J Verplancke

LISOL, the Leuven isotope separator on-line at the “cyclone”-cyclotron

Abstract LISOL, a mass separator with associated spectroscopy equipment has been brought into on-line operation at the isochronous cyclotron in Louvain-la-Neuve, Belgium. The facility enables studies of short-lived neutron-deficient isotopes. They are produced by nuclear projectiles with mass numbers up to 20 impinging on targets which are integrated into the separator ion source. Examples are given for α-induced reactions in a liquid-tin target and for 14 N-induced reactions in heated Mo-targets. Mass-separated reaction products can be guided to either one of three experimental terminals for on-line investigation. A moving-tape transport system can bring an accumulated radioactivity to detectors or spectrometers for γ-rays, conversion electrons, β-rays or charged particles. A multi-mass collector can accumulate simultaneously radio-activities from other mass chains for semi on-line detection. Nuclei as neutron deficient as 104 In and 103 In have already been investigated.

The decay of neutron deficient97Ag,98Ag, and99g, mAg

The decays of neutron-deficient 21-sec97Ag, 44.5-sec98Ag, 15-sec99mAg, and 124-sec99gAg nuclides have been investigated with the LISOL facility. Sources were produced by the92Mo(14N, ypxn) reactions on an enriched92Mo target. Positron-, x-, and γ-ray singles spectra have been performed on mass separated samples. The results are consistent with 9/2+ ground state in99Ag and a high (6+ or 7+) spin and parity for98Ag.

Decay study of103In and105In

An extensive decay scheme of105In, involving nearly 140 transitions and 35 levels in105Cd, as well as a tentative decay scheme of103In are proposed. A number of previous inconsistencies between earlier decay scheme work of105In and in-beam work on105Cd are removed. It is shown that the simple particle plus core treatment does not suffice to describe all states. A cluster plus core model seems to be an indispensable completion of this model, especially for the description of the low lying low spin states. Also the conversion coefficients of the internal transitions in105In and107In are measured. The results are well accounted for by the Moszkowski single-proton transition probabilities.

Present status and expected evolution of LISOL, the Leuven isotope separator on-line

Abstract Since the first on-line experiment in May 1975, LISOL has developed into a reliable instrument thanks to the continuous improvement of the “CYCLONE” cyclotron beams, the separator ion-sources, the beam-handling techniques and the nuclear detection techniques. The isochronous cyclotron “CYCLONE” at Louvain-la-Neuve can accelerate projectiles ranging from protons to Ar ions. With a new cyclotron ion source under construction it is expected to extend the charge state (and thus the energy), the current and the number of heavy ions available. At present five types of separator ion sources are in use, each with its favourably ionized element or group of elements, thus offering the possibility for a limited Z -selection. These are: a one filament (Cd) and a three filament Nielsen source (Ag and In), with improved heat shielding, two types of Febiad sources (Sn and In) and a new small volume source for elements with a low ionisation potential. Different targets in foil- or powder form have been tested. Until now only one group, doing nuclear spectroscopy on neutron deficient nuclei in the vicinity of Z = 50, N = 50, has been using the LISOL separator beam. They have a fast tape system, which has been extended for three or four detector coincidence measurements, and a multimass collecting system at their disposal. Two new teams, one doing on-line nuclear orientation and the other one collinear, Doppler-free laser spectroscopy are putting their apparatus behind the separator; several changes in the beam handling system have been carried out or are planned for them.

Half life measurement of the first excited O+ state in102Pd

Electron-gamma coincidences have been performed on mass separated sources of102Ag. The 1592-keV EO transition is placed in the decay scheme of 8-min102Agm. The measured half life, (17±2) nsec, reveals the anomalous nature of the first excited O+ state in102Pd.

Recoil implantation of100Pd(3.6 d) activity in different host matrices following heavy ion reactions

The large recoil energies offered by the heavy ion nuclear reactions were used to implant the100Pd(3.6 d) activity into different host matrices. The sources thus prepared were found to have good strengths and small background activities. The yields were quite high ∼3μCi/1μAh beam current of12C4+ and the efficiencies of implantation were in the range 60–70%. The difference in the recoil energies of the target and the catcher may be used to reduce activities due to unwanted nuclear reactions in the catcher foil. Using this method, we were able to prepare excellent sources of100Pd in Be, Mg, Ti, Zr and Re hosts. The quality of these sources is comparable to that of the100PdBe ion implanted sources for which data are available in the literature.

QEC-values of some neutron-deficient Ag isotopes

Recently, extensive studies on the decay of neutron-deficient Ag isotopes have been performed at LISOL, the Leuven Isotope Separator On Line. We found evidence for the new isotopes 99Agg (124 sec), 99Agm(15 sec), 98Ag(44.5 sec) and 97Ag(21 sec)1. These and some heavier Ag nuclides have been studied using singles γ and β measurements as well as γ-γ-t and β-γ-t coincidence measurements. We report here the results for the disintegration energies of the Ag-isotopes ranging from mass 98 to 102.