skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Collisional alpha transport in a weakly rippled magnetic field

Abstract

To properly treat the collisional transport of alpha particles due to a weakly rippled tokamak magnetic field the tangential magnetic drift due to its gradient (the$$\unicode[STIX]{x1D735}B$$drift) and pitch angle scatter must be retained. Their combination gives rise to a narrow boundary layer in which collisions are able to match the finite trapped response to the ripple to the vanishing passing response of the alphas. Away from this boundary layer collisions are ineffective. There the$$\unicode[STIX]{x1D735}B$$drift of the alphas balances the small radial drift of the trapped alphas caused by the ripple. A narrow collisional boundary layer is necessary since this balance does not allow the perturbed trapped alpha distribution function to vanish at the trapped–passing boundary. The solution of this boundary layer problem allows the alpha transport fluxes to be evaluated in a self-consistent manner to obtain meaningful constraints on the ripple allowable in a tokamak fusion reactor. A key result of the analysis is that collisional alpha losses are insensitive to the ripple near the equatorial plane on the outboard side where the ripple is high. As the high field side ripple is normally very small, collisional$$\sqrt{\unicode[STIX]{x1D708}}$$ripple transport is unlikely to be a serious issue.

Authors:
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1610180
DOE Contract Number:  
FG02-91ER54109
Resource Type:
Journal Article
Journal Name:
Journal of Plasma Physics
Additional Journal Information:
Journal Volume: 85; Journal Issue: 2; Journal ID: ISSN 0022-3778
Publisher:
Cambridge University Press
Country of Publication:
United States
Language:
English
Subject:
Physics

Citation Formats

Catto, Peter J. Collisional alpha transport in a weakly rippled magnetic field. United States: N. p., 2019. Web. doi:10.1017/s0022377819000151.
Catto, Peter J. Collisional alpha transport in a weakly rippled magnetic field. United States. https://doi.org/10.1017/s0022377819000151
Catto, Peter J. Mon . "Collisional alpha transport in a weakly rippled magnetic field". United States. https://doi.org/10.1017/s0022377819000151.
@article{osti_1610180,
title = {Collisional alpha transport in a weakly rippled magnetic field},
author = {Catto, Peter J.},
abstractNote = {To properly treat the collisional transport of alpha particles due to a weakly rippled tokamak magnetic field the tangential magnetic drift due to its gradient (the$\unicode[STIX]{x1D735}B$drift) and pitch angle scatter must be retained. Their combination gives rise to a narrow boundary layer in which collisions are able to match the finite trapped response to the ripple to the vanishing passing response of the alphas. Away from this boundary layer collisions are ineffective. There the$\unicode[STIX]{x1D735}B$drift of the alphas balances the small radial drift of the trapped alphas caused by the ripple. A narrow collisional boundary layer is necessary since this balance does not allow the perturbed trapped alpha distribution function to vanish at the trapped–passing boundary. The solution of this boundary layer problem allows the alpha transport fluxes to be evaluated in a self-consistent manner to obtain meaningful constraints on the ripple allowable in a tokamak fusion reactor. A key result of the analysis is that collisional alpha losses are insensitive to the ripple near the equatorial plane on the outboard side where the ripple is high. As the high field side ripple is normally very small, collisional$\sqrt{\unicode[STIX]{x1D708}}$ripple transport is unlikely to be a serious issue.},
doi = {10.1017/s0022377819000151},
url = {https://www.osti.gov/biblio/1610180}, journal = {Journal of Plasma Physics},
issn = {0022-3778},
number = 2,
volume = 85,
place = {United States},
year = {2019},
month = {4}
}

Works referenced in this record:

Plasma equilibrium with rational magnetic surfaces
journal, January 1981


Neoclassical transport in stellarators
journal, January 1987


Confinement of High-Energy Trapped Particles in Tokamaks
journal, August 1981


Ripple‐induced energetic particle loss in tokamaks
journal, August 1996


Generalized ripple-banana transport in a tokamak
journal, December 1983


Plasma Diffusion in a Toroidal Stellarator
journal, March 1969


Banana drift transport in tokamaks with ripple
journal, January 1982


Generalized banana-drift transport
journal, April 1986