High-energy Radiation Sources Research Articles

Ionizing Radiation for Preparation and Functionalization of Membranes and Their Biomedical and Environmental Applications.

The use of ionizing radiation processing technologies has proven to be one of the most versatile ways to prepare a wide range of membranes with specific tailored functionalities, thus enabling them to be used in a variety of industrial, environmental, and biological applications. The general principle of this clean and environmental friendly technique is the use of various types of commercially available high-energy radiation sources, like 60Co, X-ray, and electron beam to initiate energy-controlled processes of free-radical polymerization or copolymerization, leading to the production of functionalized, flexible, structured membranes or to the incorporation of functional groups within a matrix composed by a low-cost polymer film. The present manuscript describes the state of the art of using ionizing radiation for the preparation and functionalization of polymer-based membranes for biomedical and environmental applications.

Environmentally friendly synthesized and magnetically recoverable designed ferrite photo-catalysts for wastewater treatment applications

Fenton processes are promising wastewater treatment alternatives for bio-recalcitrant compounds. Three different methods (i.e., reverse microemulsion, sol-gel, and combustion) were designed to synthesize environmentally friendly ferrites as magnetically recoverable catalysts to be applied for the decomposition of two pharmaceuticals (ciprofloxacin and carbamazepine) that are frequently detected in water bodies. The catalysts were used in a heterogeneous solar photo-Fenton treatment to save the cost of applying high-energy UV radiation sources, and was performed under a slightly basic pH to avoid metal leaching and adding salts for pH adjustment. All the developed catalysts resulted in the effective treatment of ciprofloxacin and carbamazepine in both synthetic and real domestic wastewater. In particular, the sol-gel synthesized ferrite was more magnetic and more suitable for reuse. The degradation pathways of both compounds were elucidated for this treatment. The degradation of ciprofloxacin involved attacks to the quinolone and piperazine rings. The degradation pathway of carbamazepine involved the formation of hydroxyl carbamazepine and dihydroxy carbamazepine before yielding acridine by hydrogen abstraction, decarboxylation, and amine cleavage, which would be further oxidized.

Cosmic ray transport and radiative processes in nuclei of starburst galaxies

AbstractThe high rate of star formation and supernova explosions of starburst galaxies make them interesting sources of high-energy radiation. Depending on the level of turbulence present in their interstellar medium, the bulk of cosmic rays produced inside starburst galaxies may lose most of their energy before escaping, thereby making these sources behave as calorimeters, at least up to some maximum energy. Contrary to previous studies, here we investigate in detail the conditions under which cosmic ray confinement may be effective for electrons and nuclei and we study the implications of cosmic ray confinement in terms of multifrequency emission from starburst nuclei and production of high-energy neutrinos. The general predictions are then specialized to three cases of active starbursts, namely, M82, NGC 253, and Arp220. Both primary and secondary electrons, as well as electron–positron pairs produced by gamma-ray absorption inside starburst galaxies are taken into account. Electrons and positrons produced as secondary products of hadronic interactions are found to be responsible for most of the emission of leptonic origin. In particular, synchrotron emission of very high energy secondary electrons produces an extended emission of hard X-rays that represents a very interesting signature of hadronic process in starburst galaxies, potentially accessible to current and future observations in the X-ray band. A careful understanding of both the production and absorption of gamma-rays in starburst galaxies is instrumental to the assessment of the role of these astrophysical sources as sources of high-energy astrophysical neutrinos.

Interpolation methods for creating a scatter radiation exposure map

A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source. A well know way for best understanding of radiation scattering and radiation exposure rate during a procedure using ionizing radiation is to map exposure over the space around the source and sample. This map is done measuring exposure in points regularly spaced, it means, measurement will be placed in localization chosen by increasing a regular steps from a starting point, along the x, y and z axes or, in more efficient way, radial and angular coordinates. However, it is not always possible to maintain the accuracy of the steps throughout the entire space, or there will be regions of difficult access where the regularity of the steps will be impaired. In this work we use a high energy radiation source to simulate a common radiography setup and construct its exposure map. The arrangement of the points and the interpolation were used considering polar coordinates. Then with the same data, an interpolation using the Delaunay triangulation was made. The results show the advantages and disadvantages of each other besides the high coherence for the same data. To simulate the impossibility of regular points, the same procedures were performed in the absence of any point and compared. The results show a lower total variation when the map is calculated by triangulation. The computational and graphic treatment was performed with GNU OCTAVE software and its image processing package. The data were acquired from a bunker where a 6MeV betatron was used as a primary source.

Radio emission of the Crab and Crab-like pulsars

The pulsar radio emission is commonly associated with the plasma outflow in the open field line tube; then a pencil beam is emitted along the pulsar magnetic axis. Observations suggest that there is an additional radio emission mechanism specific for pulsars with high magnetic field at the light cylinder. These pulsars are known to be strong sources of non-thermal high energy radiation, which could be attributed to reconnection in the current sheet separating, just beyond the light cylinder, the oppositely directed magnetic fields. Pulsars with the highest magnetic field at the light cylinder (>100 kG) exhibit also radio pulses in phase with the high energy pulses. Moreover, giant radio pulses are observed in these pulsars. I argue that the reconnection process that produces high energy emission could also be responsible for the radio emission. Namely, coalescence of magnetic islands in the sheet produces magnetic perturbations that propagate away in the form of electro-magnetic nano-shots. I estimate the parameters of this emission and show that they are compatible with observations.

The steady growth of the high-energy spectral cut-off in relativistic magnetic reconnection

Magnetic reconnection is invoked as an efficient particle accelerator in a variety of astrophysical sources of non-thermal high-energy radiation. With large-scale two-dimensional particle-in-cell simulations of relativistic reconnection (i.e., with magnetization $\sigma\gg1$) in pair plasmas, we study the long-term evolution of the power-law slope and high-energy cutoff of the spectrum of accelerated particles. We find that the high-energy spectral cutoff does not saturate at $\gamma_{\rm cut}\sim 4\sigma$, as claimed by earlier studies, but it steadily grows with time as long as the reconnection process stays active. At late times, the cutoff scales approximately as $\gamma_{\rm cut}\propto \sqrt{t}$, regardless of the flow magnetization and initial temperature. We show that the particles dominating the high-energy spectral cutoff reside in plasmoids, and in particular in a strongly magnetised ring around the plasmoid core. The growth of their energy is driven by the increase in the local field strength, coupled with the conservation of the first adiabatic invariant. We also find that the power-law slope of the spectrum ($p=-{\rm d}\log N/{\rm d}\log \gamma$) evolves with time. For $\sigma\gtrsim10$, the spectrum is hard at early times ($p\lesssim 2$), but it tends to asymptote to $p\sim 2$; the steepening of the power-law slope allows the spectral cutoff to extend to higher and higher energies, without violating the fixed energy budget of the system. Our results demonstrate that relativistic reconnection is a viable candidate for accelerating the high-energy particles emitting in relativistic astrophysical sources.

Design and construction of a proportional gas flow meter with application in Mössbauer spectroscopy

The design, construction and operation parameters of a gas flow proportional counter are presented in order to implement the integral conversion electron mossbauer spectroscopy technique (ICEMS). The detector works with the support of a multi-channel detection system and a source of highenergy radiation of 57Co. A constant gas flow of a mixture of 5% CH4 in He was used as a multiplier gas, which increased the signal intensity, and protected the sample´s surface of electric shocks. An internal filter for low energy X-rays was considered during the design to achieve a lower background noise and optimize the volume of gas consumed. With this built-in ICEMS detector it is feasible to characterize efficiently the magnetic properties and oxidation states (hyperfine interactions) of both bulk materials and thin films. The calibration of the device was performed by using an iron sample synthesized by powder metallurgy. It was successfully identified the presence of a distinctive sextet of the α-Fe phase with a hyperfine field of 330 kOe and an isomer shift of 0.312 mm / s. The great usefulness of the equipment was verified by solving the magnetic hyperfine interactions of the Mossbauer spectrum associated to a commercial stainless-steel washer.

High-energy astrophysics and the search for sources of gravitational waves

The dawn of the gravitational-wave (GW) era has sparked a greatly renewed interest into possible links between sources of high-energy radiation and GWs. The most luminous high-energy sources-gamma-ray bursts (GRBs)-have long been considered as very likely sources of GWs, particularly from short-duration GRBs, which are thought to originate from the merger of two compact objects such as binary neutron stars and a neutron star-black hole binary. In this paper, we discuss: (i) the high-energy emission from short-duration GRBs; (ii) what other sources of high-energy radiation may be observed from binary mergers; and (iii) how searches for high-energy electromagnetic counterparts to GW events are performed with current space facilities. While current high-energy facilities, such as Swift and Fermi, play a crucial role in the search for electromagnetic counterparts, new space missions will greatly enhance our capabilities for joint observations. We discuss why such facilities, which incorporate new technology that enables very wide-field X-ray imaging, are required if we are to truly exploit the multi-messenger era.This article is part of a discussion meeting issue 'The promises of gravitational-wave astronomy'.

Uncertainty in positioning ion chamber at reference depth for various water phantoms.

Uncertainty in the calibration of high-energy radiation sources is dependent on user and equipment type. We evaluated the uncertainty in the positioning of a cylindrical chamber at a reference depth for reference dosimetry of high-energy photon beams and the resulting uncertainty in the chamber readings for 6- and 10-MV photon beams. The aim was to investigate major contributions to the positioning uncertainty to reduce the uncertainty in calibration for external photon beam radiotherapy. The following phantoms were used: DoseView 1D, WP1D, 1D SCANNER, and QWP-07 as one-dimensional (1D) phantoms for a vertical-beam geometry; GRI-7632 as a phantom for a fixed waterproofing sleeve; and PTW type 41023 and QWP-04 as 1D phantoms for a horizontal-beam geometry. The uncertainties were analyzed as per the Guide to the Expression of Uncertainty in Measurement. The positioning and resultant uncertainties in chamber readings ranged from 0.22 to 0.35mm and 0.12-0.25%, respectively, among the phantoms (using a coverage factor k=1 in both cases). The major contributions to positioning uncertainty are: definition of the origin for phantoms among users for the 1D phantoms for a vertical-beam geometry, water level adjustment among users for the phantom for a fixed waterproofing sleeve, phantom window deformation, and non-water material of the window for the 1D phantoms for a horizontal-beam geometry. The positioning and resultant uncertainties in chamber readings exhibited minor differences among the seven phantoms. The major components of these uncertainties differed among the phantom types investigated.

Composition dependent structural and morphological modifications in nanocrystalline Mn-Zn ferrites induced by high energy γ-irradiation

We report the high energy γ-irradiation induced structural transformations in nanocrystalline Mn1-xZnxFe2O4 (x = 0, 0.25, 0.5, 0.75 and 1) samples synthesized by solution combustion method using a mixture of fuels. All samples were exposed to a gamma radiation dose of 50 kGy. The γ-irradiation decomposes the single phase cubic spinel (Fd-3m) structure of the samples into new stable phases. The pure MnFe2O4 sample transformed to Mn2O3 and Fe1-xO phases whereas the pure ZnFe2O4 sample retained its phase. For the samples with intermediate Zn-content γ-irradiation facilitates the formation of stable α-Fe2O3 and ZnFe2O4 phases, along with amorphous MnO phase. The scanning electron micrographs demonstrate the complete change of the sample morphology with fusion of the particles after γ-irradiation. Our results are important for the understanding of the stability and performance of the devices used in various technological applications near intense high energy radiation sources.

Development and Design Mix of Radiation Shielding Concrete for Gamma-ray Shielding

For the first time in the world the development and design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates has been reported. The developed shielding aggregates are made up of red mud and are basically ceramic materials consisting of shielding phases namely barium silicate (sanbornite), barium iron titanium silicate (bafertisite), barium aluminum silicate, Iron titanium oxide (pseudorutile), barium titanate, barium iron titanium oxide, barium aluminium oxide and magnetite, which are multi elemental, multi phases, multi layered crystal structures and therefore are excellent shielding materials. The design mix calculations for the development of radiation shielding concrete using developed synthetic shielding aggregates were carried out by adopting IS 10262-2009 for grade designation of M-30 concrete. The reference hematite ore concrete and developed concrete, slabs of size 30 cm × 30 cm × 7.2 cm were casted and sucessfully tested both for radiation shielding attenuation properties for gamma rays of factor using 137Cs (of photon energy 662 keV) and 241Am (of photon energy 60 keV) as well as X-rays of 300 kVp and found to posses highly effective shielding properties. For high energy radiation source i.e. 137Cs, the developed novel design mix concrete achieved attenuation factor of 5.8 as compared to 5.1 attenuation factor for hematite ore concrete. Further, the developed optimized design mix concrete have been tested for durability and the corrosion resistant test using standard 3.5% NaCl solution for optimized design mix were also carried out. The developed design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates posses broad application spectrum ranging from construction of nuclear power plants, diagnostic X-ray, CT scanner rooms and storing radioactive waste.

Variation of Tc, lattice parameter and atomic ordering in Nb3Sn platelets irradiated with 12 MeV protons: correlation with the number of induced Frenkel defects

Nb3Sn platelets with thicknesses between 0.12 and 0.20 mm produced by a high isostatic pressure process at 1250 °C were irradiated at 300 K with 12 MeV protons. The effects of irradiation on the lattice parameter a, the atomic order parameter S and the transition temperature Tc were measured as a function of proton fluence. In view of the presence of multiple energy radiation sources in future accelerators, the present proton data are compared with neutron irradiation data from the literature. The fluences for both types of radiation were replaced by the dpa number, the ‘displacements per atom’, calculated using the FLUKA code, which is proportional to the number of radiation induced Frenkel defects. It was found that the variation of both a and S for Nb3Sn after proton and neutron irradiation as a function of dpa fall almost on the same curve, in analogy to the recently reported correlation between Tc and the dpa number. By a simultaneous irradiation of two adjacent thin Nb3Sn platelets, we have shown that this correlation is not only valid for the state of ‘steady energy loss’ (protons traveling through the first platelet) but also for the state of higher damage at the Bragg peak (second platelet). It follows that the number of radiation induced Frenkel defects in the A15 grains, calculated via the dpa number, can be considered as a ‘universal’ parameter, allowing the calculation of the variation of Tc, a and S of Nb3Sn under the effect of multiple high energy radiation sources, as in future superconducting accelerators.

Kinetics of relativistic electrons passing through quasi-periodic fields

We report a novel method for evaluating the energy spectrum of electrons emitting hard X-rays and gamma-rays in undulators and Compton sources. The method takes into account the quantum nature of recoils undergone by the electrons emitting high energy photons. The method is susceptible to evaluate a spectrum of electrons for the whole range of the emission rates per electron-pass through of the driving force, from much less than one emitted photon on average (Compton sources and short undulators) to many emitted photons (long undulators, relatively low-energy electrons). As shown in the former limiting case, the spectrum of electrons reflects the spectrum of emitted radiation whereas it is close to the Gaussian shape in the latter case. Limitation of coherency for the sources of high-energy electromagnetic radiation caused by recoils from emitted photons is also discussed.

The High-Voltage System of Calet Apparatus

CALET (CALorimetric Electron Telescope) is installed on the International Space Station since August 2015, is a mission devoted to measure the intensity of cosmic ray electrons and protons accelerated to near the speed of light. The apparatus is also designed to observe high energy gamma rays, nearby source of high energy radiation and it may even detect signatures of the elusive dark matter.One of the core components of the whole apparatus is the high voltage power supply system. It is based on hundred of independent DC/DC converters providing precise voltage regulation to two sections of CALET detectors.This paper presents the experience gained in the implementation of the CALET HV system: the system design requirements and the technical solutions adopted, the two system sections block schemes and the main characteristics of the DC/DC converters that guarantee the CALET HV system technical performance.

Dose dependent modifications in structural and magnetic properties of γ-irradiated nanocrystalline Mn0.5Zn0.5Fe2O4 ceramics

Different doses of γ-radiation can be used to modify the structural and magnetic properties of a host of materials. The Mn0.5Zn0.5Fe2O4 ceramics samples prepared by the solution combustion route were exposed to different doses of γ-radiation in order to study stability and phase transformations. The creation of defects and building up of strain was observed after medium doses of γ-irradiation (up to 25kGy) into the single phase pristine samples. However, after 50kGy of γ-irradiation the locally generated heat drives atomic diffusion, as indicated by the morphological changes in the sample. Furthermore, the sample decomposed into two new stable crystalline phases, α-Fe2O3 and ZnFe2O4, along with amorphous MnO phase. Besides the structural transformations we have observed the deterioration of magnetic properties at higher doses. Our results are important for understanding the stability and performance of the ferrite based devices used near intense high energy radiation sources.

Characteristics of betatron radiation from direct-laser-accelerated electrons.

Betatron radiation from direct-laser-accelerated electrons is characterized analytically and numerically. It is shown here that the electron dynamics is strongly dependent on a self-similar parameter S(≡n_{e}/n_{c}a_{0}). Both the electron transverse momentum and energy are proportional to the normalized amplitude of laser field (a_{0}) for a fixed value of S. As a result, the total number of radiated photons scales as a_{0}^{2}/sqrt[S] and the energy conversion efficiency of photons from the accelerated electrons scales as a_{0}^{3}/S. The particle-in-cell simulations agree well with the analytical scalings. It is suggested that a tunable high-energy and high-flux radiation source can be achieved by exploiting this regime.

Photoluminescence, radioluminescence, and thermoluminescence in NaMgF3 activated with Ni2+ and Er3+

Photoluminescence (PL) and radioluminescence (RL) has been observed at infrared wavelengths in NaMgF3 doped with Er3+ or Ni2+. The RL contains more emissions than seen in the PL, which is likely to be due to radiation induced excitations to higher energy excited states of the luminescent ion than are accessible during PL. Both luminescent ions have relatively long PL lifetimes and the long wavelength RL emission intensities are independent of absorbed dose history for high doses. This, coupled with the approximate radiological equivalence of NaMgF3 to water are desirable properties for a dosimeter for radiotherapy applications. The Čerenkov component seen for high energy radiation sources can be reduced by monitoring the longer wavelength RL emissions, or by temporal discrimination for pulsed sources. Room temperature glow peaks are seen in the NaMgF3:Er3+ thermally stimulated luminescence emission that imply the RL will be temperature dependent. This is not the case for NaMgF3:Ni2+ where no thermoluminescence is observed, hence Ni2+ is preferred over Er3+ for radiotherapy applications.

Surface Modification of Polycrystalline Diamond Compacts by Carbon Ion Irradiation

Selective modification (e.g. defect creation and amorphization) of diamond surfaces is of interests for functional diamond-based semiconductors and devices. Bombarding the diamond surface with high energy radiation sources such as electron, proton, and neutrons, however, often result in detrimental defects in deep bulk regions under the diamond surface. In this study, we utilized high energy carbon ions of 3 MeV to bombard the polycrystalline diamond compact (PDC) specimen. The resultant microstructure of PDCs was investigated using micro Raman spectroscopy. The results show that the carbon bombardment successfully created point defects and amorphization in a shallow region of ∼500nm deep on the diamond surface. The new method has great potential to allow diamond-based semiconductor devices to be used in numerous applications.

Development of mandibular osteoradionecrosis in rats: Importance of dental extraction.

To develop an animal model of mandibular osteoradionecrosis (ORN) using a high-energy radiation source (as used in human therapeutics) and to assess the role of tooth extraction on ORN development. Ten animals were irradiated with a single 35- or 50-Gy dose. Three weeks later, the second left mandibular molar was extracted from three animals in each group. Nine weeks after irradiation, the animals were euthanized, with an injection of contrast agent in the bloodstream to highlight vascularization. Mandibles were harvested and studied using micro-CT, histology, tartrate-resistant acid phosphatase activity and scanning electron microscopy. This study demonstrates that a single 50-Gy dose associated with molar extraction is necessary for ORN development. In these conditions, absence of healing of the mucosa and bone, dental effects, fibrosis, an increase in osteoclast activity and a decrease in vascularization were observed. We also determined that molar extraction increases the impact of the cellular effects of radiation. The mandibular ORN animal model was validated after 50-Gy irradiation and molar extraction. The results of this study therefore support an animal ORN model and tissue engineering strategies will now be developed to regenerate bone for patients with head and neck cancer.

Oral complications of radiotherapy: approaches to prevention and treatment

The use of high-energy radiation sources covering large areas of head and neck, together with increased chances for clinical recovery leads to increased rates of radiation complications - a variety of changes in the surrounding healthy tissues and organs. One of the most common oral mucosa complications of radiation therapy is radiation mucositis. Its pathogenesis is based on developing erythematous lesions that turn into ulcer defects with a trend of merging to form an increasingly large focuses. After reaching its peak, inflammatory reaction regresses. The incidence of radiation mucositis is over 60% at standard mode radiotherapy and nearly 100% at hyperfractionated radiotherapy. In addition to the pecularities of radiotherapy, the incidence of mucositis also depends on the tumor type, patient’s age, the initial state of the oral cavity, the patient’s nutritional status. Cryotherapy using a helium-neon laser and drugs (pentoxifylline, thalidomide, simvastatin, analgesics, anesthetics) are recommended for treatment. Reducing the procedure time by improving medical technology, using pulsed fluoroscopy instead of constant, using additional protective filters and changing the X-ray beam focus site may significantly reduce the frequency of radiation complications.