E. Lienard

Two proton emission induced via a resonance reaction

A radioactive beam of N-13 ions was used to bombard a (CH2)(n) target in order to populate a narrow resonance at 7.77 MeV in O-14. A weak two proton decay branch was observed with a width of 125 +/- 20 eV which occurs predominantly by a sequential mechanism. A limit for He-2 emission of Gamma(2He) < 6 eV is compared with calculations.

Radioactive Beam Investigation of the N-13(p,Gamma)o-14 Reaction and the Hot Cno Cycle

The results of a complete set of experiments dealing with the (N(p, gamma)O)-N-13-O-14 reaction and using N-13 radioactive beams are reported. Their astrophysical implications are related to the stellar conditions under which the cold and hot CNO cycles can develop.

Production, acceleration and use of radioactive ion beams at Louvain-la-Neuve

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.

One-step energy scanning of wide low-lying 1− resonances in 13C+p and 13N+p scattering

Thick polyethylene targets have been bombarded with 8.2 MeV C-13 and N-13 beams accelerated by a cyclotron, i.e. having a relatively large energy spread of about 200 keV. Recoil protons have been detected in order to observe the J(pi) = 1- wide resonances at E* = 8.06 and 5.17 MeV in the N-14 and O-14 compound nuclei, respectively. It is shown that accurate values of the energy, width and spin of the resonant states can be obtained under experimental conditions which, at first glance, may seem inappropriate. The method is well suited for resonance studies using radioactive beams. The measured width of the N-14 resonance (GAMMA = 33.7 +/- 1.0 keV) disagrees with a recent measurement (GAMMA = 23 keV). The energy of the O-14 resonance was determined to be E(c.m) = 526 +/- 3 keV instead of 545 +/- 10 keV as quoted in the literature. A new parameter-free microscopic calculation was undertaken to solve an apparent discrepancy between the experimental proton width and a previous calculation.

New limits for the Ne-19(p,gamma)Na-20 astrophysical reaction rate from direct measurements using radioactive beams

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 Ne-19(p,gamma)Na-20 astrophysical reaction rate determined from measurements with a radioactive beam

The Ne-19(p,gamma)Na-20 as well as the Ne-19(d,n)Na-20 reaction have been studied in inverse kinematics using Ne-19 radioactive beams. Upper and lower limits for the Ne-19(p,gamma)Na-20 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 preceeding O-15(alpha,gamma)Ne-19 reaction.

Nuclear reactions of astrophysical interest with radioactive beams

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.

Production and Use of Post-accelerated Radioactive Nuclear Beams

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 m) and Ne-19(Tl 2=17 s) with an energy between 0.5 and 4.0 MeV/amu are obtained. The first experiments using these energetic radioactive beams are discussed and the ARENAS3 project is very briefly outlined.

Measurement of the 13N + 12,13C elastic scatterings

Abstract The 13 N + 12,13 C elastic scatterings have been measured at laboratory energies of 16.3, 20. and 29.5 MeV. It is shown that the 13 N + 12 C and 13 C + 12 C systems seem to comply with charge symmetry. A preliminary analysis of the 13 N + 13 C system reveals very interesting data which cannot be reproduced easily. First investigations are presented.

Precise measurement of the Jπ = 1− resonance in 14N by 13C+p elastic scattering on a thick target

The 1- resonance at 512 keV in N-14 was measured precisely by detecting recoil protons after scattering C-13 beams on a thick CH2 target. Proton spectra were analyzed with a Breit-Wigner formalism. It is shown that energy loss and straggling of the protons and of the heavy ions in the target can be correctly taken into account.