Production of energetic light fragments in extensions of the CEM and LAQGSM event generators of the Monte Carlo transport code MCNP6

We extend the cascade-exciton model (CEM), and the Los Alamos version of the quark-gluon string model (LAQGSM), event generators of the Monte Carlo $N$-particle transport code version 6 (MCNP6), to describe production of energetic light fragments (LF) heavier than ${}^4\mathrm{He}$ from various nuclear reactions induced by particles and nuclei at energies up to about 1 TeV/nucleon. In these models, energetic LF can be produced via Fermi breakup, preequilibrium emission, and coalescence of cascade particles. Initially, we study several variations of the Fermi breakup model and choose the best option for these models. Then, we extend the modified exciton model (MEM) used by these codes to account for a possibility of multiple emission of up to 66 types of particles and LF (up to ${}^{28}\mathrm{Mg})$ at the preequilibrium stage of reactions. Then, we expand the coalescence model to allow coalescence of LF from nucleons emitted at the intranuclear cascade stage of reactions and from lighter clusters, up to fragments with mass numbers $A\le 7$, in the case of CEM, and $A\le 12$, in the case of LAQGSM. Next, we modify MCNP6 to allow calculating and outputting spectra of LF and heavier products with arbitrary mass and charge numbers. The improved version of CEM is implemented into MCNP6. Finally, we test the improved versions of CEM, LAQGSM, and MCNP6 on a variety of measured nuclear reactions. The modified codes give an improved description of energetic LF from particle- and nucleus-induced reactions; showing a good agreement with a variety of available experimental data. They have an improved predictive power compared to the previous versions and can be used as reliable tools in simulating applications involving such types of reactions.

Figure 1

Comparison of experimental ${}^6\mathrm{Li}$ spectra at 20, 45, 60, 90, and 110 degrees by Machner et al. [19] (open symbols) with calculations by the unmodified CEM03.03 (dashed histograms) and results by the newly revised CEM03.03F (solid histograms), as discussed in the text.

Figure 2

Excitation functions for the production of ${}^{14}\mathrm{C}$ and ${}^7\mathrm{Be}$, calculated with CEM03.03 using the “standard” version of the Fermi breakup model $\left(A_{\mathrm{Fermi}}=12\right)$ and with cutoff values $A_{\mathrm{Fermi}}$ of 14 and 16 (lines), as well as with MCNP6 using CEM03.$03(A_{\mathrm{Fermi}}=12$; solid points) compared with experimental data (open symbols), as indicated. Experimental data are from the T16 Lib compilation [35].

Figure 3

Examples of measured ${}^6\mathrm{Li}$ and ${}^7\mathrm{Be}$ double-differential spectra from $p+{}^9\mathrm{Be}$ at 190 MeV [36] (open symbols), compared to CEM results (histograms).

Figure 4

${}^4\mathrm{He}$ spectra at ${35}^{\circ }$ for 1.2, 1.9, and 2.5 GeV $p+{}^{12}\mathrm{C}$ measured by Fidelus of the PISA Collaboration [38] (solid symbols) compared to calculations by CEM03.03 (histograms).

Figure 5

Reaction cross section for $p+{}^{12}\mathrm{C}$, as calculated by the NASA, Dostrovsky, GEM2, and BP models (solid and broken lines). The black dots are cross sections calculated by MCNP6, and the circles are experimental data [62].

Figure 6

Reaction cross section for ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ as calculated by the NASA, Dostrovsky, GEM2, and BP models (solid and broken lines). The circles are experimental data [63] and the squares are total charge-changing cross section (TCC) measurements [64].

Figure 7

Comparison of experimental measurements of the reaction 480 MeV $p+{}^{\mathrm{nat}}\mathrm{Ag}\to {}^6\mathrm{Li}$ at ${60}^{\circ }$ by Green et al. [72] (green circles), with simulations from the original CEM03.03 (red dotted line), CEM03.03F without the coalescence extension (green dashed line), and CEM03.03F with the coalescence extension (red solid line).

Figure 8

Measured elemental cross sections for ${}^{48}\mathrm{Ca}$ fragmentation on ${}^9\mathrm{Be}$ at 140 MeV/nucleon [75] (open symbols) compared to LAQGSM03.03 predictions (solid lines).

Figure 9

Experimental neutron spectra from 400 MeV/nucleon ${}^{14}\mathrm{N}+{}^{12}\mathrm{C}$ [76] (solid symbols), compared with calculations by the production version of MCNP6 (dashed lines) and by the LAQGSM03.03 event generator used as a stand-alone code (solid lines).

Figure 10

Experimental invariant spectra of tritons from the reaction 400 GeV $p+{}^{181}\mathrm{Ta}$ [77] (solid symbols), compared with results by LAQGSM03.03 [6] used as a stand-alone code (solid lines) and by MCNP6 using the LAQGSM03.03 event generator (dashed lines).

Figure 11

Measured cross sections for light fragments produced in 137 MeV/nucleon ${}^{40}\mathrm{A}+{}^{197}\mathrm{Au}$ reactions [78] (black circles), compared to predictions by LAQGSM03.03 with the extended coalescence model (red stars).

Figure 12

Experimental invariant $p,d,t$, and ${}^3\mathrm{He}$ spectra at 30, 45, 60, 90, and 130 degrees (symbols) from a thin NaF target bombarded with an 800 MeV/nucleon ${}^{20}\mathrm{Ne}$ beam [80] (solid points), compared with results by LAQGSM03.03 using the extended coalescence model (histograms). The calculations were performed for ${}^{20}\mathrm{Ne}+{}^{20}\mathrm{Ne}$.

Figure 13

Experimental invariant $p,d,t$, and ${}^3\mathrm{He}$ spectra at 30, 45, 60, 90, and 130 degrees from a thin Pb target bombarded with an 800 MeV/nucleon ${}^{20}\mathrm{Ne}$ beam [80] (symbols), compared with results from LAQGSM03.03 using the extended coalescence model (histograms).

Figure 14

Comparison of the experimental data for ${}^{6,7,8,9}\mathrm{Li}$ spectra at $65{}^{\circ }$ produced from 1.2 GeV protons incident on ${}^{197}\mathrm{Au}$ [20] (open circles), compared to results calculated by the preliminary LAQGSM03.03F (histograms). The dotted and dashed histograms show the contributions from the preequilibrium emission and the extended coalescence model, respectively.

Figure 15

Comparison of the experimental data for ${}^{6,7,8,9}\mathrm{Li}$ spectra at $65{}^{\circ }$ produced from 1.9 GeV protons incident on ${}^{197}\mathrm{Au}$ [20] (open circles), compared to results calculated by the preliminary LAQGSM03.03F (histograms). The dotted and dashed histograms show the contributions from the preequilibrium emission and the extended coalescence model, respectively.

Figure 16

Comparison of recently measured product spectra at forward laboratory angles $\left(\theta \le 6^{\circ }\right)$ from the fragmentation of 400 MeV/nucleon ${}^{12}\mathrm{C}$ projectiles on a ${}^{197}\mathrm{Au}$ target into H and He isotopes [79] (symbols), compared with results from the previously fixed preliminary LAQGSM03.03F code (solid lines). The model results from the coalescence mechanism alone are shown by dashed lines.

Figure 17

Same as Fig. 16 for production of Li, Be, and B isotopes.

Figure 18

Comparison of experimental data for 1200 MeV $p+{}^{\mathrm{nat}}\mathrm{Ni}\to {}^7\mathrm{Li}$ at $15.6{}^{\circ }$, measured by Budzanowski et al. [21] (solid circles), to results from the original CEM03.03 (dashed line) and to those from the improved CEM03.03F (solid line).

Figure 19

Comparison of experimental data for 317 MeV $n+{}^{209}\mathrm{Bi}\to t$ at ${54}^{\circ }$ measured by Franz et al. [81] (solid circles) to results from the original CEM03.03 (solid lines) and from the improved CEM03.03F (dashed lines).

Figure 20

Experimental data for 300 MeV $\gamma +{}^{\mathrm{nat}}\mathrm{Cu}\to p$ at ${45}^{\circ },{90}^{\circ }$, and ${135}^{\circ }$ from Schumacher et al. [82] (open symbols), compared to results from the unmodified CEM03.03 (solid lines) and to those from CEM03.03F (dashed lines).

Figure 21

Comparison of experimental data for 1500 MeV ${\pi }^{+}+{}^{\mathrm{nat}}\mathrm{Fe}\to n$ at ${30}^{\circ },{90}^{\circ }$, and ${150}^{\circ }$ from Nakamoto et al. [83] (open symbols) to results from the unmodified CEM03.03 (solid lines) and to CEM03.03F (dashed lines).

Figure 22

Comparison of measured mass and charge distributions of the product yields from the reaction 800 MeV $p+{}^{197}\mathrm{Au}$, the mean kinetic energies of these products, and the mass distributions of the cross sections for the production of thirteen elements with atomic numbers $Z$ ranging from 20 to 80 [84] (open symbols), to predicted results from the original CEM03.03 (solid lines) and from CEM03.03F (dashed lines).

Figure 23

Comparison of measured fission cross sections for $n+\text{Bi}$ [85] (open circles) and [86] (solid diamonds) to results from the unmodified CEM03.03 (solid line) and from CEM03.03F (dashed lines).

Figure 24

Comparison of experimental data on 1200 MeV $p+{}^{197}\mathrm{Au}\to {}^6\mathrm{Li}$ at ${20}^{\circ }$, measured by Budzanowski et al. [20] (solid circles), to calculated results by CEM03.03F (red solid line), MCNP6-F with $\mathsf{npreqtyp}=66$ (dashed green line), MCNP6-F with $\mathsf{npreqtyp}=6$ (dash-dash-dotted blue line), and the original MCNP6 with the GENXS extension only (red dotted line).

Figure 25

Comparison of experimental data for 2500 MeV $p+{}^{\mathrm{nat}}\mathrm{Ni}\to t,{}^7\mathrm{Li}$ at ${100}^{\circ }$, measured by Budzanowski et al. [21] (solid circles), to calculated results from CEM03.03F (solid red lines), MCNP6-F with $\mathsf{npreqtyp}$= 66 (dashed blue lines), and the original MCNP6 with the GENXS extension only (dash-dotted green lines).