After several years of pandemic, we are pleased to announce that the series of the Geant4 Space Users' Workshop –G4SUW- is now resuming. This is our great pleasure that NASA Jet Propulsion Laboratory (JPL), Pasadena, California, is hosting this 15th edition of the G4SUW. A visit of the JPL laboratory is planned for the workshop participants and accompanying persons. The G4SUW is focused on new results on space radiation interaction with components, sensors and shielding analysis, to be confronted with the Geant4-based tools and developments applicable to space missions. The particular topics of interest for this workshop include:
Space radiation and its effects are key design considerations for missions. At JPL, Geant4 is used in a variety of applications including comparisons of total ionizing dose (TID) analyses with other radiation transport codes, estimating an instrument’s response to high energy penetrating radiation, and tracing particle trajectories in magnetic fields. This presentation will give an overview of some Geant4 analyses performed for JPL missions and scientific studies.
This presentation offers an overview of the recent activities and developments within the European Space Agency (ESA) pertaining to Geant4-based tools. ESA has adopted the use of these tools to support a diverse range of applications, such as validating instrument and detector responses, characterizing background noise in scientific instruments, optimizing space radiation shielding, investigating component effects and aiding scientific studies on biological effects and astronaut radiation hazards.
The presentation will focus on ESA's ongoing efforts to develop and enhance several Geant4 tools, specifically GRAS (3D radiation analysis), MULASSIS (1D radiation analysis), PLANETOCOSMICS (cosmic ray showers), and GRAPPA – the GRAS Preprocessor for planetary bodies and asteroids. The discussion will highlight new features and capabilities, including:
• G4 Multi-Threading functionality integrated into GRAS, improving performance and enabling faster simulations.
• ICRP 123 module added in GRAS. This new analysis module, based on fluence to dose conversion coefficients, enhances the precision of simulations of biological effects resulting from space radiation exposure.
• The introduction of Layered Geometry models allows for the study of habitats and human phantoms within the context of Mars and Moon missions, providing valuable insights into radiation protection strategies.
Real applications of these tools will be presented during the session, demonstrating the practical utility of these advancements. ESA's commitment to enhancing Geant4-based tools underlines its pivotal role in advancing space and planetary exploration and in addressing the challenges posed by radiation in these environments. This presentation aims to foster knowledge sharing, inspire further developments, and encourage collaboration within the Geant4 Space Users community.
Through the utilization of the GEANT4 tool integrated into SPENVIS, I aim to demonstrate the practicality and efficacy of simulating radiation hazards within spacecrafts orbiting in Low Earth Orbit (LEO). This research has two primary objectives: first, to assess the accuracy of these simulations by comparing them with historical dose assessments conducted on the International Space Station (ISS); and second, to emphasize the value of advanced simulation tools in exploring radiation hazards beyond the limitations of traditional dose measurements. By benchmarking simulation outcomes against measured dose values, we gain the ability to delve into the specific secondary products generated during radiation interactions. Additionally, this research sheds light on the intricate nature of novel shielding design challenges. The shift in interest from homogeneous dense materials to composite structures poses significant hurdles, since current simulation tools have not yet adapted to provide users with the capability to accurately model these intricate concepts within the simulation environment.
Moreover, while many investigations concentrate on introducing novel materials to enhance space safety, they frequently overlook the consequential influence of pre-existing spacecraft structures, including Micro-Meteoroid and Orbital Debris (MMOD) shielding, metal racks, and hull components. These elements significantly affect radiation interactions, necessitating their inclusion in simulations to provide accurate assessment of shielding efficiency. This further highlights the importance of advancing the capabilities of these simulation tools to encompass a more comprehensive approach to material characterization.
For instance, novel approaches often advocate for the use of polymers to create lighter shielding options. However, the suitability of such materials is highly contingent on the types of radiation that successfully penetrate existing spacecraft structures. In my preliminary investigation, it became apparent that a significant portion of the radiation inside the ISS consists of secondary neutrons and gamma rays. This observation underscores the limitations of polymer-based solutions, as they may necessitate exceptionally thick shielding, and even then, materials like polyethylene exhibit a significant decrease in efficiency with increasing thickness, further compounding the challenge. This scenario exemplifies the critical importance of studying secondary products in radiation shielding assessments, a task made feasible through the application of simulation tools.
The GDML Workbench (https://github.com/KeithSloan/GDML) is an optional workbench available for the open source project FreeCAD (https://www.freecad.org). Geometry created within FreeCAD can be exported as a GDML file (for reading by Geant4); the workbench also can also import GDML files for viewing/editing. All the GDML geometry primitives are supported, plus several useful FreeCAD constructs, such as arrays (rectilinear, polar, along a path or arbitrary points), extruded and revolved 2D sketches. Optical surfaces are also supported. Materials for each volume can be created or chosen from the included list of NIST materials. The status of the workbench and example uses will be presented.
This presentation will be devoted to recent developments of the EM physics in Geant4 as well as those in the fast simulation domain. A focus will be in particular made on the Machine-Learning based techniques used in the fast simulation.
When cosmic rays or energetic solar particles strike the lunar surface, the secondary energetic particles that escape back into space carry information about the surface composition. These “albedo” particles are also a source of additional radiation exposure for astronauts or hardware at or near the lunar surface, which must be understood in order to plan for survivability of space missions there.
Since the 2009 launch of the Lunar Reconnaissance Orbiter (LRO), the science team of its Cosmic Ray Telescope for the Effects of Radiation (CRaTER) sensor has used the Geant4 radiation-transport code to study this process. Using hundreds of processor-years on computer clusters, we have modeled all albedo particle species except neutrinos. We have organized our model results into JSON-formatted files and are making them available to the space science and engineering communities via the Zenodo open archive.
The distributions of albedo particles are calculated for individual energies of ion species from H to Ni arriving isotropically from space. This enables a user to convolve these response functions with any desired incident ion spectra, rather than having to choose from a limited set of spectra hard-coded into the model. We also include with the model some examples of such convolutions, so that users can check their use of the response files.
We will describe the organization of the model files, which allows users to avoid downloading portions not needed for a particular study. To demonstrate usage, we will show the modeled effects of regolith hydrogen on albedo proton and neutron distributions, including the depths probed. We will compare distributions at the surface and at 20 km altitude, to isolate the products of unstable particles that decay on the way up. And we will present the NEWT (Neutron Electron Water Tomography) technique, which can use electrons from neutron decay to probe regolith hydrogenation.
Geant4 is currently being used to assist in the design (geometry and shielding) of the SHARP (Solar HARd X-ray Polarimeter) instrument of the PADRE (solar PolArization and Directivity X-Ray Experiment) mission. SHARP will determine the degree of polarization of solar flare non-thermal X-rays. I will present calculations done so far, including MDP (Minimum Detectable Polarization) and mu100. I will also discuss plots showing detector responses and comparisons with scattering theory.
Neutron radiation—encountered in healthcare, nuclear reactors, and the space environment—is extremely damaging to human health. On the lunar surface, galactic cosmic rays interact with the lunar regolith to produce albedo neutrons, which have energies ranging from sub-eV to tens of MeV, making it of critical importance to shield these albedo neutrons for manned space exploration missions. Using polymer-based materials mixed with hexagonal boron nitride, we consider the physical processes of moderation and absorption to address a basic question: To protect human health, what is the optimal distribution of thermalization and capture elements within a shielding material? Using Geant4, a Monte Carlo code, we simulate over ~20,000 configurations. We find the answer to our original question is nuanced – generally, alternating layers of capture and moderation materials improve radiation protection compared to blended composites but this is not the case for all neutron energies and composite thicknesses. By optimizing the internal structure, we improve the shielding effectiveness up to a factor of 72 relative to aluminum. This is a significant improvement that could dramatically reduce the occupational radiation dose for workers in high-risk environments. Through our new NASA SSERVI program (called CLEVER), we plan to expand our Geant4 capabilities to simulate the charge transport in lunar regolith upon radiation exposure. Our goal is to track the defects, impurities, vacancies, dislocations, and other forms of inhomogeneities on the surfaces and in the crystalline structure of lunar regolith for general particle source.
Cosmic radiation can be divided into GCR (Galactic Cosmic Radiation) originating from outside the solar system, SCR (Solar Cosmic Radiation) originating from the Sun, and trapped particles in the Van Allen belt. Cosmic radiation is a high-energy particle that has a significant impact on satellites and humans operating in space. In particular, when cosmic radiation passes through electronic components, the electronic components absorb the energy of the radiation, causing effects such as TID (Total Ionizing Dose), SEE (Single Event Effect), and DDD (Displacement Dose Damage). This study analyzes the TID impact of COTS (Commercial Off-The-Shelf) OBC (On Board Computer) and MCU (MicroController Unit) such as Arduino (YUN, UNO, PICO, DUE, etc.), Raspberry Pi (CM3, CM4, etc.), LattePanda, and Nucleo among electronic components. Furthermore, to ensure that COTS products can physically reduce absorbed doses, various types of shields were designed and simulated using Gean4 (GEometry ANd Tracking) and MCNP6.2 (Monte Carlo N-Particle). 1-layer shield is composed of one of seven materials (Al, Fe, Cu, Ni, Ti, Pb, W), and compare the change in absorbed dose reduction. The 2-layer shield adds a 4mm Aluminum layer to the front of 1-layer shield, emulating an actual satellite’s outer wall. The 3-layer shield adds a BPE (Borated Polyethylene) to the back of 2-layer shield to reduce neutron flux. Geant4 and MCNP6.2 were used for shield design and simulation, and the results of the two programs were compared. In general, the higher density of the material can shield more efficiently, and it was confirmed that the results of the two programs differed by at least 2% and up to 19%.
Abstract: In recent decades, 2D materials have garnered significant interest for electronic and optical applications, particularly in the aerospace sector. Understanding the potential damage to electronic devices and sensors based on 2D materials is crucial, especially given the critical need for effective yet lightweight radiation shielding to maintain the health of satellite sensors. This study simulates the effects of cosmic radiation on 2D materials, focusing on damage mechanisms like displacements and sputtering. We employ the Geant4 simulation toolkit to analyze the energy spectrum of gamma, proton, and electron radiation passing through shields of various thicknesses, then estimate the consequent damage levels on the 2D material. Following the radiation exposure simulations, we use Density Functional Theory (DFT) calculations to evaluate any changes in the electronic and optical properties of the 2D materials. The goal of this research is to provide a comprehensive understanding of how shield thickness and weight impact the integrity of 2D materials under cosmic radiation exposure. This understanding is vital for guiding the development of more effective and lightweight shielding solutions, a crucial factor for electronic devices in satellites where every gram of weight counts
Keywords: 2D Materials, Cosmic Radiation, Satellite Sensors, Radiation Shielding, Geant4 Simulation, Density Functional Theory, Structural Damage Analysis, Lightweight Shielding Solutions, Aerospace Applications,
Abstract— This paper presents an investigation on the radiative environments that FPGA devices may encounter, elucidating the mechanisms that play a role in particle-matter interactions and their resulting consequences, notably single event upsets (SEUs). SEUs are soft errors triggered by ionizing particles, which impart charges to storage elements within FPGAs, including configuration memory cells and user memory. The primary aim of this work is to calculate SEU cross sections induced by heavy ions and protons across diverse SRAM-based FPGA device families. Additionally, we determine for various orbital missions the upset rate for each FPGA device by using CREM96. Finally, we analyze the influence of sensitive volume depth on SEU rate predictions.
Keywords—Space radiation environment, single event upsets, , cross-section, SRAM-based FPGA.
In space radiation environment, SEU mitigation is crucial to guarantee total reliable operation of memory and FPGA devices. This paper presents the design of a an EDAC system based on the combination of partial TMR and the Quasi-cyclic codes implemented in SRAM-based FPGAs to protect SRAM memories against Single Event Upsets. Experimental results show that the proposed EDAC has smaller delay, area, and power overheads over standard EDAC schemes.
Specific absorbed fractions (SAF) and S-values (S), which are related to internal radiation dosimetry, can currently be estimated using a variety of Monte Carlo tools, including MCNP and GATE, in order to prevent biological damage from being done to tissues and organs after they've been exposed to ionizing radiation. For physicists with coding skills, such tools make physics easier. However, programming and/or simulation inputs continue to be labor-intensive and time-consuming tasks. In this study, we introduce a newly created Geant4-based code called "DoseCalcs" for internal dosimetry calculations. This code offers a variety of geometrical methods (STL, GDML, TEXT, STL, C++, voxelized, DICOM, and tetrahedral) that can be used to build the simulation geometry, as well as computational capabilities such as running with MPI or multi-threading mode.
The SAFs for eight discrete mono-energetic photons with energies ranging from 0.01 to 2 MeV were estimated using the voxelized ICRP adult female phantom, determined using DoseCalcs, and compared to OpenDose reference data. The accuracy of DoseCalcs is shown to be in good agreement with OpenDose, which shows its suitability for application in the estimation of internal dosimetry quantities using a voxelized geometry method.
While we have parallelized the simulation to a number of sub-simulations with different source configurations on each compute unit, the maximum number of events (G4int size) in a simulation still limits the execution of all source configurations in one execution.
A multiscale approach was developed for the first time and used to assess the early DNA radiation damage due to galactic cosmic ray (GCR) protons and the resulting backscattered lunar radiation (BLR) on the surface of the Moon using Geant4. Male and female astronauts were modelled using the ICRP145 tetrahedral mesh phantoms. GCR protons were modelled incident on the Moon surface with an isotropic angular distribution and BLR modelled using a novel biasing technique. A hybrid physics list was developed which combined Geant4 electromagnetic condensed history physics models with Geant4-DNA track structure models to be able to model the interactions of the GCR at sub-cellular level, covering an energy range from few eV up to 100 GeV. Hadronic interactions and the modelling of induced radiochemical species were also included. The early DNA damage was assessed using the Geant4-DNA molecularDNA example. It was observed that BLR contributed to around 20% of single strand breaks and up to 45% of double strand breaks. Indirect damage due to induced hydroxyl radicals constituted most of the damage. As such, the backscattered radiation component must be considered for a full understanding of the biological impact of space radiation. In addition, more DNA damage was observed in the pancreas, spleen and ovaries in comparison to other organs modelled such as the brain, breast tissues and spinal spongiosa.
TOPAS wraps and extends the Geant4 Simulation Toolkit to create a tool that is at once highly flexible and easy to use. Originally created for medical physics under 12 years of funding from the National Cancer Institute, TOPAS is now available to all users completely free of charge under the most permissive style open-source license. While TOPAS has the full Geant4 at its core, it wraps Geant4 in its own unique architecture that allows users to master the tool in days and continue to apply it, from one project to another, over years of evolving research activity. TOPAS currently has over 2600 users at 646 institutions in 68 countries, each user running TOPAS in their own way for their own project. TOPAS is fully multi-threaded, requires no programming experience, and is available as a pre-built executable for all common macOS and Linux systems. While most users apply TOPAS to radiation therapy, medical imaging and radiobiology, it has also been applied in areas as diverse as archeology and materials science. We will take a look at unique aspects of the TOPAS architecture, including its entirely innovative control system, geometry model, scoring system, and its "time feature" system that makes TOPAS not just 3D, but 4D, wherein almost any parameter can vary over time. We will show examples of how TOPAS has been applied in medicine and discuss how it can also easily apply to aerospace simulations. TOPAS is further described at https://www.topasmc.org/
Ultra-thin electromagnetic calorimeters exploiting electromagnetic processes in oriented crystals [1, 2] is a smart solution for gamma-ray space telescopes opening wide prospects for gamma-ray astronomy, in particular for the search of dark matter annihilation. Namely, these calorimeters allow to considerably reduce both the dimension and weight of gamma-ray space telescopes as well as to make available for direct observation ultra-high energy gamma-rays up to TeV scale. Moreover, due to orientational dependence of electromagnetic shower development in oriented crystals one can amplify the signal in a certain direction at the angular scale of ~mrad, i.e. the angular size of interesting astrophysical objects for the dark matter search, such as dwarf galaxies . Furthermore, this orientational dependence can be potentially used for the measurement of the angle of incoming gamma-ray significantly reducing the complexity of the detector.
A large area (~10 m2) and small thickness cosmic detector would provide extraordinary sensitivity to point-like gamma-ray sources. Additionally, such kind of instrument will fit well the geometry of Starlink v2 Mini satellites simplifying the launch to the law orbit.
This application requires reliable Geant4 simulation model of electromagnetic showers in oriented crystals. We present a new simulation model of electromagnetic processes in oriented crystals  implemented into Geant4-11.2.0.beta. We validate the model with the experimental data as well as discuss our first steps towards full-simulation of the gamma-ray space detector.
 L. Bandiera et al. Phys. Rev. Lett. 121, 021603 (2018).
 L. Bandiera et al. Frontiers in Physics 11 (2023) 10.3389/fphy.2023.1254020
 A. Geringer-Sameth, S.M. Koushiappas et al. arXiv:1807.08740v1.
 A. Sytov et al. Journal of Korean Physical Society 83, 132–139 (2023).
We acknowledge support of the INFN through the CSN 5 MC-INFN and OREO projects. A. Sytov is supported by the European Commission (TRILLION, GA. 101032975). This work is also supported by the Korean National Supercomputing Center with supercomputing resources including technical support (KSC-2022-CHA-0003).
In the space environment, semiconductors can be exposed to various radiation sources depending on mission conditions. Depending on the type, energy, and speed of radiation, different damage mechanisms occur. These can be broadly categorized into Total Ionizing Dose (TID) effects due to radiation accumulation and Single Event Effects (SEE) caused by the penetration of radiation particles. We conducted modeling and simulation of the damage caused by TID effects and SEE on (Complementary Metal Oxide Semiconductor) CMOS, which are critical components of electronic systems.
Using semiconductor characteristic simulation tools commonly employed in the electronics field, we performed simulations that combined radiation-induced internal property changes and physical analysis resulting from ion tracking.
In this study, we utilized this Modeling and Simulation (M&S) technology to derive semiconductor processes and transistor layout structures that are radiation-resistant. We validated their properties through chip fabrication. The results of this study can serve as a means for assessing the reliability of semiconductors for radiation environments in the future and will make a significant contribution to enhancing the radiation tolerance of electronic systems.
In the space environment, changes in factors such as blood circulation under microgravity conditions can potentially result in modifications to the pharmacokinetic aspects of drug utilization, impacting drug absorption, distribution, metabolism, and excretion within the body. Nevertheless, assessing these alterations in a terrestrial setting can be challenging. Thus, there is a need for discussion regarding the use of mathematical models to predict and comprehend these changes. The objective of this study is to create gastrointestinal pharmacokinetic models in order to formulate a new agent for assessing related pharmacodynamics. This is done to control diseases, alleviate patient symptoms, and expedite disease resolution.
In this study, both compartment-based pharmacokinetic models (specifically a two-compartment model) and physiologically based pharmacokinetic models (restricted to gastrointestinal fluid rates) were employed to characterize the gastrointestinal pharmacokinetics of new agents and to simulate profiles for evaluating their effects at the target site. This mathematical model was established in both animal and human models and proved to be beneficial in nonclinical and clinical phases of drug development. The absorption kinetics (ka, absorption rate constant) of therapeutic drugs in the gastrointestinal tract were considered as the elimination kinetics (kel, elimination rate constant) in these models. The kel value was determined or estimated through in vivo animal pharmacokinetic studies, in vitro cell systems, or in-silico methods. The permeabilities of model compounds, ranging from 0.12 to 15.6 cm/sec, were obtained using the Caco2 cell system, which was used to estimate the ka values. The gastrointestinal fluid rates in animals and humans, as previously reported, were applied in this study. The Michaelis-Menten kinetic model or an indirect model was employed in the proposed pharmacokinetic model, depending on the characteristics of the therapeutic agent.
In conclusion, this study established a combined mathematical model incorporating compartment-based and physiologically based pharmacokinetic elements. This model can be a valuable tool for evaluating the behavior of therapeutic agents and understanding the pharmacodynamics of new drugs in a space environment.
This study investigates the effect of mixing ratios on the compatibility and binding energy of polyvinylpyrrolidone (PVP) and polyacrylic acid (PAA) in polymer composites for radiation treatment using molecular dynamics (MD) and Monte Carlo (MC) simulations. Five simulation models were constructed by varying the composition ratio of PVP and PAA (1/9, 3/7, 5/5, 7/3, 9/1), and the solubility parameter (δ) and cohesive energy density (CED) were calculated by performing MD simulations. The MC simulation was used to evaluate radiation absorption distributions based on the intermolecular binding energy. The results showed that PVP exhibited good compatibility with PAA from the perspective of δ and CED, and the binding energy analysis revealed that the thermal properties of the system changed as the radiation dose increased. The study provides valuable insights into the effect of mixing ratios on the properties of polymer composites for radiation treatment.
The tumor microenvironment (TME) consisting of blood and lymphatic vessels, fibroblasts, immune cells, and extracellular matrix (ECM) is a critical factor determining prognosis of anti-cancer drug treatment. Most of all, vasculature and ECM structures are the most influential factors in TME. The abnormal, tortuous and leaky tumor vasculature structure reduces chemical drug delivery to target tumor. Moreover, the high-density collagen fibers surrounding the tumor tissues make chemical drugs less effective and inhibit the infiltration of immune cells into the tumor. Therefore, mimicking the vasculature and ECM structures surrounding tumor in vitro is crucial to predict anti-cancer drug efficacy.
Therefore, a detailed and systematic understanding of the vasculature and ECM in the tumor microenvironment is essential for establishing tumor treatment strategies. Although in vivo studies are valuable in deepening our understanding of the interactions between cancer cells and the tumor microenvironment, they have limitations in dissecting the detailed mechanisms of cell-cell interactions. Additionally, results from animal models are difficult to apply to humans due to species differences. Tumor-on-a-chip offers an alternative method to study multicellular interactions in the tumor microenvironment in vitro. Previous studies on tumor-on-a-chip have been developed to incorporate endothelial cells into tumor spheroids to mimic the tumor microenvironmental vasculature and to induce tumor-associated angiogenesis or to create vascular networks with cancer cells. However, they did not consider ECM remodeling even though it is one of the most important factors in the tumor microenvironment.
In this study, we construct a breast cancer microenvironment on a microfluidic 3D cell culture platform using cancer spheroids, fibroblasts, and endothelial cells. To investigate correlating effect of tumor aggressiveness, TME formation and anti-cancer drug efficacy, three different breast cell lines were selected according to surface receptor expression. Their vasculature and ECM structures were compared with each other and the anti-cancer efficacy of paclitaxel (PTX) and NK cell infusion was evaluated using our microfluidic platform. In addition, effect of TME targeting drugs on vasculature and ECM was investigated. The results show more aggressive tumor constructs more inhibitive TME in anti-cancer treatment and that can be recovered by vasculature and ECM targeting drug treatment.
Electron transport is dominated by angular deflections below 10 MeV, with large deviations from the continuous slowing down approximation, csda, and straight-ahead methods used for higher energies and for heavier atomic ions.
EMPC will present comparisons between adjoint Monte Carlo benchmarks and
ray-trace approximations for spherical, cylindrical, and rectangular geometries, using tabulated attenuation tables, TATs, generated by 1d adjoint Monte Carlo and by SHIELDOSE versions 1 and 2 (NOVICE*seltzer). The ray-trace results include both slant-path and minimum-path modeling for solids and shells/enclosures respectively.
Spectra used in the comparison, generated by NOVICE*sofip (Stassinopoulos):
ISS: International Space Station, solar minimum and maximum
VAP: Van Allen Probe, solar minimum and maximum
GEO: geosynchronous, solar minimum and maximum
Enhanced electrons, aei7hi/lo, at ISS
Jovian: Clipper project data
The spectra include trapped protons and solar flare protons.
Comparisons include particle type to further delineate the unique character of electron transport in space radiation effects analysis, as documented during and after the NASA Voyager mission by the author.