Fakultät für Physik - Digitale Hochschulschriften der LMU - Teil 03/05

Magnetised plasma permeates the Universe. It is present in stars, accretion discs, galaxies and clusters of galaxies. This dissertation investigates the characteristics of diffuse magnetised plasma in the inter-stellar-medium (ISM) and the intra-cluster-medium (ICM).

To probe turbulence in the ISM and ICM, we develop an estimator for the magnetic tension-force spectrum. It is based on polarised synchrotron emission data in the Faraday-rotation-free frequency regime. The tension force is the dynamically most important magnetic force in subsonic magnetic turbulence.

We consider two magnetic field scenarios: a statistically isotropic field distribution, and a statistically isotropic field upon a small mean field. In the latter case the magnetic power spectrum can also be obtained in addition to the tension-spectrum. The method is exact in the ideal case of a homogeneous cosmic ray electron distribution with a power law energy spectrum with a spectral index p=3, and isotropic magnetic fields. The method is applied to mock observations based on magneto-hydrodynamic simulations as a

prelude to an application to real observations. We confirm the robustness of the estimator by comparing its output to the corresponding quantities directly computed from the simulation.

Furthermore, to investigate the global Galactic field we developed hammurabi. This software tool takes three-dimensional theoretical models for the ISM components and generates mock observations from them. It focuses on the main tracers of our Galactic magnetised plasma such as synchrotron flux, Faraday rotation, dispersion measure and ultra-high-energy-cosmic-ray delflections. Hammurabi therefore permits us to confront models of the Galactic magnetised plasma with a broad range of real observations. We report on a number of works based on this code. In particular, due to simultaneous constraints of rotation measure, polarised and total synchrotron intensity, as well as theoretical predictions on the magnetic field and cosmic-ray electron distribution, the Galactic electron density scale height was suggested to be about twice as large as previously thought. This result obtained with hammurabi was recently confirmed independently by other authors using pulsar dispersion measure data.

Finally, we consider the role of the Galactic kinetic Sunyaev Zeldovich (kSZ) effect as a CMB foreground. We analyse the detectability of the Galactic kSZ effect by means of an optimally matched filter technique applied to a simulation of an ideal observation. We obtain a S/N ratio of 0.1, and demonstrate thereby that the Galactic kSZ effect can safely be ignored as a CMB foreground.

Furthermore, we rule out any significant contamination of the polarised CMB signal by second scattering of galactic kSZ photons.

In dieser Dissertation untersuchen wir die Rolle verallgemeinerter Chern-Simons Terme in vierdimensionalen chiralen Eichtheorien, genauer, wie Quantenanomalien weggehoben werden können. Unter Einbeziehung von verallgemeinerten Chern-Simons Termen und zusätzlichen axionischen Kopplungen ist man in der Lage die Bedingungen, die Abwesenheit von Anomalien garantieren, zu entschärfen. Phänomenologische Modelle, die gerade diese Art von Kopplungen beinhalten, sind seit einiger Zeit Mittelpunkt reger Untersuchungen. Mögliche Realisierungen für entsprechende Modelle sind zum Beispiel durch sich schneidende Branen-Modelle in Orientifoldkompaktifizierungen von Typ II Stringtheorien gegeben. Die Vorhersagen der phänomenologischen Untersuchungen dieser Modelle könnten sogar in naher Zukunft in Kollisionsexperimenten nachgeprüft werden, falls nur die Masse des anomalen U(1)-Eichbosons klein genug ist.

The Tokamak configuration is a promising concept for magnetic confinement fusion. Cross-field

transport in the plasma core leads to a plasma flux across the separatrix into the scrape-off layer,

where it is guided along field lines towards the divertor targets. A return flux of neutral particles

after plasma-wall interaction is directed towards the plasma chamber. Each discharge scenario

is accompanied by a characteristic recycling pattern. The dominant mechanisms of neutralplasma

interaction are ionisation and atom-ion charge exchange. The impact of neutrals on the

particle-, momentum- and energy-balance of the plasma is relevant for the understanding of the

properties of the edge plasma and the state of the divertor plasma. Neutrals may cause energyand

momentum-detachment, a state of reduced power and particle fluxes, at the targets, which

is a prerequisite for acceptable wall loads under reactor conditions. The distribution of neutral

particles in the plasma chamber can be determined by the analysis of line emission. Parameters of

neutrals have been available so far only from localised measurements and it is therefore desired

to extend the observation area.

At the ASDEX Upgrade Tokamak, two cameras are installed to record the Deuterium

Balmer-alpha (D_alpha) emission with high spatial resolution and dynamic range in the divertor and midplane

regions. Two methods for data deconvolution are presented. A simple profile-fit is used to

resolve the radial profile of emission at the low and high field sides for low and medium density

discharges. This emission profile is translated to neutral parameters by comparison to the results

obtained from kinetic modelling of neutral penetration (KN1D). An algorithm for tomographic

reconstruction is applied to image data of the divertor region. In general, radiance data recorded

is blurred due to the impact of diffuse reflection from surfaces of the plasma facing components in

the all-Tungsten machine. Therefore, the tomographic algorithm has been extended by a model

for reflection based on a solid angle resolved measurement.

The sensitivity of the procedures is proven by the accurate analysis of different edge plasma

configurations. Poloidally resolved neutral flux densities at the plasma edge and corresponding

core fuelling rates are presented for the high field side. Underlying estimates of plasma parameters

indicate a drop of static plasma pressure along the magnetic field towards the inner target.

Changes of the poloidal flux density profile during a radial shift of the plasma column, indicate

a correlation of plasma-wall gap and scrape-off layer parameters at the high field side. From the

deconvolution of divertor view data separate emission patterns have been resolved. Besides the

character of emission at the strike zones which can give a hint on the level of detachment, the

occurrence of radiation above the inner target indicates that the distribution of plasma parameters

is probably more complex than expected from simple radial decay lengths.

The experimental emission profiles and inferred neutral parameters display an important

boundary condition for complex 2D edge modelling codes like SOLPS. The comparison of experimental

and code results question the applicability of the standard recipe (concerning code

settings) for arbitrary plasma scenarios. An interface to theory is required to reasonably exploit

the experimental data on neutral penetration.

The essential result of this thesis is a reference frame for the quantitative analysis of video

diagnostics data recorded on a Tokamak plasma, including the impact of reflecting plasma facing

components.

The internal structure of the nucleon is more complicated than expected in a simple quark model. In particular, the portion of the nucleon spin carried by the spins of the quarks is not, as expected, of the order of one, but according to the experimental data much smaller. In this thesis we study the spin structure of the proton in quantum

chromodynamics.

The constituent quark model, based on SU(6), predicts that the spin of the proton should be carried by the quarks, in disagreement with the experiments. It appears strange, that the theoretical model works so well for the magnetic moments of the nucleons, but not for the spin, although the spin and the magnetic moments are closely related to each other. We shall resolve this problem by assuming that the constituent quarks have an internal structure on their own. Thus a constituent quark has a dynamical structure, and we can introduce notions like the quark or gluon distributions inside a constituent quark.

In the light of new experimental data from HERMES, COMPASS, J-Lab, and RHIC-spin, the current status of our knowledge of the spin structure is discussed in the two theoretical frameworks: the naive parton model, and the QCD evolved parton model. QCD a is successful theory, both in perturbative and non-perturbative regions, but the spin of the nucleon still needs to be explained within QCD.