Crater formation by single ions, cluster ions and ion “showers”

Abstract

The various craters formed by giant objects, macroscopic collisions and nanoscale impacts exhibit an intriguing resemblance in shapes. At the same time, the arc plasma built up in the presence of sufficiently high electric fields at close look causes very similar damage on the surfaces. Although the plasma-wall interaction is far from a single heavy ion impact over dense metal surfaces or the one of a cluster ion, the craters seen on metal surfaces after a plasma discharge make it possible to link this event to the known mechanisms of the crater formations. During the plasma discharge in a high electric field the surface is subject to high fluxes (~10 25 cm -2 s -1 ) of ions with roughly equal energies typically of the order of a few keV. To simulate such a process it is possible to use a cloud of ions of the same energy. In the present work we follow the effect of such a flux of ions impinging the surface in the ''shower'' manner, to find the transition between the different mechanisms of crater formation. We also introduce the ''shower''-like regime of ion bombardment (underdense cloud of ions) as a subsequent regime between the single ion impact (a rare ''shower'') and cluster ions (densely packed cloud). Geneva, SwitzerlandFebruary, 2011 CLIC -Note -871Crater formation by single ions, cluster ions and ion ''showers'' Flyura Djurabekova b s t r a c tThe various craters formed by giant objects, macroscopic collisions and nanoscale impacts exhibit an intriguing resemblance in shapes. At the same time, the arc plasma built up in the presence of sufficiently high electric fields at close look causes very similar damage on the surfaces. Although the plasma-wall interaction is far from a single heavy ion impact over dense metal surfaces or the one of a cluster ion, the craters seen on metal surfaces after a plasma discharge make it possible to link this event to the known mechanisms of the crater formations. During the plasma discharge in a high electric field the surface is subject to high fluxes ($10 25 cm À2 s À1) of ions with roughly equal energies typically of the order of a few keV. To simulate such a process it is possible to use a cloud of ions of the same energy. In the present work we follow the effect of such a flux of ions impinging the surface in the ''shower'' manner, to find the transition between the different mechanisms of crater formation. We also introduce the ''shower''-like regime of ion bombardment (underdense cloud of ions) as a subsequent regime between the single ion impact (a rare ''shower'') and cluster ions (densely packed cloud).

Mechanism of vacuum breakdown in radio-frequency accelerating structures

“…A different crater formation mechanism in the arc and spark stages of a vacuum discharge is proposed in [46,47]. This mechanism implies, as that proposed in [15], the existence of a flow of ions or ion clusters, accelerated to keV energies at the metal-plasma interface, incident on the cathode.…”

Advances in the Understanding of the Physical Processes of Vacuum Breakdown

“…The code, ArcPIC, includes electric field calculation, field emission, neutral atom emission, ionization, scattering and modeling of an external driving circuit. The ion bombardment simulated in an early 1D version of the ArCPIC code was used to compute surface morphology [31].…”

From Field Emission to Vacuum Arc Ignition: A New Tool for Simulating Copper Vacuum Arcs

“…However, creating a full model of this life cycle requires the use of several simulation techniques to describe the different processes involved, which occur on different length-and time-scales. We attempt to do this with a combination of density functional theory, molecular dynamics, particle-in-cell (PIC) and hybrid simulation methods [16][17][18]. This paper focuses on modeling the initial plasma build-up in vacuum arcs using PIC.…”