Auxiliary Monte Carlo Simulations Research Articles

Study of [formula omitted] and long-lived impurities produced in the [formula omitted] reactions using an electron beam

We discuss the possibility of producing M99o radioisotope using an electron beam accelerated in the linac injector of the SOLARIS synchrotron. M99o with a half-life of 65.94 h, is a parent of the medically important radioisotope T99mc(T1/2=6 h). In our study M99o was produced from Mnato(γ,x) reaction using Bremsstrahlung γ radiation generated by 60, 100 and 200 MeV electron beams hitting a tungsten radiator located in front of the target. The activity of M99o was analysed by off-line γ spectroscopy using a HPGe detector. Auxiliary Monte-Carlo simulations were performed to determine the flux and energy distribution of the Bremsstrahlung photons. The activity thus obtained is high enough to consider the feasibility for commercial purposes of the production of M99o through photo-nuclear reactions. Apart from the reaction of interest, the activity of other long-lived radioactive impurities produced from Mnato(γ,x) reactions were determined.

Experimental study of the 197Au(n,2n) reaction cross section

In the present work, the 197Au(n,2n) reaction cross section is experimentally determined relative to the 27Al(n,α)24Na reaction at incident neutron energies of 9.0 to 10.5 MeV by means of the activation technique. The quasi-monoenergetic fast neutron beam was produced via the 2H(d,n)3He reaction at the 5.5 MV Tandem Van de Graaff accelerator at the NCSR “Demokritos” and was studied to determine the contribution of background “parasitic” neutrons using the multiple foil activation technique and the SULSA unfolding code. The cross sections for the population of the second isomeric state (12−) of 196Au and the sum of the ground (2−) and first isomeric state (5−) population cross sections were independently determined. Auxiliary Monte Carlo simulations were performed with the MCNP code.

Measurement of the 234U(n, f ) cross-section with quasi-monoenergetic beams in the keV and MeV range using a Micromegas detector assembly

The 234U neutron-induced fission cross-section has been measured at incident neutron energies of 452, 550, 651 keV and 7.5, 8.7, 10 MeV using the 7Li (p, n) and the 2H(d, n) reactions, respectively, relative to the 235U(n, f ) and 238U(n, f ) reference reactions. The measurement was performed at the neutron beam facility of the National Center for Scientific Research “Demokritos”, using a set-up based on Micromegas detectors. The active mass of the actinide samples and the corresponding impurities were determined via $ \alpha$ -spectroscopy using a surface barrier silicon detector. The neutron spectra intercepted by the actinide samples have been thoroughly studied by coupling the NeuSDesc and MCNP5 codes, taking into account the energy and angular straggling of the primary ion beams in the neutron source targets in addition to contributions from competing reactions (e.g. deuteron break-up) and neutron scattering in the surrounding materials. Auxiliary Monte Carlo simulations were performed making combined use of the FLUKA and GEF codes, focusing particularly on the determination of the fission fragment detection efficiency. The developed methodology and the final results are presented.

Cross section of the 197Au(n,2n)196Au reaction

The 197 Au(n,2n)196 Au reaction cross section has been measured at two energies, namely at 17.1 MeV and 20.9 MeV, by means of the activation technique, relative to the 27 Al(n,α)24 Na reference reaction cross section. Quasi-monoenergetic neutron beams were produced at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR “Demokritos”, by means of the 3 H(d,n)4 He reaction, implementing a new Ti-tritiated target of ∼ 400 GBq activity. The induced γ-ray activity at the targets and reference foils has been measured with HPGe detectors. The cross section for the population of the second isomeric (12− ) state m2 of 196 Au was independently determined. Auxiliary Monte Carlo simulations were performed using the MCNP code. The present results are in agreement with previous experimental data and with theoretical calculations of the measured reaction cross sections, which were carried out with the use of the EMPIRE code.

Neutron-induced fission cross-section measurement of 234U with quasi-monoenergetic beams in the keV and MeV range using micromegas detectors

Accurate data on neutron-induced fission cross-sections of actinides are essential for the design of advanced nuclear reactors based either on fast neutron spectra or alternative fuel cycles, as well as for the reduction of safety margins of existing and future conventional facilities. The fission cross-section of $^{234}$U was measured at incident neutron energies of 560 and 660 keV and 7.5 MeV with a setup based on ‘microbulk’ Micromegas detectors and the same samples previously used for the measurement performed at the CERN n_TOF facility (Karadimos et al., 2014). The $^{235}$U fission cross-section was used as reference. The (quasi-)monoenergetic neutron beams were produced via the 7Li(p,n) and the 2H(d,n) reactions at the neutron beam facility of the Institute of Nuclear and Particle Physics at the ‘Demokritos’ National Centre for Scientific Research. A detailed study of the neutron spectra produced in the targets and intercepted by the samples was performed coupling the NeuSDesc and MCNPX codes, taking into account the energy spread, energy loss and angular straggling of the beam ions in the target assemblies, as well as contributions from competing reactions and neutron scattering in the experimental setup. Auxiliary Monte-Carlo simulations were performed with the FLUKA code to study the behaviour of the detectors, focusing particularly on the reproduction of the pulse height spectra of α-particles and fission fragments (using distributions produced with the GEF code) for the evaluation of the detector efficiency. An overview of the developed methodology and preliminary results are presented.

Investigation of theAm241(n,2n)Am240cross section

The $^{241}\mathrm{Am}(n,2n)^{240}\mathrm{Am}$ reaction cross section has been measured at four energies, 10.0, 10.4, 10.8, and 17.1 MeV, by means of the activation technique, relative to the $^{27}\mathrm{Al}(n,\ensuremath{\alpha})^{24}\mathrm{Na}$ reaction reference cross section. Quasi-monoenergetic neutron beams were produced via the $^{2}\mathrm{H}(d,n)^{3}\mathrm{He}$ and the $^{3}\mathrm{H}(d,n)^{4}\mathrm{He}$ reactions at the 5.5 MV Tandem T11/25 accelerator laboratory of NCSR ``Demokritos''. The high purity $^{241}\mathrm{Am}$ targets were provided by JRC-IRMM, Geel, Belgium. The induced $\ensuremath{\gamma}$-ray activity of $^{240}\mathrm{Am}$ was measured with high-resolution high-purity germanium (HPGe) detectors. Auxiliary Monte Carlo simulations were performed with the mcnp code. The present results are in agreement with data obtained earlier and predictions obtained with the empire code.

Isomeric cross section of theAu197(n,2n) reaction

In the present work, the $^{197}\mathrm{Au}$($n,2n$) reaction cross section is experimentally determined relative to the $^{27}\mathrm{Al}$($n,\ensuremath{\alpha}$)$^{24}\mathrm{Na}$ reaction at incident neutron energies of 9.0--10.5 MeV by means of the activation technique. The quasimonoenergetic fast neutron beam was produced via the $^{2}\mathrm{H}$($d,n$)$^{3}\mathrm{He}$ reaction at the 5.5-MV Tandem Van de Graaff accelerator at the National Centre of Scientific Research (NCSR) ``Demokritos'' and was studied to determine the contribution of background ``parasitic'' neutrons using the multiple foil activation technique and the SULSA unfolding code. The cross sections for the population of the second isomeric state (${12}^{\ensuremath{-}}$) of $^{196}\mathrm{Au}$ and the sum of the ground (${2}^{\ensuremath{-}}$) and first isomeric state (${5}^{\ensuremath{-}}$) population cross sections were independently determined. Auxiliary Monte Carlo simulations were performed with the MCNP code. Theoretical calculations of the above cross sections in the 8--25 MeV region were carried out with the use of the STAPRE-F, EMPIRE, and TALYS codes, which were also compared in their implementation of the generalized superfluid model. The theoretical results are compared with previous work in the same mass region, and the strong dependence on the level scheme of the nuclei involved was revealed.