Ion Heating in a Turbulent Plasma

Abstract

The production of highly energetic ions (up to 10 keV) in, for example, large pinch discharges is well known, and has usually been attributed to acceleration of the ions by electric fields associated with the dynamics of the unstable plasma, i.e., by the fluctuating fields of the large-scale (hydromagnetic) turbulence 1 ; the time scale for this kind of process is necessarily many ion Larmor periods. We wish to report evidence for the noncollisional heating of ions to energies up to 3 keV in a situation in which the heating must be due to fluctuation frequencies CL) »fy, the ion cyclotron frequency, and which we believe results from statistical accelerations in the microfields of the turbulent spectrum of longitudinal plasma waves.The apparatus is shown schematically in Fig. 1. It consists of a silica torus, 65-cm major diam, 10-cm bore, in a quasistatic axial magnetic field Bw~ 3kG. A plasma with density ~10 12 cm"" 3 and electron temperature a few eV is prepared by passing a 1-kA axial current through weakly preionized hydrogen gas at 2-mTorr pressure. A large electric field E<p is then electromagnetically induced in this partially ionized plasma by discharging four 0.25-/iF capacitors, each charged to 35-40 kV, in series into a primary winding closely fitting the torus. With plasma loading the circuit, £ ~ 200 V cm" 1 at / = 0 and exhibits heavily damped oscillations at 1 Mc/sec. The maximum current is -20 kA at £«0.1 jusec, and the plasma resistance during the discharge is typically -1 Q.

Observation of ion heating during stimulated Buneman instability in a temporally growing plasma

“…Therefore, the generation and control of BI have created a renewed interest in the community. The major physical effects of BI include anomalous resistivity [20] and plasma heating [21,22]. Although there have been no direct experimental measurements of ion heating during the instability so far, in this letter we have conclusively proven this.…”

Recent stellarator research

“…When the linear torsatron field is converted to a toroidal one, it is necessary to add a vertical field to compensate for the toroidal effect. However, if the pitch angle is modified in an appropriate manner, the vertical field coil can also be eliminated [27,150]. The properties of the £ = 2 and 2 = 3 torsatrons are compared in Ref.…”

“…[33]. Examples of experimental devices of the torsatron type are Vint 20 (£ = 1) [219], Heliotron D (fi = 2) [144], SPAC-I (fi = 2) [238], Torso (2 = 3) [150] and Saturn (£ = 3) [146].…”

“…The stellarator programme made steady progress. Ohmic heating experiments were carried out in W lib [148], Cleo [149], Torso [150], Uragan 1 [151], JIPP Ib [153] and Heliotron D [154] and could produce plasmas with a density of n e = (0.4 -1) X 10 13 cm" 3 and an electron temperature of T e = 100 -400 eV. The confinement times were of the order of the pseudoclassical one in the range of the abovementioned parameters.…”

Temporal and Spatial Origin of Hot Ions in Turbulent Heating of a Plasma

“…1 " 3 Sutherland, Hamm, and Arakawa 7 reported structure in the optical constants of Na and K that is consistent with these predictions but does not distinguish between the absorption process suggested by Hopfield 1 as opposed to those of Lundqvist and Lyden 2 and Janow and Tzoar. 3 We report here measurements of the optical and dielectric constants of Cs at photon energies above the plasma energy.…”