the ergodic capacity of the SU link are derived under both peak interference and maximal transmit power constraints. Asymptotical expressions are provided for the important region where peak interference power constraint dominates and the case when the interference from the primary user's is dominant compared to the noise at the secondary user's receiver. The obtained expressions are presented for both cases of outdated and mean-value based power allocation and verified by using Monte Carlo simulation method.
International Nuclear Information System (INIS)
Takesue, Shinji
1989-01-01
This is the first part of a series devoted to the study of thermodynamic behavior of large dynamical systems with the use of a family of full-discrete and conservative models named elementary reversible cellular automata (ERCAs). In this paper, basic properties such as conservation laws and phase space structure are investigated in preparation for the later studies. ERCAs are a family of one-dimensional reversible cellular automata having two Boolean variables on each site. Reflection and Boolean conjugation symmetries divide them into 88 equivalence classes. For each rule, additive conserved quantities written in a certain form are regarded as a kind of energy, if they exist. By the aid of the discreteness of the variables, every ERCA satisfies the Liouville theorem or the preservation of phase space volume. Thus, if an energy exists in the above sense, statistical mechanics of the model can formally be constructed. If a locally defined quantity is conserved, however, it prevents the realization of statistical mechanics. The existence of such a quantity is examined for each class and a number of rules which have at least one energy but no local conservation laws are selected as hopeful candidates for the realization of thermodynamic behavior. In addition, the phase space structure of ERCAs is analyzed by enumerating cycles exactly in the phase space for systems of comparatively small sizes. As a result, it is revealed that a finite ERCA is not ergodic, that is, a large number of orbits coexist on an energy surface. It is argued that this fact does not necessarily mean the failure of thermodynamic behavior on the basis of an analogy with the ergodic nature of infinite systems
Flow and transport in digitized images of Berea sandstone: ergodicity, stationarity and upscaling
Puyguiraud, A.; Dentz, M.; Gouze, P.
2017-12-01
We perform Stokes flow simulations on digitized images of a Berea sandstone sample obtained through micro-tomography imaging and segmentation processes. We obtain accurate information on the transport using a streamline reconstruction algorithm which uses the velocity field obtained from the flow simulation as input data. This technique is based on the method proposed by Pollock (Groundwater, 1988) but employs a quadratic interpolation near the rock mesh cells of the domain similarly to Mostaghimi et al. (SPE, 2012). This allows an accurate resolution of the velocity field near the solid interface which plays an important role on the transport characteristics, such as the probability density of first arrival times and the growth of the mean squared displacement, among others, which exhibit non-Fickian behavior. We analyze Lagrangian and Eulerian velocity statistics and their relation, and then focus on the ergodicity and the stationarity properties of the transport.We analyze the temporal evolution of Lagrangian velocity statistics for different injection conditions, and findd quick convergence to a limiting velocity distribution, indicating the transport to be near-stationary. The equivalence between velocity samplings within and across streamlines, as well as the independency of the statistics on the number of sampled streamlines, lead as to conclude that the transport may be modeled as ergodic.These characteristics then allow us to upscale the 3-dimensional simulations using a 1-dimensional Continuous Time Random Walk model. This model, parametrized by the velocity results and the characteristic correlation length obtained from the above mentioned simulations, is able to efficiently reproduce the results and to predict larger scale behaviors.
Ergodicity of Truncated Stochastic Navier Stokes with Deterministic Forcing and Dispersion
Majda, Andrew J.; Tong, Xin T.
2016-10-01
Turbulence in idealized geophysical flows is a very rich and important topic. The anisotropic effects of explicit deterministic forcing, dispersive effects from rotation due to the β -plane and F-plane, and topography together with random forcing all combine to produce a remarkable number of realistic phenomena. These effects have been studied through careful numerical experiments in the truncated geophysical models. These important results include transitions between coherent jets and vortices, and direct and inverse turbulence cascades as parameters are varied, and it is a contemporary challenge to explain these diverse statistical predictions. Here we contribute to these issues by proving with full mathematical rigor that for any values of the deterministic forcing, the β - and F-plane effects and topography, with minimal stochastic forcing, there is geometric ergodicity for any finite Galerkin truncation. This means that there is a unique smooth invariant measure which attracts all statistical initial data at an exponential rate. In particular, this rigorous statistical theory guarantees that there are no bifurcations to multiple stable and unstable statistical steady states as geophysical parameters are varied in contrast to claims in the applied literature. The proof utilizes a new statistical Lyapunov function to account for enstrophy exchanges between the statistical mean and the variance fluctuations due to the deterministic forcing. It also requires careful proofs of hypoellipticity with geophysical effects and uses geometric control theory to establish reachability. To illustrate the necessity of these conditions, a two-dimensional example is developed which has the square of the Euclidean norm as the Lyapunov function and is hypoelliptic with nonzero noise forcing, yet fails to be reachable or ergodic.
ESEM modifications to LEO SUPRA 35 VP FESEM.
Dracopoulos, Vassileios; Danilatos, Gerasimos
2013-01-01
A LEO SUPRA 35 VP FESEM has been modified to significantly improve image quality in the low pressure mode of operation. It is further shown that the same conversion can allow the machine to operate also as a fully fledged environmental scanning electron microscope with specimen chamber pressures in excess of 2000 Pa. This is achieved by a diamagnetic insert with a thin pressure limiting aperture at the bottom of the pole-piece. The insert allows the use of various size apertures in addition to the existing 1 mm differential diaphragm. Copyright © 2012 Elsevier Ltd. All rights reserved.
Regional Themes and Global Means in Supra-National Higher Education Policy
Watson, Pam
2009-01-01
The supra-national level has become increasingly important in educational policy formulation. This paper describes and compares two settings in which growth in these supra-national policies is evident--in Europe and in Africa. Key themes arising in policy documents in each context are examined. A distinction is drawn in analysis between themes…
Atypical initial presentation of Takayasu arteritis as isolated supra-valvular aortic stenosis.
Kim, Do Yeon; Kim, Hwan Wook
2016-01-19
Among the vascular involvements of Takayasu arteritis, a supra-valvular aortic stenosis has been reported very rarely. We report a case of surgically corrected, supra-valvular aortic stenosis caused by Takayasu arteritis. A 32-year-old female was diagnosed with supra-valvular aortic stenosis by transthoracic echocardiography for the evaluation of cardiac murmur with constitutional symptoms. Under the impression of non-familial sporadic type of supra-valvular aortic stenosis, surgical correction was performed. However, after 1 year from the operation, we could know the cause of her disease through the findings of computed tomographic aortography that Takayasu arteritis was suspected. Takayasu arteritis should be considered in adult female patients presenting supra-valvular aortic stenosis with constitutional symptoms, even if no typical features of vascular involvement.
Duration Adaptation Occurs Across the Sub- and Supra-Second Systems.
Shima, Shuhei; Murai, Yuki; Hashimoto, Yuki; Yotsumoto, Yuko
2016-01-01
After repetitive exposure to a stimulus of relatively short duration, a subsequent stimulus of long duration is perceived as being even longer, and after repetitive exposure to a stimulus of relatively long duration, a subsequent stimulus of short duration is perceived as being even shorter. This phenomenon is called duration adaptation, and has been reported only for sub-second durations. We examined whether duration adaptation also occurs for supra-second durations (Experiment 1) and whether duration adaptation occurs across sub- and supra-second durations (Experiment 2). Duration adaptation occurred not only for sub-second durations, but also for supra-second durations and across sub- and supra-second durations. These results suggest that duration adaptation involves an interval-independent system or two functionally related systems that are associated with both the sub- and supra-second durations.
Czech Academy of Sciences Publication Activity Database
Shaffer, Christopher; Révész, Agnes; Schröder, Detlef; Severa, Lukáš; Teplý, Filip; Zins, E. L.; Jašíková, L.; Roithová, J.
2012-01-01
Roč. 51, č. 40 (2012), s. 10050-10053 ISSN 1433-7851 R&D Projects: GA ČR GAP207/10/2391 Grant - others:European Research Council(XE) StG ISORI; European Research Council(XE) AdG HORIZOMS Institutional support: RVO:61388963 Keywords : IR spectroscopy * ion pairs * non-ergodic behavior * ions * triflate * pyridinium ions Subject RIV: CC - Organic Chemistry Impact factor: 13.734, year: 2012
Földes-Papp, Zeno; Baumann, Gerd
2011-05-01
We present a new approach to distinguish between non-ergodic and ergodic behavior. Performing ensemble averaging in a subpopulation of individual molecules leads to a mean value that can be similar to the mean value obtained in an ergodic system. The averaging is carried out by minimizing the variation between the sum of the temporal averaged mean square deviation of the simulated data with respect to the logarithmic scaling behavior of the subpopulation. For this reason, we first introduce a kind of Continuous Time Random Walks (CTRW), which we call Limited Continuous Time Random Walks (LCTRW) on fractal support. The random waiting time distributions are sampled at points which fulfill the condition N <1, where N is the Poisson probability of finding a single molecule in the femtoliter-sized observation volume ΔV at the single-molecule level. Given a subpopulation of different single molecules of the same kind, the ratio T/ T(m) between the measurement time T and the meaningful time T(m), which is the time for observing just one and the same single molecule, is the experimentally accessible quantity that allows to compare different molecule numbers in the subpopulation. In addition, the mean square displacement traveled by the molecule during the time t is determined by an upper limit of the geometric dimension of the living cell or its nucleus.
Simultaneous multifractal decompositions for the spectra of local entropies and ergodic averages
International Nuclear Information System (INIS)
Meson, Alejandro; Vericat, Fernando
2009-01-01
We consider different multifractal decompositions of the form K α i ={x:g i (x)=α i },i=1,2,...,d, and we study the dimension spectrum corresponding to the multiparameter decomposition K α = intersection i=1 d K α i ,α=(α 1 ,...,α d ). Then for an homeomorphism f : X → X and potentials φ, ψ : X → R we analyze the decompositions K α + ={x:lim n→∞ 1/n (S n + (φ))(x)=α},K β - ={x:lim n→∞ 1/n (S n - (ψ))(x)=β}, where 1/n (S n + (φ)),1/n (S n - (ψ)) are ergodic averages using forward and backward orbits of f respectively. We must emphasize that the analysis, in any case, is done without requiring conditions of hyperbolicity for the dynamical system or Hoelder continuity on the potentials. We illustrate with an application to galactic dynamics: a set of stars (which do not interact among them) moving in a galactic field.
The ergodic limit of multipass absorption for fast wave current drive in tokamaks
Kupfer, K.; Forest, C. B.; Petty, C. C.; Pinsker, R. I.
1994-12-01
In many parameter regimes of interest for fast wave current drive (FWCD) in tokamaks, direct absorption of the fast wave by resonant electrons is a weak process and multipass absorption is an important issue. Although both full wave codes and ray tracing codes have been developed to model FWCD, in the multipass regime these tools are computationally intensive, and yield little insight into the nature of the solutions. In this work, an alternative approach is considered. Based on the wave kinetic equation, a natural limit emerges for the multipass regime, where wave energy density, convected along stochastic ray trajectories, uniformly fills the entire accessible phase space. In this ergodic, weak damping limit, the absorbed power density and corresponding wave-driven current density are readily obtained by calculating the appropriate set of one-dimensional k-space integrals at every point in configuration space. The method is used here to model FWCD on the DIII-D tokamak [R. I. Pinsker and the DIII-D Team, Plasma Physics and Controlled Nuclear Fusion Research 1992 (International Atomic Energy Agency, Vienna, 1993), Vol. 1, p. 683]. An example for reactor-grade plasma parameters is also considered.
Public-Private Partnerships (PPP on moulding state structures: The Non-Ergodic Africa
Directory of Open Access Journals (Sweden)
Fred Amonya
2016-10-01
Full Text Available Public-Private Partnerships (PPP is a ubiquitous reality. In Africa, the wave of PPP has hit states in their infancy – still moulding following only 50 years since independence. The common perspective of PPP on the realms of scholarship is transactional (focused on the delivery-end of infrastructure. This paper presents a deeper and broader perspective, and it is a distillate of a case study on PPP as a policy phenomenon. It dissects and illuminates the interaction between the forces of state formation and the wave of PPP hitting the continent. The lens of this case study is Institutional Rational Choice (IRC. The tools are a variety, comprising textual analysis, hermeneutics and econometrics – in keeping with the essence of case study (explication of reality in-situ. The product is not the orthodox generalization (claiming ‘the way’. Instead, the explication offers a viewpoint (and trigger questions on public space of Africa, while underpinning the non-ergodic character of that space
On the ergodic secret message capacity of the wiretap channel with finite-rate feedback
Rezki, Zouheir
2012-07-01
We study the secret message capacity of an ergodic block fading wiretap channel with partial channel state information at the transmitter and perfect channel state information at the receivers. We consider that in addition to the statistics of the main and the eavesdropper channel state information (CSI), the sender is provided by the legitimate receiver with a q-bit feedback, at the beginning of each coherence block, through an error-free feedback channel, with capacity q bits. We establish upper and lower bounds on the secrecy capacity. We show that a positive secrecy rate is achievable even when the feedback is at the end of each coherence block and q = 1. We also show that the lower and the upper bounds coincide asymptotically as q → ∞. Finally, asymptotic analysis at high Signal-to-Noise Ratio (SNR) are presented where it is found that the capacity is bounded at high-SNR and present a simple suboptimal scalar quantizer that is capacity achieving, without the need of any numerical optimization, as q → ∞. When applied to Rayleigh fading channels, we show that, at high-SNR, a 4-bit feedback achieves 90% of the secrecy capacity when perfect main CSI is available at the transmitter. © 2012 IEEE.
Geometric ergodicity of a hybrid sampler for Bayesian inference of phylogenetic branch lengths.
Spade, David A; Herbei, Radu; Kubatko, Laura S
2015-10-01
One of the fundamental goals in phylogenetics is to make inferences about the evolutionary pattern among a group of individuals, such as genes or species, using present-day genetic material. This pattern is represented by a phylogenetic tree, and as computational methods have caught up to the statistical theory, Bayesian methods of making inferences about phylogenetic trees have become increasingly popular. Bayesian inference of phylogenetic trees requires sampling from intractable probability distributions. Common methods of sampling from these distributions include Markov chain Monte Carlo (MCMC) and Sequential Monte Carlo (SMC) methods, and one way that both of these methods can proceed is by first simulating a tree topology and then taking a sample from the posterior distribution of the branch lengths given the tree topology and the data set. In many MCMC methods, it is difficult to verify that the underlying Markov chain is geometrically ergodic, and thus, it is necessary to rely on output-based convergence diagnostics in order to assess convergence on an ad hoc basis. These diagnostics suffer from several important limitations, so in an effort to circumvent these limitations, this work establishes geometric convergence for a particular Markov chain that is used to sample branch lengths under a fairly general class of nucleotide substitution models and provides a numerical method for estimating the time this Markov chain takes to converge. Copyright © 2015 Elsevier Inc. All rights reserved.
Tore Linné Eriksen og de store utviklingsspørsmålene
Directory of Open Access Journals (Sweden)
Kristen Nordhaug
2015-10-01
Full Text Available This article reviews some of Tore Linné Eriksen’s works within development studies/development research. In a recent introduction to development studies from 2013, he presented development research as a cross-disciplinary social science approach that addresses the grand problems of mankind. Eriksen’s own research into these grand problems has concentrated on the causes of national and international inequality and poverty. In 1974 he supported the view of the “underdevelopment school”: “Underdevelopment” in Africa and Latin America was the outcome of the inclusion of those continents in a capitalist world economy dominated by Europe. Recent works by Eriksen on the origins of the “great divergence” between Western Europe and economically advanced non-European countries (2010 and on inequality and poverty in the current world (2012 are far more complex and empirically nuanced. Still, in a recent discussion of globalization and global capitalism (2013 he reverts to some of the earlier ”underdevelopment arguments” from 1974. The article concludes that there is a tension within Eriksen’s works on the role of capitalism in development and underdevelopment. In his programmatic writings, global capitalism is seen as the main cause of inequality and poverty. In his more empirically grounded works, global capitalism is viewed rather as an important part of the bigger picture of inequality and poverty.
Measurements of earplug attenuation under supra-aural and circumaural headphones.
Tufts, Jennifer B; Palmer, Jillian V; Marshall, Lynne
2012-10-01
Supra-aural audiometric headphones are generally not recommended for use in measuring the attenuation of earplugs, because contact between the headphone and pinna and/or earplug could alter the attenuation obtained, and because of concerns of non-comparability between modes of excitation from supra-aural headphones and the sound-field procedure required by the standardized method. In this study, we compared measurements of earplug attenuation obtained under Telephonics TDH-50P supra-aural headphones with measurements obtained under circumaural headphones designed expressly for such testing. The attenuation of three types of earplugs (foam, premolded quadruple-flange, and custom-molded) was measured in a repeated-measures design. The study sample comprised 42 normal-hearing adults (21 females, 21 males). With the foam earplugs, nearly all of the attenuation measurements under the supra-aural headphones fell within 10 dB of the measurements under the circumaural headphones. With the flange and custom earplugs, approximately 10% of individuals obtained spuriously high attenuation under the supra-aural headphones. We conclude that standard supra-aural audiometric headphones are suitable for measuring the attenuation provided by foam earplugs. However, supra-aural headphones should not be used to measure the attenuation of flange or custom-molded earplugs. The potential exists for substantial over-estimation of attenuation, especially of custom plugs.
Gonzalez-Lopez, David; Faerber, Gloria; Diab, Mahmoud; Amorim, Paulo; Zeynalov, Natig; Doenst, Torsten
2017-10-01
Current sizing strategies suggest valve selection based on annulus diameter despite supra-annular placement of biological prostheses potentially allowing placement of a larger size. We assessed the frequency of selecting a larger prosthesis if prosthesis size was selected using a replica (upsizing) and evaluated its impact on haemodynamics. We analysed all discharge echocardiograms between June 2012 and June 2014, where a replica sizer was used for isolated aortic valve replacement (Epic Supra: 266 patients, Trifecta: 49 patients). Upsizing was possible in 71% of the Epic Supra valves (by 1 size: 168, by 2 sizes: 20) and in 59% of the Trifectas (by 1 size: 26, by 2 sizes: 3). Patients for whom upsizing was possible had the lowest pressure gradients within their annulus size groups. The difference was significant in annulus diameters of 21-22 or 25-26 mm (Epic Supra) and 23-24 mm (Trifecta). Trifecta gradients were the lowest. However, the ability to upsize the Epic Supra by 2 sizes eliminated the differences between Epic Supra and Trifecta. Upsizing did not cause intraoperative complications. Using replica sizers for aortic prosthesis size selection allows the implantation of bigger prostheses than recommended in most cases and reduces postoperative gradients, specifically for Epic Supra. © The Author 2017. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
Distinguishing Between Supra-Arcade Downflows and Plasmoids
Savage, Sabrina
2015-01-01
Supra-arcade downflows (SADs) and downflowing loops (SADLs), observed as sunward-traveling voids and thin flux tubes in the current sheet region above developing flare arcades, are considered indicators of magnetic reconnection fueling long-duration solar eruptions. These flows are located in regions of very low signal-to-noise in the corona where high cadence magnetic field measurements are not yet achievable, making observations difficult to fully interpret with respect to reconnection. Several models have been developed to explain their characteristics and behaviors, but most do not successfully recreate the observations. We will present a variety of downflow observations and provide comparisons to a number of the more prominent models.
Bistability, non-ergodicity, and inhibition in pairwise maximum-entropy models.
Rostami, Vahid; Porta Mana, PierGianLuca; Grün, Sonja; Helias, Moritz
2017-10-01
Pairwise maximum-entropy models have been used in neuroscience to predict the activity of neuronal populations, given only the time-averaged correlations of the neuron activities. This paper provides evidence that the pairwise model, applied to experimental recordings, would produce a bimodal distribution for the population-averaged activity, and for some population sizes the second mode would peak at high activities, that experimentally would be equivalent to 90% of the neuron population active within time-windows of few milliseconds. Several problems are connected with this bimodality: 1. The presence of the high-activity mode is unrealistic in view of observed neuronal activity and on neurobiological grounds. 2. Boltzmann learning becomes non-ergodic, hence the pairwise maximum-entropy distribution cannot be found: in fact, Boltzmann learning would produce an incorrect distribution; similarly, common variants of mean-field approximations also produce an incorrect distribution. 3. The Glauber dynamics associated with the model is unrealistically bistable and cannot be used to generate realistic surrogate data. This bimodality problem is first demonstrated for an experimental dataset from 159 neurons in the motor cortex of macaque monkey. Evidence is then provided that this problem affects typical neural recordings of population sizes of a couple of hundreds or more neurons. The cause of the bimodality problem is identified as the inability of standard maximum-entropy distributions with a uniform reference measure to model neuronal inhibition. To eliminate this problem a modified maximum-entropy model is presented, which reflects a basic effect of inhibition in the form of a simple but non-uniform reference measure. This model does not lead to unrealistic bimodalities, can be found with Boltzmann learning, and has an associated Glauber dynamics which incorporates a minimal asymmetric inhibition.
Ergodic secret message capacity of the wiretap channel with finite-rate feedback
Rezki, Zouheir
2014-06-01
We study the secret message capacity of an ergodic block fading wiretap channel with partial channel state information at the transmitter and perfect channel state information at the receivers, under both a short term power constraint (STPC) and a long term power constraint (LTPC). We consider that in addition to the statistics of the main and the eavesdropper channel state information (CSI), the sender is provided by the legitimate receiver with a q-bit feedback, at the beginning of each coherence block, through an error-free public channel, with capacity q bits. We establish upper and lower bounds on the secrecy capacity. We show that the lower and the upper bounds coincide asymptotically as q → ∞. When applied to Rayleigh fading channels, we show that, a 4-bit feedback achieves about 90% of the secrecy capacity when perfect main CSI is available at the transmitter. Finally, asymptotic analysis at high and low Signal-to-Noise Ratio (SNR) is presented. It is found that the capacity is bounded at high-SNR, whereas at asymptotically low-SNR, the lower bounds and the upper bound scale linearly with SNR under STPC. Furthermore, subject to LTPC, the capacity at low-SNR is equal to the capacity of the main channel without secrecy constraint and with perfect CSI at both the transmitter and the receiver, under a mild condition on the fading statistics. We also show that a positive secrecy rate is achievable even when the feedback is at the end of each coherence block and q=1. © 2002-2012 IEEE.
Supra-amphiphiles: a new bridge between colloidal science and supramolecular chemistry.
Kang, Yuetong; Liu, Kai; Zhang, Xi
2014-06-03
In addition to conventional amphiphiles, an emerging research area is supra-amphiphiles, which are constructed on the basis of noncovalent interactions and dynamic covalent bonds. In this feature article, we have provided a general introduction to the concept, design principles, and topologies of supra-amphiphiles, starting from some rationally tailored building blocks. In addition, we highlight some progress in the functional assembly of supra-amphiphiles, such as responsive nanoscale carriers, antibacterial and antitumor agents, fluorescent-based chemical sensors, and enzyme mimics. The supra-amphiphile is a new bridge between colloidal science and supramolecular chemistry, and it is a field where we can make full use of our imaginative power.
Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve
DEFF Research Database (Denmark)
Aagaard, Jan; Geha, Alexander S.
2007-01-01
BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area....... This study evaluates the authors' clinical experience with Top Hat supra-annular aortic valve size selection, and the technical aspects of implantation. METHODS: Between January 1999 and October 2005, a total of 251 consecutive patients underwent 252 aortic valve replacements with Top Hat supra...... required unplanned coronary bypass, and 30-day mortality was 2.0% (5/251), indicating a good safety profile for the valves implanted in this series. CONCLUSION: The general distribution of implant sizes in the US indicates that cardiac surgeons may be under-sizing the Top Hat supra-annular aortic valve...
Can the nuclear symmetry potential at supra-saturation densities be negative?
International Nuclear Information System (INIS)
Yong Gaochan
2010-01-01
In the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, for the central 197 Au+ 197 Au reaction at an incident beam energy of 400 MeV/nucleon, the effect of nuclear symmetry potential at supra-saturation densities on the preequilibrium clusters emission is studied. It is found that for the positive symmetry potential at supra-saturation densities the neutron-to-proton ratio of lighter clusters with mass number A≤3[(n/p) A≤3 ] is larger than that of the heavier clusters with mass number A>3[(n/p) A>3 ], whereas for the negative symmetry potential at supra-saturation densities the (n/p) A≤3 is smaller than the (n/p) A>3 . This may be considered as a probe of the negative symmetry potential at supra-saturation densities.
Supra-annular valve strategy for an early degenerated transcatheter balloon-expandable heart valve.
Kamioka, Norihiko; Caughron, Hope; Corrigan, Frank; Block, Peter; Babaliaros, Vasilis
2018-01-23
Currently, there are no recommendations regarding the selection of valve type for a transcatheter heart valve (THV)-in-THV procedure. A supra-annular valve design may be superior in that it results in a larger effective orifice area and may have a lower chance of valve thrombosis after THV-in-THV. In this report, we describe the use of a supra-annular valve strategy for an early degenerated THV. © 2018 Wiley Periodicals, Inc.
Sindier Antônia Alves; Heitor Garcia de Carvalho
2011-01-01
: In this article, the way digital libraries are used by undergraduate students of a Pedagogy degree in a Distance Education program is researched through concepts such as digital library, print library, and informational behavior. Based uponEspen Aarseth’s Theory of Ergodic Literature, this research consisted of some semi-structured interviews aiming at checking how the digital library was used in this program. The collected data showed that students did have access to technology, however t...
H-shaped supra-amphiphiles based on a dynamic covalent bond.
Wang, Guangtong; Wang, Chao; Wang, Zhiqiang; Zhang, Xi
2012-10-16
The imine bond, a kind of dynamic covalent bond, is used to bind two bolaform amphiphiles together with spacers, yielding H-shaped supra-amphiphiles. Micellar aggregates formed by the self-assembly of the H-shaped supra-amphiphiles are observed. When pH is tuned down from basic to slightly acidic, the benzoic imine bond can be hydrolyzed, leading to the dissociation of H-shaped supra-amphiphiles. Moreover, H-shaped supra-amphiphiles have a lower critical micelle concentration than their building blocks, which is very helpful in enhancing the stability of the benzoic imine bond being hydrolyzed by acid. The surface tension isotherms of the H-shaped supra-amphiphiles with different spacers indicate their twisty conformation at a gas-water interface. The study of H-shaped supra-amphiphiles can enrich the family of amphiphiles, and moreover, the pH-responsiveness may make them apply to controlled or targetable drug delivery in a biological environment.
Kimura, Miwako; Sakakibara, Ken-Ichi; Imagawa, Hiroshi; Chan, Roger; Niimi, Seijii; Tayama, Niro
2002-11-01
Phonation is the vocal fold vibration on normal voice. But sometimes we can observe the other phonation styles like as the pressed voice or some throat singings like as ''kargyraa'' or ''drone'' in Khoomei in Mongolian music. Also, clinically, we know that some patients who have the wide glottal slit in phonation because of the recurrence nerve palsy or after partial laryngectomy, could make the ''supra-glottal phonation.'' The ''supra-glottal phonation'' would be made from the vibration of ''supra-glottal structures'' such as the false vocal folds, the arytenoids and the epiglottis, etc. Endoscopic examination suggests the existence of some contractile functions in supra-glottal space. However, these phonation systems have not been clear to explain their neuromuscular mechanism in histology. This study aimed to find the basis for making the supra-glottal phonation from the points of view of the histological structures. We tried to investigate if there were any muscles that could contract the supra-glottal structures. The samples are the excised larynx of human beings. They were fixed by formalin after excision. We observed their macroscopic anatomy, and also with the microscopic observation their histological preparations after the process of the embedding in paraffin, slicing for the preparation and HE (hematoxylin-eosin) staining.
Supra- and infra-torcular double occipital encephalocele.
Canaz, Hüseyin; Ayçiçek, Ezgi; Akçetin, Mustafa Ali; Akdemir, Osman; Alataş, Ibrahim; Özdemir, Bülent
2015-01-01
An encephalocele is a protrusion of the brain and/or meninges through a defect in the skull that is closed or covered with skin. Occipital encephaloceles are the most frequent type in North America and Western Europe, where about 85% of encephaloceles take this form. To the best of our knowledge, there are only three other reported cases of double occipital encephaloceles in the literature. The current study reports a double and both supra- and infra-torcular occipital encephalocele in a neonate and discusses the importance of preoperative neuroimaging studies to optimize the outcome. The patient was a 1-day-old male child who was identified by prenatal ultrasound to have two occipital encephaloceles. The patient underwent a closure of the occipital encephalocele on the second postnatal day. The infant tolerated the procedure well and was extubated on the first postoperative day. The child continues to do well during follow-up. Copyright © 2014 Sociedad Española de Neurocirugía. Published by Elsevier España. All rights reserved.
Supra-galactic colour patterns in globular cluster systems
Forte, Juan C.
2017-07-01
An analysis of globular cluster systems associated with galaxies included in the Virgo and Fornax Hubble Space Telescope-Advanced Camera Surveys reveals distinct (g - z) colour modulation patterns. These features appear on composite samples of globular clusters and, most evidently, in galaxies with absolute magnitudes Mg in the range from -20.2 to -19.2. These colour modulations are also detectable on some samples of globular clusters in the central galaxies NGC 1399 and NGC 4486 (and confirmed on data sets obtained with different instruments and photometric systems), as well as in other bright galaxies in these clusters. After discarding field contamination, photometric errors and statistical effects, we conclude that these supra-galactic colour patterns are real and reflect some previously unknown characteristic. These features suggest that the globular cluster formation process was not entirely stochastic but included a fraction of clusters that formed in a rather synchronized fashion over large spatial scales, and in a tentative time lapse of about 1.5 Gy at redshifts z between 2 and 4. We speculate that the putative mechanism leading to that synchronism may be associated with large scale feedback effects connected with violent star-forming events and/or with supermassive black holes.
Study of the radiation in divertor plasmas; Etude du rayonnement dans les plasmas de divertor
Energy Technology Data Exchange (ETDEWEB)
Laugier, F
2000-10-19
We have studied the cooling of the edge plasma by radiation in the divertor volume, in order to optimize the extraction of power in tokamaks and to limit the wall erosion. In attached divertor plasmas experiments, the concentration of intrinsic impurities at the edge is related to the response of the wall to the incident energy flow of plasma, depending on a phenomenological law. We carried out an analysis of the radiation according to this law and to the control parameters of the discharges. The largest radiated fraction and best synergy are obtained when the concentration of intrinsic impurities strongly increases with the energy of incident plasma. On the other hand, the erosion of the wall is stronger. In detached plasmas, we proved that the performances in terms of incident plasma energy loss and pressure loss are optimal when the density of the slowest neutrals is strong at the edge and when their radial penetration is small. On Tore Supra, we highlighted the correlations between the maximum Mach number of incident plasma flow, the radiation front and the penetration of the neutrals. A simple diagnostic based on the localization of the maximum Mach number proves that detached mode is not optimal on Tore Supra, because the radial penetration of the slowest neutrals is not sufficiently small. In the last part, we obtained the three-dimensional topology of the radiation in the ergodic divertor using a spectral analysis code and boundary conditions consistent with the temperature distribution on the wall. The radiation is maximum in front of the divertor modules. As a consequence, radiated power is underestimated by standards measurements of Tore Supra that are located between the modules. We finally showed that the profiles of temperature along the field lines are modulated, this is specific to the ergodic divertor. (author)
Energy Technology Data Exchange (ETDEWEB)
Kuehn, Lars; Haas, Oliver de [evico GmbH, Dresden (Germany); Berger, Dietmar; Schultz, Ludwig [IFW Dresden (Germany); Olsen, Henning; Roehlig, Steffen [ELBAS Elektrische Bahnsysteme Ingenieur-Gesellschaft mbH, DNV company, Dresden (Germany)
2012-08-15
The SupraTrans system was further developed and a test drive facility built up in Dresden. The latter permits complex drive tests to be made as well as the testing of components. Compared to the demonstrator, the facility is characterized by a higher loadability, higher speeds and a completely contactless energy transmission. (orig.)
International Nuclear Information System (INIS)
Littlefield, R.G.
1976-01-01
Velocity spectra of supra-thermal electrons escaping from a low-pressure radio-frequency discharge in air have been measured by a time-of-flight method of original design. In addition, the energy spectra of the supra-thermal electrons and positive ions escaping from the rf discharge have been measured by a retarding potential method. Various parameters affecting the energy of the supra-thermal charged particles are experimentally investigated. A model accounting for the supra-thermal charged particle energies is developed and is shown to be consistent with experimental observations
Thermodynamics of supra-arcade downflows in solar flares
Chen, Xin; Liu, Rui; Deng, Na; Wang, Haimin
2017-10-01
Context. Supra-arcade downflows (SADs) have been frequently observed during the gradual phase of solar flares near the limb. In coronal emission lines sensitive to flaring plasmas, they appear as tadpole-like dark voids against the diffuse fan-shaped "haze" above, flowing toward the well-defined flare arcade. Aims: We aim to investigate the evolution of SADs' thermal properties, and to shed light on the formation mechanism and physical processes of SADs. Methods: We carefully studied several selected SADs from two flare events and calculated their differential emission measures (DEMs) as well as DEM-weighted temperatures using data obtained by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamic Observatory. Results: Our analysis shows that SADs are associated with a substantial decrease in DEM above 4 MK, which is 1-3 orders of magnitude smaller than the surrounding haze as well as the region before or after the passage of SADs, but comparable to the quiet corona. There is no evidence for the presence of the SAD-associated hot plasma (>20 MK) in the AIA data, and this decrease in DEM does not cause any significant change in the DEM distribution as well as the DEM-weighted temperature, which supports this idea that SADs are density depletion. This depression in DEM rapidly recovers in the wake of the SADs studied, generally within a few minutes, suggesting that they are discrete features. In addition, we found that SADs in one event are spatio-temporally associated with the successive formation of post-flare loops along the flare arcade. Movies associated to Figs. A.1 and A.2 are available at http://www.aanda.org
Amphiphilic building blocks for self-assembly: from amphiphiles to supra-amphiphiles.
Wang, Chao; Wang, Zhiqiang; Zhang, Xi
2012-04-17
The process of self-assembly spontaneously creates well-defined structures from various chemical building blocks. Self-assembly can include different levels of complexity: it can be as simple as the dimerization of two small building blocks driven by hydrogen bonding or as complicated as a cell membrane, a remarkable supramolecular architecture created by a bilayer of phospholipids embedded with functional proteins. The study of self-assembly in simple systems provides a fundamental understanding of the driving forces and cooperativity behind these processes. Once the rules are understood, these guidelines can facilitate the research of highly complex self-assembly processes. Among the various components for self-assembly, an amphiphilic molecule, which contains both hydrophilic and hydrophobic parts, forms one of the most powerful building blocks. When amphiphiles are dispersed in water, the hydrophilic component of the amphiphile preferentially interacts with the aqueous phase while the hydrophobic portion tends to reside in the air or in the nonpolar solvent. Therefore, the amphiphiles aggregate to form different molecular assemblies based on the repelling and coordinating forces between the hydrophilic and hydrophobic parts of the component molecules and the surrounding medium. In contrast to conventional amphiphiles, supra-amphiphiles are constructed on the basis of noncovalent interactions or dynamic covalent bonds. In supra-amphiphiles, the functional groups can be attached to the amphiphiles by noncovalent synthesis, greatly speeding their construction. The building blocks for supra-amphiphiles can be either small organic molecules or polymers. Advances in the development of supra-amphiphiles will not only enrich the family of conventional amphiphiles that are based on covalent bonds but will also provide a new kind of building block for the preparation of complex self-assemblies. When polymers are used to construct supra-amphiphiles, the resulting
Pyrosequencing of supra- and subgingival biofilms from inflamed peri-implant and periodontal sites.
Schaumann, Simone; Staufenbiel, Ingmar; Scherer, Ralph; Schilhabel, Markus; Winkel, Andreas; Stumpp, Sascha Nico; Eberhard, Jörg; Stiesch, Meike
2014-12-17
To investigate the microbial composition of biofilms at inflamed peri-implant and periodontal tissues in the same subject, using 16S rRNA sequencing. Supra- and submucosal, and supra- and subgingival plaque samples were collected from 7 subjects suffering from diseased peri-implant and periodontal tissues. Bacterial DNA was isolated and 16S rRNA genes were amplified, sequenced and aligned for the identification of bacterial genera. 43734 chimera-depleted, denoised sequences were identified, corresponding to 1 phylum, 8 classes, 10 orders, 44 families and 150 genera. The most abundant families or genera found in supramucosal or supragingival plaque were Streptoccocaceae, Rothia and Porphyromonas. In submucosal plaque, the most abundant family or genera found were Rothia, Streptococcaceae and Porphyromonas on implants. The most abundant subgingival bacteria on teeth were Prevotella, Streptococcaceae, and TG5. The number of sequences found for the genera Tannerella and Aggregatibacter on implants differed significantly between supra- and submucosal locations before multiple testing. The analyses demonstrated no significant differences between microbiomes on implants and teeth in supra- or submucosal and supra- or subgingival biofilms. Diseased peri-implant and periodontal tissues in the same subject share similiar bacterial genera and based on the analysis of taxa on a genus level biofilm compositions may not account for the potentially distinct pathologies at implants or teeth.
A novel supra-temporal approach to retrobulbar anaesthesia in dogs: Preliminary study in cadavers.
Chiavaccini, Ludovica; Micieli, Fabiana; Meomartino, Leonardo; Duffee, Lauren R; Vesce, Giancarlo
2017-05-01
A novel supra-temporal technique for retrobulbar anaesthesia in dogs is described and compared to the inferior temporal palpebral approach. Supra-temporal and inferior temporal palpebral retrobulbar injections were performed in 20 orbits of canine cadavers. Distribution of injected contrast medium within the intraconal space and around the optic nerve was analysed using computed tomography. There was adequate distribution of contrast medium within the intraconal space with both techniques. Concurrent intraconal and extraconal distribution was observed using the inferior temporal palpebral approach in 3/10 orbits and using the supra-temporal approach in 5/10 orbits. In 3/10 supra-temporal injections, the injected vehicle was distributed preferentially in the caudal aspect of the retrobulbar cone, closer to the orbital fissure. Accidental intraocular injection was never observed. The supra-temporal approach appears to be a valid alternative to the inferior temporal palpebral approach for retrobulbar anaesthesia in dogs, being less technically challenging. Further studies are required to confirm the clinical efficacy of this approach in dogs. Copyright © 2017 Elsevier Ltd. All rights reserved.
Balancing sub- and supra-salt strain in salt-influenced rifts: Implications for extension estimates
Coleman, Alexander J.; Jackson, Christopher A.-L.; Duffy, Oliver B.
2017-09-01
The structural style of salt-influenced rifts may differ from those formed in predominantly brittle crust. Salt can decouple sub- and supra-salt strain, causing sub-salt faults to be geometrically decoupled from, but kinematically coupled to and responsible for, supra-salt forced folding. Salt-influenced rifts thus contain more folds than their brittle counterparts, an observation often ignored in extension estimates. Fundamental to determining whether sub- and supra-salt structures are kinematically coherent, and the relative contributions of thin- (i.e. gravity-driven) and thick-skinned (i.e. whole-plate stretching) deformation to accommodating rift-related strain, is our ability to measure extension at both structural levels. We here use published physical models of salt-influenced extension to show that line-length estimates yield more accurate values of sub- and supra-salt extension compared to fault-heave, before applying these methods to seismic data from the Halten Terrace, offshore Norway. We show that, given the abundance of ductile deformation in salt-influenced rifts, significant amounts of extension may be ignored, leading to the erroneous interpretations of thin-skinned, gravity-gliding. If a system is kinematically coherent, supra-salt structures can help predict the occurrence and kinematics of sub-salt faults that may be poorly imaged and otherwise poorly constrained.
Supra-molecular Association and Polymorphic Behaviour In Systems Containing Bile Acid Salts
Directory of Open Access Journals (Sweden)
Camillo La Mesa
2007-08-01
Full Text Available A wide number of supra-molecular association modes are observed in mixtures containing water and bile salts, BS, (with, eventually, other components. Molecular or micellar solutions transform into hydrated solids, fibres, lyotropic liquid crystals and/or gels by raising the concentration, the temperature, adding electrolytes, surfactants, lipids and proteins. Amorphous or ordered phases may be formed accordingly. The forces responsible for this very rich polymorphism presumably arise from the unusual combination of electrostatic, hydrophobic and hydrogen-bond contributions to the system stability, with subsequent control of the supra-molecular organisation modes. The stabilising effect due to hydrogen bonds does not occur in almost all surfactants or lipids and is peculiar to bile acids and salts. Some supra-molecular organisation modes, supposed to be related to malfunctions and dis-metabolic diseases in vivo, are briefly reported and discussed.
Mendonça, J. Ricardo G.
We investigate the nonequilibrium roughening transition of a one-dimensional restricted solid-on-solid model by directly sampling the stationary probability density of a suitable order parameter as the surface adsorption rate varies. The shapes of the probability density histograms suggest a typical Ginzburg-Landau scenario for the phase transition of the model, and estimates of the "magnetic" exponent seem to confirm its mean-field critical behavior. We also found that the flipping times between the metastable phases of the model scale exponentially with the system size, signaling the breaking of ergodicity in the thermodynamic limit. Incidentally, we discovered that a closely related model not considered before also displays a phase transition with the same critical behavior as the original model. Our results support the usefulness of off-critical histogram techniques in the investigation of nonequilibrium phase transitions. We also briefly discuss in the appendix a good and simple pseudo-random number generator used in our simulations.
He, Ping
2012-01-01
The long-standing puzzle surrounding the statistical mechanics of self-gravitating systems has not yet been solved successfully. We formulate a systematic theoretical framework of entropy-based statistical mechanics for spherically symmetric collisionless self-gravitating systems. We use an approach that is very different from that of the conventional statistical mechanics of short-range interaction systems. We demonstrate that the equilibrium states of self-gravitating systems consist of both mechanical and statistical equilibria, with the former characterized by a series of velocity-moment equations and the latter by statistical equilibrium equations, which should be derived from the entropy principle. The velocity-moment equations of all orders are derived from the steady-state collisionless Boltzmann equation. We point out that the ergodicity is invalid for the whole self-gravitating system, but it can be re-established locally. Based on the local ergodicity, using Fermi-Dirac-like statistics, with the non-degenerate condition and the spatial independence of the local microstates, we rederive the Boltzmann-Gibbs entropy. This is consistent with the validity of the collisionless Boltzmann equation, and should be the correct entropy form for collisionless self-gravitating systems. Apart from the usual constraints of mass and energy conservation, we demonstrate that the series of moment or virialization equations must be included as additional constraints on the entropy functional when performing the variational calculus; this is an extension to the original prescription by White & Narayan. Any possible velocity distribution can be produced by the statistical-mechanical approach that we have developed with the extended Boltzmann-Gibbs/White-Narayan statistics. Finally, we discuss the questions of negative specific heat and ensemble inequivalence for self-gravitating systems.
Local depletion of glycogen with supra-maximal exercise in human skeletal muscle fibres
DEFF Research Database (Denmark)
Gejl, Kasper Degn; Ørtenblad, Niels; Andersson, Erik
2017-01-01
importance to muscle function. The present study was designed to investigate the depletion of these three sub-cellular glycogen compartments during repeated supra-maximal exercise in elite athletes. Ten elite cross-country skiers (age: 25 ± 4 yrs., VO2 max : 65 ± 4 ml kg(-1) min(-1) , mean ± SD) performed...... of spatially distinct glycogen compartments differs during supra-maximal exercise. Furthermore, the depletion changes with repeated exercise and is fibre type-dependent. This article is protected by copyright. All rights reserved....
Maximizing prosthetic valve size with the Top Hat supra-annular aortic valve
DEFF Research Database (Denmark)
Aagaard, Jan; Geha, Alexander S.
2007-01-01
BACKGROUND AND AIM OF THE STUDY: The CarboMedics Top Hat supra-annular aortic valve allows a one-size (and often two-size) increase over the standard intra-annular valve. This advantage should minimize the risk of patient-prosthesis mismatch, where the effective prosthetic valve orifice area...
Mach probe interpretation in the presence of supra-thermal electrons
Czech Academy of Sciences Publication Activity Database
Fuchs, Vladimír; Gunn, J. P.
2007-01-01
Roč. 14, č. 3 (2007), 032501-1 ISSN 1070-664X R&D Projects: GA ČR GA202/04/0360 Institutional research plan: CEZ:AV0Z20430508 Keywords : Mach probes * supra -thermal electrons * quasi-neutral PIC codes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.325, year: 2007
Thermal Structure of Supra-Arcade Plasma in Two Solar Flares
Reeves, Katharine K.; Savage, Sabrina; McKenzie, David E.; Weber, Mark A.
2012-01-01
In this work, we use Hinode/XRT and SDO/AIA data to determine the thermal structure of supra-arcade plasma in two solar flares. The first flare is a Ml.2 flare that occurred on November 5, 2010 on the east limb. This flare was one of a series of flares from AR 11121, published in Reeves & Golub (2011). The second flare is an XI.7 flare that occurred on January 27, 2012 on the west limb. This flare exhibits visible supra-arcade downflows (SADs), where the November 2010 flare does not. For these two flares we combine XRT and AlA data to calculate DEMs of each pixel in the supra-arcade plasma, giving insight into the temperature and density structures in the fan of plasma above the post-flare arcade. We find in each case that the supra-arcade plasma is around 10 MK, and there is a marked decrease in the emission measure in the SADs. We also compare the DEMs calculated with the combined AIA/XRT dataset to those calculated using AIA alone.
"Supra-Institutional Research": A Cost-Effective Contribution towards Enhancement
Yorke, Mantz
2010-01-01
Relatively inexpensive studies that go beyond the boundaries of individual institutions have considerable attraction, particularly at a time when resources are under significant constraint. These studies can be viewed as existing under the rather larger umbrella of "supra-institutional research". Three examples illustrate the argument…
Final results of the supra project : Improved Simulation of Upset Recovery
Fucke, L.; Groen, E.; Goman, M.; Abramov, N.; Wentink, M.; Nooij, S.; Zaichik, L.E.; Khrabrov, A.
2012-01-01
The objective of the European research project SUPRA (Simulation of Upset Recovery in Aviation) is to develop technologies that eventually contribute to a reduction of risk of Loss of control - in flight (LOC-I) accidents, today's major cause of fatal accidents in commercial aviation. To this end
Li, Jie; Liu, Kaerdun; Han, Yuchun; Tang, Ben Zhong; Huang, Jianbin; Yan, Yun
2016-10-04
Propeller-shaped molecules have been recognized to display fantastic AIE (aggregation induced emission), but they can hardly self-assemble into nanostructures. Herein, we for the first time report that ionic complexation between a water-soluble tetrapheneyl derivative and an enzyme substrate in aqueous media produces a propeller-shaped supra-amphiphile that self-assembles into enzyme responsive fluorescent vesicles. The supra-amphiphile was fabricated upon complexation between a water-soluble propeller-shaped AIE luminogen TPE-BPA and myristoylcholine chloride (MChCl) in aqueous media. MChCl filled in the intramolecular voids of propeller-shaped TPE-BPA upon supra-amphiphile formation, which endows the supra-amphiphile superior self-assembling ability to the component molecules thus leading to the formation of fluorescent vesicles. Because MChCl is the substrate of cholinesterases, the vesicles dissemble in the presence of cholinesterases, and the fluorescent intensity can be correlated to the level of enzymes. The resulting fluorescent vesicles may be used to recognize the site of Alzheimer's disease, to encapsulate the enzyme inhibitor, and to release the inhibitor at the disease site.
Real chimney technique for total debranching of supra-aortic trunks.
Kato, Masaaki; Kagaya, Hideo; Kubo, Yoji; Banno, Hiroshi; Ohkubo, Nobukazu
2015-02-01
Side-clamping of the ascending aorta is an indispensable technique for proximal anastomosis in total debranching of supra-aortic trunks and in endovascular aneurysm repair for arch aneurysm. However, this procedure may lead to the dislodging of multiple plaques and to clamp injury of the ascending aorta. We developed a clampless technique to achieve proximal anastomosis between the ascending aorta and an artificial graft used for total debranching of supra-aortic trunks. We applied this method in six patients with arch aneurysm and a plaque-rich ascending aorta and were able to achieve total debranching of the supra-aortic trunks in all of the patients without side-clamping the ascending aorta and no procedurally related complications. This clampless anastomosis technique ("real chimney technique") in the ascending aorta is a valuable option for total debranching of supra-aortic trunks in the hybrid repair of arch aneurysms. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
Water-Triggered Luminescent "Nano-bombs" Based on Supra-(Carbon Nanodots)
Lou, Q.; Qu, S.; Jing, P.; Ji, W.; Li, D.; Cao, J.; Zhang, H.; Liu, L.; Zhao, J.; Shen, D.
2015-01-01
Novel luminescent "nano-bombs" based on a self-assembled system of carbon-nanodots, termed supra-CDs, are developed. The luminescence of these luminescent "nano-bombs" depends strongly on water contact; they show weak emission in toluene and decompose in contact with water, resulting in strong
Horobin, Jarod T; Sabapathy, Surendran; Simmonds, Michael J
2017-11-01
The supra-physiological shear stress that blood is exposed to while traversing mechanical circulatory assist devices affects the physical properties of red blood cells (RBCs), impairs RBC deformability, and may induce hemolysis. Previous studies exploring RBC damage following exposure to supra-physiological shear stress have employed durations exceeding clinical instrumentation, thus we explored changes in RBC deformability following exposure to shear stress below the reported "hemolytic threshold" using shear exposure durations per minute (i.e., duty-cycles) reflective of that employed by circulatory assist devices. Blood collected from 20 male donors, aged 18-38 years, was suspended in a viscous medium and exposed to an intermittent shear stress protocol of 1 s at 100 Pa, every 60 s for 60 duty-cycles. During the remaining 59 s/min, the cells were left at stasis until the subsequent duty-cycle commenced. At discrete time points (15/30/45/60 duty-cycles), an ektacytometer measured RBC deformability immediately after shear exposure at 100 Pa. Plasma-free hemoglobin, a measurement of hemolysis, was quantified via spectrophotometry. Supra-physiological shear stress impaired RBC properties, as indicated by: (1) decreased maximal elongation of RBCs at infinite shear stress following 15 duty-cycles (P supra-physiological shear stress protocol (100 Pa) following exposure to 1 duty-cycle (F (1.891, 32.15) = 12.21, P = 0.0001); and (3) increased plasma-free hemoglobin following 60 duty-cycles (P supra-physiological shear stress, impairs RBC deformability, with the extent of impairment exacerbated with each duty-cycle, and ultimately precipitates hemolysis. © 2017 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Jirapinyo, Pichamol; Kröner, Paul T; Thompson, Christopher C
2018-04-01
BACKGROUND AND STUDY AIMS : Transoral outlet reduction (TORe), performed using a traditional interrupted or a recently described purse-string suture pattern, is effective at inducing short- and mid-term weight loss in patients with weight regain after Roux-en-Y gastric bypass (RYGB). We aimed to determine the technical feasibility and safety of purse-string TORe and to assess its impact on weight and metabolic profiles. RYGB patients undergoing purse-string TORe were included. The gastrojejunal anastomosis (GJA) was ablated using argon plasma coagulation or dissected using endoscopic submucosal dissection. A suture was used to place stitches around the GJA in a continuous ring fashion. The suture was cinched over a balloon (8 - 12 mm). The primary outcome was technical feasibility. Secondary outcomes were the percentage of total body weight lost (%TWL), adverse events, impact on comorbidities, and predictors of weight loss. 252 RYGB patients underwent 260 purse-string TORes. They had regained 52.6 ± 46.4 % of lost weight and weighed 107.6 ± 24.6 kg. The technical success rate was 100 %. At 6 and 12 months, %TWL was 9.6 ± 6.3 and 8.4 ± 8.2. Two serious adverse events (0.8 %) occurred: gastrointestinal bleeding and GJA stenosis. At 12 months, blood pressure, hemoglobin A 1c , and ALT had improved. Prior weight regain was associated with %TWL at 12 months ( β = 0.07, P = 0.007) after controlling for BMI, pouch size, and number of purse-string rings. Purse-string TORe to treat weight regain after RYGB is technically feasible and safe. Additionally, it is associated with improvement in weight and comorbidity profiles up to 12 months post-procedure. © Georg Thieme Verlag KG Stuttgart · New York.
DEFF Research Database (Denmark)
Beier, Søren Prip; Jonsson, Gunnar Eigil
2007-01-01
A vibrating membrane bioreactor, in which the fouling problems are reduced by vibrating a hollow fiber membrane module, has been tested in constant flux microfiltration above (supra-critical) and below (sub-critical) an experimentally determined critical flux. Suspensions of bakers yeast cells were...... is continually washed out during supra-critical flux operation whereas the washing out at sub-critical flux operation is not observed. This might be due to locally different hydrodynamic conditions at the membrane surface and pore entrances at supra- and sub-critical flux respectively....
The 1987-1988 progress report of the CEA-Euratom Association Research Laboratory
International Nuclear Information System (INIS)
1989-05-01
The progress report of the CEA-Euratom Association Research Group, concerning 1987 and 1988 activities, is presented. The report involves the work carried out for assembling the Tore Supra system. The different components and the operating modes are described. The report includes: the Tore Supra construction and running, theoretical work, numerical calculations and results, the tritium technology, safety studies, supraconductors and bobbins. The Tore Supra contributions to the JET program are given [fr
International Nuclear Information System (INIS)
Toi, K; Ohdachi, S; Watanabe, F; Narihara, K; Morisaki, T; Sakakibara, S; Morita, S; Goto, M; Ida, K; Masuzaki, S; Miyazawa, K; Tanaka, K; Tokuzawa, T; Watanabe, K W; Yoshinuma, M
2006-01-01
On the Large Helical Device (LHD), low to high confinement (L-H) transition and edge transport barrier (ETB) formation were observed in the low beta regime ((β dia ) dia ): volume-averaged beta derived from diamagnetic measurement) as well as in relatively high beta regime (>1.5%). In most of ETB plasmas electron density preferentially increases in the edge region without a substantial rise of the edge electron temperature. The ETB zone develops inside the ergodic field layer calculated in the vacuum field. The ETB formation strongly destabilizes edge coherent modes such as m/n = 2/3 or 1/2 (m, n: poloidal and toroidal mode numbers), because the plasma edge region is in the magnetic hill. The ETB is partially destroyed by the combination of these edge MHD modes and ELM-like activities. For a particular experimental condition, the forced generation of a sizable m/n = 1/1 magnetic island near the edge by application of external field perturbations facilitates the L-H transition at a lower electron density and suppresses edge MHD modes and ELM-like activities to lower levels
Chana-Rodríguez, Francisco; Cuervas-Mons, Manuel; Rojo-Manaute, José; Mora, Félix; Arnal, Juan; Vaquero-Martín, Javier
2017-11-01
Pelvic fracture in trauma patients can lead to hemodynamic instability. External fixation is a treatment capable of stabilizing these injuries in the context of damage control surgery. Supra-acetabular pin offers the greater biomechanical stability but requires the use of intraoperative fluoroscopy. The aim of this study was to analyze our results for an ultrasound-guided supra-acetabular pinning. Cross-sectional study with cadaveric specimens. Ultrasound-guided pin placement assessed by fluoroscopy and dissection. Fourteen ultrasound-guided supra-acetabular pins were placed in seven cadaveric specimens. Excellent placement in all cases, evaluated with radiological control. Good qualitative bone fixation after dissection. One femoral cutaneous nerve was not found during anatomic dissection and was assumed injured. Ultrasound-guided supra-acetabular pin placement is a feasible and effective technique. Our study indicates that pin placement without intraoperative fluoroscopy is feasible without compromising the reliability of its placement. © 2017 Elsevier Ltd. All rights reserved.
Ullery, Brant W; Suh, Ga-Young; Hirotsu, Kelsey; Zhu, David; Lee, Jason T; Dake, Michael D; Fleischmann, Dominik; Cheng, Christopher P
2018-04-01
To utilize 3-D modeling techniques to better characterize geometric deformations of the supra-aortic arch branch vessels and descending thoracic aorta after thoracic endovascular aortic repair. Eighteen patients underwent endovascular repair of either type B aortic dissection (n = 10) or thoracic aortic aneurysm (n = 8). Computed tomography angiography was obtained pre- and postprocedure, and 3-D geometric models of the aorta and supra-aortic branch vessels were constructed. Branch angle of the supra-aortic branch vessels and curvature metrics of the ascending aorta, aortic arch, and stented thoracic aortic lumen were calculated both at pre- and postintervention. The left common carotid artery branch angle was lower than the left subclavian artery angles preintervention ( P Supra-aortic branch vessel angulation remains relatively static when proximal landing zones are distal to the left common carotid artery.
Digital Repository Service at National Institute of Oceanography (India)
Gupta, S.M.; Fernandes, A.A.
A Q-mode factor analysis of the % data of 25 broadly defined supra-generic radiolarian groups in 42 deep-sea surface sediments produced four statistically significant and geographically distinct faunal assemblages related to (1) southwest cooler (27...
U.S. EPA, Pesticide Product Label, BIO-GUARD OBQ-SUPRA 100 ORANGE BOUQUET, 09/03/1975
2011-04-14
... I I j i ' i) :1 I '~F t r: I t \\ N rlll'( \\' I}f' ll," cI t h I () II q I d II t () 111,j I Ie f I () ( ) I ,I,,:d,lflil "qIJlp'l\\i':'~ • OBa-SUPRA 100 ~~~ ... DBQ-SUPRA 100 tJ~~ -. / I ...
Rapid growth of seed black holes in the early universe by supra-exponential accretion.
Alexander, Tal; Natarajan, Priyamvada
2014-09-12
Mass accretion by black holes (BHs) is typically capped at the Eddington rate, when radiation's push balances gravity's pull. However, even exponential growth at the Eddington-limited e-folding time t(E) ~ few × 0.01 billion years is too slow to grow stellar-mass BH seeds into the supermassive luminous quasars that are observed when the universe is 1 billion years old. We propose a dynamical mechanism that can trigger supra-exponential accretion in the early universe, when a BH seed is bound in a star cluster fed by the ubiquitous dense cold gas flows. The high gas opacity traps the accretion radiation, while the low-mass BH's random motions suppress the formation of a slowly draining accretion disk. Supra-exponential growth can thus explain the puzzling emergence of supermassive BHs that power luminous quasars so soon after the Big Bang. Copyright © 2014, American Association for the Advancement of Science.
Pan, Xicai; Yu, Qihao; You, Yanhui; Chun, Kwok Pan; Shi, Xiaogang; Li, Yanping
2017-12-01
The seasonal hydrological mechanisms of two thermokarst lakes on the northeastern Qinghai-Tibet Plateau (QTP) were characterized by three-year intensive field observations and a water balance model. In three ice-free seasons, the supra-permafrost discharge contributed a mean ratio of over 170% of the precipitation. In the ice-cover seasons, the supra-permafrost discharge contribution varied between -20% and 22% of the water storage change. Results show that a large portion of the lake water storage change is because of the supra-permafrost discharge resulting from precipitation. Furthermore, a precipitation-subsurface runoff function is preliminarily identified in which the supra-permafrost discharge nonlinearly increased with more precipitation. Our results show that the recent lake expansion is linked with increasing supra-permafrost discharge dominated by precipitation. This study also suggests that we need to pay attention to the nonlinear increase of precipitation-controlled supra-permafrost discharge on the large lake expansion at the catchment scale in the QTP region, instead of only looking at the inputs (e.g., precipitation and river discharge) as shown in the previous studies.
Eyüpoglu, Ilker Y; Hore, Nirjhar; Merkel, Andreas; Buslei, Rolf; Buchfelder, Michael; Savaskan, Nicolai
2016-05-03
Safe and complete resection represents the first step in the treatment of glioblastomas and is mandatory in increasing the effectiveness of adjuvant therapy to prolong overall survival. With gross total resection currently limited in extent to MRI contrast enhancing areas, the extent to which supra-complete resection beyond obvious contrast enhancement could have impact on overall survival remains unclear. DiVA (dual intraoperative visualization approach) redefines gross total resection as currently accepted by enabling for the first time supra-complete surgery without compromising patient safety. This approach exploits the advantages of two already accepted surgical techniques combining intraoperative MRI with integrated functional neuronavigation and 5-ALA by integrating them into a single surgical approach. We investigated whether this technique has impact on overall outcome in GBM patients. 105 patients with GBM were included. We achieved complete resection with intraoperative MRI alone according to current best-practice in glioma surgery in 75 patients. 30 patients received surgery with supra-complete resection. The control arm showed a median life expectancy of 14 months, reflecting current standards-of-care and outcome. In contrast, patients receiving supra-complete surgery displayed significant increase in median survival time to 18.5 months with overall survival time correlating directly with extent of supra-complete resection. This extension of overall survival did not come at the cost of neurological deterioration. We show for the first time that supra-complete glioma surgery leads to significant prolongation of overall survival time in GBM patients.
Can diffusion tensor imaging predict the functional outcome of supra-tentorial stroke?
International Nuclear Information System (INIS)
Maeda, Takahiro; Ishizaki, Ken-ichi; Yura, Shigeki
2005-01-01
We used diffusion tensor imaging (DTI) to assess wallerian degeneration of the pyramidal tract after the onset of supra-tentorial stroke, and correlation of the extent of Wallerian degeneration with the motor function at 3 months after stroke. Twenty eight patients with supra-tentorial acute stroke were examined, two weeks and one month after stroke by DTI. We measured fractional anisotropy (FA) of affected side/unaffected side (FA ratio) in the cerebral peduncle. We used modified Rankin Scale (mRS) for assessment of motor function at 3 months after stroke. FA ratio was significantly reduced at 2 weeks after stroke (0.833±0.146) compared to on admission (0.979±0.0797). But no significant change of FA ratio was seen between two weeks and one month after stroke in 7 cases examined (0.758±0.183 vs. 0.754±0.183). In all patients in whom the FA ratio was under 0.8 at 2 weeks after stroke, motor function showed poor recovery (mRS 4 and 5) at 3 months after stroke. When FA ratio was over 0.8 at 2 weeks after stroke, motor function at 3 months after stroke showed good recovery (mRS 0 to 3) expect for three elderly patients. With the use of DTI, Wallerian degeneration could be detected in the corticospinal tracts at midbrain level during the early phase of supra-tentorial stroke. We conclude that DTI may be useful for early prediction of motor function prognosis in patients with supra-tentorial acute stroke. (author)
Mohan, Jagdish C; Mohan, Vishwas; Shukla, Madhu; Sethi, Arvind
Doppler-derived trans-prosthetic gradients are higher and the estimated effective valve area is smaller than the catheter-derived and directly measured hemodynamic values, mostly due to pressure recovery phenomenon. Pressure recovery to a varying extent is common to all prosthetic heart valves including bioprostheses. Pressure recovery-related differences are usually small except in patients with bileaflet metallic prosthesis, wherein high-pressure local jets across central orifice have been documented since long back and also in patients with narrow aortic root. We describe two patients with normally functioning stented aortic bioprostheses with supra-annular design (EPIC SUPRA and PERIMOUNT MAGNA), wherein very high trans-prosthetic gradients and critically reduced estimated effective valve orifice areas in presence of normal aortic size were consistently recorded over long periods of follow-up. The valve leaflets, however had normal excursion, were thin, opened with a triangular or oblong shape and had expected geometric valve area (1.7 and 1.6cm 2 respectively) measured by 3D trans-oesophageal echocardiographic planimetry. Pressure recovery upstream the valves accounted for 20% and 12% of total pressure gradients respectively. Dominant site for pressure drop was intra-valvular (75-85%). Such a phenomenon has not been reported in vivo for these two valve designs. Copyright © 2016. Published by Elsevier B.V.
Observations of Supra-arcade Fans: Instabilities at the Head of Reconnection Jets
Innes, D. E.; Guo, L.-J.; Bhattacharjee, A.; Huang, Y.-M.; Schmit, D.
2014-11-01
Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.
Observations of supra-arcade fans: instabilities at the head of reconnection jets
International Nuclear Information System (INIS)
Innes, D. E.; Guo, L.-J.; Schmit, D.; Bhattacharjee, A.; Huang, Y.-M.
2014-01-01
Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets.
Open Treatment of Blunt Injuries of Supra-Aortic Branches: Case Series.
Sladojevic, Milos; Markovic, Miroslav; Ilic, Nikola; Pejkic, Sinisa; Banzic, Igor; Djoric, Predrag; Koncar, Igor; Tomic, Ivan; Davidovic, Lazar
2016-02-01
Blunt injuries of the supra-aortic branches are rare entity, and majority of patients die before arrival at the hospital. Those who arrive alive require complex and fast procedure that requires sternotomy. We report 3 successfully managed cases. We report 3 patients with injury of supra-aortic branches. One was treated urgently due to longitudinal rupture on the posterior wall of innominate artery after car accident, and another 2 had chronic false aneurysm located at the very orifice of the right subclavian and left common carotid artery. In first and second patient bypass grafting with a hand-made, Y-shaped, 8-mm Dacron graft from the ascending aorta to the right common carotid and proximal right subclavian artery were performed, whereas in last 1 bypass grafting from the ascending aorta to the cervical part of the left common carotid artery was performed. In our facility, there were no possibilities for any endovascular treatment. When endovascular technology is not available, open surgical repair of blunt injuries of supra-aortic vessels can be performed without complications. No matter to that, endovascular and hybrid procedures should be considered whenever possible. Copyright © 2016 Elsevier Inc. All rights reserved.
Boutet, Claire; Abdirahman Mohamed Moussa, Syad; Celle, Sébastien; Laurent, Bernard; Barthélémy, Jean-Claude; Barral, Fabrice-Guy; Roche, Frédéric
2016-01-01
Small upper airway measurements areas and high body mass index are recognized risk factors for obstructive sleep apnea syndrome (OSAS) in non-elderly populations; however, there is limited information regarding elderly patients. We evaluated whether upper airway volume is associated with OSAS and OSAS treated with continuous positive airway pressure (CPAP) treatment and whether BMI is correlated with upper airway volume and measurements in elderly subjects. In 60 volunteers aged 75.58±0.9 years: 20 OSAS, 20 OSAS chronically treated with CPAP, and 20 controls, semi-automatic segmentation, retropalatal distance and transverse diameter of the supra-epiglottic upper airway were evaluated using 3DT1-weighted magnetic resonance imaging. Anteroposterior to transverse diameter ratio was defined as retropalatar diameter/transverse diameter. There were no significant differences in supra-epiglottic upper airway volume between OSAS, CPAP treated patients, and controls. There were significant differences in retropalatal distance and anteroposterior to transverse diameter ratio between OSAS, CPAP treated patients, and controls (P = 0.008 and Psupra-epiglottic upper airway volume. In elderly subjects, OSAS and body mass index are not associated with changes in supra-epiglottic upper airway volume but are associated with modification of pharynx shape.
Design of Industrial and Supra-Firm Architectures: Growth and Sustainability
Directory of Open Access Journals (Sweden)
John A. Mathews
2012-08-01
Full Text Available The scope of organization design has expanded steadily from work-flow issues and job specifications to firm-level considerations and now to supra-firm industrial structures, where such issues as modularity and clustering loom large. Economic analysis has made little headway in analyzing how increasing returns may be generated through supra-firm structures such as networks and clusters, nor in the question of how their industrial architecture (modular vs. integral, open vs. closed affects economic performance. The focus here is on the supra-firm industrial architectures that have arisen, either spontaneously through the evolution of capitalism or through purposeful design, involving both state and private actors. Striking cases such as the Chinese automotive industry, which started with the production of conventional automobiles and motorcycles, and now encompasses both two-wheeled and four-wheeled electric vehicles, provide testimony to the power of some industrial configurations to outperform others. My analyses and arguments are placed in the global context of the urgent need to find ways to accelerate the uptake of green technologies (such as electric vehicles in order to reduce emissions of greenhouse gases and at the same time promote the industrialization of countries still at lower levels of income and wealth.
Directory of Open Access Journals (Sweden)
2009-09-01
Full Text Available Tore T. Petersen. Richard Nixon, Great Britain and the Anglo-American Alignment in the Persian Gulf and Arabian Peninsula: Making Allies out of Clients. Sussex Academic Press, 2009. 172pp. 978-1-84519-277-8.Since the events of 9-11 there has been a sizeable quantity of books published on American foreign policy in broad terms, as well as more focused studies on contemporary developments in southwest Asia, more commonly referred to as the Middle East. Many of these volumes are highly politic...
Paunov, Vesselin N; Al-Shehri, Hamza; Horozov, Tommy S
2016-09-29
We developed and tested a theoretical model for the attachment of fluid-infused porous supra-particles to a fluid-liquid interface. We considered the wetting behaviour of agglomerated clusters of particles, typical of powdered materials dispersed in a liquid, as well as of the adsorption of liquid-infused colloidosomes at the liquid-fluid interface. The free energy of attachment of a composite spherical porous supra-particle made from much smaller aggregated spherical particles to the oil-water interface was calculated. Two cases were considered: (i) a water-filled porous supra-particle adsorbed at the oil-water interface from the water phase, and, (ii) an oil-filled porous supra-particle adsorbed at the oil-water interface from the oil-phase. We derived equations relating the three-phase contact angle of the smaller "building block" particles and the contact angle of the liquid-infused porous supra-particles. The theory predicts that the porous supra-particle contact angle attached at the liquid interface strongly depends on the type of fluid infused in the particle pores and the fluid phase from which it approaches the liquid interface. We tested the theory by using millimetre-sized porous supra-particles fabricated by evaporation of droplets of polystyrene latex suspension on a pre-heated super-hydrophobic surface, followed by thermal annealing at the glass transition temperature. Such porous particles were initially infused with water or oil and approached to the oil-water interface from the infusing phase. The experiment showed that when attaching at the hexadecane-water interface, the porous supra-particles behaved as hydrophilic when they were pre-filled with water and hydrophobic when they were pre-filled with hexadecane. The results agree with the theoretically predicted contact angles for the porous composite supra-particles based on the values of the contact angles of their building block latex particles measured with the Gel Trapping Technique. The
Ban, David; Sabo, T Michael; Griesinger, Christian; Lee, Donghan
2013-09-26
Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool that has enabled experimentalists to characterize molecular dynamics and kinetics spanning a wide range of time-scales from picoseconds to days. This review focuses on addressing the previously inaccessible supra-tc window (defined as τ(c) supra-τ(c) supra-τ(c) window. In the second section, the current state of the art for RD is analyzed, as well as the considerable progress toward pushing the sensitivity of RD further into the supra-τ(c) scale by up to a factor of two (motion up to 25 μs). From the data obtained with these techniques and methodology, the importance of the supra-τ(c) scale for protein function and molecular recognition is becoming increasingly clearer as the connection between motion on the supra-τ(c) scale and protein functionality from the experimental side is further strengthened with results from molecular dynamics simulations.
Cerebellar Roles in Self-Timing for Sub- and Supra-Second Intervals.
Ohmae, Shogo; Kunimatsu, Jun; Tanaka, Masaki
2017-03-29
Previous studies suggest that the cerebellum and basal ganglia are involved in sub-second and supra-second timing, respectively. To test this hypothesis at the cellular level, we examined the activity of single neurons in the cerebellar dentate nucleus in monkeys performing the oculomotor version of the self-timing task. Animals were trained to report the passage of time of 400, 600, 1200, or 2400 ms following a visual cue by making self-initiated memory-guided saccades. We found a sizeable preparatory neuronal activity before self-timed saccades across delay intervals, while the time course of activity correlated with the trial-by-trial variation of saccade latency in different ways depending on the length of the delay intervals. For the shorter delay intervals, the ramping up of neuronal firing rate started just after the visual cue and the rate of rise of neuronal activity correlated with saccade timing. In contrast, for the longest delay (2400 ms), the preparatory activity started late during the delay period, and its onset time correlated with self-timed saccade latency. Because electrical microstimulation applied to the recording sites during saccade preparation advanced self-timed but not reactive saccades, regardless of their directions, the signals in the cerebellum may have a causal role in self-timing. We suggest that the cerebellum may regulate timing in both sub-second and supra-second ranges, although its relative contribution might be greater for sub-second than for supra-second time intervals. SIGNIFICANCE STATEMENT How we decide the timing of self-initiated movement is a fundamental question. According to the prevailing hypothesis, the cerebellum plays a role in monitoring sub-second timing, whereas the basal ganglia are important for supra-second timing. To verify this, we explored neuronal signals in the monkey cerebellum while animals reported the passage of time in the range 400-2400 ms by making eye movements. Contrary to our expectations, we
Activation/Inhibition of mast cells by supra-optimal antigen concentrations.
Huber, Michael
2013-01-22
Mast cells (MCs) are tissue resident cells of hemopoietic origin and are critically involved in allergic diseases. MCs bind IgE by means of their high-affinity receptor for IgE (FcεRI). The FcεRI belongs to a family of multi-chain immune recognition receptors and is activated by cross-linking in response to multivalent antigens (Ags)/allergens. Activation of the FcεRI results in immediate release of preformed granular substances (e.g. histamine, heparin, and proteases), generation of arachidonic acid metabolites, and production of pro-inflammatory cytokines. The FcεRI shows a remarkable, bell-shaped dose-response behavior with weak induction of effector responses at both low and high (so-called supra-optimal) Ag concentrations. This is significantly different from many other receptors, which reach a plateau phase in response to high ligand concentrations. To explain this unusual dose-response behavior of the FcεRI, scientists in the past have drawn parallels to so-called precipitin curves resulting from titration of Ag against a fixed concentration of antibody (Ab) in solution (a.k.a. Heidelberger curves). Thus, for high, supra-optimal Ag concentrations one could assume that every IgE-bound FcεRI formed a monovalent complex with "its own Ag", thus resulting in marginal induction of effector functions due to absence of receptor cross-linking. However, this was never proven to be the case. More recently, careful studies of FcεRI activation and signaling events in MCs in response to supra-optimal Ag concentrations have suggested a molecular explanation for the descending part of this bell-shaped curve. It is obvious now that extensive FcεRI/IgE/Ag clusters are formed and inhibitory molecules and signalosomes are engaged in response to supra-optimal cross-linking (amongst them the Src family kinase Lyn and the inositol-5'-phosphatase SHIP1) and they actively down-regulate MC effector responses. Thus, the analysis of MC signaling triggered by supra
Supra choroidal buckling in managing myopic vitreoretinal interface disorders: 1-year data.
El Rayes, Ehab N
2014-01-01
To evaluate the efficacy of supra choroidal buckling procedure using a supra choroidal catheter, as a new approach in treating myopic vitreomacular interface disorders specially in difficult cases of myopic traction maculopathy with or without macular hole retinal detachment in posterior staphyloma depending on the concept of indenting the choroid only, from a 1-year data study. A newly developed supra choroidal catheter was used to deliver stabilized, cross-linked, long-acting hyaluronic acid as a filler in the supra choroidal space in the area of the staphyloma forming a choroidal indenting effect. Before the injection, pars plana vitrectomy was performed without internal limiting membrane peeling to avoid the risk of break of the roof of foveal detachment in case of foveoschisis. This indentation was used to treat 11 patients with myopic foveoschisis and 12 patients with myopic macular hole retinal detachment, 5 of whom had failed primary repair by vitrectomy before inclusion in this trial. Clinical and optical coherence tomographic evaluations of these patients were performed over 1-year follow-up. Retinal layer restoration was achieved in all 11 eyes with myopic foveoschisis. This was gradual over a period of 2 to 6 weeks postoperatively. No recurrence over the 12-month follow-up was observed. Visual acuity improved by 1 line or more in 9 eyes (81.8%). Of the 12 eyes, 10 with macular hole detachment (83%) showed closure of the holes in association with the resolution of the detachment; 2 eyes showed resolution of the detachment and flatting of the edge of the holes but with incomplete closure on optical coherence tomography. Eight eyes (66.6%) showed improvement in visual acuity by 1 or more lines with no recurrence of retinal detachment over the 12-month follow-up period. The indentation effect was sufficient over the 12-month follow-up period. The indentation effect achieved by supra choroidal approach can be used as a method of managing myopic foveoschisis
Directory of Open Access Journals (Sweden)
Kashapov, Mergalуаs M.
2017-03-01
Full Text Available This article describes the functions of metacognition and the role of these functions in professional pedagogical thinking (PPT: the discovery of the emergence of a problemacy, the organization of cognition processes, and the management of the comprehension and resolution of the problem situation. Thinking is related to the metacognitive activity of a subject. Components and strategies of metacognition are included in the PPT process and define (by means of conscious or unconscious regulation the efficiency of discovering and solving problems in an interpersonal interaction situation that must be comprehended and transformed. One of the conditions providing for realization of the supra-situational thinking of professionals is a high level of metacognitive activity, although the level of the pronouncedness of metacognitive activity does not depend on the subject’s possessing basic professional education. We have created and tested new psychodiagnostic techniques aimed at defining the level of forecasting in problem (conflict situations and at evaluating metacognitive knowledge and activity. The sample group included about 800 people (university lecturers, school teachers, and teachers who train college students. It was proved that the metacognitive focus of forecasting stimulates the formation and development of various forecasting types: proactive, retroactive, and interactive. Forecasting is viewed as a metacognitive component of supra-situational thinking and a component of the cognitive side of communication. Situational and supra- situational types of pedagogical thinking are shown to have different properties and different orientations toward forecasting activity; these properties and orientations determine the differentiation and hierarchization of these types of thinking. It was discovered that the metacognitive properties of supra-situational thinking are achieved through a high degree of integration of all basic forecasting qualities
Sequencing at the syllabic and supra-syllabic levels during speech perception: an fMRI study.
Deschamps, Isabelle; Tremblay, Pascale
2014-01-01
The processing of fluent speech involves complex computational steps that begin with the segmentation of the continuous flow of speech sounds into syllables and words. One question that naturally arises pertains to the type of syllabic information that speech processes act upon. Here, we used functional magnetic resonance imaging to profile regions, using a combination of whole-brain and exploratory anatomical region-of-interest (ROI) approaches, that were sensitive to syllabic information during speech perception by parametrically manipulating syllabic complexity along two dimensions: (1) individual syllable complexity, and (2) sequence complexity (supra-syllabic). We manipulated the complexity of the syllable by using the simplest syllable template-a consonant and vowel (CV)-and inserting an additional consonant to create a complex onset (CCV). The supra-syllabic complexity was manipulated by creating sequences composed of the same syllable repeated six times (e.g., /pa-pa-pa-pa-pa-pa/) and sequences of three different syllables each repeated twice (e.g., /pa-ta-ka-pa-ta-ka/). This parametrical design allowed us to identify brain regions sensitive to (1) syllabic complexity independent of supra-syllabic complexity, (2) supra-syllabic complexity independent of syllabic complexity and, (3) both syllabic and supra-syllabic complexity. High-resolution scans were acquired for 15 healthy adults. An exploratory anatomical ROI analysis of the supratemporal plane (STP) identified bilateral regions within the anterior two-third of the planum temporale, the primary auditory cortices as well as the anterior two-third of the superior temporal gyrus that showed different patterns of sensitivity to syllabic and supra-syllabic information. These findings demonstrate that during passive listening of syllable sequences, sublexical information is processed automatically, and sensitivity to syllabic and supra-syllabic information is localized almost exclusively within the STP.
Sequencing at the syllabic and supra-syllabic levels during speech perception: an fMRI study
Directory of Open Access Journals (Sweden)
Isabelle eDeschamps
2014-07-01
Full Text Available The processing of fluent speech involves complex computational steps that begin with the segmentation of the continuous flow of speech sounds into syllables and words. One question that naturally arises pertains to the type of syllabic information that speech processes act upon. Here, we used functional magnetic resonance imaging to profile regions, using a combination of whole-brain and exploratory anatomical region-of-interest (ROI approaches, that were sensitive to syllabic information during speech perception by parametrically manipulating syllabic complexity along two dimensions: (1 individual syllable complexity, and (2 sequence complexity (supra-syllabic. We manipulated the complexity of the syllable by using the simplest syllable template—a consonant and vowel (CV-and inserting an additional consonant to create a complex onset (CCV. The supra-syllabic complexity was manipulated by creating sequences composed of the same syllable repeated 6 times (e.g. /pa-pa-pa-pa-pa-pa/ and sequences of 3 different syllables each repeated twice (e.g. /pa-ta-ka-pa-ta-ka/. This parametrical design allowed us to identify brain regions sensitive to (1 syllabic complexity independent of supra-syllabic complexity, (2 supra-syllabic complexity independent of syllabic complexity and, (3 both syllabic and supra-syllabic complexity. High-resolution scans were acquired for 15 healthy adults. An exploratory anatomical ROI analysis of the supratemporal plane (STP identified bilateral regions within the anterior two-third of the planum temporale, the primary auditory cortices as well as the anterior two-third of the superior temporal gyrus that showed different patterns of sensitivity to syllabic and supra-syllabic information. These findings demonstrate that during passive listening of syllable sequences, sublexical information is processed automatically, and sensitivity to syllabic and supra-syllabic information is localized almost exclusively within the STP.
International Nuclear Information System (INIS)
Wang, Erhui; Morita, Shigeru; Goto, Motoshi; Murakami, Izumi; Oishi, Tetsutarou; Dong, Chunfeng
2013-01-01
Two-dimensional distribution of impurity lines emitted from ergodic layer with stochastic magnetic field lines in Large Helical Device (LHD) has been observed using a space-resolved extreme ultraviolet (EUV) spectrometer. The two-dimensional electron temperature distribution in the ergodic layer is successfully measured using the line intensity ratio of Li-like NeVIII 2s-3p ( 2 S 1/2 - 2 P 3/2 : 88.09 Å, 2 S 1/2 - 2 P 1/2 : 88.13 Å) to 2p-3s ( 2 P 1/2 - 2 S 1/2 : 102.91 Å, 2 P 3/2 - 2 S 1/2 : 103.09 Å) transitions emitted from radial location near Last Closed Flux Surface (LCFS). The intensity ratio analyzed with ADAS code shows no dependence on the electron density below 10 14 cm -3 . The result indicates a little higher temperature, i.e., 220 eV, in the poloidal location at high-field side near helical coils called O-point compared to the temperature near X-point, i.e., 170 eV. The electron temperature profile is also measured at the edge boundary of ergodic layer using the line intensity ratio of Li-like CIV 2p-3d ( 2 P 1/2 - 2 D 3/2 : 384.03 Å, 2 P 3/2 - 2 D 5/2 : 384.18 Å) to 2p-3s ( 2 P 1/2 - 2 S 1/2 : 419.53 Å, 2 P 3/2 - 2 S 1/2 : 419.71 Å) transitions. The intensity ratios analyzed with CHIANTI, ADAS and T.Kawachi codes show a slightly higher temperature near O-point, i.e., 25 eV for CHIANTI, 21 eV for ADAS and 11 eV for T.Kawachi's codes, compared to the temperature at X-point, i.e., 15 - 21 eV for CHIANTI, 9 - 15 eV for ADAS and 6 - 9 eV for T.Kawachi codes. It suggests that the transport coefficient in the ergodic layer is varied with three-dimensional structure. (author)
Cui, Xiaoyang; Wu, Simiao; Zeng, Quantao; Xiao, Jiahe; Liu, Ming
2015-02-01
To investigate the correlations of atheromatous plaques in the aortic arch or supra-aortic arteries with intracranial arterial stenosis and carotid plaques in stroke patients, and to determine whether taking these plaques into account will reduce the proportion of patients in the undetermined etiology group. We prospectively enrolled 308 ischemic stroke patients, whose clinical characteristics and A-S-C-O classifications were compared with analyses of intracranial arteries, carotid arteries, aortic arch, and supra-aortic arteries. 125(40.6%) patients had plaques in the aortic arch or supra-aortic arteries, of which 106 (84.8%) had complex plaques. No correlations were observed between these plaques and carotid plaques ( p = 0.283) or intracranial arterial stenosis ( p = 0.097). After detecting the mobile thrombi in the aortic arch and supra-aortic arteries, the proportion of patients in the atherothrombosis group was increased from 33.8% to 55.5% ( p = 0.00), whereas the proportion of patients in stroke of undetermined etiology group was decreased from 19.2% to 11.0% ( p = 0.00). Examining only the carotid and intracranial arteries may not provide adequate information about large arteries in stroke patients. Therefore, it would be better to include a search for relevant plaques in the aortic arch or supra-aortic arteries in modern stroke workup, for it may lead to more accurate stroke subtype classification and guide secondary prevention.