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A comprehensive description of methods, suitable for solving the kinetic equation for fast ions and impurity species in tokamak plasmas using Monte Carlo approach, is presented. The described methods include Hamiltonian orbit-following in particle and guiding center phase space, test particle or guiding center solution of the kinetic equation applying stochastic differential equations in the presence of Coulomb collisions, neoclassical tearing modes and Alfv\'en eigenmodes as electromagnetic perturbations relevant to fast ions, together with plasma flow and atomic reactions relevant to impurity studies. Applying the methods, a complete reimplementation of the well-established minority species code ASCOT is carried out as a response both to the increase in computing power during the last twenty years and to the weakly structured growth of the code, which has made implementation of additional models impractical. Also, a benchmark between the previous code and the reimplementation is accomplished, showing good agreement between the codes., Comment: 13 pages, 9 figures, submitted to Computer Physics Communications

A Monte Carlo method for the collisional guiding-center Fokker-Planck kinetic equation is derived to include the effects of background magnetic-field nonuniformity. It is shown that, in the limit of a homogeneous magnetic field, the guiding-center Monte Carlo collision operators reduce to the standard Coulomb operators. The coefficients required for the implementation of the method are also given., 17 pages

The fusion alpha and beam ion with steady-state power loads in all four main operating scenarios of ITER have been evaluated by the ASCOT code. For this purpose, high-fidelity magnetic backgrounds were reconstructed, taking into account even the internal structure of the ferritic inserts and tritium breeding modules (TBM). The beam ions were found to be almost perfectly confined in all scenarios, and only the so-called hybrid scenario featured alpha loads reaching 0.5 MW due to its more triangular plasma. The TBMs were not found to jeopardize the alpha confinement, nor cause any hot spots. Including plasma response did not bring dramatic changes to the load. The ELM control coils (ECC) were simulated in the baseline scenario and found to seriously deteriorate even the beam confinement. However, the edge perturbation in this case is so large that the sources have to be re-evaluated with plasma profiles that take into account the ECC perturbation.

Group-III nitrides in their wurtzite crystal structure are characterized by large spontaneous polarization and significant piezoelectric contributions in heterostructures formed of these materials. Polarization discontinuities in polar heterostructures grown along the 0001 direction result in huge built-in electric fields on the order of megavolt per centimeter. We choose the III-nitride heterostructures as archetypal representatives of polar heterostructures formed of semiconducting or insulating materials and study the behavior of positrons in these structures using first-principles electronic-structure theory supported by positron annihilation experiments for bulk systems. The strong electric fields drive positrons close to interfaces, which is clearly seen in the predicted momentum distributions of annihilating electron-positron pairs as changes relative to the constituent bulk materials. Implications of the effect to positron defect studies of polar heterostructures are addressed. DOI: 10.1103/PhysRevB.82.041307

We use the orbit-following Monte Carlo code ASCOT to calculate the wall power loads in ITER caused by fusion alphas. The simulations are carried out for a realistic 3D magnetic field that includes the effect of both ferritic inserts and the test blanket modules, both causing aberrations in the magnetic field structure, particularly at the edge. In addition to an magnetohydrodynamic (MHD)-quiescent plasma we now also address the power loads in the presence of relevant MHD events: both neoclassical tearing modes (NTMs) and toroidal Alfven eigenmodes (TAEs) are included in the simulation model. In the case of NTMs, the total power load to the wall is found to depend on the perturbation amplitude. Even with the strongest perturbation, however, the power load density stays within the design limit of the ITER wall materials. In the case of TAEs, while the wall power load density stays at the MHD-quiescent level, significant redistribution of alphas inside the plasma was observed. This was also found to affect the alpha heating profile.

This thesis is an attempt to document and explain the manifest changes that have been taking place in Welsh identity since 1979, and the political consequences thereof. It is presupposed that before any autonomist outbursts and other, related political changes take place in a sub-national region such as Wales, some sort of identive change has to occur. This 'identive change' is posited to take place in two stages - identity transformation followed by identity mobilisation. Central chapters deal with this process in two, non-exclusive, dimensions - institutions and individual agents. Alongside institution-building, certain policy areas are deemed to be of crucial importance in relation to the maintenance and dissemination of Welsh identity, namely education and broadcasting. In addition, the relationship between endogenous and exogenous forces affecting Welsh identity is considered in the context of civil society, political praxis, the economy and the European Union. These events are charted and analysed by means of primarily qualitative techniques which emphasise the importance of the positional and strategic confluence of individual 'gatekeepers', who are able to influence policy and, perhaps more importantly, affect the perception and reception of new ideologies and institutional exigencies.