Multi‐Channel Analyzer Investigations of Ion Flux at the Target Surface in Pilot‐PSI

Abstract

Pilot-PSI is a linear plasma device designed for investigations of plasma-surface interaction. A cascaded-arc plasma source operated in argon or/and hydrogen generates a high-density plasma that is magnetically confined on the vessel's axis, resulting a plasma column of about 1-2 cm in diameter which interacts with a solid target. A multi-channel analyzer was constructed to study the radial distribution of the ion flux at the target surface. The analyzer was placed in the centre of Pilot-PSI target and current-voltage characteristics were drawn for five collectors disposed at different radial positions. The ion flux was estimated from the ion part of the current-voltage characteristic for each collector. For densities lower than 10 19 m −3 (significantly below the maximum performance of Pilot-PSI), fluxes of up to 10 23 ions/m 2 s were measured. A difference of a factor four was measured between the maximum ion flux in the centre of the target and the flux at the edge, at a radial position of 1 cm.

Tailoring the charged particle fluxes across the target surface of Magnum-PSI

“…At target position, the magnetic confinement of the plasma can be considered rather weak, since the cyclotron frequency of H + ions is in the same range as their collision frequency, but this doesn't limit the validity of the results. Similar distributions were also obtained at higher magnetic fields, both in Magnum-PSI [3] as well as in Pilot-PSI [4]. Moreover, the radial gradient of the floating potential is larger for higher magnetic field strengths [3].…”

Cross-section analysis of the Magnum-PSI plasma beam using a 2D multi-probe system

“…The plasma beam in Magnum-PSI has so far mainly been characterized using Thomson scattering (TS) [4] and optical emission spectroscopy (OES) while the target surface has been investigated using infra-red (IR) imaging and calorimetry [5]. However, it has been shown that in Pilot-PSI-the forerunner of Magnum-PSI-the plasma beam is characterized by a strong radial electric field [6,7] and radial current flows through the sample exposed to the plasma [7]. It is thus of interest to characterize those parameters in Magnum-PSI where the target is exposed in a diverging magnetic field region.…”