Investigating Ultralow-Emittance Nanobeam Formation Using a Coulomb Crystal

Abstract Ultraprecise single-ion irradiation is of practical interest for the application of research and development of quantum materials and devices. To achieve this, a single-ion irradiation system, consisting of a linear Paul trap (LPT) and electrostatic bipotential lenses, is being developed at Takasaki Institute for Advanced Quantum Science, National Institutes for Quantum Science and Technology. In this paper, we conduct detailed multiparticle simulations on the controlled ejection of single ions from a two-component Coulomb crystal generated in the LPT, followed by the bipotential lens for strong focusing and acceleration of ejected cold ions, to investigate the feasibility of nanobeam formation. Two different schemes, which employ any of a string, planar, or shell crystal, are considered for selective single-ion ejection from the LPT. The present numerical results show that, in both ion ejection schemes, silicon ions sympathetically cooled through laser-cooled calcium ions can be ejected selectively from the LPT with an ultralow-emittance of the order of 10−15 m·rad or less and focused below 10 nm on the target after bipotential acceleration to 100 keV. The ion dynamics and focusing characteristics of the lens system are discussed.