Geant4 Simulation Research Articles

Simulation of angular resolution of a new electromagnetic sampling calorimeter

We report on the simulation results for the angular resolution of an electromagnetic (EM) sampling calorimeter with photons in the range of 100 MeV to 2 GeV. The simulation model of the EM calorimeter consists of alternating layers of a 1-mm-thick lead plate and a 5-mm-thick plastic scintillator plate. The scintillator plates are alternately segmented into horizontal and vertical strips. In this study, we obtain energy deposits in individual strips using Geant4 simulations and reconstruct the incident photon angles using the XGBoost with gradient-boosted decision trees. The performance of the angle reconstruction depends on the detector configuration and the accuracy of machine learning. The angular resolution is well described by the expression 0.24°⊕1.25°/Eγ, where Eγ is the incident photon energy in GeV, for 32 layers of 15 mm width strips. This energy dependence is consistent for different incident angles in the range of 10° to 40°.

Measurement of the Compton scattering in germanium with a p-type point-contact germanium detector for dark matter detection

Low-energy background through Compton scattering from the ambient γ rays can be contaminated in direct dark matter search experiments. In this paper, we report comparable measurements on low-energy spectra via Compton scattering from several γ-ray sources with a p-type point-contact germanium detector. The spectra between 500 eV and 18 keV have been measured and analyzed. Moreover, the features of the electron binding effect, particularly at the edges of the K- and L-shells in the germanium atom, were observed with different gamma sources and were consistent with the models in the Geant4 simulation. An empirical background model is proposed that provides insights into understanding the low-energy background in germanium for direct dark matter experiments.

GEANT4 simulation and spectrum restoration of a pixelated X-ray detector

We perform a detailed simulation of a pixelated CdTe detector using the GEANT4 toolkit completed with a custom code emulating the detector's electronic response. We demonstrate that a measured tungsten X-ray spectrum can be majorly restored back to the original incident spectrum using the developed model, without requiring the dedicated hardware charge sharing correction.

Atmospheric Neutron-Induced Fault Generation and Propagation in Quantum Bits and Quantum Circuits

Quantum Computing, by exploiting the quantum properties of quantum bits, significantly improves the performance and efficiency of computation. Unfortunately, quantum devices are very susceptible to external perturbation, including natural radiation. In this paper we measure, through GEANT4 simulations, the charge deposited by impinging neutrons in superconducting quantum devices. As we show, most atmospheric neutrons deposit sufficient energy to break Cooper pairs and, thus, can potentially modify the qubit state. Then, with a dedicated circuit-level fault-injector, we track the transient fault propagation in real quantum circuits and measure its impact on the output probabilities distribution. We discuss the fault model for quantum bits and show how to measure faults impact on the circuit output.

Study on Radiation Shielding of Inner Radiation Belt Protons

The radiation environment in the inner radiation belt is severe due to the large flux of high energy protons. Very few satellites are deployed in inner radiation belt today, and radiation shielding in this region did not get much attention. An imaging satellite developed by the Chinese Academy of Sciences will operate in the inner radiation belt in 2023. In order to shield the high energy protons, a new composite material was developed, and the shielding ability of this material was compared with that of Al, Ta, and sandwich materials by the Geant4 simulation tool. The results show that the new material can reduce the total ionizing dose by 40%, and the displacement damage dose by 50% compared with the Al shielding in same shielding mass. The number of transmitted protons under the shielding of Al and new materials was tested by using a 30 MeV~60 MeV proton beam on the ground, and the experimental results agree well with the simulation results.

Angular distribution of low momentum atmospheric muons at ground level

We report measurements of the angular distributions of low momentum atmospheric muons at 38 m above sea level for zenith angles θ between -60 and 60 degrees in the south-north direction. The muon detection was performed with two NaI(Tl) scintillation detectors mounted in coincidence. An adjustable lead thickness placed between the detectors allowed to select muons with a minimal momentum ranging from 0.3 to 0.9 GeV/c. The integrated and the differential muon flux were determined by analyzing the deposited energy spectra in the scintillators backed up by a Geant4 simulation of the experimental setup. The results are consistent with the cos n (θ) distribution in good agreement with the literature. These data contribute to fill the gap in the geomagnetic cutoff rigidity interval 8 GV < Pc < 14 GV where no similar measurements were performed before. We found that n = 1.88 - 0.12 Pμ c in this domain of muon momenta cutoff Pμ c < 1 GeV/c. The present measurements are useful for many muon studies requiring an accurate integrated flux.

Technical note: Simulation of lung counting applications using Geant4

A Geant4 simulation package has been developed to investigate and test detector configurations for lung counting applications. The objective of this study was to measure radiation emitted from the human body and to make a qualitative comparison of the results of the simulation with an experiment. Experimental data were measured from a plastic phantom with a set of lungs containing 241Am activity. For comparison, simulations in which 241Am activity was uniformly distributed inside the lungs of the ICRP adult reference computational phantom were made. The attenuation of photons by the chest wall was simulated and from this photopeak efficiency and photon transmission were calculated as a function of photon energy. The transmission of 59.5 keV gamma rays, characteristic of the decay of 241Am, was determined from the computational phantom as a function of the angular position of the detector. It was found that the simulated detector response corresponds well with that from an experiment. The simulated count rate below 100 keV was 10.0(7) % greater compared to the experimental measurement. It was observed that 58.3(4) % of photons are attenuated for energies below 100 keV by the chest wall. In the simulation, the transmission of 59.5 keV gamma rays varied from 13.8(2) % to 38.0(4) % as a function of the angular position of the detector. The results obtained from the simulations show a satisfactory agreement with experimental data and the package can be used in the development of future body counting applications and enables optimization of the detection geometry.

Experimental study of medical isotopes 62,64Cu and 68Ga production using intense picosecond laser pulse

Radioisotopes are indispensable agents in medical diagnosis and treatment, among which copper-62, 64 (62,64Cu) and gallium-68 (68Ga) are medical isotopes widely used in positron emission tomography (PET) imaging. Experiments that generate these radioisotopes via laser-induced photonuclear reactions were performed on the XingGuangIII laser facility of the Laser Fusion Research Center in Mianyang. High-charge ( ∼ 40 nC) MeV electron (e− ) beams were generated with 100 terawatts, picosecond laser pulses. The e− beams were then impinged on a metal stack composed of Ta foil and activation plates (natural Cu and Ga2O3), producing high-energy bremsstrahlung x-rays and medical isotopes 62,64Cu and 68Ga, respectively. The characteristic emissions of the produced 62,64Cu and 68Ga were detected off-line , and the production yields of 62,64Cu and 68Ga were obtained to be of the order of 106 per laser shot. For electrons with energy higher than 8 MeV, the dependence of isotope production efficiency (per e− ) on electron temperature () is investigated through Geant4 simulations. It is found that the production efficiency increases with the . At ∼ 10 MeV, the values are 10−4 for 62Cu and 2 × 10 − 5 for 68Ga, respectively. The prospect of producing the medical isotopes 62,64Cu and 68Ga are further evaluated using a table-top femtosecond laser system of high repetition. With a repetition rate of 100 Hz, their activity is expected to reach 0.2 GBq for 62Cu, 0.1 GBq for 64Cu and 0.05 GBq for 68Ga, respectively. Such activity would meet the required dose for clinical PET imaging, indicating the great potential to produce medical isotopes with an all-optical, high-repetition laser system.

A detailed investigation of gamma and neutron shielding capabilities of ternary composites doped with polyacrylonitrile and gadolinium (III) sulfate

The shielding efficiencies of gamma and neutron radiations for ternary composites containing polyester resin, polyacrylonitrile and gadolinium (III) sulfate at different ratios were investigated in the present study. In order to investigate the gamma radiation shielding capacity of the produced ternary composites, linear and mass attenuation coefficients, half value layer, effective atomic number and radiation protection efficiency parameters were determined experimentally, theoretically and using the GEANT4 simulation code. The gamma shielding capabilities of the composites were studied in the photon energy range of 59.5–1332.5 keV. In order to investigate the neutron shielding abilities of composites, inelastic, elastic, capture and transport numbers, total macroscopic cross section and mean free path parameters were determined with the help of GEANT4 simulation code. In addition, the number of transmitted neutrons at different sample thicknesses and neutron energies were also determined. It was observed that gamma radiation shielding properties were improved due to the increasing amount of gadolinium (III) sulfate and neutron shielding properties were improved due to the increasing amount of polyacrylonitrile. While the composite coded P0Gd50 exhibits a better gamma radiation shielding ability than the others, the neutron shielding of the sample coded P50Gd0 is also more favorable than the others.

ESTIMATION OF THE GAMMA-RAY FIELD IN AIR FROM RADIOACTIVE SOURCES IN THE GROUND BY NUMERICAL SOLUTION OF THE BOLTZMANN TRANSPORT EQUATION.

Gamma-ray field in air from radioactive sources uniformly distributed in the ground is calculated by numerically solving the photon transport equation. The scattered flux is developed on the Legendre polynomials basis of the spherical harmonics method and a double P1 approximation is applied. The method is implemented in the Octave programming package. The calculation of the gamma-ray field is also done by Monte Carlo simulation using an optimised geometry model of the soil-air medium that is implemented in Geant4 simulation code. The results obtained by the two methods are in good agreement. The computing time for the spherical harmonics deterministic method is significantly less than the Monte Carlo simulation. Dose rate conversion factors in the air are calculated for the natural radioactive series of 238U and 232Th and for 40K nuclide and for soils contaminated by various radionuclides. The results are in agreement with the published theoretical and experimental studies.

Determination of 170,172Yb(α,n)173,175Hf reaction cross sections in a stacked-target experiment

Background: For understanding the synthesis of elements in the universe, precise knowledge of reaction rates and cross sections is paramount. This is especially true for the $p$ process because its study requires large network calculations including thousands of nuclei and nuclear reactions with little room for simplification. Therefore, robust theoretical methods for predicting cross sections are needed which are usually based on Hauser-Feshbach calculations. These calculations use physics input in the form of $\ensuremath{\gamma}$-ray strength functions, nuclear level densities, and particle $+$ nucleus optical-model potentials. These have to be constrained using experimental results.Purpose: To constrain the $\ensuremath{\alpha}$ optical-model potential $\ensuremath{\alpha}$-induced reactions are well suited. The ytterbium isotopic chain not only offers multiple stable isotopes on which cross sections can be measured and insights into the evolution of the $\ensuremath{\alpha}$ optical-model potential with the neutron-to-proton ratio can be gained but also includes the $p$ nucleus $^{168}\mathrm{Yb}$. Its abundance is significantly impacted by the $^{164,166}\mathrm{Yb}(\ensuremath{\alpha},\ensuremath{\gamma})$ reactions and is, therefore, also affected by the constraints resulting from the experiment presented in this paper.Method: To study the $^{170,172}\mathrm{Yb}(\ensuremath{\alpha},n)^{173,175}\mathrm{Hf}$ reaction cross sections the activation method was used. During irradiation the targets were arranged in stacks of four to reduce the required irradiation time. Aluminum degrader foils served as backings. The average interaction energy inside each ytterbium layer was determined via geant4 simulations. A third layer, consisting of manganese, was used to verify the simulations by comparing the measured $^{55}\mathrm{Mn}(\ensuremath{\alpha},(2)n)^{57,58}\mathrm{Co}$ reaction cross sections to previous results. For irradiation the 10 MV FN tandem accelerator located at the University of Cologne was used and the activation measurement was performed utilizing the Cologne Clover Counting setup consisting of two clover-type high-purity germanium detectors in a face-to-face geometry.Results: For the $^{170}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction seven cross sections at center-of-mass energies between 12.7 and 16.5 MeV were measured. For the $^{172}\mathrm{Yb}(\ensuremath{\alpha},n)$ reaction six cross sections for center-of-mass energies of 13.1 to 16.5 MeV could be determined with an additional upper limit at ${E}_{\mathrm{c}.\mathrm{m}.}=12.3$ MeV.Conclusion: Comparisons to theoretical models show that state-of-the-art $\ensuremath{\alpha}$-optical model potentials reproduce the measured cross sections very well. The ratios of $(\ensuremath{\alpha},n)$ reaction cross sections in the ytterbium isotopic chain can be accurately reproduced as well.

RAMSEES: A Model of the Atmospheric Radiative Environment Based on Geant4 Simulation of Extensive Air Shower

The device downscaling of electronic components has given rise to the need to consider specific failures in onboard airplane electronics. Single Event Effects (SEE) are a kind of failures that occur due to radiation in the atmosphere. For the purpose of ensuring onboard electronic reliability, there is a clear need for new tools to predict the SEE rate, at both avionic altitudes and at ground level. In this work, we develop a new tool: RAMSEES (Radiation Atmospheric Model for SEE Simulation), which simulates the atmospheric radiative environment induced by cosmic rays. This multiscale and multi-physics phenomenon is simulated using the Geant4 toolkit, allowing the creation of a database to characterize the radiation environment in the atmosphere as a function of altitude. We show the need to simulate very high-energy particles such as 100 TeV space protons, because they are the main contributor of radiation at avionic altitudes as well as at ground level. Our approach shows a good agreement with the experimental data, the standards, and other models, and it also points out some discrepancies, especially below 18 km of altitude. RAMSEES can be the basis of the estimation of the SEE rate from ground level to the stratosphere, at any given position and time.

PEPI Lab: a flexible compact multi-modal setup for X-ray phase-contrast and spectral imaging

This paper presents a new flexible compact multi-modal imaging setup referred to as PEPI (Photon-counting Edge-illumination Phase-contrast imaging) Lab, which is based on the edge-illumination (EI) technique and a chromatic detector. The system enables both X-ray phase-contrast (XPCI) and spectral (XSI) imaging of samples on the centimeter scale. This work conceptually follows all the stages in its realization, from the design to the first imaging results. The setup can be operated in four different modes, i.e. photon-counting/conventional, spectral, double-mask EI, and single-mask EI, whereby the switch to any modality is fast, software controlled, and does not require any hardware modification or lengthy re-alignment procedures. The system specifications, ranging from the X-ray tube features to the mask material and aspect ratio, have been quantitatively studied and optimized through a dedicated Geant4 simulation platform, guiding the choice of the instrumentation. The realization of the imaging setup, both in terms of hardware and control software, is detailed and discussed with a focus on practical/experimental aspects. Flexibility and compactness (66 cm source-to-detector distance in EI) are ensured by dedicated motion stages, whereas spectral capabilities are enabled by the Pixirad-1/Pixie-III detector in combination with a tungsten anode X-ray source operating in the range 40–100 kVp. The stability of the system, when operated in EI, has been verified, and drifts leading to mask misalignment of less than 1 upmum have been measured over a period of 54 h. The first imaging results, one for each modality, demonstrate that the system fulfills its design requirements. Specifically, XSI tomographic images of an iodine-based phantom demonstrate the system’s quantitativeness and sensibility to concentrations in the order of a few mg/ml. Planar XPCI images of a carpenter bee specimen, both in single and double-mask modes, demonstrate that refraction sensitivity (below 0.6 upmurad in double-mask mode) is comparable with other XPCI systems based on microfocus sources. Phase CT capabilities have also been tested on a dedicated plastic phantom, where the phase channel yielded a 15-fold higher signal-to-noise ratio with respect to attenuation.

Cosmic ray test of a STCF DTOF detector prototype

A time-of-flight detector based on detection of internally reflected Cherenkov light (DTOF), is proposed for the endcap particle identification at the Super Tau-Charm Facility (STCF). A prototype with a trapezoidal fused silica radiator that had a size of 533 mm/ 295 mm × 454 mm × 15 mm is constructed, which is approximately one-third of the size of the DTOF sector proposed for STCF. A field-programmable-gate-array-based dual-threshold time-over-threshold measurement circuit is employed to read signals from the microchannel-plate photomultiplier tube, which performs functions such as signal amplification, discrimination, and digitization. The DTOF prototype was tested in a cosmic ray telescope, which realizes 3D tracking of cosmic ray muons with an angular resolution of < 1 mrad, position resolution of <200μm, and reference time resolution of 24 ps. To analyze and understand the performance of the DTOF prototype, a GEANT4 simulation is employed. The time resolution of the DTOF prototype is 25 ps by using 10 or more photoelectrons in the cosmic ray test, which is in good agreement with the simulation result, proving the feasibility of this technology.

Identification of coal and gangue based on R value method for dual-energy X-ray of Geant4 simulation

With technical means of Geant4 simulation, the effectiveness of R value method in coal and gangue identification method of dual-energy X-ray is verified, and the characteristic factors affecting R value are explored. In the experiment, control variable method is used to study the effect of the thickness and shape of coal and gangue in R threshold. Compared with the shape of the coal sample, the thickness of the sample can directly affect the changes in R value of coal and gangue more. In addition, R threshold is continuously changing during the process of coal and gangue separation. R value of coal and gangue is positively correlated with the thickness of the sample, while the correlation with shape is difficult to be expressed due to the difficulty of mathematical descriptions of shape. The results show that the combination of dual-energy X-ray and image processing of Geant4 simulation can effectively identify coal and gangue, and the accuracy of distinguishing coal and gangue with different shapes and thicknesses reaches 95%. Finally, the current use of Geant4 simulation based on sample thickness can establish R threshold change curve for coal and gangue separation under specific geological environment for further coal and gangue separation with R value method based on dual-energy.

Investigation of the neutron radiation protective properties of chlorophyll and carotenoid

In this study, we have investigated neutron radiation absorption properties of chlorophyll and carotenoid. Our aim is to show that chlorophyll and carotenoid, which are naturally found in every green plant, can be used to make a cream, medicine, paint, or shield material against neutrons. Neutron radiation is generally used in many applications such as diffraction and scattering experiments, material crystallography, diagnosis and therapy in medicine, cell DNA studies in biology, condensed matter physics, materials research and development, solid-state chemistry, mineralogy, geology, and the study and improvement of the structural properties of materials. In order to reduce or completely eliminate the damages that can be caused by direct or scattered neutrons by the people working in these studies or other people in the environment, materials with high shielding are needed to absorb neutrons. In order to understand that chlorophyll and carotenoid can be used in the production of neutron shielding materials, the neutron radiation absorption parameters of these materials were investigated. The parameters, which are widely used in neutron shielding studies such as an effective removal cross section, half value layer, mean free path, and neutron transmission factor (NTF) were estimated using the Monte Carlo simulation GEANT4 code for both fast and epithermal neutrons. In addition, the dose rates of all samples were determined by using an 241Am–Be fast neutron source. All theoretical and experimental results obtained to understand the absorption capacities of chlorophyll and carotenoid were compared with paraffin, which is widely used in neutron shielding applications.It is to be noted that determined that chlorophyll showed an effective shielding against fast neutrons and carotenoid showed an effective shielding against epithermal neutrons. Investigation revealed that these materials are alternate shielding materials against neutron radiation for the production of medicine, composite material, and paint to be developed for neutron radiation.

Test beam measurement of ATLAS ITk Short Strip module at warm and cold operational temperature

This study is focused on an investigation of the performance of the Short Strip module developed by the ATLAS Inner Tracker (ITk) strip collaboration using electron beams of energy 5.4 GeV and 5.8 GeV at the DESY-II Testbeam Facility. The noise at +30 °C and -30 °C was measured. The ratio of the two measurements is compared with a circuit-model calculation. The measured noise at -30 °C is compared with the maximum noise that would correspond to an acceptable signal-to-noise ratio after the expected radiation damage from operation at HL-LHC. The measured charge distributions at +30 °C and -30 °C are compared with GEANT4 simulations. The detection efficiency and noise-occupancy were measured as a function of threshold at both +30 °C and -30 °C. The average cluster width was measured as a function of threshold. Scans of detection efficiency versus threshold at different delay settings were used to reconstruct the pulse shape in time. The resulting pulse shape was compared with a circuit model calculation.

On the Prospects of BaF2 as a Fast Scintillator for Time-of-Flight Positron Emission Tomography Systems

Future time-of-flight positron emission tomography (TOF-PET) will be in need of ultrafast scintillation materials, with potential seen in cross-luminescence (CL). BaF2, for example, shows a sub-100-ps decay time with 300 photons produced per MeV. However, it poses challenges, such as medium radiation length, low photofraction, moderate light yield, and vacuum ultraviolet (VUV) emission around 200nm. Recent developments in UV-sensitive solid-state photodetectors (SiPMs) have the potential to establish CL for ultrafast TOF in PET. In this work, we aim to study BaF2, read out by these new VUV SiPMs, as a viable alternative to cerium-doped lutetium–yttrium oxyorthosilicate (LYSO:Ce). In order to investigate the prospects of BaF2 in TOF-PET, we compare the CTR of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2\times $ </tex-math></inline-formula> 20 mm 3 undoped and yttrium-doped BaF2 crystals, readout by Hamamatsu S13370–3050CN SiPMs with a maximum photon detection efficiency (PDE) of 14% at 200nm and air coupling, to LYSO:Ce:Ca crystals of the same size. With high-frequency readout electronics, we reached 233ps with undoped BaF2 and 213ps with BaF2:Y, while the performance of LYSO:Ce:Ca was 125ps (measured with HPK S14160–3050HS, PDE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 60$ </tex-math></inline-formula> % and glue coupling). Conducting measurements at different depth of interaction positions shows a pronounced impact on the CTR. Furthermore, we investigated the performance for systems of BaF2 with TOFPET2c ASIC measurements and Geant4 simulations for effective sensitivity comparisons to LYSO:Ce:Ca.

A Geant4 shielding design for the first US carbon multi-ion hybrid synchrotron facility

The Mayo Clinic Florida Integrated Oncology Building will be the home of the first spot-scanning only carbon/proton hybrid therapy system by Hitachi, Ltd. It will provide proton beams up to kinetic energies of 230 MeV and carbon beams up to 430 MeV n−1 for clinical deployment. To provide adequate radiation protection, the Geant4 (v10.6) Monte Carlo toolkit was utilized to quantify the ambient dose equivalent at a 10 mm depth (H*(10)) for photons and neutrons. To perform accurate calculations of the ambient dose equivalent, three-dimensional computer-aided design files of the entire planned facility were imported into Geant4, as well as certain particle system components such as the bending magnets, fast Faraday cup, and gantry. Particle fluence was scored using 60 cm diameter spheres, which were strategically placed throughout areas of interests. Analytical calculations were performed as first-pass design checks. Major shielding slabs were optimized using Geant4 simulations iteratively, with more than 20 alternative designs evaluated within Geant4. The 430 MeV n−1 carbon beams played the most significant role in concrete thickness Requirements. The primary wall thickness for the carbon fixed beam room is 4 meters. The presence of the proton gantry structure in the simulation caused the ambient dose equivalent to increase by around 67% at the maze entrance, but a decrease in the high energy beam transport corridor. All shielding primary and secondary goals for clinical operations were met per state regulation and national guidelines.

A mathematical approach to calculate the absolute total detection efficiency of a 4[formula omitted] NaI(Tl) sum spin spectrometer

The absolute total detection efficiency of a detector for gamma rays intensely depends on the solid angle subtended by the detector’s front surface at the gamma source. In the present work, we have developed, for the first time, a new mathematical formalism to calculate the solid angle subtended by an n-sided polygonal detector at the point source when the source is placed along the axis of the detector. The method is based on the subtraction of the solid angle in which gamma rays do not enter the detector from that of the circular cross-section. The solid angle formula, so derived, has been applied to calculate the absolute total detection efficiency of NaI(Tl) scintillation detectors of pentagonal and hexagonal cross-sections for monoenergetic gamma rays. These efficiencies are then used to calculate the absolute total detection efficiency of 4π sum-spin spectrometer for gamma rays up to energy 20 MeV. The spectrometer is an array of 32 conical NaI(Tl) detectors of pentagonal and hexagonal cross-sections. To validate the formalism developed, the theoretically calculated efficiencies are compared with those obtained from realistic GEANT4 simulations and experimental measurements considering 137Cs and 60Co gamma sources. The reasonably good agreement clearly validates the developed formalism.