Measurements of the total ion flux from vacuum arc cathode spots

Abstract

-The ion flux from vacuum arc cathode spots was measured in two vacuum arc systems. The first was a vacuum arc ion source which was modified allowing us to collect ions from arc plasma streaming through an anode mesh. The second discharge system essentially consisted of a cathode placed near the center of a spherically shaped mesh anode. In both systems, the ion current streaming through the mesh was measured by a biased collector. The mesh anodes had geometric transmittances of 60% and 72%, respectively, which were taken into account as correction factors. The ion current from different cathode materials was measured for 50-500 A of arc current. The ion current normalized by the arc current was found to depend on the cathode material, with values in the range from 5% to 19%. The normalized ion current was generally greater for elements of low cohesive energy. The ion erosion rates were determined from values of ion current and ion charge states, which were previously measured in the same ion source. The absolute ion erosion rates ranged from 16-173 µg/C.

The evolution of ion charge states in cathodic vacuum arc plasmas: a review

“…Even as only a small percentage of ions do not stick, the flux of atoms (i.e., neutralized former ions) from the surface causes a very relevant density according to   1 a c ii a n S nv v   (28) since the characteristic atom velocity a v is much smaller than the characteristic ion velocity i v . Nonsticking necessarily produces neutrals, and charge exchange reactions (27) occur, predominantly reducing the fraction of higher charged ions and producing more singly charged ions, in agreement with measurements [100,102].…”

Vacuum arc ion sources: recent developments and applications

“…These results can be taken as a refinement of the often-quoted value of about 10% [49]- [51]. The ion erosion rate experiments have been described in more detail elsewhere [52].…”

“…Interestingly, we note that the Mevva-V ion source has been operated as a high current electron source by simply changing the source bias from positive to negative [55], without any other change to the setup. The LBNL Mevva V ion source is used for a variety of research purposes including exploration of vacuum arc phenomena [46], [52], ion implantation into metals [56], semiconductors [57] and optoelectronic materials [58], synthesis of high-Tc superconductors, some bioengineering experiments [59], heavy ion fusion [60], and other. This source has been fully described in [10], [30], [61], [62].…”

The fractal nature of vacuum arc cathode spots

“…Ions have been collected by negatively biased probes placed in some macroscopic distance (for example, see companion paper [49]). Early measurements by Smeets and Schulpen [8] indicated that the Fourier amplitude is MS#TPS0860.R1, --LBNL-56776 --~1 f β with 1 β ≈ , for frequencies up to 15 MHz, and 0 β = at higher frequencies.…”