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Induced radioactivity in particle accelerators is currently not sufficiently addressed, particularly for radiotherapy electron LINACs when the activation occurs via secondary neutrons created in photo-nuclear reactions. Methodologies based on Monte-Carlo simulations coupled with activation calculation codes are often used to address this issue. Their accuracy, which is potentially affected by the limited capabilities of the calculation tools to simulate nuclear reactions at the origin of the materials activation, can be deeply analyzed only through comparisons with experimental values but the latter are not widely available. New macroscopic data for the activity induced by neutrons in the materials commonly present in medical electron LINACs are presented. Neutron-induced activation has been measured by sample irradiation at SPIRAL2/NFS facility in accurately characterized configurations. Experimental results were compared to the simulations predictions allowing to assess the precision that can be achieved by a fully simulation-based methodology, mainly related to the energy-dependent reaction cross-sections. [ABSTRACT FROM AUTHOR]

This paper introduces a novel concept of the pulsed neutron facility (PNF) for maximizing the production of the thermal neutrons and its application to medical use based on prompt gamma neutron activation analysis (PGNAA) using Monte Carlo simulations.The PNF consists of a compact D-T neutron generator, a graphite pile, and a detection system using Cadmium telluride (CdTe) detector arrays. The configuration of fuel pins in the graphite monolith and the design and materials for the moderating layer were studied to optimize the thermal neutron yields. Biological samples – normal and cancerous breast tissues – including chlorine, a trace element, were used to investigate the sensitivity of the characteristic γ-rays by neutron-trace material interactions and the detector responses of multiple particles.Around 90 % of neutrons emitted from a deuterium-tritium (D-T) neutron generator thermalized as they passed through the graphite stockpile. The thermal neutrons captured the chlorines in the samples, then the characteristic γ-rays with specific energy levels of 6.12, 7.80 and 8.58 MeV were emitted. Since the concentration of chlorine in the cancerous tissue is twice that in the normal tissue, the count ratio of the characteristic γ-rays of the cancerous tissue over the normal tissue is approximately 2.

The Surrogate Ratio Method (SRM) was employed in the first experimental determination of the 231Th(n,f) cross section, relative to the 235U(n,f) cross section, over an equivalent neutron energy range of 360 keV to 10 MeV. The 230Th(n,f) cross section was also deduced using the SRM, relative to the 234U(n,f) cross section, over an equivalent neutron energy range of 220 keV to 25 MeV. The desired compound nuclei were populated using (3He,3He) and (3He) reactions on targets of 232Th and 236U and relative fission decay probabilities were measured. The surrogate 230,231Th(n,f) cross sections were compared to cross section evaluations and directly-measured experimental data, where available.

Abstract: A few years ago, the neutron time-of-flight facility n_TOF was built at CERN to address some of the urgent needs of high-accuracy nuclear data for Accelerator Driven Systems and other advanced nuclear energy systems, as well as for nuclear astrophysics and fundamental nuclear physics. Thanks to the characteristics of the neutron beam, and to state-of-the-art detection and acquisition systems, high quality neutron cross-section data have been obtained for a variety of isotopes, many of which radioactive. Following an important upgrade of the spallation target and of the experimental area, a new measurement campaign has started last year. After a brief review of the most important results obtained so far at n_TOF, the new features of the facility are presented, together with the first results on the commissioning of the neutron beam. The plans for future measurements, in particular related to nuclear technology are finally discussed. [Copyright &y& Elsevier]

Abstract: We determined neutron excitation functions from the respective reaction thresholds up to 1.6GeV for almost 100 target-product combinations relevant for cosmochemical, geochemical, and technological applications. We started with thick target production rates that have been obtained by irradiating iron and stone spheres with protons having energies between 600MeV and 1.6GeV. From the particle spectra of primary protons, secondary protons, and secondary neutrons, and the usually well known cross sections for the proton-induced reactions we calculated the production rates only due to protons. By subtracting these data from the measured total production rates we obtained production rates only due to secondary neutrons. With the modelled neutron spectra, guess functions calculated using nuclear model codes, and sophisticated energy-dependent deconvolution procedures we were able to determine almost 100 neutron excitation functions with their uncertainties. With the thus obtained neutron cross sections we are able to describe the experimental production rates in the thick target experiments, meteorites, the lunar surface, and terrestrial surface samples usually within the uncertainties, i.e., to within 10–15%. The adjusted neutron cross sections (a posteriori) are compared to results from the theoretical nuclear model codes INCL4.5/ABLA07 and TALYS. The TALYS code usually describes the a posteriori data reasonably well, i.e., mostly within a factor of a few. The quality of the INCL4.5+ABLA07 predictions depends on the reaction type and increases with increasing number of ejectiles, i.e., increasing target-product mass difference. The neutron cross section database, though successful in quantifying production rates in terrestrial and extraterrestrial matter, presents by no means a final step and experiments with quasi-monoenergetic neutrons are needed. [Copyright &y& Elsevier]

The cross sections for the Sn ( n, α)Cd, Sn ( n, α)Cd and Sn ( n, α)Cd reactions have been measured in the neutron energy range of 13.5-14.6 MeV using the activation technique and a coaxial HPGe γ-ray detector. The fast neutrons were produced by the T (d, n) He reaction. The neutron energies in the measurements were determined by cross section ratios for Nb( n,2 n)Nb and Zr( n, 2 n)Zr reactions. The results of present work were discussed and compared with theoretical calculation data, measurement results found in the literature and with the comprehensive evaluation data in ENDF/B-VII.0, CENDL-3.1, JENDL-4.0 libraries. [ABSTRACT FROM AUTHOR]

Abstract: Double-differential cross sections of inclusive light-ion (p, d, t, 3He and α) production in carbon induced by 96 MeV neutrons have been measured at eight laboratory angles from 20° to 160° in steps of 20°. Experimental techniques, as well as procedures for data taking and data reduction, are presented. Deduced energy-differential and production cross sections are herewith reported. Experimental cross sections are compared with theoretical reaction model calculations and experimental data in the literature. The measured production cross sections for protons, deuterons, tritons, 3He, and α particles support the trends suggested by data at lower energies. Deduced partial kerma coefficients for carbon are also shown. [ABSTRACT FROM AUTHOR]

Abstract: Neutron cross sections for a complete set of Dy isotopes, 156,158,160,161,162,163,164Dy, were evaluated in the incident energy range from 10−5 eV to 20MeV. In the low energy region, including thermal and resolved resonances, our evaluations are based on the latest data published in the Atlas of Neutron Resonances. In the unresolved resonance region we performed additional evaluation by using the averages of the resolved resonances and adjusting them to the experimental data. In the fast neutron region, we used the nuclear reaction model code EMPIRE-2.19 with the model parameters adjusted to the experimental data. The results are compared with the available experimental data and with the existing nuclear data libraries, including ENDF/B-VI.8 and JEFF-3.1. The new evaluations are suitable for neutron transport calculations and they were adopted by the new US evaluated nuclear data library, ENDF/B-VII.0, released in December 2006. [Copyright &y& Elsevier]

Abstract: Cross sections which is relevant in research of neutron transmutation doping of some important semiconducting materials were measured at neutron energies from 13.5 to 14.8MeV for the reactions 75As(n,2n)74As, 75As(n,p)75m+gGe, 75As(n,α)72m+gGa by activation relative to the 27Al(n,α)24Na reaction. Measurements were carried out by γ-detection using a coaxial HPGe detector. Natural realgar (As2S2) powder of 99.9% purity was used as samples. Fast neutrons were produced by the T(d,n)4He reaction. The results obtained are compared with existing data. [Copyright &y& Elsevier]

Abstract: In support of the Stewardship Science Academic Alliances initiative, an experimental program has been developed at Triangle Universities Nuclear Laboratory (TUNL) to measure (n,xn) cross-sections with both in-beam and activation techniques with the goal of improving the partial cross-section database for the NNSA Stockpile Stewardship Program. First experimental efforts include excitation function measurements on 235,238U and 241Am using pulsed and monoenergetic neutron beams with E n =5–15MeV. Neutron-induced partial cross-sections were measured by detecting prompt γ rays from the residual nuclei using various combinations of clover and planar HPGe detectors in the TUNL shielded neutron source area. Complimentary activation measurements using DC neutron beams have also been performed in open geometry in our second target area. The neutron-induced activities were measured in the TUNL low-background counting area. In this presentation, we include detailed information about the irradiation procedures and facilities and preliminary data on first measurements using this capability. [Copyright &y& Elsevier]

Abstract: A new method for correcting charged-particle spectra for thick-target effects is described. Starting with a trial function, inverse response functions are found by an iterative procedure. The variances corresponding to the measured spectrum are treated similarly and in parallel. Oscillations of the solution are avoided by rebinning the data to finer bins during a correction iteration and back to the original or wider binning after each iteration. This thick-target correction method has been used for data obtained with the MEDLEY facility at the The Svedberg Laboratory, Uppsala, Sweden, and is here presented in detail and demonstrated for two test cases. [Copyright &y& Elsevier]

Abstract: The cross sections for the reactions 115In(n, p)115gCd, 115In(n, α)112Ag, 115In(n, 2n)114mIn, 113In(n, 2n)112mIn, 115In(n, n′)115mIn, and 113In(n, n′)113mIn induced by 14MeV neutrons have been measured by activation relative to the 27Al(n, α)24Na. Measurements were carried out by γ-detection using a coaxial HPGe detector. As samples, natural indium has been used. The fast neutrons were produced by the T(d, n)4He reaction. The results obtained are compared with existing data. [Copyright &y& Elsevier]

Abstract: Double-differential cross sections for neutron-induced light-ion production at 96 MeV have been measured for a variety of nuclei at The Svedberg Laboratory. Using the measured cross-section data, we deduce the Kerma coefficient from carbon and oxygen for p, d, t, 3He and α particles. In order to get the total Kerma for C and O, we add GNASH calculation values where experimental data are not available and obtain a Kerma coefficient of 7.85 ± 0.63 fGy m2 for carbon and 7.09 ± 0.57 fGy m2 for oxygen. The C/O Kerma coefficient ratio then becomes 1.11 ± 0.11. In addition we determine the Kerma ratio between ICRU muscle and A-150, again adding calculations with the GNASH code where no experimental data are available, and obtain a value of 0.98 ± 0.05. While the Kerma coefficients for carbon and oxygen do not agree with the prediction in ICRU Report 63, the ratio values are in good agreement with existing predictions. [ABSTRACT FROM AUTHOR]

Abstract: The cross sections for the reactions 89Y(n, 2n) 88m+gY and 89Y(n, α) 86m+gRB induced by 14MeV neutrons have been measured using the activation technique and a coaxial HPGe γ-ray detector. Spectroscopically pure Y2O3 powder was used. Fast neutrons were produced by the T(d, n) 4He reaction. The neutron fluencies were determined using the monitor reaction 93Nb(n, 2n) 92mNb. [Copyright &y& Elsevier]