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The laser ion source has been used for the study of the isotope shifts of neutron-deficient Eu isotopes. The extension of the region of applicability of the method by using the $\gamma $ - and $\beta$ -radiation detection is reported. We have measured the isotope shifts of the europium optical line 576.520 nm for $^{137\mbox{--}139,141,142m,143,144}{\rm Eu}$ . To increase the laser ion source efficiency an axial magnetic field (350 gauss) was applied. Nearly a twofold rise of the ionization efficiency for Eu was observed. By using the effect of optical ion bunching an increase of the selectivity was obtained. The isotope shift data for $^{139,141,142m,143,144}{\rm Eu}$ are in agreement with the previously measured isotope shifts for these nuclides. The new data for $^{137}{\rm Eu}$ and refined data for $^{138}{\rm Eu}$ point to a gradual increase of the deformation for these isotopes. Comparisons with microscopic-macroscopic calculations and calculations in the framework of the Hartree-Fock model were performed.

Effect of an axial magnetic field influence on the ionization efficiency of surface and laser ion sources has been observed. The axial magnetic field applying in the range 500–800 G gives an increase of the ion current of atoms of all elements those are ionized in a hot cavity of the surface or laser ion source. Moreover, if for ionization of atoms with low ionization potentials such as K, Rb, and Cs the magnetic field applying effect is negligible, for elements with ionization potentials higher than 6 eV, such as Gd, Tm, Yb, Lu, and others it reaches value about 20 in the ion source temperature region of 2100–2500 °C. The results of on-line experiments are presented confirming the influence of the axial magnetic field on the ionization efficiency rise of neutron-deficient isotopes of rare-earth elements produced in the combined ion source-target assembly (ionizing target) and Eu isotopes resonantly ionized in the laser ion source and in the high temperature ionizing target.

International audience; Production of Rb, Cs and Fr isotopes from uranium carbide targets of a high density has been investigated. The UC target material with a density of 12 g/cm3 was prepared in a form of pellets of 2 mm thickness, 11 mm in diameter and grain dimensions of about 20 microns. Two targets were tested on-line at the same temperature conditions: a) a reference small target with a thickness of 4.5 g/cm2; b) a big massive target with a thickness of 91 g/cm2. The yields and release efficiencies of the nuclides with the half-lives from some minutes to some milliseconds produced from the investigated targets have been presented. A preliminary analysis of the obtained results has shown an increase of the produced nuclide yields proportionally to the target thickness even for very short-lived isotopes 214Fr (T1/2=5 ms) and 219Fr (T1/2=20 ms). One month off-line heating test of a big target at a temperature of 2000 °C has been conducted. The yields and release of Rb, Cs and Fr measured on-line before and after the heating test coincided in the limits of measurement errors that demonstrated the conservation of the developed target unit parameters. The construction of a big target with the mass about 0.7 kg prepared presently at IRIS has been discussed.

Three new ionization schemes for polonium have been tested with the resonant ionization laser ion source (RILIS) during the on-line production of 196Po in a UCx target at ISOLDE. The saturation of the atomic transitions has been observed and the yields of the isotope chain 193–198,200,202,204Po have been measured. This development provides the necessary groundwork for performing in-source resonant ionization spectroscopy on the neutron-deficient polonium isotopes (Z = 84). ispartof: Nuclear Instruments & Methods in Physics Research B vol:266 issue:19 pages:4403-4406 ispartof: location:FRANCE, Deauville status: published

The production of neutron-rich Ag, In and Sn isotopes from a uranium carbide target of a high density has been investigated at the IRIS facility in the PLOG (PNPI-Legnaro-GANIL-Orsay) collaboration. The UC target material with a density of 12 g/cm3 was prepared by the method of powder metallurgy in a form of pellets of 2 mm thickness, 11 mm in diameter and grain dimensions of about 20 μm. The uranium target mass of 31 g was exposed at a 1 GeV proton beam of intensity 0.05–0.07 μA. For the ionization of the produced species the electron beam–plasma ionization inside the target container (ionizing target) has been used. It was the first experiment when the new high density UC target material was exploited with the electron–plasma ionization. Yields of Sn isotopes have been measured in the target temperature range of (1900–2100) °C. The yields of some Pd, In and Cd isotopes were measured as well to compare to previously measured ones from a high density uranium carbide target having a ceramic-like structure. For the first time a nickel isotope was obtained from a high density UC target.

International audience; Production of on-line mass separated neutron-rich isotopes using fission induced by 1 GeV protons on high-density uranium targets (typically 11 g/cm3) has been investigated for several years at the IRIS facility. Here we review some of the achievements during the years up to 2006 and the perspectives. In particular, we present a comparison of yields in p and n-induced fission, enhancements by secondary neutrons, a comparison with lower-density targets used at PARRNe and ISOLDE for Rb and Cs isotopes and preliminary results obtained with a new UC target material.

International audience; The capacity of uranium carbide target materials of different structure and density for production of neutron-rich and heavy neutron-deficient nuclides have been investigated. The yields of Cs and Fr produced by a 1 GeV proton beam of the PNPI synchrocyclotron and release properties of different targets have been measured. Yields and release efficiencies of Cs and Fr produced from a high density UC target material and from low density UCx prepared by the ISOLDE method at IRIS in the collaboration with PARRNe group from Orsay are compared. The yields from ISOLDE original target are presented for comparison as well.

The branching of the ${2}^{+}\ensuremath{\rightarrow}{0}^{+}$ transition in $^{92}\mathrm{Sr}$ has been measured to 0.032(4) per $^{92}\mathrm{Rb}$ decay. It confirms an earlier measurement which was discarded in nuclear data evaluations because of a contradiction with accepted lower log $\mathit{ft}$ limits. The conflict could be solved assuming that close to half of the decay intensity, mostly as high-energy ground-state transitions, is missing in the decay scheme.

The branching of the $2+$$\rightarrow$$0^+$ transition in $^{92}$Sr has been measured to 0.032(4) per $^{92}$Rb decay. It confirms an earlier measurement which was discarded in nuclear data evaluations because of a contradiction with accepted lower log ft limits. The conflict could be solved assuming that close to half of the decay intensity, mostly as high-energy ground-state transitions, is missing in the decay scheme.

In-target resonance ionization was applied for the first time, to our knowledge, for isotope-shift and hyperfine splitting measurements at the Investigation of Radioactive Isotopes on Synchrocyclotron (IRIS) facility. The production yield of the short-lived Gd atoms and the selectivity of the laser ionization appear to be nearly two and seven times higher, respectively, compared with those of a conventional target--laser-ion-source system. Changes in mean-square charge radii $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}{}_{A,{A}^{'}}$ for $^{145}\mathrm{Gd}$,$^{145}\mathrm{Gd}{}^{m}$, and $^{143}\mathrm{Gd}{}^{m}$ and magnetic moments for $^{145}\mathrm{Gd}$ and $^{143}\mathrm{Gd}{}^{m}$ are determined. The stabilization influence of the proton subshell closure on the $\ensuremath{\delta}\ensuremath{\langle}{r}^{2}\ensuremath{\rangle}{}_{A,{A}^{'}}$ (i.e., on the deformation) behavior at $Nl82$ was not observed.

A number of on-line and off-line tests have been performed at the IRIS (investigation of radioactive isotopes at synchrocyclotron) facility in order to develop uranium carbide targets with a high density (11 g/cm3) for the on-line production of neutron-rich isotopes by fission of 238U. A 1 GeV proton beam was used to bombard two kinds of targets held at temperatures in the range of 1900–2100 °C. The first one was a target-ion source assembly slightly modified to withstand 3 months of continuous heating at a temperature of about 2050 °C. The second unit was of a new kind, where ionisation takes place in the target volume itself. A comparison of the on-line isotopic yields before and after heating for 3 months is here reported. The yields and release times of Rb, Cs and In are compared with the ones obtained from a standard reference target, as measured in previous experiments.

A series of on-line mass separation experiments have been performed at the IRIS facility to measure the yield and release of Rb and Cs neutron-rich isotopes produced by fission reaction of 238U. A 1 GeV proton beam was used to bombard uranium carbide targets with the densities of 11 g/cm3 and 1.5 g/cm3 held at temperatures in the range (2000-2230) °C. The release curves of Rb and Cs long-lived isotopes were measured from both kinds of targets. The overall production efficiency was determined making use of experimentally measured cross-sections of that isotope production. Comparison of the experimental yields of Rb and Cs isotopes with the calculated ones after corrections for losses due to finite release times suggests that the diffusion is the dominating process reducing the efficiency for short-lived isotopes. When normalized to the same thickness, an enhancement for the high-density rod target of the measured isotope yields is observed when going far from stability. This is possibly explained by the reactions induced by secondary neutrons. A significant odd-even effect with higher yields of Cs even neutron isotopes has been observed, confirming a similar effect obtained in earlier experiments.

International audience; A combined target-ion source unit (ionizing target) has been developed for the on-line production of radioactive single-charged ions. The target is able to withstand temperatures of up to 2500 °C and also acts as an ion source of surface, electron-beam, and laser ionizations. Using tantalum foil as a target material, the on-line combined target-ion source unit efficiency, which is the product of the ionization and release efficiencies, has been obtained for neutron-deficient isotopes of Eu, Gd, and Yb. These nuclides were ionized by the surface ionization inside a hot tungsten target container, holding tantalum foils as a target material. The results of the combined target-ion source unit use for on-line laser resonant ionization spectroscopy investigation of neutron-deficient Gd isotopes have been also presented. For neutron-rich isotopes produced from a high-density UC target, which were ionized by the surface ionization inside the target container, the ionization efficiency values have been obtained close to 100% for Rb and Cs and 10% for In. For Ag and Sn neutron-richisotopes, the values of the electron-beam ionization efficiency in the volume of the targetcontainer, correspondingly equal to 4% and 2%, have been obtained.