Recent Achievements and Perspectives in Nuclear Physics

FOREWORD.

LOCAL ORGANIZING COMMITTEE AND INTERNATIONAL ADVISORY COMMITTEE.

PROGRAMME.

CONTENTS.

Direct reactions of exotic nuclear beams populating their excited states are discussed from the aspects of the inverse kinematics by measuring in-flight decay of the beam-like nucleus and the selectivity of the reactions. Emphasis is made for inelastic scatterings and nucleon transfer reactions of α using a liquid helium target. As an example of the α inelastic scattering, recent experimental results on the isoscalar electric responses of the ¹⁴O are presented and discussed on the continuum effects on the isoscalar E0 and E1 responses. Recent experiments on γ-ray spectroscopy of ¹³B* and ²³F* populated by the proton-transfer reaction (α,t) at 30–55 A MeV are also demonstrated for studies of single particle states in exotic nuclei.

We have studied several exotic nuclei around doubly magic ¹⁰⁰Sn and ¹³²Sn in terms of the shell model employing realistic effective interactions derived from the CD-Bonn nucleon-nucleon potential. The short-range repulsion of the bare potential has been renormalized by constructing a smooth low-momentum potential, V_low–k, that is used directly as input for the calculation of the effective interaction. In this paper, after a brief survey of the theoretical framework, we present some selected results of our studies. Comparison shows that our results are in very good agreement with the available experimental data. This may stimulate experimental efforts to gain more information on nuclei in these regions of shell closures off stability.

Recent advances in the large-scale shell-model calculation performed by the authors are presented. Since the shell model, a powerful tool to study the nuclear structure, is often confronted with the computational limitation when applied to a heavier region, the Monte Carlo shell model is proposed to overcome the limitation. Owing to the development of the large-scale shell-model calculation, we can obtain a systematic description of some regions. From this the relation between the effective interaction and the nuclear structure is clarified, as exemplified in the N ~ 20 region, the pf-shell region, and the medium-heavy mass region.

The event assigned to the convincing candidate of an isotope of the 113th element, ²⁷⁸113, and its daughter nuclei, ²⁷⁴Rg and ²⁷⁰Mt, were observed in the reaction ²⁰⁹Bi + ⁷⁰Zn at a beam energy of 349.0 MeV with a total dose of 1.7×10¹⁹, for the first time. Alpha decay energies and decay times of the candidates, ²⁷⁸113, ²⁷⁴Rg, and ²⁷⁰Mt were (11.68±0.04 MeV, 0.344 ms), (11.15±0.07 MeV, 9.26 ms), and (10.03±0.07 MeV, 7.16 ms), respectively. The production cross-section of the isotope were deduced to be .

A few examples of recent experimental and theoretical works performed in the frame of the GASP collaboration are reported. Selected examples concern recent results on dynamical symmetries and phase transitions in nuclear shape: in particular, the isospin symmetry in the A = 35 isobaric doublet, the X(5) symmetry at the critical point of phase transition in ¹⁷⁸Os and the new field of phase transitions in the octupole mode.

In this paper we review two important aspects of the study of reaction mechanisms for structure studies of halo and weakly bound nuclei. The first is related to the importance of a proper interpretation of elastic scattering data on heavy nuclei, by including the Coulomb breakup effects on the microscopic optical potentials. The second has to do with understanding the special characteristics of two-neutron halo nuclei such as ¹⁴Be, in which the two neutron pair is bound, while each single extra neutron is unbound in the field of the core. A model to describe projectile fragmentation, following which neutron-core coincidences are recorded and the neutron-core relative energy spectrum is reconstructed, is presented with an application to the study of ¹³Be. We wish to see whether the neutron-¹²Be relative energy spectra obtained from fragmentation of ¹⁴Be or ¹⁴B would show differences predictable in a theoretical model.

The effect of the nuclear deformation on heavy-ion fusion reactions were investigated for the reactions ^60,64Ni + ¹⁵⁴Sm and ⁷⁶Ge + ¹⁵⁰Nd, where ¹⁵⁴Sm and ¹⁵⁰Nd are well deformed nuclei. It is found that the fusion probability strongly depends on the orientation of these deformed nuclei. When projectiles collide at the tip of the deformed nuclei, the fusion probability is considerably reduced. On the other hand, when projectiles collide at the side of the deformed nuclei, the fusion occurs without any hindrance. This result suggests that the compact configuration at touching forms more easily a compound nucleus than an elongated configuration. The effect of the nuclear shell structure on heavy-ion fusion reactions was also investigated for the reaction systems ⁸²Se + ¹³⁸Ba, ⁸²Se + ¹³⁴Ba, ¹⁶O + ²⁰⁴Pb, ⁸⁶Kr + ¹³⁴Ba, ⁸⁶Kr + ¹³⁸Ba, and ⁸²Se + ^nat.Ce. The measured evaporation residue cross-sections for the reactions ⁸²Se + ¹³⁸Ba and ⁸⁶Kr + ¹³⁸Ba were two orders of magnitude and one order of magnitude larger than those for the reactions ⁸²Se + ¹³⁴Ba and ⁸⁶Kr + ¹³⁴Ba, respectively, at the excitation energy region of 10 ~ 30 MeV. It was found that the evaporation residue cross-sections correlate strongly with the sum of the shell energies for both projectile and target nuclei, i.e., the evaporation residue cross-sections increase as the sum of the shell energy decreases.

We perform molecular dynamics simulations of screening by bound target electrons in low energy nuclear reactions. Quantum effects corresponding to the Pauli and Heisenberg principle are enforced by constraints. We show that the enhancement of the average cross section and of its variance is due to the perturbations induced by the electrons. This gives a correlation between the maximum amplitudes of the inter-nuclear oscillational motion and the enhancement factor. It suggests that the chaotic behavior of the electronic motion affects the magnitude of the enhancement factor.

The new magnetic spectrometer PRISMA for heavy-ions has been installed at the end of 2002 and is now operating at LNL. In-beam tests evidenced experimental resolutions consistent with the design characteristics of the setup. A first experimental campaign has been completed at the end of 2004.

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 array (100 crystals), the photopeak efficiency (≈3%) and the PRISMA large acceptance, 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. The setup is now fully operational, and the preliminary outcome of the first experiments will be discussed.

A polarization asymmetry measurement with an unstable beam of ⁶He with an energy of 71 MeV/u has, for the first time, been successfully carried out. For this purpose a new type of the spin polarized solid proton target was constructed which can be operated under a low magnetic field of 0.08 T and a high temperature of 100 K.

The study of the gamma decay from the giant dipole resonance (GDR) built on highly excited states continues to be a useful tool to explore the basic nuclear nuclear properties at finite temperature and angular momenta. In particular the dependence of the GDR width as a function of temperature and angular momentum provides information on the evolution of the nuclear shapes and of the damping mechanisms of this collective state. Here we focus on results of new exclusive measurements concerning a region at the low temperature at around 1-1.5 MeV and at high angular momenta close to the fission limit. Two different behaviours of the nuclear shape are found for the mass region A=40 and A=220. In the first case some evidence for the Jacobi transition (oblate to prolate shape transition) is found while for the heavy mass the data show the persistence of nearly spherical shapes up to the fission limit.

We studied the prompt dipole γ-ray emission, associated with entrance channel charge asymmetry effects, as a function of incident energy in the ^32,36S + ^100,96Mo (E_lab=6 MeV/nucleon) and ^36,40Ar + ^96,92Zr fusion reactions (E_lab= 16 and 15 MeV/nucleon, respectively). With the above reaction pairs the ¹³²Ce compound nucleus was formed, from entrance channels having different charge asymmetries, at an excitation energy of 117 and 304 MeV with identical spin distribution. By studying the differential γ-ray multiplicity spectra related to the above fusion reactions, it was shown that at the higher compound nucleus excitation energy the Giant Dipole Resonance γ-ray intensity increases by ~14% for the more charge asymmetric system while at the lower one no difference between the data was seen within the experimental uncertainties. Calculations based on a collective bremsstrahlung analysis of the reaction dynamics are presented and compared with the experimental findings.

To study the order-to-chaos transition in nuclei we investigate the validity of the K-quantum number in the excited rapidly rotating ¹⁶³Er nucleus, analysing the variance and covariance of the fluctuations of counts of spectra γ-cascades feeding into low-K and high-K bands. The data are compared to simulated spectra obtained using microscopic cranked shell model calculations. K-selection rules are found to be obeyed in the decay along excited unresolved rotational bands of internal excitation energy up to around 1.2 MeV. At higher internal energy, from about 1.2 to 2.5 MeV, the selection rules are found to be only partially valid.

Coupling to reaction channels (including continuum break-up channels) seems to predict enhancement of fusion below the barrier (for total fusion and, to a lesser degree, also for complete fusion), when the reaction process is treated within the conventional coupled-channel approach, with proper modifications due to weak-binding nature of halo systems (as for example the long range of formfactors and potentials).

The experimental results concerning the reaction mechanisms of light weakly bound stable as well as radioactive nuclei, on various targets at near-barrier energies are reviewed and discussed. In order to study the reaction mechanisms of radioactive nuclei at near-barrier energies our collaboration developed a new line (EXOTIC) for the production of light exotic nuclei, by inverse kinematics nuclear reactions using the beams from the Tandem XTU accelerator of the Laboratori Nazionali di Legnaro impinging on H₂ or CH₄ gas target.

The scattering process for the system ¹¹Be + ²⁰⁹Bi has been measured in the energy range around the Coulomb barrier at the RIKEN RIPS facility. The scattered ¹¹Be ions have been detected with a new type of large solid angle pixel-structure detector array, named EXODET. The experimental data evaluated at 44-MeV ¹¹Be beam energy have been compared with those obtained for the stable system ⁹Be + ²⁰⁹Bi. The comparison allowed to investigate for the first time the effects due to the ¹¹Be halo structure and low binding energy on the scattering process.

We have started a research program at LNL with the apparatus 8πLP aimed at studying the fission dynamics in systems of intermediate fissility using light charged particles as probes. These systems are characterized by an evaporation residues (ER) cross section comparable or larger than the fission cross section, and by a relatively higher probability for charged particle emission in the pre-scission channel. In a theoretical framework in which time scale estimates rely on statistical model calculations, the additional analysis of particle emission in the ER channel allows to put more constraints on the input parameters of statistical and dynamical models. The presentation will report about an overall view of the systems studied so far and will provide clues for interesting physical cases. Recent advancement will also be discussed on the interplay between the fission and the evaporation residues channels as implied by a dynamical approach to the description of the fission process.

Evaporative proton and alpha particle energy spectra and angular distributions have been measured in the decay of the compound nucleus ¹³⁹Eu produced at an excitation energy of 90 MeV by the ³²S + ¹⁰⁷Ag reaction. In-plane and out-of-plane angular distributions and energy spectra of alpha particles have been compared with theoretical calculations performed using the statistical Montecarlo code Lilita. Three expressions for the level density parameter have been used: a) without isospin dependence b) with N-Z isospin dependence and c) with Z-Z₀ isospin dependence, based on the distance of the nucleus from the valley of stability. The predictions by the Z-Z₀ prescription fail to reproduce the data. Isospin independent and N-Z dependence reasonably well reproduce the data.

A key question in the physics of unstable nuclei is the knowledge of the EOS for asymmetric nuclear matter (ANM) away from normal conditions. We recall that the symmetry energy at low densities has important effects on the neutron skin structure, while the knowledge in high densities region is crucial for supernovae dynamics and neutron star properties. The only way to probe such region of the isovector EOS in terrestrial laboratories is through very dissipative collisions of asymmetric (up to exotic) heavy ions from low to relativistic energies. A general introduction to the topic is firstly presented. We pass then to a detailed discussion on the neck – fragmentation process as the main dissipative mechanism at the Fermi energies and to the related isospin dynamics. From Stochastic Mean Field simulations the isospin effects on all the phases of the reaction dynamics are thoroughly analysed, from the fast nucleon emission to the mid-rapidity fragment formation up to the dynamical fission of the spectator residues. Simulations have been performed with an increasing stiffness of the symmetry term of the EOS. Some differences have been noticed, especially for the fragment charge asymmetry. New isospin effects have been revealed from the correlation of fragment asymmetry with dynamical quantities at the freeze-out time. A series of isospin sensitive observables to be further measured are finally listed.

The excited nuclear systems formed in heavy ion collisions can be studied from a thermodynamical point of view. Charged finite systems have different behaviors with respect to infinite ones. After experimental selection of such equilibrated systems the extraction of thermodynamic coordinates is performed. Different signals compatible with a liquid-gas phase transition have been obtained. In particular a bimodal distribution of the asymmetry between the first two heaviest fragments is presented. Abnormally large fluctuations, which in thermodynamic equilibrium are associated to a negative branch of the heat capacity give indications of a first order phase transition. Perspectives for new generation experiments are indicated.

Since January 2003, the new 4π detector CHIMERA is operational at Laboratori Nazionali del Sud in Catania. The device was designed to study multifragmentation at Fermi energy (10 MeV/nucleon < E/A < 100 MeV/nucleon). Good identification of light charged particles and fragments allow to perform careful investigations of the reaction mechanism. During 2003 and 2004 different experiments were accomplished in the framework of an international collaboration. Triggered by recent increasing interest for isospin physics and future facilities with radioactive beams, in 2006-2007 CHIMERA will be upgraded by a suitable pulse shape analysis in silicon detectors, so that the present identification performance of the apparatus will be extended. CHIMERA fostered the interest of researchers for new developments in the field of particle identification and innovative signal processing methods. In this paper, a report of this activity is given and the experimental capability of the apparatus is illustrated.

The evolution of the GDR γ yield as a function of excitation energy has been investigated in nuclei of mass A ≈ 126 - 136 through the reactions ¹¹⁶Sn + ¹²C at 17 and 23A MeV and the reaction ¹¹⁶Sn + ²⁴Mg at 17A MeV. Hot nuclei produced in incomplete fusion reactions span an excitation energy range between 160 and 290 MeV. Gamma-rays were detected with MEDEA array in coincidence with residues detected in MACISTE. The evolution of the GDR parameters has been investigated as a function of the linear momentum transferred to the fused system. The analysis of the γ spectra and their comparison with CASCADE calculations is presented. A comparison with the gamma spectra measured in the reaction ³⁶Ar + ⁹⁸Mo at 37A MeV at higher excitation energy is presented. A progressive reduction of γ multiplicity with respect to predictions for 100% of the Energy Weighted Sum Rule is observed above 200 MeV excitation energy.

Experiments measuring muon pairs have played an important role in the SPS heavy-ion program since its very beginning, in 1986. I start by shortly reviewing the present situation in this field. Then, I describe the NA60 experiment, that has been designed in order to answer specific questions which remained open after the previous SPS experiments. NA60 has studied Indium–Indium collisions in 2003 and proton-nucleus in 2004. The data analysis is presently ongoing. Preliminary results on J/ψ suppression and on the study of low-mass resonances (ø, ω) in In-In collisions will be shown. Prospects for the future will also be shortly discussed.

We analyze correlation functions of charmonia at finite temperature (T) on anisotropic lattices using the maximum entropy method (MEM). It is shown that J/ψ and η_c survive as distinct resonances in the plasma even up to T ≃ 1.6T_c and that they eventually dissociate between 1.6T_c and 1.7T_c (T_c is the critical temperature of deconfinement). This suggests that the deconfined plasma is non-perturbative enough to hold heavy-quark bound states. The significance of this result in RHIC physics is also discussed.

Head-on collisions between ultrarelativistic heavy nuclei are believed to provide the extreme conditions of energy densities sufficient for the transition of hadronic matter to a short-lived state, called Quark-Gluon Plasma (QGP), where quarks are no longer confined within the nucleon. The forthcoming Large Hadron Collider (LHC) at CERN, scheduled to start commissioning during 2007, will be the ultimate facility for searching QGP. Complementary to the CMS and ATLAS experiments whose physics programmes focus on the search of the Higgs particle and super-symmetric particles in p-p collisions, the design of the ALICE experiment (A Large Ion Collider Experiment), has been optimized to study nucleus-nucleus collisions at LHC energies via a simultaneous measurement of many different observables. The ALICE setup comprises a multipurpose complex of tracking and particle-identification devices installed in a large solenoidal magnet and a muon detection arm in the forward rapidity region. Construction status and anticipated performance of the main ALICE sub-detectors will be discussed.

Hadronic matter under extreme conditions have drawn strong attentions, in particular, with many interesting results provided from RHIC. In this article, a selected number of recent results from RHIC are presented and their implications are discussed with main focus on the global aspects of hot and dense matter.

The objective of the DEAR (DAΦNE Exotic Atom Research) and the coming SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) experiments is an eV precision measurement of the K_α line shift and width, due to the strong interaction, in kaonic hydrogen and a similar measurement - the first one - in kaonic deuterium. The final aim is a precision determination of the antikaon-nucleon isospin dependent scattering lengths, which allows to better understand the chiral symmetry breaking scenario in the strangeness sector. DEAR has performed the most precise measurement up to now on kaonic hydrogen at the end of 2002. It is for the first time that the K-complex could be clearly identified. The obtained result is presented in this paper. An eV precision measurement of kaonic hydrogen and kaonic deuterium is foreseen in the framework of the newly started SIDDHARTA project, which continues the DEAR scientific line.

Chemical properties of the transactinide element, rutherfordium (Rf), produced in the reaction ²⁴⁸Cm(¹⁸O,5n) have been studied at an atom-at-a-time scale. Ion-exchange experiments of Rf together with the lighter homologues in the periodic table of the elements, group-4 elements Zr and Hf, in hydrofluoric acid solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, we have observed an unexpected chemical behavior of Rf; the fluoride complex formation of Rf is significantly different from those of the homologues. Characteristics of the complexing strength of the Rf fluoride are briefly discussed by comparing with those of Zr and Hf and also with theoretical predictions by relativistic molecular density-functional calculations.

The only three existent kaonic helium X-ray transition measurements at present are referring to the transitions to 2p level. These measurements are more than 30 years old and the obtained results, affected by big errors, are much larger than those predicted by optical models. It is thought that the optical model is inadequate, due to the presence of the ∧(1405) resonance, not properly taken into account. Because the nucleons in the helium nucleus are tightly bound, the effective energy of the K−p interaction (1432 MeV at threshold) is in helium much closer to the energy of the resonance than in other nuclei. It is then planned to measure the kaonic helium X-ray transitions to the 2p level in the framework of the SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) experiment, at the DAΦNE collider of Frascati National Laboratories, and to confirm or not the discrepancy reported by the previous experiments with a much smaller error.

Selected results following the first analyses of the data collected during the first run of FINUDA at DAΦNE will be presented and discussed. They concern the spectroscopy of , for which a considerable production of the core excitation states in reaction was observed for the first time and the evidence for a K−pp deeply bound state, observed for the first time with the invariant mass method. Finally, the perspectives of Hypernuclear Physics at a machine with a luminosity increased by at least one order of magnitude will be outlined.

Recently, we have performed an experimental search for deeply bound kaonic states by the kaon absorption reaction at rest in a liquid helium target. We observed very distinctive mono-energetic peak formation in a proton missing-mass spectrum. We denote it as a strange tribaryon, S⁰(3115), with baryon number 3, charge 0, isospin 1 and strangeness -1. If we attribute the mono-energetic peak to the formation of a deeply bound kaonic state, the separation energy of the kaon should be as deep as about 200 MeV. In the present paper, we will overview the present experimental data, and discuss the experimental program for the near future.

The first “systematic” study of 1 p shell hypernuclei with electromagnetic probes has started in Hall A at Jefferson Lab ⁵. The aim is to perform hypernuclear high resolution spectroscopy by the electroproduction of strangeness on four 1p-shell targets: ¹²C, ⁹Be, ¹⁶O, ⁷Li. The first part of the experiment on ¹²C and ⁹Be has been performed in 2004, the second part (¹⁶O and ⁷Li) is scheduled for June 2005. To overcome the major experimental difficulties, namely the low counting rate and the challenging Particle IDentification (PID), two septum magnets and a Ring Imaging CHerenkov (RICH) detector had to be added to the existing apparatus. After underlining the particular role the electroproduction reaction plays in hypernuclear physics we describe the challenging modifications of the Hall A apparatus. Preliminary results on ¹²C and ⁹Be are presented.

No abstract received.

Experimental efforts to nuclear astrophysical problems by the direct method are discussed including our new data for the explosive hydrogen burning process. We first present our new extensive, low-energy in-flight RI beam separator CRIB, which has been installed primarily for nuclear astrophysics. This is delivering RI beams of 10⁶ pps for some ions and will be increased by one or two orders of magnitudes in near future. Two experiments performed with CRIB are discussed. One of the most crucial stellar reactions ¹⁴O(α,p)^l7F for the onset of the high-temperature rp-process was directly investigated and the transitions through the states at around 6.2 MeV in ¹⁸Ne were first observed, confirming the importance of the process predicted before. The reaction leading to the first excited state in ¹⁷F was also found to have a considerable contribution. A proton resonance search experiment of ²³Mg + p was also discussed, which is a part of our series of resonance search studies relevant to the early stage of the rp-process.

The Trojan Horse Method allows for the measurements of cross sections in nuclear reactions between charged particles at astrophysical energies. The basic features of the method are discussed and recent applications are presented. Information on the electron screening potential for various reactions is also obtained by comparison with direct measurements.

The excitation function of the ⁸Li(α, n)¹¹B reaction was measured in the energy region of E_cm = 0.7 MeV − 2.6 MeV by using a highly efficient detector system and a highly pure low-energy ⁸Li–beam. The obtained reaction cross section is roughly 1.6 times smaller than the one by a previous inclusive measurement. The excitation function of the ⁸Li(α,n)¹¹B to the ¹¹B ground state and the excitation energy spectrum in the residual nucleus ¹¹B are also shown.

It is known that the chemical elements and their isotopes were created by nuclear fusion reactions in the hot interiors of remote and long-vanished stars over many billions of years¹. The present picture is that all elements from carbon to uranium have been produced entirely within stars during their fiery lifetimes and explosive deaths. The detailed understanding of the origin of the chemical elements and their isotopes combines astrophysics and nuclear physics, and forms what is called nuclear astrophysics. In turn, nuclear reactions are at the heart of nuclear astrophysics: they influence sensitively the nucleosynthesis of the elements in the earliest stages of the universe and in all the objects formed thereafter, and control the associated energy generation, neutrino luminosity, and evolution of stars. A good knowledge of the rates of these fusion reactions is essential to understanding this broad picture. Some of the most important experimental techniques to measure the corresponding cross sections, based both on direct and indirect methods, will be described in this paper.

A heavy ion medical accelerator HIMAC was completed in 1993 at National Institute of Radiology Sciences, and clinical trials for cancer therapy were started with carbon-ions in the next year. The rationale for use of the carbon-ion for cancer therapy lies in the great advantages over photon or low-LET radiations, those are dose localization, higher ability to kill cells even if they are hypoxic. About 2,000 patients were treated until August 2004. HIMAC has been working with excellent stability and reliability since after the beam commissioning.

The study of a possible solution for a target system with a high intensity (up to 10 mA) proton primary beam, aimed at the production of exotic nuclei as a result of high energy fissions in ²³⁸U, is reported. The work is inserted in the framework of the SPES project (Study for the Production of Exotic Species) of the Legnaro INFN Laboratories (Italy). An ideal configuration with the low energy primary beam (E<50 MeV) directly impinging on a UC₂ target device has been here considered. The isotopes fragments yields and the power depositions have been studied by means of the Monte Carlo code MCNPX as a function of the primary beam energy. The proposed configuration has been analyzed from a thermal point of view. A parameterization of the disk radius has also been performed.

A well established activity of the group in the field of applied nuclear physics was present in Florence already since the Eighties. This activity was carried out at an accelerator laboratory based on a single-ended 3 MV Van de Graaff. In this paper first I will explain the main features of Ion Beam Analysis (IBA) techniques and I will describe the experimental set-up at our laboratory; then I will give some examples of our work to show which kind of information may be obtained both in cultural heritage and environment field; finally, I will present the new INFN LABEC Laboratory in Florence.

In order to analyze hydrogen content in magmatic samples nuclear microbeam irradiation system with elastic recoil coincidence spectrometry (ERCS) has been developed. This new method of analysis is only sensitive for hydrogen. The analysis is non-destructive and quick in which depth profile of hydrogen concentration can be deduced from measured energy spectrum.

A new design of magnetic spectrometer, MAGNEX, is under construction for the INFNLNS, Catania. The unique features of MAGNEX are its solid angle of acceptance (51 msr), momentum acceptance (±10%), overall momentum resolution of 1/2000 and mass resolution of 1/200, together with a focal plane detector having a low detection threshold (0.5 MeV/A). The spectrometer is based on a 55° bend angle dipole magnet with mean radius of 1.6 m. It is designed for a maximum rigidity of 1.8 Tm. Despite the large acceptance, a good momentum resolution is achieved by a combination of careful ion-optical design and software ray-reconstruction. The latter depends on three things: the availability of detailed field maps, the precise measurement of position and angle by the detection system, and the solution to high order of the equation of motion based on, in our case, the program COSY INFINITY. The MAGNEX spectrometer, connected with the broad choice of both stable and radioactive beams at the LNS, will provide new opportunities for, e.g., spectroscopy of weakly-bound nuclei by direct reactions, reaction mechanisms with large isospin and nuclear astrophysics.

We have been developing three-dimensional position sensitive Germanium semiconductor detector using an Artificial Neural Network(ANN). For training training of the ANN, pulse shape sampling was performed using flash-ADCs. In order to reduce the time for sampling, several method were proposed and tested.

New accelerator facilities for radioactive-ion beams and high-intensity stable beams will start operation in a few years. They will provide interesting opportunities for exploring unknown territories of the nuclear landscape but the harsh experimental conditions require the construction of a new generation of detector arrays for gamma-ray spectroscopy built fully from germanium detectors and based on the emerging technique of gamma-ray tracking. The “Advanced GAmma Tracking Array” (AGATA), proposed in Europe, will be built out of 180 highly segmented high purity germanium crystals operated in position sensitive mode by means of digital data techniques and pulse shape analysis of the segment signals. AGATA will be capable of measuring gamma radiation in a large energy range (from ~10 keV to ~ 10 MeV), with the largest possible photopeak efficiency (25 % at M_γ = 30) and with a good spectral response. In particular, its very good Doppler correction and background rejection capabilities will allow to perform “standard” γ-ray spectroscopy experiments using fragmentation beams with sources moving at velocities up to β ~ 0.5. The talk reviews the status of development of the γ-ray tracking technique and the present design of AGATA.

The use of exotic beams of low intensity asks for high efficiency experimental set-ups. Light charged particles are important tools in studying nuclear reactions with exotic beams, mainly to study direct reactions in inverse kinematics and to develop powerful ancillary detection systems to be coupled to gamma arrays. Large solid angle coverage, precise measurement of energy, timing and scattering angle are the main features of these new generation detectors. The number of electronic channels associated to these high segmentation detectors is quite large: in the order of 1000 or more. To reduce the amount of electronic components, ASIC technology is required and in the next future an effort will be devoted to design new high-density electronics with adequate resolution and dynamic range. Several actions to coordinate the efforts at European level are on the way. The aim is to develop new instrumentation and related electronics suitable to be used in the above experiments. Italian Nuclear Physics community actively participate to design new instrumentation and to perform the preliminary tests.

The low intensity (about 10⁵-10⁶ pps) of the presently available RNBs (Radioactive Nuclear Beams) requires detection apparatuses with large solid angle coverage and high granularity. Moreover, the utilization of highly segmented detectors needs unconventional read-out systems appositely designed and the development of electronic boards making use of highly miniaturized and integrated circuitry (ASIC chip). The EXODET (EXOtic DETector) apparatus has been designed and constructed following these guide lines. It consists of large-area silicon detectors segmented in 100 strips on a single side. The particle energy loss information is obtained from the unsegmented side using standard electronic chains, while for the read-out of the incident position information we found suitable a chip already developed for high-energy particle physics experiments. EXODET has been already successfully used in exotic nuclei experiments devoted to the study of the scattering of ¹⁷F on a ²⁰⁸Pb target and of ¹¹Be on a ²⁰⁹Bi target at energies around the Coulomb barrier, performed at the Argonne National Laboratory (USA) and at the RIKEN Laboratory (Japan), respectively. The development of these modern and compact detection systems opens new and interesting perspectives for experimentation with RNBs.

An application of digital sampling techniques is presented which can greatly simplify experiments involving subߝnanosecond time-mark determinations and energy measurements with nuclear detectors, used for Pulse Shape Analysis and Time of Flight measurements in Heavy-Ion experiments. In this work a 100 MSample/s, 12 bit analog to digital converter has been used. A modular system well suited for applications to large detector arrays is also described. Examples of application of these devices to various detector types (i.e. silicon, germanium, CsI(Tl), Gas, …) in experiments involving particle identification via Pulse Shape analysis and Time of Flight measurements are presented. The achievable digital timing resolution is much smaller than the converter sampling period, for example a resolution of 100 ps FWHM has been obtained with a 12 bit, 100 MSample/s converter. The system is suited for applications to large detector arrays and to different kinds of detectors.

We are starting to develop a next generation DAQ system which consists of autonomous data taking modules distributed over DAQ network. The each module is tightly connected to its partner detector and has memorizing capability of the detector’s characteristic. The framework of present DAQ systems for nuclear physics experiments which stands on modular structure is not changed for 30 years, because it is universal and flexible. Advanced research works require more precise measurement and more detector channels, which caused difficulty of complicated cabling, increasing noise etc. The biggest difficulty is time consumed calibration work which is mandatory on each experiment and makes the analysis period so long. On the other hand, IT (Information Technology) field is growing so quickly and we can take fast CPU, big memory, network technology etc. with so small expense. It is no wonder to imagine autonomous data taking modules distributed over DAQ network as more universal and flexible DAQ system.

A dedicated beam line has been installed at the Naples tandem accelerator aiming to verify the homogeneity of nTD silicon detectors. The experimental technique relies on pinhole proton beams, x- and y-translations by remotely controlled stepping motors, tuning the bombarding energy to explore different (z) depths. Comparing the pulses delivered by a special preamplifier, which allows studying current signals induced by ionizing particles, allows checking the detector homogeneity point by point.

An overview of the “Laboratorio dell’Acceleratore” (accelerator laboratory), which hosts a 3 MV tandem accelerator, is presented.

The experimental activity in the field of the Nuclear Physics is briefly outlined: about 470 Italian researchers are involved in 32 experiments, supported by INFN and carried out both at national and international facilities.

The EXCYT facility (EXotics with CYclotron and Tandem) at the INFN-LNS is based on a K-800 Superconducting Cyclotron injecting stable heavy-ion beams (up to 80 MeV/amu, 1μA) into a Target-Ion Source assembly (TIS) to produce the required nuclear species, and on a 15 MV Tandem for post-accelerating the radioactive beams. Since the previous TIS had been radically modified in its shape, dimensions and geometry, it became necessary to verify off and on-line the TIS behaviour with respect to the mechanical and thermal stresses at 2300 K as well as to obtain information about the production and the release processes. In order to save time, this was successfully achieved in May 2003 at the SIRa test-bench of SPIRAL, GANIL, by shooting a ¹³C primary beam (60 MeV/amu) on a ¹²C target under the same operational conditions that will be initially used at EXCYT. The measured yields and production efficiencies for ^8,9Li were compatible with the ones obtained at SIRa. We decided to deliver ⁸Li as the first EXCYT radioactive beam taking into account the requests and the first results obtained by the Big Bang collaboration as well as the availability of the large magnetic spectrometer MAGNEX in late 2004. The commissioning of the EXCYT facility is foreseen by the beginning of 2005 together with the start of nuclear experiments programme.

High Energy Accelerator Research Organization (KEK) and Japan Atomic Energy Research Institute (JAERI) are jointly constructing the Tokai Radioactive Ion Accelerator Complex (TRIAC) facility at Tokai site of JAERI . This facility in a final goal consists of an Isotope Separator On-Line (ISOL), a charge-breeding 18 GHz ECR (CB-ECR), and a linac complex such as a split-coaxial RFQ (SCRFQ-) linac, an interdigital-H type (IH-) linac, three rebunchers, and a superconducting (SC-) linac. Radioactive nuclei are produced with using primary beams from the 20 MV Tandem accelerator. The output RNB energy is variable between 0.1 to 8 MeV/u. At the end of 2004, the TRIAC facility will open up the RNB science with 1.1 MeV/u beams supplied from IH-linac. The higher energetic (5-8 MeV/u) RNBs will be available in the near future.

At LNL it has been proposed an Advanced Exotic Ion Beam facility, that will allow a frontier program in RIBs Physics. In particular beams of neutron rich nuclei in the medium heavy mass region will be produced. The structure properties of these nuclei are interesting also for the understanding of the astrophysical problem of the stellar nucleosyntesis. We illustrate here the concept of the SPES facility, and how this proposal is interconnected with the longer term European project EURISOL. The first part of the SPES facility, SPES-1, is presently under construction.

Since 1990 the RIKEN Accelerator Research Facility has provided variety of fast radio-isotope (RI) beams based on the projectile-fragmentation scheme. Various studies have been made and are in progress using these exotic beams, the intensities of which are highest in the world for many light unstable nuclei. The RIKEN RI Beam Factory, which is now being built, will greatly extend the region of study to more exotic and heavier nuclei. The first beam is expected in the end of the year 2006. Installations of experimental equipments are being considered to fully exploit the new opportunity of nuclear research.

LIST OF PARTICIPANTS.

AUTHOR INDEX.