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Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened. Peer Reviewed Article escrit per 365 autors/autores: Labit, B.; Eich, T.; Harrer, G. F.; Wolfrum, E.; Bernert, M.; Dunne, M. G.; Frassinetti, L.; Hennequin, P.; Maurizio, R.; Merle, A.; Meyer, H.; Saarelma, S.; Sheikh, U.; Adamek, J.; Agostini, M.; Aguiam, D.; Akers, R.; Albanese, R.; Albert, C.; Alessi, E.; Ambrosino, R.; Andr be, Y.; Angioni, C.; Apruzzese, G.; Aradi, M.; Arnichand, H.; Auriemma, F.; Avdeeva, G.; Ayllon-Guerola, J. M.; Bagnato, F.; Bandaru, V. K.; Barnes, M.; Barrera-Orte, L.; Bettini, P.; Bilato, R.; Biletskyi, O.; Bilkova, P.; Bin, W.; Blanchard, P.; Blanken, T.; Bobkov, V.; Bock, A.; Boeyaert, D.; Bogar, K.; Bogar, O.; Bohm, P.; Bolzonella, T.; Bombarda, F.; Boncagni, L.; Bouquey, F.; Bowman, C.; Brezinsek, S.; Brida, D.; Brunetti, D.; Bucalossi, J.; Buchanan, J.; Buermans, J.; Bufferand, H.; Buller, S.; Buratti, P.; Burckhart, A.; Calabr, G.; Calacci, L.; Camenen, Y.; Cannas, B.; Cano Megías, P.; Carnevale, D.; Carpanese, F.; Carr, M.; Carralero, D.; Carraro, L.; Casolari, A.; Cathey, A.; Causa, F.; Cavedon, M.; Cecconello, M.; Ceccuzzi, S.; Cerovsky, J.; Chapman, S.; Chmielewski, P.; Choi, D.; Cianfarani, C.; Ciraolo, G.; Coda, S.; Coelho, R.; Colas, L.; Colette, D.; Cordaro, L.; Cordella, F.; Costea, S.; Coster, D.; Cruz Zabala, D. J.; Cseh, G.; Czarnecka, A.; Cziegler, I.; D’Arcangelo, O.; Dal Molin, A.; David, P.; De Carolis, G.; De Oliveira, H.; Decker, J.; Dejarnac, R.; Delogu, R.; Den Harder, N.; Dimitrova, M.; Dolizy, F.; Domínguez-Palacios Durán, J. J.; Douai, D.; Drenik, A.; Dreval, M.; Dudson, B.; Dunai, D.; Duval, B. P.; Dux, R.; Elmore, S.; Embréus, O.; Erds, B.; Fable, E.; Faitsch, M.; Fanni, A.; Farnik, M.; Faust, I.; Faustin, J.; Fedorczak, N.; Felici, F.; Feng, S.; Feng, X.; Ferreira, J.; Ferr, G.; Février, O.; Ficker, O.; Figini, L.; Figueiredo, A.; Fil, A.; Fontana, M.; Francesco, M.; Fuchs, C.; Futatani, S.; Gabellieri, L.; Gadariya, D.; Gahle, D.; Galassi, D.; Gałązka, K.; Galdon-Quiroga, J.; Galeani, S.; Gallart, D.; Gallo, A.; Galperti, C.; Garavaglia, S.; Garcia, J.; Garcia-Lopez, J.; Garcia-Mu oz, M.; Garzotti, L.; Gath, J.; Geiger, B.; Giacomelli, L.; Giannone, L.; Gibson, S.; Gil, L.; Giovannozzi, E.; Giruzzi, G.; Gobbin, M.; Gonzalez-Martin, J.; Goodman, T. P.; Gorini, G.; Gospodarczyk, M.; Granucci, G.; Grekov, D. 1; Grenfell, G.; Griener, M.; Groth, M.; Grover, O.; Gruca, M.; Gude, A.; Guimarais, L.; Gyergyek, T.; Hacek, P.; Hakola, A.; Ham, C.; Happel, T.; Harrison, J.; Havranek, A.; Hawke, J.; Henderson, S.; Hesslow, L.; Hitzler, F.; Hnat, B.; Hobirk, J.; Hoelzl, M.; Hogeweij, D.; Hopf, C.; Hoppe, M.; Horacek, J.; Hron, M.; Huang, Z.; Iantchenko, A.; Iglesias, D.; Igochine, V.; Innocente, P.; Ionita-Schrittwieser, C.; Isliker, H.; Ivanova-Stanik, I.; Jacobsen, A.; Jakubowski, M.; Janky, F.; Jardin, A.; Jaulmes, F.; Jensen, T.; Jonsson, T.; Kallenbach, A.; Kappatou, A.; Karpushov, A.; Kasilov, S.; Kazakov, Y.; Kazantzidis, P. 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T.; Walkden, N.; Wauters, T.; Weiland, M.; Weinzettl, V.; Wensing, M.; Wiesen, S.; Wiesenberger, M.; Wilkie, G.; Willensdorfer, M.; Wischmeier, M.; Wu, K.; Xiang, L.; Zagorski, R.; Zaloga, D.; Zanca, P.; Zaplotnik, R.; Zebrowski, J.; Zhang, W.; Zisis, A.; Zoletnik, S.; Zuin, M.

Measurements and simulations with the UEDGE code of radiated power, and ion saturation currents and power loads to the target plates have been compared for density scans in ohmic and low confinement mode plasmas in DIII-D, ASDEX Upgrade, and JET. Simulations including cross-field drifts and assuming elevated chemical sputtering yields of 3%–4% move the numerical solutions closer to many of the measurements compared to omitting the drifts and using the published Davis–Haasz yields. Adopting these assumptions the simulations reproduce the measured currents and powers, and their functional dependence on upstream density to within a factor of 2, with the exception of the ion currents to the low field side target in ASDEX Upgrade and the high field side target in JET. The applicability of using enhanced sputtering yields is discussed by comparing measured and simulated emission from low charge state carbon in the divertor regions.

This contribution examines the impact on plasma radiation and on power load to the divertor (i) of large type I ELMs with energies 0.25–1.3 MJ in high current H-mode JET discharges and (ii) of disruptions. (i) The ELMs provoke strong radiation losses, mostly confined to the inner divertor region. Large type I ELMs with ΔWELM ⩾ 0.72 MJ show enhanced radiation losses which are associated with the ablation of carbon layers in the inner divertor. Such large ELMs are usually followed by a phase of type III ELMs with an increased radiation in the plasma core. (ii) The unmitigated disruptions exhibit small radiation fractions with strong poloidal radiation asymmetry during the thermal quench, which could cause Be melting by radiation in ITER. In dedicated experiments on massive gas injection, about 60% of the thermal energy and a significant part of the magnetic energy was converted in radiation and spread uniformly over the first walls.

Multi-fluid plasma edge code packages, usually coupled to Monte-Carlo transport codes for neutrals are in wide use in the fusion community to simulate the SOL and divertor. A status of the current code validation effort is presented using experimental data of Ohmic and L-mode discharges from ASDEX Upgrade for He in forward toroidal field, BT, only and for D fueled in forward and reversed BT in lower single null configurations. While satisfactory agreement between simulated and experimental data can be obtained for both divertors as long as one of the two divertors is not strongly recombining, the qualitative behavior as a function of line averaged density cannot be recovered in the simulations for higher recycling regimes. This holds independently of field direction or fueling species. Semi-empirical models and thus far not included physics models are discussed.

A major challenge in nuclear fusion research is the coherent combination of measurements from heterogeneous diagnostics. Different measurement techniques for measuring the same subset of physical p...

Carbon transport in the ASDEX Upgrade outer divertor plasma is investigated in numerical simulations. The SOLPS5.0 code package is used to model the scrape-off layer plasma in a set of repeated lower-single-null L-mode discharges. Special emphasis is given to replicate the plasma conditions measured in the full tungsten, vertical outer target of ASDEX Upgrade, and solutions with and without the effect of drifts are presented. First ERO simulations of hydrocarbon transport in a SOLPS plasma background including drifts are carried out, and significantly closer match to the experimental 13C deposition pattern is obtained than with the solution without drifts. The 2D divertor electric field predicted by SOLPS is applied to the ERO modelling, and it is observed to result in a poloidal hydrocarbon drift that agrees well with the experiment. An increased carbon deposition efficiency, particularly upstream from the source, is obtained in the normal ASDEX Upgrade field configuration (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The development of the baseline H-mode scenario foreseen for ITER on the ASDEX Upgrade tokamak, i.e. discharges at q 95 = 3, relatively low β N ~ 1.8, high normalized density n/n GW ~ 0.85 and high triangularity δ = 0.4, focused on the integration of elements foreseen for ITER and available on ASDEX Upgrade, such as ELM mitigation techniques and impurity seeding in combination with a metallic wall. Values for density and energy confinement simultaneously came close to the requirements of the ITER baseline scenario as long as β N stayed above 2. At lower heating power and thus lower β N normalized energy confinement H 98y2 ~ 0.85 is obtained. It has been found that stationary discharges are not easily achieved under these conditions due to the low natural ELM frequency occurring at the low q 95/high δ operational point. Up until now the ELM parameters were uncontrollable with the tools developed in other scenarios. Therefore studies on an alternative operational point at higher β N and q 95 have been conducted. In order to prepare for the ITER first non-activation operational phase, Helium operation has been investigated as well.

Detailed modelling of the plasma edge of ASDEX Upgrade in Ohmic and H-mode discharges was performed with the SOLPS (B2-EIRENE) code. A tendency of the code solutions to underestimate the divertor T e and overestimate the plasma density (thus, predicting cooler and denser divertor than in the experiment) has been reliably established. A possible cause of the observed discrepancies is the presence of a significant population of supra-thermal ions and electrons in the SOL and divertor, which cannot be modelled by the fluid plasma code B2.

In ASDEX Upgrade, a fast reciprocating probe positioned in the lower divertor, capable of accessing the low-field side (LFS) and high-field side (HFS) scrape-off layer (SOL) just below the x-point, as well as the private flux region, was equipped with a Mach head and used to investigate fast flow fluctuations and in–out divertor flow asymmetries during ELMs. We compare the flow behaviour during ELMs in the three separate regions. Flow enhancement is observed in the HFS SOL, with Mach number values reaching or exceeding M = 2, flow reversal in the LFS SOL, and complex fluctuating behaviour in the private flux region (which includes flow reversal). We discuss the possible mechanisms that could drive these observations.

An extracorporeal procedure is described for the selective removal of LDL from patients with familial hypercholesterolemia. It comprises plasmapheresis followed by selective precipitation of LDL from plasma with heparin at low pH. The LDL-heparin complex is then removed by filtration and the clear plasmafiltrate subjected to bicarbonate dialysis to restore physiological pH and maintain fluid and electrolyte balance. The capacity and efficiency of the system for the selective elimiation of LDL was confirmed by in vitro studies with three liters of plasma from a hypercholesterolemic patient. Extensive animal investigations have demonstrated the applicability and biocompatibility of the procedure. This has been further confirmed by a first application in a human volunteer.

A low density H-mode plasma has been selected for detailed inter-ELM modelling by the SOLPS code package, with the coupled treatment of its plasma (fluid code B2) and neutral (Monte-Carlo code Eirene) parts. Good quality measured midplane density and temperature profiles, covering the pedestal region and stretching far into the SOL, as well as several other parameters and profiles measured in the divertor, have enabled testing the consistency of code solutions with experiment. Once the upstream, midplane profiles have been fitted, and the global parameters (e.g. input power into the computational grid, radiated power) matched, the code reproduces experimental profiles and control parameters in the divertor with an accuracy within a factor of 2. Deviations of modelled parameters from the experiment were found around the strike point position where most of the power was deposited on the target. The deviations are consistent among themselves and all point to one common problem with the modelling: the predicted divertor electron temperature is too low and the density too high, compared with the experiment. The largest inconsistency between the code and experiment was in the magnitude of the peak Hα radiation in the outer divertor, which was larger by a factor of 2 in the code simulations. In addition, the code predicts a somewhat higher sub-divertor neutral flux but lower carbon impurity content in the edge plasma than in the experiment, as well as lower CIII emission. The discrepancy between Hα profiles can to a large degree be attributed to profile effects: the simulated Hα emission profiles are narrower than in the experiment, reflecting the tendency of the neutral–plasma mix to congregate excessively around the strike point in the modelling. At the same time, the integrated Hα emission matches very well with the experiment.Extensive sensitivity studies of the influence of variations in input parameters and assumptions of the code on the modelled divertor conditions have been conducted. They have not resulted in an identification of any SOLPS input/control parameters capable of removing the main disagreement between the code output and experiment. A possibility of parallel transport effects related to low collisionality to increase the effective plasma temperature near the strike point position or of increased perpendicular transport by neutrals (due to some missing reactions in Eirene) to widen the target profiles, will be explored in the future.

Heat deposition onto plasma facing components outside the divertor by ELMs and fast particles has been investigated in ASDEX Upgrade. Heat fluxes up to tens of megawatts per square meter are found during ELMs on limiters and a few megawatts per square meter in between. The total deposited power on non-divertor structures can be up to 10% of the heating power and has to be considered for high power next step experiments. The mechanisms behind the observed heat load patterns are qualitatively understood. The main contributions come from fast ions created by neutral beam injection (and ion cyclotron minority) heating, and from ELMy energy bursts from the plasma edge.

An integrated exhaust scenario has been developed in ASDEX Upgrade providing simultaneous control of particle exhaust, time averaged divertor power flux and ELM power via pace-making of the ELM frequency. Feedback quantities are the divertor neutral flux (actuator: deuterium gas puff) and the divertor temperature as measured by thermoelectric currents (actuator: argon gas puff). The ELM frequency is stabilised to a level high enough for moderate ELM power load with repetitive injection of small pellets from the high field side. The scenario is fully compatible with the present tungsten wall coating, which constitutes about 65% of the area of the plasma facing components. It is intended for application in a future full-tungsten ASDEX Upgrade with strongly reduced intrinsic carbon radiation in order to simulate a possible full-tungsten stage of ITER.

At certain values of the edge rotational transform ιa, the confinement quality of plasmas in the Wendelstein 7-AS (W7-AS) stellarator is found to react very sensitively to small modifications of the edge rotational transform ιa. As ιa can be reproducibly changed either by external fields or by a small plasma current, these transitions offer a precise way to systematically analyse differences in plasma turbulence between bad and good confinement cases. This paper presents results of the study of electron density fluctuations associated with confinement changes. Wavenumber and frequency spectra and radial profiles are compared. A slow and reproducible transition is induced by a small plasma current and the sequence of events leading to bad confinement is investigated. The laser scattering core plasma density fluctuation measurements are complemented by edge beam emission spectroscopy results and magnetic fluctuation measurements with Mirnov coils. Clear correspondence between plasma fluctuations and confinement degradation is observed: the weight of larger structures increases, fluctuations increase in the plasma core, the poloidal flow velocity decreases and regions of mode-like activity move radially in the plasma. These changes occur gradually and controllably if the magnetic configuration is steered by a small plasma current.

High-confinement (H-mode) operation is the choice for next-step tokamak devices based either on conventional or advanced tokamak physics. This choice, however, comes at a significant cost for both the conventional and advanced tokamaks because of the effects of edge localized modes (ELMs). ELMs can produce significant erosion in the divertor and can affect the beta limit and reduced core transport regions needed for advanced tokamak operation. Experimental results from DIII-D [J. L. Luxon et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] this year have demonstrated a new operating regime, the quiescent H-mode regime, which solves these problems. We have achieved quiescent H-mode operation that is ELM-free and yet has good density and impurity control. In addition, we have demonstrated that an internal transport barrier can be produced and maintained inside the H-mode edge barrier for long periods of time (>3.5 s or >25 en...

Intense bursts of nonthermal electron cyclotron emission (ECE) have been observed in H-mode (high confinement) discharges in the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)], measured with heterodyne radiometers and a broadband far infrared (FIR) detector. These bursts are triggered by edge-localized modes (ELMs) and consist of single or several spikes, most lasting 5–150 μs. Radiation temperatures reach up to several MeV. Observed spectral bandwidths are typically less than 4 GHz. Bandwidths as low as 500 MHz, which is the limit of the instrumental filter spacing, have been found. Statistical analysis shows a steady decrease of the number of spikes with rising spike energy. Burst frequencies seem to depend linearly on the magnetic field. It is speculated that the bursts are coherent second harmonic ECE.

A new second harmonic heterodyne ECE system, which is suitable for the future W7-X stellarator, has been developed and tested at W7-AS. It completes the older W7-AS system. The design was aimed at using less components and improving the system noise compared to the older system. A technical description and first measurements are presented.

Plasma discharges at W7-AS in the ‘electron root’ regime show highly peaked electron temperature- and pressure profiles. A switch-off of the ECRH leads to a fast temperature drop with time constants of less than 1 ms and a corresponding change of the Shafranov shift in the center of the plasma. For a temporally resolved comparison between calculated and measured temperature profiles, a fast method of gaining the mapping of the magnetic field to the radius along the ECE sightline is presented. Using these mappings to compare measured ECE signals with modeled temperatures (assuming plausible profiles of the radial electrical field), the time constant for the decay of the electric field after a ECRH power switch-off was found to be 0.6 ms.

A new radiometer has been built up for the W7-AS stellarator which consists of a frontend with an extreme broadband mixer, two intermediate frequency (IF) parts with 16 channels each and a novel additional 16 filter section with variable IF. The system was designed with the future W7-X in mind. All settings can therefore be remotely changed. This “W7-X” system is integrated into the electron cyclotron emission (ECE) systems at W7-AS. EC radiation is collected using elliptical mirrors in Gaussian optics. W7-AS results will be shown. The “zoom” device is installed at DIII-D at the moment; first results are also shown.

Density-limit discharges in the W7-AS stellarator, with constant line-integrated density and a duration of up to 2 s, were studied at three values of the toroidal magnetic field (B = 0.8, 1.25 and 2.5 T). The central factor governing the physics of the density limit in stellarators was demonstrated to be the decreasing net power to the plasma when the centrally peaked radiated power density profile exceeds that of the deposited power density. The process was further accelerated by the peaking of electron density under these conditions. In discharges with B = 2.5 T, simulations of the centrally peaked radiation power density profiles could be shown to be due to peaked impurity density profiles. Laser blow off measurements clearly inferred an inward pinch of the injected aluminium. These discharges had the electron density profile form found in the improved confinement H-NBI mode on W7-AS. The aim of producing steady-state discharges at the highest possible density in stellarators is naturally of special interest for reactor operation. Such a scenario has been best achieved in H-mode discharges, in which ELMs restricted the impurity influx to the plasma and an equilibrium in the plasma parameters with suitably low radiation power levels was possible. A density scan in ECRH discharges highlights the need to control impurity sources and choose electron densities well below the density limit in order that steady-state operation can be attempted in discharges without ELMs. A simple model of bulk radiation predicted that the limiting density should depend on the square root of heating power and this was experimentally confirmed. The magnetic field scaling of the limiting density found experimentally in this simple model will partly depend on the term concerning the radial profile of the impurity density, which in turn is a function of the diffusion coefficient and inward pinch of the impurity ions. Theoretical studies have shown that an assumption about the B dependence of the thermal conductivity leads to density limit scaling laws with an explicit B dependence.

H-mode operation in the low-shear stellarator W7-AS is achieved for specific plasma edge topologies characterized by three `operational windows' of the edge rotational transform. An explanation for this strong influence of the magnetic configuration could be the increase of viscous damping if rational surfaces and thus island structures occur within the relevant plasma edge layer, thereby impeding the development of an edge transport barrier. Prior to the final transition to a quiescent state, the plasma edge passes a rich phenomenology of dynamic behaviour such as dithering and ELMs. Plasma edge parameters indicate that a quiescent H-mode occurs if a certain edge pressure is achieved.

The CERES/NA45 experiment at the CERN-SPS is dedicated to study the production of e + e − -pairs in ultrarelativistic heavy ion collisions. Compared to extrapolations from results obtained in proton-induced reactions, it has previously observed an enhanced production in S-Au [1] and Pb-Au [2] collisions. To verify this enhancement and to study its properties, higher statistics were accumulated during a runtime in 1996. We report here, for the first time, on the results of this analysis (for details see ref. [3]).

The behaviour of carbon in the divertor of ASDEX-Upgrade is investigated by means of optical spectroscopy, bolometry and thermography. Apparent chemical erosion yields, derived from CH molecular band emission and H β spectroscopy are shown to exhibit a pronounced flux dependence and isotope effect, Y chem m H x Γ -0.7 , while no dependence on surface temperature (T surf < 100°C) and impact energy is seen. The flux and isotope dependences also show up in the CII, CIII and total carbon radiation. The weak correlation between the carbon yields in the divertor and the core plasma carbon concentration supports the assumption that main chamber sources are important for the core plasma carbon content under the low temperature, high recycling conditions of this study.

A new divertor was installed in ASDEX Upgrade and went into operation in spring of 1997. The divertor was designed to handle heat fluxes relevant to ITER-like scenarios. For this, the tiles expected to receive the maximum load (strike point modules) are hardened by the use of carbon fibre composites covering about 20% of the total divertor area. The maximum heat flux detected by thermography in a H-mode discharge is only 4 MW/m 2 or below for a total input power of 20 MW without radiating mantle, except some ELMs showing a moderately higher heat flux. A broad distribution of the power load found in the measured poloidal distribution of the heat flux as well as the energy distribution, shows that less than half of the power flowing into the divertor is received by the strike point modules. The remaining power is loaded to other tiles of the divertor, particularly the transition module and parts of the roof baffle near to the strike point modules. The reconstructed radiation pattern reveals that the fraction of power radiated outside the divertor is comparable for both geometries. But the radiated fraction inside the divertor is increased by 10-15% in the Lyra shaped divertor.

Radiation losses in divertor I of ASDEX Upgrade have been studied at high density when the divertor is detached. Spectroscopic measurements in the visible and VUV spectral range allow a characterization of both the impurity source and radiation. Despite very low target temperatures of 1 eV, carbon is released from the target with high rates by chemical sputtering. Power losses are estimated from the resonance lines of deuterium and the carbon ions. A comparison with bolometry shows that 80% of the emission can be ascribed to carbon and deuterium. The composition of the carbon emission is compared with results obtained on JT-60 and DIII-D. Using the Braams-Eirene model of the detached divertor the influence of transport on the power losses is investigated. By means of a realistic radiative loss function we find that the enhancement of maximum power input into the divertor by non-coronal effects is not more than a factor of two.

A polarimeter based on the Cotton–Mouton effect has been developed and installed at the W7-AS stellarator. It is operated in the submillimeter wave region at frequencies of 500–650 GHz. The polarimeter demonstrated its capability to perform absolute, robust measurements of the line integrated electron density. The change of the state of polarization is calculated with high accuracy using Segre’s formalism. By varying the frequency and the B field, it could be shown that the Faraday effect has negligible influence on the measurements.

A Cotton-Mouton effect polarimeter operating in the submillimeter wave region has been developed at the W7-AS stellarator. The transmission matrix representative for the change of polarization state of a probing wave has been calculated and significant elements are determined experimentally. Systematic magnetic field scans over a wide range of the magnetic field conducted at two different probing frequencies were carried out for the first time. These scans clearly demonstrate that the Cotton-Mouton effect is being observed under optimal experimental conditions. The experimental setup measures the line integrated electron density unambiguously and has proven its robustness under various conditions.

Hadronic spectra from interactions of Pb on Au at 158 AGeV/c have been measured by the CERES experiment at the CERN SPS. We report on preliminary results on transverse mass spectra of identified pions and negative hadrons as well as spectra of the positive charge excess obtained by subtracting the negative particle distribution from that of positive tracks. We have also performed a study of the event azimuthal anisotropies which give evidence for directed and elliptic flow in non-central collisions.

The CERES/NA45 collaboration measured, at the CERN SPS, low-mass electron pair production in Pb Au collisions at 158 A GeV/c incident momentum. In this paper we present an analysis of the data taken during the SPS Pb-beam period in the fall of 1995. The results confirm previous findings of CERES showing that the pair production in the mass range 0.2 ee 2 , when scaled to the ion case with the event multiplicity, is enhanced over the expected yield from the known hadronic sources in pp collisions. A comparison of the results for different multiplicity bins indicates that the excess increases faster than linearly with charged-particle multiplicity. We also present the transverse-momentum distributions of the observed pairs.

Gewohnlich wird bei der Herleitung der Wellengleichung fur das magnetische Vektorpotential A im Rahmen der Lorentz-Eichung rein formal eine Quellenfeldkomponente A Q eingefuhrt, deren Interpretation dem Leser uberlassen bleibt. Die vorliegende Arbeit zeigt die physikalische Bedeutung dieser Komponente auf und veranschaulicht die Unterschiede zwischen Coulomb-Eichung und Lorentz-Eichung.

A simple analytic model of divertor radiation is used as a framework for identifying different routes to divertor detachment. Three means of achieving detachment are demonstrated experimentally including, increasing plasma density, purposely increasing the impurity level and increasing the scrape-off layer connection length. The resulting low electron temperatures in the divertor causes friction processes to dominate ionization in the recycling region, giving rise to plasma pressure loss along field lines. The pressure loss is in approximate agreement with simple analytic modelling.

Power exhaust is one of the critical questions to be solved for ITER, especially with the side condition of sufficient particle exhaust. Since the H-mode threshold might require a high power flux over the separatrix, only small power losses inside the bulk plasma might be permitted, and thus eventually a large fraction of the power must be removed in the scrape-off layer and divertor plasma. Neutral energy losses can only remove a small fraction of the power, and therefore most of the power flux has to be radiated, either by hydrogen isotopes, by the intrinsic impurities (mainly carbon) or by additionally seeded impurities. However, all these scenarios with reduced power flow to the divertor imply also a reduced particle flow into the divertor. This might be critical for particle exhaust, especially concerning the helium ash. Reduction of the power flow to the divertor by enhanced radiation losses has been investigated in the large divertox experiments like JET, DIII-D, ASDEX Upgrade, and JT-60U, and an experimental overview of the present status will be given in this paper, together with a discussion of impurity exhaust (mainly He and Ne) in these scenarios.

In this paper we describe impurity line emission measurements in the divertor of ASDEX Upgrade during high power neutral beam heated discharges. We focus on detached conditions where the dominating part of the radiation comes from the X-point region. Spatially resolved line emission in the VUV and visible spectral region of the intrinsic carbon and additionally puffed impurities (neon and nitrogen) is presented. A simple interpretation of the line emission profiles is given and they are also compared to the results of bolometry.

We report preliminary results of the first measurement of low-mass electron pairs in 160 GeV/nucleon PbAu collisions at central rapidities in a wide multiplicity range. This work is the continuation of our systematic studies on pair production in p-Be, p-Au and SAu interactions. The motivation for this effort derives from a new source of lowmass dileptons recently observed in SAu and S-W collisions by CERES and HELIOS/3, respectively. The results obtained in the analysis of the PbAu data confirm our previous finding that pair production in the mass range 0.2 < mee < 1.5 GeV/c2 is enhanced over the contributions from hadron decays while no significant excess could be observed for mee ≲ 2mπ. A comparison of the results for different multiplicity bins favours a non-linear dependence of the e+e−-yield on the accompanying charged particle densities.

We report on the performance of a doublet of 3 in. cylindrical silicon drift detectors installed as an upgrade of the CERES/NA45 electron pair spectrometer for the Pb-beam at the CERN SPS. The silicon detectors provide external particle tracking and background rejection of conversions and close Dalitz pairs. Results on vertex reconstruction and rejection from a Pb test-run in 1994 are presented.

CERES is an experiment dedicated to measure e+ e−-pairs in nucleus-nucleus collisions at the CERN SPS. Following the experiences gained with proton and sulfur beams the CERES spectrometer was upgraded to cope with the much larger charged particle densities produced in PbPb collisions. Major parts of the upgrade were completed in time for a 10 days test with a lead beam in November 1994. The results clearly demonstrate the feasibility of the experiment in the environment of central PbPb collisions.

Phase-space time-resolved measurements of fast-ion losses induced by edge localized modes (ELMs) and ELM mitigation coils have been obtained in the ASDEX Upgrade tokamak by means of multiple fast-ion loss detectors (FILDs). Filament-like bursts of fast-ion losses are measured during ELMs by several FILDs at different toroidal and poloidal positions. Externally applied magnetic perturbations (MPs) have little effect on plasma profiles, including fast-ions, in high collisionality plasmas with mitigated ELMs. A strong impact on plasma density, rotation and fast-ions is observed, however, in low density/collisionality and q(95) plasmas with externally applied MPs. During the mitigation/suppression of type-I ELMs by externally applied MPs, the large fast-ion bursts observed during ELMs are replaced by a steady loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the neutral beam injection (NBI) prompt loss signal without MPs. Multiple FILD measurements at different positions, indicate that the fast-ion losses due to static 3D fields are localized on certain parts of the first wall rather than being toroidally/poloidally homogeneously distributed. Measured fast-ion losses show a broad energy and pitch-angle range and are typically on banana orbits that explore the entire pedestal/scrape-off-layer (SOL). Infra-red measurements are used to estimate the heat load associated with the MP-induced fast-ion losses. The heat load on the FILD detector head and surrounding wall can be up to six times higher with MPs than without 3D fields. When 3D fields are applied and density pump-out is observed, an enhancement of the fast-ion content in the plasma is typically measured by fast-ion D-alpha (FIDA) spectroscopy. The lower density during the MP phase also leads to a deeper beam deposition with an inward radial displacement of approximate to 2 cm in the maximum of the beam emission. Orbit simulations are used to test different models for 3D field equilibrium reconstruction including vacuum representation, the free boundary NEMEC code and the two-fluid M3D-C1 code which account for the plasma response. Guiding center simulations predict the maximum level of losses, approximate to 2.6%, with NEMEC 3D equilibrium. Full orbit simulations overestimate the level of losses in 3D vacuum fields with approximate to 15% of lost NBI ions.

The impact of edge localized modes (ELMs) and externally applied resonant and non-resonant magnetic perturbations (MPs) on fast-ion confinement/transport have been investigated in the ASDEX Upgrade (AUG), DIII-D and KSTAR tokamaks. Two phases with respect to the ELM cycle can be clearly distinguished in ELM-induced fast-ion losses. Inter-ELM losses are characterized by a coherent modulation of the plasma density around the separatrix while intra-ELM losses appear as well-defined bursts. In high collisionality plasmas with mitigated ELMs, externally applied MPs have little effect on kinetic profiles, including fast-ions, while a strong impact on kinetic profiles is observed in low-collisionality, low q 95 plasmas with resonant and non-resonant MPs. In low-collisionality H-mode plasmas, the large fast-ion filaments observed during ELMs are replaced by a loss of fast-ions with a broad-band frequency and an amplitude of up to an order of magnitude higher than the neutral beam injection prompt loss signal without MPs. A clear synergy in the overall fast-ion transport is observed between MPs and neoclassical tearing modes. Measured fast-ion losses are typically on banana orbits that explore the entire pedestal/scrape-off layer. The fast-ion response to externally applied MPs presented here may be of general interest for the community to better understand the MP field penetration and overall plasma response. Ministerio de Economía y Empresa ((RYC-2011-09152 y ENE2012-31087) Marie Curie (Grant PCIG11-GA-2012-321455) US Department of Energy (DE-FC02-04ER54698, SC-G903402, DE-FG02-04ER54761, DE-AC02-09CH11466 and DE-FG02- 08ER54984) NRF Korea contract 2009-0082012 MEST under the KSTAR project

The completely detached high confinement (CDH) regime established recently in high power ASDEX-Upgrade single null divertor discharges is described. The standard CDH mode scenario with feedback controlled external deuterium and neon puffing is analysed in detail with respect to its divertor detachment and confinement properties. Impurity transport and pumping effects and the density operation windows of the CDH mode are outlined. First results with other impurity radiators (N,Ar) are given. Finally the CDH mode operation space is discussed in terms of main chamber and scrape-off layer plus divertor radiation and possible consequences for future fusion experiments are outlined.

This paper presents a new method in TLM for very efficient computation of highly conducting thin shielding walls. Firstly, the impulse response of a finite conducting sheet is computed analytically via inverse Laplace transform. Subsequently, a recursive convolution integral is formulated with the analytical impulse response. This allows a very efficient and accurate calculation of the diffusion process through imperfectly conducting walls.

Detailed experimental divertor data are presented on the profiles of density and temperature in the inner and outer divertor fans, the radiated power distribution, the gas pressure and the spectroscopically derived particle fluxes, all as a function of the discharge density. At low and medium density, the inner divertor is cold and dense compared to the outer divertor. At high density, strong X-point MARFE and separatrix radiation partially detaches the inner divertor. Probe measurements which penetrate into the X-point MARFE at the outer divertor are presented.

We have for the first time identified e + e − -pairs produced by strongly varying electromagnetic fields in distant SPt collisions at 200 GeV/u projectile energy at the CERN-SPS. The differential cross section for the mass range 10 MeV/ c 2 ≤ m ee ≤ 100 MeV/ c 2 and the polar angle range 141 mrad ≤ θ e ≤ 260 mrad agrees well with a lowest-order perturbation QED-calculation.

The H-mode obtained in ASDEX Upgrade by three heating methods (Ohmic, NBI, ICRF) is analysed. The power threshold is shown to be relatively low compared with other tokamaks and to be independent of the heating method. The operational window for the different types of H-phases, (dithering, ELMing with type-III and I ELMs, ELM-free) is given and discussed. The features of the H-mode discharges, in particular quasi-stationary ELMing phases with type I ELMs, are described and discussed. Finally, it is shown that the power flux through the plasma edge is a key parameter for H-mode operation and control.

The dynamic behaviour of the L-H transition in ASDEX Upgrade is described. We focus on two dynamic phenomena: Dithering Cycles and ELMs. The Dithering Cycles are characterized experimentally; then, a theoretical model is presented which explains the cycle as a limit cycle oscillation at the transition. With regard to ELMs, the modulation of heat and particle fluxes into the divertor due to ELMs is studied, quantitative results from thermography of the target plates are given.

ASDEX Upgrade is a poloidal divertor experiment very similar to ITER with respect to magnetic field properties and especially to the plasma boundary geometry. A large part of the programme on ASDEX Upgrade is therefore dedicated to investigating and optimizing reactor-relevant plasma boundary issues. This contribution is concerned with H-mode studies and edge physics in general. The L/H-power threshold, H-mode confinement, details of ELM dynamic and 'dithering' L/H-transitions will be discussed. The edge physics investigations are concerned with model calculations and validations, the characteristic 'approach' to the density limit (DL), target plate sputtering and the influence of hydrocarbons, asymmetries and drifts depending on the direction of the toroidal magnetic field, and finally first results of high-Z material experiments.

Demographic changes of the industrialised modern society can be recognised throughout every medical specialisation. In the past plastic surgery had a main focus in the reconstruction of posttraumatic disorders but nowadays the typical disorders of the elderly and "civilization diseases" became a major part of reconstructive surgery. In this context the preservation of the lower extremity is a major concern of the plastic surgeon. Especially in patients with diabetes and its typical peripheral atherosclerosis we have to treat peripheral ulcers in an interdisciplinary setting including diabetologist, vascular and plastic surgeon to preserve the endangered extremity.

SOLPS simulation of a dedicated ASDEX Upgrade Ohmic shot for scrape-off layer and divertor modelling is described. The tendency of the code to predict a colder and denser divertor plasma compared with the experiment for solutions that satisfy main boundary conditions (on the input power across the core/edge boundary, particle throughput and radiated power) and match upstream profiles is confirmed. Issues related to the role of neutral sources and sinks are discussed. In the interpretative modelling based on experimental upstream profiles, neither the neutral pressure in the divertor nor the method of fuelling was found to strongly influence the parameters at the outer target, which are primarily determined by the input power and separatrix density.

Thermal injuries of more than 20% of body surface area lead to conditions resembling a severe systemic inflammatory response syndrome, such as in septic shock. It has been shown that septic shock may lead to disturbances in cortisol metabolism and balance of the hypothalamic-pituitary-adrenal axis. To investigate whether such a disturbance also occurs in the very early stages of systemic inflammatory response syndrome in burned patients, we performed 20 corticotropin-releasing hormone tests on day 1 after admission to our unit. In 7 of 20 patients, a disturbance of cortisol secretion could be demonstrated. Four patients developed adrenal insufficiency. The correlation between the abbreviated burn severity index and the risk of developing adrenal insufficiency was significant (P = 0.008). We observed a higher mortality rate in adrenally insufficient patients; however, because of the small patient number, we were not able to prove this observation with a statistical significant correlation (P = 0.11). Our findings indicate that temporary adrenal insufficiency occurs in the early stages of severe injury. Further investigations will have to be performed to clarify whether such patients benefit from cortisol replacement.

The influence of electron heating compared to ion heating on plasma performance has been analysed in order to make valid projections towards future devices. The capabilities of the newly upgraded electron cyclotron resonance heating system at ASDEX Upgrade make this analysis feasible by replacing neutral beam injection. Dominantly electron heated plasmas are analysed and compared to dominantly ion heated plasmas. It is investigated if they behave systematically different or if the change of heated species is fully compensated by heat exchange from electrons to ions. Studies of plasmas at high collisionalities are presented in Sommer et al (2012 Nucl. Fusion 52 114018). Here, these former investigations are extended towards lower collisionalities. The global plasma parameters show a slight reduction with increasing electron heating arising from a significant decrease of the ion temperature, whereas the electron temperature profile is unchanged. The density profile shows a strong peaking which remains unchanged when modifying the heating mix. The power balance analysis shows an important impact of the heat exchange between electrons and ions. The electron and ion temperatures and the plasma density are modelled with the transport model TGLF. The experimental observations are reproduced verifying the applied code. Linear gyrokinetic calculations with GS2 found the ion temperature gradient mode to be the dominant microinstability in all analysed cases.