MCNP6 fragmentation of light nuclei at intermediate energies

Abstract

Fragmentation reactions induced on light target nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the latest Los Alamos Monte Carlo transport code MCNP6 and with its cascade-exciton model (CEM) and Los Alamos version of the quark-gluon string model (LAQGSM) event generators, version 03.03, used as stand-alone codes. Such reactions are involved in different applications, like cosmic-ray-induced single event upsets (SEU's), radiation protection, and cancer therapy with proton and ion beams, among others; therefore, it is important that MCNP6 simulates them as well as possible. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after INC. Both CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to He4 from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codes.Comment: 31 pages, 27 figures, submitted to Nucl. Instrum. Methods

Total reaction cross sections in CEM and MCNP6 at intermediate energies

“…(For more information about the stages of CEM in its model of spallation reactions, see Ref. [2,3,9].) Better total reaction (inverse) cross section models are available now [10][11][12][13][14][15][16][17][18][19][20][21].…”

Determination of integral cross sections of3H in Al foils monitors irradiated by protons with energies ranging from 40 to 2600 MeV

“…Nevertheless, as shown in this work, the obtained results can certainly be used to verify the nuclear models of radiation transport codes. 3 H activity in Al foil was determined using a low-background spectrometric α-, β-radiometer, Quantilus 1220, and a system of automatic sample preparation, A307 Sample Oxidizer. An analysis of the measured β-spectra was carried out with the SpectraDec code [6].…”

“…This stimulates an interest in the study of the production cross-sections of this nuclide in different structural materials of nuclear installations. A compilation of the experimental values of the cross-sections of the reaction Al(p,x) 3 H, taken from data libraries [1,2] and together with values obtained in this work in comparison with the simulated data both in [3] and in this work are presented in Fig. 1 Figure 1: Al(p,x) 3 H reaction cross-sections measured in [1,2], simulated [3] as well as obtained in this work.…”

Neutron spallation measurements and impacts on low-background experiments

“…With regard to the model, there are several possible explanations: the incoming neutron spectrum might be different than assumed, the cross-section libraries (typically available for energies below ~150 MeV) might be insufficient between materials, or more likely, the use of the Bertini model for simulating the INC process might cause the observed differences. This focus on the Bertini model as being the most likely cause derives from a recent comprehensive study by Mashnik & Kerby [38] and references therein, where they compare a large body of proton-beam induced fragmentation data from light targets to the using the Cascade-Exciton Model (CEM03.03) implemented in the MCNP6.1 replacement to MCNPX. Those results show very good agreement (better than factors of 2) with all the targets including aluminum.…”

“…Publications on spallation production from these light nuclei are limited and not directly applicable to the energies of interest here [38,39,40,41,42]. The reported disagreement between data and models is often a factor of two.…”