I. Reusen

Beams of short lived nuclei produced by selective laser ionization in a gas cell

Abstract An on-line laser ion source has been developed for the production of elemental and isobaric pure beams of radioactive ions. It is based on selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a noble gas at high pressure. The ion source has been tested in a wide range of recoil energies going from 1.3 MeV to ∼ 90 MeV. Efficient schemes of two step laser ionization through autoionizing states have been found for nickel, cobalt and rhodium. Residence times of the reaction products in a gas cell have been measured for helium and argon as buffer gas. Elementally pure beams of 54,55Ni and 54Co, produced in a light-ion induced fusion-evaporation reaction, and of 113Rh, produced in proton-induced fission of 238U, were obtained. An efficiency of the ion source of 6.6% for fusion reactions and of 0.22% for fission reactions has been obtained. A selectivity of the ion source of 300 for fusion and 50 for fission reactions has been achieved.

The SPIG, improvement of the efficiency and beam quality of an ion-guide based on-line isotope separator

Abstract A SPIG (Sextupole Ion Beam Guide) has been constructed and tested to couple an ion-guide based ion source to an on-line isotope separator. In comparison to a skimmer, the SPIG offers both an increased beam quality and the possibility to operate the ion-guide at higher buffer gas pressures.

The Leuven isotope separator on-line laser ion source

An element-selective laser ion source has been used to produce beams of exotic radioactive nuclei and to study their decay properties. The operational principle of the ion source is based on selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a noble gas at high pressure. The ion source has been installed at the Leuven Isotope Separator On-Line (LISOL), which is coupled on-line to the cyclotron accelerator at Louvain-la-Neuve. 54,55Ni and 54,55Co isotopes were produced in light-ion-induced fusion reactions. Exotic nickel, cobalt and copper nuclei were produced in proton-induced fission of 238U. The b decay of the 68–74Ni, 67–70Co, 70–75Cu and 110–114Rh isotopes has been studied by means of β–γ and γ–γ spectroscopy. Recently, the laser ion source has been used to produce neutron-deficient rhodium and ruthenium isotopes (91–95Rh, 98Rh, 90,91Ru) near the N=Z line in heavy ion-induced fusion reactions.

A detector setup to study the decay properties of exotic nuclei

Abstract General features of a detector setup for decay studies at on-line mass-separators are discussed. The detection system was used for measurements of β-decay properties of exotic nuclei with A ≈70. Results of GEANT Monte-Carlo simulations of the detector setup generally confirm the measurements. Both measurements and simulations show that even in case of low multiplicity events the Ge detector efficiency and peak to total ratio of γ-lines are reduced by large factor due to summing. Steps to improve the detection system are discussed.

Status of the laser ion source at the Leuven isotope separator online

An online laser ion source has been used at the Leuven isotope separator online for the production of pure beams of exotic nuclei. The operational principle of the ion source is based on the element-selective multistep laser resonance ionization of nuclear reaction products thermalized and neutralized in a high-pressure noble gas. A number of improvements has been carried out to obtain stable and reproducible operation. The ion source has been optimized for the production of beams of exotic nuclei, created in proton-induced fission reactions. The efficiency of the ion source has been improved by incorporating the sextupole ion guide to separate laser-produced ions from the gas jet and to transport them to the acceleration stage of the mass separator. A gas purification system has been installed to purify the noble gas down to ppb level. High selectivity and efficiency of the ion source allowed to collect nuclear spectroscopic information for the neutron deficient 54Ni and neutron-rich 68–74Ni isotopes.

Mono-isotopic beams of exotic nuclei produced by a universal on-line laser ion source

Abstract We report on recent experiments proving the high efficiency and selectivity of a universal and fast on-line laser ion source based on resonance laser ionization in a gas cell. The application for the production of neutron-rich nickel isotopes is discussed, including the first observation of γ-transitions from the decay of 71Ni. We also discuss current efforts to still increase both efficiency and selectivity.

Production of neutron-rich copper isotopes in 30-MeV proton-induced fission of 238U

Abstract The neutron-rich isotopes 70–76Cu have been produced in 30-MeV proton-induced fission of 238U using the Ion Guide Laser Ion Source (IGLIS) at LISOL. The production rates of the copper isotopes, and of the nickel and cobalt isotopes that were measured earlier, are compared to cross section calculations. Based on these new results an estimate for the cross section of 78Ni is given.

Can the waiting-point nucleus 78Ni be studied at an on-line mass-separator?

Abstract Short-lived nickel isotopes have been studied using a chemically selective Ion Guide Laser Ion Source (IGLIS) based on resonance ionisation of atoms at the Leuven Isotope Separator On-Line (LISOL) separator. The decay properties of different Ni isotopes have been studied using β-γ-coincidences. Experimental production rates of proton induced fission of 238U are obtained for 69,71Ni. These numbers are in a strong disagreement with Silberg-Tsao calculations.

Laser ion source for the Leuven Isotope Separator On‐Line

An on‐line laser ion source has been developed and coupled to an on‐line isotope separator for the production of isotopically and isobarically pure beams of radioactive ions. It is based on element‐selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a high‐pressure noble gas after their recoil out of the target. Pure beams of 54,55Ni and 54Co, produced in a light‐ion‐induced fusion‐evaporation reaction, and of 113Rh, produced in a proton‐induced fission of 238U, were obtained. A preliminary efficiency of the ion source of ∼6% for fusion reactions and of ∼0.2% for fission reactions has been obtained. A selectivity of the ion source of 300 for fusion and 50 for fission reactions limited by the evacuation of non‐neutralized reaction products has been achieved.

Gamow-Teller strength in the f7/2-nuclei 54Co and 42Sc studied through the beta decay of 54Ni and 42Ti

At the LISOL facility the neutron-deficient {sup 54}Ni isotope was produced via a {sup 3}He fusion-evaporation reaction on a {sup 54}Fe target positioned in the element-selective Ion-Guide Laser Ion Source (IGLIS). The {beta} decay of {sup 54}Ni was observed for the first time. The Gamow-Teller {beta}-decay strength associated with the (J{sup {pi}}=1{sup +}) level at 937.2 keV in the daughter nucleus {sup 54}Co was deduced. The Gamow-Teller {beta}-decay strength is in agreement with B(GT) obtained from (p,n) reaction studies. For the first time an experiment was performed using a heavy-ion beam in combination with the IGLIS in order to produce {sup 42}Ti.