| 1. |
- Demidov, V. I., et al.
(författare)
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The analysis of probe I-V characteristics in a magnetized low-temperature plasma
- 2001
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Ingår i: Contributions to Plasma Physics. - 0863-1042 .- 1521-3986. ; 41:5, s. 443-448
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Tidskriftsartikel (refereegranskat)abstract
- The validity of probe theories based on the classical electron transport to probes in low-temperature magnetized plasma of the toroidal device `Blaamann has been demonstrated. The analysis was carried out for the conditions when global transport of charged particles in the device is anomalous, namely for magnetic field up to 0.3 T and pressure range 0.1 - 1 Pa. It was shown also that for the magnetic field larger than 0.1 T probes longer than 15 mm provide electron saturation current practically independent of probe potential, hence more accurate measurements of the plasma parameters. The experiments have revealed that application of long probes oriented parallel to the magnetic field may cause an anomaly of the I-V characteristics in the sense that a local increase of the electron current appears near the plasma potential.
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| 2. |
- Ratynskaia, Svetlana V., et al.
(författare)
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Measurements of plasma potential and electron temperature fluctuation in a low-temperature magnetized plasma
- 2001
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Ingår i: Contributions to Plasma Physics. - 0863-1042 .- 1521-3986. ; 41:5, s. 449-454
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of fluctuations of plasma potential and electron temperature in a toroidal magnetized plasma is carried out by applying a cylindrical probe with insulating end plugs oriented parallel to the B-field in conjunction with another cylindrical probe oriented perpendicularly. Coherency and cross-phase between (V) over tilde (f) and (T) over tilde (e) are estimated, and typically have values close to 0.6 and pi respectively. Power-law spectra are found for frequencies well above the poloidal rotation frequency with spectral index typically around 4.0 for (V) over tilde (f) and around 2.5 for (T) over tilde (e). The density gradient is above the threshold for flute interchange instability, and the results are consistent with theory and global numerical simulations of this plasma.
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| 3. |
- Antoni, V., et al.
(författare)
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Turbulence and anomalous transport in magnetized plasmas : Hints from the reversed field pinch configuration
- 2004
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 44:06-maj, s. 458-464
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Tidskriftsartikel (refereegranskat)abstract
- The properties of plasma turbulence in the outer region of the Reversed Field Pinch experiments RFX and EXTRAP-T2R are reviewed. The statistical properties of fluctuations in the range of scales relevant for transport are presented. The observation of coherent structures emerging from the background turbulence and their interpretation in terms of vortices is reported. The interplay between these structures and the mean ExB flow of the plasma is demonstrated with emphasis to the action on the preferential rotation direction. The effect on the particle transport induced by the background turbulence and by the structures is discussed. Finally the methods tested to control turbulence and to mitigate the related transport are illustrated and discussed.
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| 4. |
- Barankova, Hana, et al.
(författare)
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Reactive process and hysteresis effect in magnetron with magnetized hollow cathode enhanced target
- 2020
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Ingår i: Contributions to Plasma Physics. - : WILEY-V C H VERLAG GMBH. - 0863-1042 .- 1521-3986. ; 60:9
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Tidskriftsartikel (refereegranskat)abstract
- The hysteresis effect in the reactive process was investigated in the magnetron with a magnetized hollow cathode enhanced target (HoCET) in which the target is coupled with the hollow cathode magnetized by the magnetic field of the magnetron. The process, where both the magnetron and hollow cathode plasmas are combined, is compared to the magnetron sputtering. The hysteresis curve in the magnetized HoCET magnetron, recording the titanium emission intensity versus varying content of nitrogen in the gas mixture exhibits a local maximum on the increasing part of the curve. The hysteresis curve is shifted to lower contents of nitrogen than the hysteresis curve for the magnetron. It is concluded that more efficient utilization of the reactive gas takes place in this device.
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| 5. |
- Borodkina, I., et al.
(författare)
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An Analytical Expression for the Electric Field and Particle Tracing in Modelling of Be Erosion Experiments at the JET ITER-like Wall
- 2016
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Ingår i: Contributions to Plasma Physics. - : WILEY-V C H VERLAG GMBH. - 0863-1042 .- 1521-3986. ; 56:6-8, s. 640-645
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Tidskriftsartikel (refereegranskat)abstract
- A new analytical approximation for the electric potential profile in the presence of an oblique magnetic field and the analytical solution for the particle motion just before the impact with a plasma-facing surface are presented. These approximations are in good agreement with fluid solutions and the corresponding PIC simulations. These expressions were applied to provide effective physical erosion yields for Be, which have in a second step been used in ERO code simulations of spectroscopy at Be limiters of the JET ITER-like wall. These new analytical expressions lead to an increase of the effective physical sputtering yields of Be by deuteron impact up to 30% in comparison with earlier pure numerical simulations. (
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| 6. |
- Brodin, Gert, et al.
(författare)
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Wave Generation in a Warm Magnetized Multi-Component Plasma
- 2014
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 54:7, s. 623-625
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Tidskriftsartikel (refereegranskat)abstract
- The resonant interaction between three waves propagating perpendicularly to an external magnetic field in a plasma is considered. We present the explicit expressions for the three wave coupling coefficients of a warm multi-component plasma. The results of previous work on the generation of THz radiation by laser plasma interaction are significantly improved. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 7. |
- Drake, James R., et al.
(författare)
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Experimental studies of MHD dynamics in a RFP magnetically confined plasma
- 2004
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986. ; 44:06-maj, s. 503-507
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Tidskriftsartikel (refereegranskat)abstract
- Studies of non-linear dynamics of MHD tearing modes in the EXTRAP reversed-field pinch experiments [1] have demonstrated such phenomena as mode rotation, phase-locking and wall locking.
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| 8. |
- Hoelzl, M., et al.
(författare)
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Insights into type-I edge localized modes and edge localized mode control from JOREK non-linear magneto-hydrodynamic simulations
- 2018
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Ingår i: Contributions to Plasma Physics. - : Wiley-VCH Verlagsgesellschaft. - 0863-1042 .- 1521-3986. ; 58:6-8, s. 518-528
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Tidskriftsartikel (refereegranskat)abstract
- Edge localized modes (ELMs) are repetitive instabilities driven by the large pressure gradients and current densities in the edge of H-mode plasmas. Type-I ELMs lead to a fast collapse of the H-mode pedestal within several hundred microseconds to a few milliseconds. Localized transient heat fluxes to divertor targets are expected to exceed tolerable limits for ITER, requiring advanced insights into ELM physics and applicable mitigation methods. This paper describes how non-linear magneto-hydrodynamic (MHD) simulations can contribute to this effort. The JOREK code is introduced, which allows the study of large-scale plasma instabilities in tokamak X-point plasmas covering the main plasma, the scrape-off layer, and the divertor region with its finite element grid. We review key physics relevant for type-I ELMs and show to what extent JOREK simulations agree with experiments and help reveal the underlying mechanisms. Simulations and experimental findings are compared in many respects for type-I ELMs in ASDEX Upgrade. The role of plasma flows and non-linear mode coupling for the spatial and temporal structure of ELMs is emphasized, and the loss mechanisms are discussed. An overview of recent ELM-related research using JOREK is given, including ELM crashes, ELM-free regimes, ELM pacing by pellets and magnetic kicks, and mitigation or suppression by resonant magnetic perturbation coils (RMPs). Simulations of ELMs and ELM control methods agree in many respects with experimental observations from various tokamak experiments. On this basis, predictive simulations become more and more feasible. A brief outlook is given, showing the main priorities for further research in the field of ELM physics and further developments necessary.
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| 9. |
- Ivanova-Stanik, I., et al.
(författare)
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COREDIV and SOLPS Numerical Simulations of the Nitrogen Seeded JET ILW L-mode Discharges
- 2016
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Ingår i: Contributions to Plasma Physics. - : WILEY-V C H VERLAG GMBH. - 0863-1042 .- 1521-3986. ; 56:6-8, s. 760-765
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present the comparison of simulations with the numerical codes COREDIV and SOLPS5.0 for JET L-mode discharges with ITER like wall (ILW). The simulations have been performed for L-mode shots with and without nitrogen seeding (#82291 - 9) which are characterised by relatively low auxiliary heating power (P-NBI = 1.1 MW) and low electron density (n(e) = 2.35 x 10(19) m(-3)). Comparisons are made to the experimental measurements (e.g. radiation levels, plasma profiles) and the differences between the results from the two codes (e.g. temperature and density profiles at the outer divertor plate) are shown and discussed.
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| 10. |
- Joost, J.-P., et al.
(författare)
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Löwdin's symmetry dilemma within Green functions theory for the one-dimensional Hubbard model
- 2021
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Ingår i: Contributions to Plasma Physics. - : Wiley. - 0863-1042 .- 1521-3986.
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Tidskriftsartikel (refereegranskat)abstract
- The energy gap of correlated Hubbard clusters is well studied for one-dimensional systems using analytical methods and density-matrix-renormalization-group (DMRG) simulations. Beyond 1D, however, exact results are available only for small systems by quantum Monte Carlo. For this reason and, due to the problems of DMRG in simulating 2D and 3D systems, alternative methods such as Green functions combined with many-body approximations (GFMBA), that do not have this restriction, are highly important. However, it has remained open whether the approximate character of GFMBA simulations prevents the computation of the Hubbard gap. Here we present new GFMBA results that demonstrate that GFMBA simulations are capable of producing reliable data for the gap which agrees well with the DMRG benchmarks in 1D. An interesting observation is that the accuracy of the gap can be significantly increased when the simulations give up certain symmetry restriction of the exact system, such as spin symmetry and spatial homogeneity. This is seen as manifestation and generalization of the “symmetry dilemma” introduced by Löwdin for Hartree–Fock wave function calculations.
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