P. Spolaore

A 4π light-charged particle Si detector as a trigger device for in-beam γ-ray spectroscopy

A 4π Si-ball detector system has been constructed as a trigger device for the γ-ray spectrometer GASP. The construction and operation of the detector is reported, together with a brief description of the electronics and of the data acquisition system used. Results are presented for the 32S + 40Ca reaction at 140 MeV of32S beam energy.

Delayed g9/2 Alignment in the N=Z Nucleus 72Kr

The structure of Kr-72 has been investigated at GASP through the Ca-40(Ca-40,2 alpha) reaction at a beam energy of 160 MeV using the 4 pi ISIS Si-ball for reaction channel selection. The level scheme has been extended up to an excitation energy of approximate to 8.5 MeV. The spins and parities of the observed levels are assigned tentatively. The observed band shows the predicted change from oblate to prolate shape. The four quasi-particle g(9/2) alignment is found to be significantly delayed in rotational frequency with respect to the heavier Kr isotopes. Such a delay contradicts the predictions of standard mean-field calculations and may reflect either additional correlations in the T = 0 pairing channel or coupling to vibrational degrees of freedom or both

Linking transitions between the highly deformed states and the yrast states of normal deformation in 133Nd

Abstract Transitions linking the highly deformed band to low deformation states have been unambiguously established in 133 Nd in the very first experiment performed with the GASP array. the highly deformed band becomes yrast at 29 2 + , where it mixes with the positive parity band built upon the [404] 7 2 Nilsson state. The experimentally deduced interaction amounts to 13 keV. The measurement of the spins in the highly deformed intruder band sheds some light upon the reported backbend anomaly in this mass region.

Cross sections and average angular momenta in the fusion of 28Si+94,100Mo and 58,64Ni+64Ni☆

Abstract Fusion cross sections and mean angular momenta have been measured for the four systems 28Si+94,100Mo and 58,64Ni+64Ni and can be explained in the framework of the coupled-channels (CC) approach. In particular the influence of 2n-transfer channels with positive Q-values shows up. The direct relation between excitation function and angular momenta has been verified.

The TMR network project "Development of γ-ray tracking detectors"

The next generation of 4 pi arrays for high-precision gamma -ray spectroscopy will involve gamma -ray tracking detectors. They consist of high-fold segmented Ge detectors and a front-end electronics, based on new digital signal processing techniques, which allows to extract energy, timing and spatial information for a gamma -ray by pulse shape analysis of the Ge detector signals. Utilizing the information on the positions of the interaction points and the energies released at each point the tracks of the gamma -rays in a Ge shell can be reconstructed in three dimensions.

Cross sections and mean angular momenta for 64Ni + 92,96Zr fusion near and below the Coulomb barrier

Abstract Fusion cross sections and mean angular momenta have been measured for 64 Ni + 92,96 Zr around the Coulomb barrier. The results are presented and systematically compared with the predictions of a schematic coupled-channel model, demonstrating the need of more refined calculations including higher-order coupling effects, and/or other degrees of freedom, beyond the usual inelastic and quasi-elastic transfer channels.

Coupling of the recoil mass spectrometer CAMEL to the γ-ray spectrometer GASP

Abstract A project has been realized to link the CAMEL recoil mass spectrometer to the GASP γ-spectrometer in order to perform high resolution and efficiency γ-recoil coincidence measurements. To preserve high flexibility and autonomy in the operation of the two complex apparatus a rough factor two of reduction in the overall heavy ion transmission was accepted in designing the optics of the particle transport from the GASP center to the CAMEL focal plane. The coupled configuration has been tested with the fusion reaction 58 Ni (E = 212 MeV ) + 64 Ni , obtaining a mass resolution of 1 300 and efficiency between ∼ 11% and ∼ 15% for different evaporation products.

Rotation induced octupole correlations in the neutron-deficient 109Te nucleus

High spin states in the neutron deficient nucleus 109Te have been populated with the 58Ni+54Fe reaction at 220 MeV and investigated through γ-spectroscopy methods at the GASP spectrometer making use of reaction channel selection with the ISIS Si-ball. The level scheme has been extended up to an excitation energy of ≈12.1 MeV. The spins and parities of the observed levels are assigned tentatively supporting the identification of two bands of opposite parity connected by strong dipole transitions inferred to be of E1 character. Octupole correlations in 109Te induced by rotation are suggested as the cause of this effect.

Mean angular momenta in heavy ion fusion

Abstract The results of the measurement of fusion cross sections σ fus and mean angular momenta l for the five systems 16 O+ 112 Cd, 28 Si+ 94,100 Mo and 58,64 Ni+ 64 Ni are reported. The direct comparison between the fusion excitation function and l ( E ) confirms consistency of the two independent observables. By analyzing the data in the framework of the coupled channels (CC) approach a good overall agreement between experiment and model predictions has been found. In particular the influence of 2n-transfer channels with positive Q-values is put in evidence.

Gamma-ray tracking with the MARS detector

Abstract.The feasibility of the entire process of