Radiative Acceleration Research Articles

Study of Light Nuclei Activation in Human Blood During High-Energy Linear Accelerator (Linac) Radiation Therapy

Study of Light Nuclei Activation in Human Blood During High-Energy Linear Accelerator (Linac) Radiation Therapy

Radiative Acceleration of Dense Circumstellar Material in Interacting Supernovae

Early-time light curves/spectra of some hydrogen-rich supernovae (SNe) provide solid evidence of the existence of confined, dense circumstellar matter (CSM) surrounding dying massive stars. We numerically and analytically study the radiative acceleration of CSM in such systems, where the radiation is mainly powered by the interaction between the SN ejecta and the CSM. We find that the acceleration of the unshocked dense CSM ahead of the shock is larger for massive and compact CSM, with velocities reaching up to ∼103 km s−1 for a CSM of order 0.1 M ⊙ confined within ∼1015 cm. We show that the dependence of the acceleration on the CSM density helps us explain the diversity of the CSM velocity inferred from the early spectra of some Type II SNe. For explosions in even denser CSM, radiative acceleration can affect the dissipation of strong collisionless shocks formed after the shock breakout, which would affect early nonthermal emission expected from particle acceleration.

Larmor Temperature, Casimir Dynamics, and Planck’s Law

Classical radiation from a single relativistically accelerating electron is investigated where the temperature characterizing the system highlights the dependence on acceleration. In the context of the dynamic Casimir effect with Planck-distributed photons and thermal black hole evaporation, we demonstrate analytic consistency between the ideas of constant acceleration and equilibrium thermal radiation. For ultra-relativistic speeds, we demonstrate a long-lasting constant peel acceleration and constant power emission, which is consistent with the idea of balanced equilibrium of Planck-distributed particle radiation.

Adiabatic bunch compression in storage rings from self wakes generated in Cherenkov waveguides

Equilibrium bunch lengths typical to modern day light sources of tens of picoseconds limit the spectral reach of superradiant approaches for exploring materials and biological samples. In particular, generation of terahertz radiation seems appealing for pump-probe experiments.Taking advantage of self-wakes generated by carefully chosen structure one can control the bunch length and shape the bunch profile to increase significantly the high-frequency spectral components. Numerical analysis indicates the presence of self-consistent steady states that can be obtained with passive corrugated or dielectric structures. This approach has potential applications for generating superradiant terahertz radiation and pulse shaping in circular accelerators.

Bubble structure evolution and electron injection controlled by optical cycles in wakefields

The evolution of bubble structure and electron injection in laser wakefield acceleration with different optical cycles is investigated through three-dimensional particle-in-cell simulations. Under fixed transverse and longitudinal ponderomotive force, the effect of optical cycles on the evolution of bubble structure and electron injection is studied by changing the laser wavelength. For a multi-cycle laser, electron acceleration is dominated by the ponderomotive force that produces symmetrical bubble and continuous injection. As the optical cycles decrease, the dominant effect of the electron acceleration can transition from the ponderomotive force to the carrier wave, and the carrier envelope phase shift can cause transverse oscillation of the bubble and periodic electron injection in the direction of laser polarization. The criterion for the dominant acceleration mechanism and the dependence of transition distance on the optical cycles and pulse width are obtained. The results are beneficial for manipulating electron acceleration and betatron radiation generation.

Radiotherapy Infrastructure Shielding Calculations: software development for shielding calculations in a linear accelerator radiotherapy room.

This work aimed to develop and validate software that calculates the shielding thickness required for a radiotherapy room with a linear accelerator utilising geometric and dosimetric data. The software "Radiotherapy Infrastructure Shielding Calculations" (RISC) was developed using MATLAB programming. It does not require the installation of the MATLAB platform, and the user only needs to download and install the application, which displays a graphical user interface (GUI). The GUI includes empty cells to insert numerical values for several parameters to calculate the proper shielding thickness. The GUI comprises two main interfaces, one for the primary and one for the secondary barrier calculation. The interface of the primary barrier is divided into four tabs: (a) primary radiation, (b) patient scattered and leakage radiation, (c) IMRT techniques and (d) the shielding cost calculations. The interface of the secondary barrier includes three tabs: (a) patient scattered and leakage radiation, (b) IMRT techniques and (c) the shielding cost calculations. Each tab consists of two sections: one for input and one for output of the necessary data. The RISC is based on the methods and formulae of the NCRP 151 and calculates the primary and secondary barrier thickness for ordinary concrete with a density of 2.35g/cm3 and the cost for a radiotherapy room with a linear accelerator that performs conventional or IMRT techniques. Calculations can be performed for photon energies of 4, 6, 10, 15, 18, 20, 25 and 30 MV of a dual-energy linear accelerator, while instantaneous dose rate (IDR) calculations are also performed. The RISC has been validated using all comparative examples of NCRP 151 and the calculations from shielding reports of the Varian IX linear accelerator at Methodist Hospital of Willowbrook and Elekta Infinity at the University Hospital of Patras. The RISC is accompanied by two text files: (a) "Terminology," extensively describing all parameters, and (b) "User's Manual," providing useful instructions to the user. The RISC is user-friendly, simple, fast and precise, providing accurate shielding calculations and quickly and easily reproducing different shielding scenarios for a radiotherapy room with a linear accelerator. Additionally, it could be used during the educational process of shielding calculations by graduate students or trainee medical physicists. As a future work, the RISC will be updated with new features such as skyshine radiation, door shielding, and other types of machines and shielding materials.

Entropy optimization and response surface methodology of blood hybrid nanofluid flow through composite stenosis artery with magnetized nanoparticles (Au-Ta) for drug delivery application

Entropy creation by a blood-hybrid nanofluid flow with gold-tantalum nanoparticles in a tilted cylindrical artery with composite stenosis under the influence of Joule heating, body acceleration, and thermal radiation is the focus of this research. Using the Sisko fluid model, the non-Newtonian behaviour of blood is investigated. The finite difference (FD) approach is used to solve the equations of motion and entropy for a system subject to certain constraints. The optimal heat transfer rate with respect to radiation, Hartmann number, and nanoparticle volume fraction is calculated using a response surface technique and sensitivity analysis. The impacts of significant parameters such as Hartmann number, angle parameter, nanoparticle volume fraction, body acceleration amplitude, radiation, and Reynolds number on the velocity, temperature, entropy generation, flow rate, shear stress of wall, and heat transfer rate are exhibited via the graphs and tables. Present results disclose that the flow rate profile increase by improving the Womersley number and the opposite nature is noticed in nanoparticle volume fraction. The total entropy generation reduces by improving radiation. The Hartmann number expose a positive sensitivity for all level of nanoparticle volume fraction. The sensitivity analysis revealed that the radiation and nanoparticle volume fraction showed a negative sensitivity for all magnetic field levels. It is seen that the presence of hybrid nanoparticles in the bloodstream leads to a more substantial reduction in the axial velocity of blood compared to Sisko blood. An increase in the volume fraction results in a noticeable decrease in the volumetric flow rate in the axial direction, while higher values of infinite shear rate viscosity lead to a significant reduction in the magnitude of the blood flow pattern. The blood temperature exhibits a linear increase with respect to the volume fraction of hybrid nanoparticles. Specifically, utilizing a hybrid nanofluid with a volume fraction of 3% leads to a 2.01316% higher temperature compared to the base fluid (blood). Similarly, a 5% volume fraction corresponds to a temperature increase of 3.45093%.

Shielding design aspects of SR in 3 GeV ILSF

Iranian Light Source Facility (ILSF) is an under-construction synchrotron radiation accelerator consisting of a 150 MeV linac, a booster synchrotron operating from 150 MeV to 3 GeV, and a 3 GeV storage ring that stores a maximum of 400 mA current of electrons. As the stored beam circulates, a fraction of the beam is lost due to interactions with gas molecules, interactions among beam particles, and orbital bending, which produce radiation. The bulk shielding calculation for the ILSF and the input parameters used for this analysis are discussed in this paper. The potential of skyshine neutrons to cause radiation hazards is investigated as well. Moreover, the design and shielding simulation using the FLUKA Monte Carlo code is presented for the linac beam stop and primary and scattered gas bremsstrahlung for the first optics enclosure of the ILSF spectro microscopy beamline. Our designed radiation shielding system guarantees that the annual dose in all areas around the ILSF machine does not exceed the dose limit of 1 mSv.

IGNITION OF WOODEN BIOMASS PARTICLES UNDER MICROWAVE EXPOSURE AT HIGH-TEMPERATURE RADIATION-CONVECTIVE HEATING

Link for citation: Syrodoy S.V., Malyshev D.Yu., Kostoreva Zh.A., Kostoreva A.A., Omarov A.A. Ignition of wooden biomass particles under microwave exposure at high-temperature radiation-convective heating. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 5, рр.159-167. In Rus. The relevance. Despite the active development of technologies for the production of electrical energy by means of wind power generators and solar batteries, by 2100, most of the energy will still be generated at thermal power plants that burn fossil fuels. As a rule, thermal power plants use coal as fuel (about 40 %). However, it should be noted that during the combustion of coal in the furnaces of steam and hot water boilers, toxic oxides of sulfur and nitrogen are intensively formed. In this regard, many scientists of the world working in the field of energy are working to create new innovative technologies for the eco- and energy-efficient production of heat and electricity. The latter include technologies for burning woody biomass in the furnaces of steam and hot water boilers of thermal power plants. The use of woody biomass can significantly reduce the environmental impact of thermal power plants on the atmosphere. However, no technology has yet been developed to burn wood with high energy efficiency. The latter is due to the high moisture saturation of woody biomass in its initial state. The main aim: experimental determination of the main stages and identification of a complex of physicochemical processes occurring together during the ignition of woody biomass particles under microwave exposure under high-temperature radiation-convective heating. Object: dry and moisture-saturated wood of two types (pine and cedar). The relative humidity of the wood from which the particles were made (with a characteristic size of 4 mm) varied from 6 (relatively dry biomass) to 42 % (moisture-saturated wood). Method. To establish the main characteristics of wood particle ignition under microwave exposure under high-temperature radiation-convective heating, a special experimental stand was developed, representing a reaction tube with heat-insulated radio-transparent walls through which a high-temperature oxidizer (air oxygen) was blown. The wood particle was mounted on the axis of the pipe so as to fall into the focus of the emitter. All processes were recorded by a high-speed video camera. Results. The paper introduces the results of experimental studies of ignition of dry and wet particles of woody biomass in the environment of air heated to high temperatures under conditions of radiation-convective and radiation-convective microwave heating. A significant influence of the type of wood on the ignition delay times (tign) was established. Rather significant effect of heating conditions on ignition is also shown, since microwave exposure leads to an acceleration of ignition of woody biomass particles. It was shown that during the ignition of wet wood particles, the effect of exposure to microwave radiation (acceleration of ignition) is more significant compared to ignition of dry wood particles. It was also found that the moisture content (φ) of woody biomass significantly affects the ignition delay times (increase in φ leads to growth in the tign value). The regularities established in the conducted experiments illustrate the prospects of using woody biomass (including moisture-saturated) in thermal power engineering as the main fuel.

Neutron spectrometry and dosimetry using a multi-shell Single Sphere Neutron Spectrometer with thermo-luminescent and optically stimulated luminescent detectors

A portable neutron spectrometer with concentric multi-shell moderating assembly and TL, OSL detectors has been validated with standard neutron reference fields to generate the neutron spectra and estimate the ambient dose equivalents, H*(10). Further, the system has been used in the mixed neutron–gamma radiation fields at accelerator facility. The neutron fluence and the ambient dose equivalent estimates were verified using the standard reference neutron fields, viz. 241Am-Be, 252Cf, D-T neutron sources. The system was then employed in the accelerator radiation environment to measure the neutron spectral yield from the interactions of 15 and 20 MeV protons with a thick natural Ta target. The results were compared with those obtained from FLUKA simulations. A conventional neutron dose equivalent meter was also used to verify the ambient dose equivalent estimated from the spectrometric measurements. The reproducibility of the neutron spectra and dose values were found to be satisfactory, thereby encouraging the implementation of the portable single sphere neutron spectrometer in complex radiation environment around particle accelerators. Present studies demonstrate the measurements with the in-house built spectrometer for neutron energies up to 20 MeV.

Nonthermal acceleration radiation of atoms near a black hole in presence of dark energy

We investigate how dark energy affects atom-field interaction. To this end, we consider acceleration radiation of a freely falling atom close to a Schwarzschild black hole (BH) in the presence of dark energy characterized by a positive cosmological constant $\mathrm{\ensuremath{\Lambda}}$. The resulting spacetime is endowed with a BH and a cosmological (or de Sitter) horizon. Our consideration is a nonextremal ($1+1$)-dimensional geometry with horizons far apart, giving rise to a flat Minkowski-like region in between the two horizons. Assuming a scalar (spin-0) field in a Boulware-like vacuum state, and by using a basic quantum optics approach, we numerically achieve excitation probabilities for the atom to detect a photon as it falls toward the BH horizon. It turns out that the nature of the emitted radiation deeply drives its origin from the magnitude of $\mathrm{\ensuremath{\Lambda}}$. In particular, radiation emission is enhanced due to dilation of the BH horizon by dark energy. Also, we report an oscillatory nonthermal spectrum in the presence of $\mathrm{\ensuremath{\Lambda}}$, and these oscillations, in a varying degree, also depend on BH mass and atomic excitation frequency. We conjecture that such a hoedown may be a natural consequence of a constrained motion due to the bifurcate Killing horizon of the given spacetime. The situation is akin to the Parikh-Wilzcek tunneling approach to Hawking radiation where the presence of extra contributions to the Boltzmann factor deforms the thermality of flux. It apparently hints at field satisfying a modified energy-momentum dispersion relation within classical regime of general relativity arising as an effective low energy consequence of an underlying quantum gravity theory. Our findings may signal new ways of conceiving the subtleties surrounding the physics of dark energy.

Analysis of Radiation Dose Distribution in Nasopharyngeal and Organ Cancer Cases at Risk with Linear Accelerator Radiotherapy 6 MV Photon Energy Using the IMRT Technique at Prof. Hospital. Dr. I. G. N. G. Ngoerah

This study aims to determine the distribution of radiation doses on PTV and OAR radioteraphy planning in RSUP. Prof. Dr. I.G.N.G Ngoerah, Bali, Indonesia does no exceed a predetermined limit. The research metode used is the value of Homogenity Index (H), Conformity Index (CI), and the maximum value of radiation ose to the Organ At Risk (OAR), amely the right eye lens, left eye lens, brainstem, optic chiasma, and spinal cord. These data are compared with the provisions of ICRU report 83 and the maximum dose reference value for OAR. Using data from 30 nasopharyngeal cancer patients with a total radiation dose of 7000 cGy. Obtained a value for HI of 0.1214 with a t-test result of 0.459> 0.05 which means it is not significant. While the value for CI is 0.9850 with nonparametric statistical test results of 0.285> 0.05 which means it is not significant. The maximum dose value for the right eye lens is 772.7 cGy with a t-test result of 0.779> 0.05 which means it is not significant. For the maximum value of the dose in the lens of the left eye of 771.0 cGy with a t test result of 0.791> 0.05 which means it is not significant. For the maximum value of the dose in the brain stem of 5178.1 cGy with nonparametric test results of 0.686> 0.05 which means not significant. The maximum dose value at the optic chiasma is 4,837.2 cGy with a nonparametric test result of 0.225>0.05 which means it is not significant. For the maximum value of the dose in the spinal cord of 4,663.3 cGy with a t test result of 0.958> 0.05 which means it is not significant.

Obtaining and Studying Materials for Suppressing External Vibrations at Critical Nodes of Synchrotron Radiation Accelerators

Obtaining and Studying Materials for Suppressing External Vibrations at Critical Nodes of Synchrotron Radiation Accelerators

Obtaining and researching materials for suppressing external vibrations in the responsible nodes of synchrotron radiation accelerators

We show that the introduction of powders-modifiers into a polymer matrix in an amount of less than 1 wt % leads to an increase in the strength characteristics and resistance to cyclical loading with a force of 50–1600 N and a frequency of 2 Hz of more than 3 million cycles.

Opacities and Atomic Diffusion

Opacity is a fundamental quantity for stellar modeling, and it plays an essential role throughout the life of stars. After gravity drives the collapse of interstellar matter into a protostar, the opacity determines how this matter is structured around the stellar core. The opacity explains how the radiation field interacts with the matter and how a major part of the energy flows through the star. It results from all the microscopic interactions of photons with atoms. Part of the momentum exchange between photons and atoms gives rise to radiative accelerations (specific to each type of atom), which are strongly involved in a second-order process: atomic diffusion. Although this process is a slow one, it can have a significant impact on stellar structure and chemical composition measurements. In this review, we discuss the way opacities are presently computed and used in numerical codes. Atomic diffusion is described, and the current status of the consideration of this process is presented.

Helical tomotherapy and two types of volumetric modulated arc therapy: dosimetric and clinical comparison for several cancer sites

Radiotherapy accelerators have undergone continuous technological developments. We investigated the differences between Radixact™ and VMAT treatment plans. Sixty patients were included in this study. Dosimetric comparison between the Radixact™ and VMAT plans was performed for six cancer sites: whole-brain, head and neck, lymphoma, lung, prostate, and rectum. The VMAT plans were generated with two Elekta linear accelerators (Synergy®and Versa HD™). The planning target volume (PTV) coverage, organs-at-risk dose constraints, and four dosimetric indexes were considered. The deliverability of the plans was assessed using quality assurance (gamma index evaluation) measurements; clinical judgment was included in the assessment. The mean AAPM TG218 (3%-2mm, global normalization) gamma index valueswere 99.4%, 97.8%, and 96.6% forRadixact™,Versa HD™, andSynergy®, respectively. Radixact™ performed better than Versa HD™ in terms of dosimetric indexes, hippocampi D100%, spinal cord Dmax, rectum V38.4 Gy, bladder V30 Gy,and V40 Gy. Versa HD™saved more of the (lungs-PTV) V5 Gyand (lungs-PTV) Dmean,heartDmean, breasts V4 Gy, and bowel V45 Gy. RegardingSynergy®, the head and neckRadixact™plan saved more of the parotid gland, oral cavity, and supraglottic larynx. From a clinical point of view, for the head and neck, prostate, and rectal sites, theRadixact™ and Versa HD™ plans were similar;Radixact™ plans were preferable for the head and neck and rectum toSynergy®plans. The quality of linac plans has improved, and differences with tomotherapy have decreased. However, tomotherapy continues to be an essential add-on in multi-machine departments.

Atmospheric Density Inversion Based on Swarm-C Satellite Accelerometer

We used the Swarm-C accelerometer data to invert the orbital atmospheric density in this study. First, the Swarm-C satellite mission data were obtained from the ESA’s public data platform, and preliminary data error correction was performed. This paper refers to the calibration method of GRACE-A satellite accelerometer data. It adds linear temperature correction on the original basis. Moreover, this study’s accelerometer data correction results were compared with the data correction results published by the ESA. In order to explore the influence of light radiation on the accelerometer, we established a geometric model of Swarm-C to simulate the physical shape of the satellite surface. The light radiation pressure model and the shadow area judgment model were established, the change in the light radiation acceleration during the transition process of the satellite from the umbra area to the penumbra area and then to the shadowless area was studied, and the state transition during the transition process was analyzed. Finally, the atmospheric drag coefficient was calculated based on the Sentman model. Atmospheric density inversion calculations were performed using the above data. We show the spatial distribution of atmospheric density at a fixed latitude, testing our results during geomagnetic storms. We compared the density results with existing research data, demonstrating the effectiveness of our approach.

Dose estimation for cone-beam computed tomography in image-guided radiation therapy for pelvic cancer using adult mesh-type reference computational phantoms

The use of cone-beam computed tomography (CBCT) is expanding owing to its installation in linear accelerators for radiation therapy, and the imaging dose induced by this system has become the center of attention. Here, the dose to patients caused by the CBCT imager was investigated. Organ doses and effective doses for male and female mesh-type reference computational phantoms (MRCPs) and pelvis CBCT mode, routinely used for pelvic irradiation, were estimated using the Particle and Heavy Ion Transport Code System. The simulation results were confirmed based on the point-dose measurements. The estimated organ doses for male MRCPs with/without raised arms and for female MRCPs with/without raised arms were 0.00286-35.6mGy, 0.00286-35.1mGy, 0.00933-39.5mGy, and 0.00931-39.0mGy, respectively. The anticipated effective doses for male MRCPs with/without raised arms and female MRCPs with/without raised arms irradiated by pelvis CBCT mode were 4.25mSv, 4.16mSv, 7.66mSv, and 7.48mSv, respectively. The results of this study will be useful for patients who undergo image-guided radiotherapy with CBCT. However, because this study only covered one type of cancer with one type of imager, and image quality was not considered, more studies should be conducted to estimate the radiation dose from imaging devices in radiation therapy.

A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets

Context. Blazars, a class of active galaxies whose jets are relativistic and collimated flows of plasma directed along the line of sight, are prone to a slew of magnetohydrodynamic (MHD) instabilities. These jets show characteristic multi-wavelength and multi-timescale variabilities. Aims. We aim to study the interplay of radiation and particle acceleration processes in regulating the multi-band emission and variability signatures from blazars. In particular, the goal is to decipher the impact of shocks arising due to MHD instabilities in driving the long-term variable emission signatures from blazars. Methods. To this end, we performed relativistic MHD (RMHD) simulations of a representative section of a blazar jet. The jet was evolved using a hybrid Eulerian-Lagrangian framework to account for radiative losses due to synchrotron process as well as particle acceleration due to shocks. Additionally, we incorporated and validated radiative losses taking into consideration the external Compton (EC) process that is relevant for blazars. We further compared the effects of different radiation mechanisms through numerical simulation of 2D slab jet as a validation test. Finally, we carried out a parametric study to quantify the effect of magnetic fields and external radiation field characteristics by performing 3D simulations of a plasma column. The synthetic light curves and spectral energy distribution (SEDs) were analyzed to qualitatively understand the impact of instability driven shocks. Results. We observed that shocks produced with the evolution of instabilities give rise to flaring signatures in the high-energy band. The impact of such shocks is also evident from the instantaneous flattening of the synchrotron component of the SEDs. At later stages, we observed the transition in X-ray emission from the synchrotron process to that dominated by EC. The inclusion of the EC process also gives rise to γ-ray emission and shows signatures of mild Compton dominance that is typically seen in low-synchrotron peaked blazars.

High Energy CT applications for cultural heritage

The application of computed tomography (CT) in the field of cultural heritage is no new concept and widely applied mainly by usage of medical or industrial CT systems. Nevertheless, CT setups based on conventional X-ray tubes with energy spectra up to 600 kV face several limitations considering the overall maximum specimen dimension due to the available foot print of the CT system and therefore scanning volume (approx. < 1 m x 1 m x 1m), object weight (load limit of the manipulation system, usually < 100 kg) and material properties, e.g. highly absorbing metal components. To overcome these boundaries High Energy CT systems with a linear accelerator (linac) radiation source with up to 9 MeV spectra prove to be a successful tool to push the limits of conventional CT and to provide a comprehensive extension for a new class of cultural heritage objects. In this paper, we demonstrate the beneficial application of high-energy photons for the digitization of historic objects and artifacts, as well as strategies for democratizing access to this still expensive but valuable technology for digital preservation, research and exhibition.