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Elemental composition of the fine (PM2.5) and coarse (PM2.5-10) fraction of atmospheric particulate matter was measured at hourly time resolution by the use of a “streaker” sampler during a winter period at a Central European urban background site in Warsaw, Poland. A combination of multivariate (Positive Matrix Factorization), wind- (Conditional Probability Function) and trajectory-based (Cluster Analysis) receptor models, was applied for source apportionment. It allowed for identification of 5 similar sources in both fractions, including sulfates, soil dust, road salt, traffic- and industry-related sources. Another 2 sources, i.e., Cl-rich and wood and waste combustion, were identified in the fine fraction solely. In the fine fraction, aged sulfate aerosol related with emissions from solid fuel combustion in the residential sector located outside the city was the largest contributing source to fine elemental mass (44 %), while traffic-related sources, including soil dust mixed with road dust, road dust, as well as exhaust and non-exhaust traffic emissions, had the biggest contribution in the coarse elemental mass (together accounting for 83 %). Regional transport of aged aerosols and more local impact of the rest of identified sources played a crucial role in aerosol formation over the city. In addition, 2 intensive Saharan dust outbreaks were registered on 18th February and 8th March 2016. Both episodes were characterized by long-range transport of dust at 1 500 m and 3 000 m over Warsaw, as well as the concentrations of the soil component being 7 (up to 3.5 µg m−3) and 6 (up to 6.1 µg m−3) times higher than the mean concentrations observed during non-episodes days (0.5 µg m−3 and 1.1 µg m−3) in the fine and coarse fraction, respectively. The set of receptor models applied to the high time resolution data allowed to follow in detail the daily evolution of the aerosol elemental composition and to identify distinct sources contributing to the concentrations of different PM fractions, as well as revealed “multi-faces” of some elements, having diverse origin in the fine and coarse fraction. The hourly resolution of meteorological conditions and air mass back trajectories empower to follow transport pathways of the aerosol as well.

The elastic scattering in the reaction $$^{7}$$ 7 Li+$$^{208}$$ 208 Pb was investigated in the bombarding energy range from 25 to 39 MeV. The real and imaginary parts of the optical potential were analyzed by using a phenomenological potential. A dispersion relation analysis is presented in order to investigate the threshold anomaly effect. It is concluded that $$^{7}$$ 7 Li has an intermediate behavior between the tightly bound nuclei such as $$^{16}$$ 16 O and the loosely bound nuclei such as $$^{6}$$ 6 Li where the lack of the threshold anomaly is unambiguously observed. Reaction cross sections are also extracted from the elastic scattering data and its comparison with the ones of other systems has been performed to draw hints on the effect of the breakup channel.

The correct determination of the X-ray peak areas in PIXE spectra by fitting with a computer program depends crucially on accurate parameterization of the detector peak response function. In the Guelph PIXE software package, GUPIXWin, one of the most used PIXE spectra analysis code, the response of a semiconductor detector to monochromatic X-ray radiation is described by a linear combination of several analytical functions: a Gaussian profile for the X-ray line itself, and additional tail contributions (exponential tails and step functions) on the low-energy side of the X-ray line to describe incomplete charge collection effects. The literature on the spectral response of silicon X-ray detectors for PIXE applications is rather scarce, in particular data for Silicon Drift Detectors (SDD) and for a large range of X-ray energies are missing. Using a set of analytical functions, the SDD response functions were satisfactorily reproduced for the X-ray energy range 1–15 keV. The behaviour of the parameters involved in the SDD tailing functions with X-ray energy is described by simple polynomial functions, which permit an easy implementation in PIXE spectra fitting codes.

One-dimensional and three-dimensional dynamical fission calculations based on Langevin equations are performed for the compound nuclei 194 Pb, 200 Pb, 206 Pb, 182 Hg, and 204 Hg to investigate the influence of the compound nucleus isospin on the prescission particle multiplicities and on the fission fragment mass–energy distribution. It is found that the prescission neutron, proton, and alpha particle multiplicities have approximately the same sensitivity to the dissipation strength for a given nucleus. This is at variance with conclusions of recent papers. The sensitivity of the calculated prescission particle multiplicities to the dissipation strength becomes higher with decreasing isospin of fissioning compound nucleus, and the increase of prescission particle multiplicities could reach 200%, when the reduction coefficient of one-body viscosity k s increases from 0.1 to 1, for the most neutron deficient nuclei considered. The variances of fission fragment mass and kinetic energy distributions are less sensitive to the change of dissipation strength than the prescission light particle multiplicities. A comparison to experimental data concerning 200 Pb nucleus is also presented.

At the new 3 MV Tandetron accelerator of the LABEC laboratory of INFN in Florence, an external beam facility fully dedicated to measurements of elemental composition of atmospheric aerosol has been installed. The experimental set-up hitherto used for this kind of applications has been upgraded with the introduction of a silicon drift detector and of a beam current monitor system based on the backscattering of protons on the extraction window. The new facility will be presented, together with some methodological results obtained so far for the analysis of airborne particulate matter samples collected on quartz fiber filters.

The composition of airborne particulate matter in Montelupo Fiorentino (a small town about 20 km west of Florence characterized by the presence of a large number of ceramic and glass factories) was studied by means of continuous and sequential sampling, ion beam analysis (IBA) techniques and statistical methods. The aerosol PM 10 fraction was collected on a daily basis for about 9 months (September 2002-June 2003). To investigate the elemental size distribution, for a shorter period (about 3 weeks) we collected PM 10 , PM 25 and PM 1 simultaneously. A continuous streaker sampler was also used, which allows the study of the aerosol composition with 2 h time resolution. Mass concentrations were obtained using an analytical balance. The elemental analysis was performed at the INFN accelerator laboratory at the Physics Department of Florence University by particle-induced x-ray emission and particle elastic scattering analysis (the latter implemented for this campaign). The use of the two techniques allowed a complete reconstruction of the gravimetric mass. An absolute principal component analysis showed industrial sources to be, on average, the main contributors to PM 10 mass; however, the weight of the 'soil' source (connected to local soil re-suspension and to long-range Saharan transport episodes) becomes dominant during some of the days when the 50 μg m -3 limit is exceeded.

Pre-scission and post-scission multiplicities of neutrons and alpha particles have been simultaneously measured for the fission-like reactions of 340 MeV 28 Si on 232 Th. Dynamical model calculations using HICOL code predict that about 90% of the observed events are of quasi-fission type while the remaining 10% are from compound nucleus fission decay. Moving source fits were carried out to the observed neutron and alpha particle spectra, measured at different angles with respect to the fragment directions. The pre-scission and post-scission neutron multiplicities are deduced to be 8.7±2.0 and 9.4±2.0, respectively. The corresponding multiplicity values for alpha particles are found to be 0.22±0.08 and 0.1±0.03. From the measured post-scission neutron multiplicity, it is inferred that about 65±20 MeV of the initial excitation energy remains at scission. This may be compared to the value of 85±30 MeV estimated from PACE2 statistical model calculations, adjusted to reproduce the measured pre-scission neutron multiplicity. From a comparison of the Statistical Model predictions with the measured pre-scission neutron multiplicity, the fission delay is estimated to be of 5 +7 −3 ×10 −20 s which overlaps with the average duration of fission-like process from the contact to the scission point (2×10 −20 s) as determined from HICOL-based dynamical calculations. For the delay time deduced as above, the pre-scission alpha particle multiplicity calculated by the PACE2 code is about a factor two larger than the experimental one, demonstrating the difficulties in modelling the alpha particle emission from highly elongated shapes that characterize the fissioning system from the contact point to scission.

A 4pi light charged particle spectrometer, named 8pLP, is in operation at the Laboratori Nazionali di Legnaro (Italy) for the study of the reaction mechanisms produced in low-energy heavy-ion reactions. The spectrometer has recently been used in a study of fission dynamics that involves the detection of light charged particles in the fission and evaporation residue channel in a system of intermediate fissility, as well as in a study of multinucleon transfer to heavy target. Data on the system 240 MeV S-32 + Mo-100 are presented. Dynamical effects extracted as a consequence of the comparison of the data to the statistical model calculations are discussed.

Light particles in coincidence with evaporation residues and heavy fragments have been measured by a 4pi charged-particle detector at the INFN Laboratori Nazionali di Legnaro (Padua) for the 240 MeV S-32+Mo-100 reaction leading to the Ce-132 composite system at 152 MeV of excitation energy. Energy spectra of the alpha-particles in coincidence with fission fragments were extracted for many correlation angles both in plane and out of plane. A prominent out-of-plane emission was observed, consistent with the pattern for the near-scission emission. From the fit to the spectra, the pre-scission alpha-particle multiplicity of 0.040 +/- 0.006 was obtained. This value is reproduced by the code PACE2 without the inclusion of a delay time for fission. The presence of fast fission, which could be responsible for this result, is discussed.

The reaction 120 MeV 19 F + 181 Ta has been studied by charged particle-γ-ray coincidence techniques. An incomplete fusion component has been identified in coincidence with 192,191Hg residues which are populated in the αxn channels. Evidence has been found that the feeding of high spin states in final residues is enhanced when the coincidence is required with alpha particles emitted at forward angles, where the incomplete fusion component dominates.

A 4π detection system sensitive to light charged particles is being developed at the Laboratori Nazionali di Legnaro (LNL) for the study of the reaction mechanisms produced in heavy-ion collisions at energies up to 20 AMeV. The 8πLP apparatus is a telescope assembly characterized by large solid angle (90% of 4π) and high granularity (262 modules). Particle identification at low energy is enhanced by combining Δ E – E , TOF and PSD techniques. Thresholds for particle identification range from 1 MeV for protons and 3 MeV for alpha particles to about 2–3 AMeV for C ions. The system is fully operational for experiments.

We have measured the high-energy γ-ray spectra from the fusion reactions 130 MeV16O +98Mo and 240 MeV48Ti +64Ni, populating the114Sn and112Sn compound nuclei at the excitation energy of 110 MeV. The comparison of the spectra shows a ~36% enhancement of the α-ray yield in the Giant Dipole Resonance region (Eγ > 8 MeV) when the 16 O-induced reaction is considered. This enhancement is interpreted as due to entrance channel effects related to theN/Z asymmetry between the target and the projectile.

The alpha-particle emission from the Si-28+Er-170 fusion-evaporation reaction at 165 and 185 MeV has been measured and compared with published data relative to the pre-scission emission in the same reaction. The spectra in the two channels exhibit nearly the same shape in the low energy region, whereas in the high energy region the spectrum for the fusion-evaporation case features a larger apparent temperature. The interpretation of the difference in shape between the two decay channels is based on statistical model calculations which account for the effects due to the different length of the decay chain. Statistical model calculations with standard parameters describe well the gross features of the alpha particle spectra in the fusion-evaporation channel and the proton spectra in the pre-scission channel. On the contrary, the model predictions seem to overestimate by similar or equal to 2 MeV the emission barrier for the alpha particles in the pre-fission channel. This effect is ascribed to the larger elongation of the nucleus during the fission process. An average axis ratio b/a similar to 2 for the emitter is suggested.

A 4/spl pi/ detection system sensitive to light charged particles is being developed at the Laboratori Nazionali di Legnaro (LNL) for the study of the reaction mechanisms produced in heavy ion collisions at energies up to 20 AMeV. The 8/spl pi/LP apparatus is a telescope assembly characterized by large solid angle (90% of 4/spl pi/) and high granularity (262 modules). Particle identification at low energy is obtained by combining /spl Delta/E-E, TOF and PSD techniques. Each telescope is made of a 300 /spl mu/m passivated silicon detector and a 15 mm (or 5 mm) CsI(Tl) crystal with photodiode readout. Thresholds for particle identification range from 1 MeV for protons and 3 MeV for alpha particles to about 2-3 AMeV for C ions. A low-cost trigger and readout bus system has been developed to cope with the large number of parameters and the high counting rate. The system will be fully operational for experiments in the summer of 1997.

Light particles spectra in coincidence with fission fragments have been measured for the reaction 187 MeV 37 Cl on 120 Sn populating 157 Ho compound nuclei at the excitation energy E x = 85 MeV. The experimental neutron pre-scission multiplicity for symmetric splintting is two times larger than the statistical model estimate. The experimental multiplicity is reproduced by calculations in which a fission delay, in agreement with systematics, is introduced. This empirical fission delay produces a sizeable increase, with respect to the standard statistical model estimate, of the survival probability against fission for nuclei with angular momentum around J ∼ h . The importance of this effect in the population of superdeformed and hyperdeformed structures in the evaporation residues is discussed.

High-energyγ-rays from the32S+74Ge reaction at 210 MeV bombarding energy were measured in coincidence with light charged particles detected in a large area hodoscope. Experimental results show that energeticγ-rays in coincidence with light charged particles are essentially emitted in the compound nucleus decay. The parameters of the giant dipole resonance (GDR) have been extracted from alineshape analysis of the experimentalγ-ray spectrum. The derived values of mean energyED, widthΓ and strengthS are in good agreement with results from previous experiments on Sn isotopes obtained by using different experimental techniques.

The reactions 10 MeV/u 86 Kr + 76 Ge and 27 MeV/u 16 O + 150 Sm were used to form the same composite system with A ∼ 160 at about 300 MeV of excitation energy, as derived from measurements of both the linear momentum transfer and the neutron multiplicity. The comparison of the evaporative spectra of the α particles in coincidence with evaporation residues does not show evidence for effects related to the entrance channel of the reaction, such as those predicted by dynamical models.

The emission of high-energyγ-rays in the deexcitation of hot40Ca and39K nuclei formed in heavy-ion fusion reactions at excitation energyEx ∼ 90 MeV has been studied. The high energyγ-rays were measured in coincidence with evaporation residues or light charged particles. Theγ spectrum from the self-conjugated compound nucleus40Ca shows an appreciable yield suppression in the Giant Dipole Resonance (GDR) energy region with respect to the39K, due to isospin selection rules in the dipoleγ-decay. The spectral line shapes of theγ spectra are well reproduced by using a statistical code which treats explicitly the isospin quantum number in evaluating level densities and transmission coefficients. The GDR parameters determined from the present coincidence measurements are in good agreement with the systematic in theA ∼ 40 mass region at lower bombarding energy based on the analysis of inclusive spectra.

The multiplicities of γ-rays emitted in the giant dipole resonance decay of 200 Pb have been measured in coincidence with both evaporation residues and fission fragments. The experimental data have been compared with results of statistical calculations which take into account dynamical fission hindrance. The fission probability distribution has been determined as a function of excitation energy.

The evaporative decay of the compound nucleus 139Eu produced by the 180MeV 32S + 107Ag reaction was studied with the aim to test the empirical isospin expressions of the level density, recently appeared in the literature. We measured light charged particle spectra and angular correlations in coincidence with the evaporation residues and the invariant velocity distribution of the evaporation residues. In addition, an independent experiment was performed on the reaction 32S + 109Ag at the same incident energy. Evaporation residue angular distribution was measured and the fusion-evaporation cross-section was determined. All the measured quantities are compared with the predictions of different level density prescriptions: a) isospin independence, b) a dependence from N - Z and c) a dependence from Z-Z0 as proposed by Al-Quraishi et al. Results show that the predictions of the Z-Z0 dependence are far off the experimental data for all the measured observables. Regarding the isospin independent prescription and the N - Z dependence, although no great differences appear between their predictions the N - Z prescription seems to better describe the experimental data.

Alpha particles and protons emitted in the 32S + 74Ge reaction at E = 160, 210, 259, 335 and 435 MeV were measured in coincidence with evaporation residues. The average inverse level-density parameter 〈 K 〉 for hot evaporation residues with A ∼ 100 was obtained by comparing the slope of the charged-particle spectra with the predictions from a full statistical model calculation. Spectral shapes are well reproduced by calculations using the standard values 〈K〉 = 7.5 MeV , except for alpha particles at the highest bombarding energy, which corresponds to an excitation energy ϵ = 2.2 MeV/nucleon . The present results are compared with other experimental investigations in the A ∼ 100 and A ∼ 160 regions and with predictions from theoretical models. Difficulties in extracting the nuclear temperature from the slope of the particle spectra for A ∼ 100 are discussed.

Light charged particle (LCP) emission in the evaporation residue (ER) and fusion fission (FF) channels have been studied for the 200 MeV 32S + 100Mo reaction, leading to 132Ce composite nuclei at E x =122 MeV. The main goal was to study the decay of 132 Ce on the basis of an extended set of observables, to get insights on the fission dynamics. The proton and alpha particle energy spectra, their multiplicities, ER-LCP angular correlations, ER and FF angular distributions, and ER and FF cross-sections were measured. The measured observables were compared with the Statistical Model (SM). Using standard parameters, the model was able to reproduce only the pre-scission multiplicities and the FF and ER cross-sections. The calculation was observed to strongly overestimate the proton and alpha particle multiplicities in the ER channel. Disagreements were also observed for the ER-LCP correlations, the LCP energy spectra and the ER angular distribution. By varying the SM input parameters over a wide range of values, it is shown that it is not possible to reproduce all the observables simultaneously with a unique set of parameters. The inadequacy of the model in reproducing the ER particle multiplicities is also observed analysing data from the literature for other systems in the A ≈ 150 and E x ≈ 100−200 MeV region. These results indicate serious limitations about the use of the SM in extracting information on fission dynamics.

Neutron spectra in coincidence with fission fragments have been measured for the 115 MeV 16 O + 144 Sm and 270 MeV 60 Ni + 100 Mo reactions, populating 160 Yb compound nucleus at E x ∼75 MeV excitations energy. The extracted pre-scission multiplicity for the 60 Ni + 100 Mo reaction is substantially larger than the statistical model prediction, demonstrating clearly that dynamical effects dominate even at low excitation energy.

The systems of intermediate fissility 132Ce and 158Er have been studied experimentally and theoretically in order to investigate the dissipation properties of nuclear matter. Cross sections of fusion-fission and evaporation residues channels together with charged particles multiplicities in both channels, their spectra, angular correlations and mass-energy distribution of fission fragments have been measured. Theoretical analysis has been performed using multi-dimensional stochastic approach with realistic treatment of particle evaporation. The results of analysis show that full one-body or unusually strong two-body dissipation allows to reproduce experimental data. No temperature dependent dissipation was needed.

The154Sm(28Si, Mg) and154Sm(16O, C) transfer reactions atE/B∼1.6 have been studied by means of fragment-γ-ray coincides. γ-ray spectra are dominated, for both reactions, by the yrast transitions from156,154Gd. The analysis of the energy loss spectra associated with156,154Gd, performed in the framework of a model for transfer reaction and the statical model for the sequential evaporation, suggests that the two Gd isotopes are produced by different reaction mechanisms. The analysis of γ-ray discrete lines for156Gd reveals different paths in the decay of excited primary products of the transfer reactions. The gamma-ray multiplicities are unexpectly similar for the two reactions. The complexity of the transfer processes is underlined.

γ-multiplicityMγ and missing charge ΔZ from fragment-fragment coincidences have been measured for fissionlike events in the reactions32S+58,64Ni at 160 and 180 MeV bombarding energies. The experimental data have been compared with a Monte Carlo simulation of the sequential decay of primary fragments assumed to be in thermal equilibrium. Statistical-model calculations have been performed with different assumptions on the spin distribution of the composite system decaying in two symmetric fragments. The experimentalMγ data are well described by model calculations with spin values inside the fusion region. Those spin values are close to the first moments of the angular-momentum distributions for fusion-fission of the compound nucleus as computed by statistical model using finite-range corrected fission barriers. Model calculations describe also well the experimental ΔZ values for the32S+58Ni reaction but overestimate the data relative to the64Ni target, evidencing difficulties in the complete reconstruction of the sequential decay of the reaction products.

The MAGIC telescope has been designed for the observation of Cherenkov light generated in Extensive Air Showers initiated by cosmic particles. However, its 17m diameter mirror and optical design makes the telescope suitable for direct optical observations as well. In this paper, we report about the development of a system based on the use of a dedicated photo-multiplier (PMT) for optical observations. This PMT is installed in the centre of the MAGIC camera (the so-called central pixel). An electro-to-optical system has been developed in order to transmit the PMT output signal by an optical fibre to the counting room, where it is digitized and stored for off-line analysis. The performance of the system using the optical pulsation of the Crab nebula as calibration source is presented. The time required for a 5 sigma detection of the Crab pulsar in the optical band is less than 20s. The central pixel will be mainly used to perform simultaneous observations of the Crab pulsar both in the optical and gamma-ray regimes. It will also allow for periodic testing of the precision of the MAGIC timing system using the Crab rotational optical pulses as a very precise timing reference. (c) 2008 Elsevier B.V. All rights reserved.

Charged particles and high energy \ensuremath{\gamma} rays from the decay of the $^{156}\mathrm{Er}$ compound nucleus populated at ${\mathit{E}}_{\mathit{x}}$=47 MeV excitation energy by the $^{12}\mathrm{C}$${+}^{144}$Sm and $^{64}\mathrm{Ni}$${+}^{92}$Zr reactions have been measured to study possible nonstatistical or entrance channel effects. The experimental spectra and published evaporation residue and neutron data are compared with statistical model calculations. The comparison shows that the statistical model with standard parametrization of level density and yrast lines describes reasonably well the bulk of experimental observables but not the shape of neutron spectra if account is taken of the enhancement factor for E2 transitions. The discrepancies between experimental data and model calculations are discussed.

The \ensuremath{\alpha} decay of Ru compound nuclei populated in $^{32}\mathrm{S}$ on $^{58}$,60,62,64Ni reactions at ${E}_{\mathrm{beam}=135\char21{}}$185 MeV has been studied. Experimental data have been compared with statistical model calculations performed with two different computer codes. The quality of the agreement between calculations and experimental data was found, in one case, to depend on the compound nucleus populated. Comparing the results from the two computer codes, deviations in the predicted cross sections are evidenced which are due to the different parametrization of nuclear properties employed in the calculations. Statistical model calculations describe well the shape of experimental spectra if account is taken of changes in the phase space available to the decaying nucleus which are related to the onset of deformations at high spins. Fission competition strongly determines the alpha-particle cross sections at the higher bombarding energies which are systematically underestimated by the model calculations if transmission coefficients computed from optical model potentials are used.

Fission and binary fragmentation of the excited nuclear systems of Z=116 and 124 were investigated using the reactions induced by {sup 80}Se beams on {sup 208}Pb and {sup 232}Th targets at bombarding energies ranging from 470 to 630 MeV. The mass and kinetic energy of the binary reaction products were reconstructed by measuring their velocities by the time-of-flight method and the angles of emission using multiwire proportional chambers. Total neutron multiplicities were measured in coincidence with the fragments, using an array of neutron detectors. The fragment mass-energy correlation was studied for the two systems. The average total kinetic energy (TKE) of fragments for the {sup 80}Se+{sup 208}Pb system agrees with earlier measurements and with Viola's systematics in the mass symmetric region for compound nucleus fission, whereas for the {sup 80}Se+{sup 232}Th system, the TKE values are significantly lower. This is also consistent with higher values of total neutron multiplicities observed for the case of {sup 80}Se+{sup 232}Th at comparable available energies. From an extrapolation of the measured total neutron multiplicities for the mass symmetric region to zero compound nucleus excitation energy, the average number of prompt neutrons expected to be emitted in the spontaneous fission of the superheavy Z=116 hasmore » been estimated to be {nu}{sub tot}{sup sf}=10{+-}2, which is consistent with the value derived for the same compound nucleus populated in the {sup 56}Fe+{sup 232}Th reaction in an earlier work. In the case of the {sup 80}Se+{sup 232}Th system, similar analysis was carried out by taking the average TKE from Viola's systematics for estimating the available energy for particle emission corresponding to compound nucleus fission. In this way, by extrapolating the observed neutron multiplicities to zero compound nucleus excitation energy, a value of {nu}{sub tot}{sup sf}=15{+-}2 was obtained for the spontaneous fission of the superheavy Z=124 nucleus. The increase in the average number of neutrons emitted in fission as a function of the atomic number of the nucleus in the superheavy mass region was confirmed by comparing the results of the present work with published data.« less

Fission dynamics in systems of intermediate fissility is under study with the 8πLP apparatus at the Laboratori Nazionali di Legnaro (Italy). Here we present some preliminary results for the composite system 132Ce at Ex=122 MeV, produced in the reaction 32S + 100Mo at Elab=200 MeV. Measured charged particle multiplicities in the evaporation residue and fission channels, and cross sections of the two channels have been compared to the predictions of a dynamical model based on three dimensional Langevin equations. The sizeable set of measured observables allowed to put severe constraints to the model. A good overall agreement is obtained assuming one body dissipation, which implies a fission delay in the range 15 – 25 ×10−21 s.

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.

The binary fragmentation of the excited superheavy system of Z=116 formed in the reaction 372 MeV {sup 56}Fe+{sup 232}Th has been investigated. The fragment masses and kinetic energies were determined through measurement of the fragment velocities by the time-of-flight method. Neutron spectra were measured in coincidence with the fragments at several angles with respect to the fragment direction, which were analyzed to deduce the total as well as the pre-scission neutron multiplicities. We analyzed the correlations between fragment mass and kinetic energy, gated and nongated by the coincidence with neutrons, to learn about the dynamics of the reaction with respect to the two-body exit channels. The events in the near-mass-symmetric valley region appear to receive a significant contribution from the asymmetric mode of fission of the superheavy compound nucleus Z=116, which can be due to the influence of the closed proton and neutron shells of Z=50 and N=82 in the light fragments. From the observed number of pre-scission neutrons, it is inferred that the time scales of the fissionlike reactions leading to near-mass-symmetric splits are rather large, of the order of several times 10{sup -20} s. The average number of prompt neutrons emitted in the spontaneous fission of such amore » superheavy nucleus is {nu}=(12{+-}1), as deduced from the neutron measurements.« less

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.

Fusion-evaporation reactions induced by $110\phantom{\rule{0.3em}{0ex}}\text{MeV}$ $^{11}\mathrm{B}$ and radioactive $^{11}\mathrm{C}$ on $^{87}\mathrm{Rb}$ targets have been studied by measuring evaporation residue--light particle coincidences. The proton to $\ensuremath{\alpha}$ particle ratio in each reaction has been derived and compared with predictions from statistical model calculations. These calculations account rather well for the experimental data, when a small empirical adjustment of the emission barrier is performed, in agreement with earlier results. No evidence is found for predicted temperature and isospin modification of the binding energies. The possibility of a further study of isospin and temperature dependent effects in fusion-evaporation reactions with radioactive beams is discussed.

The paper presents methodological innovations introduced in the characterisation of urban aerosol collected in Italy in a recent campaign. Two complementary ion beam analysis (IBA) techniques were used to analyse Nuclepore filters used in continuous streaker samplers to collect airborn particles in four Italian towns. Na to Pb elemental concentrations were obtained by particle induced X-ray emission (PIXE), while time of flight secondary ion mass spectrometry (ToF-SIMS) produced, on the same samples, time trends for several elements and molecular fragments. In addition, light attenuation measurements were used as a tracer for black carbon. The data produced by these three techniques was merged into a unique data set to address the characterisation of particulate matter sources. Correlations between elemental concentration trends (PIXE) and relative trends for molecular fragments (ToF-SIMS) and black carbon (light attenuation) have been studied by cluster and principal component analysis. (C) 2004 Elsevier B.V. All rights reserved.

Light charged particles in coincidence with evaporation residues and heavy fragments have been measured for the 200MeV S-32 + Mo-100 reaction leading to the Ce-132 composite. The alpha pre-scission multiplicities are remarkably larger than what found in the same system at 240 MeV. This unexpected trend can be ascribed to the opening of the fast fission channel at 240 MeV. The statistical model reproduces the light charged particles pre-scission multiplicities at 200 MeV if a delay time of tau(d) approximate to 26 x 10(-21)s is considered.

MAGIC is a new generation Cerenkov telescope which aims to detect cosmic γ-rays at energies as low as 10 – 30 GeV, closing the gap between satellites and ground-based γ-ray telescopes. In this paper we summarize the technical innovations, physics goals, and the status of the MAGIC telescope.

A 4π detection system sensitive to light charged particles is fully operational at the Laboratori Nazionali di Legnaro (LNL) since the end of 1998. The apparatus, called 8πLP, is dedicated to the study of the reaction mechanisms in heavy ion collisions at energies up to 20 AMeV. The system is a telescope array based on ΔE-E, Time of Flight and Pulse Shape Discrimination identification techniques, operating in coincidence with specialized trigger detectors for evaporation residues and fission fragments.

Pulsed emission from a few Gamma-Ray pulsars may be detectable with Ground-Based Gamma-Ray Telescopes, at energies of 10–30 GeV. A timing analysis may in part overcome the difficulty of the faint Cherenkov light yield, for a given period. The pulsar ephemerides from the archival data of HARTRAO and Princeton (1989–1998) provide an excellent opportunity to study the accuracy of extrapolations of such ephemerides to the present moment. The aim of this study is to investigate the smear in the gamma-ray pulse profile during a single night of observations, given the absence of contemporary radio pulsar observations during ON-line analyses to determine the status of a candidate. We present an analysis of the effect of pulsar timing noise on the smear in the pulse profile, by using extrapolated ephemerides from radio observations to the ‘γ-pulsar candidates online observation (de Onia-Wilhelmi et al. 2002, African Skies, 7, March 2002). The strategy is to extrapolate over a period of 103 days to give the predicted period. As a conclusion of these studies, it is clear that it is possible to extrapolatr the radio parameters of most radio pulsars over several years, given a typical integration time of 6 hours per shift. Nevertheless treating with very active pulsars (Crab, Vela . . .) requires careful consideration of timing noise. Attending to this study, for a given ephemerides, we should be able to discern if we will need comtemporary radio observation or the extrapolation is precise enough.

The HEGRA collaboration has built one of the most powerful instrument to detect VHE γ-rays from astrophysical sources, applying the stereoscopic technique to the observation of γ-ray induced air showers with Cerenkov telescopes. The HEGRA system of telescopes has been shutdown in September 2002. In what follows we shall review the most prominent results obtained by the experiment in its 5 years of operations.

L'objet de l'analyse consistait a determiner le profil des elements chimiques de l'encre gallique sur un document ecrit avant et apres un traitement aqueux et une desacidification. A cet effet une etude a ete realisee sur un manuscrit en papier chiffon datant du 17 eme siecle. La methode utilisee pour cette analyse, consistant dans l'emission de rayons X induite par des protons (Proton Induced X-ray Emission) est une methode qui ne detruit pas les elements chimiques. Les profils de concentration de 15 elements allant de Na a Pb ont ete mesures avec une precision de 0,3 mm. De cette facon il a ete possible de determiner la composition quantitative d'encre et de papier ainsi que de suivre les changements de concentration subis par les elements au cours des traitements aqueux enregistres par la methode PIXE. Il semble que cette methode meriterait d'etre developpee et qu'elle pourrait devenir un instrument de travail efficace pour les conservateurs.

The emission of two coincident energetic (E≥8 MeV) gamma rays has been observed in the 187 MeV 37Cl+ 120Sn reaction by using the cluster detectors of the EUROBALL III array. Those events are attributed to the decay of the double giant dipole resonance built on highly excited states.

Large cross-section reaction channels were measured in the systems 6Li( 7Li) + 208Pb with high statistical accuracy at 5(3) energies around the Coulomb barrier from 29 to 39 MeV. These channels were assigned (mainly) to the breakup of 6Li, very loosely bound, into α + d and to the breakup of 5Li, produced by n-transfer to the target, into α + p and to similar processes with 7Li beam. The cross-sections with 6Li, Sα = 1.475 MeV, are systematically larger than the 7Li ones. This reflects, most likely, the higher binding energy of 7Li, Sα = 2.468 MeV. Theoretical predictions for the 6Li + 208Pb system which include for 6Li breakup to continuum states within a continuum discretized coupled-channels approach (CDCC) and resonant breakup plus n-transfer with DWBA reproduce the angular distribution shapes but still underestimate the cross-sections by a factor ∼ 3.

The ridge structure with ΔEγ=±30 keV, observed in the past in coincidence with protons emitted in the reaction 187 MeV 37Cl +120Sn and attributed to an hyperdeformed nuclear shape in 152Dy, has been studied in a new experiment performed with the EUROBALL III array. The ridge is now observed in coincidence with transitions in the yrast superdeformed band of 152Dy but no discrete rotational bands have been identified.

Entrance channel effects in the fusion of heavy ions have been studied by using the 74Ge+74Ge reaction at 318 MeV. The population of the yrast superdeformed band in 144Gd shows an increase when compared with the results obtained in the more asymmetric 48Ti+100Mo reaction at 215 MeV. The relative yields of the different evaporation residues produced in the 74Ge+74Ge and in the 48Ti+100Mo reactions are very similar, with the exception of the 145,144Gd residual nuclei (3n and 4n decay channels) which are populated with a larger yield in the symmetric reaction. Statistical model calculations reproduce qualitatively such effect if a fission delay is explicitly taken into account. Effects related to fusion barrier fluctuations seem to be important in determining the spin distributions of the compound nucleus. The spectra of the high energy γ-rays emitted in the 74Ge+74Ge reaction have been measured as a function of the γ-ray multiplicity as well as in coincidence with selected evaporation residues. They are reproduced by standard statistical model calculations with GDR parameters taken from systematics, demonstrating that, in agreement with dynamical model prediction, the emission of γ-rays from the dinucleus formed in the earlier stage of the collision is unimportant.