Modeling of spallation reactions

Spallation reactions - What for?

Context

 

Spallation reactions are nuclear reactions involving a light projectile and an atomic nucleus. The projectile energies range from ~100 MeV to a few GeV. These boundaries are indicative only, they correspond to the upper limit for nuclear structure effects and lower limit for the onset of partonic degrees of freedom, respectively. These reactions occur both in space through cosmic radiations and on Earth in particle accelerators. Examples for space include damages to on-board electronics, doses received by the astronauts, and also a possible explanation for the abundance of some nuclei or what they reveal of the cosmic radiation itself from irradiation of meteorites. In accelerators they are used both to produce exotic nuclei, which will be studied further, and neutrons, which will be used as a probe or for the transmutation of nuclear wastes, and also for medical applications such as hadrontherapy.

These various examples show the importance for a correct modeling of these reactions.

 

The basic spallation reaction process.

Goals

 

The main goal is to develop a model that best simulates spallation reactions and that is based on first principles in order to ensure a solid foundation and robust extensions.

These reactions are modeled in two steps, which are an intranuclear cascade followed by the de-excitation of the nucleus. The model developed at DPhN is INCL, which stands for IntraNuclear Cascade Liège (*). Of course, this model is combined with a de-excitation code so that the full reaction is simulated (the most commonly used is the Abla code from GSI, others codes are SMM or GEMINI++).

After fifteen years of improvements INCL correctly reproduces a large number of experimental data (spectra of emitted particles, characteristics of the residual nuclei) for projectile energies ranging from a few tens of MeV to 2-3 GeV (**). Another strength of INCL is its implementation in different transport codes (Geant4, PHITS, MCNP-X) and its usage to simulate macro-systems where intra-nuclear cascades are relevant.

Since ~2012 developments have moved towards higher energies and handling of additional particles. Hence, activities are (or have) focused on:

  • Translation from fortran77 to C++ in order to facilitate the maintenance and for implementation in Geant4;
  • Extension to higher energies (~15 GeV);
  • Implementation of strangeness (Kaon, Lambda, Sigma);
  • Targeting application to cosmic rays (in collaboration with University of Bern, Switzerland).

(*) The code was born in the 80's at the University of Liège. The code is co-developed in close collaboration since the mid-90's.
(**) An international benchmark of spallation codes performed in 2010 under the aegis of the IAEA demonstrated the reliability of INCL with respect to experimental data and other models.

 

Prospects

 

In order to take advantage of available experimental data (especially for strangeness), new particles could be added as projectiles. Indeed, it is considered adding antiprotons, as well as the electromagnetic probes (gamma, electrons, muons), or even electroweak probe (neutrinos), to the current projectiles (nucleons, pions and light nuclei A < 18).

 

 

Contact: Jean-Christophe DAVID

 

Last update : 12/04 2017 (2229)

Retour en haut