Beam-Ion Transport in Tokamaks: Thermalization in Large Orbit-Width Regime

Sager, Glenn Terry

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https://hdl.handle.net/2142/85942 Copy

Description

Title

Beam-Ion Transport in Tokamaks: Thermalization in Large Orbit-Width Regime

Author(s)

Sager, Glenn Terry

Issue Date

1998

Doctoral Committee Chair(s)

George Hunter Miley

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

Language

eng

Abstract

"Comparison with the present results shows that the small orbit-width approximation introduces $\ge$5% errors in the density, parallel momentum, and energy moments when $\rho\sb{\theta}/L = 0.86$ in low-$Z\sb{\rm eff}$ plasmas. These results are observed for all source pitch-angles studied except the deeply passing sources, which are in good agreement ($\le$5%) with the small orbit-width model. A non-zero current, due to the large orbit-width of the trapped fast ions, is identified and related to, the superthermal alpha particle bootstrap ""seed"" current. In low-$Z\sb{\rm eff}$ plasmas, pitch-angle scattering is only important for marginally passing ion sources. Scattering into the trapping region causes substantial inward-directed transport that is not predicted in the convective model. Parallel momentum is reduced by $\sim$70%. For cases with marginally passing sources in higher $Z\sb{\rm eff}$ plasmas, transport into the trapping region scales linearly with scattering frequency $\nu\sb{\perp}.$ The results are sensitive to source localization in a layer at the trapping/passing boundary. Significant broadening of profiles is observed for cases with deeply trapped sources in higher $Z\sb{\rm eff}$ plasmas."

Graduation Semester

1998

Type of Resource

text

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http://hdl.handle.net/2142/85942

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