Effects of suprathermal fusion particles in tokamak plasmas
Petrie, Thomas Walter
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https://hdl.handle.net/2142/25591
Description
Title
Effects of suprathermal fusion particles in tokamak plasmas
Author(s)
Petrie, Thomas Walter
Issue Date
1978
Doctoral Committee Chair(s)
Miley, George H.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
suprathermal fusion particles
tokamak plasmas
center drift theory
velocity-space scattering
Language
en
Abstract
"Several crucial properties of suprathermal (>500 keV) fusion-products are explored, both in their initial phase and during their slowingdown period. A guiding center drift theory, which predicts the effect of energy loss on the motion of these suprathermals, is derived for a low-B, symmetric (non-ripple) tokamak. Velocity-space scattering is ignored. Among the important implications of this theory are: (1) the net inward drift of fusion particles during their slow-down phase, and (2) the importance of the plasma density and temperature in determiningthis drift.
The effect the inward drifting has on the spatial profile for the suprathermals approaching thermal energies, on the energy distribution, and on the plasma heating profile is demonstrated for five reactor cases, ranging from near-term low-current devices to conceptual power reactors. It is found that ""in situ"" energy deposition is a reasonable assumption for the higher current machines, like UWMAK I, differing in the plasma heating evaluation by only a few percent from our more exact treatment (SYMALF) over most of the plasma. However, for lower current tokamaks, the discrepancies between ""in situ"" and SYMALF can become quite sizeable (~2S%). It is also shown that, due to the slowing-down drifts, the fusion-product energy distribution near the plasma edge can have a positive slope with increasing energy, suggesting a possible driving mechanism for microinstabilities.
In the case of magnetic ripple, a probabilistic density function is employed to determine drift losses associated with ripple trapped, 3.52-MeV alpha particles. When used to determine 3.52-MeV alpha particle-wall-loadings, code RIPALF, which is based on this probability function, predicts the position of local ""hot spots"" along the first wall.
Either of the codes, SYMALF or RIPALF, can be used to calculate the net spatial charge build-up arising from rapid fusion particle losses. A fluid model which incorporates this information is developed to predict toroidal plasma rotation induced by these losses. The rotation resulting from ""first bounce"" alpha particles losses for a corresponding D-T system may yield measurable results under certain conditions. Toroidal rotation generated in a TFTR-like tokamak is most likely to be undetectable for deuterium-injection into a 3He thermal background."
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