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https://hdl.handle.net/2142/67785
Description
Title
Cyclotron Radiation by a Multi-Group Method
Author(s)
Chu, Terry Chingfai
Issue Date
1980
Department of Study
Nuclear Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Energy
Language
eng
Abstract
Cyclotron radiation is a serious energy loss mechanism in fusion reactors using magnetic confinement. It plays an important role in the energy-balance of the whole reactor system.
A multi-energy group technique is developed to study conditions under which cyclotron radiation emission can shift a Maxwellian electron distribution into a non-Maxwellian; and if the electron distribution is non-Maxwellian, to study the rate of cyclotron radiation emission as compared to that emitted by a Maxwellian having the same mean electron density and energy. The assumptions in this study are: the electrons should be in an isotropic medium and the magnetic field should be uniform.
The multi-group technique is coupled into a multi-group Fokker-Planck computer code to study electron behavior under the influence of cyclotron radiation emission in a self-consistent fashion. It was found that under normal thermonuclear conditions cyclotron radiation would not cause a significant shift in the electron distribution away from the normal Maxwellian. This is because of the strong influence of electron-electron collisions which forces a relaxation towards the Maxwellian.
Several non-Maxwellian distributions were simulated to compare their cyclotron emissions with the corresponding energy and number density equivalent Maxwellian distributions. The results confirm that compared to a Maxwellian, an excess of slow electrons would radiate less while an excess of fast electrons would radiate more severely.
The truncated Maxwellian distribution of electrons in mirror machines emits less ((LESSTHEQ) 40% of that from a Maxwellian) cyclotron radiation than an energy and number density equivalent Maxwellian. These non-Maxwellian electron distributions may help to make advanced fuels such as Cat.-D burn feasibly in a tandem mirror reactor because of their reduced cyclotron radiation emission. In tokamaks the runaway electrons cause the cyclotron emission to be many times (> 10) greater than the background Maxwellian.
Although the technique used in the present study does not give any information about polarization of the cyclotron radiation, it is suitable for computer codes which simulate time-dependent plasma behavior by a multi-group technique. It is especially attractive since the computer run time to calculate the cyclotron radiation is minimal as numerical integrations are avoided.
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