Monte Carlo Radiation Transport Research Articles

Perturbed recombination from inhomogeneous photon injection and application to accreting primordial black holes

Exotic electromagnetic energy injection in the early Universe may alter cosmological recombination, and ultimately cosmic microwave background (CMB) anisotropies. Moreover, if energy injection is inhomogeneous, it may induce a spatially-varying ionization fraction, and non-Gaussianity in the CMB. The observability of these signals, however, is contingent upon how far the injected particles propagate and deposit their energy into the primordial plasma, relative to the characteristic scale of energy injection fluctuations. In this study we inspect the spatial properties of energy deposition and perturbed recombination resulting from an inhomogeneous energy injection of sub-10 MeV photons, relevant to accreting primordial black holes (PBHs). We develop a novel Monte-Carlo radiation transport code accounting for all relevant photon interactions in this energy range, and including secondary electron energy deposition efficiency through a new analytic approximation. For a specified injected photon spectrum, the code outputs an injection-to-deposition Green's function depending on time and distance from the injection point. Combining this output with a linearized solution of the perturbed recombination problem, we derive time- and scale-dependent deposition-to-ionization Green's functions. We apply this general framework to accreting PBHs, whose luminosity is strongly spatially modulated by supersonic relative velocities between cold dark matter and baryons. We find that the resulting spatial fluctuations of the free-electron fraction are of the same magnitude as its mean deviation from standard recombination, from which current CMB power spectra constraints are derived. This work suggests that the sensitivity to accreting PBHs might be substantially improved by propagating these inhomogeneities to CMB anisotropy power spectra and non-Gaussian statistics, which we study in subsequent papers.

Evaluation of gamma-ray transmission through rectangular collimator slits for application in nuclear fuel spectrometry

Gamma-ray spectrometry is widely applied in several science fields, and in particular in non-destructive gamma scanning and gamma emission tomography of irradiated nuclear fuel. Often, a collimator is used in the experimental setup, to selectively interrogate a region of interest in the fuel. For the optimization of instrument design, as well as for planning measurement campaigns, predictive models for the transmitted gamma-ray intensity through the collimator are needed. Commonly, Monte Carlo radiation transport tools are used for accurate prediction of gamma-ray transport, however, the long computation time requirements when used in low-efficiency experimental setups present challenges.In this work, the full-energy peak intensity transmitted through a rectangular collimator slit was examined. A uniform planar surface source emitting isotropically was considered, and the rate of photons reaching an ideal counter plane on the opposite side of the collimator was evaluated by analytical integration. To find a closed-form primitive function, some idealizations were required, and thereby parametric models were obtained for the optical field of view, dependent on slit dimensions (length, height and width) and source-to-collimator distance. It was shown that the count rate in the detector is independent of the collimator-to-source distance. For contributions from outside the optical field of view, where a closed-form expression cannot be found, instead fast numerical integration methods were proposed.The results were validated using the Monte Carlo code MCNP6.2. For the analytical method, deviations were larger, the shorter the collimator, with up to 25% of underestimation obtained for the shortest examined collimator of 10 cm length. However, the longer the collimator, the better the observed agreement. This accuracy is deemed to be sufficient for instrument design and measurement planning, where often the order of magnitude of the count rate is not a priori known. For the numerical method, the results showed an agreement within 3% for all evaluated collimator settings.The methods are planned for use in iterative optimization routines in the design of Gamma Emission Tomography devices, as well as for the prediction of gamma spectra obtained in the planning of fuel inspections. An application of the proposed method was demonstrated in spectrum prediction for a short cooling-time fuel rod test from the Halden reactor.

Modeling bystander effects that cause growth delay of breast cancer xenografts in bone marrow of mice treated with radium-223

Rationale The role of radiation-induced bystander effects in cancer therapy with alpha-particle emitting radiopharmaceuticals remains unclear. With renewed interest in using alpha-particle emitters to sterilize disseminated tumor cells, micrometastases, and tumors, a better understanding of the direct effects of alpha particles and the contribution of the bystander responses they induce is needed to refine dosimetric models that help predict clinical benefit. Accordingly, this work models and quantifies the relative importance of direct effects (DE) and bystander effects (BE) in the growth delay of human breast cancer xenografts observed previously in the tibiae of mice treated with 223RaCl2. Methods A computational model of MDA-MB-231 and MCF-7 human breast cancer xenografts in the tibial bone marrow of mice administered 223RaCl2 was created. A Monte Carlo radiation transport simulation was performed to assess individual cell absorbed doses. The responses of the breast cancer cells to direct alpha particle irradiation and gamma irradiation were needed as input data for the model and were determined experimentally using a colony-forming assay and compared to the responses of preosteoblast MC3T3-E1 and osteocyte-like MLO-Y4 bone cells. Using these data, a scheme was devised to simulate the dynamic proliferation of the tumors in vivo, including DE and BE propagated from the irradiated cells. The parameters of the scheme were estimated semi-empirically to fit experimental tumor growth. Results A robust BE component, in addition to a much smaller DE component, was required to simulate the in vivo tumor proliferation. We also found that the relative biological effectiveness (RBE) for cell killing by alpha particle radiation was greater for the bone cells than the tumor cells. Conclusion This modeling study demonstrates that DE of radiation alone cannot explain experimental observations of 223RaCl2-induced growth delay of human breast cancer xenografts. Furthermore, while the mechanisms underlying BE remain unclear, the addition of a BE component to the model is necessary to provide an accurate prediction of the growth delay. More complex models are needed to further comprehend the extent and complexity of 223RaCl2-induced BE.

Radiation dose from computed tomography scans for Korean pediatric and adult patients.

In recent events of the Coronavirus Disease 2019 (COVID-19) pandemic, CT scans are being globally used as a complement to the reverse-transcription polymerase chain reaction (RT-PCR) tests. It will be important to be aware of major organ dose levels, which are more relevant quantity to derive potential long-term adverse effect, for Korean pediatric and adult patients undergoing CT for COVID-19. We calculated organ dose conversion coefficients for Korean pediatric and adult CT patients directly from Korean pediatric and adult computational phantoms combined with Monte Carlo radiation transport techniques. We then estimated major organ doses delivered to the Korean child and adult patients undergoing CT for COVID-19 combining the dose conversion coefficients and the international survey data. We also compared our Korean dose conversion coefficients with those from Caucasian reference pediatric and adult phantoms. Based on the dose conversion coefficients we established in this study and the international survey data of COVID-19-related CT scans, we found that Korean 7-year-old child and adult males may receive about 4 - 32 mGy and 3 - 21 mGy of lung dose, respectively. We learned that the lung dose conversion coefficient for the Korean child phantom was up to 1.5-fold greater than that for the Korean adult phantom. We also found no substantial difference in dose conversion coefficients between Korean and Caucasian phantoms. We estimated radiation dose delivered to the Korean child and adult phantoms undergoing COVID-19-related CT examinations. The dose conversion coefficients derived for different CT scan types can be also used universally for other dosimetry studies concerning Korean CT scans. We also confirmed that the Caucasian-based CT organ dose calculation tools may be used for the Korean population with reasonable accuracy.

Computational design and optimization of a neutron imaging beamline using Monte Carlo and deterministic SN radiation transport for the Utah TRIGA reactor

This paper describes efforts to establish a neutron imaging radiography capability in an available beam port at the University of Utah 90-kW TRIGA Reactor (UUTR) from computational analysis of the proposed beamline. We employ methods in 3-D Monte Carlo and SN deterministic radiation transport methods to characterize the neutron beamline before its construction. Incident beam currents established using results from 3-D SN and Monte Carlo full core models were employed as a starting point for the source term in a full-scale MCNP6 computational model of the neutron beam port system to predict the spatial and energy-dependent neutron flux expected to exit the beam pipe onto the imaging operations floor. Our analysis reveals a full-power total neutron flux of 2.5 × 107 ± 1.4 × 105n/cm2/s, where 92% of this flux streams through the surface normal within angle tally bin of 0°<θ<2°. This neutron flux is above the threshold of industrially relevant neutron flux magnitudes necessary to probe non-destructive imaging in high-Z materials and opens up possibilities for tomographic imaging. Further analysis regarding the functionality and optimal design of the beam port utilizes both Monte Carlo and deterministic 3-D radiation transport methods to characterize principal neutron beam line attributes such as the L/D ratio, theoretical cadmium ratios, neutron-to-photon ratio, effective beam diameter estimates, and predicted neutron flux to irradiated foil samples. These supplemental models are developed in efforts to solidify consistency between Monte Carlo and deterministic methods, as subsequent development of a radiation beamstop will employ a hybrid fashion of the two for variance reduction purposes. In addition, primary and secondary radiation dose rates are evaluated to assess parameters for safe installation, guide future irradiation tests, and design of a beam stop for optimal shielding.

An electromagnetic physics constructor for low energy polarised X-/gamma ray transport in Geant4

The production, application, and/or measurement of polarised X-/gamma rays are key to the fields of synchrotron science and X-/gamma-ray astronomy. The design, development and optimisation of experimental equipment utilised in these fields typically relies on the use of Monte Carlo radiation transport modelling toolkits such as Geant4. In this work the Geant4 “G4LowEPPhysics” electromagnetic physics constructor has been reconfigured to offer a best set of electromagnetic physics models for studies exploring the transport of low energy polarised X-/gamma rays. An overview of the physics models implemented in “G4LowEPPhysics”, and it’s experimental validation against Compton X-ray polarimetry measurements of the BL38B1 beamline at the SPring-8 synchrotron (Sayo, Japan) is reported. “G4LowEPPhysics” is shown to be able to reproduce the experimental results obtained at the BL38B1 beamline (SPring-8) to within a level of accuracy on the same order as Geant4’s X-/gamma ray interaction cross-sectional data uncertainty (approximately ± 5 %).

Simulating Ionising Radiation in Gazebo for Robotic Nuclear Inspection Challenges

The utilisation of robots in hazardous nuclear environments has potential to reduce risk to humans. However, historical use has been largely limited to specific missions rather than broader industry-wide adoption. Testing and verification of robotics in realistic scenarios is key to gaining stakeholder confidence but hindered by limited access to facilities that contain radioactive materials. Simulations offer an alternative to testing with actual radioactive sources, provided they can readily describe the behaviour of robotic systems and ionising radiation within the same environment. This work presents a quick and easy way to generate simulated but realistic deployment scenarios and environments which include ionising radiation, developed to work within the popular robot operating system compatible Gazebo physics simulator. Generated environments can be evolved over time, randomly or user-defined, to simulate the effects of degradation, corrosion or to alter features of certain objects. Interaction of gamma radiation sources within the environment, as well as the response of simulated detectors attached to mobile robots, is verified against the MCNP6 Monte Carlo radiation transport code. The benefits these tools provide are highlighted by inclusion of three real-world nuclear sector environments, providing the robotics community with opportunities to assess the capabilities of robotic systems and autonomous functionalities.

Quantification of the radiosensitization effect of high-Z nanoparticles on photon irradiated cells: combining Monte Carlo simulations and an analytical approach to the local effect model

In vitro experiments show significant reduction in the survival fraction of cells under irradiation treatments assisted with high-Z nanoparticles (NPs). In order to predict the radiosensitization effect of NPs, a modification of the local effect model (LEM), in which the energy deposition from NPs is assessed by Monte Carlo (MC) radiation transport codes, has been employed in the past. In this work, a combined framework that splits the consideration of the radiosensitization effect into two steps is proposed. The first step is the evaluation of the radial dose distribution (RDD) around a single NP ionized by a photon beam with given energy spectrum using MC simulation. Thereafter, an analytical approach based of the LEM and the calculated RDD is used for evaluation of the average dose and the average number of lethal lesions in a cell target due to a set of ionized NPs. The explicit expressions were derived for the case of a spherical cell target and the RDD describing by the power law function. RDDs around gold NPs (GNPs) of different radii were simulated using the MC technique and fitted by a power law function. The fitted RDD and the derived expressions were applied for calculation of the survival curves and relative biological effectiveness of a spherical MDA-MB-231 cell loaded with GNPs and irradiated with monoenergetic photons of 10–150 keV. The proposed framework provides a practical alternative to time-consuming MC simulations, enabling the assessment of the response of cell cultures to an irradiation treatment assisted with NPs for a wide variety of cell geometries, NP distributions and irradiation schemes.

Multi-objective genetic algorithm optimization of a directionally sensitive radiation detection system using a surrogate transport model

Direction-sensitive and imaging radiation detection systems often rely on complicated mask geometries to reconstruct source positions and images. Optimizing the design of these masks is difficult, often non-intuitive, and computationally intensive due to the radiation transport involved. Advances in computational resources, efficient, stochastic optimization techniques, and improved variance reduction in radiation transport through hybrid deterministic-Monte Carlo methods have enabled researchers to consider methods to find formal optimal solutions for these systems. However, many systems span a complex and large design space making full radiation transport simulations to inform the optimization routine computationally intractable. This work applies a multi-objective genetic algorithm to a generalizable surrogate model, benchmarked through full Monte Carlo radiation transport simulations, to determine the optimal design for the rotating scatter mask directionally-sensitive detection system. Performing the equivalent optimization of 10,000 design evaluations with Monte Carlo radiation transport simulations would take 460 CPU-years. In contrast, the 10,000 surrogate design evaluations produced Pareto frontiers comparable to the Monte Carlo results, while reducing the computational cost by 99.998% to 4.1 CPU-days. The chosen optimal designs maintain high directional accuracy with respect to the original design, while improving the response basis similarity by 14% and increasing the efficiency by a factor of 40 at the cost of increasing the mask’s mass by a factor of 3.

Monte Carlo calculation of the organ equivalent dose and effective dose due to immersion in a 16N beta source in air using the ICRP reference phantoms

This work summarises the results of a comparison organized by EURADOS focused on the usage of the ICRP Reference Computational Phantoms. This activity aimed to provide training for the implementation of voxel phantoms in Monte Carlo radiation transport codes and the calculation of the dose equivalent in organs and the effective dose. This particular case describes a scenario of immersion in a16N beta source distributed in the air of a room with concrete walls where the phantom is located. Seven participants took part in the comparison of results using GEANT4, TRIPOLI-4 and MCNP family codes, and there was detected a general problem when calculating the dose to skeletal tissue and the remainder tissue. After a process of feedback with the participants the errors were corrected and the final results reached an agreement of ±5%.

Tabulation of organ dose conversion factors for terrestrial radioactivity monitoring program

Terrestrial radioactivity monitoring of 238U and 232Th series, and 40K in soil is an essential practice for radioactivity and radiation measurement of a place. In conventional practice, only basic data can be in-situ measured using a survey instrument, for example radioactivity concentration in soil and ambient dose equivalent rate. For other physical quantities, for example organ absorbed dose and organ equivalent dose, the measurement is impossible to be performed and can only be computed using Monte Carlo radiation transport simulations. In the past, most of the works only focused on calculating air-kerma-to-effective dose conversion factors. However, the information on organ dose conversion factors is scarcely documented and reported. This study was conducted to calculate organ absorbed and tissue-weighted equivalent dose conversion factors as a result of exposure from terrestrial gamma radiation. Series of organ dose conversion factors is produced based on computations from Monte Carlo MCNP5 simulations using modelled gamma irradiation geometry and established adult MIRD phantom. The study found out that most of the radiation exposed organs absorb energy at comparable rates, except for dense and superficial tissues i.e., skeleton and skin, which indicated slightly higher values. The good agreement between this work and previous studies demonstrated that our gamma irradiation geometry and modelling of gamma radiation sources are adequate. Therefore, the proposed organ dose conversion factors from this study are reasonably acceptable for dose estimation in environmental radioactivity monitoring practices.

A New Fast Monte Carlo Code for Solving Radiative Transfer Equations Based on the Neumann Solution

Abstract In this paper, we propose a new Monte Carlo radiative transport (MCRT) scheme, which is based completely on the Neumann series solution of the Fredholm integral equation. This scheme indicates that the essence of MCRT is the calculation of infinite terms of multiple integrals in the Neumann solution simultaneously. Under this perspective, we redescribe the MCRT procedure systematically, in which the main work amounts to choosing an associated probability distribution function for a set of random variables and the corresponding unbiased estimation functions. We select a relatively optimal estimation procedure that has a lower variance from an infinite number of possible choices, such as term-by-term estimation. In this scheme, MCRT can be regarded as a pure problem of integral evaluation, rather than as the tracing of random-walking photons. Keeping this in mind, one can avert some subtle intuitive mistakes. In addition, the δ functions in these integrals can be eliminated in advance by integrating them out directly. This fact, together with the optimal chosen random variables, can remarkably improve the Monte Carlo (MC) computational efficiency and accuracy, especially in systems with axial or spherical symmetry. An MCRT code, Lemon (Linear integral Equations’ Monte carlo solver based On the Neumann solution; the code is available on the GitHub codebase at https://github.com/yangxiaolinyn/Lemon, and version 2.0 is archived on Zenodo at https://doi.org/10.5281/zenodo.4686355), has been developed completely based on this scheme. Finally, we intend to verify the validation of Lemon; a suite of test problems mainly restricted to a flat spacetime has been reproduced, and the corresponding results are illustrated in detail.

Optimizing the moderator geometry and thickness for a reactor-based slow positron source

Monte Carlo radiation transport simulations were used to calculate the slow positron yields from tungsten foil positron moderators at a reactor-based slow positron source. The slow positron generation rates were coupled to a simple electrostatic extraction model to estimate the yield of extractable slow positrons from the source. These calculations were used to optimize the foil thicknesses, length, pitch, and extraction voltages.

Monte Carlo approach for calculation of mass energy absorption coefficients of some amino acids

This study offers a Monte Carlo alternative for computing mass energy absorption coefficients of any material through calculation of photon energy deposited per mass of the sample and the energy flux obtained inside a sample volume. This approach is applied in this study to evaluate mass energy absorption coefficients of some amino acids found in human body at twenty-eight different photon energies between 10 keV and 20 MeV. The simulations involved a pencil beam source modeled to emit a parallel beam of mono-energetic photons toward a 1 mean free path thick sample of rectangular parallelepiped geometry. All the components in the problem geometry were surrounded by a 100 cm vacuum sphere to avoid any interactions in materials other than the absorber itself. The results computed using the Monte Carlo radiation transport packages MCNP6.2 and GAMOS5.1 were checked against the theoretical values available from the tables of XMUDAT database. These comparisons indicate very good agreement and support the conclusion that Monte Carlo technique utilized in this fashion may be used as a computational tool for determining the mass energy absorption coefficients of any material whose data are not available in the literature.

Monte Carlo simulation to assess free space and end-weld thickness variation effects on dose rate for a new Ir-192 brachytherapy source

A new Iridium-192 seed for brachytherapy is under development. Specific dose rate contribution by two different factors were evaluated: the effect from movement of the core in the free space within the seed and the effect of the end-weld thickness variation. Both were investigated through use of the Monte Carlo radiation transport code MCNP6 and an in-house routine programmed with MATLAB. Differences greater than 15% compared to results from the nominal seed were found near the source, indicating a significant dose variation.

Effect of Nd3+ ions on radiation attenuation properties of PbF2–TeO2–WO3 glass system for shielding applications

This study aims to investigate the utility of using 15PbF2–(60x)TeO2–25WO3–xNd2O3 (0.1≥x≥1.5) glasses in the nuclear shielding applications for mixed radiation fields at energies ranging from 15keV to 15MeV. The effect of Nd3+ ions on gamma attenuation properties of the present glass system was discussed in detail. The radiation attenuation features were investigated for the present glass system by using Monte Carlo radiation transport simulation via Geant4 toolkit. The simulation results were theoretically approved by using Phy-X approach over the entire considered energy range. The obtained results indicate that the values of Zeff and Neff were both highest in the in the τ/ρ dominated energies due to the atomic number dependence of the cross sections of the τ/ρ absorption processes. Moreover, FNRCS values were 0.1152, 0.1152, 0.1153, and 0.1153cm−1 for PWTN1, PWTN2, PWTN3, and PWTN4 respectively. Finally, an extensive comparative study is also presented between the studied glass system and standard traditional shielding materials. The study suggests PWTN4 is the best photon shield amongst the studied PWTN-glasses.

Dose conversion coefficients for neutron external exposures with five postures: walking, sitting, bending, kneeling, and squatting.

In a previous study, posture-dependent dose coefficients (DCs) for photon external exposures were calculated using the adult male and female mesh-type reference computational phantoms (MRCPs) of the International Commission on Radiological Protection (ICRP) that had been transformed into five non-standing postures (i.e. walking, sitting, bending, kneeling, and squatting). As an extension, the present study was conducted to establish another DC dataset for external exposures to neutrons by performing Monte Carlo radiation transport simulations with the adult male and female MRCPs in the five non-standing postures. The resulting dataset included the DCs for absorbed doses (i.e., organ/tissue-averaged absorbed doses) delivered to 29 individual organs/tissues, and for effective doses for neutron energies ranging from 10-9 to 104MeV in six irradiation geometries: antero-posterior (AP), posteroanterior (PA), left-lateral (LLAT), right-lateral (RLAT), rotational (ROT), and isotropic (ISO) geometries. The comparison of DCs for the non-standing MRCPs with those of the standing MRCPs showed significant differences. In the lateral irradiation geometries, for example, the standing MRCPs overestimate the breast DCs of the squatting MRCPs by up to a factor of 4 due to the different arm positions but underestimate the gonad DCs by up to about 17 times due to the different leg positions. The impact of different postures on effective doses was generally less than that on organ doses but still significant; for example, the standing MRCPs overestimate the effective doses of the bending MRCPs only by 20% in the AP geometry at neutron energies less than 50MeV, but underestimate those of the kneeling MRCPs by up to 40% in the lateral geometries at energies less than 0.1MeV.

Investigation and comparison of neutron image quality using monochromatic and polychromatic beams of Tehran Research Reactor by Monte Carlo simulation

Neutron radiography (NR) is a non-destructive testing (NDT) method which uses a neutron beam for materials investigation in the research and industrial application. In this work, the quality of the neutron radiography system based on thermal monochromatic and polychromatic beam tubes of the Tehran Research Reactor (TRR) has been studied and compared using Monte Carlo simulation. MCNPX is a Monte Carlo radiation transport code with a built-in radiography feature that has been used The parameters of neutron images have been evaluated by several standard test samples qualitatively and quantitatively. The image analysis of standard samples shows that the thermal neutron content of the monochromatic beam is about 29.8% more than a polychromatic beam. Moreover, the simulation results have been validated by measured quality parameters of the polychromatic neutron beam at the E channel of TRR which are in good agreement. The results show that the monochromatic neutron beam with a wavelength of 2.9 Å can have a lower neutron intensity by 36% on average for iron, brass, copper, and polyethylene. However, there was no significant difference between polychromatic beam and neutron beam at a wavelength of 1.75 Å for these materials. Furthermore, a polychromatic beam provides a better performance to show different percentages of uranium enrichment of fuel rods in the images than the monochromatic beam. So that, the maximum difference is about 90.09% between transmitted neutron intensities of rods with enrichment of 12 and 20% by a polychromatic beam.

The global optimal reference field for the difference formulation in the implicit Monte Carlo radiation transport

Statistical noise has always been one of the most important problems hindering the wide application of the Monte Carlo method in thermal radiative transfer. The difference formulation which has been introduced in recent years is a source manipulation variance reduction technique, in which the radiation intensity is defined relative to a reference field. In this formulation, the transport operator remains unchanged, but the solution and source functions are changed. Numerical results show that in this formulation the symbolic implicit Monte Carlo (SIMC) method can significantly reduce statistical noise in some cases. The standard formulation can be considered as a special formulation where the reference field is zero. In general, the reference field is chosen as the thermal equilibrium radiation field at the beginning or end of the time step. However, we found that this choice can lead to a larger statistical noise than in the standard formulation in some cases, and even non-physical oscillation of the calculation results, which severely restrict the application of this method.In this paper, we develop the difference formulation based on generalized reference fields, and the Fleck-Cummings implicit Monte Carlo technique is employed to solve the functions. Through analysis, we find that the choice of the reference field is the key to reduce statistical noise. We define the global optimal reference field, which satisfies the minimum for the L1 norm of energy weights of the particles emitted during a time step. Although it is difficult to find the global optimal reference field, we propose a scheme to select a reference field which satisfies that the statistical noise is lower than the zero reference field in most cases. Numerical results show that the new method can avoid the nonphysical oscillation that occurs in regions of the problem with sharp spatial gradients in the solution in the classical difference formulation. The method also leads to a remarkable reduction in noise comparing to the Fleck-Cummings implicit Monte Carlo method in the standard formulation.

Verification of KURBUC-based ion track structure mode for proton and carbon ions in the PHITS code

The particle and heavy ion transport code system (PHITS) is a general-purpose Monte Carlo radiation transport simulation code. It has the ability to handle diverse particle types over a wide range of energy. The latest PHITS development enables the generation of track structure for proton and carbon ions (1H+, 12C6+) based on the algorithms in the KURBUC code, which is considered as one of the most verified track-structure codes worldwide. This ion track-structure mode is referred to as the PHITS-KURBUC mode. In this study, the range, radial dose distributions, and microdosimetric distributions were calculated using the PHITS-KURBUC mode. Subsequently, they were compared with the corresponding data obtained from the original KURBUC and from other studies. These comparative studies confirm the successful inclusion of the KURBUC code in the PHITS code. As results of the synergistic effect between the macroscopic and microscopic radiation transport codes, this implementation enabled the detailed calculation of the microdosimetric and nanodosimetric quantities under complex radiation fields, such as proton beam therapy with the spread-out Bragg peak.