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An efficient method for the production and post-acceleration of a pure F-18(T-1/2 = 109.8 min) radioactive beam has been developed. Large amounts of F-18 are produced via the O-18(p,n)F-18 reaction using a 15.5 MeV proton beam on an O-18-enriched water target. After the chemical purification of the target content, the F-18 activity is transferred into [F-18]-fluoromethane. It is then transported to an ECR ion source, where after dissociation of the molecules, the fluorine atoms are ionized. Finally, the F-18(2+) ions are accelerated to 14 MeV in a second cyclotron. The different steps in the production cycle and the characteristics of the final F-18 beam are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.

The 19Ne(p, γ)20Na as well as the 19Ne(d,n)20Na reaction have been studied in inverse kinematics using 19Ne radioactive beams. Upper and lower limits for the 19Ne(p, γ)20Na astrophysical reaction rate have been deduced, for the first time on the basis of direct experimental data. It is concluded that the transition from the hot-CNO cycle to the rp-process in explosive hydrogen burning is most likely governed by the proceeding 15O(α,γ)19Ne reaction.

Inexplosive stellar hydrogen burning, the hot CNO cycles and the rp-process are mainly linked by the reaction sequence O-15(alpha,gamma) Ne-19(p,gamma)Na-20. Using intense Ne-19 radioactive beams, both the Ne-19(p,gamma) and the Ne-19(d,n) reaction have been studied. Upper and lower limits for the Ne-19(p,gamma) reaction rate have been deduced, allowing to conclude that the O-15(alpha,gamma) reaction is most likely the bottleneck reaction.

The ARENAS(3) facility, coupling the two cyclotrons of Louvain-la-Neuve, is intensively been used over the past years for cross-section measurements of nuclear reactions of astrophysical interest. We will describe the characteristics of the available beams and the experiments going on using these beams. The Ne-19(p,gamma)Na-20 reaction, of considerable importance for the reaction now between the CNO and the NeNa mass region in high-temperature hydrogen burning conditions, will be discussed in particular. The proposed low-energy resonance at 0.447 MeV has been measured in inverse kinematics using novel activation techniques. An upper limit (90% C.L.) of 18 meV is obtained for the strength of this first particle-unbound state of Na-20 together with preliminary values for the strength of the higher excited states.

The [sup 19]Ne([ital p],[gamma])[sup 20]Na reaction may influence considerably the reaction flow between the CNO and NeNa mass regions in high temperature hydrogen burning conditions. The 447 keV resonance has been studied by exploiting radioactive [sup 19]Ne beams with novel detection techniques to measure [beta][sup +]-delayed [alpha] radioactivity of [sup 20]Na nuclei produced in reactions with polyethylene targets. A 90% C.L. upper limit of 18 meV for the resonance strength has been determined and implications for the spin assignment of the 2.646 MeV state in [sup 20]Na and the stellar reaction are discussed.

The mass separator LISOL, on-line to the CYCLONE cyclotron, is described as it is presently configured. Improvements in the cyclotron beams are mentioned, and separator developments to accommodate the various experimental stations are presented. Modifications to the separator to permit ion guide operation are given. Yields of some short-lived isotopes are presented, for heavy-ion induced reactions.

The production and acceleration of radioactive beams using two cyclotrons coupled by an electron cyclotron resonance ion source is described. Pure beams of N-13 (T1/2 = 9.96 min) and Ne-19 (T1/2 = 17 s) with an energy around 1 MeV/amu are obtained with intensities larger than 50 ppA. As an example, cross section measurements using a N-13 beam on hydrogen and deuteron targets are presented. Finally, the ARENAS3 project, a future plan for the production of radioactive beams in Belgium, is described.

An off-line release study N-13 (T1/2 = 9.96 min) produced by a proton induced reaction on a graphite target (POCO-graphite EDM3, density = 1.84 g/cm3, grain size approximately 3-mu-m) has been performed. The activation energy for the diffusion process is determined to be 6.15(16)x10(5) J/Mol. With this acitivation energy, extraction efficiences for N-13 are obtained at different temperatures and are compared to on-line measured extraction efficiencies.

A feasibility study was undertaken for the measurement of the resonance at E(r) = 545 keV in the N-13(p,gamma)O-14 reaction, using intense radioactive ion beams. The analog resonance at E(r) = 512 keV in C-12(p,gamma)N-14 was chosen as a test case, leading to improved knowledge of the resonance parameters. Thin- and thick-target yields were obtained with C-13 beams on an extended gas target and a polyethylene foil, respectively. In addition, thin and thick targets of enriched C-13 were irradiated with proton beams. Normalization problems arising with mixed ion beams (N-13/C-13) are discussed.

A single stage electron cyclotron resonance (ECR) ion source has been developed for the radioactive ion beam facility in Louvain-la-Neuve. The source was first tested with an off-line test separator using calibrated leaks of neon, nitrogen and carbon dioxide. The lingering time in the source, due to atoms sticking to the walls of the ion source, has been studied. The maximum efficiencies obtained are 52% for Ne-20(1+), 20% for N-15(1+) and 15% for C-12(1+). A N-13(1+) (T1/2 = 9.96 m) efficiency of 8% has been measured on-line.

A single‐stage electron cyclotron resonance source was developed for the Radioactive Ion Beam project. The layout of the source and results obtained with an off‐line test separator are presented. Maximum ionization efficiencies obtained for Ne+1, Ne+2, and Ne+3 using He as support gas equal 52%, 15%, and 3%, respectively.

The 19Ne(p,γ)20Na reaction may be of considerable influence for the reaction flow between the CNO and NeNa mass region in high temperature hydrogen burning conditions. The proposed low energy resonance at 0.447 MeV has been measured in inverse kinematics with the Louvain‐la‐Neuve 19Ne beam, using novel activation techniques. An upper limit to the resonance strength has been determined and the implications for the spin assignment of the 2.646 MeV state in 20Na as well as for the stellar reaction rate are discussed.

The fraction of daughter nuclei that recoil out of the catcher foil after α decay of mass-separator implanted mother nuclei is determined experimentally and compared with calculations. The correction that has to be applied on the α-branching ratio, obtained by comparing the mother and daughter activity in one α detector, is at least 20%. Previously published branching ratios can be wrong due to the underestimation of the correction procedure. As an example, the 202 Rn → 198 Po → 194 Pb decay chain is studied.

The gamma-rays de-exciting the yrast states in neutron deficient nuclei around A-55 have been observed from fusione-vaporation reactions induced by an intense radioactive Ne-19 beam on a Ca-40 target. An array of escape suppressed germanium detectors recorded reaction gamma-rays. Background subtraction of radiation from the decay of the beam was achieved using the timing properties of the pulsed beam and through particle detection using the LEDA charged particle array. These data constitute the first use of an on-line separated and accelerated radioactive beam for studies of near yrast nuclear states using fusion-evaporation reactions. Information on the gamma-ray yields from evaporation residues, relative to yields with a stable beam, has been obtained and the problems associated with performing such experiments in a highly radioactive background environment have been addressed.