Emilio Mendoza, Francesc Sansaloni, Pedro Arce, Daniel Cano-Ott, Juan Ignacio Lagares

�Abstract– An accurate modeling of the interactions of chargedparticles (protons, 2H, 3H, 3He, �-particles…) with energies up totenths of MeV is necessary for many physical problems andapplications such as proton therapy or isotope production formedical imaging (e.g. 11C and 18F), activation calculations,accelerator shielding ormaterial damage calculations.Most of the Monte Carlo simulation codes, and in particular theGeant4 simulation package, applied to these types of problems dorely on theoretical nuclear models rather than evaluated crosssection data. It is well known that the validity of nuclear modelsused in Monte Carlo codes for describing the interaction ofcharged particles in the energy range up to tenths of MeV can bepoor and lead to unacceptably large systematic uncertainties ifthe model parameters are not adjusted by comparison toexperimental data. For this reason, we have developed theG4ParticleHP package for Geant4. The package allowssimulating the interaction of charged particles interactions usingevaluated nuclear data libraries for charged particles such asENDF-B.VII or TENDL.

I. INTRODUCTION

N the simulation of many physical problems it is needed toknow precisely the nuclear interactions of protons, as well as

other charged particles, like deuterium, tritium, 3He andalphas. This means to know not only the cross sections, butalso the production of secondary particles like gammas,neutrons and the residual nuclei. Nuclear models do notpredict accurately these reaction channels for energies up totenths of MeV if the model parameters are not adjusted bycomparison to experimental data. In the case of Geant4, wehave explicitly verified the incorrectness of the cross sectionscalculated by the QGSP model. Fig.1. shows the largedisagreement between the Geant4 [1,2] (blue curve) andexperimental 18O (p,n)18F and 14N(p,�)11C reaction crosssections (green curve).

Manuscript received November 14, 2011. This work was supported in partby the Spanish national company for radioactive waste ENRESA, through theCIEMAT-ENRESA agreements on “Transmutación de residuos radiactivosde alta actividad ", the Spanish “Plan Nacional de I+D+i de Física dePartículas (project FPA2008-04972-C03-01)”, the Spanish Ministerio deCiencia e Innovación through the “CONSOLIDER CSD 2007-00042” projectand the European Commission 7th Framework Project ENSAR.

E. M. is with Department of Nuclear Innovation, CIEMAT, Madrid, Spain(e-mail: emilio.mendoza@ciemat.es).

F. S. is with Department of Medical Applications, CIEMAT, Madrid,Spain (e-mail: francesc.sansaloni@ciemat.es).

P. A. is with Department of Medical Applications, CIEMAT, Madrid,Spain (e-mail: pedro.arce@ciemat.es).

D. C-O. is with Department of Nuclear Innovation, CIEMAT, Madrid,Spain (e-mail: daniel.cano@ciemat.es).

J. I. L. is with Department of Medical Applications, CIEMAT, Madrid,Spain (e-mail: juanignacio.lagares@ciemat.es).

To solve this problem we have taken a different approach:in a similar way as it is done in the Geant4 G4NeutronHPpackage, we have converted the existing nuclear data librariesfor inelastic interactions induced by charged particles into theGeant4 G4NDL format and developed the necessary sourcecode for modeling the reactions based on the nuclear datalibraries. The code is currently being validated by comparisonto other Monte Carlo codes using the same input libraries.

II. MATERIALS AND METHODS

A homemade program has been used to translate theexisting charged particle nuclear data libraries to the sameGeant4 format used for the G4NeutronHP package. Inaddition, a new package inspired on the G4NeutronHP modelhas been written simulating the interaction of charged particlesbased on nuclear data libraries rather than nuclear models.

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CROSS SECTION 18O(p,n)18F

Geant4IAEA

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CROSS SECTION 14N(p,alpha)11C

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Fig.1. Comparison of proton incident cross sections of production of18O from 18F (left) and 11C from 14N (right) calculated with Geant4(in blue) and obtained from the IAEA experimental data base (ingreen).

Available data bases

There are a few evaluated nuclear data bases that contain datafor charged particle nuclear interactions. The characteristics ofthe databases used are the following:

Anew physics model for the charged particletransport with Geant4

I

2011 IEEE Nuclear Science Symposium Conference Record N53-5

978-1-4673-0120-6/11/$26.00 ©2011 IEEE 2242

ENDF-B.VII.0 [6] / JENDL-3.3 [7]:� Relies only on experimental data.� Only a few isotopes are available. In the ENDF-B.VII.0

library, 46 isotopes for incident protons, 5 for incidentdeuterons, 3 for incident tritons and 2 for incident 3Henuclei. In the JENDL-3.3 library there are 13 isotopesfor incident alphas.

� Only p � X reactions are included (double differentialspectra of resulting particles (n,p,d,…), without channelinformation (n,nn,np,nna,...)).

� The energy range covered extends up to 150 MeV forprotons (with some exceptions), 50 MeV for deuterons(with some exceptions), 20 MeV for tritons, 20 MeV for3He and 15 MeV for alphas.

� The files are distributed in the ENDF format.

TENDL [8]:� Relies on some experimental data and calculations with

the TALYS code [9].� Contains information for 2400 isotopes.� There are several versions.� Has information for all reaction channels. For some

versions, only p � X reactions are included.� The energy range covered extends up to 200 MeV for all

particle types.� The files are distributed in the ENDF format

IAEA medical database [10]:� Relies only on experimental data.� Only a few reaction channels for a few isotopes are

available.� Only channel cross sections are available.� The data are both in simple text and ENDF format.

IBANDL database [11]:� Relies only on experimental data.� Not all isotopes are listed in.� Many experimental measurements channel by channel.� The energy range covered extends up to a few MeV.� The files are distributed in the R33 format.

III. VALIDATION

We have planned extensive tests to validate the conversion ofthe files to the Geant4 format and the performance of the newGeant4 G4ParticleHP model. Furthermore, the complete list ofisotopes present in the libraries will be tested with pythonscripts using the GAMOS [3] framework.

A general description of the tests to be made and a fewexamples of the validation started already are given next.

A. Check of the total and channel by channel crosssections: ENDF format� Geant4 formatThis simple test compares the total cross section and the

cross section for each inelastic channel. It runs a Geant4 job ofprotons of a fixed energy, deactivating the electromagnetic and

hadronic elastic processes and killing the proton after the firstinteraction; it counts the times each reaction channel happensand compares it with the cross section read directly from theENDF format file.

Fig.2. Comparison of 27Al(p,na)23Mg inelastic cross sectionfrom Geant4 (blue) and the TENDL database (red).

B. Check of the secondary particle production: energyspectra

It runs a Geant4 job similar to the previous test and plots theenergy spectra of secondary particles. Then compares thespectra with the spectra read directly from the ENDF file.

Fig. 3. Comparison of neutron energy spectra produced by 7MeV protons interacting on a 18O target from ENDF database(blue) and Geant4 (red). Both data are normalized to the samearbitrary value.

C. Check of the secondary particle production: emissionangle spectraSimilar to the neutron spectra, it tests the angle between the

primary proton and the secondary particle, isotope per isotope,channel by channel, for different proton energies.

Neutron energy (eV)

number

ofneutro

ns

proton Energy (MeV)

XS(ba

rn)

2243

D. Comparison with MCNPIn a last test we compare a full simulation in Geant4 with

the same simulation in MCNP [4]. For MCNP we use theMCUNED [5] development that allows to read severalevaluated data bases in MCNP.

Fig. 4. Neutron fluence emitted by a 0.1 mm thick layer of 206Pb,irradiated with a 100 MeV proton beam. The neutron yields obtainedwith Geant4 and MCNPX with the ENDF-VII.0, LA150 (distributedwith MCNPX) and TENDL libraries are compared.

Fig. 4. and Fig. 5. show the neutron and �-ray fluenciesemitted by a 0.1 mm thick layer of 206Pb, irradiated with a 100MeV proton beam. From the comparison of the neutron yieldsin Fig. 4., it can be observed that the results with the two codesare in agreement and that the result depends largely on theevaluated library used. The results obtained in Fig. 5. for the �-ray distributions do show a much larger scatter. The reason isthat Geant4 does have built in models that are used incombination with the evaluated libraries. However, it can beseen that the results for Geant4 and MNCPX obtained with theevaluated libraries (ENDF/B-V.II and LA150, respectively) doagree at energies above a few hundred keV.

The comparison of Geant4 with the new package andMCNP using the evaluated data library represents a firstvalidation our code implementation, while the comparison ofGeant4 with and without the new package shows theimprovements that the new package provides.

IV. CONCLUSIONS:We have developed a new package for Geant4 that

simulates the nuclear interactions of protons, deuterons,tritons, 3He and alpha particles from nuclear data libraries. Thenew package is at the test phase but shows a remarkableimprovement with respect to the previous models existing inGeant4 for several cases. Nevertheless, due to the compleximplementation of this package, it will be necessary to perform

a very careful and extensive set of tests to verify the chargedparticle cross sections as well as the secondary particleproduction. It is also to be noted that the goodness of thepackage is strictly correlated with the goodness of the datalibraries, which sometimes are not based on experimental data,but on models that need a detailed validation.

Fig. 5. �-ray fluence emitted by a 0.1 mm thick layer of 206Pb,irradiated with a 100 MeV proton beam. The Geant4 and MCNPX �-ray yields obtained for evaluated libraries and models are compared.

REFERENCES

[1] S. Agostinelli et al., ”Geant4: a simulation toolkit”, Nucl. Instr. Meth,vol. A506, pp. 250-303, July 2003.

[2] J. Allison et al., “Geant4 developments and applications'”, IEEE Trans.Nucl. Sci., vol. 53, No 1, pp. 270-278, February 2006.

[3] P. Arce, J.I. Lagares, L. Harkness, L. Desorgher, G. de Lorenzo, Y.Abreu, Z. Want. “GAMOS: an easy and flexible way to use GEANT4”.See this proceedings.

[4] D.B. Pelowitz (ed.) (2008). MCNPX Users Manual Version 2.6.0.Report LA-CP-07-1473 (2008). [Online]. Available:https://mcnpx.lanl.gov/documents.html

[5] P. Sauvan, J. Sanz, F. Ogando. “New capabilities for Monte Carlosimulation of deuteron transport and secondary products generation”.Nucl. Instr. Meth., vol A 614, pp. 323=330, March 2010

[6] M. B. Chadwick et al., "ENDF/B-VII.0 Next Generation EvaluatedNuclear Data Library for Nuclear Science and Technology" , SpecialIssue on Evaluated Nuclear Data File ENDF/B-VII.0, Nuclear DataSheets 107(12) (2006) 2931-3059.

[7] K. Shibata et al., "Japanese Evaluated Nuclear Data Library Version 3Revision-3: JENDL-3.3", J. Nucl. Sci. Technol. 39(2002)1125.

[8] A.J. Koning and D. Rochman, "TENDL-2008: Consistent TALYS-baseEvaluated Nuclear Data Library including covariance data",www.talys.eu/tendl-2008 , OECD/NEA JEFF/DOC-1262, November2008.

[9] A.J. Koning, S. Hilaire and M.C. Duijvestijn, ``TALYS-1.0",Proceedings of the International Conference on Nuclear Data forScience and Technology - ND2007, April 22 -27, 2007, Nice, France,eds. O. Bersillon, F. Gunsing, E. Bauge, R. Jacqmin and S. Leray, EDPSciences, 2008, p. 211-214.

[10] IAEA-TECDOC-1211 (May 2001).[11] http://www-nds.iaea.org/ibandl/

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