ISSN:
1089-7666
Source:
AIP Digital Archive
Topics:
Physics
Notes:
In the plasma physics literature there appear two different definitions of Pfirsch–Schlüter current. One of them is predominantly used in equilibrium calculations and satisfies the condition IT=0. The other definition appears commonly in transport calculations and requires that the surface average of the dot product of the Pfirsch–Schlüter current density with the magnetic field vanish, i.e., 〈JPS⋅B〉=0. The difference between the definitions is a surface function. Within the framework of the moment equation approach, the total parallel current is completely determined through a surface average of Ohm's law; thus different definitions of Pfirsch–Schlüter current imply different expressions for the bootstrap current. Understanding the different implications of these two definitions is of particular importance when designing toroidal devices with minimized Pfirsch–Schlüter current or studying tokamaks with optimized bootstrap current. In this paper the definitions of Pfirsch–Schlüter and bootstrap current, as well as the expressions for the corresponding Pfirsch–Schlüter diffusion flux, are analyzed and discussed for the case of axisymmetric and nonaxisymmetric plasmas. Although in cases like a current-free stellarator or a large-aspect-ratio tokamak both definitions are equivalent, they are in general different, and in order to avoid misunderstandings it is therefore important to use only one. The most appropriate definition is IT=0. In this paper the equations for determining the bootstrap current within the framework of the fluid equations are also analyzed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.860085
