Ion acceleration in a pulse vacuum discharge

Abstract

A relation between the mean average energy of accelerated ions epsilon i and the maximum rate of current rise in a vacuum discharge is established. The relationship takes the power form epsilon i varies as i1.3 for different ion species over a wide range of discharge parameters for i>i0=3*108 A s-1. For smaller values of i the corresponding value of epsilon i is almost independent of the discharge parameters. The ion mass and charge-dependence of epsilon i are also discussed.

Ion energy distribution functions of vacuum arc plasmas

“…Krinberg and co-workers 25 used a magnetohydrodynamic model and pointed out that local pinching by a magnetic field can lead to ion acceleration and jet formation, especially while the discharge current is rising. This has been shown to be true in the vacuum spark regime when the discharge current has a rise rate exceeding 8 3 10 A/s × : ion kinetic energies up to 10 keV have been observed [26][27][28] . It is generally accepted that electron-ion coupling in the expanding plasma 9-13 plays a crucial role for ion acceleration, and ion acceleration due to electrostatic fields does not explain the present or other literature data.…”

Ion acceleration in vacuum arc cathode plasma jets with large rates of current rise

“…It was experimentally observed [2], [13] that the arc voltage significantly increases with . For low , the spot current does not exceed a few hundred amperes in high current arcs [1].…”

“…It is important to determine the region of that corresponds to the measured ion energy values for different spot currents. To accomplish this, was calculated using measured data [2], [3]. The results of this calculation for -and are presented in Fig.…”

“…The jet momentum equation and equation of energy conservation determine the ion velocity and its energy . The simple expression in an integral form was used from [9], [14] as (2) where is the ion mass, is the spot area, is the spot current density, is the plasma jet velocity, is the plasma jet voltage, and is the plasma pressure calculated from the spot theory. The system of equations for the cathode spot [10] was solved together with (1) and (2), taking into account the heavy particle flow in the kinetic layer for Cu, yielding , plasma density , , , and other spot parameters.…”

“…An important question is the mechanism of plasma acceleration in the cathode jets. Recently, in short pulsed high-current vacuum arcs [2], [3] and earlier for sparks [4], [5], a considerable increase of the ion energy in comparison to longer duration low current arcs has been observed. The measured ion energy range in microsecond arcs with current is 1-10 keV (high energy) while for I, 100-A millisecond arcs it is only about 100 eV (low energy) [6]- [8].…”