A multichannel magnetic probe system for analysing magnetic fluctuations in helical axis plasmas

The need to understand the structure of magnetic fluctuations in H-1NF heliac [S. Hamberger et al., Fusion Technol. 17, 123 (1990)] plasmas has motivated the installation of a sixteen former, tri-axis helical magnetic probe Mirnov array (HMA). The new array complements two existing poloidal Mirnov arrays by providing polarisation information, higher frequency response, and improved toroidal resolution. The helical placement is ideal for helical axis plasmas because it positions the array as close as possible to the plasma in regions of varying degrees of favourable curvature in the magnetohydrodynamic sense, but almost constant magnetic angle. This makes phase variation with probe position near linear, greatly simplifying the analysis of the data. Several of the issues involved in the design, installation, data analysis, and calibration of this unique array are presented including probe coil design, frequency response measurements, mode number identification, orientation calculations, and mapping probe coil positions to magnetic coordinates. Details of specially designed digitally programmable pre-amplifiers, which allow gains and filters to be changed as part of the data acquisition initialisation sequence and stored with the probe signals, are also presented. The low shear heliac geometry [R. Jiménez-Gómez et al., Nucl. Fusion 51, 033001 (2011)], flexibility of the H-1NF heliac, and wealth of information provided by the HMA create a unique opportunity for detailed study of Alfvén eigenmodes, which could be a serious issue for future fusion reactors.This work was supported by the Education Investment Fund under the Super Science Initiative of the Australian Government. S.R.H. wishes to thank AINSE Ltd. for providing financial assistance to enable this work on H-1NF to be conducted

Neoclassical transport for Uragan-2M in the 1/ν regime

The 1/ν neoclassical transport (effective ripple, εeff) is studied for the torsatron Uragan-2M (see in [1]. For stellarators where the finite plasma pressure causes a weak influence on the equilibrium εeff can be computed using field line tracing code [2] in real space coordinates. Also, an optimizing procedure is carried out using the code [3] for optimizing stellarators with fixed coil design. Besides, possibilities of improving the neoclassical transport by changing the resulting vertical magnetic field are considered.Вивчено неокласичний перенос в режимі 1/ν («effective ripple», εeff) для торсатрону Ураган-2M [1]. Для стелараторів, де вплив кінцевого тиску плазми на рівновагу являється слабким , εeff може бути розраховано з застосуванням коду [2], що використовує інтегрування вздовж магнітних силових ліній в реальних просторових координатах. Застосовано також оптимізаційну процедуру, яка використовує код [3] для оптимізації стелараторів з фіксованими котушками. Крім того, розглянуто можливості зниження коефіцієнтів неокласичного переносу шляхом змінювання результуючого вертикального магнітного поля.Изучен неоклассический перенос в режиме 1/ν («effective ripple», εeff) для торсатрона Ураган-2M [1]. Для стеллараторов, где конечное давление плазмы оказывает слабое влияние на равновесие, εeff может быть рассчитан с применением кода [2], использующего интегрирование вдоль магнитных силовых линий в реальных пространственных координатах. Применена также оптимизационная процедура, использующая код [3] для оптимизации стеллараторов с фиксированными катушками. Рассмотрены также возможности снижения коэффициентов неоклассического переноса путем изменения результирующего вертикального магнитного поля

Influence of magnetic configuration on edge turbulence and transport in the H-1 Heliac

The role of the rotational transform (ι) profile on fluctuations and transport is investigated in the H-1 Heliac by means of dynamic (i.e. changing during a shot) and static (fixed during a shot) scans of rotational transform through a range of values where the electron density drops markedly and which correspond to having the point of ℓ located near r/a = 0.75 in a region of magnetic well (such that the surface averaged magnetic field strength increases with radius). The gap is near the ℓ = 4/3 resonance, but as the resonance is not in the plasma for more than half the gap it is not clear that this is relevant. Although this drop is clearly driven by the variation of helical current, under particular circumstances, similar density changes occur spontaneously. Plasma currents are measured throughout the scan and are found to slightly affect the rotational transform profile, and reverse about the configuration of minimum confinement, while induced currents through a toroidal loop voltage in the dynamical scans are not found to be significant. The confinement and fluctuation properties are studied by means of 2D movable Langmuir probes. Large near edge-localised dithering quasi-coherent fluctuations at ∼ 6 kHz develop in a strong density gradient region with low magnetic shear as ι is scanned up to a point where the density collapses in the outer region. This dithering corresponds to an m = 3 mode comprising of standing and propagating components. The net and fluctuation-induced transport components are measured near the plasma edge in a similar discharge, and it is found that fluctuation-induced transport driven by these low frequency coherent modes dominates the particle balance during the low density phase but is only a small component of the net flux when the density is higher

Influence of magnetic configuration on edge turbulence and transport in the H-1 Heliac

\u3cp\u3eThe role of the rotational transform (ι) profile on fluctuations and transport is investigated in the H-1 Heliac by means of dynamic (i.e. changing during a shot) and static (fixed during a shot) scans of rotational transform through a range of values where the electron density drops markedly and which correspond to having the point of ℓ located near r/a = 0.75 in a region of magnetic well (such that the surface averaged magnetic field strength increases with radius). The gap is near the ℓ = 4/3 resonance, but as the resonance is not in the plasma for more than half the gap it is not clear that this is relevant. Although this drop is clearly driven by the variation of helical current, under particular circumstances, similar density changes occur spontaneously. Plasma currents are measured throughout the scan and are found to slightly affect the rotational transform profile, and reverse about the configuration of minimum confinement, while induced currents through a toroidal loop voltage in the dynamical scans are not found to be significant. The confinement and fluctuation properties are studied by means of 2D movable Langmuir probes. Large near edge-localised dithering quasi-coherent fluctuations at ∼ 6 kHz develop in a strong density gradient region with low magnetic shear as ι is scanned up to a point where the density collapses in the outer region. This dithering corresponds to an m = 3 mode comprising of standing and propagating components. The net and fluctuation-induced transport components are measured near the plasma edge in a similar discharge, and it is found that fluctuation-induced transport driven by these low frequency coherent modes dominates the particle balance during the low density phase but is only a small component of the net flux when the density is higher.\u3c/p\u3

Solar unterstuetzte Nahwaermeversorgung mit und ohne Langzeit-Waermespeicher (September 1994 bis Oktober 1998)

Within the framework of this project the first three pilot plants for solar-assisted short-distance heat supply with long-term heat storage systems were built and started operation in Friedrichshafen, Hamburg and Neckarsulm. With these plants it could be demonstrated that solar-assisted short-distance heat supply with long-term storage systems comes up to the mark and cuts down energy consumption and related emissions by more than 50 % compared to conventional systems and concepts of heat supply in new residential districts using fossile energy sources. The first years' operating results are within the range of expectations. A measuring concept was developed for the pilot plants which permits scientific measurements to be carried out on systems for solar-assisted short-distance heat supply with long-term heat storage. The measuring data are used to monitor the plants' thermodynamic performance and can help designing and verifying planning tools. With a view to the transfer of knowledge acquired by the research project and its propagation in practice, a BINE information package entitled 'Solar short-distance heat - a manual for practitioners' was compiled. The knowledge gained through this research project has essentially contributed to the further development of large solar heat supplies and long-term thermal energy storage techniques. (orig.)Im Rahmen dieses Forschungsvorhabens wurden unter anderem die ersten drei Pilotanlagen zur solar unterstuetzten Nahwaermeversorgung mit Langzeit-Waermespeicher in Friedrichshafen, Hamburg und Neckarsulm gebaut und in Betrieb genommen. Mit diesen Anlagen konnte demonstriert werden, dass eine solar unterstuetzte Nahwaermeversorgung mit Langzeit-Waermespeicher die in sie gesetzten Erwartungen erfuellt, und, im Vergleich zu einer konventionellen Bauweise und Waermeversorgung der Neubaugebiete, ueber 50% der sonst notwendigen fossilen Energien und der damit verbundenen Emissionen einspart. Die Betriebsergebnisse der ersten Jahre liegen im Rahmen der Erwartungen. Fuer die Pilotanlagen wurde ein Messkonzept entwickelt, mit dem solar unterstuetzte Nahwaermeanlagen mit Langzeit-Waermespeicher wissenschaftlich vermessen werden koennen. Anhand der Messdaten wurde und wird das thermodynamische Verhalten der Anlagen ueberwacht, ausserdem koennen mit ihrer Hilfe Planungswerkzeuge entwickelt und ueberprueft werden. Zum Transfer des durch das Forschungsvorhaben erarbeiteten Wissens und zu dessen Verbreitung in der Praxis wurde ein BINE-Informationspaket 'Solare Nahwaerme - ein Leitfaden fuer die Praxis' geschrieben. Das Forschungsvorhaben hat durch die gewonnenen Erkenntnisse massgeblich zur Weiterentwicklung von solaren Grossanlagen und von Techniken zur Langzeit-Waermespeicherung beigetragen. (orig.)SIGLEAvailable from TIB Hannover: F99B1050+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman