Persistent success of the orbiting cluster model of heavy-ion resonances

The orbiting cluster model is applied to the basic presently available data on resonances in heavy-ion-induced reactions. The model is shown to correctly predict the presence of resonances and give a good overall agreement with the measured resonance energies

Optimizing performances of CsI(Tl) crystals with a photodiode readout

Tests are described concerning the performances of CsI(Tl) crystals. Particular care was dedicated to the study of the light production and collection of the crystals, that appear to be significantly a⁄ected both by the choice of the wrapping materials and by the details of the binding technique. A functional relation between the light pulse height and the coupling of the crystal#photodiode system was deduced. Finally, the influence of this coupling on the energy resolution of the detector is discussed. ( 1999 Elsevier Science B.V. All rights reserved

Measurement of the neutron capture cross sections of 233U, 237Np, 240,242Pu, 241,243Am and 245Cm with a total absorption calorimeter at n_TOF

Proposal: Measurement of the neutron capture cross sections of 233U, 237Np, 240,242Pu, 241,243Am and 245Cm with a Total Absorption Calorimeter at n_TOFAccurate and reliable neutron capture cross section data for actinides are necessary for the proper design, safety regulation and precise performance assessment of transmutation devices such as Fast Critical Reactors or Accelerator Driven Systems (ADS). The goal of this proposal is the measurement of the neutron capture cross sections of 233U, 237Np, 240,242Pu, 241,243Am and 245Cm at n_TOF with an accuracy of 5%. 233U plays an essential role in the Th fuel cycle, which has been proposed as a safer and cleaner alternative to the U fuel cycle. The capture cross sections of 237Np, 240,242Pu, 241,243Am and 245Cm play a key role in the design and optimization of a strategy for the Nuclear Waste Transmutation. A high accuracy can be achieved at n_TOF in such measurements due to a combination of features unique in the world: high instantaneous neutron fluence and excellent energy resolution of the facility, innovative Data Acquisition System based on flash ADCs and the use of a high performance Total Absorption Calorimeter as a detection device.Postprint (published version

Evidence of non-statistical structures in the elastic and inelastic scattering of58Ni+58Ni and58Ni+62Ni and intermediate dinuclear states

Excitation functions and angular distributions of58Ni+58Ni and58Ni+62Ni scattering at energies just above the Coulomb barrier have been measured aroundθcm=90° in energy stepsΔEcm=0.25 MeV fromEcm ⋍ 110 MeV toEcm ⋍ 120 MeV for58Ni+58Ni and fromEcm ⋍ 110 MeV toEcm ⋍ 118 MeV for58Ni+62Ni. Evidence for structure of non-statistical character has been found in the angle-summed excitation functions; this evidence is corroborated by the analysis of the angular distributions. This is the first time that non-statistical structure in elastic and inelastic scattering is reported with high confidence level for this mass and excitation energy ranges. Attempts are presented to understand the nature of this structure, including the presence of intermediate dinuclear states and virtual states in a potential well

Measurements of fission cross sections of actinides

A measurement of the neutron induced fission cross sections of 237Np, 241,243Am and of 245Cm is proposed for the n_TOF neutron beam. Two sets of fission detectors will be used: one based on PPAC counters and another based on a fast ionization chamber (FIC). A total of 5E18 protons are requested for the entire fission measurement campaign.Postprint (author's final draft

Application of Photon Strength Functions to (n,g ) measurements with the n_TOF TAC

The neutron capture cross section measurements at the CERN n_TOF facility are performed using a new detection system, the segmented Total Absorption Calorimeter (TAC). All measurements are performed in reference to the well known Au σ(n,γ). The accuracy of the measurements depends on the accuracy of the TAC detection efficiency, which is calculated by means of Monte Carlo simulations. In this MC simulation photon strength functions and level densities play a major role as ingredients used for the generation of primary events, that is the electromagnetic cascades following the (n,γ) process. We have calculated the TAC detection efficiency for the case of Au (n,γ) by adjusting the photon strength functions of Au so that the simulation reproduces the experimental data. Both the MC method and the uncertainty of the results are discussed

The 93Zr(n, γ) reaction up to 8 keV neutron energy

The (n,γ) reaction of the radioactive isotope 93Zr has been measured at the n-TOF high-resolution time-of-flight facility at CERN. Resonance parameters have been extracted in the neutron energy range up to 8 keV, yielding capture widths smaller (14%) than reported in an earlier experiment. These results are important for detailed nucleosynthesis calculations and for refined studies of waste transmutation concepts.EC FIKW-CT-2000-0010

Study of the background in the measuring station at the n_TOF facility at CERN: sources and solutions

A background roughly two orders of magnitude higher than tolerable was found in the n_TOF facility at CERN during the first measurements. This note describes a series of additional measurements performed in the n_TOF experimental area to study the origin and the characteristics of the background. The program of these measurements was determined taking into account the results from the simulations carried out by the EET group. A first phase of measurements confirmed the results of the simulations, namely that the dominant source of background was due to neutrons generated by negative muon capture. Actions to reduce the background were taken according to the results from both measurements and simulations. An iron shielding wall 3.2 m thick was then placed in between the sweeping magnet and the second collimator, with the purpose of stopping most of the muons. In a second phase of measurements, results showed that the additional shielding reduced the main component of the background by about a factor of 30.Postprint (author's final draft

Optimizing performances of CsI(Tl) crystals with a photodiode readout

Abstract Tests are described concerning the performances of CsI(Tl) crystals. Particular care was dedicated to the study of the light production and collection of the crystals, that appear to be significantly affected both by the choice of the wrapping materials and by the details of the binding technique. A functional relation between the light pulse height and the coupling of the crystal#photodiode system was deduced. Finally, the influence of this coupling on the energy resolution of the detector is discussed