Über den Bewegungsvorgang in einem linearen Plasmabeschleuniger

Es wird der Bewegungsablauf an linearen Plasmabeschleunigern, deren außerer Stromkreis durch das zu beschleunigende Plasma geschlossen wird, anhand vondrei Modellen betrachtet. Die Bewegungsgleichungen der drei Modelle: Free-Particle- Modell, Schneepflug-Modell und Modell mit konstanter Masse wurden mit Hilfe der elektronischen Rechenanlage IBM 1620 numerisch integriert. In Teil II wird der im Modell mit konstanter Masse benötigte Reibungskoeffizient aus der Betrachtung einzelner Wechselwirkungsprozesse des Plasmas mit dem Neutralgas abgeschätzt. In Teil III werden die Bewegungsgleichungen abgeleitet und die numerischen Ergebnisse diskutiert. Aus der Diskussion der Abhängigkeit der dynamischen Größen von den Kreisdaten und der Erörterung von Dimensionierungsfragen ergeben sich einige qualitative Aussagen, die weitgehend von den einzelnen Modellen unabhängig sind, da die Bewegungen mit einigen Einschränkungen für alle drei Modelle sehr ähnlich verlaufen. So wird z.B. eine Beziehung für optimale Ausbeute an Impuls und spezifischem Impuls angegeben. Die graphischen Darstellungen des Bewegungsablaufes befinden sich am Schluß der Arbeit

Toroidal effects on Island formation in a helically perturbed tokamak equilibrium

The characteristics of the ergodic magnetic field at the edge of a tokamak plasma produced by an additional helical field are described usuall in terms of the Fourier components of the perturbing field to lowest order in the aspect ratio $\epsilon$ [1]. Fieldline tracing calculations for the planned Dynamic Ergodic Divertor (DED) at TEXTOR-94 [2], which has an aspect ratio of $\epsilon$ = 0.25 lead to about 30 % smaller values for the island width and the related Chirikov parameter and to quite larger deviations in the neId line diffusion coefficient D$_{FL}$. This effect was found to have a significant dependence on the poloidal location of the perturbation coils.Starting from the expression for the island width in t.erms of the vector potential, given in [1], which is correct to any order in the aspect ratio, we derive an expression, which is in fulagreement with the numerical results. This is achieved by taking into account the full toroidal geometry when replacing the perturbation of the vector potential by the perturbation of the magnetic field

Fluid Targets for Heat Removal in Fusion Reactors

Fluid targets, i.e. liquids or solids moving through the high heat flux zones, may be a way to solve the heat exhaust and erosion problems in fusion reactors. Some of the ideas are not new and are presented in the literature in widely scattered articles. Unfortunately, the discussion is often not detailed enough to judge their applicability. They have e.g. been addressed in the framewerk of the INTOR and ITER studies. This report contains contributions of members of a study group constituted from scientists and engineers of different Institutes of KFA end of 1993. The group met a few times to discuss ideas and problems associated with the use of fluid targets for heat exhaust in fusion reactors. The starting point has been a proposal for a respective program on TEXTOR. The main aim of the group's work has been so far to identify critical questions warranting in depth studies in preparation of a potential experiment in TEXTOR. The treatment of the matter in these contributions is by now means complete and exhaustive but some important conclusions still can be drawn. Reference to literature is made in the individual contributions where appropriate. In addition to these references a number of publications of general interest have been used and are listed in the appendix. The contributions partly consist of summaries in english and copies of figures and viewgraphs in german which are selfexplaining in most cases

Enhanced small scale turbulence oscillations correlated to sawtooth relaxations in the textor tokamak

A periodic enhancement of the microturbulence level by sawtooth relaxations has been detected by CO$_{2}$ laser forward scattering in the TEXTOR tokamak. This feature is reproduced quantitatively by a heat transport code in which the anomalous electron transport coefficient is calculated self consistently following a theoretical model of the saturation of the dissipative trapped electron instability. The code also predicts a strong modulation of the heat whole plasma and a strong "profile consistency" as continuous temperature measurements have interpretation of these results is given. Calculated global plasma parameters, such as the energy confinement time and the loop voltage, are in good agreement with the measured values

Toroidal effects on island formation in a helically perturbed tokamak equilibrium

The characteristics of the ergodic magnetic field at the edge of a tokamakplasma produced by an additional helical field are described usually in terms of the Fourier components of the perturbing field to lowest order in theaspect ratio #epsilon#. Fieldline tracing calculations for the planned dynamic ergodic divertor TEXTOR-94, which has an aspect ratio of#epsilon# = 0.25 lead to about 30% smaller values for the island width and the related Chirikov parameter and to quite larger deviations in the field line diffusion coefficient D_F_L. This effect was found to have a significant dependence on the poloidal location of the perturbation coils. Starting from the expression for the island width in terms of the vector potential, which is correct to any order in the aspect ratio, we derive anexpression, which is in full agreement with the numerical results. This is achieved by taking into account the full toroidal geometry when replacing the perturbation of the vector potential by the perturbation of the magnetic field. (orig.)7 refs.SIGLEAvailable from TIB Hannover: RA 831(3367) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman