Atomic Data and Databases on the Internet: Entering 1996
In this report the current situation with availability and management of atomic data on the Internet is reviewed.
atom-ph↗
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Results for “plasm-ph”
Search indexed arXiv papers on artificial intelligence, large language models, computer vision and robotics. Read source abstracts and follow links to arXiv.
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High energy proton acceleration in dissolving plasma clots
We consider the acceleration of particles (protons) in a plasma clot by an induced field which appears due to the dissolving of the clot. The mechanism of this acceleration is based on a model where the clot consists of double flat moving current layers. It is assumed that the currents flow in opposite directions, while the clot moves in a perpendicular one. It is shown that protons can reach the highest observed energy (of the order of $10^{11}- 10^{12}$GeV), providing that the size of the clot is large enough.
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Stellarator News for January, 1995
The Stellarator News is a bi-monthly newsletter covering the international stellarator community.
plasm-ph↗
Excitation of Large-ktheta Ion-Berstein Waves in Tokamaks
The mode-converted ion-Bernstein wave excited in tokamaks is shown to exhibit certain very interesting behavior, including the attainment of very small poloidal phase velocities, the reversal of poloidal direction, and up-down asymmetries in propagation and damping. Because of these effects, this wave holds promise for channeling {$α$-particle}\ power to ions, something that would make a tokamak fusion reactor far more attractive than presently envisioned.
plasm-ph↗
Stellarator News, Issue 38, March 1995
Stellarator News, an international journal of the stellarator community, is Published by Fusion Energy Division, Oak Ridge National Laboratory, James A. Rome, Editor In the March 1995 issue . . . **** Exerpts from the U.S. Congress Office of Technology Assment report on TPX and Alternate Concepts. **** Edge transport and turbulence studies on U-3M The turbulent-driven particle flow is shown to be comparable with the equilibrium flow at the boundary of the configuration under Alfven-heating conditions in the U-3M torsatron. **** Topological aspects of island divertor studies on W7-AS The structure of the edge plasma in W7-AS, observed with probes, television camera, and H-alpha light agrees at low beta with vacuum field calculations: the low-valued resonances at iotabar=5/m are resolved for m = 8 to 11; external perturbations are not significant at the edge, even for iotabar = 5/10. **** 140-GHz second harmonic O-mode electron cyclotron heating at W7-AS First experimental results are presented of 140-GHz second harmonic O-mode (0.7-MW power) ECRH at a high electron density of 1.8 x 10^20 m^-3 on W7-AS. **** Equilibrium plasma currents in quasi-symmetric stellarators with a helical magnetic axis The plasma currents in quasi-symmetric stellarators are calculated to determe the quasi-symmetric conditions with the help of analytical equations.
plasm-ph↗
Stellarator News, Issue 39, May 1995
Special Issue: New Stellarators New stellarators are being constructed throughout the world as part of a well-coordinated international program. This issue concentrates on the engineering and construction details of Large Helical Device (LHD), Toki, Japan Wendelstein 7-X (W7-X), Greifswald, Germany Helias Stellarator Experiment (HSX), Madison Wisconsin, USA TJ-II, Madrid, Spain
plasm-ph↗
A New Look at the Landau's Theory of Spreading and Damping of Waves in Collisionless Plasmas
The theory of plasma waves and Landau damping in Maxwellian plasmas, Landau's ``rule of pass around poles'' include doubtful statements, particularly related to an artificial ``constructing'' of the dispersion equation, what should allow the possibility of its solution otherwise not existing at all, and the possibility of analytical continuations of corresponding very specific ruptured functions in the one-dimensional Laplace transformation, used by Landau, what is the base of his theory. We represent, as an accessible variant, a more general alternative theory based on a two-dimensional Laplace transformation, leading to an asymptotical in time and space solution as a complicated superposition of coupled damping and {\em non-damping \/} plane waves and oscillations with different dispersion laws for every constituent mode. This theory naturally and very simply explains paradoxes of the phenomenon of plasma echo. We propose for discussion a new ideology of plasma waves (both electron and ion-acoustic waves) qualitatively different from the traditional theory of Landau damping for non-collisional as well as for low-collisional plasmas.
plasm-ph↗
Experimental Divertor Similarity Database Parameters
A set of experimentally-determined dimensionless parameters is proposed for characterizing the regime of divertor operation. The objective is to be able to compare as unambiguously as possible the operation of different divertors and to understand what physical similarities and differences they represent. Examples from Alcator C-Mod are given.
plasm-ph↗
Influence of wave frequency variation on anomalous cyclotron resonance interaction of energetic electrons with finite amplitutude ducted whistler-mode wave
The influence of wave frequency variation on the anomalous cyclotron resonance $ω=ω_{Be}+kv_{\|}$ interaction (ACRI) of energetic electrons with a ducted finite amplitude whistler-mode wave propagating through the so-called transient plasma layer (TPL) in the magnetosphere or in the ionosphere is studied both analytically and numerically. The anomalous cyclotron resonance interaction takes place in the case when the whistler-mode wave amplitude $B_{W}$ is consistent with the gradient of magnetic field $\overrightarrow{B_0}$. The region of phase space occupied by anomalously interacting energetic electrons (synchronous particles) is determined. The efficiencies of both the pitch-angle scattering of resonant electrons and their transverse acceleration are studied and the efficiencies dependence on the magnitude and sign of the wave frequency drift is considered. It has been shown that in the case of ACRI occuring under conditions relevant to VLF-emission in the magnetosphere, the energy and pitch-angle changes of synchronous electrons may be enchanced by a factor $10^2 ÷10^3$ in comparison with ones for nonsynchronous resonant electrons. So the small in density group of synchronous particles may give significant contribution to a whistler-mode wave damping in TPL.
plasm-ph↗
Mode Coupling in Space and Time Varying Anisotropic Absorbing Plasmas
A four dimensional systematic mathematical approach for investigating propagation and coupling of wave modes in a slowly varying (in all space directions and time) anisotropic, absorbing plasma is represented. The formalism is especially useful for energy considerations of the waves. It is applicable to general cases of mode conversion in plasmas with general geometries of space-time and magnetic field configurations. A simple example of how this formalism can be applied to practical cases is given.
plasm-ph↗
Electrostatic Ion Perturbations in Unmagnetized Plasma Shear Flow
The electrostatic perturbations in an unmagnetized, non-isothermal ($T_i{\ll}T_e$) electron-ion plasma shear flow are considered. New physical effects, arising due to the non-normality of linear dynamics, are described. It is shown that the velocity shear induces the extraction of the mean flow energy by the acoustic perturbations (ion-sound waves). The influence of the medium dispersion, rising due to the violation of quasineutrality for perturbations, is examined. It is shown that in the course of the evolution ion-sound waves turn into ion plasma oscillations. New class of nonperiodic, electrostatic perturbations (with vortical motion of ion component), characterized by the intense energy exchange with the mean flow, is also described.
plasm-ph↗
Special-relativistic model flows of viscous fluid
Two, the most simple cases of special-relativistic flows of a viscous, incompressible fluid are considered: plane Couette flow and plane Poiseuille flow. Considering only the regular motion of the fluid we found the distribution of velocity in the fluid (velocity profiles) and the friction force, acting on immovable wall. The results are expressed through simple analytical functions for the Couette flow, while for the Poiseiulle flow they are expressed by higher transcendental functions (Jacobi's elliptic functions).
plasm-ph↗
Power Balance in the ITER Plasma and Divertor
It is planned to use atomic processes to spread out most of the heating power over the first wall and side walls to reduce the heat loads on the plasma facing components in ITER to ~ 50 MW. Calculations indicate that there will be 100 MW in bremstrahlung radiation from the plasma center, 50 MW of radiation from the plasma edge inside the separatrix and 100 MW of radiation from the scrape-off layer and divertor plasma, leaving 50 MW of power to be deposited on the divertor plates. The radiation losses are enhanced by the injection of impurities such as Neon or Argon at acceptably low levels (~0.1 % Argon, etc.)
plasm-ph↗
Adaptive Mesh Refinement for Singular Current Sheets in Incompressible Magnetohydrodynamic Flows
The formation of current sheets in ideal incompressible magnetohydrodynamic flows in two dimensions is studied numerically using the technique of adaptive mesh refinement. The growth of current density is in agreement with simple scaling assumptions. As expected, adaptive mesh refinement shows to be very efficient for studying singular structures compared to non-adaptive treatments.
comp-gas↗
A Review of Recent Developments in Atomic Processes for Divertors and Edge Plasmas
The most promising concepts for power and particle control in tokamaks and other fusion experiments rely upon atomic processes to transfer the power and momentum from the edge plasma to the plasma chamber walls. This places a new emphasis on processes at low temperatures (1-200 eV) and high densities (10^20-10^22 m^-3). The most important atomic processes are impurity and hydrogen radiation, ionization, excitation, recombination, charge exchange, radiation transport, molecular collisions, and elastic scattering of atoms, molecules and ions. Important new developments have occurred in each of these areas. The best available data for these processes and an assessment of their role in plasma wall interactions are summarized, and the major areas where improved data are needed are reviewed.
plasm-ph↗
Analytic Criteria for Power Exhaust in Divertors due to Impurity Radiation
Present divertor concepts for next step experiments such ITER and TPX rely upon impurity and hydrogen radiation to transfer the energy from the edge plasma to the main chamber and divertor chamber walls. The efficiency of these processes depends strongly on the heat flux, the impurity species, and the connection length. Using a database for impurity radiation rates constructed from the ADPAK code package, we have developed criteria for the required impurity fraction, impurity species, connection length and electron temperature and density at the mid-plane. Consistent with previous work, we find that the impurity radiation from coronal equilibrium rates is, in general, not adequate to exhaust the highest expected heating powers in present and future experiments. As suggested by others, we examine the effects of enhancing the radiation rates with charge exchange recombination and impurity recycling, and develop criteria for the minimum neutral fraction and impurity recycling rate that is required to exhaust a specified power. We also use this criteria to find the optimum impurity for divertor power exhaust.
plasm-ph↗
Studies of Plasma Detachment Using a One Dimensional Model for Divertor Operation
To characterize the conditions required to reach advanced divertor regimes, a one-dimensional computational model has been developed based on a coordinate transformation to incorporate two-dimensional effects. This model includes transport of ions, two species each of atoms and molecules, momentum, and ion and electron energy both within and across the flux surfaces. Impurity radiation is calculated using a coronal equilibrium model which includes the effects of charge-exchange recombination. Numerical results indicate that impurity radiation acts to facilitate plasma detachment and enhances the power lost from the divertor channel in escaping neutral atoms by cooling the electrons and suppressing ionization. As divertor particle densities increase, cold and thermal molecules become increasingly important in cooling the plasma, with molecular densities dominating electron and atomic densities under some conditions.
plasm-ph↗
Radiation Rates for Low Z Impurities in Edge Plasmas
The role of impurity radiation in the reduction of heat loads on divertor plates in present experiments such as DIII-D, JET, JT-60, ASDEX, and Alcator C-Mod, and in planned experiments such as ITER and TPX places a new degree of importance on the accuracy of impurity radiation emission rates for electron temperatures below 250 eV for ITER and below 150 eV for present experiments. We have calculated the radiated power loss using a collisional radiative model for Be, B, C, Ne and Ar using a multiple configuration interaction model which includes density dependent effects, as well as a very detailed treatment of the energy levels and meta-stable levels. The "collisional radiative" effects are very important for Be at temperatures below 10 eV. The same effects are present for higher Z impurities, but not as strongly. For some of the lower Z elements, the new rates are about a factor of two lower than those from a widely used, simpler average-ion package (ADPAK) developed for high Z ions and for higher temperatures. Following the approach of Lengyel for the case where electron heat conduction is the dominant mechanism for heat transport along field lines, our analysis indicates that significant enhancements of the radiation losses above collisional radiative model rates due to such effects as rapid recycling and charge exchange recombination will be necessary for impurity radiation to reduce the peak heat loads on divertor plates for high heat flux experiments such as ITER.
plasm-ph↗