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A. Pakou1, N. Patronis1, D. Pierroutsakou2, A.M. Sanchez-Benitez3, L. Acosta3,4, N. Alamanos5, A. Boiano2, G. Inglima6, D. Filipescu7, T. Glodariu7, A. Guglielmetti8, M. La Commara6, G. Lalazissis9, I. Martel3, C. Mazzocchi8, M. Mazzocco10, P. Molini10, C. Parascandolo2, M. Sandoli6, C. Signorini10, R. Silvestri6, F. Soramel10, M. Romoli2, E. Stiliaris11, A. Trzcinska12, K. Zerva1, E. Vardaci6, A. Vitturi10.

The knowledge of excited states in the odd-odd ${}^{150}$Pm, completely unknown until recently, is important both for understanding double $\ensuremath{\beta}$ decay of ${}^{150}$Nd and for nuclear structure studies in mass regions with a quantum phase transition. A large number of excited states have been determined for the first time in this nucleus by measuring spectra of the ${}^{152}$Sm($d$,$\ensuremath{\alpha}$) direct reaction at 25 MeV with the Munich Q3D spectrograph and by $\ensuremath{\gamma}$-ray spectroscopy with the ($p,n\ensuremath{\gamma}$) reaction at 7.1 MeV at the Bucharest tandem accelerator. Some of these levels correspond to peaks recently observed with the ${(}^{3}$He,$t$) reaction at 140 MeV/u.

The low-spin excitations of the nucleus 146Sm which is just two neutrons and two protons away from the N = 82 shell and Z = 64 subshell closures have been investigated by means of the 143Nd (α, n) and 144Nd (α, 2n) fusion-evaporation reactions. We established 47 hitherto unknown energy levels up to 4.7MeV and 75 new transitions. In addition, 7 spin assignments were possible from the γ-γ angular correlation analysis. The structure of the possible candidates for a 2+ ⊗ 3− quadrupole-octupole multiplet are first discussed in terms of the harmonic vibrational model. A comparison of these states with the corresponding ones in the neighboring N = 84 isotones is also presented. Finally, the structure of the 146Sm nucleus is interpreted in terms of the IBA-spdf model. It is shown that the model is able to reproduce the experimental relative transition strengths of the 2+ ⊗ 3− quadrupole-octupole multiplet and also a series of collective properties such as the proposed double-octupole excitations.

8th Topical Meeting on Industrial Radiation and Radioisotope Measurement Applications (IRRMA) -- JUN 24-JUL 01, 2011 -- Kansas City, MO WOS: 000306937800064 PubMed ID: 22154387 We report on a gamma-ray coincidence analysis using a mixed array of hyperpure germanium and cerium-doped lanthanum tri-bromide (LaBr3:Ce) scintillation detectors to study nuclear electromagnetic transition rates in the pico-to-nanosecond time regime in P-33,P-34 and S-33 following fusion-evaporation reactions between an O-18 beam and an isotopically enriched O-18 implanted tantalum target. Energies from decay gamma-rays associated with the reaction residues were measured in event-by-event coincidence mode, with the measured time difference information between the pairs of gamma-rays in each event also recorded using the ultra-fast coincidence timing technique. The experiment used the good full-energy peak resolution of the LaBr3:Ce detectors coupled with their excellent timing responses in order to determine the excited state lifetime associated with the lowest lying, cross-shell, I-pi = 4(-) "intruder" state previously reported in the N=19 isotone P-34. The extracted lifetime is consistent with a mainly single-particle M2 multipolarity associated with a f(7/2) -> d(5/2) single particle transition. (C) 2011 Elsevier Ltd. All rights reserved. Kansas State Univ (KSU), Coll Engn, KSU, Dept Mech & Nucl Engn, KSU, Radiat Measurement Applicat Lab, N Carolina Sate Univ, Ctr Engn Applicat Radiosotopes, Int Radiat Phys Soc (IRPS) Science and Technology Facilities Council [ST/J000051/1, ST/F006950/1, ST/G000751/1 NuSTAR, ST/G000751/1]

7Li induced-reactions have been used with a 186W target to populate nuclei around A∼180-190 at the National Institute of Physics and Nuclear Engineering in Bucharest, Romania. An array of high-purity germanium (HPGe) and cerium-doped lanthanum bromide (LaBr3:Ce) detectors have been used to measure sub-nanosecond half-lives with fast-timing techniques. The yrast 2+ state in 190Os was measured to be t1/2 = 375(20)ps, in excellent agreement with the literature value. The previously unreported half-life of the 564-keV state in 189Ir has also been measured and a value of t1/2 = 540(100)ps ps obtained.

Fast-timing measurements were performed in the region of the medium-mass $^{103,105,107}\mathrm{Cd}$ isotopes, produced in fusion evaporation reactions. Results on new and reevaluated half-lives are analyzed within a systematic study of transition rates. The $7/{2}_{1}^{+}$ states in $^{103,105,107}\mathrm{Cd}$ are interpreted as arising from a single-particle excitation. The $9/{2}^{+}$ states configuration assignment is based on the observed decay branches.

The cross sections of the {sup 115}Sn({alpha},{gamma}){sup 119}Te, {sup 115}Sn({alpha},n){sup 118}Te, and {sup 116}Sn({alpha},n){sup 119}Te reactions (both on ground and isomeric states) have been measured at effective center-of-mass energies from 9.3 to 14.8 MeV. During a first experiment, enriched self-supporting {sup 115}Sn (51.2%) + {sup 116}Sn (24.4%) foils were bombarded with an {alpha} beam delivered by the Bucharest IFIN-HH Tandem Accelerator. In a second experiment, a highly enriched {sup 116}Sn target was irradiated in order to disentangle the experimental cross section contributions due to {sup 115}Sn({alpha},{gamma}){sup 119}Te and {sup 115}Sn({alpha},n){sup 118}Te reactions obtained in the first measurement. The beam-induced activity was measured with two large volume HPGe detectors in close geometry. The experimental results were compared with theoretical predictions obtained in the framework of the statistical model.

$\ensuremath{\gamma}$ rays were measured at several angles in both singles and coincidence modes in the $^{115}\mathrm{Sn}$$(\ensuremath{\alpha},n\ensuremath{\gamma}){}^{118}$Te reaction at 15 MeV on a thick target. Multipolarities and mixing ratios were determined from the $\ensuremath{\gamma}$-ray angular distribution analysis. Lifetimes of 11 low- and medium-spin excited states in $^{118}\mathrm{Te}$ were determined from a Monte Carlo Doppler-shift attenuation method analysis of the Doppler broadened line shapes of $\ensuremath{\gamma}$ rays deexciting the levels. The results are discussed in comparison with the predictions of the interacting boson model.

Half-lives of the 19/2+ and 21/2+ states in 95Mo and of the 8+ and 10+ states in 96Mo were measured. Matrix elements for yrast transitions in 95Mo and 96Mo are discussed., Comment: Proceedings of XIX International School on Nuclear Physics, Neutron Physics and Applications, Varna, Bulgaria, 2011, 5 pages, 6 figures

Charged reaction products originated from the interaction of the loosely bound radioactive ion beam {sup 17}F (S{sub p}=600 keV) with the proton-shell closed {sup 58}Ni target were measured at two colliding energies slightly above the Coulomb barrier. The collected data were analyzed within the framework of the optical model to deduce the reaction cross section and to investigate the role played by inelastic excitations, transfer channels, and the breakup process {sup 17}F{yields}{sup 16}O+p at near-barrier energies. The reaction cross section at the lower {sup 17}F energy showed a moderate enhancement ({approx}20%) with respect to that of the system {sup 16}O+{sup 58}Ni. At this energy direct reaction channels were also found to be more relevant than those for the reaction induced from the tightly bound projectile {sup 16}O on the same target. Both features could be strongly related to the very low binding energy of the {sup 17}F valence proton.

The excitation functions for $^{7}\mathrm{Li}+^{28}\mathrm{Si}$ quasielastic scattering at ${150}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${170}^{\ifmmode^\circ\else\textdegree\fi{}}$ have been measured at sub- and near-barrier energies (0.6 to 1.3 ${\mathrm{V}}_{\mathrm{B}}$) and the corresponding barrier distributions derived. The results were analyzed within the framework of the optical model using a procedure similar to one used on previous results for $^{6}\mathrm{Li}+^{28}\mathrm{Si}$ employing double-folded potentials calculated using the BDM3Y1 effective interaction. The variation of the surface strength of the optical potential as a function of incident energy was compared for the two systems $^{6}\mathrm{Li}+^{28}\mathrm{Si}$ and $^{7}\mathrm{Li}+^{28}\mathrm{Si}$, the barrier distributions being used to help better define the potential at the lowest energies. The barrier distributions were also analyzed with continuum-discretized coupled-channel (CDCC) and coupled reaction channel (CRC) calculations as a means of investigating the influence of breakup and transfer reactions on these quantities for these light, weakly bound projectiles.

{gamma} rays were measured at several angles in both singles and coincidence mode in the {sup 119}Sn({alpha},n{gamma}){sup 122}Te reaction at 15 MeV on a thick target. Lifetimes of excited states in {sup 122}Te were determined from a Monte Carlo Doppler shift attenuation method (DSAM) analysis of the Doppler broadened lines shapes of {gamma} rays de-exciting the levels. A comparison of several deduced lifetimes with recent results obtained with the (n,n{sup '}) reaction allowed us to validate the choice of a parameter used to calculate the contribution of the side feeding times. The ingredients of the DSAM line-shape analysis (stopping power, description of instrumental line shapes, and side feeding evaluation) are presented in some detail. It is concluded that with proper treatment of side feeding, a DSAM line-shape analysis of peaks in singles or coincidence spectra obtained following the ({alpha},n{gamma}) reaction is able to provide rather accurate values for the lifetimes of levels with low and medium spins.

A fast-timing method to determine lifetimes of nuclear states in the sub-nanosecond domain is presented. It is based on in-beam measurements of triple-gamma coincidences in heavy-ion fusion-evaporation reactions, performed with an array of HPGe and LaBr(3):Ce detectors. The high-energy resolution HPGe detectors are used to define de-exciting cascades, while the fast LaBr(3):Ce detectors are used to determine the decay time spectra of selected levels fed by these cascades. A special method to treat the time information of an array of fast detectors is employed in order to fully use the efficiency of the array. Two measurements are presented to illustrate the method: a re-determination of the known half-life T(1/2) = 0.7 ns of 7/2(+) level in (107)Cd (test experiment), and the determination of a half-life T(1/2) = 0.7 ns of the E(x) = 205 keV, J(pi) = 7/2(+) level in (107)Cd (test experiment), and the determination of a half-life T(1/2) = 47 ps for the E(x) = 367 keV, J(pi) = 3/2(+) state of (199)Tl..

Elastic backscattering measurements were performed for the weakly bound nucleus $^{6}\mathrm{Li}$ on a $^{28}\mathrm{Si}$ target at sub- and near-barrier energies (0.6 to 1.3 V${}_{C.B.}$). Excitation functions of elastic scattering cross sections were measured at ${150}^{\ifmmode^\circ\else\textdegree\fi{}}$ and ${170}^{\ifmmode^\circ\else\textdegree\fi{}}$ and the corresponding ratios to Rutherford scattering and relevant barrier distributions were formed. The results are discussed in terms of the potential threshold anomaly and the reaction mechanisms involved.

We investigated the dynamical dipole mode, related with entrance channel charge asymmetry effects, in the 40Ar+92Zr and 36Ar+96Zr fusion reactions at Elab = 15.1 A and 16 A MeV, respectively. These reactions populate, through entrance channels having different charge asymmetries, a compound nucleus in the A = 126 mass energy region, identical spin distribution at an average excitation energy of about 280 MeV. The compound nucleus average excitation energy and average mass were deduced by the analysis of the light charged particle energy spectra. By studying the γ‐ray energy spectra and the γ‐ray angular distributions of the considered reactions, the dynamical nature of the prompt radiation related to the dynamical dipole mode was evidenced. The data are compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics.

The cross sections of the $^{117}\mathrm{Sn}$($\ensuremath{\alpha},\ensuremath{\gamma}$) $^{121}\mathrm{Te}$ and $^{117}\mathrm{Sn}$($\ensuremath{\alpha},p$) $^{120}\mathrm{Sb}$ reactions have been measured in the effective center of mass energy from 11.5 to 14.6 MeV. Highly enriched self-supporting $^{117}\mathrm{Sn}$ (90%) foils were bombarded with an $\ensuremath{\alpha}$ beam delivered by the Bucharest IFIN-HH tandem accelerator. The induced activity of $^{121}\mathrm{Te}$ and $^{120}\mathrm{Sb}$ was measured with two large-volume high-purity Ge detectors in close geometry to maximize the detector efficiency. The experimental cross section and astrophysical $S$ factor are compared with statistical model predictions for different global $\ensuremath{\alpha}$-nucleus optical potentials.

The prompt γ-ray emission is investigated in the 16 A MeV energy region by means of the 36,40Ar + 96,92Zr fusion reactions leading to a compound nucleus in the vicinity of 132Ce. The dynamical nature of this radiation is confirmed. We show that the prompt γ radiation has an angular distribution pattern consistent with a dipole oscillation along the symmetry axis of the dinuclear system. The data are compared with calculations based on a collective bremsstrahlung analysis of the reaction dynamics.

Within the frame of the commissioning of a new experimental apparatus EXPADES we undertook the measurement of the elastic scattering angular distribution for the system 17 O+ 208 Pb at energy around the Coulomb barrier. The reaction dynamics induced by loosely bound Radioactive Ion Beams is currently being extensively studied [4]. In particular the study of the elastic scattering process allows to obtain direct information on the total reaction cross section of the exotic nuclei. In order to understand the effect of the low binding energy on the reaction mechanism it is important to compare radioactive weakly bound nuclei with stable strongly-bound nuclei. In this framework the study of the 17 O+ 208 Pb elastic scattering can be considered to be complementary to a previous measurement of the total reaction cross section for the system 17 F+ 208 Pb at energies of 86, 90.4 MeV [5, 6]. The data will be compared with those obtained for the neighboring systems 16,18 O+ 208 Pb and others available in literature.

We investigated the reaction induced by the Radioactive Ion Beam 7Be on the closed proton shell nucleus 58Ni at 22.0 MeV bombarding energy. The 7Be beam was produced by means of the in-flight technique with the facility EXOTIC at INFN-LNL (Italy). Charged reaction products were mass and charge identified in a rather wide angular range and their energy distributions were analyzed to infer some information on the production mechanism. The relevance of direct processes, especially 3He- and 4He-stripping, as well as compound nucleus reactions is critically reviewed.

The study of reactions induced by exotic weakly bound nuclei at energies around the Coulomb barrier had attracted a large interest in the last decade, since the features of these nuclei can deeply affect the reaction dynamics. The discrimination between different reaction mechanisms is, in general, a rather difficult task. It can be achieved by using detector arrays covering high solid angle and with high granularity that allow to measure the reaction products and, possibly, coincidences between them, as, for example, recently done for stable weakly bound nuclei [1, 2]. We investigated the collision of the weakly bound nucleus 7Be on a 58Ni target at the beam energy of 1.1 times the Coulomb barrier, measuring the elastic scattering angular distribution and the energy and angular distributions of 3He and 4He. The 7Be radioactive ion beam was produced by the facility EXOTIC at INFN-LNL with an energy of 22 MeV and an intensity of ~3×105 pps. Results showed that the 4He yeld is about 4 times larger than 3He yield, suggesting that reaction mechanisms other than the break-up mostly produce the He isotopes. Theoretical calculations for transfer channels and compound nucleus reactions suggest that complete fusion accounts for (41±5%) of the total reaction cross section extracted from optical model analysis of the elastic scattering data, and that 3He and 4He stripping are the most populated reaction channels among direct processes. Eventually estimation of incomplete fusion contributions to the 3,4He production cross sections was performed through semi-classical calculations with the code PLATYPUS [3].

We investigated the prompt dipole γ‐ray emission, related with entrance channel charge asymmetry effects, in the 40Ar + 92Zr and 36Ar + 96Zr fusion reactions at Elab= 15 and 16 MeV/nucleon, respectively, with the aim to probe its evolution with incident energy. These reactions populate, through entrance channels having different charge asymmetries, the 132Ce compound nucleus at an average excitation energy of 304 MeV with identical spin distribution. Fusionlike events were selected by detecting high‐energy γ‐rays in coincidence with evaporation residues. By studying the differential γ‐ray multiplicity spectra of the considered reactions, it was shown that the dipole γ‐ray intensity increases by ∼14% for the more charge asymmetric system. This result, associated with those reported for the 32,36S + 100,96Mo reaction pair at lower beam energies, implies a “rise and fall” trend of the prompt dipole γ‐ray emission in the studied beam energy range with a maximum value at 9 MeV/nucleon.

A large number of new measurements with the activation technique were performed for $(n,2n)$ and neutron-induced $\ensuremath{\Delta}Z=1,2$ reaction cross sections on the stable molybdenum isotopes in the energy range from 13.5 to 21 MeV. First results were obtained for the $^{92}\mathrm{Mo}(n,2n){^{91}\mathrm{Mo}}^{m},^{92}\mathrm{Mo}(n,\ensuremath{\alpha}){^{89}\mathrm{Zr}}^{m},^{94}\mathrm{Mo}$$(n,2n){^{93}\mathrm{Mo}}^{m},^{95}\mathrm{Mo}(n,p){^{95}\mathrm{Nb}}^{m},^{96}\mathrm{Mo}(n,p)^{96}\mathrm{Nb},^{96}\mathrm{Mo}(n,x)$${^{95}\mathrm{Nb}}^{m}$, $^{97}\mathrm{Mo}$$(n,p)$$^{97}\mathrm{Nb}$, $^{97}\mathrm{Mo}$$(n,p)$${^{97}\mathrm{Nb}}^{m}$, $^{97}\mathrm{Mo}$$(n,x)$$^{96}\mathrm{Nb}$, $^{98}\mathrm{Mo}$$(n,p)$${^{98}\mathrm{Nb}}^{m}$, $^{98}\mathrm{Mo}$$(n,x)$$^{97}\mathrm{Nb}$, $^{98}\mathrm{Mo}$$(n,x)$${^{97}\mathrm{Nb}}^{m}$, and $^{100}\mathrm{Mo}$$(n,\ensuremath{\alpha})$$^{97}\mathrm{Zr}$ reactions, above 16 MeV. A significant number of high-accuracy 14 MeV measurements were performed which are in good agreement with the measurements above 16 MeV for reactions studied in both energy ranges. The rather complete database for the molybdenum isotopes was analyzed with two different sets of consistent model calculations: a local and a global approach. The global approach (a blind calculation with the TALYS code) provides a good overall description of the dominant reaction channels, although the $(n,\ensuremath{\alpha})$ reactions for the heavy isotopes are overpredicted. The local approach (an adjusted calculation with the STAPRE-H code) describes the shapes and magnitudes of the excitation functions well from the reaction thresholds up to 21 MeV using a consistent parameter set, which was optimized based on all experimental information for the nuclei at hand and their immediate neighbors. The agreement between experimental and calculated data is, in general, good both at the maxima and at the tails of the excitation functions, and both for total activation cross sections of a particular channel and for cross sections leading to isomers, showing the viability of the level densities, the optical models, and the \ensuremath{\gamma} widths. Comparison of the two model calculations with the data indicates the relevance of an appropriate treatment for preequilibrium (PE) \ensuremath{\alpha}-particle emission for the description of the data above 14 MeV. Comparison between the model calculations shows largely different PE deuteron emission contributions to the total $(\ensuremath{\Delta}Z=1,\ensuremath{\Delta}A=1)$ cross sections with an additional marked difference in energy dependence. This suggests that emission spectra around 20 MeV are required to establish the magnitude of the PE deuteron emission contribution to this process. New \ensuremath{\gamma}-ray strength functions were established by verification against average $(n,\ensuremath{\gamma})$ data and were demonstrated to give good agreement with the measured isomer production cross sections.

A new pixel-structure detector array with a large solid angle coverage has been used for the first time to study the elastic scattering of exotic $^{17}\mathrm{F}$ nuclei from a $^{208}\mathrm{Pb}$ target at $90.4\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$. The experimental data have been analyzed in the framework of the optical model potential and the real and imaginary strong absorption radii have been evaluated. These quantities have been compared with those obtained for the system $^{19}\mathrm{F}+^{208}\mathrm{Pb}$ at the same energy in the center of mass frame. The $^{17}\mathrm{F}+^{208}\mathrm{Pb}$ reaction cross section is more similar to those of the systems $^{16,17}\mathrm{O}+^{208}\mathrm{Pb}$ rather than to the one of the system $^{19}\mathrm{F}+^{208}\mathrm{Pb}$ at similar energies: this indicates that in the energy range around the Coulomb barrier the breakup channel is still weak. The exclusive breakup cross section $^{17}\mathrm{F}\ensuremath{\rightarrow}^{16}\mathrm{O}+p$ has been measured for the first time at energy below the Coulomb barrier.

The γ-strength functions and level densities of 73,74Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ∼1-13 MeV for 74Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ∼3 MeV towards lower γ energies. The obtained data show that both 73,74Ge display an increase in strength at low γ energies., SCOPUS: cp.p, info:eu-repo/semantics/published

The Extreme Light Infrastructure - Nuclear Physics, one of the three pillars of the Extreme Light Infrastructure Pan-European initiative, is a new large scale facility dedicated to nuclear physics with extreme electromagnetic fields. ELI-NP will host two 10 PW lasers and a very brilliant Gamma beam system with unprecedented intensity and energy resolution parameters. We propose to perform photon induced nuclear reactions using the very brilliant γ -ray beams provided by the Gamma beam system to examine in detail the photon absorption process and its decay modes. Here the experimental program related to nuclear research on reactions above the neutron separation threshold, which is under preparation at ELI-NP, is presented.

We measured for the first time 7 Be elastically scattered nuclei as well as 3,4 He reaction products from a 58 Ni target at 22.3 MeV beam energy. The data were analyzed within the optical model formalism to extract the total reaction cross section. Extensive kinematical, Distorted Wave Born Approximation (DWBA) and Continuum Discretized Coupled Channel (CDCC) calculations were performed to investigate the 3,4 He originating mechanisms and the interplay between different reaction channels.

The parity doublet of 1+/1− states of Ne-20 at 11.26 MeV excitation energy is one of the best known test cases to study the weak part of the nuclear Hamiltonian. The feasibility of parity violation experiments depend on the effective nuclear enhancement factor (RN/|E(1+) − E(l−)|) which amplifies the impact of the matrix element of the weak interaction on observables indicating parity mixing. An extreme large value of Rn/|E(1+) − E(l−)| = (670 ± 7000) MeV−1 was reported for the doublet in 20Ne. The large uncertainty depends amongst others on the large uncertainty of |E(1+) − E(l−)| = 7.7±5.5 keV of the parity doublet. Nuclear resonance fluorescence (NRF) experiments with linearly and circularly polarized photon beams were performed at the High Intensity Gamma-Ray Source at Duke University, Durham, NC, USA, to determine the energy difference of the parity doublet with higher precision. The different angular distributions for 0+ → 1− → 0+ and 0+ → 1+ → 0+ NRF cascades in polarized γ-ray beams were used to determine the energy difference of the parity doublet to 2.9(13) keV.

A new experimental apparatus for charged particle detection, named EXODET (EXOtic DETector) has been designed to be used in nuclear physics experiments involving radioactive ion beams (RIBs). A typical feature of RIBs presently available at the first-generation production facilities is the low beam intensity (10/sup 5/--10/sup 6/ pps); therefore, a large solid angle coverage and a high granularity are required to allow the reconstruction of the complete event kinematics. In this paper, we present the main features of the EXODET apparatus, fulfilling the previous requirements, and the first experimental results.

In the present contribution, we will briefly present an overview of the last experimental results obtained by the Italian EXOTIC collaboration on the study of the reaction mechanisms around the Coulomb barrier with light weakly bound Radioactive Ion Beams. Several experiments have been performed by our group in different laboratories: at ANL (USA) and, more recently, at LNL (Italy) to study the system 17F+208Pb and at RIKEN (Japan) for the system 11Be+209Bi. A comparative discussion with the results obtained for other reactions induced by light weakly‐ and tightly‐bound projectiles will be finally given.

The study of the resonant structures in neutron-nucleus cross-sections, and therefore of the compoundnucleus reaction mechanism, requires spectroscopic measurements to determine with high accuracy the energy of the neutron interacting with the material under study. To this purpose, the neutron time-of-flight facility n_TOF has been operating since 2001 at CERN. Its characteristics, such as the high intensity instantaneous neutron flux, the wide energy range from thermal to few GeV, and the very good energy resolution, are perfectly suited to perform highquality measurements of neutron-induced reaction cross sections. The precise and accurate knowledge of these cross sections plays a fundamental role in nuclear technologies, nuclear astrophysics and nuclear physics. Two different measuring stations are available at the n_TOF facility, called EAR1 and EAR2, with different characteristics of intensity of the neutron flux and energy resolution. These experimental areas, combined with advanced detection systems lead to a great flexibility in performing challenging measurement of high precision and accuracy, and allow the investigation isotopes with very low cross sections, or available only in small quantities, or with very high specific activity. The characteristics and performances of the two experimental areas of the n_TOF facility will be presented, together with the most important measurements performed to date and their physics case. In addition, the significant upcoming measurements will be introduced.

The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,γ) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.

At the neutron time-of-flight facility n_TOF at CERN a new vertical beam line was constructed in 2014, in order to extend the experimental possibilities at this facility to an even wider range of challenging cross-section measurements of interest in astrophysics, nuclear technology and medical physics. The design of the beam line and the experimental hall was based on FLUKA Monte Carlo simulations, aiming at maximizing the neutron flux, reducing the beam halo and minimizing the background from neutrons interacting with the collimator or back-scattered in the beam dump. The present paper gives an overview on the design of the beam line and the relevant elements and provides an outlook on the expected performance regarding the neutron beam intensity, shape and energy resolution, as well as the neutron and photon backgrounds., Engineering & Physical Sciences Research Council (EPSRC) EP/I003258/1, Science & Technology Facilities Council (STFC) ST/L005794/1 ST/J000159/1

International audience; The neutron time of flight (n_TOF) facility at CERN is a spallation source characterized by a white neutron spectrum. The innovative features of the facility, in the two experimental areas, (20 m and 185 m), allow for an accurate determination of the neutron cross section for radioactive samples or for isotopes with small neutron capture cross section, of interest for Nuclear Astrophysics. The recent results obtained at n_TOF facility are presented.

Proton elastic scattering angular distributions for the reaction F-17 + p, were measured in inverse kinematics over a wide angular range (theta(c.m). = 50 degrees-160 degrees) at two near-barrier energies of 3.5 and 4.3 MeV/u. The optical potential was probed in a phenomenological and microscopic approach. Moreover, total reaction cross-sections were also determined via optical potential analysis and were used as a signature for probing a possible halo structure of this proton-rich nucleus. Physical Review C

The reaction dynamics induced by the 17F Radioactive Ion Beam on the proton-shell closed 58Ni target was studied at two colliding energies slightly above the Coulomb barrier. Charged reaction products were detected at forward angles and the quasi-elastic differential cross section was analyzed within the framework of the optical model in order to extract the reaction cross section and to investigate the relevance of direct reaction channels (inelastic scattering, breakup and transfer) at near-barrier energies. The comparison with the reaction induced by double-magic tightly-bound 16O projectiles on the same target showed that the 17F reaction cross section is moderately enhanced at the lower secondary beam energy. Direct reaction channels were also found to be more relevant than for the corresponding 16O-induced reaction.

The scattering processes of two mirror projectiles, the well bound 17 O (Sn = 4.143 MeV) and the loosely bound radioactive 17 F (Sp = 0.600 MeV), on the proton closed shell target 58 Ni were measured at several energies around the Coulomb barrier. The experimental data were analyzed within the framework of the optical model to extract the reaction cross section and to investigate the role played by direct reaction channels at near-barrier energies. The comparison shows a similar behaviour for the two A = 17 projectiles despite their very different binding energies and suggests a rather small effect of the 17 F breakup channel on the reaction dynamics.

Charged reaction products originated from the interaction of the loosely bound radioactive ion beam (17)F (S(p) = 600 keV) with the proton-shell closed (58)Ni target were measured at two colliding energies slightly above the Coulomb barrier. The collected data were analyzed within the framework of the optical model to deduce the reaction cross section and to investigate the role played by inelastic excitations, transfer channels, and the breakup process (17)F --> (16)O + p at near-barrier energies. The reaction cross section at the lower (17)F energy showed a moderate enhancement (similar to 20%) with respect to that of the system (16)O + (58)Ni. At this energy direct reaction channels were also found to be more relevant than those for the reaction induced from the tightly bound projectile (16)O on the same target. Both features could be strongly related to the very low binding energy of the (17)F valence proton. Physical Review C

The excitation functions for (7)Li + (28)Si quasielastic scattering at 150 degrees and 170 degrees have been measured at sub- and near-barrier energies (0.6 to 1.3 VB) and the corresponding barrier distributions derived. The results were analyzed within the framework of the optical model using a procedure similar to one used on previous results for (6)Li + (28)Si employing double-folded potentials calculated using the BDM3Y1 effective interaction. The variation of the surface strength of the optical potential as a function of incident energy was compared for the two systems (6)Li + (28)Si and (7)Li + (28)Si, the barrier distributions being used to help better define the potential at the lowest energies. The barrier distributions were also analyzed with continuum-discretized coupled-channel (CDCC) and coupled reaction channel (CRC) calculations as a means of investigating the influence of breakup and transfer reactions on these quantities for these light, weakly bound projectiles. Physical Review C

We have studied the elastic scattering of the exotic F-17 nuclei from Pb-208 at Coulomb barrier energies. For the measurement we used a new detector array with pixel structure and a large solid angle. Optical potential analysis shows that F-17 has an imaginary potential much less deep than F-19. Information on the exclusive F-17 breakup cross section has been deduced too.