A. Lépine-Szily

Elastic scattering and total reaction cross section for the 6He + 27Al system

Abstract The elastic scattering of the radioactive halo nucleus 6 He on 27 Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The Sao Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of 6 He on 27 Al are similar to those for stable, weakly bound projectiles as 6,7 Li, 9 Be and larger than stable, tightly bound projectile as 16 O on 27 Al.

A fast position sensitive microchannel plate detector for ray-tracing of charged particles

Abstract Studies of nuclear reactions by the use of secondary beams involve the need of ray-tracing of either the incident beam or the reaction products. For high resolution experiments, the material interposed to the trajectory of particles must be very thin, in order to produce a minimum of perturbation of their characteristics. Secondary electrons emitted from thin foils are well suited for fast position determination. A microchannel plate detector has been developed in order to accomplish the tracing of these electrons. A parallel E - and B -field configuration, applied as a focusing device for the emitted electrons, produces an image of a reaction vertex. Thus an image of the trajectory of particles can be obtained by placing the electron producing foil into the beamline and record the position of the accelerated and focused electrons hitting a grid of sensewires.

Elastic scattering of 6He and its analysis within a four-body eikonal model

Abstract We have measured the elastic scattering of a 6 He secondary beam on a 12 C target at 41.6 MeV/u. The secondary beam was produced by fragmentation with SISSI, and transported to SPEG. The combined use of SISSI and SPEG allows very good quality data to be obtained in terms of energy and angular resolution. The cross section is analysed within a 4-body (α+n+n+ 12 C) eikonal scattering model which is completely parameter-free. Very good agreement with the data is found.

Search for the signature of a halo structure in the p(6He, 6Li)n reaction

Abstract The elastic scattering p( 6 He, 6 He)p and charge exchange reaction p( 6 He, 6 Li)n have been measured in reverse kinematics with a secondary 6 He beam. The angular distributions for these reactions were obtained. In the case of the charge exchange reaction, the ratio of the cross section for the Gamow-Teller transition to the ground state, and for the Fermi transition to the isobaric analog state is a measure of the relative strength of the two components of the exchange interaction, V στ and V τ . This ratio is found to be compatible with existing systematics for stable T = 1 nuclei, and no clear signature of a halo structure was found in the present data.

Model-unrestricted nucleus-nucleus scattering potentials from measurement and analysis of 16O + 16O scattering☆

Abstract The elastic scattering cross section for 16 O ions on 16 O targets has been measured with high accuracy over large angular ranges at incident energies from 250 to 704 MeV. From these data which sample both diffractive and refractive scattering processes, we extract the underlying scattering potentials using model-unrestricted analysis methods. The extracted potentials fit very well into the systematics found in light-ion scattering. The real potential parts also compare very favourably with microscopically calculated folding potentials based on a weak density-dependence of the underlying effective nucleon-nucleon interaction at large overlap densities.

A cyclotron as a high resolution mass spectrometer for fast secondary ions

Abstract We present the first results from a new method for mass measurements developed using the GANIL coupled cyclotrons, which uses a cyclotron as a high resolution mass spectrometer for fast secondary ions. We report here the results obtained with primary beams of 13.74 MeV/nucleon 15N and 12C, accelerated by the first cyclotron and incident on a Ta target located between the cyclotrons. Reaction products with mass-to-charge ratio of 3 were selected and accelerated by the second cyclotron. The accelerated secondary nuclei were detected in the interior of the second cyclotron using a plastic scintillator located on a radially moving rod. Details of the procedure and results are discussed. When two masses are close enough to be accelerated simultaneously by the second cyclotron, the precision in the measurement of the mass difference is better than 10−6.

The 12C+24Mg elastic scattering: An example of anomalous transparency at coulomb barrier energies

Abstract Fifteen complete angular distributions of the elastic scattering of 12 C+ 24 Mg were measured at energies around the Coulomb barrier ( E cm = 10.67–16 MeV). The angular distributions are strongly oscillating and could be well described by an optical potential family, whose real part was determined without continuous ambiguity. The imaginary part of this optical potential is very shallow. At four energies the inelastic scattering angular distributions leading to the 2 + state of the 24 Mg were also measured and analysed with coupled-channels calculations. The volume integrals of the optical potentials used in the coupled-channels calculations present the threshold anomaly in their energy dependence, with a clear Q -value dependence.

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.

7,9,10Be elastic scattering and total reaction cross sections on a12C target

Elastic scattering angular distributions for {sup 7}Be, {sup 9}Be, and {sup 10}Be isotopes on {sup 12}C target were measured at laboratory energies of 18.8, 26.0, and 23.2 MeV, respectively. The analysis was performed in terms of optical model potentials using Woods-Saxon and double-folding form factors. Also, continuum discretized coupled-channels calculations were performed for {sup 7}Be and {sup 9}Be + {sup 12}C systems to infer the role of breakup in the elastic scattering. For the {sup 10}Be + {sup 12}C system, bound states coupled-channels calculations were considered. Moreover, total reaction cross sections were deduced from the elastic scattering analysis and compared with published data on other weakly and tightly bound projectiles elastically scattered on the {sup 12}C target, as a function of energy.

Comparison of

Cross sections of 120 Sn(α,α) 120 Sn elastic scattering have been extracted from the α-particle-beam contamination of a recent 120 Sn( 6 He, 6 He) 120 Sn experiment. Both reactions are analyzed using systematic double-folding potentials in the real part and smoothly varying Woods-Saxon potentials in the imaginary part. The potential extracted from the 120 Sn( 6 He 6 He) 120 Sn data may be used as the basis for the construction of a simple global 6 He optical potential. The comparison of the 6 He and α data shows that the halo nature of the 6 He nucleus leads to a clear signature in the reflexion coefficients η L : The relevant angular momenta L with η L » 0 and η L « 1 are shifted to larger L with a broader distribution. This signature is not present in the α-scattering data and can thus be used as a new criterion for the definition of a halo nucleus.