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Quasi‐linear diffusion and radial transport in tokamaks

 

作者: R. D. Hazeltine,   S. M. Mahajan,   D. A. Hitchcock,  

 

期刊: Physics of Fluids(00319171)  (AIP Available online 1981)
卷期: Volume 24, issue 6  

页码: 1164-1179

 

ISSN:0031-9171

 

年代: 1981

 

DOI:10.1063/1.863506

 

出版商: AIP

 

数据来源: AIP

 

摘要:

An important difference between the classical collision operator,C(f), and Kaufman’s quasi‐linear diffusion operator in action space,D(f), is that only the former conserves particles, momentum, and energy at each spatial point. The nonlocal character of action‐space diffusion allows all transport fluxes to be expressed directly in terms of appropriate moments ofD. Thus, a general description of quasi‐linear diffusion and convection across flux surfaces in any collisionless, axisymmetric toroidal system is obtained, in terms of scale factors relating the invariant surfaces to the flux surfaces. Several analogues to the neoclassical problem are apparent, including the collisionless version of the Ware–Galeev pinch effect, whose derivation in action space is especially straightforward. Toroidicity modifies not only particle orbits but also the spatial structure of the fluctuations, and both modifications affect the resulting transport in an important way. The use of appropriate action‐angle variables automatically includes the orbital effects; crucial features of the toroidal eignmode structure are incorporated by use of the ballooning representation. This makes the fastest radial variation explicit, in terms of a single parameter describing the degree to which submodes localized on different rational surfaces overlap. The variation on slower length scales, and the overall spectral amplitude, are not determined. The radial particle flux corresponding to a Maxwellian distribution function is displayed and its dependence on properties of the spectrum is analyzed.

 

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