MENDL2 and IEAF2001 nuclide production yields databases verification in inter-medium energy range.

This work presents results of computer simulation of two experiments which aim at measuring the threshold activation reaction rates in 12C, 19F, 27Al, 59Co, 63Cu, 65Cu, 64Zn, 93Nb, 115In, 169Tm, 181Ta, 197Au, and thin samples placed inside and outside a 0.8 GeV proton-irradiated 4-cm thick W target and a 92-cm-thick W-Na composite target of 15 cm diameter both. In total, more than 1000 values of activation reaction were determined in both the experiments. The measured reaction rates were compared with the rates simulated by the LAHET code with the use of several nuclear databases for the respective excitation functions, namely, MENDL2 together with MENDL2P for cross sections of protons and neutrons up to 100 MeV, and with the recently developed IEAF-2001 that provides neutron cross sections up to 150 MeV. A comparison of simulation-to-experiment agreement obtained with MENDL2 and IEAF-2001 is presented. The agreement between simulation and experiment has been found general satisfactory for both databases. However, further studies should be done to improve the simulation of production of secondary protons and high-energy neutrons, as well as the high-energy neutron elastic scattering. Our results allow to conclude about the reliability of the transport codes and databases used to simulate the accelerator driven systems (ADS), particularly with Na-cooled W targets. High-energy threshold excitation functions to be used in the activation-based unfolding of neutron spectra inside the ADS can also be inferred from these results.

Theoretical simulation of residual nuclide products in 208,207,206Pb, NATPb and 209Bi (P,X) reactions at intermediate and high energies.

The independent and cumulative measured yields of residual products in thin lead and bismuth targets irradiated with 0.04-2.6 GeV protons are compared with results by the LAHET, CEM03, LAQGSM03, INCL+ABLA, CASCADE and YIELDX codes, in order to evaluate the predictive power of the codes in this energy region. We found that the predictive power of the tested codes is different but is satisfactory for most of the nuclides in the spallation region, though none of the codes agree well with the data in the whole-mass region of product nuclides and all should be improved further. On the whole, the predictive power of all codes for the data in the fission and fragmentation product regions and, especially, at the borders between spallation and fission and between fission and fragmentation regions is much worse than in the spallation region; therefore, development of better evaporation/fission/fragmentation models is of first priority.

CEM2k and LAQGSM codes as event generators for space-radiation-shielding and cosmic-ray-propagation applications.

The CEM2k and LAQGSM codes have been recently developed at Los Alamos National Laboratory to simulate nuclear reactions for a number of applications. We have benchmarked our codes against most available data measured at incident particle energies from 10 MeV to 800 GeV and have compared our results with predictions of other current models used by the nuclear community. Here, we present a brief description of our codes and show some illustrative results that testify that CEM2k and LAQGSM can be used as reliable event generators for space-radiation-shielding, cosmic-ray (CR) propagation, and other astrophysical applications. Finally, we show an example of combining of our calculated cross-sections with experimental data from our LANL T-16 compilation to produce evaluated files. Such evaluated files were successfully used in the model of particle propagation in the Galaxy GALPROP to better constrain the size of the CR halo.

A space radiation transport method development.

Improved spacecraft shield design requires early entry of radiation constraints into the design process to maximize performance and minimize costs. As a result, we have been investigating high-speed computational procedures to allow shield analysis from the preliminary design concepts to the final design. In particular, we will discuss the progress towards a full three-dimensional and computationally efficient deterministic code for which the current HZETRN evaluates the lowest-order asymptotic term. HZETRN is the first deterministic solution to the Boltzmann equation allowing field mapping within the International Space Station (ISS) in tens of minutes using standard finite element method (FEM) geometry common to engineering design practice enabling development of integrated multidisciplinary design optimization methods. A single ray trace in ISS FEM geometry requires 14 ms and severely limits application of Monte Carlo methods to such engineering models. A potential means of improving the Monte Carlo efficiency in coupling to spacecraft geometry is given in terms of re-configurable computing and could be utilized in the final design as verification of the deterministic method optimized design.