Electron Irradiation Dose Research Articles

Multi-characterization of electron-induced defects in highly oriented pyrolytic graphite

Engineering the properties of materials through defects is at the forefront of research in Materials Science. Here, we investigate the defects produced on highly oriented pyrolytic graphite (HOPG) samples irradiated with 25 keV electrons at different doses. Our samples are characterized using micro-Raman spectroscopy, small angle X-ray scattering and atomic force microscopy measurements. We assign the D mode appearance in Raman spectra to defect-like features, which induce distortions in the electronic density of HOPG after electron irradiation. These defect-like structures are interpreted in terms of a phenomenological model previously proposed by other authors. Furthermore, magnetic measurements allow to follow the changes in the magnetization of electron-irradiated HOPG. Our results show a slight increment in coercivity in irradiated samples as well as a large remanence and saturation enhancement in the sample with higher electron irradiation dose. These novel results hint that a threshold dose needs to be overcome in order to observe a magnetic response in HOPG with electron-induced defects.

Evaluation of the Effect of Different Doses of Fast Electron Irradiation on the Flavoring Compounds and Storage Life of Pink Garlic (Allium sativum L.)

Evaluation of the Effect of Different Doses of Fast Electron Irradiation on the Flavoring Compounds and Storage Life of Pink Garlic (Allium sativum L.)

Studies on functional properties of PCL films modified by electron radiation and TAIC additive

Investigation of the effect of electron radiation and triallyl isocyanurate (TAIC) on the functional properties of poly(ε-caprolactone) (PCL) films was the aim of the present paper. The mechanical properties from static tensile tests, resistance to strain at elevated temperatures, permeability of oxygen and water vapor, shrinkage, luminous transmittance, haze and surface free energy were determined. It was found that irradiation of PCL containing TAIC induces larger and more distinct changes in the film properties with regard to the irradiation of PCL with no TAIC. This fact results from formation of a crosslinked structure, in which TAIC participates in linking of PCL macromolecules. The extent of observed changes essentially depends on the magnitude of the electron radiation dose. It was also found that films obtained exhibit a two-phase structure (crosslinked and non-crosslinked) in the case of samples with TAIC, and structural changes associated with elongation of macromolecules, formation of branched structures or polymer degradation in the case of samples with no this compound.

Dermatopathology effects of simulated solar particle event radiation exposure in the porcine model

The space environment exposes astronauts to risks of acute and chronic exposure to ionizing radiation. Of particular concern is possible exposure to ionizing radiation from a solar particle event (SPE). During an SPE, magnetic disturbances in specific regions of the Sun result in the release of intense bursts of ionizing radiation, primarily consisting of protons that have a highly variable energy spectrum. Thus, SPE events can lead to significant total body radiation exposures to astronauts in space vehicles and especially while performing extravehicular activities. Simulated energy profiles suggest that SPE radiation exposures are likely to be highest in the skin. In the current report, we have used our established miniature pig model system to evaluate the skin toxicity of simulated SPE radiation exposures that closely resemble the energy and fluence profile of the September, 1989 SPE using either conventional radiation (electrons) or proton simulated SPE radiation. Exposure of animals to electron or proton radiation led to dose-dependent increases in epidermal pigmentation, the presence of necrotic keratinocytes at the dermal-epidermal boundary and pigment incontinence, manifested by the presence of melanophages in the derm is upon histological examination. We also observed epidermal hyperplasia and a reduction in vascular density at 30 days following exposure to electron or proton simulated SPE radiation. These results suggest that the doses of electron or proton simulated SPE radiation results in significant skin toxicity that is quantitatively and qualitatively similar. Radiation-induced skin damage is often one of the first clinical signs of both acute and non-acute radiation injury where infection may occur, if not treated. In this report, histopathology analyses of acute radiation-induced skin injury are discussed.

Thermoluminescence glow curves and deconvoluted glow peaks of Ge doped flat fibers at ultra-high doses of electron radiation

The behavior of Ge doped silica, SiO2 flat fibers (FF) irradiated with 2.5 MeV electron radiation at ultra-high dose (UHD) range, up to 1 MGy, has been investigated. The analyzed glow curves measured by the usage of the WinREMS software revealed that peak height and glow curve maximum temperature are highly dependent on the dose. The shape of the glow curves is constant with increasing dose. The supralinearity of all glow peaks increases to its f(D)(max), which occurs around 50 kGy. No saturation occurs at f(D)(max) and further increases in dose, up to 1 MGy, exhibits a significant decrease in f(D). The glow peaks 2 (230 degrees C) and 4 (290 degrees C), deconvoluted by the usage of WinGCF software, are the first-order kinetic peaks and can be used as the main dosimetric peaks for high-dose measurements between 1 and 50 kGy in an industrial environment. (C) 2015 Elsevier Ltd. All rights reserved.

Photoluminescence, optical band gap and surface wettability of some polymeric track detectors modified by electron beam

In the present study, modifications have been performed on two polymeric track detectors (PTDs), CR-39 and Makrofol. The samples were irradiated with 1.5MeV electron beam at different doses ranging from 0 to 500kGy. Changes in photoluminescence (PL) and ultraviolet–visible (UV–vis) spectrophotometry as well as surface properties have been carried out for all PTD samples. The PL spectra indicate noticeable decrease of the integrated intensity for both types of irradiated PTDs with the increase of electron beam doses. This may be due to the creation of defects in the irradiated PTDs polymers. UV–vis spectra reveal that the optical absorption was shifted towards higher wavelength region after irradiation with electron beam. The optical band gap energy and Urbach's energy are decreased with increasing electron beam doses. Contact angle measurements show that the wettability and surface free energy are increased for irradiated samples with increasing electron irradiation doses. The change in roughness is also investigated.

Plasmonic ‘top-hat’ nano-star arrays by electron beam lithography

Lithography techniques play an important role in the fabrication of nanoscale functional devices. In electron beam lithography (EBL) the optimum dose of electron irradiation is a critical parameter. In this paper, we first identify suitable EBL fabrication parameters by writing patterns with different sizes, periods and electron radiation doses. After finding suitable fabrication parameters, we show how five-pointed gold nanostructures with electric field-enhancing ‘top hats’ can be fabricated using EBL. Reflectance data of these arrays is measured in order to assess their potential applications in biosensing arrays.

Effects of Electron Irradiation on the Dielectric Behavior of Langmuir-Blodgett Terpolymer Films

The dielectric response of the Langmuir-Blodgett poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) terpolymer films with various electron irradiation doses was investigated. The dielectric data were analyzed with Vogel-Fulcher law, confirming the relaxor behavior of irradiated samples. Besides, after fitting the data to an empirical law it was proved that the diffuseness of phase transition increased with increasing irradiation dose. Both the Curie temperature and the Curie constant, which were derived from fitting the data to the Curie-Weiss law, were used to calculate a local order parameter within a spin-glass model. It was found that sharper temperature dependence of the local order parameter corresponds to less diffused phase transition.

Optimal electron irradiation as a tool for functionalization of MoS2: Theoretical and experimental investigation

We demonstrate the utility of electron irradiation as a tool to enhance device functionality of graphene-analogous MoS2. With the help of first-principles based calculations, vacancy-induced changes of various electronic properties are shown to be a combined result of crystal-field modification and spin-orbital coupling. A comparative theoretical study of various possible vacancy configurations both in bulk and monolayer MoS2 and related changes in their respective band-structures help us to explain plausible irradiation induced effects. Experimentally, various structural forms of MoS2 in bulk, few layered flakes, and nanocrystals are observed to exhibit important modification of their magnetic, transport, and vibrational properties, following low doses of electron irradiation. While irradiated single crystals and nanocrystals show an enhanced magnetization, transport properties of few-layered devices show a significant increase in their conductivity, which can be very useful for fabrication of electronic devices. Our theoretical calculations reveal that this increase in n-type conductivity and magnetization can be correlated with the presence of sulfur and molybdenum vacancies.

Analysis of electron beam-induced effect on electrical switching properties of glass chalcogenide GeTe thin films through Raman spectroscopy

The electrical switching behavior of amorphous GeTe thin films deposited by thermal evaporation technique and exposed to different doses of electron irradiation has been investigated. All the glasses subjected to electron irradiation below 8 kGy have been found to exhibit memory-type electrical switching behavior whereas irradiation at 8 kGy led to electrical breakdown of the device. It has been observed that the threshold switching value decreases initially and then rises again with increasing doses which may be due to structural rearrangement upon irradiation. Raman study has been performed to get greater insight on the irradiation-induced structural modification in the sample. The study exhibited remarkable change in the relative intensity, along with significant band shift with increasing irradiation dose which is in consistent with threshold field for switching.

Ensuring Uniformity of Measurements of Absorbed Doses of Intensive Photon and Electron Radiation in Radiation Technologies

Ensuring reliability and traceability of the unit of absorbed dose of intense photon and electron radiation, used in radiation technologies in industry, is based on the creation of a system of sample measures and methods of transmission with minimal loss of dimensional accuracy of the unit of absorbed dose from the sample tools to working dosimeters and is a necessary basis of yield growth, of increase of labour productivity and the introduction of innovative products. The measuring capabilities of the State primary special standard of power unit of absorbed dose of intensity photon, electron and beta radiation for radiation technologies and of the standards of the absorbed dose of photon and electron radiation, used for radiation monitoring of radiation pro- cesses.

Dissolution of a silver film in silicon glasses under electron bombardment

It is shown that the under the action of an electron beam with electron energy E > 10 keV and electron irradiation dose Q ≥ 20 mQ/cm2 on silicate glasses coated with a silver film 80–100 nm in thickness, the silver film is dissolved partially or completely. The main mechanisms inducing this effect are the formation of a negative space charge under the glass surface, field emission of positive silver ions from the field, and migration of silver ions to the space charge region.

Adjuvant single-fraction radiotherapy is safe and effective for intractable keloids

The aim of this study was to assess the feasibility and efficacy of high-dose, single-fraction electron beam radiotherapy for therapy-resistant keloids. Before 2010, intractable keloids were treated at our institution with post-operative irradiation of 6–15 Gy in 3–5 fractionations. For convenience and cost effectiveness, we have changed our treatment protocol to high-dose single-fraction radiotherapy. A total of 12 patients with 16 keloid lesions were treated from January 2010 to January 2013 in our department. A 10-Gy dose of electron irradiation was given within 72 h of the surgical excision. The mean follow-up period was 20 months. Treatments were well tolerated, and there was no recurrence in any of the patients. Severe adverse effects were not observed. Surgical excision of the keloid, followed by immediate, single-fraction, high-dose radiotherapy, is both safe and effective in preventing recurrence of therapy-resistant keloids.

Electrical and elastic properties of an array of carbon nanotubes after irradiation by high-energy electrons

The effect of the irradiation of arrays of annealed and unannealed multiwalled carbon nanotubes (CNTs) by electrons with an energy of 21 MeV and a dose of 2.2 × 1017 el/cm2 on their electrical conductivity, thermal electromotive force, and elasticity coefficient is studied. It is established that the irradiation of annealed nanotubes considerably decreases (by nearly a factor of two) their electrical conductivity and coefficient of elasticity in the material pressing direction and increases their thermal electromotive force by nearly 1.5 times. The effect of the same dose of electron irradiation on an array of unannealed CNTs also leads to an appreciable decrease in its coefficient of elasticity, but favors a considerable increase in the electrical conductivity and thermal electromotive force of the material. The observed effects are discussed in relation to the specifics of the formation of radiation defects in CNTs and their interaction with primary defects in unannealed specimens.

Fabrication of carbon nanomembranes by helium ion beam lithography.

The irradiation-induced cross-linking of aromatic self-assembled monolayers (SAMs) is a universal method for the fabrication of ultrathin carbon nanomembranes (CNMs). Here we demonstrate the cross-linking of aromatic SAMs due to exposure to helium ions. The distinction of cross-linked from non-cross-linked regions in the SAM was facilitated by transferring the irradiated SAM to a new substrate, which allowed for an ex situ observation of the cross-linking process by helium ion microscopy (HIM). In this way, three growth regimes of cross-linked areas were identified: formation of nuclei, one-dimensional (1D) and two-dimensional (2D) growth. The evaluation of the corresponding HIM images revealed the dose-dependent coverage, i.e., the relative monolayer area, whose density of cross-links surpassed a certain threshold value, as a function of the exposure dose. A complete cross-linking of aromatic SAMs by He+ ion irradiation requires an exposure dose of about 850 µC/cm2, which is roughly 60 times smaller than the corresponding electron irradiation dose. Most likely, this is due to the energy distribution of secondary electrons shifted to lower energies, which results in a more efficient dissociative electron attachment (DEA) process.

Electron-irradiation induced changes in structural and magnetic properties of Fe and Co based metallic glasses

Electron-irradiation induced changes in structural and, magnetic properties of Co57.6Fe14.4Si4.8B19.2Nb4, Fe72Si4.8B19.2Nb4 and, Co72Si4.8B19.2Nb4 metallic glasses were studied using magnetic hysteresis and, synchrotron X-ray diffraction measurements. Results reveal composition dependent changes of magnetic properties in electron irradiated metallic glasses. A low electron irradiation dose (15kGy) enhances saturation magnetization (up to 62%) in Fe-based alloy (Fe72Si4.8B19.2Nb4). Synchrotron XRD measurements reveal that electron irradiation transforms the amorphous matrix to a more ordered phase, accountable for changes in magnetic properties.

A NEW MOBILE ELECTRON ACCELERATOR FOR INTRA OPERATIVE ELECTRON RADIATION THERAPY

A demonstrator of a new, highly mobile, robotized linear electron accelerator for Intra Operative Electron Radiation Therapy (IOERT) is under construction at National Centre for Nuclear Studies. In an IOERT treatment, a high dose of electron radiation is delivered in a single fraction directly to an exposed location after tumor ablation during oncological surgery. Due to the fact that the tumor can be located anywhere in the body, a high maneuverability of the accelerator and its adaptability to anatomical conditions are required. Moreover, since the treatment is usually executed in an unshielded operation room, the radiation protection issues are of principal importance. To assure safety of the patient and medical personnel, the therapeutic head is designed to constrain the radiation to the volume of the tumor lodge while minimizing leakage and stray radiation. For these reasons, construction of accelerators for IOERT differs considerably from the construction of linear electron accelerators for external beam radiation therapy. This paper presents some challenges and solutions in construction of the accelerator and in particular its therapeutic head with beam forming system.

Optical properties and laser damage performance of SiO2 irradiated by high-power pulsed electron beam

A 60 kW electron beam is used to study the microstructure and optical property evolutions as well as laser induced damage threshold of fused silica after irradiation at room temperature. Optical microscopic results indicate that cracks appear at the surface of SiO2 after electron beam irradiation, owing to the thermal effect, and that the crack density and size increase with increasing radiation dose. The morphology of the surface cracks is analyzed by using atomic force microscope and the width of crack is about 1 μm. In addition, there are a large number of debris particles with sizes of 0.1-1 μm on the surface. From the optical absorption spectrum of each of all samples, a weak absorption peak at 394 nm is observed and the absorbance increases at the beginning then decreases with increasing electron-radiation dose. Before and after irradiation, three absorption bands at 460 nm, 496 nm and 520 nm are clearly observed and their intensities first increase and then decrease, which is consistent with the results of absorption spectra. The effect of electron dose on the laser induced damage threshold (LIDT) at 355 nm is investigated and the results indicate that the LIDT decreases with increasing dose. At the lower electron doses, the color centers are responsible for the decrease of LIDT. However, at the higher electron doses, the decrease of LIDT is due to the light modulation and absorption induced by microscale cracks and debris particles at the surface of irradiated fused silica.

Microcathodoluminescence spectra evolution for planar and nanopillar multiquantum-well GaN-based structures as a function of electron irradiation dose

Effects of low energy electron beam irradiation (LEEBI) of planar and nanopillar InGaN/GaN multiquantum well light emitting diode structures are discussed. The bands observed in microcathodoluminescence (MCL) spectra were attributed to recombination involving two types of InGaN quantum dots with lower (2.92 eV MCL band) and higher (2.75 eV) indium concentration. During the LEEBI treatment, the intensity of both MCL lines first decreased, presumably due to the introduction of radiation defects, then, after the dose of 0.2 C/cm2 increased, reached a maximum and then again decreased. At the same time, the peak energy showed a red shift at low irradiation doses and a blue shift at high doses. The results are explained by an interplay between the increasing density of nonradiative recombination defects and quantum dots during irradiation. The difference between the nanopillar and planar structures is attributed to a stronger impact of surface defects in nanopillars.

PLASMA CHARACTERISTICS IN SQUARE PULSE ARC DISCHARGE OF PLASMA CATHODE ELECTRON SOURCE DEVICE

Plasma parameters in Plasma Cathode Electron Source Device (PCESD) are very important things because they will determine the eficiency of its electron extraction. Square pulse mode of PCESD’s arc discharge plasma current can be obtained by using Pulse Forming Network (PFN) circuits which is called Arc Discharge Power Supply (ADPS). The square pulse mode is necessity to simplify in electron irradiation dose calculation. ADPS is connected with Hollow Anode Chamber (HAC) which is placed inside of PCESD to produce arc discharge plasma. The value of arc discharge plasma current is the main key to determine plasma parameters that can be measured by using Rogowski coil. The value of the arc discharge plasma current is IADPS = 206.30 A with pulse width  = 80 μs. Whereas the plasma parameters values inside of the HAC are: the electron plasma density ne = (16.85  1019) m-3, electron plasma temperature Te = 2.609 eV, electron plasma frequency fe = 116.74 GHz, and Debye length λD = 9.958 µm respectively.