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On ASDEX Upgrade first experiments were made using single probes with a voltage sweep frequency up to 100kHz. Possibilities and limitations using fast swept probes with a standard diagnostic and analysis tools are discussed. A good agreement between the data derived from fast swept single probe characteristics and floating as well as saturation current measurements was found. In a stationary (non ELMing) plasma the data of the fast swept probe are compared to standard slow swept probes (kHz range) showing an improvement of the measurement by faster sweeping. While ELM filaments already could be resolved the access of electron temperature fluctuations in small scale turbulence still has to be improved. Further comparisons are done in ELMy H-mode with combined ball-pen probe/floating potential measurements which can deliver electron temperatures with 25 μ s time resolution at reduced spatial resolution compared to pin probes. During ELMs the electron temperatures derived from the ball-pen probe and fast swept single probes agreed (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) more...

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) more...

Edge localised modes (ELMs) are repetitive instabilities that occur in the outer region of tokamak plasmas. In this work, for the first time, we present image sequences of the temporal evolution of the observed filamentary structures during the ELM events. more...

The objective of the study was to assess the extent and severity of heavy metal contamination of arable soils of the Damascus Ghouta, an area with intensive agricultural production. We examined the present degree and spatial distribution of heavy metal concentrations in 51 soil profiles and in 22 topsoil samples in the Damascus Ghouta. The soils were digested with aqua regia for heavy metal analysis. Pb, Cu and Zn concentrations in the topsoils exhibited anthropogenic increased values. The major sources for the heavy metal contamination in Damascus city are most possibly emissions from vehicles. These emissions transported by air and sewage water together with household and industrial sewage effluents have been considered to be responsible for the increased heavy metal concentrations found in the soils of the central Barada area. However, the values were in most cases below tolerable values of soil for agricultural use. Cr concentrations up to 1800 mg kg−1 were found near a tannery industrial estate. Concerning the health risk of the population bioavailability and mobility of heavy metals seems to be of minor importance, based on the soil properties found in the study area. However, direct ingestion of soil, e.g., by children and inhalation of dust may contribute largely to the accumulation of heavy metal in human and livestock. more...

Pellet injection was investigated for its fuelling capability to high densities in ELMy H mode discharges at JET. Applying the high field side launch system, optimized refuelling scenarios were developed on the basis of conventional discharge configurations withIp= 2.5 MA,Bt= 2.4 T, averaged triangularity ⟨δ⟩≈0.34 and mainly neutral beam heating at a level of approximately 17 MW. The accessible operational range was extended with respect to gas puff refuelling by the use of pellet injection. For example, H mode conditions could be maintained at densities beyond the Greenwald level. Plasma energy confinement was observed to become density independent at high densities. Deep pellet particle deposition made possible the uncoupling of edge and core density, allowing more peaked density profiles. When confinement deterioration due to pellet triggered MHD activity or parasitic pellet borne gas was avoided in appropriate pulse schedules, an enhanced particle inventory was achieved while maintaining the plasma pressure profile. In a technical assessment it was found that there is still room for further enhancement of the injection scenario by improved adaptation to high density plasma operation. more...

The ablated material of a frozen hydrogen isotope pellet which is injected into a hot tokamak plasma forms a high β plasmoid. This diamagnetic plasmoid is accelerated to the magnetic low field side of the torus. The high β plasmoid drift was directly observed by an optical diagnostic with high space and time resolution. Spectroscopic measurements of the emitted light allowed the density and temperature of the ablation cloud, and for the first time also of the drifting plasmoids, to be determined. The experiments give a new insight into the dynamics of the formation of striations during the pellet ablation; these striations cause the separation of the ablated material into a sequence of separated, drifting plasmoids. The influence of the drift on the mass deposition profile for high field side pellet injection is discussed. The plasmoid dynamics even influences the radial pellet motion, most probably owing to a rocket effect. The physical principles of the high β plasmoid drift are discussed and compared with the experimental observations. more...

For high density H modes with constant gas puff on ASDEX Upgrade a slow evolution of the density profile is observed with a time constant much larger than τE. While the edge density remains constant the central density increases as does the stored energy until sawteeth are lost and impurity influx sets in. This peaking process is only observed with NBI heating. Substituting half of the heating by central ICRH leads to completely flat profiles even though half of the original NBI particle fuelling remains. This behaviour, as well as the slow timescale of the peaking process with pure NBI heating, is successfully modelled with a pinch of the order of the neoclassical Ware pinch and a proportionality between the particle diffusion coefficient D and the heat conductivity χ. Such an assumption links D to the heat flux profile qheat, since the temperature profile is observed to be stiff. Such a model implies flat density profiles for a centrally heated fusion reactor. more...

Limited available pellet velocities have so far restricted the refuelling performance of efficient launch schemes from the tokamak magnetic high field side (HFS). Although pellet injection during H mode has resulted in more peaked density profiles and enhanced performance with respect to gas puff refuelling, prompt particle and energy losses caused by pellet induced ELM bursts have still limited the extension of the operational area. Now, the preliminary version of a new optimized pellet injection set-up at ASDEX Upgrade allows for significantly higher injection speeds when launching pellets from the magnetic HFS. Intact pellets with velocities up to vP = 560 m/s were successfully injected instead of the vP = 240 m/s available with the previous set-up. The velocity increase results in a deeper pellet penetration and seems to follow the vP1/3 scaling derived from a multimachine study using conventional pellet launch from the torus outside. The inward shift of the pellet particle deposition profile with respect to the penetration depths turned out to be approximately the same for both launch velocities. The respectively achieved deeper particle deposition inside the plasma column reduced the particle and energy loss rates during the immediate post-pellet phase. Thus, further enhancement of tokamak operation in the high density regime seems feasible by means of high speed pellets launched from the torus inner side. more...

Migration of impurities in tokamaks has been studied with the help of tracer-injection (13C and 15N) experiments in JET and ASDEX Upgrade since 2001. We have identified a common pattern for the migrating particles: SOL flows drive impurities from the low-field side towards the high-field side of the vessel. Migration is also sensitive to the density and magnetic configuration of the plasma, and strong local variations in the resulting deposition patterns require 3D treatment of the migration process. Moreover, re-erosion of the deposited particles has to be taken into account to properly describe the migration process during steady-state operations of the reactor. more...

Nous montrons, par une etude experimentale utilisant la velocimetrie laser-Doppler, que l'instabilite de l'etat de repos dans le probleme de la convection mixte (c'est a dire libre et forcee) ne se compare pas avec la courbe theorique correspondant a l'instabilite neutre, mais bien a celle de l'instabilite convective. Des lors nous mesurons l'amplitude de la vitesse dans les rouleaux thermoconvectifs en fonction de la direction de l'ecoulement et nous comparons avec les valeurs predites d'une equation d'amplitude, decrivant une dynamique idealisee bidimensionelle. more...

The ASDEX Upgrade programme is directed towards physics input to critical elements of the ITER design and the preparation of ITER operation, as well as addressing physics issues for a future DEMO design. After the finalization of the tungsten coating of the plasma facing components, the re-availability of all flywheel-generators allowed high-power operation with up to 20 MW heating power at I p up to 1.2 MA. Implementation of alternative ECRH schemes (140 GHz O2- and X3-mode) facilitated central heating above n e = 1.2 × 1020 m−3 and low q 95 operation at B t = 1.8 T. Central O2-mode heating was successfully used in high P/R discharges with 20 MW total heating power and divertor load control with nitrogen seeding. Improved energy confinement is obtained with nitrogen seeding both for type-I and type-III ELMy conditions. The main contributor is increased plasma temperature, no significant changes in the density profile have been observed. This behaviour may be explained by higher pedestal temperatures caused by ion dilution in combination with a pressure limited pedestal and hollow nitrogen profiles. Core particle transport simulations with gyrokinetic calculations have been benchmarked by dedicated discharges using variations of the ECRH deposition location. The reaction of normalized electron density gradients to variations of temperature gradients and the T e/T i ratio could be well reproduced. Doppler reflectometry studies at the L–H transition allowed the disentanglement of the interplay between the oscillatory geodesic acoustic modes, turbulent fluctuations and the mean equilibrium E × B flow in the edge negative E r well region just inside the separatrix. Improved pedestal diagnostics revealed also a refined picture of the pedestal transport in the fully developed H-mode type-I ELM cycle. Impurity ion transport turned out to be neoclassical in between ELMs. Electron and energy transport remain anomalous, but exhibit different recovery time scales after an ELM. After recovery of the pre-ELM profiles, strong fluctuations develop in the gradients of n e and T e. The occurrence of the next ELM cannot be explained by the local current diffusion time scale, since this turns out to be too short. Fast ion losses induced by shear Alfvén eigenmodes have been investigated by time-resolved energy and pitch angle measurements. This allowed the separation of the convective and diffusive loss mechanisms. more...

For ASDEX Upgrade (AUG) a new probe head was developed for simultaneous measurements of electric and magnetic fluctuations in the edge plasma region. The probe head consists of a cylindrical graphite case. On the front side six graphite pins are mounted. With this arrangement the poloidal and radial electric field components, the ion saturation current and the current-voltage characteristic can be registered simultaneously. Inside the graphite case a magnetic sensor is mounted by which the three components of magnetic field fluctuations are measured. During the AUG discharges the probe head is inserted up to three times for 100 ms each by the midplane manipulator into the scrape-off layer (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) more...

Experimental investigations of the plasma potential and electric field were performed for ELMy H-mode plasmas in the vicinity of the limiter shadow of ASDEX Upgrade. A fast reciprocating probe with a probe head containing four ball-pen probes (BPPs) [J. Adamek et al., Czech. J. Phys. 54 (2004) C95 – C99.] was used on the midplane manipulator. Different gradients of the plasma potential were observed during ELMs and in between them. The temporal resolution of the direct plasma potential measurements with BPP was determined by using power-spectra analysis. more...

A new divertor configuration (DIV-IIb) has been implemented in ASDEX Upgrade. In order to accommodate a large variety of plasma shapes with bottom triangularities (δbot) up to 0.48, the outer strikepoint region was modified and the roof baffle was lowered and diminished at its outer part in comparison with the previous divertor (DIV-II). The inner part of the divertor strikepoint module remains unchanged, but a smooth transition to the central column is provided at the divertor entrance to minimize local hydrogen recycling. An increase in power density is observed due to geometrical reasons at the outer target, whereas the divertor radiation for similar configurations and discharge conditions is unchanged. The pumping characteristics for D and He are almost retained, suggesting a large influence of the inner divertor leg, the configuration of which remains as before. Detachment in L-mode discharges fits well into a scaling deduced from JET data and earlier ASDEX Upgrade data. A significant reduction (20%) of the L–H threshold is observed compared with DIV-II. Its density dependence is weaker than in the previous DIV-II configuration and there are hints for an influence of triangularity on power threshold. Finally, clear evidence for a parasitic plasma below the divertor roof baffle is found. more...

Following the discovery of marked heaves in the molassic marls of Pfaendertunnel in Vorarlberg, Austria, a triaxial swelling-pressure measuring device was used for the first time in assessing expansion stresses. Measurements were made on standard cubes of a side length of 3 cm, the resulting stresses being recorded via a measurement intensifier and evaluated by EDP. Numerous swelling-pressure measurements have been carried out on pelitic rocks of different composition over the past years. Mineralogical composition, grain size distribution and Atterberg values were established simultaneously. The results obtained indicated varying degrees of interdependence. It was noticed that specific mineralogical and geotechnical factors could be correlated in different ways with the swelling pressure established. The time element in the formation of expansion stresses also reflected previous loads to which the rock had been subjected in its geological past. Artificially produced rock cubes made of homogenized sample material were investigated too in order to permit the determination of swelling pressure with sediments not suitable for the production of standard cubes. The expansion stresses obtained by this method were all low ones. From these investigations it has proved possible, in the absence of actual test results, to assess the potential swelling of rocks from a consideration of their mineralogical and geotechnical parameters. more...

Summary On studying 182 papillary neo plasms of the thyroid, 32 nonenca psulated lesions were found to be occult papillary carcinomas (maximum diameter 1.5 cm); out of these 32 patients 18 cases of cervical lymph node metastases were observed. Histologically, 4 circumscribed microcarcinomas, 3 partially encapsulated carcinomas, and 25 occult sclerosing carcinomas were distinguished. The mean diameter of the 4 circumscribed tumours as compared to that of the remaining 28 lesions proved to be statistically significantly smaller, but no significant differences could be observed regarding the rate of lymph node metastasis. One occult sclerosing carcinoma showed a morphologic pattern different from the remaining cases — namely that it had an exclusively solid appearance in the primary lesion and also in its lymph nodes metastases. The follicle cell origin of this lesion was established immunohistochemically by patchy thyroglobulin synthesis. The excellent prognosis of the occult category of papillary thyroid carcinoma was confirmed by a follow-up (mean 7.7 years, range 1.1 to 16.3 years), in which only 2 instances of eradicable recurrent lymph node metastases within the group of occult sclerosing carcinomas were recorded. more...

Strong isotopic fractionation between234U and238U has been noted in deep oil-well brines. The waters are stratigraphically and structurally isolated from fresh-water inflow and have remained stagnant for more than five half-lifes of234U. Excess234U is explained by the234Th alpha-recoil nucleus event. more...

The isotopic composition of krypton extracted from six different selenium ores gives clear evidence for the double beta-decay of 82 Se. The preliminary half-life of 82 Se, calculated from one sample, is 1.4 × 10 20 y with an error of about 20%. more...

Cellulose degradation by several white rot fungi was investigated. In most fungi cellulase production was stimulated by lignin-related phenolics. Detailed investigation of Tremetes versicolor showed that this stimulation was not directly effected by phenols but was due to an indirect induction. The phenol was oxidized by laccase to quinone. The quinone was then reduced by the enzyme cellobiose: quinone-oxidoreductase while cellobiono-lactone was formed from cellobiose. The cellobiono-lactone was responsible for the increased cellulase production in submerged cultures with cellulose as the sole carbon source. more...

In a previous paper /l/ it has been pointed out that electron energy loss spectroscopy in the infrared spectral region is a very sensitive tool for the study of structure and composition of thin films. Here as a further example the energy loss study of amorphous silicon films is presented. In the case of amorphous semiconductors where most of the optical and electrical properties are still strongly influenced by impurities an analytical test is substantial.Silicon films have been investigated which have been prepared by different methods and under different conditions: by evaporation, by decomposition of silane (SiH4) in a rf glow discharge and by sputtering. The influence of the substrate temperature has been studied for films produced by silane decomposition.Fig. 1 shows a typical spectrum of amorphous silicon prepared by the glow discharge method obtained by 30 keV electrons with a resolution of 3 to 4 meV. more...