Calculation study of selective ion extraction from ion source with Paul-trap-type laser cooling device

Abstract

A single-ion implantation (SII) system combining a laser-cooled linear-Paul-trap ion source (LPT-IS) and a two-stage acceleration lens is being developed to produce an array of nitrogen vacancy (NV) centers, which have recently attracted significant attention as potential qubits. The fabrication of the NV center array requires repeated implantations of a single nitrogen molecule ion (N2+) from SII into a diamond specimen with an energy on the order of a 10-keV and spatial precision of several tens of nanometers or less. To satisfy this requirement, N2+ ions with very low emittance must be selectively extracted from the LPT-IS. In this study, the selective extraction of N2+ ions is investigated using a three-dimensional multiparticle simulation by varying magnitudes and temporal profile of the voltage applied to the end plate electrodes of a conventional LPT. The emittance of the N2+ extracted from the LPT-IS is the lowest when N2+ ion is at the leading end of an array of N2+ and Ca+ ions in the string-like crystalline structure formed with sympathetic cooling. We show that a single N2+ ion with required energy can be extracted from the array of N2+ and Ca+ ions passing through the end plate electrode of the LPT-IS, without spoiling the emittance, by increasing the voltage applied to the end plate electrode at the precise required moment.