arXiv subjects

I. E. Ochs

Publications and source records attributed to I. E. Ochs.

25 records · Page 2Linked to original sources

arXiv2020

Heat Pump via Charge Incompressibility in a Collisional Magnetized Multi-Ion Plasma

Stratification due to ion-ion friction in a magnetized multiple-ion species plasma is shown to be accompanied by a heat pump effect, identified for the first time here, transferring heat from one ion species to another as well as from one region of space to another. The heat pump is produced via newly identified heating mechanisms associated with charge incompressibility and the Ettingshausen effect. Besides their academic interest, these new effects may have useful applications to plasma technologies that involve rotation or compression.

physics.plasm-ph↗

arXiv2020

Maximum-Entropy States for Magnetized Ion Transport

For a plasma with fixed total energy, number of particles, and momentum, the distribution function that maximizes entropy is a Boltzmann distribution. If, in addition, the rearrangement of charge is constrained, as happens on ion-ion collisional timescales for cross-field multiple-species transport, the maximum-entropy state is instead given by the classic impurity pinch relation. The maximum-entropy derivation, unlike previous approaches, does not rely on the details of the collision operator, only on the presence of certain conservation properties.

physics.plasm-ph↗

arXiv2019

Radial Current and Rotation Profile Tailoring in Highly Ionized Linear Plasma Devices

In a rotating magnetized plasma cylinder with shear, cross-field current can arise from inertial mechanisms and from the cross-field viscosity. Considering these mechanisms, it is possible to calculate the irreducible radial current draw in a cylindrical geometry as a function of the rotation frequency. The resulting expressions raise novel possibilities for tailoring the electric field profile by controlling the density and temperature profiles of a plasma.

physics.plasm-ph↗

arXiv2018

Nonlinear Ohmic Dissipation in Axisymmetric DC and RF Driven Rotating Plasmas

An axisymmetric fully ionized plasma rotates around its axis when a charge separation between magnetic surfaces is produced from DC fields or RF waves. On each magnetic surface both electrons and ions obey the isorotation law and perform an azimuthal E cross B rotation at the same angular velocity. When Coulomb collisions are taken into account such a flow displays no Ohmic current short circuiting of the charge separation and thus no linear dissipation. A nonlinear Ohmic response appears when inertial effects are considered, providing a dissipative relaxation of the charge separation between the magnetic surfaces. This nonlinear conductivity results from an interplay between Coriolis, centrifugal and electron-ion collisional friction forces. This phenomena is identified, described and analyzed. In addition, both the quality factor of angular momentum storage as well as the efficiency of wave driven angular momentum generation are calculated and shown to be independent of the details of the charge separation processes.

physics.plasm-ph↗

arXiv2018

Strategies for Advantageous Differential Transport of Ions in Magnetic Fusion Devices

In a variety of magnetized plasma geometries, it has long been known that highly charged impurities tend to accumulate in regions of higher density. Here, we examine how this "collisional pinch" changes in the presence of additional forces, such as might be found in systems with gravity, fast rotation, or non-negligible space charge. In the case of a rotating, cylindrical plasma, we describe a regime in which the radially outermost ion species is intermediate in both mass and charge. We discuss implications for fusion devices and plasma mass filters.

physics.plasm-ph↗

arXiv2017

Drift and Separation in Collisionality Gradients

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.

physics.plasm-ph↗

arXiv2017

Particle Orbits in a Force-Balanced, Wave-Driven, Rotating Torus

The wave-driven rotating torus (WDRT) is a recently proposed fusion concept where the rotational transform is provided by the E x B drift resulting from a minor radial electric field. This field can be produced, for instance, by the RF-wave-mediated extraction of fusion-born alpha particles. In this paper, we discuss how macroscopic force balance, i.e. balance of the thermal hoop force, can be achieved in such a device. We show that this requires the inclusion of a small plasma current and vertical magnetic field, and identify the desirable reactor regime through free energy considerations. We then analyze particle orbits in this desirable regime, identifying velocity-space anisotropies in trapped (banana) orbits, resulting from the cancellation of rotational transforms due to the radial electric and poloidal magnetic fields. The potential neoclassical effects of these orbits on the perpendicular conductivity, current drive, and transport are discussed.

physics.plasm-ph↗