Production of noble gas isotopes by proton-induced reactions on lead
Université de Liège, Institut de Physique, Sart Tilman, Liège, BelgiumNuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms (Impact Factor: 1.12). 02/2005; 229(1):1-23. DOI: 10.1016/j.nimb.2004.11.009
We measured integral thin target cross sections for the proton-induced production of He-, Ne-, Ar-, Kr- and Xe-isotopes from lead from the respective reaction threshold up to 2.6 GeV. The production of noble gas isotopes from lead is of special importance for design studies of accelerator driven nuclear reactors and/or energy amplifiers. For all experiments with proton energies above 200 MeV a new mini-stack approach was used instead of the stacked-foil technique in order to minimise the influences of secondary particles on the residual nuclide production. About 420 cross sections for 23 nuclear reactions were determined. The phenomenology of the determined excitation functions enables us to distinguish between the different reaction modes fragmentation, hot and cold symmetric fission, asymmetric fission and deep spallation. Cross sections for the production of 21Ne and 38Ar measured below 100 MeV and 200 MeV, respectively, enable us to study nuclide production below the nominal Coulomb-barrier. The experimental data are compared to results from the theoretical nuclear model code INCL4/ABLA. While the model describes the production of 4He reasonably well, it underestimates the cross sections for Ne- and Ar-isotopes produced via deep spallation and/or multifragmentation by up to two orders of magnitude. For the Kr- and Xe-isotopes the agreement between modelled and measured data strongly depends on the reaction mechanisms. While INCL4/ABLA describes the production of n-poor Kr-isotopes via hot-symmetric fission and the production of Xe-isotopes via asymmetric fission reasonably well, i.e. within a factor of 2, the discrepancies between modelled and measured cross sections for the n-rich Kr-isotopes produced via cold symmetric fission are significantly larger. For the Xe-isotopes produced via spallation, i.e. at energies higher than about 600 MeV, the model completely fails to describe the experimental data. Therefore, the comparison of measured and modelled thin target cross sections clearly indicates that experimental data are still needed because the predictive power of nuclear model codes, though permanently improving, does still not allow to reliably predict the cross sections needed for most applications and irradiation experiments remain indispensable.
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ABSTRACT: Absolute cross sections, energy spectra, and angular distributions have been measured for 1,2,3H, 3,4,6He, 6,7,8,9Li and 7,9,10Be isotopes produced in 1.2 GeV proton-induced spallation reactions with targets between Al and Th. Results of simulation calculations with the intra-nuclear cascade code INCL2.0 coupled to the statistical model GEMINI are in good agreement with these data, as to charged-particle evaporation, mean excitation energy, and mean linear momentum transfer. The pre-equilibrium emission of composite particles, not accounted for in these simulations, however, typically contributes to the total production of composite particles by 40–60% for 2H and 3He, 20–40% for 3H, 5–20% for 4He, and about 15–25% for Li and Be. The composite pre-equilibrium particles together carry off a mean energy of up to 50 MeV, i.e., about 30% compared to the mean energy released by particle evaporation. For deuterons, pre-equilibrium emission is shown to be well described by surface coalescence while definitely other mechanisms are required for 4He and heavier clusters.Nuclear Physics A 02/2006; 765(3-4-765):426-463. DOI:10.1016/j.nuclphysa.2005.10.014 · 2.20 Impact Factor
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ABSTRACT: Reliable nuclear data on spectra and total hydrogen and helium (gas) production cross sections from various reactions are needed for fundamental studies and many applications. So, we need the gas-production cross sections by nucleons in accelerator-driven systems to evaluate the material damage; the kinetic energy released in matter (kerma) determined predominantly by hydrogen and helium production cross sections is of first importance for radiotherapy and radiation protection; such data are needed for astrophysics, etc. It is impossible to measure all needed data, therefore reliable models able to predict such data are required. All previous versions of the Cascade-Exciton Model (CEM) and of the Los Alamos Quark-Gluon String Model (LAQGSM) described gas-production cross sections only roughly and not well enough, just as many other similar models do. This is why we addressed recently this problem in the latest version of our codes CEM03.01 and LAQGSM03.01, improving significantly our description of both the spectra and total gas-production cross sections. A part of this work is presented here.The American Nuclear Society 14th Biennial Meeting on the Radiation Protection and Shielding Division, Carlsbad, New Mexico, USA; 04/2006
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ABSTRACT: We measured integral thin target cross-sections for the proton-induced production of He-, Ne-, Ar-, Kr-, and Xe-isotopes from lead and bismuth from the respective reaction threshold up to 2.6 GeV. The production of noble gas isotopes from lead and bismuth is of special importance for design studies of accelerator driven nuclear reactors and/or energy amplifiers. For all experiments with proton energies above 200 MeV a new mini-stack approach was used instead of the stacked-foil technique in order to minimise influences of secondary particles. The phenomenology of the determined excitation functions enables us to distinguish between the different reaction modes fragmentation, hot and cold symmetric fission, asymmetric fission, and deep spallation. For lead more than 420 cross-sections for 23 nuclear reactions have been measured. While the lead data have already been published, here we present first results for the production of noble gas isotopes from bismuth. The experimental data are compared to results from the theoretical nuclear model code INCL4/ABLA. This comparison clearly indicates that experimental data are still needed because the predictive power of nuclear model codes, though permanently improving, does still not allow to reliably predict the cross-sections needed for most applications and irradiation experiments remain indispensable.Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 06/2006; 562(2):760–763. DOI:10.1016/j.nima.2006.02.049 · 1.22 Impact Factor
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