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Abstract
This thesis deals with two distinct topics. In part I, action-angle methods are applied to several problems in tokamak transport. In part II, the multiphoton excitation of atomic systems is considered.
Part I begins with a development of the basic action-angle formalism used throughout this work. This is first applied to the problem of nondiffusive energetic triton losses due to MHD activity. Next the 'stochastic regime' diffusion of ions in a general ripple perturbation (finite n, m, $\omega$) is considered. A generalized stochastic threshold is derived. We conclude by considering the diffusion of thermal and energetic particles in a turbulent spectrum. The reduction of transport due to orbit averaging is demonstrated. Also, from an observed upper bound on energetic triton diffusion in TFTR, an upper bound on the level of magnetic fluctuations is inferred.
The second part of this thesis, on multiphoton atomic processes, begins with a review of this new and rapidly developing field. The intense fields typically required to drive a multiphoton transition are found to preclude a perturbative treatment. Non-perturbative methods, used throughout this work, are therefore introduced. These are first applied to the analysis of multiphoton transitions between two low lying atomic states. Comparison is made between excitation and ionization rates for specific atomic systems. The same methods are also applied to the analysis of multiphoton transitions in Rydberg atoms. Resonance conditions, transition thresholds, and ionization thresholds for such atoms are found to be in close agreement with experimental observations.
