We describe a variant of the quadrupole rf (Paul) ion trap capable of localization of a trapped ion to much less than an optical wavelength (Lamb-Dicke regime). The trapping potentials are generated by a high-g, vacuum-compatible, quarter-wave resonator driven at about 240 MHz. The binding strength of the trap has been characterized. The trap contains compensation electrodes which allow the cancellation of stray static electric fields within the trap. Secular frequencies of tens of megahertz have been achieved for trapped magnesium and beryllium ions.

Absolute cross sections for electron-impact single ionization of Si+ and Si + have been measured using crossed beams of ions and electrons and calculated using a configuration-average distorted-wave method. Corrections have been made for metastable components and small fractions of nitrogen impurities in the incident ion beams. Excitation-autoionization measurably enhances the cross sections of both Si+ and Si +. Ionization rate coef5cients and fitting parameters are presented for the experimental data.PACS number(s): 34.80.Kw

This paper surveys the ongoing physics experiments at the Electron Beam Ion Trap (EBIT) facility at NIST, with particular attention paid to the underlying physical principles involved. In addition, some new data on the performance of our EBIT are presented, including results related to the determination of the trap width, ion temperature, and number of highly charged ions in the trap.