Deceleration of highly charged Ni ions with compressed longitudinal kinetic energy distribution by a falling potential

Higher-precision optical clocks based on highly charged ions (HCIs) have become one of the means to explore new physics beyond the standard model. Usually, HCIs are produced by electron bombardment with high kinetic energy. Therefore, to realize an optical clock, the deceleration of HCIs is necessary. In this study, the design and operation of a deceleration beamline to produce low-energy HCIs are presented. We used time-of-flight technology to select pure 58 Ni 12+ ions. The longitudinal kinetic energy distribution of the ion beam was compressed from 11.4(4)qV (q is the electric charge of ions) to 2.2(3)qV by employing a rapidly decreasing voltage. Adopting a deceleration lens system, the longitudinal kinetic energy of the 58 Ni 12+ ions was reduced from 678.2(3)qV to 2.0(3)qV.