The FLUKA Code: Developments and Challenges for High Energy and Medical Applications

TL;DR: The FLUKA Monte Carlo code as discussed by the authors is used extensively at CERN for all beam-machine interactions, radioprotection calculations and facility design of forthcoming projects, which requires the code to be consistently reliable over the entire energy range (from MeV to TeV) for all projectiles.

About: This article is published in Nuclear Data Sheets.The article was published on 2014-06-01 and is currently open access. It has received 1511 citations till now.

Summary

INTRODUCTION

• The CERN accelerator complex exploits a unique combination of accelerators.
• The equivalent laboratory energy range for proton beams at CERN spans from a few MeV up to 10 5 TeV.
• FLUKA is jointly developed by the European Laboratory for Particle Physics (CERN), and the Italian National Institute for Nuclear Physics (INFN).
• Hadron-nucleon inelastic collisions are described in terms of resonance production and decay up to a few GeV.
• Data (symbols, from the compilation in [12] ) are presented for the total cross section and for the "single π" cross section (red).

III. DEVELOPMENTS OF INTEREST FOR HADRONTHERAPY MONITORING

• They can proceed through emission of either independent nucleons or deuterons.
• All possible combinations of unbound nucleons and/or light fragments are checked at each stage of system evolution and a figure-of-merit evaluation based on phase space closeness at the nucleus periphery is used to decide whether a light fragment is formed.
• At energies below a few tens of MeV, coalescence is increasingly ineffective in reproducing the data.
• An example outlining the effectiveness of the new approach and directly relevant for proton therapy monitoring with PET is given in Fig. 4(left) .
• FLUKA capabilities in this aspect have been recently enhanced [17] , and an example is given in Fig. 5 .

IV. SPIN AND PARITY EFFECTS

• Statistical evaporation of excited low mass fragments is unsuitable due to the relatively few, widely spaced levels.
• Therefore, alternative de-excitation mechanisms are employed for these light (typically A≤16) residual nuclei in most Monte Carlo (MC) codes.
• The spin factor S n must be restricted to the spin projections compatible with an emission with L min .
• This reaction is of special relevance for underground experiments, particularly those using liquid scintillators, where photons produced by high energy muons penetrating through the underground rock can produce 11 C and neutron background.

V. CONCLUSIONS

• The FLUKA code is used for a variety of applications at CERN and elsewhere.
• Some of the recent improvements of relevance for CERN problems, mostly ν beams and interactions, underground experiments, and medical applications have been described, together with examples showing the improved results when compared with experimental data.

Figures

FIG. 4. nat,12C(p, x)11C (left), and nat,12C(γ, n)11C (right) cross sections as computed with fluka2013.0 (red, upper curve), and fluka2011.2 (blue, lower curve) compared with data retrieved from the EXFOR library [16] .

FIG. 5. Prompt photon yield at 90◦ as a function of depth for a 95 MeV/n 12C beam impinging on a PMMA target. The Bragg peak position is at ≈20 mm. Absolute comparison of data (red stars) [18] (the original experimental data have been re-evaluated in 2012) and FLUKA (blue circles).

FIG. 1. Left: Double differential π+ production for 158 GeV/c protons on carbon as a function OF pT for various XF values (legend: XF values and scaling factor among curves). Right: pT integrated π + (green, top) π− (blue, second from top) production for the same reaction and K+ (red, second from bottom), K− (purple, bottom) production for pp at the same energy. Histograms computed by FLUKA ; symbols experimental data from [9, 10]. The dashed areas represent the statistical errors of the calculation.

FIG. 3. Cross sections for reactions induced by muon neutrinos on protons (left) and neutrons (right). Data (symbols, from the compilation in [12]) are presented for the total cross section (black) and for the “single π” cross section (red). The total simulated cross section (black line) is composed of the QE (not shown), resonant (magenta line) and DIS (cyan line) channels. The red dotted line shows the calculated “single π” cross section in the present FLUKA version, while the dotted blue line corresponds to the old FLUKA results.

FIG. 2. Pion production (π− from Be left, π+ from Cu right) from proton interactions at 12.3 GeV/c. Double differential pion spectra as a function of momentum for different cos θ intervals in the range 0.5-1 (legend: < cos θ > and scaling factor among curves). Symbols: data (BNL910 expt. [13]), histograms: FLUKA . The dashed areas represent the statistical errors of the calculation.

Frequently asked questions

Q1. What are the contributions in "The fluka code: developments and challenges for high energy and medical applications" ?

The FLUKA code has been used for a variety of applications at CERN and elsewhere this paper, and some of the recent improvements of relevance for CERN problems, mostly ν beams and interactions, underground experiments, and medical applications have been described. 

Q2. Why is the evaporation of low mass fragments unsuitable?

SPIN AND PARITY EFFECTSStatistical evaporation of excited low mass fragments is unsuitable due to the relatively few, widely spaced levels. 

Q3. What are the important reactions for in-vivo or off-line PET monitoring?

Composite ejectiles like d, t, 3He, and α can be reasonably described by coalescence algorithms during the intranuclear cascade and preequilibrium stages. 

Q4. What is the important method for in-vivo or off-line PET monitoring?

A popular choice forthese calculations is the Fermi Break-up model [19, 20], where the excited nucleus is supposed to disassemble in one single step into two or more fragments, possibly in excited states, with branching given by plain phase space considerations. 

Q5. What is the important reaction for in-vivo or off-line PET monitoring?

All possible combinations of unbound nucleons and/or light fragments are checked at each stage of system evolution and a figure-of-merit evaluation based on phase space closeness at the nucleus periphery is used to decide whether a light fragment is formed. 

Q6. What is the important technique for in-vivo hadrontherapy monitoring?

Another promising technique for in-vivo hadrontherapy monitoring relies on the detection of prompt photons emitted following nuclear interactions by the beam particles.