Angular Goos-Hanchen shift in subwavelength gratings enhanced by surface plasmon resonance

The angular Goos-Hanchen shift dependence on the subwavelength grating parameters and the incident Gaussian beam width is investigated theoretically. High sensitivity of the angular Goos-Hanchen shift to the incident angle of a light beam near the surface plasmon resonance is demonstrated. Splitting of the reflected beam into two angularly separated beams is shown for strongly focused beam incident at the surface plasmon resonance angle.

A Publicly Available Dataset of Out-of-Field Dose Profiles of a 6 MV Linear Accelerator

An increase in radiotherapy-induced secondary malignancies has led to recent developments in analytical modelling of out-of-field dose. These models must be validated against measurements, but currently available datasets are outdated or limited in scope. This study aimed to address these shortcomings by producing a large dataset of out-of-field dose profiles measured with modern equipment. A novel method was developed with the intention of allowing physicists in all clinics to perform these measurements themselves using commonly available dosimetry equipment. A standard 3D scanning water tank was used to collect 36 extended profiles. Each profile was measured in two sections, with the inner section measured with the beam directly incident on the tank, and the outer section with the beam incident on a water-equivalent phantom abutted next to the tank. The two sections were then stitched using a novel feature-matching approach. The profiles were compared against linac commissioning data and manually inspected for discontinuities in the overlap region. The dataset is presented as a publicly accessible comma separated variable file containing off-axis ratios at a range of off-axis distances. This dataset may be applied to the development and validation of analytical models of out-of-field dose. Additionally, it may be used to inform dose estimates to radiosensitive implants and anatomy. Physicists are encouraged to perform these out-of-field measurements in their own clinics and share their results with the community.

Experimental Study and Analysis of Light Scattering Patterns of Bragg Fibers Fabricated in PECVD

Light scattering patterns are commonly used in industry to assess fiber quality. In this work, scattering patterns of Bragg fibers are studied. Optical fibers are coated with alternating layers of Silicon Nitride and Silica using Plasma Enhanced Chemical Vapor Deposition. A laser beam incident perpendicular to the fiber axis scatters off creating patterns distinct from that of uncoated fibers which exhibit continuous front lobe. Effect of variation in layer properties, polarization, wavelength and fiber symmetry is observed in the patterns. Anomalous suppression and enhancement in angular scattering pattern is explained through a scattering angle diagram. Features in the pattern are mapped to reflectance of the Bragg stack and it is found that a stopband creates the anomalous features in the scattering.

Radiation Doses to Patients Undergoing Osteosynthesis Procedures

Fractures of limbs are most frequent causes of orthopaedic interventions. Especially the older people are exposed to these because of motion disorders and osteoporosis. Most of orthopaedic surgery interventions are performed under X-rays control to achieve an optimal settings the anatomical details and also some artificial implants, if such are necessary. Because if that, X-ray units are common equipment in operational theatre where orthopaedic procedures are performed. As a rule they are mobile C-arm units, which are easy available in any time when are necessary. A consequence of every usage of X-rays an exposure to patient but also to operational medical team [1-3]. They are a number of factors affecting both the patient and staff irradiation. There are three categories: patient dependent, equipment dependent and procedure dependent factors. Patient dependent factors include: body thickness in the beam, complexity of the anatomic structure. Equipment dependent factors include: setting of dose rates in pulsed fluoro- and continuous fluoro mode, last image hold, acquisition, and virtual collimation. The main procedure related factors are: number of radiographic frames per run, collimation, fluoroscopic and radiographic acquisition modes, fluoroscopy time, wedge filter, magnification, distance of patient to image receptor (image intensifier or flat panel detector), distance between X-ray tube and patient, and tube angulations. Very important is also the experience of the operator. In case of patient, this is especially important for the procedures when the primary beam can cover the part of the trunk. Such situation has place in the procedure of osteosynthesis the femoral bone, reconstruction of head of femur and also osteosynthesis the humeral bone. Despite a relatively short time of real exposures, doses to patients undergoing these procedures can achieve quite high values: the entrance skin air kerma (here named the “dose”) over 80 mGy was also recorded. Additionally, in practice the primary X-ray beam incident on the same area patient’ body making a higher risk of radiation detriments. The paper presents collection of doses recorded for patients undergoing the procedures of osteosynthesis the femoral bone and the humeral bone during last moths in the big university clinic.

On the Calibration of the Cherenkov Detector of Galactic and Solar Cosmic Protons with Energies of 600 MeV and More

This article discusses a possible approach to creating a calibration technique for the Galactic and Solar Cosmic Proton Cherenkov Detector. The method is based on the Monte Carlo simulation of proton and electron transfer and their generation of Cherenkov photons in the polymethylmethacrylate radiator. It is shown that, under certain conditions, the device calibration with electrons of 9,38 MeV energy is equivalent to the calibration with a 600 MeV proton beam incident laterally on the detector.

Study of aluminum nitride films deposited on silicon for fabrication of MEMs devices

In this work, aluminum nitride (AlN) thin films deposited on the silicon (100) by RF magnetron-sputtering were analyzed. Nitrogen and argon plasmas were used in a vacuum system technique, being possible to obtain films oriented to the (oo2) crystallographic direction analyzed by X-ray diffraction (XRD) technique. Scanning electronic microscopy (SEM) was used to obtain the chemical composition (% at.) of AlN thin films. SEM analyses were accomplished to verify the images of the AlN films. Raman spectroscopy was used to obtain the Raman displacement as a function of the light intensity of the beam incident on the AlN films. Therefore, it was possible to reach the peaks of laser radiation absorption (λ = 514 nm) during Raman scattering. Ellipsometry was required to obtain: the roughness (Rz), optical gap (E04), and films thickness. Optical properties of the films depend on the temperature during the deposition. COMSOL software was required to simulate the performance of MEMS device, operating in the match circuit on a few ten of MHz resonance frequency.

The BDX-MINI detector for Light Dark Matter search at JLab

This paper describes the design and performance of a compact detector, BDX-MINI, that incorporates all features of a concept that optimized the detection of light dark matter in the MeV-GeV mass range produced by electrons in a beam dump. It represents a reduced version of the future BDX experiment expected to run at JLAB. BDX-MINI was exposed to penetrating particles produced by a 2.176 GeV electron beam incident on the beam dump of Hall A at Jefferson Lab. The detector consists of 30.5 kg of PbWO$$_4$$ 4 crystals with sufficient material following the beam dump to eliminate all known particles except neutrinos. The crystals are read out using silicon photomultipliers. Completely surrounding the detector are a passive layer of tungsten and two active scintillator veto systems, which are also read out using silicon photomultipliers. The design was validated and the performance of the robust detector was shown to be stable during a six month period during which the detector was operated with minimal access.

Исследование прохождения электронов с энергией 10 keV через керамический макроканал

The paper presents the results of experimental studies of the passage of electrons through a ceramic macrocapillary with energy of 10 keV in the position when the axis of the channel is parallel to the axis of the incident beam. Measurements were made of the current and energy spectrum of electrons passing through the channel, depending on the value of the current of the beam incident into it and the irradiation time of the channel. The change in the transmission of electrons through the sample as a function of time after the formation of a conductive carbon deposit on the inner surface of both ends of the channel is demonstrated.