Current drive in recombining plasma

Schmit, Paul; Fisch, Nathaniel J.

doi:10.1063/1.3646745

Cited by 3 publications

(3 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Since the number of fast current carriers is small compared to the bulk current carriers, the induced electric field affects primarily bulk electrons, producing current with classical resistivity. What is addressed and simulated here is the wave-generated current, I rf (t), for which the induced field can be ignored [6]. Thus a different choice of plasma parameters and expansion rates could yield a switch-like means to produce either bursts of current or voltage.…”

mentioning

confidence: 99%

“…However, Appendix A of [6] shows that the relaxation of the fast-particle current is minimally affected by the induced dc field driving an Ohmic counter-current. Then the I rf (t) calculated here can be inserted into the circuit equation along with some L/R time [8], and the solution I(t) then represents the net plasma current.…”

mentioning

confidence: 99%

“…Since particle collision rates ν c ∼ 1/v 3 , the high velocity tail relaxes more slowly than the rest of the distribution, producing a net current. However, as opposed to steady state current drive [5], here the development and relaxation of current carried by suprathermal particles will be impacted significantly by the time-varying temperature and density of the plasma as well as inductive effects [6].…”

mentioning

confidence: 99%

See 2 more Smart Citations

Driving Sudden Current and Voltage in Expanding and Compressing Plasma

Schmit

Fisch

2012

Phys. Rev. Lett.

Self Cite

View full text Add to dashboard Cite

A magnetized plasma preseeded with an initially undamped Langmuir wave is shown to transition suddenly to a collisionless damping regime upon expansion of the plasma perpendicular to the background magnetic field. The resulting anisotropic fast particle distribution then leads to an electrical current and dc voltage induction. The current drive efficiency of this effect in nonstationary plasmas is shown to depend on the rate of expansion of the plasma, the time-varying collisionality, and the plasma L/R time. Subsequent re-compression of the plasma enhances this current drive effect by reducing further the collision rate of the current-carrying electrons. Here, a new scheme to drive sudden bursts of current and voltage is predicted in nonstationary plasma, whereby an initially undamped monochromatic wave, embedded in a magnetized plasma and propagating in one direction parallel to the magnetic field, is induced into wave-particle resonance with plasma particles due to magnetic expansion perpendicular to the wavevector. The sudden, collisionless damping causes the wave to transfer its energy anisotropically onto the co-moving high-energy tail of the resonant particle distribution, while subsequent velocity-dependent collisional relaxation of the modified distribution results in a rise and fall of the total fast-particle current.As a paradigmatic example, embedded Langmuir waves are considered, though other waves may prove more suitable for specific applications. The peak attainable fast-particle current densities occur for expansion rates, η, comparable to the electron collision rate, ν c . However, expansion rates significantly faster than the collision rate lead to more prolonged current as a result of enhanced electron trapping by the wave, which carries more electrons to superthermal velocities and, hence, reduces their collisionality. Interestingly, the current can be prolonged by magnetically compressing the plasma to higher densities following the collisionless damping, which increases perpendicular velocities sufficiently to lower the collisionality of the current-carrying electrons.Before presenting the results of the numerical simulations, the basic current drive mechanism will be explained briefly. For slow variation of external forces, the Langmuir wave dispersion relation obeys the eikonal equation [3]: ω 2 = ω

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation