N. Alamanos

16O elastic scattering at Elab = 94 MeV/nucleon

Abstract Elastic scattering of 94 MeV/nucleon 16 O on 40 Ca, 90 Zr, and 208 Pb was measured, completing similar measurements on 12 C and 28 Si. Optical model analysis of the whole set of data shows that the sensitive region where the nuclear potential is determined moves inwards as the mass of the target decreases. This determination is more precise for light systems which present a strong negative angle scattering contribution in the angular distribution. The data have also been analyzed in the framework of the folding model using density independent and density dependent nucleon-nucleon interaction. In both cases, the resulting potentials have to be renormalized to get a good description of the data. The data are consistent with a smooth decrease with energy of both the real and imaginary potentials.

The elastic scattering of 6Li+28Si at near-barrier energies

The 6 Li + 28 Si elastic scattering was studied at near-barrier energies with the aim to probe the threshold anomaly. Angular distributions were measured over a wide angular range (θlab = 25 ◦ to 150 ◦ ) at 4 energies, namely, 7.5, 9, 11 and 13 MeV. The present data together with previous ones at higher energies, as well as elastic scattering data of 6 Li on various targets at near barrier energies, were analyzed by using optical potentials obtained in a double-folding framework. It was found that the strength of the real part of the potential remains almost independent of energy down to, and possible even below, barrier, while the strength of the imaginary part presents an increase at near barrier energies. The results are discussed.  2003 Elsevier Science B.V. All rights reserved.

24.5 A MeV 6He+p elastic and inelastic scattering

The structure of 6 He is explored with proton elastic and inelastic scattering to the first 2 + excited state (Q =− 1. 8M eV) of 6 He in the inverse kinematics using a 24.5 A MeV 6 He beam. The distorted wave approximation (DWA) with an optical potential obtained by folding an effective nucleon–nucleon (NN) g-matrix with the 6 He density matrix elements as given by a large basis shell model is used to analyse the data. The comparison of predictions with the data confirms the view that 6 He has

EXCITATION OF GIANT-RESONANCES IN PB-208, SN-120, ZR-90 AND NI-60 BY 84 MEV/NUCLEON O-17 IONS

Abstract Elastic and inelastic scattering of 1435 MeV 17O ions on 208Pb, 120Sn, 90Zr and 60Ni have been measured. Hindrance in the excitation of the first 3− states is observed. Parameters of the isoscalar giant monopole and quadrupole resonances are obtained. The quadrupole resonance exhausts ∼ 55% of the energy-weighted sum rule while the observed monopole resonance corresponds to more than 100% of the sum rule. Strength is also observed at high excitation energy in all targets.

Proton reaction cross-section measurements on stable and neutron-rich nuclei as a probe of the nucleon–nucleus interaction

PCT No. PCT/JP95/02403 Sec. 371 Date Jul. 25, 1996 Sec. 102(e) Date Jul. 25, 1996 PCT Filed Nov. 27, 1995 PCT Pub. No. WO96/16993 PCT Pub. Date Jun. 6, 1996The present invention relates to a process for controlling molecular weight of a styrenic polymer by adding an organometallic compound such as triethylaluminum when a crystalline styrenic polymer having a highly syndiotactic configuration is produced by using a catalyst for producing a styrenic polymer having the syndiotactic configuration. A styrenic polymer having a highly syndiotactic configuration can efficiently be obtained by homopolymerizing or copolymerizing a styrenic compound in accordance with the process of the present invention. Therefore, the process of the present invention is expected to be advantageously used for producing the styrenic polymer.

Nuclear spin alignment and static moments of light projectile fragments measured with the Level Mixing Resonance (LMR) method

Abstract We report on the first Level Mixing Resonance experiments performed on β-decaying nuclei produced and aligned in intermediate energy fragmentation reactions. From the resonant change of the β-asymmetry as a function of a static magnetic field, we derived information on the initial alignment of 12B and 18N projectile fragments and on the nuclear structure of the neutron 18N nucleus. Positive alignments ranging from 0.9% to 14.4% have been found for different cuts in the longitudinal momentum distribution of 12B and 18N fragments. A very large ratio for the quadrupole frequency to the magnetic moment has been measured for the neutron rich 18N fragments.

Production of superheavy elements at GANIL

A long-term new experimental program has begun at GANIL, i.e. search for new super heavy nuclei and their structure. The first part consists in studying the structure of the 273110 isotope which involves the development of high intensity Se beam. In parallel, reactions involving Inverse Kinematics will be studied allowing to have a versatileness set-up. By adding germanium and electron detectors, spectroscopic studies could be made on trans-fermium elements. Preliminary results showed that the Wien Filter has a suppression of the incident beam with a 1010 factor, which is comparable with results elsewhere. We show recent results with the present set-up at GANIL in producing Fr isotopes in the Kr+Sb reaction. We present also the result of our Kr+Pb experiment, which tried to reproduce the Berkeley result of the element 118.

New target and detection methods: active detectors

Abstract The study of nuclei far from stability interacting with simple target nuclei, such as protons, deuterons, 3 He and 4 He implies the use of inverse kinematics. The very special kinematics, together with the low intensities of the beams calls for special techniques. In july 2002 we tested a new detector, in which the detector gas is the target. This allows in principle a 4π solid angle of the detection, and a big effective target thickness without loss of resolution. The detector developped, called Maya, used isobuthane C 4 H 10 as gas in present tests, and other gases are possible. The multiplexed electronics of more than 1000channels allows the reconstruction of the events occuring between the incoming particle and the detector gas atoms in 3D. Here we were interested in the elastic scattering of 8 He on protons for the study of the isobaric analogue states (IAS) of 9 He. The beam, in this case, is stopped in the detector. The resonance energy is determined by the place of interaction and the energy of the recoiling proton. The design of the detector is shown, together with some preliminary results are discussed.

Hydrogen-4 and Hydrogen-5 from t+t and t+d transfer reactions studied with a 57.5-MeV triton beam

An environmentally safe liquid/solid tritium target suitable for beams of radioactive nuclei was created and used in the study of t+d and t+t transfer reactions with putting emphasis on the observation of 4H and 5H resonance states. A state of 4H with Eres=3.22±0.15 MeV and Γobs=3.33±0.25 MeV was obtained in t+d reaction from the spectra of protons leaving the target at θlab=18°–32° and detected in coincidence with tritons. A valuable fraction of protons detected in t+t reaction at θlab=18°–32° in ptn coincidence events was attributed to the states of 5H nucleus. At ∼2.5 MeV above the tnn decay threshold the 5H spectrum shows up a narrow maximum followed by a wide structure at 4–7 MeV. One can not exclude that interference effects could modify the observed 5H resonance maximum resulting in its energy shift and width reduction.

FIRST EXPERIMENTS WITH THE FUSION DETECTOR

Abstract The Fusion Utility for Secondary Ions (FUSION) has been built to measure the fusion–fission cross section induced by radioactive beams at energies around the barrier. A set of 10 parallel plate avalanche counters measures the fission fragments which are stopped therein. Twenty plastic scintillators, surrounding the inner shell of PPACs, detect the eventual residue from the projectile. This detector could work in different geometry and allow measurements of low cross section with very weak beams. The measurements at GANIL of the fission cross sections at barrier energies for 9,11 Be on U are reported.