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Relatively high counting rates were registered in a proton inelastic scattering experiment on 16 O and 28 Si using HPGe detectors which was performed at the Tandem facility of IFIN-HH, Bucharest. In consequence, dead time corrections were needed in order to determine the absolute γ -production cross sections. Considering that the real counting rate follows a Poisson distribution, the dead time correction procedure is reformulated in statistical terms. The arriving time interval between the incoming events ( Δ t ) obeys an exponential distribution with a single parameter - the average of the associated Poisson distribution. We use this mathematical connection to calculate and implement the dead time corrections for the counting rates of the mentioned experiment. Also, exploiting an idea introduced by Pommé et al. , we describe a consistent method for calculating the dead time correction which completely eludes the complicated problem of measuring the dead time of a given detection system. Several comparisons are made between the corrections implemented through this method and by using standard (phenomenological) dead time models and we show how these results were used for correcting our experimental cross sections. [ABSTRACT FROM AUTHOR]

The γ production cross sections from neutron inelastic scattering on 24Mg were measured for neutron energies up to 18 MeV at GELINA (the Geel Linear Accelerator), the neutron source operated by EC-JRC-IRMM, Belgium. The level cross section and the total inelastic cross section were determined. We used the GAINS (Gamma Array for Inelastic Neutron Scattering) spectrometer with seven large-volume high-purity germanium (HPGe) detectors placed at 110° and 150° with respect to the beam direction. The neutron flux was determined with a 235U fission chamber. The results are compared with calculations performed with the talys 1.6 code using the default settings. [ABSTRACT FROM AUTHOR]

A measurement was performed at the white neutron source Geel Linear Accelerator (GELINA) of the Institute for Reference Materials and Measurements to determine the cross sections for the (n, n'γ) and (n, 2n'γ) reactions on 56Fe. The Gamma Array for Inelastic Neutron Scattering (GAINS) was used. The results are scaled to the neutron-induced fission cross section of 235U. The paper emphasizes the multiple checks performed to assure the consistency of the results. γ production cross sections, total inelastic cross sections, and level production cross sections were determined. A good agreement exists with previous measurements. Theoretical calculations were performed with the talys 1.6 reaction code using default parameters, but also using a microscopic approach. These calculations are discussed in comparison t [ABSTRACT FROM AUTHOR]

The inelastic scattering of neutrons on 28Si was investigated using the (n,n'ɣ) technique. The ɣ production cross sections were measured and the level and total inelastic cross sections were determined with high accuracy. 28Si was also excited through the 25Mg(ɑ,nɣ)28Si reaction and a comparison of the ɣ production cross sections determined for various incident energies was performed. [ABSTRACT FROM AUTHOR]

The inelastic scattering of neutrons on structural materials constitutes a major concern for the design of neutrinoless double β decay experiments. We explore our neutron inelastic scattering data on 206Pb, 56Fe, 28Si, 24Mg, and 12C, searching for possible contributors to the background in the energy region where neutrinoless double β decay signals would be produced. [ABSTRACT FROM AUTHOR]

Abstract: The GAINS (Germanium Array for Inelastic Neutron Scattering) setup was recently installed at the GELINA (Geel Linear Accelerator) neutron source of EC-JRC-IRMM. In order to produce reliable neutron inelastic cross-section data the setup requires a precise efficiency calibration for each sample under investigation. These samples represent extended sources in non-standard orientations and with significant self-attenuation of gamma rays. We present in detail the efficiency calibration procedure performed with two Monte Carlo simulations using MCNP and GEANT4. A good agreement is found between the two independent approaches. The general features of the simulations are discussed together with an in-depth description of the various factors influencing the efficiency. [Copyright &y& Elsevier]

Abstract: A comprehensive set of Monte Carlo simulations was performed with the MCNP5 code to provide a generic characterisation of the neutron and photon fluxes for time-of-flight measurements at all flight paths of the GELINA facility. Simulations were performed for the direct flux configuration (DFC, 10keV–20MeV) and the moderated flux configuration (MFC, 10meV–1MeV). Fluxes and flux energy spectra were obtained for both neutrons and photons. For neutrons, additionally, detailed resolution functions and figures of merit were obtained. The validity of the approach for the photon spectra is shown by comparison with a dedicated measurement. Also, a verification is presented of the validity of the neutron resolution function by comparison with measured capture and transmission data for 103Rh and 56Fe in the incident neutron energy range from 70eV to 50keV. This comprehensive overview will facilitate the planning and analysis of measurements at the GELINA facility with an improved knowledge of its physical characteristics. [Copyright &y& Elsevier]

Abstract: Gamma production cross sections for neutron inelastic scattering, and reactions on 208Pb were measured at the Geel Electron Linear Accelerator (GELINA) from the respective thresholds up to at most 20 MeV. An unprecedented neutron energy resolution of 1.1 keV at 1 MeV (35 keV at 10 MeV) and a total uncertainty of about 5% was achieved for the integral gamma production cross section of the most intense transition in 208Pb. The gamma production cross section was measured for 29 transitions of the inelastic channel, 5 transitions of the channel and one transition of the channel. Based on the evaluated level scheme of 208Pb, the total neutron inelastic scattering cross section and the level cross sections were deduced. Four large volume HPGe (high purity germanium) detectors were used for the detection of the γ-rays. The 88.11% enriched 208Pb sample was placed at a flight path length of 198.551 m. The cross sections were measured relative to the standard cross section by continuously monitoring the neutron flux with a fission chamber containing 235U. The results are compared with the existing experimental data from the literature and with model estimates obtained with the recent TALYS 1.00 code. A good agreement of the present data is found with both the existing experimental data and with the calculations. The present work greatly expands the number of measured gamma production cross sections and the level cross sections derived for this nucleus. [Copyright &y& Elsevier]

Abstract: Gamma production cross-sections were measured for the neutron inelastic scattering and () reactions on 209Bi using the white neutron spectrum of GELINA with the time-of-flight technique at the 200 m flight-path station. The full energy range, from the inelastic threshold up to 20 MeV was covered in one experiment with an unprecedented energy resolution of 1.1 keV at 1 MeV and 35 keV at 10 MeV. The gamma-rays were detected with large volume HPGe detectors. The flux was determined with a 235U fission chamber based on the 235U() standard cross-section. A metallic Bi sample was used. Inelastic gamma production cross-sections were measured for 39 transitions up to an excitation energy of 3.8 MeV. Based on the adopted level scheme of 209Bi, the total inelastic and the level cross-sections were constructed. A total uncertainty smaller than 5% was obtained for the total inelastic cross-section up to 10 MeV. The gamma production cross-section was measured for the 8 transitions from 208Bi nucleus up to 1.09 MeV excitation energy. The results are compared with earlier experimental works and with model calculations performed with the TALYS code, version 0.72. Calculations with the TALYS model code show good agreement with the deduced total inelastic cross-section in the entire incident energy range and for deduced level cross-sections below 3 MeV. Discrepancies between calculation and experiment that occur for gamma production cross-sections above 3 MeV are discussed. [Copyright &y& Elsevier]

Abstract: A 12-bits and 420MSample/s waveform digitizer was used with large volume High Purity Germanium (HPGe) detectors for measurements of gamma-ray production cross-section from inelastic neutron scattering. For these time-of-flight measurements at the GELINA white neutron source, the use of a fast digitizer significantly increases the efficiency compared with a conventional data acquisition system. First, the pulse processing time required to obtain the amplitude with high resolution is significantly reduced so that pulse pile-up with the prompt gamma-burst is eliminated for neutron-induced events. Second, an improved time response is obtained for which the amplitude and rise time dependence is strongly reduced compared to that of a conventional constant fraction discriminator. Excellent energy and time resolution is obtained with algorithms suitable for on-line signal processing, so that data storage is under control. Bench tests are presented that compare methods of signal processing. For the best method, the data acquisition system based on the fast digitizer was tested during measurements of gamma production cross-sections for and . A direct comparison was made with results obtained with conventional electronics operated in parallel. [Copyright &y& Elsevier]

Abstract: Cross-sections were measured for gammas produced by neutron inelastic scattering and () reactions on 52Cr using the white neutron spectrum of GELINA with the time-of-flight technique at the 200 m flight-path station. The full energy range, from the inelastic threshold up to 18 MeV was covered in one experiment with an unprecedented neutron energy resolution of 1.1 keV at 1 MeV and 35 keV at 10 MeV. The gamma rays were detected with large volume HPGe detectors. The flux was determined with a 235U fission chamber based on the 235U() standard cross-section. A Cr2O3 sample was used with a 52Cr/Cr concentration of 99.85% wt. Inelastic gamma production cross-sections were measured for 12 transitions, at least one transition from each level up to an excitation energy of 3.77 MeV. Based on the adopted level scheme of 52Cr, the total inelastic and the level cross-sections were constructed. A total uncertainty smaller than 5% was obtained for the total inelastic cross-section up to 10 MeV. The () gamma production cross-section was measured for the 749.06 keV and 1164.4 keV transitions from 51Cr. Results are compared with earlier experimental works and model calculations performed with the TALYS code. Calculations with the default parameters of TALYS show in general rather good agreement with the present data. [Copyright &y& Elsevier]

Proton-rich isotopes of zinc and germanium, 57Zn and 61Ge, have been produced by fragmentation of a 70Ge beam at the LISE3 facility of GANIL. Their main decay characteristics have been studied after implantation in a double-sided silicon strip detector. In addition, the production cross-sections of proton-rich isotopes in the copper-to-germanium region have been determined. These cross-sections are much lower than predicted by the EPAX formula. These findings question to some extent the production rates expected for present and future fragmentation facilities. [ABSTRACT FROM AUTHOR]

The new neutron time-of-flight facility (n_TOF) has been built at CERN and is now operational. The facility is intended for the measurement of neutron induced cross-sections of relevance to Accelerator Driven Systems (ADS) and to fundamental physics. Neutrons are produced by spallation of the 20 GeV/c proton beam, delivered by the Proton Synchrotron (PS), on a massive target of pure lead. A measuring station is placed at ≈185 m from the neutron producing target, allowing high-resolution measurements. The facility was successfully commissioned with two campaigns of measurements, in November 2000 and April 2001. The main interest was concentrated in the physical parameters of the installation (neutron fluence and resolution function), along with the target behavior and various safety-related aspects. These measurements confirmed the expectations from Monte Carlo simulations of the facility, thus allowing to initiate the foreseen physics program. [Copyright &y& Elsevier]

The n_TOF facility at CERN is a source of neutrons produced by spallation of 20 GeV/c protons onto a lead target. The outstanding characteristics of this source (very high intensity, 200 m flight path, wide spectral function) make it an extremely useful tool for studying neutron induced reactions. The neutrons in the energy region from 1 to 10 MeV are particularly interesting for producing nuclei with large neutron excess by fission. The onset of an asymmetric fission mode at these energies seems to considerably enhance the yield of neutron rich species. Therefore, a method could emerge for producing neutron rich rare earth nuclei in a region up to now inaccessible. [Copyright &y& Elsevier]

A neutron inelastic scattering experiment was performed at the Geel Electron Linear Accelerator neutron source using an enriched 54Fe sample. The γ rays produced in the reaction were detected using the Gamma Array for Inelastic Neutron Scattering spectrometer. For each observed transition we determined the γ-production cross section for incident energies ranging from the inelastic threshold (≈1.434 MeV) up to 18 MeV. Using these primary data we also calculated the cross section of the first excited level and the total inelastic cross section. Our experimental results are compared with previous reported values, evaluated nuclear data libraries and theoretical calculations performed with the TALYS 1.9 code. A careful tuning of the optical model parameters allowed significant improvements in the description of the experimental results leading to interesting conclusions regarding the interaction of the 54Fe nucleus with neutrons. [ABSTRACT FROM AUTHOR]

A new high-flux spallation neutron source, the neutron time-of-flight facility (nTOF), recently became operational at CERN. The neutron energy ranges from the thermal to the GeV range. Performance results from the commissioning are reported. [ABSTRACT FROM AUTHOR]

Excitation functions for γ production associated with the neutron inelastic scattering and the (n, 2n) reactions on 206Pb were measured from threshold up to 18 MeV for about 40 transitions. Two independent measurements were performed using different samples and acquisition systems to check consistency of the results. The neutron flux was determined with a 235U fission chamber and a procedure that were validated against a fluence standard. For incident energy higher than the threshold for the first excited level and up to 3.5 MeV, estimates are provided for the total inelastic and level cross sections by combining the present γ production cross sections with the level and decay data of 206Pb reported in the literature. The uncertainty common to all incident energies is 3.0% allowing overall uncertainties from 3.3% to 30% depending on transition and neutron energy. The present data agree well with earlier work, but significantly expand the experimental database while comparisons with model calculations using the talys reaction code show good agreement over the full energy range. [ABSTRACT FROM AUTHOR]

We have refurbished and tested a neutron array composed of 81 BC400 plastic scintillator detectors dedicated for neutron measurements in future fusion–fission experiments The Neutron Array (NA) detectors, installed at the 9 MV Tandem accelerator facility of the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), have been refurbished and the data acquisition system has been updated. We present the characteristics and performances of the NA and of the associated electronics. [ABSTRACT FROM AUTHOR]

Abstract: The neutron inelastic scattering cross-section of 23Na has been measured in response to the relevant request of the OECD–NEA High Priority Request List, which requires a target uncertainty of 4% in the energy range up to 1.35MeV for the development of sodium-cooled fast reactors. The measurement was performed at the GELINA facility with the Gamma Array for Inelastic Neutron Scattering (GAINS), featuring eight high purity germanium detectors. The setup is installed at a 200m flight path from the neutron source and provides high resolution measurements using the (n,n′γ)-technique. The sample was an 80mm diameter metallic sodium disk prepared at IRMM. Transitions up to the seventh excited state were observed and the differential gamma cross-sections at 110° and 150° were measured, showing mostly isotropic gamma emission. From these the gamma production, level and inelastic cross-sections were determined for neutron energies up to 3838.9keV. The results agree well with the existing data and the evaluated nuclear data libraries in the low energies, and provide new experimental points in the little studied region above 2MeV. Following a detailed review of the methodology used for the gamma efficiency calibrations and flux normalization of GAINS data, an estimated total uncertainty of 2.2% was achieved for the inelastic cross-section integrals over the energy ranges 0.498–1.35MeV and 1.35–2.23MeV, meeting the required targets. [Copyright &y& Elsevier]

A new setup was developed at the Geel Electron LINear Accelerator (Gelina) pulsed white neutron source for the measurement of continuous energy excitation functions of gamma-ray production cross-sections in neutron-induced inelastic scattering. Characteristic gamma-rays are identified, background-free, using the good pulse height resolution of two large volume High-Purity Germanium (HPGe) detectors. High incident-energy resolution is achieved by the time-of-flight method with a flight-path length of 200 m and a time resolution of 8 ns full-width at half-maximum. A neutron energy resolution of 1.1 keV fwhm is obtained at 1 MeV (36 keV at 10 MeV). Absolute cross-sections are obtained by measuring the neutron flux with a 235U fission chamber. The setup was successfully applied to the determination of excitation curves of gamma-ray production cross-sections, level inelastic cross-sections and total inelastic cross-sections for 52Cr and 58Ni. [Copyright &y& Elsevier]

The features of fission fragments formed in the near barrier reaction 32 S + 197 Au ( E beam lab = 166 MeV ) are investigated. The measurement was performed at the ALTO facility of IPN Orsay, France, with the aim of clarifying the quantitative contribution of the quasi-fission process to the total fission events. The mass and total kinetic energy of the fission fragments were compared to the expectations of the liquid drop model, revealing an asymmetric fission component which may be traced back to a quasi-fission process mixed with the fusion–fission events. The γ -rays and neutrons measured in coincidence with the fission fragments were used to yield additional information for the discrimination of the two aforementioned mechanisms. All observed trends are consistent and fairly well reproduced by the statistical model. [ABSTRACT FROM AUTHOR]

The ACtive TARget and Time Projection Chamber (ACTAR TPC) is a novel gas-filled detector that has recently been constructed at GANIL. This versatile detector is a gaseous thick target that allows the tracking of charged particles in three dimensions and provides a precise reaction energy reconstruction from the vertex position. A commissioning experiment using resonant scattering of a 3.2 MeV/nucleon 18O beam on an isobutane gas (proton) target was performed. The beam and the heavy scattered ions were stopped in the gas volume, while the light recoil left the active volume and were stopped in auxiliary silicon detectors. A dedicated tracking algorithm was applied to determine the angle of emission and the length of the trajectory of the ions, to reconstruct the reaction kinematics used to built the excitation functions of the 1 H(18O, 18O) 1 H and 1 H(18O, 15N) 4 He reactions. In this article, we describe the design of the detector and the data analysis, that resulted in center of mass reaction energy resolutions of 38(4) keV FWHM and 54(9) keV FWHM for the proton and alpha channels, respectively. [ABSTRACT FROM AUTHOR]

A neutron inelastic scattering experiment was performed on an enriched 57Fe sample at the Geel Electron Linear Accelerator neutron source using the Gamma Array for Neutron Inelastic Scattering spectrometer. Several γ-production cross sections were determined, but the first transition (14.4 keV) could not be detected owing to the steadily increased γ background at low energies. Consequently, we use an interplay between experimental data and carefully tuned theoretical calculations to generate the total inelastic cross section. [ABSTRACT FROM AUTHOR]

The results of a neutron inelastic scattering experiment performed at the Geel Electron Linear Accelerator pulsed white neutron source of the European Commission Joint Research Centre are reported. The neutrons with energies up to 18 MeV interacted with a natTi sample and the γ rays resulting from inelastic scattering reactions on the stable isotopes were detected using the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. We were able to measure the γ-production cross sections for 21 transitions in the five stable Ti isotopes. From these, the level cross sections and the total inelastic cross sections were determined. Our experimental results are compared with theoretical calculations performed using the talys 1.8 code, evaluated nuclear data libraries, and also with previously reported results. [ABSTRACT FROM AUTHOR]

The strength functions of the π f 5 / 2 , π p 3 / 2 and π f 7 / 2 orbitals in neutron-rich 71 Cu were obtained in a 72 Zn(d, 3 He) 71 Cu proton pick-up reaction in inverse kinematics using a radioactive beam of 72 Zn at 38 MeV/u. A dedicated set-up was developed to overcome the experimental challenges posed by the low cross section of the reaction and the low energy of the outgoing 3 He particles. The excitation-energy spectrum was reconstructed and spectroscopic factors were obtained after analysis of the angular distributions with the finite-range Distorted-Wave Born Approximation (DWBA). The results show that unlike for the π f 5 / 2 orbital and contrary to earlier interpretation, the π f 7 / 2 single-particle strength distribution is not appreciably affected by the addition of neutrons beyond N = 40 . [ABSTRACT FROM AUTHOR]

Excited states have been studied in 28Na using the β-decay of implanted 28Ne ions at the Grand Accelerateur National d'lons Lourds/LISE as well as the in-beam γ-ray spectroscopy at the National Superconducting Cyclotron Laboratory/S800 facility. New states of positive (Jπ = 3+,4+) and negative (Jπ = l--5-) parity are proposed. The former arise from the coupling between 0d5/2 protons and 0d3/2 neutrons, while the latter are attributable to couplings of 0d5/2 protons with 1 p3/2 or 0f1/2 neutrons. While the relative energies between the Jπ = l+-4+ states are well reproduced with the USDA interaction in the N = 17 isotones, a progressive shift in the ground-state binding energy (by about 500 keV) is observed between 26F and 30Al. This points to a possible change in the proton-neutron 0d5/2-0d3/2 effective interaction when moving from stability to the drip line. The presence of Jπ = 1--4- negative-parity states around 1.5 MeV as well as of a candidate for a Jπ = 5- state around 2.5 MeV give further support to the collapse of the N = 20 gap and to the inversion between the neutron 0f7/2 and 1p3/2 levels below Z = 12. These features are discussed in the framework of shell-model and energy-density-functional calculations, leading to predicted negative-parity states in the low-energy spectra of the 26F and 25O nuclei. [ABSTRACT FROM AUTHOR]

The structure of the 24F nucleus has been studied at GANIL using the β decay of 24O and the in-beam y-ray spectroscopy from the fragmentation of 27,28Na, 25,26<>Ne, and 29,30Mg nuclei. Combining these complementary experimental techniques, the level scheme of 24F has been constructed up to 3.6 MeV by means of particle-y and particle-yy coincidence relations. Experimental results are compared to shell-model calculations using the standard USDA and USDB interactions as well as ab initio valence-space Hamiltonians calculated from the in-medium similarity renormalization group based on chiral two- and three-nucleon forces. Both methods reproduce the measured level spacings well, and this close agreement allows unidentified spins and parities to be consistently assigned. [ABSTRACT FROM AUTHOR]