NASA has recognized the need for making additional heavy-ion collision measurements at the U.S. Brookhaven National Laboratory in order to support further improvement of several particle physics transport-code models for space exploration applications. FLUKA has been identified as one of these codes and we will review the nature and status of this investigation as it relates to high-energy heavy-ion physics

Anderson, V.

Ballarini, F.

Battistoni, G.

Campanella, M.

Carboni, M.

Cerutti, F.

Elkhayari, N.

Empl, A.

Fasso, A.

Ferrari, A.

Gadoli, E.

Gazelli, M. V.

LeBourgeois, M.

Lee, K. T.

Mayes, B.

Muraro, S.

Ottolenghi, A.

Pelliccioni, M.

Pinsky, L. S.

Rancati, T.

Ranft, J.

Roesler, S.

Sala, P. R.

Scannocchio, D.

Smirnov, G.

NASA Technical Reports Server

Acta Phys. Hung. A 19/1 (2004) 000–000
HEAVY ION
PHYSICS
Space Applications of the FLUKA Monte-Carlo Code:
Lunar and Planetary Exploration
Kerry Lee,1 Thomas Wilson,1,a Neal Zapp,1 and Lawrence Pinsky,2
for the FLUKA collaborationb
1 NASA, Johnson Space Center,
2101 NASA Parkway, Code KR, Houston, Texas 77058 USA
2 University of Houston
4800 Calhoun Blvd, Houston, Texas, 77204 USA
Received 15 November 2005
Abstract. NASA has recognized the need for making additional heavy-ion
collision measurements at the U.S. Brookhaven National Laboratory in order to
support further improvement of several particle physics transport-code models
for space exploration applications. FLUKA has been identified as one of these
codes and we will review the nature and status of this investigation as it relates
to high-energy heavy-ion physics.
Keywords: Heavy-ion collisions, cosmic rays, particle albedos
PACS: 21.60.Ka, 24.10.Lx
1. Introduction
The particle radiation environments on planetary surfaces contain a full spectrum of
particle types, including relativistic nuclei produced in heavy-ion collisions created
by incident high-energy cosmic rays. Unlike the Earth which is protected by an
atmosphere, the surface of the Moon is an example of a planetary surface directly
bombarded by energetic nuclei from both the Sun and the Galaxy.
As a consequence, the lunar environment is a complex one involving the full
range of heavy-ion physics from thermal neutrons to interactions predicted by the
relativistic Dual Parton Model (DPM). Backscatter albedos of all types are gener-
ated, including prompt neutrino production due to charmed meson decay. Defining
these radiation environments is a circumstance very similar to that existing at par-
ticle accelerators such as the forth-coming Large Hadron Collider (LHC) at CERN
and similar colliders at Fermilab. Monte Carlos are the simulation tools used in
that definition, and FLUKA [1–3] is the one of choice in this discussion.
1219-7580/04/ $ 20.00
c© 2004 Akade´miai Kiado´, Budapest
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2 K. Lee and T. Wilson
It has become a goal of experiments such as NASA-funded studies at the U.S.
Brookhaven National Laboratory to make as many exclusive cross-section measure-
ments as possible and feasible in the energy range 0.1 - 5.0 GeV/A. These can
enhance the Monte Carlo modelling of nuclear physics in the transition region from
nonrelativistic to relativistic effects.
2. Technical Background on FLUKA
As a fully-integrated particle physics Monte Carlo simulation package, FLUKA has
been successfully corroborated with well-established experimental physics (called
benchmarking), and is known to preserve correlations within interactions as well
as among particle shower components, from thermal neutrons to TeV energies. Its
simulation represents the interaction and propagation through matter of some 60
different types of particles with high accuracy. This includes photons and electrons
from 1 keV to thousands of TeV, charm production of neutrinos, muons of any en-
ergy, hadrons of energies up to 20 TeV (extended to 10 PeV by linking FLUKA with
the DPMJET code discussed below), as well as all of the corresponding antiparticles
and heavy ions.
3. Modifications of FLUKA in Progress
Since ion-ion (A-A) nuclear interactions are not yet thoroughly treated in any Monte
Carlo for all energies, FLUKA is still under development. This circumstance arises
because of the paucity of exclusive A-A collision data at the onset of relativistic
effects. Stated differently, the Monte Carlo community is in need of a satisfactory
event generator that adequately simulates collisional nuclear physics (A-A scatter-
ing) in the energy range 0.5-to-5.0 GeV/A.
Above this energy range (0.5-to-5.0 GeV/A), the Dual Parton Model (DPM-
JET) is used [4, 5]. Below that range, FLUKA employs the Intra-Nuclear Cascade
(INC) and Pre-Equilibrium Approach to Nuclear Thermalization (PEANUT) mod-
els for light ions.
3.1. The FLUKA-DPMJET Interface
The event generator DPMJET mentioned above is based on the Dual Parton Model
in conjunction with the Glauber formalism. It is a Monte Carlo code for sampling
hadron-hadron, hadron-nucleus, and nucleus-nucleus (A-A) collisions at accelerator
and cosmic-ray energies (Elab from 5-10 GeV/A up to 10
18
− 1020 eV/A), adapted
and interfaced with the rest of FLUKA [4]. It has since been upgraded to DPMJET-
3 [5].
FLUKA internally requires A-A production cross-sections in order to select
the appropriate nucleus-nucleus interactions. It includes a complete matrix of A-A
production cross-sections along with the Glauber impact parameter distributions.
Heavy-ion Enhancements in FLUKA 3
Owing to the validity of the Glauber formalism, these cross-sections can be safely
utilized down to a projectile kinetic energy of about 1 GeV/A.
3.2. Transition to Non-relativistic Energies
Although event generators exist for most of the particle interactions treated by
FLUKA, those necessary for A-A collisions in the transition region from the Glauber
formalism down to non-relativistic energies (from say 5 GeV/A down to 100 MeV/A)
are not as well-defined. This is the region of the NASA-funded transport code in-
vestigation.
One feature of the physics in this region is momentum-dependent nuclear poten-
tials which are notoriously nonlocal in nature. Nonlocal interactions break Lorentz
invariance and this is somehow related to the transition to nonrelativistic dynamics
(where Lorentz invariance becomes negligible). A number of computer codes have
been created to deal with the nuclear and molecular dynamics in this energy range,
but with only marginal success. The first was the nonrelativistic Quantum Molec-
ular Dynamics (QMD) model [6], augmented by limited Poincare´ invariance argu-
ments to be pseudo-relativistic, a model known as the Relativistic QMD (RQMD)
method [7].
The RQMD 2.4 model has been widely used over the energy range from 0.1
GeV/A to several hundreds of GeV/A. However, this code does not perform the
latest stages of the A-A reaction, and does not always conserve energy.
Several alternatives exist, addressed in more detail elsewhere [8]. First, the
RQMD code per se has been scrutinized, adapted to be interfaced with the FLUKA
evaporation models and corrected for energy non-conservation, while maintaining
its underlying philosophy. Then it has been embedded into the current version
of FLUKA while again guaranteeing absolute conservation of energy, an essential
requirement for any suitable transport code. Second, alternative QMD [3] and
Hamiltonian Molecular Dynamics (HMD) event generators are undergoing develop-
ment.
3.3. The Modified RQMD Event Generator
The modified RQMD event generator included in the present release as RQMD-
FLUKA has been used to prepare fluence plots that aided in planning for the
proposed measurements at Brookhaven National Laboratory for NASA. These are
of interest, and two will be shown here while more are discussed in a different
publication [8]. They illustrate FLUKA’s existing capability in the suspect energy
range below DPMJET’s cutoff around 5 GeV/A and above the INC-technique and
PEANUT.
The embedded RQMD-FLUKA provides an option to run in an INC-like mode
to reduce computation time in instances where full accuracy is not required. The
original RQMD code does not identify complex fragments at the end of the in-
teraction. The strategy adopted is to allow the code to follow an interaction to
4 K. Lee and T. Wilson
some intermediate point where all of the hard collisions between constituent par-
ticles are over. Then the evolution is stopped in an interim state. At that point,
projectile- and target-like nuclei are formed out of the spectator nucleons (i.e. nu-
cleons which did not undergo two-body collisions), and their excitation energy is
calculated from the energies of the holes left by the hit nucleons. The remaining
particles are next placed in the final-state RQMD-FLUKA event-generator output
buffer. The two trial hot-fragments so identified are next run through the FLUKA
evaporation/fission/fragmentation module, allowing them to de-excite into surviv-
ing fragments since the latter may have boiled-off some of their original constituents
in the evaporation process.
Fig. 1. Laboratory scattering angle distributions for protons, pions and light
ions (D-B) per second in one-degree annular bins from a 1 kHz 3.0 GeV/A
Gold (Au) beam incident on a Silicon (Si) target.
Figures 1-2 show some results from the RQMD-FLUKA event generator as it
presently exists. These fluence plots (ordinate: number of particles cm−2) depict
the laboratory scattering angles in annular angle-bins of one degree for protons
above a kinetic energy of 100 MeV in the laboratory, for all charged pions above
50 MeV in the laboratory and for all light ions (Deuterons through Boron) above
100 MeV/A. The ordinates are normalized to the yields from a 1-kHz beam of Gold
(Au) incident upon a one-interaction-length thick Silicon (Si) target.
Both of the figures show a similar behavior, having a proton distribution peaking
near zero. One of the important differences in the calculations for 5 GeV/A with
respect to 3 GeV/A interactions is the relative height of the pion distribution at
larger angles. The pion scattering-angle distribution rises from low values at small
Heavy-ion Enhancements in FLUKA 5
angles, becoming comparable to the proton fluence. In Figure 2 it begins to exceed
the proton fluence around 13 degrees.
Fig. 2. Same fluence as Figure 1, except using a 1 kHz 5.0 GeV/A Gold (Au)
beam incident on a Silicon (Si) target. Note the dominance of the pions starting
at about 13 degrees.
3.4. The HMD Event Generator
The additional option under study to complement the RQMD-FLUKA event gener-
ator is the HMD model. This event generator derives from the concept of primary
and secondary constraints developed by Dirac [9] for relativistic Hamiltonians and
derived from Poincare´ invariance. When the Hamiltionian exists, this approach to
relativistic QMD-type methods has never been implemented successfully in a Monte
Carlo and it offers promise in the problematic transition energy range. Its poten-
tial application within FLUKA is under consideration as yet another alternative to
QMD-FLUKA. More detail on this method is published elsewhere [8].
4. Conclusions
Prompted by the need for adequate Monte Carlo simulation tools both for future
particle accelerators and space exploration architectures, FLUKA is undergoing
continuing development. The need for better understanding of heavy-ion physics in
the transition from nonrelativistic to relativistic energies has been reviewed.
6 K. Lee and T. Wilson
Acknowledgments
FLUKA development as discussed here has been partially funded by financial sup-
port from INFN as well as NASA under Grant NAG8-1901.
Notes
a. Permanent address: NASA, Johnson Space Center - KR, Houston, Texas 77058;
E-mail: twilson@ems.jsc.nasa.gov
b. V. Andersen1, F. Ballarini2,3 , G. Battistoni3,4, M. Campanella3,4, M. Carboni5, F.
Cerutti3,4, N. Elkhayari1, A. Empl1, A. Fasso`6, A. Ferrari7, E. Gadioli3,4 , M. V.
Garzelli3,4 , M. LeBourgeois1 , K. T. Lee1,8, B. Mayes1, S. Muraro3, A. Ottolenghi2,3,
M. Pelliccioni5, L. S. Pinsky1, T. Rancati3, J. Ranft9, S . Roesler7, P. R. Sala3,4, D.
Scannocchio2,3, G. Smirnov10, V. Vlachoudis7, T. Wilson8, and N. Zapp1,8
1 University of Houston, Houston, TX, USA
2 University of Pavia, Milan, Italy
3 Istituto Nazionale di Fisica Nucleare (INFN), Milan, Italy
4 University of Milan, Milan, Italy
5 Laboratori Nazionali di Frascati, INFN, Milan, Italy
6 Stanford Linear Acclerator Center (SLAC), Stanford, CA, USA
7 European Organization for Nuclear Research (CERN), Geneve, Switzerland
8 NASA Johnson Space Center, Houston, TX, USA
9 Siegen University, Siegen, Germany
10 Joint Institute for Nuclear Research (JINR), Dubna, Russia
References
1. A. Fasso`, A. Ferrari and P. Sala, Proceedings of Monte Carlo 2000 Conf.,
Lisbon, October 23-26, 2000, A. Kling, F. Barao, M. Nakagawa, L. Tavora,
P.Vaz, eds., Springer-Verlag, Berlin (2001) p. 159.
2. A. Fasso`, A. Ferrari, J. Ranft and P. Sala, ibid., p. 955.
3. V. Andersen et al., Adv. Spa. Res. 34, Issue 6 (2004) 1302.
4. J. Ranft, Phys. Rev. D51 (1995) 64.
5. S. Roesler, R. Engel and J. Ranft, Proceedings of Monte Carlo 2000 Conf.,
Lisbon, October 23-26, 2000, Springer-Verlag, Berlin (2001) p. 1033.
6. J. Aichelin, Prog. Part. Nucl. Phys. 30 (1993) 191.
7. H. Sorge, H. Sto¨cker and W. Greiner, Ann. Phys. 192 (1989) 266.
8. L. S. Pinsky et al., IEEE Aerospace Conf., Big Sky, Montana, to be published
(2005).
9. P. A. M. Dirac, Rev. Mod. Phys. 21 (1949) 392.


Space Applications of the FLUKA Monte-Carlo Code: Lunar and Planetary Exploration

Space Applications of the FLUKA Monte-Carlo Code: Lunar and Planetary Exploration

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