Paul trap for optical frequency standards

We describe a variant of the quadrupole rf (Paul) ion trap capable of localization of a trapped ion within much less than an optical wavelength (Lamb-Dicke regime). Attainment of the Lamb-Dicke regime reduces the sensitivity of the central absorption feature to atomic motion, thereby reducing an important source of noise in an optical frequency standard. The trapping potentials are generated by a high-Q, vacuum-compatible, quarter-wave resonator driven at about 240 MHz. Secular frequencies of tens of megahertz have been achieved for trapped magnesium and beryllium ions.>