Mixed Radiation Research Articles

Monte Carlo simulation of semiconductor-based detector in mixed radiation field in the atmosphere

Calculation of radiation protection quantities in tissue equivalent material from measurements using semiconductor detectors requires correction factors for conversion of the measured values in the semiconductor material to the tissue equivalent material. This approach has been used many times in aircraft and for space dosimetry. In this paper, we present the results of Monte Carlo simulations which reveal the need to take into account both the radiation field and the detector material when performing the conversion of measured values to radiation protection quantities. It is shown that for low Z target material, most of the dose equivalent at aviation altitudes comes from neutrons originating from nuclear reactions, while in high Z targets most of the dose equivalent comes from photons, originating from electromagnetic reactions.

Microdosimetric Modeling of Relative Biological Effectiveness for Skin Reactions: Possible Linkage Between In Vitro and In Vivo Data

Precise evaluation of the relative biological effectiveness (RBE) for skin reactions is indispensable for the treatment planning of particle therapy and boron-neutron capture therapy. The evaluation is also needed for the future radiation protection system for mixed radiation fields. Such RBE is often evaluated based on in vitro cell survival data, but its validity remains incompletely understood. This study aimed to develop a model for estimating RBE for skin reactions and dermal cell survival in the same framework and quantitatively discuss a possible link between them. The microdosimetric kinetic model, which was originally developed for estimating cell surviving fractions for various radiations, was improved to be capable of estimating the mean and uncertainty of RBE for skin reactions. The parameter used in the model was independently determined from in vitro measurements of dermal cell survival and in vivo measurements of skin reactions taken from 8 and 23 articles, respectively. In the parameter determination, the characteristics of the radiation fields employed in each measurement were reproduced in detail by the Particle and Heavy Ion Transport Code System. Our model quantitatively revealed that RBE for skin reactions tend to be higher than those for dermal cell survival. RBE of various monoenergetic radiations calculated from this model confirmed that the past evaluations made by the International Commission on Radiological Protection and the National Council on Radiation Protection and Measurements a few decades ago are still supported by recent experimental data. Our model can play important roles not only in medical physics for avoiding unnecessary skin reactions in particle therapy and boron-neutron capture therapy but also in radiation protection for future decision-making of the recommended RBE values.

Synergistic Effects of Ionizing Dose and Displacement Damage on SiGe Heterojunction Bipolar Transistors

The individual and mixed radiation experiments of gamma rays and neutrons were performed to evaluate the irradiation synergistic effects (ISEs) of ionizing dose and displacement damage on SiGe heterojunction bipolar transistors (HBTs). These results indicate that the SiGe HBTs in this work experience a significant sensitivity of ISEs and the degradation of base current induced by mixed irradiation was more severe than that of simple artificial sum of individual irradiation. The degradation of SiGe HBTs induced by mixed radiation does not vary with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {BE}}$ </tex-math></inline-formula> linearly, but is significant at low injection and weakened at high injection.

“Quantum Pendants” - the measurement of exposure to enhanced natural radioactivity

Different methods of alternative medicine may cause increased exposure to humans due to natural radioactivity. “Scalar energy medallions”, also known as “Quantum Pendants”, were investigated in the present work. Such objects are easily available in herbal stores or online. The elevated concentration of natural radionuclides from thorium series (232Th) and uranium series (238U) were measured in such pendants. The measured concentrations reached values up to 49 100 Bq·kg−1 for 228Ra, 51 600 Bq·kg−1 for 228Th, and 7 900 Bq·kg−1 for 238U and 226Ra. Radioactive disequilibrium among radionuclides was observed and this fact may be indirect evidence of the industrial (not natural) origin of these materials. Therefore, such medallions should be considered as NORM (Naturally Occurring Radioactive Materials) or TENORM (Technologically Enhanced NORM). According to the suppliers, the medallions should be carried directly on the skin of the human chest. Therefore, elevated radiation exposure is expected. Due to the presence of natural radionuclides in elevated concentrations, a mixed radiation field is the source of exposure to humans. Such conditions imply some metrological difficulties due to complex types of radiation. The article presents a proposal for a measurement approach in such cases. The effective dose from beta, X and gamma radiation for the human body was measured with the use of body phantoms and Panasonic thermoluminescent (TL) dosimeters. Various combinations of TL detectors, radiation filters and calculation protocols were applied to determine the doses from beta, X and gamma radiation. The obtained total effective dose exceeds the limit for the general population – 1 mSv.

Two-Dimensional Mixed Convection and Radiative Al2O3-Cu/H2O Hybrid Nanofluid Flow over a Vertical Exponentially Shrinking Sheet with Partial Slip Conditions

Hybrid nanofluid is considered a modern and improvised form of nanofluid which usually used to enhance the performance of heat transfer in fluid flow systems. Previous studies found hybrid nanofluid offered a wide range of applications and this opened up numerous new opportunities to further explore the unknown behaviour of hybrid nanofluid under different body geometries and physical parameters. This paper numerically studied a two-dimensional mixed convection and radiative Al2O3-Cu/H2O hybrid nanofluid flow over a vertical exponentially shrinking sheet with partial slip conditions. The main objective is to investigate the effect of mixed convection and radiation on the velocity and temperature profiles, as well as the effect of suction on reduced skin friction and reduced heat transfer with respect to solid volume fraction of copper, velocity, and thermal slips. Exponential similarity variables transformed the governing system of partial differential equations into a system of ordinary differential equations which is solved via MATLAB’s bvp4c solver. Outcomes showed that the value of the reduced heat transfer upsurges in the first solution but declines in the second solution when the velocity slip rises. The reduced heat transfer decreases in both dual solutions when thermal slip is enhanced. As the intensity of thermal slip increases, the reduced skin friction rises in the first solution and decreases in the second. As the mixed convection parameter increases, no obvious variation is noticed in the temperature distribution within the first solution, but increasing trend is observed within the second solution. An increment in the temperature distribution also observed within the dual solutions as the thermal radiation parameter increases. In summary, findings from this study are particularly useful to understand various behaviour of Al2O3-Cu/H2O hybrid nanofluid under the influence of mixed convection, radiation, and partial slip conditions when it flows over a vertical exponential shrinking sheet.

Controlling discharge mode in electrical activities of myocardial cell using mixed frequencies magnetic radiation

Based on the standard Fitzhugh–Nagumo model for myocardial cell excitations and electrical activities, the effect of electromagnetic induction is considered and through which mixed frequencies magnetic radiation is imposed to detect the mode transition. Indeed, time-varying electromagnetic field can be induced when myocardial cell is exposed or surrounded by electromagnetic field and thus the effect of electromagnetic induction should be considered. From the analyzes of sampled series for membrane potentials, the improved model holds many bifurcation parameters and the mode of excitations and electric activities can be detected and observed in larger parameter zones. It is found that apart from exciting a myocardial cell, the mixed frequencies magnetic radiation can promote mode transition to bursting type behavior as the frequency is increased as well as suppress the electrical activities to quiescent state under high intensities magnetic radiations, which are consistent with biological experiments.

Introduction and implementation of the CMRP radiodosimeter — a novel wireless microdosimetry system

Microdosimetry is a useful method to evaluate the relative biological effectiveness (RBE) as well as dose equivalent of any mixed radiation field without prior knowledge of type of charged particles and their spectra. The need of portable, user friendly devices for microdosimetric Quality Assurance measurements in particle therapy are greatly preferable to avoid sophisticated setup and time-consuming data analysis.Currently, the ability to perform microdosimetric measurements is restricted to those with extensive prior knowledge of the electronics involved and their experimental setup.The Centre for Medical Radiation Physics (CMRP) has developed a compact microdosimetric system named Radiodosimeter - a novel acquisition system that combines both wireless communication and plug-and-play design to provide a device that can be used with minimal setup. The system is compatible with current CMRP MicroPlus probe technology. The Radiodosimeter communicates with the client computer via Wi-Fi, allowing remote management and monitoring of acquisitions.The system was bench-marked against the standard microdosimetric setup at Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan and was found to have the same response. Several redundancy methods were demonstrated such as continuing an acquisition following disconnection from the client software and the ability to connect through different Wi-Fi modes (WPA2 Personal/Enterprise).These features prove that the Radiodosimeter can operate independently of a client computer, indicating its potential to be used as a portable device for personal monitoring in mixed radiation fields, including for microdosimetric quantity verification predicted by Treatment Planning Software in particle therapy.

Effect of internal heat source and non-independent thermal properties on a convective–radiative longitudinal fin

In the current research, the mixed convection and radiation heat transfer for a longitudinal fin with a constant velocity and considering heat source is analytically investigated. Two effective analytical methods called Method of Moments (MOM) and Least Square Method (LSM) will be employed to analyze the problem. However, using weighted residual methods creates an economical way in solution time and there is no need for grid generation difficulties. After attaining the dimensionless governing equations and solving them by MOM and LSM, the precision of results is tested by comparing with numerical solutions, and a reasonable accuracy is demonstrated. It can be drawn from the results that increasing the M, NR and Pe causes a decrease in temperature profile, but with rise of β the dimensionless temperature enhances.

Polyethylene composite with boron and tungsten additives for mixed radiation shielding

Mixed neutron and gamma radiations are common in many nuclear applications. Several materials can be combined to obtain a composite material that is better for mixed radiation than the individual component materials. The aim of this paper is to investigate the shielding effectiveness of a polyethylene (PE)-based composite with boron and tungsten additives. Several compositions are tested to shield against a 252Cf fission neutron source using an attenuation experiment. The composite is also manufactured using the melt-mixing method of component raw materials. Comparisons are made between the different compositions and the experimental results. Results suggest that the PE composite with 16%wt boron and 16%wt tungsten show the best mixed radiation attenuation as compared to pure PE, PE composite with 25%wt boron, and PE composite with 25%wt tungsten.

Measurement of the energy spectrum of laser-accelerated protons using FNTD: Development of an easy and quick method for energy spectrometry

This paper reports the derivation of energies of proton beams accelerated by an intense laser using a fluorescent nuclear track detector (FNTD), which is Al2O3 single crystal doped with C and Mg. Using the FNTD, we acquire 3D images of incoming tracks easily, consecutively and rapidly and we can follow the fluorescence intensity of the proton tracks towards their terminals. By counting the number of proton tracks that disappeared at a certain depth, we determine the range of the tracks. Then, we evaluate energies of incoming protons from the evaluated range. The maximum energy of accelerated proton is 3.3 MeV. The results obtained from FNTD measurements are in good agreement with those obtained from the relationship between the incident energy and the distance calculated from the spatial distribution of the magnetic field. The FNTD provides the energy spectrum quickly after the laser shot within few hours, much faster than conventional nuclear track detectors such as CR-39 plastic and nuclear emulsion detectors, which require several days due to the chemical treatments needed. The FNTD is a promising detector for the diagnosis of beams accelerated by an intense laser, which generates a complex mixed radiation field.

A comparison of small-batch clustering and charge-comparison methods for n/[formula omitted] discrimination using a liquid scintillation detector

In this study, a novel neutron and γ-ray (n/γ) discrimination method based on a small-batch clustering algorithm has been developed to improve the discrimination performance of an EJ-301 liquid scintillator detector. The Principal Component Analysis (PCA) of the particle waveform shows that the main feature distribution of the original signal presents an approximate ellipse, which prompts us to adopt a clustering algorithm based on Gaussian Mixture Model (GMM). The classification ability of the small-batch clustering for discriminating n/γ pulse waveforms is verified by a mixed radiation field from a 252Cf isotope source, and then compared with the discrimination results of the charge comparison (CC) method. The results show that the proposed method based on the small-batch clustering provide a higher Figure of Merit (FoM) for n/γ discrimination compared to the CC method, in which FoM increases from 1.26, 1.30, 1.39, and 1.45 for the CC method to 1.35, 1.48, 1.52 and 1.68 respectively for the proposed method during the energy intervals 400–600 keV, 600–800 keV, 800–1000 keV, and >1000 keV for the mixed field of 252Cf. The results infer that the small-batch clustering method can be used as reference for pulse shape discrimination in neutron detection.

Dosimetry of heavy ion exposure to human cells using nanoscopic imaging of double strand break repair protein clusters

The human body is constantly exposed to ionizing radiation of different qualities. Especially the exposure to high-LET (linear energy transfer) particles increases due to new tumor therapy methods using e.g. carbon ions. Furthermore, upon radiation accidents, a mixture of radiation of different quality is adding up to human radiation exposure. Finally, long-term space missions such as the mission to mars pose great challenges to the dose assessment an astronaut was exposed to. Currently, DSB counting using γH2AX foci is used as an exact dosimetric measure for individuals. Due to the size of the γH2AX IRIF of ~ 0.6 µm, it is only possible to count DSB when they are separated by this distance. For high-LET particle exposure, the distance of the DSB is too small to be separated and the dose will be underestimated. In this study, we developed a method where it is possible to count DSB which are separated by a distance of ~ 140 nm. We counted the number of ionizing radiation-induced pDNA-PKcs (DNA-PKcs phosphorylated at T2609) foci (size = 140 nm ± 20 nm) in human HeLa cells using STED super-resolution microscopy that has an intrinsic resolution of 100 nm. Irradiation was performed at the ion microprobe SNAKE using high-LET 20 MeV lithium (LET = 116 keV/µm) and 27 MeV carbon ions (LET = 500 keV/µm). pDNA-PKcs foci label all DSB as proven by counterstaining with 53BP1 after low-LET γ-irradiation where separation of individual DSB is in most cases larger than the 53BP1 gross size of about 0.6 µm. Lithium ions produce (1.5 ± 0.1) IRIF/µm track length, for carbon ions (2.2 ± 0.2) IRIF/µm are counted. These values are enhanced by a factor of 2–3 compared to conventional foci counting of high-LET tracks. Comparison of the measurements to PARTRAC simulation data proof the consistency of results. We used these data to develop a measure for dosimetry of high-LET or mixed particle radiation exposure directly in the biological sample. We show that proper dosimetry for radiation up to a LET of 240 keV/µm is possible.

Characterization of the neutron/[formula omitted]-ray discrimination performance in an EJ-301 liquid scintillator for application to prompt fission neutron spectrum measurements at CSNS

The FIssion Neutron spectrum Detector Array (FINDA) has been designed for measurement of prompt fission neutron spectrum on the Back-n beam line at the China Spallation Neutron Source (CSNS). In order to test the neutron-γ discrimination performance of the EJ301 scintillator that will be used as a detector unit in the FINDA, a comparative study using three conventional digital pulse shape discrimination (PSD) methods has been carried out. An Am–Be source has been used to generate the mixed neutron-γ radiation and the waveform data has been obtained with a fast digitizer. Pulse interpolation, baseline restoration and pulses pile-up rejection have been applied for digital pulse processing. Charge comparison (CC) method and simplified charge comparison(SCC) method show a better capability of neutron-γ discrimination than rise time comparison(RTC) method over the entire energy range. Rise time comparison method needs a very fast digitizer or pulse interpolation to improve the PSD ability. The analysis of neutron-γ discrimination performance of the EJ301 scintillator provides a strong technical support for fast neutron measurement using the FINDA at CSNS.

A Multiple-Relaxation-Time lattice Boltzmann analysis of coupled mixed convection and radiation effect in a tilted two-sided lid-driven enclosure

A 2D Multiple-Relaxation-Time (MRT) lattice Boltzmann (LB) is used to simulate the coupled mixed convection and surface radiation in a square double lid-driven cavity. The parameters governing the problem are the inclination angle (0°≤γ≤180°), the emissivity of the walls (0≤ε≤1), the Reynolds number (Re=100), the Richardson number (0.01≤Ri≤100) and the Grashof number (102≤Gr≤106). The results obtained show significant effects of the Richardson number on the overall structure of the flow and heat transfer characteristics. The radiation effect on the behavior of the fluid within the cavity and the total Nusselt number is considerable, particularly at high values of Richardson number.

Modeling and analysis of unsteady second-grade nanofluid flow subject to mixed convection and thermal radiation

Modeling and analysis of unsteady second-grade nanofluid flow subject to mixed convection and thermal radiation

The number of moths caught by light traps is affected more by microhabitat than the type of UV lamp used in a grassland habitat

We compared the performance of three entomological LED lamps that differed in intensity and wavelength composition by using them to catch 2257 individuals of 161 species and 11 families of nocturnal Lepidoptera in two grassland habitats (dry grassland and orchard meadow). The study was carried out in June and July 2020 in the Jenzig conservation area (Jena, Germany, 50°56´12˝N, 11°37´37˝E). In each habitat, we sampled three microhabitats that were either exposed, moderately sheltered or sheltered. Data were analysed using generalized linear mixed models. A lamp with high radiant flux (LepiLED maxi: 1.34 W mixed radiation) attracted 37% more moths and 5% more species than a lamp with a lower radiant flux (LepiLED mini: 0.55 W mixed radiation). The maxi lamp also attracted 17% more moths and 6% more species than the same lamp with UV radiation only (LepiLED maxi switch UV mode: 0.59 W). However, the maxi lamp only performed significantly better in exposed microhabitats, whereas the UV lamp performed similarly in the sheltered and moderately sheltered sites. The number of individuals caught in the dry grassland habitat was greater than in the orchard meadow (1288 vs. 969), whereas the number of species was similar in both habitats (120 vs. 128). Higher numbers of individuals were caught in the moderately sheltered sites than in the sheltered and exposed sites (935 vs. 773 vs. 549). The same trend was seen in the number of species (119 vs. 113 vs. 110). The communities of moths caught by traps with different lamps were similar. We conclude that light-trapping is a robust method that delivers comparable results even when different lamps are used. The use of several weak lamps is more efficient and results in larger catches than the use of a single strong lamp.

Mixed convection and surface radiation in a ventilated cavity containing two heat-generating solid bodies

This work aims to numerically study the mixed laminar convection and surface radiation in a square air-ventilated cavity (Pr=0.71). Inside this cavity, two square bodies are placed at the same height and generate the same amount of heat. This model can be applied to cooling electronic components. The air enters the cavity from an inlet port at the bottom of the left vertical wall and exits in the outlet port at the top of the other vertical wall. The left wall of the cavity is maintained at a constant temperature TC, while the other walls are assumed to be adiabatic. The Finite Volume Method (FVM) and the SIMPLE algorithm are used to discretize and solve the governing equations. The effect of Rayleigh and Reynolds numbers and surface emissivity on streamlines, isotherms, maximum temperature, and convective and radiative Nusselt numbers are discussed. The obtained results indicate that the maximum temperature decreases with increasing the Reynolds number. It also observed that the surface radiation has more effect for low values of Re. For engineering purposes, correlations have been developed that give the maximum temperatures for ε=0or1, and different ranges of Reynolds number.

IMMERSED BOUNDARY METHODS FOR THERMOFLUIDS PROBLEMS

We review the progress in the development and application of immersed boundary (IB) methods to thermofluids problems achieved in the last three decades. The implementation of different heat transfer boundary conditions, ranging from Dirichlet, Neumann, and Robin to conjugate heat transfer, are discussed for continuous as well as discrete forcing immersed boundary methods. We review several key studies that developed and employed IB methods with stationary boundaries for a variety of heat transfer scenarios such as forced convection, natural or mixed convection, radiation, and combustion. The computational challenges associated with the approaches employed for thermofluids problems with moving boundaries are discussed in detail. These include problems with rigid bodies that move under the influence of fluid dynamic forces as well as flow-induced deformation of compliant bodies. We conclude the article by briefly discussing the implementation of immersed boundary methods in two emerging areas: bioheat transfer and high-speed compressible flows.

Optimal Cooling in a Cavity with Combined Mixed Convection-Surface Radiation Using the Lbm

Optimal Cooling in a Cavity with Combined Mixed Convection-Surface Radiation Using the Lbm

Stray radiation produced in FLASH electron beams characterized by the MiniPIX Timepix3 Flex detector

This work aims to characterize ultra-high dose rate pulses (UHDpulse) electron beams using the hybrid semiconductor pixel detector. The Timepix3 (TPX3) ASIC chip was used to measure the composition, spatial, time, and spectral characteristics of the secondary radiation fields from pulsed 15–23 MeV electron beams. The challenge is to develop a single compact detector that could extract spectrometric and dosimetric information on such high flux short-pulsed fields. For secondary beam measurements, PMMA plates of 1 and 8 cm thickness were placed in front of the electron beam, with a pulse duration of 3.5 µs. Timepix3 detectors with silicon sensors of 100 and 500 µm thickness were placed on a shifting stage allowing for data acquisition at various lateral positions to the beam axis. The use of the detector in FLEXI configuration enables suitable measurements in-situ and minimal self-shielding. Preliminary results highlight both the technique and the detector’s ability to measure individual UHDpulses of electron beams delivered in short pulses. In addition, the use of the two signal chains per-pixel enables the estimation of particle flux and the scattered dose rates (DRs) at various distances from the beam core, in mixed radiation fields.