L. Brillard

Low-energy measurement of the Be-7(p,gamma) B-8 cross-section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies. Comment: Accepted for publication in Phys. Rev. Lett

ADSORPTION OF ZR, HF, NB, TA AND PA ON MACROPOROUS ANION EXCHANGERS IN HF MEDIUM

The behaviour of the elements Zr, Hf, Nb, Ta and Pa has been investigated on macroporous anion exchange resin BIORAD AGMP 1 in HF medium (from 0.02 to 2M). All the studied elements show strong adsorption properties at low HF concentration. The adsorption was found to be highly dependent on H+ and F− concentrations. The distribution of possible adsorbable complexes is discussed.

Chemical isolation of dubnium (element 105) in fluoride media

Summary The isotope 262Db was produced by irradiation of a 248Cm target with 106-MeV 19F ions at the 15 MV MP Tandem accelerator of Orsay (France). The reaction products were continuously and rapidly transported with a KCl aerosol helium jet system to the chemistry setup. They were dissolved in HF medium and the solution was passed through three successive ion exchange columns, allowing a continuous high level purification of Db from actinides on a first cation exchange column, the isolation of Db on an anion exchange one, and the retention of the long-lived decay products of 262Db (3.24 h–254Fm) on a second cation exchange column. Just after the end of irradiation, the decay products were desorbed from this column, purified and α-sources were prepared on carbon foil by electrospray. In 13 effective irradiation hours, 22 events corresponding to the α-decay of 254Fm were recorded. Almost 70 atoms of 262Db, produced in the reaction 248Cm + 19F were isolated in dilute HF medium. Like its homologues/analogues Nb, Ta and Pa, dubnium forms, with fluoride ions, negatively charged complexes which are strongly retained on anion exchanger.

Search for chemical separation of element 106 homologues in HF and HF-HCl media

Abstract In order to study the chemical properties of element 106 in aqueous media, fast, efficient and reproducible chromatographic separations were tested on its assumed homologues: Mo, W and U. Corroborative static and dynamic off-line experiments have shown that after fixation of these three elements on an anion-exchange resin in HF medium, selective elution could be achieved by using suitable concentrations of HCl-HF and HCl solutions. Separations of short-lived W isotopes, produced through heavy ion irradiation were also performed on-line.

Isolation of Radiochemically Pure 148Gd from Alpha Particle Irradiated Samarium Oxide by Chromatographie Methods and Mass Separation

The gadolinium isotope of mass 148, because of its low α-energy (3.182 MeV) and long half-life (75 y) [1, 2], is a very interesting nuclide. Due to the similarity of its chemical properties with actinides in oxidation state III and the absence of energy interference in adetection, it can be used as a tracer in all studies of these elements which require long α-measurements; for instance, in the detection of α-emitting transactinide daughters as well as in the analysis of environmental or biological samples containing low activity of actinides [3-5] , Various methods for the separation of microamounts of gadolinium isotopes from macroamount of europium or samarium have been developed [6, 7]: liquid-liquid extraction with organophosphorous extractante, electroreduction on a mercury cathode, cementation with sodium amalgam, ion exchange or extraction chromatography ... The present paper provides a description of the radiochemical isolation of gadolinium isotopes from Eu isotopes and bulk of samarium by chromatographic methods. The isotopes mentioned were produced through irradiation of natural samarium oxide by α-particles. Chemical separations were performed by combined extraction and ionexchange chromatography. The chemical yields may be low since the aim of this work is to obtain pure sample of Gd.

Preparation par electropulverisation de sources minces pour spectrometrie alpha en geometrie alpha en geometrie 4π

Abstract Preparation of samples is an important requirement in the study of the production of the 105, 107 and 109 elements. A method is discussed that allows the preparation of trivalent actinide sources for 4π alpha spectrometry. By electrospraying of acetic solution of these carrier-free elements, with addition of some micrograms of lanthanum, sources can be prepared on carbon or metallized VYNS thin foils or directly on the gold layer of silicon surface barrier detectors. Deposition yields are greater than 90% and the resolution is better than 60 keV.

Study of the168Hf electron capture decay

The (EC, β+) decay of168Hf, produced by the156Gd (16O,4n) reaction, has been studied, with high efficiency HPGe coaxial detectors, using on-line measurements with the RACHEL setup. Off-line measurements were also carried out using catcher collection technique. Energies and intensities of 119 γ-lines are reported among these only two were known in the earlier study ofChu andReednick. The168Lu level scheme built on the basis of single γ- and X-spectra and γ-γ coincidence measurements, allows the interpretation of 79 γ-transitions, between 38 excited states reported for the first time.