Plasma simulations

From potentiometric and spectroscopic studies it is concluded that the main species at neutral pH is a 1 1 tridentate chelate (11) with a log stability constant of ca. — 4. The claim55 that the stability of this species is comparable to that of the Cu(albumin) complex is rather surprising, since for this to occur the involvement of a histidine in the third amino add position is normally required, and furthermore others have concluded that in blood plasma at least the tripeptide is unlikely to compete against other ligands for the available Cu11.56,57 To illustrate the point that such conclusions from blood plasma simulations are only applicable to that medium, Pickart and Thaler58 have shown that in a cell culture medium the tripeptide considerably enhanced Cu uptake into cells and that this was not affected by a 300-fold molar excess of amino adds, including histidine. 

Plasma simulation experiments along with single and simultaneous multiple ion irradiation studies are needed to investigate the possibilities of interactive effects116 ... 

Understanding the dependence of film structure and morphology on system layout and process parameters is a core topic for the further development of ZnO technology. Work is being performed on in situ characterization of deposition processes. Growth processes are simulated using Direct Simulation Monte-Carlo (DSMC) techniques to simulate the gas flow and sputter kinetics simulation and Particle-ln-Cell Monte-Carlo (PICMC) techniques for the plasma simulation [132]. 

Fig. 5.34. (a) High-speed photograph (source Fraunhofer FEP, Dresden) and (b) plasma simulation of an MF magnetron in-line sputter process (source Fraunhofer 1ST, Braunschweig)... 

The resulting set of 10 equations, assuming toroidal symmetry and replacing the radial component of the ion momentum balance equation by an ad hoc diffusions ansatz (likewise the other radial transport coefficients are replaced by ad hoc anomalous expressions) is the basis for most current edge plasma simulation models. These anomalous ad-hoc coefficients are free model parameters. They, and their empirical scalings, can be determined by comparison with experimental plasma profile data, if one can be sure that all other terms in the equations, and in particular the source terms Sm resulting from atomic and molecular processes, are accurately known and implemented. 

For ASDEX Upgrade, detachment is harder to achieve with the presence of vibrationally excited molecules than without. This result is exactly the opposite of what one would have expected without such a detailed bookkeeping of the various competing processes and forces, as it is currently only provided by the edge plasma simulation codes employed here. 

CH4, cd4) + (°) Bands of radicals (CH, CH2,...) near carbon walls, limiters and divertors excitation rates for the visible exist and have been measured in plasma simulators and tokamaks... 

CH,CD + + Bands been measured in plasma simulators at limiters divertors further check of break-up chain advisable include new data origin molecule of CH ne-dependence ... 

OH, OD + Bands not yet well defined in the toka-mak edge bands seen in plasma simulators... 

Fig. 9.3. (a) Erosion yield of Be as function of surface temperature as measured in the plasma simulator PISCES-B [23]. (b) Sputtering yield of Be for Be and D ions as function of surface temperature measured by ion beams [4,22]... 

Fig. 9.10. Flux dependence of the chemical erosion yield for Tmax and an ion energy of 30 eV determined from spectroscopic measurements in different fusion devices and plasma simulators. The solid lines are a fit using Bayesian probability theory and its confidence intervals [58,59]. The dashed line is a prediction from an earlier analytic description [44]...

Recently, it could be demonstrated in the PISCES-B plasma simulator that Be impurity atoms in the eroding plasma can lead to a drastic suppression of chemical erosion already at concentrations as low as 0.15 at% [84],... 

At high ion fluences the chemical erosion yield appears to decrease. This fluence dependence may originate from the development of a pronounced surface topography. Dedicated investigations are needed in plasma simulators where high fluences can be achieved. 

Up until the early 1990s, simulations that solved for the radio frequency (RF) plasma dynamics (so-called glow discharge models) were confined to one spatial dimension (1-D) [36, 113-126]. In addition, most of these simulations did not solve for the transport and reaction of neutrals, i.e., the effect of gas excitation and/or dissociation on the plasma characteristics was not accounted for. This can sometimes be a severe limitation since even minute quantities of excited species can alter the discharge properties [36]. Self-consistent RF plasma simulations which solve for the coupled effects of charged and neutral species transport and chemistry have only been reported within the past several years in 1-D [36, 121, 123], 2-D [97, 100, 127-132] and 3-D [109, 110]. Multidimensional simulations are particularly useful since they can address the important issue of plasma uniformity and the spatiotemporal plasma... 

When dealing with multidimensional geometries and complex chemistries, fullblown self-consisted plasma simulations pose a very challenging task. While brute force simulations (for example ones that solve the complete set of conservation equations for all particles) are feasible, they are also labor and time consuming. Judicious approximations, based on the physics of the problem, can reduce the simulation times dramatically. Examples are the space-time averaging used in the non-local approach [58, 59], or the approximations used to construct rapid plasma simulation tools [59, 101, 148, 152, 153]. 

A key component of particle-based simulation methods involves the coupling of the dynamics of the charge carriers (ions) with the field of forces generated by the external boundary conditions as well as by the internal electrostatic interactions between the components of the system. This self-consistent coupling approach has been successfully employed for more than three decades in plasma simulations. The adjective self-consistent refers to the fact that the forces caused by the electrostatic interactions within the components of the system depend strictly on the spatial configuration of the components and must be updated continuously as the dynamics of the system evolves. 

Another technique, widely used in a different context (kinetic theory, plasma simulation) is the so-called Vortex-in-Cell Method (Hockney and Eastwood 1981, Birdsall and Langdon 1985). In the Vortex-in-Cell Method a two-dimensional computational domain is divided into cells and the vorticity is counted in each cell. The Poisson equation relating the vorticity and the Laplacian of the stream function is subsequently solved on the grid by an FTT algorithm, the velocity... 

Plasma Simulation Code Benchmark 14.9 tflops on 512 nodes (45%)... 

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