Drift and separation in collisionality gradients

Abstract

We identify a single-particle drift resulting from collisional interactions with a background species, in the presence of a collisionality gradient and background net flow. We analyze this drift in different limits, showing how it reduces to the well known impurity pinch for high-Z i impurities. We find that in the low-temperature, singly-ionized limit, the magnitude of the drift becomes mass-dependent and energy-dependent. By solving for the resulting diffusion-advection motion, we propose a mass-separation scheme that takes advantage of this drift, and analyze the separative capability as a function of collisionally dissipated energy.

Strategies for advantageous differential transport of ions in magnetic fusion devices

“…( 1) can be derived from the condition that the frictional forces between these two species vanish (i.e., that there is no relative velocity). This derivation has been done previously in both the fluid picture [36] and the single-particle picture [37]. Here we will briefly replicate and extend the argument in the fluid picture, allowing for an additional species-dependent external potential Φ s with a gradient parallel to that of the pressure.…”

Maximum-entropy states for magnetized ion transport

“…In the existing literature, Eqs. ( 1) and (2) have been derived from fluid models [1,5,8], using a jump-moment formalism [2], by solving kinetic equations [4], and from a single-particle perspective [7]. In all of these cases, the resulting expression is understood as a condition for the steady state of some particular model for the timeevolution of the plasma.…”

“…This mapping is described implicitly by Eqs. (6), (7), (8), (9), and (43). Problems of this kind are not trivial [14][15][16][17][18][19][20][21], though in some cases it is possible to read off self-consistent solutions.…”

“…In a fully ionized, magnetized plasma, in the absence of temperature gradients, it is a well-known result of cross-field transport theory that collisional species a and b reach steady state only when [1][2][3][4][5][6][7]]…”

Momentum Conservation in Current Drive and Alpha-Channeling-Mediated Rotation Drive

“…Such charge extraction would create a radial electric field in the magnetized plasma, resulting in E×B rotation. Driving E×B rotation, and in particular sheared rotation, is useful in a variety of ways for plasma control; it can suppress both large-scale instabilities [25][26][27][28][29][30][31][32] and small-scale turbulence [33][34][35][36][37] , increase the confinement of mirror plasmas via centrifugal forces [38][39][40] , and even be exploited in a variety of plasma mass separation schemes [41][42][43][44][45][46][47][48][49][50] . Thus, rotation drive via alpha channeling would be an extremely useful tool to have in the plasma control toolbox.…”