Calculation Of Energy Deposition Research Articles

Radiation-induced DNA damage by proton, helium and carbon ions in human fibroblast cell: Geant4-DNA and MCDS-based study

Background. Radiation-induced DNA damages such as Single Strand Break (SSB), Double Strand Break (DSB) and Complex DSB (cDSB) are critical aspects of radiobiology with implications in radiotherapy and radiation protection applications. Materials and Methods. This study presents a thorough investigation into the effects of protons (0.1–100 MeV/u), helium ions (0.13–100 MeV/u) and carbon ions (0.5–480 MeV/u) on DNA of human fibroblast cells using Geant4-DNA track structure code coupled with DBSCAN algorithm and Monte Carlo Damage Simulations (MCDS) code. Geant4-DNA-based simulations consider 1 μm × 1 μm × 0.5 μm water box as the target to calculate energy deposition on event-by-event basis and the three-dimensional coordinates of the interaction location, and then DBSCAN algorithm is used to calculate yields of SSB, DSB and cDSB in human fibroblast cell. The study investigated the influence of Linear Energy Transfer (LET) of protons, helium ions and carbon ions on the yields of DNA damages. Influence of cellular oxygenation on DNA damage patterns is investigated using MCDS code. Results. The study shows that DSB and SSB yields are influenced by the LET of the particles, with distinct trends observed for different particles. The cellular oxygenation is a key factor, with anoxic cells exhibiting reduced SSB and DSB yields, underscoring the intricate relationship between cellular oxygen levels and DNA damage. The study introduced DSB/SSB ratio as an informative metric for evaluating the severity of radiation-induced DNA damage, particularly in higher LET regions. Conclusions. The study highlights the importance of considering particle type, LET, and cellular oxygenation in assessing the biological effects of ionizing radiation.

Monte Carlo electron transport simulation study based on NPTS program

Monte Carlo programs are increasingly considered the most accurate tool for simulating particle transport problems. The neutron-photon transport simulation capabilities of domestic particle transport Monte Carlo softwares are relatively advanced, while the electron transport simulation functions have not been well developed yet. This paper independently developed the functions of electron transport and photon-electron transport in the CH (condensed history technique) scheme based on the NPTS (Neutron Photon Transport System) program, and implemented the multi-coupling transport simulation of neutrons, photons, and electrons, which can meet the needs of actual applications. Several test models were run on both NPTS and the popular programs such as EGS and RMC to verify the correctness of NPTS. In addition, an energy deposition tally is developed. It is shown both theoretically and experimentally that the energy deposition calculation by NPTS are more accurate than RMC.

A New Model of Solar Ultraviolet Irradiance Variability With 0.1–0.5 nm Spectral Resolution

AbstractObservations of solar irradiance made from space since 2003 with 0.1 nm spectral resolution at wavelengths from 115 to 310 nm and 0.5 nm spectral resolution at wavelengths from 260 to 500 nm are used to construct a new model, NRLSSI2h, of solar irradiance variability with higher spectral resolution than the 1 nm NRLSSI2 model used to specify the NOAA Solar Irradiance Climate Data Record. The new model better resolves irradiance variability in specific emission and absorption features that are directly attributable to atoms and molecules in the Sun’s atmosphere. Singularly prominent is spectral irradiance variability at 379–389 nm, dominated by the CN molecular band system; irradiance in this 10 nm band increased 0.078 W m−2 during solar cycle 23, contributing 4.6% of the 1.7 W m−2 concurrent total solar irradiance increase. Irradiance variability at wavelengths from 300 to 400 nm, a region dominated by multiple spectral features, is a factor of 2–5 smaller in the new model than estimated by semiempirical models that use radiative transfer codes to calculate the contrasts of faculae and sunspots, which alter the temperature‐dependent densities of these species relative to the surrounding continuum. Solar atmosphere temperature and composition profiles in radiative transfer models may therefore not be realistic or their atomic and molecular databases may be incomplete. Improved colocation of spectral features in solar irradiance and the absorption cross sections of molecular oxygen and ozone with the new model may allow higher fidelity calculations of energy deposition in Earth’s atmosphere.

Modification of the fusion energy gain factor in magnetic confinement fusion due to plasma temperature anisotropy

In magnetic confinement fusion (MCF), the plasma always exhibits an anisotropic temperature distribution, which may impact not only the plasma dynamics but also the nuclear reaction process. Here, through theoretical derivations and self-consistent particle-in-cell simulations with the newly-developed nuclear reaction and alpha particle energy deposition calculation modules, we find that, if considering the plasma has an anisotropic temperature distribution, the fusion energy gain factor (Q) of MCF is significantly modified, where both the deuteron–triton nuclear reactivity and the alpha particle energy deposition fraction are heavily influenced. The simulation results show that, under the International Thermonuclear Experimental Reactor (ITER) condition, if the plasma temperature anisotropy ratio can reach 0.1, i.e., the plasma perpendicular temperature component is one-tenth of its parallel component corresponding to the ambient magnetic field direction, the Q-value of ITER can be increased from the originally-designed 5 to about 10, with doubled enhancement.

Optimizing the GPU based method calculating energy deposition of beams coupling with discrete materials in dynamical and thermal simulations for higher computing efficiency

In order to obtain more accurate energy deposition simulation results of beams coupling with discrete materials especially the granular materials in dynamical and thermal simulations, a discrete energy deposition calculation method was proposed previously to replace the equivalent homogenization method and accelerated with GPUs (Tian et al., 2021 [10]). However, it was found that the computing efficiency drops so severely with the increasing of the energy space size and the time required for simulations increases greatly unacceptably. In this work, for higher computing performance, based on the bottleneck analyses of CUDA (Compute Unified Device Architecture) kernels of the previous method, two improvements were made to the space cell marking phase and the energy deposition phase. In the space cell marking phase, a new proposed Lagrange-Euler Mapping Method searching the fixed space cells through flowing grains replaced the previous Euler Searching Method searching the flowing grains from fixed space cells. In the energy deposition phase, a warp aggregation method was used, assigning fewer threads to perform atomic operations. In the simulation of a granular-flow target bombarded by a 1 GeV proton beam setting a large energy computing space with a number of cells up to ∼108, the improved algorithm can effectively reduce the number of memory access instructions of CUDA warps. As a result, the computing performance was improved by 85% on A100 GPUs and 206% on K80 GPUs, making the dynamical and thermal simulations of granular-flow targets more efficient. Our method also could be beneficial for simulating the interactions between arbitrary source (or field) with a fixed spatial distribution and discrete materials.

High-order diamond differencing schemes for the Boltzmann Fokker–Planck equation in 1D and 2D Cartesian geometries

This paper presents the implementation of high-order diamond differencing schemes, specifically the DD1 and DD2 schemes which are 4th- and 6th-order accurate respectively, to handle the spatial discretization of the Boltzmann Fokker–Planck equation in 1D and 2D Cartesian geometries. While being as computationally expensive as linear/quadratic discontinuous Galerkin schemes, the DD1/DD2 schemes are respectively an order more accurate. The energy deposition calculations presented in this work show that, besides providing correction to the oscillations and a reduced propensity to yield negative fluxes than the classical diamond difference closure relation, they tend to perform better than discontinuous Galerkin schemes, even in regions with abrupt variations of the solution due to rapid energy loss, to interface implying high-Z variations and to domain borders.

A fast and accurate GPU based method on simulating energy deposition for beam-target coupling with granular materials

The simulation of beam energy transfer and medium dynamics is essential in nuclear studies and designs involving the beam loading on targets. Although the existing methods are relatively mature in simulating the thermohydrodynamics of a solid or liquid target coupled with an energetic beam, they may not be entirely applicable to a complex porous medium such as granular materials with massive discrete elements. In this study, a GPU (Graphics Processing Unit) based discrete energy deposition simulation method is proposed for the thermohydrodynamical simulation of granular flow targets with beam-grain coupling. The results of physical validations show that a significant improvement in accuracy was achieved by our method compared to the equivalent homogenization method which just simplified the granular medium to a whole block. This method provides a more accurate alternative solution to the problem of calculating energy deposition on grains. Although the method is computationally intensive, it can be synchronously executed with the granular dynamics simulation owing to the powerful parallel computing capability of GPUs. Thus, the studies on the dynamical and thermal behaviors of beam-grain coupling can be conducted in a relatively fast and precise way.

The adequacy of energy deposition over thermodynamic behaviour in explaining the acoustic energy in bubble nucleation of superheated droplets

Sufficient amount of energy deposition through the energetic particles initiate bubble nucleation in the superheated liquid by producing the critical sized vapor bubble and subsequent growth of the bubble occurs by emitting the acoustic energy. The sensitive region of bubble nucleation changes by controlling the reduced superheat of the superheated liquid. The electrons sensitivity arises at higher reduced superheat as compared to the recoil nuclei. In the present work, we have observed the discrimination between the acoustic energy released due to both the recoil nuclei and electrons induced nucleation in superheated liquids like R-134a (containing the low Z nuclei) and in R-12 (of high Z nuclei). The experimental results show opposite trend in the two liquids. The experimental results are explained by the thermodynamic calculation and by the calculation of energy deposition of the recoil nuclei and electrons in the liquid.

Energy deposition calculation by Monte Carlo simulation in irradiation of electric cables by electron beam

The reason for crosslinking the insulation polymer in wire and cable by radiation is to improve their performance at an elevated temperature, the chemical resistance, toughness and abrasion resistance in use. The quality of products made by radiation processing depends not only on the absorbed dose but also on homogenuity of dose distribution especially in circular objects like cables which have different density in conductor and insulation part, respectively.It is important to optimize crosslinking processes for reducing the operation cost while sustaining suitable quality of the final product. The computer simulation method becomes a very useful tool for optimizing process, providing essential information in a short time and reducing cost comparing with the conventional method based on experimental dosimetry. The application of several Monte Carlo codes for electron and photon transport and the advances in computing systems, make possible to accomplish dosimetry tasks by numerical simulation. With increased computing speed and decreasing hardware cost, it is expected that Monte Carlo based electron dose calculation algorithms will become available for routine electron beam dosimetry. We have developed the EBSCANmc (simulator program) in order to simulate and study the crosslinking of electric cables. EBSCANmc employs the MCNP (Monte Carlo N-Particle) 6.2 code, which is a general purpose Monte Carlo particle transport code. The computer simulation of the dose distributions in electric cables was performed for various process parameters, namely the level of electron beam energy, irradiation positions, the density of cable insulator, and backscattering. The results of computer simulation are compared with experimental data using the CTA film dosimeter.

Calculations of energy deposition and ionization in the 2019 novel coronavirus by electron beam irradiation

Using Monte Carlo methods, this study investigates energy deposition of energetic electrons and ionization in the 2019 novel coronavirus by electron irradiation, which are important characteristic quantities related with biological damage formation. The inelastic scattering of low-energy electrons (<10 keV) was calculated by dielectric theory. The optical energy-loss functions of viral proteins and RNA were derived from an empirical method in the energy-loss range <40 eV and the calculation of optical parameters of the biomolecules. The densities and distributions of energy deposition and ionization were calculated from the stopping power and inelastic cross-sections in the electron-cascade simulation. Electrons with primary energies of approximately 1–3 keV produced significant energy deposition and ionization in the target coronavirus. More energetic electrons were less effective due to the larger electron range and fewer scattering events in the coronavirus.

Simulation of energy loss of fractionally charged particles using Geant4

Over the years several rare-event search experiments have shown increasing interest to search for Fractionally Charged Particles (FCPs) within the data acquired in those experiments. This, in turn, has required the need for a framework to calculate accurately the energy loss expected from FCPs as they pass through the detector material. We have developed Monte Carlo methods within Geant4 to simulate for the first time energy loss of FCPs through different physics processes. The program can be used to calculate energy deposition distributions, a major component of any FCP search analysis, as they interact with detector material. We discuss the implementation and validation of the energy loss of FCPs using a typical detector material.

Prostate volume and age are predictors of energy delivery using the CoreTherm Concept in patients with LUTS/BPO: a study on thermal dose

Objective: The primary aim of this study was to evaluate the scientific evidence supporting the use of thermal dose as a secondary (or an alternative) endpoint when using the CoreTherm Concept.Material and methods: Baseline and treatment data from 283 consecutive treatments were evaluated. All patients had lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH). After evaluation, benign prostatic enlargement (BPE) with benign prostatic obstruction (BPO) was evident. As treatment, the CoreTherm Concept was used in all patients with LUTS/BPO. Data parameters were retrospectively extracted and included patient age, prostate volume, energy delivery, treatment time and calculated cell kill. In addition, assessment of temperature curves and calculated intraprostatic blood flow was made to define an optimal treatment. In total, 199 treatments assessed as optimal were included in the study.Results: There was a significant correlation between pretreatment prostate volume and energy delivery (p < .001). Age also influenced energy consumption significantly (p = .01).Conclusion: The solid correlation between pretreatment prostate volume and age versus total energy deposition implies the recommendation that a pretreatment calculation of an appropriate energy deposition should be used in all treatments as an alternative treatment endpoint.

Experimental study of humidity effect on charge measurement of reference ionization chambers in clinical high-energy photon beams.

In the practice code of dosimetry, humidity effect is assumed to be constant as far as the measurements are performed in the relative humidity (RH) range of (20-80)%; thus, the humidity effect can be ignored with a dose uncertainty of 0.15%. This assumption is based on the previous experimental results by Niatel and Guiho. Rogers and Ross calculated the stopping power ratio of humid air and dry air for high-energy electron beams by using a Monte Carlo code. They demonstrate that the W value, the mean energy required to create an ion pair in air, is independent of the beam quality when the air is dry, and that the traditional humidity correction can be used also for high-energy photon and electron beams; however, this was only a computational study. In the present study, we measured the humidity correction of Farmer-type ionization chambers in high-energy photon beams and determined the W values of humid air using the calculated energy deposition of humid air with a Monte Carlo code. Furthermore, we proposed an analytical expression to determine a practical humidity correction for an ionization chamber as a function of absolute humidity. Experiments were carried out using a clinical linear accelerator (linac, Elekta Precise) at the National Metrology Institute of Japan (NMIJ). A shield box was constructed downstream of the linac and connected to an air processor, which maintained the temperature around 22°C and controlled the humidity in the range of (10-70)% inside the box. We prepared two Farmer-type ionization chambers: PTW 30013 and Exradin A19. Each ionization chamber was placed inside the box and irradiated with 6-, 10-, and 15-MV high-energy photon beams from the clinical linac. The energy deposition to the humid air inside the ionization chamber was calculated using the Electron Gamma Shower Version 5 (EGS5) code system. Stabilization for the humidity of the ionization chamber was completed within 3h. The polarity and ion recombination corrections did not show any change in the humidity range studied. The measured humidity correction and the evaluated W values of humid air in high-energy photon beams were in good agreement with those by Rogers in TG-21 and by Niatel in the range of RH (10-70)%. Humidity correction of ionization chambers in high-energy photon beams from the clinical linac was determined experimentally. Using the analytical expression for the energy depositions by EGS5, the analytical expression for the W values was also derived.

Starburst and post-starburst high-redshift protogalaxies

Quenching of star-formation has been identified in many starburst and post-starburst galaxies, indicating burst-like star-formation histories (SFH) in the primordial Universe. Galaxies undergoing violent episodes of star-formation are expected to be rich in high energy cosmic rays (CRs). We have investigated the role of these CRs in such environments, particularly how they could contribute to this burst-like SFH via quenching and feedback. These high energy particles interact with the baryon and radiation fields of their host via hadronic processes to produce secondary leptons. The secondary particles then also interact with ambient radiation fields to generate X-rays through inverse-Compton scattering. In addition, they can thermalise directly with the semi-ionised medium via Coulomb processes. Heating at a rate of ∼10−25 erg cm−3 s−1can be attained by Coulomb processes in a star-forming galaxy with one core-collapse SN event per decade, and this is sufficient to cause quenching of star-formation. At high-redshift, a substantial amount of CR secondary electron energy can be diverted into inverse-Compton X-ray emission. This yields an X-ray luminosity of above 1041 erg s−1by redshiftz = 7 which drives a further heating effect, operating over larger scales. This would be able to halt inflowing cold gas filaments, strangulating subsequent star-formation. We selected a sample of 16 starburst and post-starburst galaxies at 7 ≲ z ≲ 9 and determine the star-formation rates they could have sustained. We applied a model with CR injection, propagation and heating to calculate energy deposition rates in these 16 sources. Our calculations show that CR feedback cannot be neglected as it has the strength to suppress star-formation in these systems. We also show that their currently observed quiescence is consistent with the suffocation of cold inflows, probably by a combination of X-ray and CR heating.

Comparison of ionization track structure models for electronic devices of different sizes

The effect of the ionization track structure of the heavy ion deposited charge by direct ionization on the energy deposition calculation for single event upset (SEU) rate prediction is investigated using Geant4 based on Monte Carlo transport code. The limitations of using linear energy transfer (LET) as the single parameter to determine the energy deposited in the sensitive volume (SV) are analyzed. Track effects are becoming of great importance with technology downscaling. Three track structure models are summarized, and the applicability of track structure models for high energy ions (>8.0 MeV/amu) and low energy ions (<0.3 MeV/amu) with the same LET to devices of different sizes is discussed. It is revealed that the selection of an appropriate track structure model requires a comprehensive consideration of electronic device size and ion energy.

Monte Carlo simulations used to calculate the energy deposited in the coronary artery lumen as a function of iodine concentration and photon energy

Purpose: To better understand the risks of cumulative medical X-ray investigations and the possible causal role of contrast agent on the coronary artery wall, the correlation between iodinated contrast media and the increase of energy deposited in the coronary artery lumen as a function of iodine concentration and photon energy is investigated.Materials and methods: The calculations of energy deposition have been performed using Monte Carlo (MC) simulation codes, namely PENetration and Energy LOss of Positrons and Electrons (PENELOPE) and Monte Carlo N-Particle eXtended (MCNPX). Exposure of a cylinder phantom, artery and a metal stent (AISI 316L) to several X-ray photon beams were simulated.Results and discussion: For the energies used in cardiac imaging the energy deposited in the coronary artery lumen increases with the quantity of iodine. Monte Carlo calculations indicate a strong dependence of the energy enhancement factor (EEF) on photon energy and iodine concentration. The maximum value of EEF is equal to 25; this factor is showed for 83 keV and for 400 mg Iodine/mL. No significant impact of the stent is observed on the absorbed dose in the artery for incident X-ray beams with mean energies of 44, 48, 52 and 55 keV.Conclusion: A strong correlation was shown between the increase in the concentration of iodine and the energy deposited in the coronary artery lumen for the energies used in cardiac imaging and over the energy range between 44 and 55 keV. The data provided by this study could be useful for creating new medical imaging protocols to obtain better diagnostic information with a lower level of radiation exposure.

Investigation of track structure and condensed history physics models for applications in radiation dosimetry on a micro and nano scale in Geant4

Monte Carlo methods apply various physical models, either condensed history (CH) or track structure (TS), to simulate the passage of radiation through matter. Both CH and TS models continue to be applied to radiation dosimetry investigations on a micro and nano scale. However, as there has been no systematic comparison of the use of these models for such applications there can be no quantification of the uncertainty that is being introduced by the choice of physics model. A comparison of CH and TS models available in Geant4, along with a quantification of the differences in calculated quantities on a micro and nano scale, has been undertaken in this study. A sphere of liquid water was simulated, with an incident beam of monoenergetic electrons with kinetic energy between 50 eV and 10 keV. The energy deposition (typical of microdosimetry) and number of ionisations (typical of nanodosimetry), per incident particle, were recorded in a water sphere with diameter varying between 1 nm and 1 m. The simulations were repeated using the following physics packages: Livermore (CH), Penelope (CH) and Geant4-DNA (TS). Results indicated that substantial differences were present between calculated physical quantities, depending on the physics model, target diameter and ratio of the target diameter and mean track length of the incident electron. In the case of the smallest targets, the calculated energy deposition was higher when using the CH models, while the number of ionisations was typically underestimated. In larger targets the energy deposition was in good agreement for all physics models, however the number of ionisations was significantly underestimated by the CH approach, in some cases by almost two orders of magnitude. Regarding CH models, the parameter that had the greatest impact on the results was found to be the threshold of production of secondary particles; when this was minimised the CH and TS results showed the best agreement.

PO-0792: Monte-Carlo calculated energy deposition and nanodosimetric quantities around a gold nanoparticle

PO-0792: Monte-Carlo calculated energy deposition and nanodosimetric quantities around a gold nanoparticle

Application of FLUKA code to gamma-ray attenuation, energy deposition and dose calculations

Application of FLUKA code to gamma-ray attenuation, energy deposition and dose calculations

Access of energetic particles to Titan׳s exobase: A study of Cassini׳s T9 flyby

We study how the local electromagnetic disturbances introduced by Titan affect the ionization rates of the atmosphere. For this, we model the precipitation of energetic particles, specifically hydrogen and oxygen ions with energies between 1keV and 1MeV, into Titan׳s exobase for the specific magnetospheric configuration of the T9 flyby. For the study, a particle tracing software package is used which consists of an integration of the single particle Lorentz force equation using a 4th order Runge–Kutta numerical method. For the electromagnetic disturbances, the output of the A.I.K.E.F. hybrid code (kinetic ions, fluid electrons) is used, allowing the possibility of analyzing the disturbances and asymmetries in the access of energetic particles originated by their large gyroradii. By combining these methods, 2D maps showing the access of each set of particles were produced. We show that the access of different particles is largely dominated by their gyroradii, with the complexity of the maps increasing with decreasing gyroradius, due to the larger effect that local disturbances introduced by the presence of the moon have in the trajectory of the particles with lower energies. We also show that for particles with gyroradii much larger than the moon׳s radius, simpler descriptions of the electromagnetic environment can reproduce similar results to those obtained when using the full hybrid simulation description, with simple north–south fields being sufficient to reproduce the hybrid code results for O+ ions with energies larger than 10keV but not enough to reproduce those for H+ ions at any of the energies covered in the present study. Finally, by combining the maps created with upstream plasma flow measurements by the MIMI/CHEMS instrument, we are able to estimate normalized fluxes arriving at different selected positions of the moon׳s exobase. We then use these fluxes to calculate energy deposition and non-dissociative N2 ionization rates for precipitating O+ and H+ ions and find differences in the ion production rates of up to almost 80% at the selected positions. All these results combined show that the electromagnetic field disturbances present in the vicinity of Titan significantly affect the contribution of energetic ions to local ionization profiles.