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Title:Beam-Ion Transport in Tokamaks: Thermalization in Large Orbit-Width Regime
Author(s):Sager, Glenn Terry
Doctoral Committee Chair(s):George Hunter Miley
Department / Program:Nuclear Engineering
Discipline:Nuclear Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Nuclear
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.
Issue Date:1998
Description:159 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1998.
Other Identifier(s):(MiAaPQ)AAI9904576
Date Available in IDEALS:2015-09-28
Date Deposited:1998

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