Shinji Urabe

Majorana Effect on Atomic Frequency Standards

The Majorana effect on the hydrogen maser and the cesium (Cs) beam frequency standard is studied. In the hydrogen maser, the Majorana transition is used to the state selection successfully to eliminate the atoms in the [F = 1, mF = 1] state. As the result, a good performance of the hydrogen maser operation is obtained. In the Cs beam frequency standard, the remarkable phenomena due to this transition are described, such as the change of beam detection current, the change of the pattern in the low-frequency Zeeman transition, and the change of the velocity distributions.

Measurements of Motional Frequencies for Laser-cooled Ions in a Penning Trap

Abstract The characteristics of laser-cooled Be+ ions stored in a Penning trap are reported. Be+ ions are cooled by a laser to approximately 300 mK and the cyclotron and axial frequencies of the cooled ions are measured by a laser fluorescence technique. In addition, ion resonances are observed when several kinds of ions are trapped with Be+ ions.

Design of and Preliminary Results on a Cesium-Beam Standard at the Radio Research Laboratories

A laboratory type cesium beam standard is being constructed for experimental use as a working standard at the RRL of Japan. Ihe structural design and experimental results on the phase adjustment of Ramsey cavity, the beam optics employing hexapole magnets, and an axial C-field, and the digital servo system are described. Methods for evaluating the beam velocity distribution employing a pulse technique and the analysis of the Ramsey pattern are examined. Observed intensity of Ramsey signal proved satisfactory, and other experiments are now proceeding.

Laser microwave double-resonance experiment on trapped /sup 113/Cd/sup +/ ions

The possibility of using Cd/sup +/ ions as a microwave frequency standard whose light source is an all-solid state UV laser system is presented. The ground-state hyperfine splitting of trapped /sup 113/Cd/sup +/ ions is measured using an RF trap technique. The transition is detected using a laser microwave double-resonance method in the presence of He buffer gas. The splitting is determined to be 15 199 862 858(2) Hz. The preciseness of the value was improved over that in previous data by seven orders of magnitude. A light source of 214.5 nm is being developed by the authors for optical pumping and laser-cooling of Cd/sup +/ ions whose fundamental oscillator is based on diode lasers.

Sympathetic cooling of stored ions in a penning trap

Two different ion species (Be + and Cd + ) were trapped simultaneously in a Penning trap. The Be + ions were directly laser-cooled and the Cd + ions were sympathetically cooled to below 1 K by the Coulomb interactions. The ultraviolet spectra (5s 2 S 1/2 -5p 2 P 3/2 , 214.5 nm) of six isotopes of the Cd + ions were observed.