S. Roesler

The Monte Carlo Event Generator DPMJET-III

A new version of the Monte Carlo event generator Dpmjet is presented. It is a code system based on the Dual Parton Model and unifies all features of the Dtunuc-2, Dpmjet-II and Phojet1.12 event generators. Dpmjet-III allows the sim- ulation of hadron-hadron, hadron-nucleus, nucleus-nucleus, photon-hadron, photon- photon and photon-nucleus interactions from a few GeV up to the highest cosmic ray energies. Hadronic collisions at high energies involve the production of particles with low transverse momenta, the so-called soft multiparticle production. The theoretical tools available at present are not sufficient to understand this feature from QCD and phenomenological models are typically applied instead. The Dual Parton Model (DPM) (1) is such a model and its fundamental ideas are presently the basis of many of the Monte Carlo (MC) implementations of soft interactions in codes used for Radiation Physics simulations. Many of these implementations are however limited in their application by, for example, the collision energy range which they are able to describe or by the collision partners (hadrons, nuclei, photons) which the model can be used for. With respect to modern multi-purpose codes for particle interaction and transport these limitations at high energy are clearly often a disadvantage. In this paper we present the Dpmjet-III code system, a MC event generator based on the DPM which is unique in its wide range of application. Dpmjet-III is capable of simulating hadron-hadron, hadron-nucleus, nucleus-nucleus, photon- hadron, photon-photon and photon-nucleus interactions from a few GeV up to the highest cosmic ray energies. In the present paper we give an overview over the different components and models of Dpmjet-III and present a few examples for comparisons of model results with experimental data.

Antiprotons at Solar Maximum

New measurements with good statistics will make it possible to observe the time variation of cosmic antiprotons at 1 AU through the approaching peak of solar activity. We report a new computation of the interstellar antiproton spectrum expected from collisions between cosmic protons and the interstellar gas. This spectrum is then used as input to a steady-state drift model of solar modulation, in order to provide predictions for the antiproton spectrum as well as the antiproton/proton ratio at 1 AU. Our model predicts a surprisingly large, rapid increase in the antiproton/proton ratio through the next solar maximum, followed by a large excursion in the ratio during the following decade.

Antiparticle to particle production ratios in hadron-hadron and d-Au collisions in the DPMJET-III Monte Carlo model

To understand baryon stopping we analyze new Relativistic Heavy Ion Collider and Fermilab data within the framework of the multichain Monte Carlo DPMJET-III. The present consideration is restricted to hadron-hadron and d-Au collisions, where the present version of the model can be trusted.

Nuclear Models in FLUKA: Present Capabilities, Open Problems, and Future Improvements

The nuclear reaction models embedded in the FLUKA code cover hadron, ion, photon and neutrino induced nuclear interactions from energies as low as few tens of MeV up to several tens of TeV. A short description of the main physics ingredients in the FLUKA nuclear models is given, with emphasis on the intermediate energy range and on “exotic” reactions. The treatment of electromagnetic dissociation as recently implemented in FLUKA is described. Examples of performances are presented for illustrative situations covering some of the most typical FLUKA applications.

The FLUKA code: an overview

FLUKA is a multipurpose Monte Carlo code which can transport a variety of particles over a wide energy range in complex geometries. The code is a joint project of INFN and CERN: part of its development is also supported by the University of Houston and NASA. FLUKA is successfully applied in several fields, including but not only, particle physics, cosmic ray physics, dosimetry, radioprotection, hadron therapy, space radiation, accelerator design and neutronics. The code is the standard tool used at CERN for dosimetry, radioprotection and beam-machine interaction studies. Here we give a glimpse into the code physics models with a particular emphasis to the hadronic and nuclear sector.

Induced radioactivity in and around high-energy particle accelerators

Particle accelerators and their surroundings are locations of residual radioactivity production that is induced by the interaction of high-energy particles with matter. This paper gives an overview of the principles of activation caused at proton accelerators, which are the main machines operated at Conseil Européen pour la Recherche Nucléaire. It describes the parameters defining radio-nuclide production caused by beam losses. The second part of the paper concentrates on the analytic calculation of activation and the Monte Carlo approach as it is implemented in the FLUKA code. Techniques used to obtain, on the one hand, estimates of radioactivity in Becquerel and, on the other hand, residual dose rates caused by the activated material are discussed. The last part of the paper focuses on experiments that allow for benchmarking FLUKA activation calculations and on simulations used to predict activation in and around high-energy proton machines. In that respect, the paper addresses the residual dose rate that will be induced by proton-proton collisions at an energy of two times 7 TeV in and around the Compact Muon Solenoid (CMS) detector. Besides activation of solid materials, the air activation expected in the CMS cavern caused by this beam operation is also discussed.

The hadronic models for cosmic ray physics: the FLUKA code solutions

FLUKA is a general purpose Monte Carlo transport and interaction code used for fundamental physics and for a wide range of applications. These include Cosmic Ray Physics (muons, neutrinos, EAS, underground physics), both for basic research and applied studies in space and atmospheric flight dosimetry and radiation damage. A review of the hadronic models available in FLUKA and relevant for the description of cosmic ray air showers is presented in this paper. Recent updates concerning these models are discussed. The FLUKA capabilities in the simulation of the formation and propagation of EM and hadronic showers in the Earth’s atmosphere are shown.

Neutron Energy and Time-of-flight Spectra Behind the Lateral Shield of a High Energy Electron Accelerator Beam Dump,Part I: Measurements

Neutron energy and time-of-flight spectra were measured behind the lateral shield of the electron beam dump at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were produced by a 28.7 GeV electron beam hitting the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shield. The measurements were performed using a NE213 organic liquid scintillator behind different thicknesses of the concrete shield of 274 cm, 335 cm, and 396 cm, respectively. The neutron energy spectra between 6 and 800 MeV were obtained by unfolding the measured pulse height spectrum with the detector response function. The attenuation length of neutrons in concrete was then derived. The spectra of neutron time-of-flight between beam on dump and neutron detection by NE213 were also measured. The corresponding experimental results were simulated with the FLUKA Monte Carlo code. The experimental results show good agreement with the simulated results.

Neutron energy and time-of-flight spectra behind the lateral shield of a high energy electron accelerator beam dump. Part II: Monte Carlo simulations

Energy spectra of high-energy neutrons and neutron time-of-flight spectra were calculated for the setup of experiment T-454 performed with a NE213 liquid scintillator at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were created by the interaction a 28.7 GeV electron beam in the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shielding. In order to determine the attenuation length of high-energy neutrons additional concrete shielding of various thicknesses was placed outside the existing shielding. The calculations were performed using the FLUKA interaction and transport code. The energy and time-of-flight were recorded for the location of the detector allowing a detailed comparison with the experimental data. A generally good description of the data is achieved adding confidence to the use of FLUKA for the design of shielding for high-energy electron accelerators.

Generic Studies of Radioactivity Induced by High-Energy Beams in Different Absorber Materials

Abstract The FLUKA code is used to simulate the residual dose rates around a typical beam absorber considering various scenarios. The latter include carbon, copper, and tungsten as jaw materials, different beam energies, protons, and lead ion beams as well as different irradiation and cooling times. Using the dose rate maximum close to the absorber surface, the study investigates the cooling time dependence for the different scenarios. It is found to be similar for all jaw materials and beam energies. The dose rate scales with energy as E0.83 and with the number of nucleons when comparing proton beam with lead ions. After a sufficiently long cooling time, a few radionuclides produced in the steel tank, such as 56Co, 58Co, 48V, and 54Mn, dominate the dose rate. The study can be easily extended to other materials or irradiation scenarios and can be applied to first evaluations of given accelerator design options.