Charging of insulators by multiply-charged-ion impact probed by slowing down of fast binary-encounter electrons

Abstract

The interaction of ion beams with insulators leads to charging-up phenomena, which at present are under investigation in connection with guiding phenomena in nanocapillaries with possible application in nanofocused beams. We studied the charging dynamics of insulating foil targets [Mylar, polypropylene (PP)] irradiated with swift ion beams (C, O, Ag, and Xe at 40, 23, 40, and 30 MeV/u, respectively) via the measurement of the slowing down of fast binary-encounter electrons. Also, sandwich targets (Mylar covered with a thin Au layer on both surfaces) and Mylar with Au on only one surface were used. Fast-electron spectra were measured by the time-of-flight method at the superconducting cyclotron of Laboratori Nazionali del Sud (LNS) Catania. The charge buildup leads to target-material-dependent potentials of the order of 6.0 kV for Mylar and 2.8 kV for PP. The sandwich targets, surprisingly, show the same behavior as the insulating targets, whereas a single Au layer on the electron and ion exit side strongly suppresses the charging phenomenon. The accumulated number of projectiles needed for charging up is inversely proportional to electronic energy loss. Thus, the charging up is directly related to emission of secondary electrons.

Slowing down of fast electrons as probe for charging and decharging dynamics of ion-irradiated insulators

“…Here, as a short follow-up to Ref. [1], we report further results on BEE emission, and an analysis of convoy electron (CE) emission, which complements the BEE data. Indeed, the CE data allow for an independent control of the * Deceased.…”

“…[1]. Beams of highly charged C (23 and 40 MeV/u), O (23 MeV/u), Kr(64 MeV/u), Ag (40 MeV/u), and Xe (20, 23, and 30 MeV/u) ions were used to irradiate thin foils at the superconducting cyclotron of LNS, Catania and at GANIL, Caen.…”

“…Beams of highly charged C (23 and 40 MeV/u), O (23 MeV/u), Kr(64 MeV/u), Ag (40 MeV/u), and Xe (20, 23, and 30 MeV/u) ions were used to irradiate thin foils at the superconducting cyclotron of LNS, Catania and at GANIL, Caen. The multidetector ARGOS [1,[6][7][8] was mounted in the large scattering chamber CICLOPE or the CHIMERA chamber of LNS, or in the NAUTILUS chamber at GANIL. The velocity of fast electrons was measured by the time-of-flight (TOF) method with scintillation detectors.…”

“…[1] and references therein). For the past few years, guiding phenomena in nanocapillaries with the possible application of nanofocused beams have been extensively studied (see Refs.…”

“…[1], we reported results on the ion irradiationtime-dependent slowing down of fast binary-encounter electrons (BEEs) emitted from the insulating polymers Mylar and polypropylene (PP). All of the experiments were performed with the multidetector ARGOS.…”