Two modes of transportation of a high current ion beam with ballistic focusing

Tamara Koval, Vladimir Tarakanov

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Ion sources are used to modify surface layers of different materials and manufactured items. The minimization of radiation damage of treated surfaces sets the trend to decrease the ion beam energy (< 1.5 keV). The dynamic ion beam compensation and the ion beam plasma generation should be considered to control the transport of the metallic low-energy ion beam with ballistic focusing. The ion beam transport with ballistic focusing in the equipotential drift space is studied with numerical simulation by the 2.5D axial symmetric version of the KARAT electromagnetic PiC code. It is shown that the collector current changes to the pulsed mode when the injected ion energy W < W-{c}, where W-{c} is critical energy that depends on the gas concentration and the injected ion current. The pulsed mode is the result of the virtual anode (VA) formation and its compensation by secondary electrons. In hemispherical drift space with curvature radius of 7.5 cm, the critical energy W-{c}=2 \text{keV} when the transported ion current I-{b}=1\ \mathrm{A} and the gas concentration n-{g}=10^{13}\ \text{cm}^{-3}. The oscillation frequency of the collector current depends on energy, the system geometry and the gas concentration. The oscillating mode of the collector current when decreasing the energy (W < W-{c}) of the transported ions is a result of the decreased role of secondary electrons in compensating the ion beam space charge. This leads to alternating formations: the VA formation when compensation of the space charge of the beam ions compensated. Plasma in the beam transport area is formed. A critical factor that impacts the ion beam transport mode is the electron heating under the increased plasma instability. All these processes are considered in the proposed PiC simulation. The time required to the ion-beam plasma formation and the period of the collector current pulses decrease as the transported ion energy W and the gas concentration increase.

Original languageEnglish
Title of host publicationProceedings - 2020 7th International Congress on Energy Fluxes and Radiation Effects, EFRE 2020
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages671-674
Number of pages4
ISBN (Electronic)9781728126869
DOIs
Publication statusPublished - 14 Sep 2020
Event7th International Congress on Energy Fluxes and Radiation Effects, EFRE 2020 - Virtual, Tomsk, Russian Federation
Duration: 14 Sep 202026 Sep 2020

Publication series

NameProceedings - 2020 7th International Congress on Energy Fluxes and Radiation Effects, EFRE 2020

Conference

Conference7th International Congress on Energy Fluxes and Radiation Effects, EFRE 2020
CountryRussian Federation
CityVirtual, Tomsk
Period14.9.2026.9.20

Keywords

  • Ballistic focusing
  • Ion beam transport
  • Plasma
  • Virtual anode

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Energy Engineering and Power Technology

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