Облучение ионами аргона Cr/4H-SiC-фотоприемников

The results of the effect of irradiation with Ar ions on the structural, electrophysical and optical characteristics of the ultraviolet Cr/4H-SiC photodetectors in the spectral range of 200−400 nm are presented. After a single irradiation with 53MeV Ar ions with a fluence of 1 · 1010 cm−2, the quantum efficiency of the photodetectors practically remained at the level of the initial samples due to the "gettering effect“ of simple radiation defects by cluster formations. The observed effect promoted a decrease in the number of simple radiation defects of the vacancy type, an increase in the lifetime of current carriers, and, as a consequence, unchanged values of the photoconductivity of Cr/4H-SiC photodetectors. After repeated irradiation of the photodetectors with Ar ions with a total fluence of 2 · 1010 cm−2, the decay of clusters was observed, the formation of a significant number of simple defect centers, which led to a decrease in the lifetime of current carriers and, as a consequence, to a decrease in photoconductivity of Cr/4H-SiC photodetectors.

Crosslinking Multilayer Graphene by Gas Cluster Ion Bombardment

In this paper, we demonstrate a new, highly efficient method of crosslinking multilayer graphene, and create nanopores in it by its irradiation with low-energy argon cluster ions. Irradiation was performed by argon cluster ions with an acceleration energy E ≈ 30 keV, and total fluence of argon cluster ions ranging from 1 × 109 to 1 × 1014 ions/cm2. The results of the bombardment were observed by the direct examination of traces of argon-cluster penetration in multilayer graphene, using high-resolution transmission electron microscopy. Further image processing revealed an average pore diameter of approximately 3 nm, with the predominant size corresponding to 2 nm. We anticipate that a controlled cross-linking process in multilayer graphene can be achieved by appropriately varying irradiation energy, dose, and type of clusters. We believe that this method is very promising for modulating the properties of multilayer graphene, and opens new possibilities for creating three-dimensional nanomaterials.

An induced annealing technique for SiPMs neutron radiation damage

The use of Silicon Photo-Multipliers (SiPMs) has become popular in the design of High Energy Physics experimental apparatus with a growing interest for their application in detector area where a significant amount of non-ionising dose is delivered. For these devices, the main effect caused by the neutron fluence is a linear increase of the leakage current. In this paper, we present a technique that provides a partial recovery of the neutron damage on SiPMs by means of an Electrical Induced Annealing. Tests were performed, at the temperature of 20°C, on a sample of three SiPM arrays (2×3) of 6 mm2 cells with 50 μm pixel sizes: two from Hamamatsu and one from SensL. These SiPMs have been exposed to neutrons generated by the Elbe Positron Source facility (Dresden), up to a total fluence of 8 × 1011 n1 MeV-eq/cm2. Our techniques allowed to reduced the leakage current of a factor ranging between 15-20 depending on the overbias used and the SiPM vendor. Because, during the process the SiPM current can reach O(100 mA), the sensors need to be operated in a condition that provides thermal dissipation. Indeed, caution must be used when applying this kind of procedures on the SiPMs, because it may damage permanently the devices themself.

“At-Home” Photobiomodulation: A New Approach for Bell’s Palsy Treatment

Objective. This report is the first one to describe the possibility to use “self‐administered” photobiomodulation (PBM) for Bell’s palsy (BP) treatment. Background. BP is a peripheral disorder of the facial nerve causing sudden paralysis of unilateral facial muscles, and PBM has been successfully suggested for its treatment without any side effect. This is the first case report where a laser device was successfully used at home by the patient herself to treat BP opening new perspectives on the therapy of this disease. Methods. This report describes the “at-home PBM” treatment performed on a 15-year-old girl who presented BP consisting of acute pain on the right side of her face, difficulty in biting and dripping saliva from the right side of her lips. The treatment was performed twice a day by cutaneous applications, each of 15 minutes (total fluence 48 J/cm2) in an area corresponding to the parotid gland by a device emitting at 808 nm at 250 mW output power. Results. Two weeks after PBM treatment, performed at home twice a day by the patient herself without any kind of pharmacological therapy, the complete disappearing of the disease was noticed with no side effects. Conclusion. With the limitations due to a single case report and with the need of further clinical trials to confirm it, “at-home PBM” seems to represent a good and safe approach to the treatment of BP.

Evaluation of neutron spectra and dose equivalent from a Varian 2100C/D Medical Linear Accelerator: Monte Carlo simulation and a literature review

In this study was carried out a review according to experimental and Monte Carlo studies in the literature on the neutron production from 18 MV, Varian 2100C/D linac. The effects of these neutrons were investigated on the total fluence, the energy spectra, and the dose equivalent. These factors were calculated as a function of depth and the radiation field size by simulation of linac head using of MCNPX2.6.0 code. The neutron strength was found equal to 1.23 × 1012 nGy−1.The results showed that with increasing the field size from 5 × 5 to 40 × 40 cm2, the neutron fluence and dose equivalent in the water phantom rose to the maximum value for 25 × 25 cm2field (3.05 × 107 ncm−2Gy−1and 3.14 mSvGy−1respectively) and then decreased with increasing the field size. According to the results, the magnetite-steel, ordinary, and limonite-steel concrete walls significantly increased the neutron dose equivalent for about 27.4%, 17.2%, and 13.5%, respectively.

Femtosecond Double-Pulse Laser Ablation and Deposition of Co-Doped ZnS Thin Films

Nanostructured thin films of Co-doped zinc sulfide were synthesized through femtosecond pulsed laser deposition. The scheme involved ablation of physically mixed Co and ZnS with pairs of ultrashort pulses separated in time in the 0–300 ps range. In situ monitorization of the deposition process was carried out through a simultaneous reflectivity measurement. The crystallinity of generated nanoparticles and the inclusion of Co in the ZnS lattice is demonstrated by transmission electron microscopy and energy dispersive X-ray microanalysis (TEM-EDX) characterization. Surface morphology, Raman response, and photoluminescence of the films have also been assessed. The role of interpulse temporal separation is most visible in the thickness of the films obtained at the same total fluence, with much thicker films deposited with short delays than with individual uncoupled pulses. The proportion of Co in the synthesized doped ZnS nanoparticles is found to be substantially lower than the original proportion, and practically independent on interpulse delay.

Vascular Effects of Photodynamic Therapy with Curcumin in a Chorioallantoic Membrane Model

Photodynamic Therapy (PDT) is a treatment that requires light, a photosensitizing agent, and molecular oxygen. The photosensitizer is activated by light and it interacts with the oxygen that is present in the cellular microenvironment. The molecular oxygen is transformed into singlet oxygen, which is highly reactive and responsible for the cell death. Therefore, PS is an important element for the therapy happens, including its concentration. Curcumin is a natural photosensitizer and it has demonstrated its anti-inflammatory and anti-oxidant effects that inhibit several signal transduction pathways. PDT vascular effects of curcumin at concentrations varying from 0.1 to 10 mM/cm2 and topical administration were investigated in a chick Chorioallantoic Membrane (CAM) model. The irradiation was performed at 450 nm, irradiance of 50 mW/cm2 during 10 min, delivering a total fluence of 30 J/cm2. The vascular effect was followed after the application of curcumin, with images being obtained each 30 min in the first 3 h, 12 h, and 24 h. Those images were qualitatively and quantitatively analyzed with a MatLAB®. Curcumin was expected to exhibit a vascular effect due to its angio-inhibitory effect. Using curcumin as photosensitizer, PDT induced a higher and faster vascular effect when compared to the use of this compound alone.

Электронная микроскопия и элементный состав приповерхностного слоя кристаллов LiF, облученных электронами

Electron microscopy and optical vibrational spectroscopy techniques have been used to study Li nanoparticles formed on the cleaved surface of lithium fluoride (LiF) crystals irradiated by 4-MeV electron beam to a total fluence of 5 × 10^16 cm^–2. It is suggested that ionization accompanying this intense irradiation leads to radiolysis of the target and removal of fluorine from interblock boundaries, where lithium cations are collected and mutually oriented to form microwires. This functional surface may be of practical interest.

Ablation of Copper Metal Films by Femtosecond Laser Multipulse Irradiation

Ablation of copper using multipulse femtosecond laser irradiation with an 800 nm wavelength and 120-fs pulse duration is investigated theoretically. A two-temperature model, which includes dynamic optical and thermal-physical properties, is considered. The numerical results of the material thermal response obtained by varying the pulse number, the separation times between pulses and laser fluences are presented. Our results show that the increasing of pulse number with a separation time less than the thermal relaxation time can dramatically enhance the lattice temperature without a noticeable increase in ablation depth. Therefore, we suggest that the vaporization rate can be augmented in comparison to the melting rate during the same single-phase explosion at the same total fluence where a fast heat accumulation effect plays an important role for cleaner ablation during micromachining.