The SPES project: a second generation ISOL facility

Abstract SPES is an INFN project to develop a Radioactive Ion Beam facility as an intermediate step toward EURISOL, the next generation European ISOL facility. The facility will be installed at the Laboratori Nazionali di Legnaro where the superconductive linac ALPI will reaccelerate the exotic beams at energies larger than 10 AMeV. Neutron-rich radioactive beams will be produced by proton-induced Uranium fission at an expected in-target fission rate of 1013 fissions per second. As proton driver, a 70 MeV cyclotron with a total current of 0.750 mA shared on two exit ports will be installed. The key feature of SPES is to provide high intensity and high-quality beams of neutron-rich nuclei to perform forefront research in nuclear physics as well as to develop and interdisciplinary research center based on the cyclotron proton beam. Neutron production at a rate of 1014 n/s is expected using the proton beam on thick target. The status of the project and the layout of the neutron facility will be presented. Two facilities can be operated at the same time, with a capability of 5000 h per year each. The ISOL facility will use 0.2 mA to reach the goal of 1013 fissions per second and more than 0.5 mA will be available for applied physics applications, mainly neutron beam and medical isotopes production

7 Li ( p , n ) 7 Be cross section from threshold to 1960 keV and precise measurement of the 197 Au ( n , γ ) spectrum-averaged cross section at 30 keV

Background: The 7 Li(p, n) 7 Be reaction is one of the most used nuclear reaction for accelerator-based neutron sources. There are few experimental cross section data in the double-value energy region and they are discrepant, as are the reaction yields. Purpose: We derive the 7 Li(p, n) 7 Be reaction cross section, and measure with small uncertainty the 197Au(n, γ ) 198Au spectrum-averaged cross section at neutron energy around 30 keV. Method: By irradiating Li metal targets over the proton energy range of 1879 to 1960 keV, thick target yields were measured using the generated 7 Be activity. Based on the theoretical description of the reaction yield, accelerator parameters and reaction cross sections are derived. Gold foils were activated with the neutron field generated by the (p, n) reaction on a Li target at a proton energy of about a half keV above the reaction threshold. Results: The thick target yield is well reproduced when the Breit-Wigner single-resonance formula for s-wave particles is used to describe the reaction cross section. The ratio between neutron and proton widths was found to be equal to n/p = 5.4 1 − Tth/Tp. The detailed balance principle is used to obtain the cosmologically important time-reversed 7 Be(n, p) 7 Li reaction cross section. The measured 197Au(n, γ ) 198Au spectrum-averaged cross section agrees with the value calculated from the ENDF/B-VIII.0 library. Conclusions: We demonstrated the feasibility of deriving the 7 Li(p, n) 7 Be reaction cross section from the thick target yield. Using the ratio between neutron and proton widths obtained in this work reduces the uncertainty in calculating the reaction cross section to a factor of 2.3.International Atomic Energy Agency Contract No. 17883. G.M.-

ANEM: A rotating composite target to produce an atmospheric-like neutron beam at the LNL SPES facility

A fast neutron (E> MeV) irradiation facility is under development at the 70 MeV SPES proton cyclotron at LNL (Legnaro, Italy) to investigate neutron-induced Single Event Effects (SEE) in microelectronic devices and systems. After an overview on neutron-induced SEE in electronics, we report on the progress in the design of ANEM (Atmospheric Neutron EMulator), a water-cooled rotating target made of Be and W to produce neutrons with an energy spectrum similar to that of neutrons produced by cosmic rays at sea-level. In ANEM, the protons from the cyclotron alternatively impinge on two circular sectors of Be and W of different areas; the effective neutron spectrum is a weighted combination of the spectra from the two sectors. In this contribution, we present the results of thermal-mechanical Finite Element Analysis (ANSYS) calculations of the performance of the ANEM prototype. The calculations at this stage indicate that ANEM can deliver fast neutrons with an atmospheric-like energy spectrum and with an integral flux [Formula: see text](1-70 MeV) [Formula: see text]107 n cm[Formula: see text]s[Formula: see text] that is 3×109 more intense than the natural one at sea-level: a very competitive flux for SEE testing

Status of the LEgnaro NeutrOn Source facility (LENOS)

Abstract LENOS is a new facility under development at Laboratori Nazionali di Legnaro (LNL). It is based on a new technic for neutron beam shaping in accelerator based neutron sources. The main advantage of this method is to be able to shape the primary charged-particle beam to a defined energy distribution that, impinging on a neutron producing target, generates the desired neutron spectra at the sample position. Together with the proton energy distribution, other degrees of freedom are used to obtain the desired neutron energy spectra, e.g. the angular distribution of produced neutrons, the nuclear reactions used for the neutron spectra production, and the convolution of neutron spectra coming from different target materials. The main advantage of this new approach is the good control over the energy and spatial distribution of the produced neutron spectrum avoiding most of the problems due to neutron moderation, since it is easier to work with charged particles than with neutrons. The goal of the LENOS facility is to obtain a Maxwell-Boltzmann neutron energy spectrum with tunable temperature and a high neutron flux at sample position by using the 7Li(p,n) reaction. To maximize the neutron flux a very narrow primary proton beam has to be used, so the target has to remove a very high specific power. Currently available lithium targets are inadequate to sustain the high specific power that needs to be dissipated in the LENOS facility. A dedicated target based on micro-channel geometry and liquid metal cooling has been developed and tested. This contribution describes the status of the LENOS facility

33S as a cooperative capturer for BNCT

33S is a stable isotope of sulfur for which the emission of an α-particle is the dominant exit channel for neutron-induced reactions. In this work the enhancement of both the absorbed and the equivalent biologically weighted dose in a BNCT treatment with 13.5keV neutrons, due to the presence of 33S, has been tested by means of Monte Carlo simulations. The kerma-fluence factors for the ICRU-4 tissue have been calculated using standard weighting factors. The simulations depend crucially on the scarce 33S(n,α)30Si cross-section data. The presence of a high resonance at 13.5keV was established by previous authors providing discrepant resonance parameters. No experimental data below 10keV are available. All of this has motivated a proposal of experiment at the n_TOF facility at CERN. A setup was designed and tested in 2011. Some results of the successful test will be shown. The experiment is scheduled for the period November to December 2012. © 2014 Elsevier Ltd

Excitation function shape and neutron spectrum of the Li 7 ( p , n ) Be 7 reaction near threshold

The forward-emitted low energy tail of the neutron spectrum generated by the $^{7}\mathrm{Li}(p,n)^{7}\mathrm{Be}$ reaction on a thick target at a proton energy of 1893.6 keV was measured by time-of-flight spectroscopy. The measurement was performed at BELINA (Beam Line for Nuclear Astrophysics) of the Laboratori Nazionali di Legnaro. Using the reaction kinematics and the proton on lithium stopping power the shape of the excitation function is calculated from the measured neutron spectrum. Good agreement with two reported measurements was found. Our data, along with the previous measurements, are well reproduced by the Breit-Wigner single-resonance formula for $s$-wave particles. The differential yield of the reaction is calculated and the widely used neutron spectrum at a proton energy of 1912 keV was reproduced. Possible causes regarding part of the 6.5% discrepancy between the ^{197}\mathrm{Au}(n,\ensuremath{\gamma}) cross section measured at this energy by Ratynski and Kappeler [Phys. Rev. C 37, 595 (1988)] and the one obtained using the Evaluated Nuclear Data File version B-VII.1 are given

Fast neutron production at the LNL Tandem from the 7^7Li(14^{14}N,xn)X reaction

Fast neutron beams are of relevance for many scientific and industrial applications. This paper explores fast neutron production using a TANDEM accelerator at the Legnaro National Laboratories, via an energetic ion beam (90 MeV $^{14}N$) onto a lithium target. The high energy models for nuclear collision of FLUKA foresee large neutron yields for reactions of this kind. The experiment aimed at validating the expected neutron yields from FLUKA simulations, using two separate and independent set-ups: one based on the multi-foil activation technique, and the other on the time of flight technique, by using liquid scintillator detectors. The results of the experiment show clear agreement of the measured spectra with the FLUKA simulations, both in the shape and the magnitude of the neutron flux at the measured positions. The neutron spectrum is centered around the 8 MeV range with mild tails, and a maximum neutron energy spanning up to 50 MeV. These advantageous results provide a starting point in the development of fast neutron beams based on high energy ion beams from medium-sized accelerator facilities

NEAR: A New Station to Study Neutron-Induced Reactions of Astrophysical Interest at CERN-n_TOF

We present NEAR, a new experimental area at the CERN-n_TOF facility and a possible setup for cross section measurements of interest to nuclear astrophysics. This was recently realized with the aim of performing spectral-averaged neutron-capture cross section measurements by means of the activation technique. The recently commissioned NEAR station at n_TOF is now ready for the physics program, which includes a preliminary benchmark of the proposed idea. Based on the results obtained by dedicated Monte Carlo simulations and calculation, a suitable filtering of the neutron beam is expected to enable measurements of Maxwellian Averaged Cross Section (MACS) at different temperatures. To validate the feasibility of these studies we plan to start the measurement campaign by irradiating several isotopes whose MACS at different temperatures have recently been or are planned to be determined with high accuracy at n_TOF, as a function of energy in the two time-of-flight measurement stations. For instance, the physical cases of 88Sr(n,γ ), 89Y(n,γ ), 94Zr(n,γ ) and 64Ni(n,γ ) are discussed. As the neutron capture on 89Y produces a pure β -decay emitter, we plan to test the possibility to perform activation measurements on such class of isotopes as well. The expected results of these measurements would open the way to challenging measurements of MACS by the activation technique at n_TOF, for rare and/or exotic isotopes of interest for nuclear astrophysic

First Results of the 140^{140}Ce(n,γ)141^{141}Ce Cross-Section Measurement at n_TOF

An accurate measurement of the $^{140}$Ce(n,γ) energy-dependent cross-section was performed at the n_TOF facility at CERN. This cross-section is of great importance because it represents a bottleneck for the s-process nucleosynthesis and determines to a large extent the cerium abundance in stars. The measurement was motivated by the significant difference between the cerium abundance measured in globular clusters and the value predicted by theoretical stellar models. This discrepancy can be ascribed to an overestimation of the $^{140}$Ce capture cross-section due to a lack of accurate nuclear data. For this measurement, we used a sample of cerium oxide enriched in $^{140}$Ce to 99.4%. The experimental apparatus consisted of four deuterated benzene liquid scintillator detectors, which allowed us to overcome the difficulties present in the previous measurements, thanks to their very low neutron sensitivity. The accurate analysis of the p-wave resonances and the calculation of their average parameters are fundamental to improve the evaluation of the $^{140}$Ce Maxwellian-averaged cross-section