Leuven Isotope Separator On-Line Research Articles

In-gas laser ionization and spectroscopy of actinium isotopes near the N=126 closed shell

The in-gas laser ionization and spectroscopy (IGLIS) technique was applied on the $^{212--215}\mathrm{Ac}$ isotopes, produced at the Leuven Isotope Separator On-Line (LISOL) facility by using the in-gas-cell and the in-gas-jet methods. The first application under on-line conditions of the in-gas-jet laser spectroscopy method showed a superior performance in terms of selectivity, spectral resolution, and efficiency in comparison with the in-gas-cell method. Following the analysis of both experiments, the magnetic-dipole moments for the $^{212--215}\mathrm{Ac}$ isotopes, electric-quadrupole moments and nuclear spins for the $^{214,215}\mathrm{Ac}$ isotopes are presented and discussed. A good agreement is obtained with large-scale nuclear shell-model calculations by using a $^{208}\mathrm{Pb}$ core.

Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL

To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility that are needed for the first on-line studies of in-gas-jet laser spectroscopy. Different geometries for the gas outlet and extraction ion guides have been tested for their performance regarding the acceptance of laser ionized species as well as for their differential pumping capacities. The specifications and performance of the temporarily installed high repetition rate laser system, including a narrow bandwidth injection-locked Ti:sapphire laser, are discussed and first preliminary results on neutron-deficient actinium isotopes are presented indicating the high capability of this novel technique.

The Laser Ion Source Trap (LIST) coupled to a gas cell catcher

The proof of principle of the Laser Ion Source Trap (LIST) coupled to a gas cell catcher system has been demonstrated at the Leuven Isotope Separator On Line (LISOL). The experiments were carried out by using the modified gas cell-based laser ion source and the SextuPole Ion Guide (SPIG). Element-selective resonance laser ionization of neutral atoms was taking place inside the cold jet expanding out of the gas cell catcher. The laser path was oriented in longitudinal as well as transverse geometries with respect to the atoms flow. The enhancement of beam purity and the feasibility for in-source laser spectroscopy were investigated in off-line and on-line conditions.

Dual chamber laser ion source at LISOL

A new type of gas cell for the resonance ionization laser ion source at the Leuven Isotope Separator On Line (LISOL) has been developed and tested under off-line and on-line conditions. Two-step selective laser ionization is applied to produce purified beams of radioactive isotopes. The selectivity of the ion source has been increased by more than one order of magnitude by separation of the stopping and laser ionization regions. This allows the use of electrical fields for further ion purification.

Short-lived fission products as a diagnostics tool for studying atom and ion behavior in a gas-based laser ion source

A striking difference between gamma spectra of neutron-rich Rh isotopes obtained with the laser ion source at the Leuven Isotope Separator On-Line facility has been observed depending on the mode of operation. Although the global production rate of 112Rh g,m nuclei decreases considerably, the ratio between the productions of 112Rh g and 112Rh m increases strongly when no laser ionisation is used. This effect is caused by 112Ru atoms which decay during gas evacuation of the ion source gas cell, thereby producing 112Rh g ions. The comparison in time behaviour of reaction produced ions, β-decay produced ions and laser produced ions makes it possible to study and characterise the different processes in the gas cell. The influence of these processes has to be considered when extracting nuclear information such as the relative feeding of different short-lived isomers and isotopes and fission cross-sections in a particular mass chain.

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.

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 Ni54 and neutron-rich Ni68–74 isotopes.

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

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.

Status report on the electron cyclotron resonance ion sources used for the production of radioactive ion beams at Louvain-la-Neuve

Two single-stage, 6 GHz electron cyclotron resonance (ECR) ion sources are currently in use at the ARENAS project at Louvain-la-Neuve. One of them is used to ionize radioactive elements to low charge states (1+ to 4+) before injection in the postaccelerator cyclotron. High intensity beams of 6He, 11C, 13N, 18Ne, and 19Ne are being produced. Recently the source has been adapted for the ionization of 18F and the first experiment with this beam has been performed. A second ECR source, almost identical to the first, is used in combination with the Leuven isotope separator on-line. It produces stable and radioactive beams at 50*q keV. Mass separated beams of 13N, 14O, and 15O can be produced using a high-temperature carbon target. An upgrade of this type of ECR source is now under construction. It consists mainly of increased magnetic fields and the capability for insertion of a heated cavity.

In beam nuclear polarization of on-line separated isotopes

Dynamical nuclear polarization techniques are newly being applied at the Leuven Isotope Separator On-Line of the Cyclotron Research Center in Louvain-la-Neuve to polarize the intense radioactive ion beams which have become available. The experimental setup is described and first results are reported.

Polarization of isotope separator beams at the Leuven Isotope Separator On Line

A setup has been constructed which implements the techniques of grazing surface scattering and of the tilted foil method to produce nuclear polarized beams at the Leuven Isotope Separator On Line (LISOL), which is connected to the cyclotron Cyclone at Louvain-la-Neuve. This development makes it possible to use the intense radioactive ion beams (RIB), which will be available soon in the framework of the RIB−project at Louvain-la-Neuve, for polarization experiments. Especially solid state studies using polarized probe nuclei are envisaged in the beginning. First experiments to test the setup have been carried out and the results are very promising. The specific features of the setup are discussed together with the results of the test experiments.

Polarized nitrogen beams at LISOL

A setup has been constructed which enables to produce nuclear polarized, mass separated beams at the Leuven Isotope Separator On Line (LISOL). First experiments demonstrate the existence of substantial atomic orientations, induced with both the tilted foil (TF) and the grazing surface scattering (GSS) technique. The results of the TF experiments being as good as optimal for our situation, the GSS results can still be enhanced. The setup could be used as a complementary method in material characterization studies and first experiments to use a polarized 13N beam to determine site distributions of N implanted in Fe are being planned.

In-beam induced nuclear polarization of radioactive ion beams

A system to polarize nuclear beams in-flight has been built at the central beam line of the Leuven Isotope Separator On Line (LISOL) at the Cyclotron Research Center in Louvain-la-Neuve. Surface collisions at grazing incidence as well as the tilted foil method are being applied as polarizing techniques. These methods are generally applicable and overcome the limitations imposed by the low temperature in situ nuclear orientation technique. First polarization tests have been carried out with a 50 keV 14N + ion beam: (i) transmitted through a 2 μg/cm 2 tilted C-foil and (ii) scattered at about 2.5 ° from a flat Si(100) single crystal. The atomic polarization of the ions was detected by measuring the circular polarization of the 500 nm NII 2s 22p3p 3D2s 22p3d 3F° and the 567 nm NII 2s 22p3s 3P2s 22p3p 3D optical transitions. Values for S/ I of 10.2(1.9)% (500 nm) were deduced for the tilted foil and 7.7(1.1)% (500 nm) and 6.9(1.7)% (567 nm) for the scattering at the Si-surface.

Low and medium energy radioactive ion beams at Louvain-la-Neuve, Belgium

At Louvain-la-Neuve, radioactive ion beams (0.6 MeV/amu) have been produced, combining the variable energy, multiparticle cyclotron CYCLONE ( k = 110 MeV) and the newly developed, high intensity 30 MeV H − cyclotron, CYCLONE 30. The Leuven Isotope Separator On Line (LISOL) produces low energy radioactive beams (50 keV acceleration energy) which are mainly used for nuclear physics experiments. Radioactive beams with masses ranging from A ≅ 8 up to A ≅ 240 are obtained by light and heavy ion induced fusion and fission reactions. This paper describes a new project for accelerating these beams to medium energies (up to 1.5 MeV/amu) for use in nuclear, astrophysical and solid state studies (ARENAS 3).