Sudden transition to chaos in plasma wave interactions

The coherent three-wave interaction, with linear growth in the higher frequency wave and damping in the two other waves, is reconsidered; for equal dampings, the resulting three-dimensional (3-D) flow of a relative phase and just two amplitudes behaved chaotically, no matter how small the growth of the unstable wave. The general case of different dampings is studied here to test whether, and how, that hard scenario for chaos is preserved in passing from 3-D to four-dimensional flows. It is found that the wave with higher damping is partially slaved to the other damped wave; this retains a feature of the original problem an invariant surface that meets an unstable fixed point, at zero growth rate! that gave rise to the chaotic attractor and determined its structure, and suggests that the sudden transition to chaos should appear in more complex wave interactions

Self-consistent resonance absorption with two layer profile steepening

Resonance absorption of p-polarized light, incident at angle 6 on a flowing, stratified plasma, is analyzed; profile steepening within (i) a layer around the turning point, and (ii) a thinner,embedded sublayer at the critical surface is taken into account self-consistently. The entire steepened region is taken as collisionless and isothermal. The structure of the main layer shows a variety of regimes, depending on how the flow crosses a sonic point. The structure of the sublayer is also determined; it is entirely subsonic (with no wave breaking) for a well-defined,broad parameter range. Density changes across both layer and sublayer, and fractional absorption, are given in terms of [(wavelength)2 Xintensity/temperature], and (temperature/mec2). The flow outside the double structure is also analyzed for particular conditions

Current collection by an active spherical electrode in an unmagnetized plasma

A theoretical model for the steady-state response of anodic contactors that emit a plasma current Ii and collect electrons from a collisionless, unmagnetized plasma is presented. The use of a (kinetic) monoenergetic population for the attracted species, well known in passive probe theory, gives both accuracy and tractability to the theory. The monoenergetic population is proved to behave like an isentropic fluid with radial plus centripetal motion, allowing direct comparisons with ad hoc fluid models. Also, a modification of the original monoenergetic equations permits analysis of contactors operating in orbit-limited conditions. Besides that, the theory predicts that, only for plasma emissions above certain threshold current a presheath/double layer/core structure for the potential is formed (the core mode), while for emissions below that threshold, a plasma contactor behaves exactly as a positive-ion emitter with a presheath/sheath structure (the no-core mode). Ion emitters are studied as a particular case. Emphasis is placed on obtaining dimensionless charts and approximate asymptotic laws of the current-voltage characteristic

Hard transition to chaotic dynamics in Alfven wave fronts

The derivative nonlinear Schrodinger DNLS equation, describing propagation of circularly polarized Alfven waves of finite amplitude in a cold plasma, is truncated to explore the coherent, weakly nonlinear, cubic coupling of three waves near resonance, one wave being linearly unstable and the other waves damped. In a reduced three-wave model equal dampings of daughter waves, three-dimensional flow for two wave amplitudes and one relative phase, no matter how small the growth rate of the unstable wave there exists a parametric domain with the flow exhibiting chaotic relaxation oscillations that are absent for zero growth rate. This hard transition in phase-space behavior occurs for left-hand LH polarized waves, paralleling the known fact that only LH time-harmonic solutions of the DNLS equation are modulationally unstable, with damping less than about unstable wave frequency 2/4 x ion cyclotron frequency. The structural stability of the transition was explored by going into a fully 3-wave model different dampings of daughter waves,four-dimensional flow; both models differ in significant phase-space features but keep common features essential for the transition

Bare-tether sheath and current: comparison of asymptotic theory and kinetic simulations in stationary plasma

Analytical expressions for current to a cylindrical Langmuir probe at rest in unmagnetized plasma are compared with results from both steady-state Vlasov and particle-in-cell simulations. Probe bias potentials that are much greater than plasma temperature (assumed equal for ions and electrons), as of interest for bare conductive tethers, are considered. At a very high bias, both the electric potential and the attracted-species density exhibit complex radial profiles; in particular, the density exhibits a minimum well within the plasma sheath and a maximum closer to the probe. Excellent agreement is found between analytical and numerical results for values of the probe radiusR close to the maximum radius Rmax for orbital-motion-limited (OML) collection at a particular bias in the following number of profile features: the values and positions of density minimum and maximum, position of sheath boundary, and value of a radius characterizing the no-space-charge behavior of a potential near the high-bias probe. Good agreement between the theory and simulations is also found for parametric laws jointly covering the following three characteristic R ranges: sheath radius versus probe radius and bias for Rmax; density minimum versus probe bias for Rmax; and (weakly bias-dependent) current drop below the OML value versus the probe radius for R > Rmax

Low Cost Semi Automated Assembly Unit for Small Size Back Contact Modules and Low Cost Interconnection Approach

AbstractWe present our low cost assembly unit to manufacture back contact solar modules based on the conductive backsheet (CBS) approach. This in house developed apparatus was built to assemble test modules containing one up to four 6 inch back contact solar cells. The system is a retrofit of a commercially available CNC system which is equipped with a cell grabber and a manual dispensing system (by Nordson). The total cost of the setup was roughly 4000 € excluding the dispenser unit. Using this equipment we assembled several small size modules containing one and four Zebra cells, which are low cost 6 inch IBC solar cells developed at ISC Konstanz [1,2]. The contact between copper backsheet and back contact cell of the one cell modules we present here is formed by low temperature solder paste (LTSP). First cell to module (CTM) loss evaluations and reliability results suggest that this material could be a viable alternative to electrically conductive adhesive (ECA) which is currently the most commonly used material for this purpose

Influencia del tratamiento químico con cloroformo/metanol en el comportamiento elástico del pericardio de ternera utilizado en la construcción de bioprótesis cardiacas

Se estudia el comportamiento mecánico del pericardio de ternera utilizado en la construcción de bioprótesis cardiacas cuando se trata químicamente cloroformo/metanol (CM) comparándolo con tratamiento estándar con glutaraldehído.(G). Se ensayan a tracción hasta rotura 40 probetas, veinte con cada tratamiento y de estas el 50% suturadas en su parte central con seda 4/0.La perdida de resistencia media a la rotura de las probetas suturadas fue de alrededor de 6 MPa sin encontrar diferencias entre el tipo de tratamiento utilizado. No obstante en el análisis de las curvas promedio estrés/deformación para valores de estrés a tracción inferiores a 2.5 MPa, apenas encontramos diferencias entre las series suturadas y no suturadas tratadas con cloroformo/metanol anulando parcialmente el efecto deletéreo de la sutura en ese rango de estrés que incluye el estrés estimado de trabajo, de 0.25MPa.El tratamiento con cloroformo/metanol podría, además de retrasar los procesos de calcificación del pericardio, mejorar el comportamiento elástico de las probetas suturadas disminuyendo la interacción con la sutura. Ensayos de fatiga real con este tratamiento químico deberán ser realizados para verificar esta hipótesis.Peer Reviewe

Alfvén wave far field from steady-current tethers

We analyzed he Alfvén waves ignaturele ft behindi n the ionospherbe y orbiting insulatedt etherso peratinga s thrusterso r generatorws ith steadyc urrentsU. sing a recentd escription of tetherr adiationt o determineth e far field, we showt hat, at their leadinge dges,t heA lfv6n wingsh avea n Airy functionc rosswises tructureT. he field amplitudef alls off weakly as the inversec uber oot of the distancea longt he wavef ront.T he fronti tself, whichc arriesa negligible fractiono f the powerr adiateda sA lfven waves,b roadensp roportionallyto the cuber oot of that distanceW. e showt hatc ollisionadl ecayb ecomesim portanat t about1 03k m alongt he front.F or tethersl ongert han about2 km, the top andb ottoms tructures("wings")a re fully disjoint