Production of noble gas isotopes by proton-induced reactions on lead
ABSTRACT 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: We measured integral thin target cross sections for the proton-induced production of 3He, 4He, 21Ne, 22Ne, 36Ar and 38Ar from Fe and Ni from the respective reaction thresholds up to 1.6GeV. The production of noble gas isotopes, especially 4He, from Fe and Ni is of special importance for design studies of accelerator driven systems and/or energy amplifier, because Fe is the main structural material in almost every design study. Furthermore, the cross sections are needed to establish the first physical model calculations for the production of cosmogenic nuclides in iron meteorites. As a result of our new measurements there now exist for both target elements a complete and consistent database for the production of noble gas isotopes. The experimental data are compared to results from the theoretical nuclear model codes INCL4/ABLA and TALYS. This comparison clearly demonstrates again that experimental data are still needed because the predictive power of nuclear model codes, though permanently improving, does still not allow reliably predicting the cross sections needed for most applications and irradiation experiments remain indispensable.Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2008; 266(1):2-12. · 1.19 Impact Factor
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ABSTRACT: Reliable predictions of light charged particle production in spallation reactions are important to correctly assess gas production in spallation targets. In particular, the helium production yield is important for assessing damage in the window separating the accelerator vacuum from a spallation target, and tritium is a major contributor to the target radioactivity. Up to now, the models available in the MCNPX transport code, including the widely used default option Bertini-Dresner and the INCL4.2-ABLA combination of models, were not able to correctly predict light charged particle yields. The work done recently on both the intranuclear cascade model INCL4, in which cluster emission through a coalescence process has been introduced, and on the de-excitation model ABLA allows correcting these deficiencies. This paper shows that the coalescence emission plays an important role in the tritium and $^3He$ production and that the combination of the newly developed versions of the codes, INCL4.5-ABLA07, now lead to good predictions of both helium and tritium cross sections over a wide incident energy range. Comparisons with other available models are also presented. Comment: 6 pages, 9 figuresNuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 11/2009; · 1.19 Impact Factor
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ABSTRACT: In the past years, INC models simulating spallation reactions have been undergoing considerable development, and their results are more and more scrutinized by experimental work. Recently, IAEA has led an international collaboration to independently benchmark various INC models. The preliminary results of this collaboration indicate that while the Bertini model performs well in predicting neutron production, it greatly lacks the capability to predict light charged particle emission compared to CEM’03 and INCL. This drives us to completely reevaluate the NCSU radiation damage cross section database, which was developed 7 years ago using a combination of CEM2k and Bertini models for benchmarking experimental data. The reevaluation currently involves just the CEM’03 model in MCNPX due our limited code access. Our preliminary results are in reasonable agreement with the NCSU database for the helium and hydrogen production cross section, but there are obvious differences for the displacement cross section. Such similarities and differences are being investigated, and the validity of the CEM’03 model for predicting radiation damage to materials is being examined. The reevaluated radiation damage cross sections presented in this paper are used in calculating radiation damage to the target assembly currently running at SNS, and the results are compared with those of previous studies.Journal of Nuclear Materials 12/2012; 431(s 1–3):33–38. · 2.02 Impact Factor