E. C. A. Cochrane

Beam cooler for low-energy radioactive ions

An ion beam cooler for mass-separated radioactive ion beams has been developed and tested at the IGISOL-type mass separator facility. Technical description and characteristic properties are presented. An energy spread below 1 eV and transmission e

Nuclear moments and charge radii of the 171Hf ground state and isomer

ciency of 60% were measured. 2001 Elsevier Science B.V. All rights reserved.

First collinear laser spectroscopy measurements of radioisotopes from an IGISOL ion source

The magnetic moment, quadrupole moment and mean-square charge radial changes, relative to 172Hf, have been measured for the 171Hf ground state and the ½-[521] isomeric state, using on-line laser spectroscopy. The magnetic moments of the isomer and ground states are found to be + 0.526(16)µn and -0.674(12)µn, respectively. The spectroscopic quadrupole moment of the ground state is found to be +3.463(27) b. No change in mean-square charge radius is observed between the ground state and isomeric state. The observation of an inversion in the odd-even staggering at 171Hf is consistent with the suggested deformation trends.

An ion beam cooler for collinear laser spectroscopy

Abstract The standard Doppler-free technique of collinear laser spectroscopy has been successfully applied to radioisotopes from the ion-guide isotope separator (IGISOL) at the University of Jyvaskyla. The laser resonance fluorescence signals for the 140,142,144 Ba radioisotopes show that the ion beam energy spread is less than 6 eV, allowing the laser technique to have both high resolution and a sensitivity comparable with the best obtained at conventional facilities.

A thirty second isomer in Hf-171

An ion beam cooler has been constructed and tested at the IGISOL mass separator facility at the University of Jyväskylä. The cooler is designed to improve the ion optical properties of radioactive ion beams produced with fission-, light-ion fusion and heavy ion fusion ion guides. The performance of the device has been tested in off- and on-line conditions. It has been shown that the emittance and energy spread of the ion beam can be decoupled from the ion guide parameters with high transmission efficiency.

High resolution laser spectroscopy of naturally occurring ruthenium isotopes

An isomer has been detected in Hf-171 with a half-life of T-1/2 = 29.5(9) s. The state was populated in the Yb-170(alpha,3n)Hf-171m reaction at a beam energy of E-alpha = 50 MeV in an on-line ion guide isotope separator. The isomeric Hf-17lm(+) beam was extracted from the ion guide, mass-analysed and implanted in the surface of a microchannel-plate. The half-life of the collected activity was measured from the decay of the microchannel-plate count rate. We associate the isomer with the first excited slate in Hf-171 with spin 1/2(-) at an excitation energy of 22(2) keV.

Progress of laser spectroscopy at the IGISOL

High resolution crossed atomic beam laser spectroscopy has been used to measure isotope shifts and hyperfine structures in 12 transitions in naturally occurring ruthenium isotopes. Improved values for the changes in mean square charge radii have been deduced from a combined analysis of optical isotope shift and muonic x-ray data.

First measurement of radioisotopes by collinear laser spectroscopy at an ion-guide separator

The laser IGISOL facility at JYFL has successfully provided on line laser spectroscopy access to short lived isomers and refractory metal isotopes. A new ion beam cooler has been commissioned at the facility and the scope for future work has been greatly increased. The cooler can provide a low energy spread (∼1 eV), point like source of ions independent of their initial production conditions (a critical concern for spectroscopy at IGISOL facilities). New results for neutron deficient hafnium isotopes are reported. The fully operational cooler will enable future investigations to be directed at high K isomers, isotopes around Zr and at the light proton “halo” candidates.

Performance of and possibilities at the Jyvaskyla ion guide isotope separator on-line facility

The first successful application of an ion-guide separator (IGISOL) for collinear laser spectroscopy of radioisotopes has achieved an efficiency comparable with the best obtained with catcher-ionizer facilities. The ion beam energy spread was determined to be less than 6 eV, allowing laser fluorescence resonance signals for the Ba-140,Ba-142,Ba-144 radioisotopes to be detected with high resolution and sensitivity. Applications of this technique to measuring nuclear properties of refractory elements and short lived isomers promises to be particularly advantageous.