Geant4 Validation Research Articles

Including Calorimeter Test Beams in Geant-val—The Physics Validation Testing Suite of Geant4

The Geant4 simulation toolkit is currently adopted by many particle physics experiments, including those at the Large Hadron Collider and the ones proposed for future lepton and hadron colliders. In the present era of precision tests for the Standard Model and increasingly detailed detectors proposed for the future colliders scenario, Geant4 plays a key role. It is required to remain a reliable and stable toolkit for detector simulations and at the same time undergo major improvements in both physics accuracy and computational performance. Calorimeter beam tests involve various particles at different energy scales and represent ideal benchmarks for the physics modeling and assessment of Monte Carlo tools for radiation–matter simulation. We present the first results of a broad validation campaign on test beam data targeting data deployment and preservation with geant-val, the Geant4 validation and testing suite. We investigate the Geant4 capability to model the calorimeter response, energy fluctuations, and shower shapes using data from the ATLAS hadronic end-cap calorimeter and the CALICE silicon-tungsten calorimeter. The evolution over the recent years of the recommended set of physics processes for high-energy physics applications is outlined and compared to alternative models for hadronic interactions.

GEANT4 validation for X-ray treatment of wooden cultural heritage artefacts

The preservation of cultural heritage is very important. Ionizing radiation is widely used for this purpose and use of gamma irradiation has become common practice in cultural heritage preservation. The number of available electron accelerators is two orders of magnitude greater than for gamma facilities, and many countries do not have gamma facilities.In this work we demonstrate the possibility of using an electron accelerator and X-rays generated from accelerated electrons for radiation treatment of wooden cultural heritage. The GEANT4 toolkit was used for the simulation of the passage of particles through matter. The accuracy of radiation treatment numerical simulation in comparison with experiment was in range of 1.5–11.8%.

Validation of Geant4 for silicon microdosimetry in heavy ion therapy

Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 m or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements.This work compares measurements performed with a silicon microdosimeter in mono-energetic , and ion beams of therapeutic energies, against simulation results calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy, ), the dose mean lineal energy, y D and the RBE10, as estimated by the microdosimetric kinetic model (MKM). Overall Geant4 showed reasonable agreement with experimental measurements. Before the distal edge of the BP, simulation and experiment agreed within ∼10% for y D and ∼2% for RBE10. Downstream of the BP less agreement was observed between simulation and experiment, particularly for the and beams. Simulation results downstream of the BP had lower values of y D and RBE10 compared to the experiment due to a higher contribution from lighter fragments compared to heavier fragments.

Validation of Geant4’s G4NRF module against nuclear resonance fluorescence data from 238U and 27Al

G4NRF (Jordan and Warren, 2007; Vavrek et al., 2018a) is a simulation module for modeling nuclear resonance fluorescence (NRF) interactions in the Geant4 framework (Allison et al., 2016). In this work, we validate G4NRF against both absolute and relative measurements of three NRF interactions near 2.2 MeV in 238U and 27Al using the transmission NRF data from the experiments described in Vavrek et al. (2018b). Agreement between the absolute NRF count rates observed in the data and predicted by extensive Geant4+G4NRF modeling validate the combined Geant4+G4NRF to approximately 15–20% in the 238U NRF transitions and 10% in 27Al, for an average 14% discrepancy across the entire study. The difference between simulation and experiment in relative NRF rates, as expressed as ratios of count rates in various NRF lines, is found at the level of ≲3%, and is statistically identical to zero. Inverting the analysis, approximate values of the absolute level widths and branching ratios for 238U and 27Al are also obtained.

Simulation and optimization of current generation in gallium phosphide nanowire betavoltaic devices

The geometry of a gallium phosphide nanowire (NW) array has been optimized for maximum current generation in a betavoltaic (BV) device. The energy capture efficiency for various device geometries with different radioisotope source compounds was calculated in GEANT4. A validation of GEANT4 for BV device simulation was performed by comparing a model output with the available bulk semiconductor BV performance data, followed by predictions of the performance of NW-based devices. The pitch and the diameter of the NWs were found to have the most significant impact on the β-generated current density, with the optimum diameter-to-pitch ratios ranging from 0.55 to 0.8, depending on the source. The energy capture efficiency improved when low energy beta (β) emitters were used. For devices utilizing 63Ni source compounds, the β-generated current densities approached 0.95 μA cm−2, representing an improvement by a factor as high as 5.8 compared to planar devices. In the case of 3H source compounds, the generated current density was 3.05 μA cm−2, a factor of 15.5 larger than comparable planar devices. However, NW devices utilizing sources with a higher decay energy, such as 147Pm, did not demonstrate any improvements over planar geometries. Using the results for optimum NW geometries, NW-based or other nanostructured devices could be made to surpass the present commercial BV batteries.

Validation of Geant4 10.3 simulation of proton interaction for space radiation effects

Monte Carlo simulation of space radiation effects induced by protons is important for design of space missions. Geant4 is a well established toolkit for Monte Carlo simulation focused on high energy physics applications. In this work, a set of new validation results versus data for Geant4 electromagnetic and hadronic interaction of protons is presented and discussed. Optimal configuration of Geant4 physics for space applications is proposed.

Progress in Geant4 Electromagnetic Physics Modelling and Validation

In this work we report on recent improvements in the electromagnetic (EM) physics models of Geant4 and new validations of EM physics. Improvements have been made in models of the photoelectric effect, Compton scattering, gamma conversion to electron and muon pairs, fluctuations of energy loss, multiple scattering, synchrotron radiation, and high energy positron annihilation. The results of these developments are included in the new Geant4 version 10.1 and in patches to previous versions 9.6 and 10.0 that are planned to be used for production for run-2 at LHC. The Geant4 validation suite for EM physics has been extended and new validation results are shown in this work. In particular, the effect of gamma-nuclear interactions on EM shower shape at LHC energies is discussed.

Geant4 validation of neutron production on thick targets bombarded with 120 GeV protons

Neutron energy spectra and angular distributions are calculated for 120GeV protons on thick graphite, aluminum, copper, and tungsten targets using relevant physics models within the Monte-Carlo simulation package Geant4. The calculations are compared to data from recent experiment. Discrepancies are observed between experimental data and Geant4 models, and suggest that improvements of the intra-(INC) and inter-nuclear cascade processes employed by the models are required.

Challenges of the ATLAS Monte Carlo production during Run 1 and beyond

In this paper we will review the ATLAS Monte Carlo production setup including the different production steps involved in full and fast detector simulation. A report on the Monte Carlo production campaigns during Run 1 and Long Shutdown 1 will be presented, including details on various performance aspects. Important improvements in the work flow and software will be highlighted.Besides standard Monte Carlo production for data analyses at 7 and 8 TeV, the production accommodates various specialised activities. These range from extended Monte Carlo validation, Geant4 validation, pile-up simulation using zero bias data and production for various upgrade studies. The challenges of these activities will be discussed.

Validation of Geant4 and MCNPX-PoliMi simulations of fast neutron detection with the EJ-309 liquid scintillator

In organic liquid scintillators, the energy distribution of neutrons is indirectly measured by characterizing the pulse height distribution of light output produced through nuclear reactions within the detectors. However, the complexity of the light generation on these detectors makes simulating their response difficult with standard Monte Carlo techniques. This paper presents the response of 7.62-cm-long×7.62-cm-diameter and 12.7-cm-long×12.7-cm-diameter EJ-309 liquid scintillators, simulated using the Geant4 and MCNPX-PoliMi Monte Carlo codes. The simulations are restricted to the neutron transport and interaction models. Monoenergetic neutrons as well as fission neutrons emitted by a 252Cf spontaneous fission source are used in these simulations. The energy deposition of neutrons in organic liquid scintillators is dependent upon their collisions with hydrogen and carbon nuclei; therefore simulating neutron collisions on an event-by-event basis is important to generate neutron pulse height distributions. There are no default physics models in Geant4 hence proper selection of physics models is required for accurate simulation. In this paper, we compare Geant4 (ver. 4.9.5) and MCNPX-PoliMi (ver. 2.0) neutron pulse height distributions. The simulations are validated with time-of-flight (TOF) measurements obtained with 12.7-cm-long×12.7-cm-diameter EJ-309 detectors. Results show that both Geant4- and MCNPX-PoliMi-generated distributions are in good agreement with the measured data.

Validation of Geant4 Releases with distributed resources

In this paper we present the strategy and tools used to accomplish physics validation of the GEANT4 simulation toolkit.GEANT4 is a toolkit for the simulation of passage of radiation through matter. It is successfully used by all LHC experiments as well as by medical applications, space physics and industrial applications. A publicly available version of GEANT4 is released once per year and a beta preview release is also made available.The developed testing suite is extended with a job submission system that allows for the generation of high statistics data-sets on distributed resources. The analysis of the data is also integrated and tools to store and visualize the results are provided.

SU‐FF‐I‐12: Validation of Geant4's Predictions On X‐Ray Scatter and Glandular Dose in Pendant‐Geometry Cone‐Beam Breast CT

Purpose: The Geant4 toolkit is a freely available, widely supported base package for the simulation of particles through matter. This study aimed to test Geant4's accuracy by comparing its predictions for glandular dose and x‐ray scatter in pendant‐geometry cone‐beam breast CT against previously published experimental and simulated data. Method and Materials: We performed Monte Carlo simulations using the Geant4 package [Agostinelli et al, Nucl Instrum Meth A 506: 250–303, 2003] to recreate the conditions of three previously published papers on breast CT dose and scatter. Geant4's scatter simulations are compared against experimental data [Kwan et al, Med Phys 32(9): 2967–2975, 2005], while the dose results are compared against Monte Carlo simulations based on other codes [Boone et al, Med Phys 31(2): 226–235, 2004; Thacker et al, Phys Med Biol 49: 5433–5444, 2004]. The compared scatter results include scatter‐to‐primary ratio profiles for breasts of different sizes, glandularity and incident x‐ray spectra. For the dose comparisons, we compared Geant4's monochromatic results with the monochromatic results reported by the two previously published papers. Results: Geant4 matches the reported experimental SPR profiles to an accuracy of 1.6–16.7% (μ=9.2%, σ=5.4%). The sources for observed deviations include inexact re‐creation of the experimental setup and lack of specific information on the x‐ray spectra used in the experiments. The dose results agree with Boone's published results within 0.7–12.3% (μ=5.3%, σ=4.2%) and with Thacker's to within 1.2–22.3% (μ=10.8%, σ=8.8%). Conclusion: The data comparison suggests that Geant4 can be used to predict x‐ray scatter and dose deposition in low energy experiments such as dedicated breast CT. Given the availability, support and flexibility of the Geant4 toolkit, the use of this package for simulation of breast CT studies can be very useful to researchers in the field. Research supported in part by: NIH‐NIBIB Grant RO1‐EB002123 and the Georgia Cancer Coalition.

PSF, LSF and S/P in mammography: GEANT4 validation

The main goal of this study was to validate the predictions of GEANT4, a Monte Carlo code originally developed for high-energy physics, for low-energy (10–40 keV) photon transmission and scattering through matter similar to biological tissue. We compared GEANT4 calculations with existing phantom data relevant for the mammographic imaging technique. This work showed that scattered-to-primary ratio data can be simulated using GEANT4 with a deviation smaller than 5%. At the same time, we encountered a limitation in the small-angle region description by the code, which is important for point- and line-spread function calculations. The comparison with forward angle data showed that the GEANT4 models, known as “G4 Low Energy” and “G4 Penelope”, describe the measurements for X-ray beams typically used in mammography better than 10% for angles above 10 degrees, and that “G4 Low Energy” is preferable to “G4 Penelope”. The results confirm the possible use of GEANT4 for the optimization of applications based on low-energy photon transmission and scattering.

Status of the DESIRE project: Geant4 physics validation studies and first results from Columbus/ISS radiation Simulations

The Dose Estimation by Simulation of the ISS Radiation Environment (DESIRE) project aims to accurately calculate radiation fluxes and doses to astronauts inside the European Columbus module of the International Space Station using Geant4. Since Geant4 has not been previously used for this type of application it needs to be validated. This will be followed by a detailed evaluation of the incident radiation fields on ISS and culminate with the geometry modeling and full-scale flux and dose simulations for Columbus. Geant4 validation studies and comparisons to other tools are presented. These concern the angle and energy distributions of particles leaving irradiated targets and of energy depositions in the targets. Comparisons are made between simulations using different Geant4 physics models, experimental data, and other particle transport programs. Geant4 using the "Binary Cascade" model for inelastic nucleon reactions performs very well in these comparisons, but some issues with other models remain to be resolved if they are to be used for space radiation shielding applications. Results of Geant4 simulations of the transport of some relevant radiation field components through the hull of a simplified model of Columbus are also presented.