Magnetic Spectrometer PRISMA Research Articles

Spectroscopy of neutron-richDy168,170: Yrast band evolution close to theNpNnvalence maximum

The yrast sequence of the neutron-rich dysprosium isotope 168Dy has been studied using multi-nucleon transfer reactions following collisions between a 460-MeV 82Se beam and a 170Er target. The reaction products were identified using the PRISMA magnetic spectrometer and the gamma rays detected using the CLARA HPGe-detector array. The 2+ and 4+ members of the previously measured ground state rotational band of 168Dy have been confirmed and the yrast band extended up to 10+. A tentative candidate for the 4+ to 2+ transition in 170Dy was also identified. The data on these nuclei and on the lighter even-even dysprosium isotopes are interpreted in terms of Total Routhian Surface calculations and the evolution of collectivity in the vicinity of the proton-neutron valence product maximum is discussed.

The many facets of heavy ion transfer reactions

With the large solid angle magnetic spectrometer PRISMA coupled to the γ array CLARA extensive investigations have been carried out for nuclear structure and reaction dynamics. In the present paper aspects of these studies will be presented, focusing more closely on the reaction mechanism, in particular on the properties of quasi-elastic and deep-inelastic processes and on measurements at energies far below the Coulomb barrier.

γ-ray spectroscopy of1738Clusing grazing reactions

Excited states of $^{38}_{17}$Cl$_{21}$ were populated in grazing reactions during the interaction of a beam of $^{36}_{16}$S$_{20}$ ions of energy 215 MeV with a $^{208}_{82}$Pb$_{126}$ target. The combination of the PRISMA magnetic spectrometer and the CLARA $\gamma$-ray detector array was used to identify the reaction fragments and to detect their decay via $\gamma$-ray emission. A level scheme for $^{38}$Cl is presented with tentative spin and parity assignments. The level scheme is discussed within the context of the systematics of neighboring nuclei and is compared with the results of state-of-the-art shell model calculations.

Installation of the AGATA Demonstrator and commissioning experiments at LNL

The first phase of the AGATA project, namely the AGATA Demonstrator Array, consists of a subset of 5 triple clusters of the final array and will be used to demonstrate the feasibility of the γ-ray tracking. The performance of the instrument has been estimated up to now only through Monte Carlo simulations and indirect measurements. The first installation is presently ongoing ay the Laboratori Nazionali di Legnaro, Italy, where it has replaced the CLARA array at the target position of the PRISMA magnetic spectrometer. In the present contribution, the details of the installation will be reviewed and preliminary results from the first in-beam commissioning test will be given.

Quasi-elastic reactions: A survey on recent results

Binary reactions at energies close to the Coulomb barrier received recently a significant boost thanks to the advent of the large solid angle magnetic spectrometer PRISMA coupled to the γ array CLARA. In the present paper different aspects of the recent results of nuclear structure and reaction dynamics will be presented, focusing more closely on the reaction mechanism.

Spectroscopy of neutron-richMn59−63isotopes

Valiente-Dobon, J. J. Lenzi, S. M. Freeman, S. J. Lunardi, S. Smith, J. F. Gottardo, A. Della Vedova, F. Farnea, E. Gadea, A. Napoli, D. R. Axiotis, M. Aydin, S. Bazzacco, D. Bizzeti, P. G. Bizzeti-Sona, A. M. Benzoni, G. Bucurescu, D. Corradi, L. Deacon, A. N. de Angelis, G. Fioretto, E. Guiot, B. Ionescu-Bujor, M. Iordachescu, A. Leoni, S. Marginean, N. Marginean, R. Mason, P. Menegazzo, R. Mengoni, D. Million, B. Montagnoli, G. Orlandi, R. Recchia, F. Sahin, E. Scarlassara, F. Singh, R. P. Stefanini, A. M. Steppenbeck, D. Szilner, S. Ur, C. A. Varley, B. J. Wieland, O.

Multinucleon transfer reactions in closed-shell nuclei

Multinucleon transfer reactions in Ca40+Zr96 and Zr90+Pb208 have been measured at energies close to the Coulomb barrier in a high-resolution γ-particle coincidence experiment. The large-solid-angle magnetic spectrometer PRISMA coupled to the CLARA γ array has been employed. Trajectory reconstruction has been applied for the complete identification of transfer products. Mass and charge yields, total kinetic energy losses, γ transitions of the binary reaction partners, and comparison of data with semiclassical calculations are reported. Specific transitions in Zr95 populated in one-particle transfer channels are discussed in terms of particle-phonon couplings. The γ decays from states in Ca42 in the excitation energy region expected from pairing vibrations are also observed.3 MoreReceived 26 April 2007DOI:https://doi.org/10.1103/PhysRevC.76.024604©2007 American Physical Society

Spectroscopy of neutron-richP37

The excited states of the neutron-rich nucleus {sub 15}{sup 37}P{sub 22} have been populated in grazing reactions, using a beam of {sup 36}S ions (at 215 MeV) delivered onto a thin {sup 208}Pb target. Emitted {gamma} rays from excited projectile-like nuclei were detected using the CLARA array of 25 escape-suppressed Ge clover detectors in coincidence with reaction products detected and identified with the PRISMA magnetic spectrometer. A level scheme is presented for {sup 37}P together with proposed spin assignments. The level structure of {sup 37}P is discussed within the context of shell-model calculations by using an improved sdpf effective interaction.

Reaction mechanism and nuclear structure explored in binary reactions: status and perspectives

Recent advances have been achieved in the field of multinucleon transfer reactions among heavy ions, both experimentally and theoretically. Detailed nuclear mass, charge and Q-value distributions allow to identify the relevant degrees of freedom acting in the transfer process. The advent of the large solid angle magnetic spectrometer PRISMA coupled to the large γ -array CLARA was a major experimental breakthrough, as reaction mechanism and nuclear structure studies of neutron rich nuclei can be performed via γ -particle coincidences. Examples of recent studies are presented.

Shape transitions far from stability: The nucleus 58Cr

Excited states up to Iπ=8+ in the neutron-rich nucleus 58Cr have been identified by using a new experimental setup composed of the large acceptance magnetic spectrometer PRISMA and the highly efficient γ-detector array CLARA. Interestingly, the excitation energy sequence of the ground-state band follows the one expected by the E(5) dynamical symmetry for a nucleus at the critical point of the shape phase transition from a spherical vibrator (U(5)) to a γ-soft rotor (O(6)). For the first time, in the same physical system, large scale shell-model calculations in the full fp shell are compared to the E(5) analytical model results and to the Interacting Boson Model. The theoretical results are in excellent agreement with the present data.

Intruder configurations in neutron-rich P and S isotopes

Neutron-rich sdf-shell nuclei have attracted a great deal of international interest, both theoretically and experimentally. There is an increasing interest in using deep-inelastic reactions to obtain spectroscopic information about these exotic nuclei. New results obtained from two such experiments are presented here. The highly sensitive GASP array was used to measure the γ decays of previously unobserved yrast and near yrast states of 34P which were populated when 230 MeV 36S ions were incident on a thick target of 176Yb. In addition, a recent investigation of the spectroscopy of neutron-rich P and S isotopes has been undertaken with 215 MeV 36S ions incident on a thin target of 208Pb using the CLARA Ge detector array in conjunction with the PRISMA magnetic spectrometer. Preliminary results from this experiment are presented here.

The CLARA-PRISMA setup installed at LNL: first results

CLARA is an array of 25 Clover (EUROBALL type) Ge detectors, placed at the target position of the large acceptance magnetic spectrometer PRISMA. Due to the granularity of the CLARA Ge array (100 crystals), the photopeak efficiency (≈3%) and the PRISMA large acceptance (≈80 msr, and 20% Δp/p), the setup is an excellent tool to investigate the structure of neutron-rich nuclei, populated in multinucleon transfer reactions and deep inelastic collisions with stable beams. Since March 2004 the setup is fully operational, and since then several experiments have been performed, with beams delivered by the LNL XTU-Tandem and the ALPI linac. In this contribution the preliminary outcome of the first experiments is shown.

Multinucleon transfer reactions studied with the heavy-ion magnetic spectrometer PRISMA

Recent inclusive measurements on multinucleon transfer reactions reveal important information on the interplay between single-particle and nucleon pair degrees of freedom. More detailed studies are being performed with the new magnetic spectrometer PRISMA, coupled to the CLARA γ-array.

First results of the CLARA-PRISMA setup installed at LNL

Spring 2004 has seen the first experiments performed with the CLARA-PRISMA setup installed at LNL (Legnaro). The setup consists of CLARA, an array of 25 Clover (EUROBALL type) Ge detectors, placed at the target position of the large acceptance PRISMA magnetic spectrometer. The setup is an excellent tool to investigate the structure of neutron-rich nuclei, populated in multinucleon transfer reactions and deep inelastic collisions with stable beams. PRISMA allows the identification of the reaction products opening the possibility to go further away from stability in comparison with previous experimental activities using the aforementioned reactions. The setup has been commissioned in the first three months of the year and since March is fully operational. Five experiments had been performed, with beams delivered by the LNL tandem and the ALPI linac. In this contribution the main features of the setup as well as the preliminary outcome of the first experiments will be described.

The focal plane detector of the magnetic spectrometer PRISMA

The characteristics and performance of the focal plane detector system developed for the magnetic spectrometer PRISMA are presented. It is composed of a multi-wire parallel plate avalanche counter (providing X, Y and timing signals) followed by a multi-parametric transverse field ionization chamber array (providing multiple Δ E signals). The detector array has been built to match the very large acceptance of PRISMA and provides optimal performance in the complete identification (nuclear charge, energy and mass) of nuclei produced in heavy-ion binary reactions.

The large-area micro-channel plate entrance detector of the heavy-ion magnetic spectrometer PRISMA

This paper describes the entrance detector of the magnetic spectrometer PRISMA recently installed at Legnaro. The detector is based on rectangular ( 80 × 100 mm 2 ) Micro-Channel Plates (MCP). It provides a fast time signal and its position-sensitive anode allows to extract the X and Y information. It exploits an electrostatic field for the acceleration of secondary electrons from a thin Carbon foil ( ≃ 20 μ g / cm 2 ) onto the MCP assembly. The electrons are guided by a parallel magnetic field. Good performances were obtained in the laboratory tests. The detector is presently installed at the entrance of PRISMA and gives resolutions ⩽ 400 ps in time, and 1 mm in both X and Y -axes, with efficiency ≃ 100 % , in typical experiments with heavy-ion beams.

Multinucleon transfer measured with the magnetic spectrometer Prisma

The magnetic spectrometer Prisma for heavy ions, at the Laboratori Nazionali di Legnaro, is a device with large acceptance and good resolution. Installation of the spectrometer and its detectors has been recently completed. Preliminary results of the first measurements on multinucleon transfer reactions are reported.

PRISMA - a magnetic spectrometer for heavy ions at LNL

The heavy-ion magnetic spectrometer PRISMA was recently installed at Laboratori Naz. di Legnaro, in order to exploit the heavy-ion beams of the XTU Tandem-ALPI-PIAVE accelerator complex, with masses up to A≃200 at energies ≃5-10 MeV MeV A.

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Gustav-Hertz Prize 2004, by H.-Jürgen KlugeTom W. Bonner Prize 2004, by Hamish RobertsonHans A. Bethe Prize 2004, by Hamish RobertsonThe Magnetic Spectrometer PRISMA, by Alberto M. Stefanini and the PRISMA CollaborationJoint Institute for Nuclear Astrophysics