Angular Incidence Research Articles

Nuclear Tracks Morphology Study Using Raman Methodology

In this work, a new methodology for rendering profiles of etched nuclear tracks is presented, using confocal micro-Raman spectrometry instrumentation. The precise profile of etched nuclear tracks with normal and/or angular incidence of the particle can be determined in few minutes, with a great visual and numerical resolution, that means a quantitative and qualitative simultaneous chemical and morphology characterization with the Raman technique. The Raman image routine is designed to acquire at each image pixel a complete Raman spectrum. This is a mapping of the functional groups that form the polymeric structure, which may be broken by the damage caused by the incident radiation and/or the etching process.

Perfect electromagnetic absorption using graphene and epsilon-near-zero metamaterials

The ability of graphene/polymer heterostructures to absorb GHz electromagnetic radiation was recently evidenced both theoretically and experimentally [Batrakov et al., Sci. Rep. 4, 7191 (2014) and Lobet et al., Nanotechnology 26, 285702 (2015)]. Maximum absorption was shown to depend solely on refractive indices of incident and emergence media once impedance matching conditions are fulfilled. In this paper, analytical models and numerical simulations are performed for both semi-infinite and finite slab substrate. We evidenced that only three graphene layers separated by a dielectric spacer and an epsilon-near-zero metamaterial as emergence medium allow a perfect absorption for normal incidence. The use of lossless epsilon-near-zero metamaterial prevents radiations to go through the device, because of infinite impedance, and forces them to be totally absorbed in the dissipative medium (graphene). The device is proved to be robust regarding angular incidence up to 45 deg for a semi-infinite epsilon-near-zero metamaterial. The proposed strategy is universal and can be applied to any kind of two-dimensional dissipative materials lying on epsilon-near-zero metamaterial. The proposed absorber does not rely on surface patterning or texturing and hence is more appealing for device applications.

TH‐AB‐201‐07: Filmless Treatment Localization QA for the CyberKnife System

Purpose:Accuray recommends daily evaluation of the treatment localization and delivery systems (TLS/TDS) of the CyberKnife. The vendor‐provided solution is a Winston‐Lutz‐type test that evaluates film shadows from an orthogonal beam pair (known as AQA). Since film‐based techniques are inherently inefficient and potentially inconsistent and uncertain, this study explores a method which provides a comparable test with greater efficiency, consistency, and certainty. This test uses the QAStereoChecker (QASC, Standard Imaging, Inc., Middleton, WI), a high‐resolution flat‐panel detector with coupled fiducial markers for automated alignment. Fiducial tracking is used to achieve high translational and rotational position accuracy.Methods:A plan is generated delivering five circular beams, with varying orientation and angular incidence. Several numeric quantities are calculated for each beam: eccentricity, centroid location, area, major‐axis length, minor‐axis length, and orientation angle. Baseline values were acquired and repeatability of baselines analyzed. Next, errors were induced in the path calibration of the CK, and the test repeated. A correlative study was performed between the induced errors and quantities measured using the QASC. Based on vendor recommendations, this test should be able to detect a TLS/TDS offset of 0.5mm.Results:Centroid shifts correlated well with induced plane‐perpendicular offsets (p < 0.01). Induced vertical shifts correlated best with the absolute average deviation of eccentricities (p < 0.05). The values of these metrics which correlated with the threshold of 0.5mm induced deviation were used as individual pass/fail criteria. These were then used to evaluate induced offsets which shifted the CK in all axes (a clinically‐realistic offset), with a total offset of 0.5mm. This test provided high and specificity and sensitivity.Conclusion:From setup to analysis, this filmless TLS/TDS test requires 4 minutes, as opposed to 15–20 minutes for film‐based methods. The techniques introduced can potentially isolate errors in individual joints of the CK robot.Spectrum Medical Physics, LLC of Greenville, SC has a consulting contract with Standard Imaging of Middleton, WI

On the bimetallic 1D photonic crystals under angular incidence excitation

Ternary layer-based one-dimensional photonic crystal (1D PC) kind of optical filter is discussed that operates in the visible and near-infrared regimes of the electromagnetic spectrum. The 1D PC filter is comprised of bimetallic structure having three periodic nanolayers of gold, flint glass (SiO2), and silver. Dispersion and reflection characteristics of the proposed filter are analyzed by implementing the concept of transfer matrix and taking into account the incidence excitations under different angles. It is found that the structure exhibits behavior similarly to notch, comb, and Fabry–Pérot types of filter. It is expected that such filters would be useful in integrated optic as well as in sensing applications.

Transport in magnetized nanocylindrical topological insulators

In this work we study the surface states of a topological insulator (TI) cylinder with a magnetization in the radial, azimuthal and axial directions. We derive the eigenenergies and eigenstates, and show that a state with a quantum number associated with the orbital angular momentum incident at a junction between a source TI cylinder and a coaxial drain TI cylinder can only be transmitted and reflected into states with the same quantum number. For cylinders magnetized only in the radial direction, this leads to markedly different behavior in the transmission depending on whether the source magnetization is smaller or larger than the drain magnetization. For azimuthal magnetizations, it results in perfect transmission between two cylinders magnetized to different extents in the azimuthal direction. The restriction of transmission and reflection to states with the same quantum number gives rise to a step-like increment in the transmission from an unmagnetized cylinder to one with an axial magnetization as the energy and magnetization are varied.

Single and multilayered materials processing by argon ion beam etching: study of ion angle incidence and defect formation

Ion beam etching (IBE) is a very promising technique in microelectronics because of its capability to etch small patterns with a high resolution and inert materials. In this study, the angular incidence of an argon ion beam on the etch rate and uniformity is discussed in the case of several materials often used in microelectronics. The capability of the IBE technique to etch multilayered stack samples with positive anisotropic profiles was demonstrated on TiNiAu, TiNiCuAu, BST and PZT. Two typical defects involved in IBE processing (fences and not etched pattern foots) due to shadow masking and redeposition effect, are explained and solutions are presented to avoid them. Deep IBE was performed on GaN with an etch depth as high as 10 μm, using a 8 μm thick SiO2 mask. The etching of other mask materials, such as TiN, was investigated in order to improve the selectivity. Using a TiN mask, a selectivity to GaN as high as 5 is reported. Finally, the etch rate enhancement needed for deep etching was studied.

Photon polarization in light-by-light scattering: Finite size effects

We derive a simple expression for the photon helicity and polarisation-flip probabilities in arbitrary background fields, in the low energy regime. Taking the background to model a focused laser beam, we study the impact of pulse shape and collision geometry on the probabilities and on ellipticity signals of vacuum birefringence. We find that models which do not account for pulse duration can overestimate all signals in near head-on collisions by up to an order of magnitude. Taking pulse duration into account, the flip probability becomes relatively insensitive to both angular incidence and the fine details of the pulse structure.

Large-area full-field thickness measurement of glass plates by an optical interferometric system

Thickness uniformity has been a crucial issue for glass plates used in the flat panel display (FPD). However, point-by-point measurement and/or phase-shifting technique must be employed in the current optical interferometric techniques. Therefore, instantaneous full-field thickness measurement cannot be implemented. Besides, the measurement area is limited by the dimensions of optical components employed in the current optical interferometric techniques. In this paper, an optical interferometric system named angular incidence interferometry (AII) was proposed so that large-area full-field thickness measurement can be achieved. By using AII, the full-field continuous phase difference can be determined by using only one interference image. When the thickness at one point of the specimen is known, the full-field thickness distribution can be obtained immediately. Moreover, with the use of only a basic point-expanded laser light and an image acquisition system, no other special optical components are needed in AII. The applicability and feasibility of AII on the measurement of thickness were investigated by a typical commercially available glass plate of 0.7mm nominal thickness.

47.4: Distinguished Paper: Realization of Outstandingly High Efficacy White OLED by Controlling Evanescent Mode and Wide Angular Incident Light

AbstractOptimization of angular light distribution in organic layer and light extraction structure based on high refractive index substrate were investigated. Due to advanced optical design for decreasing waveguide and evanescent modes, white OLED device with outstandingly high efficacy of 133 lm/W at 1,000 cd/m2 was realized.

Changes of Band Gap Structure of 1-D Quasi-Periodic Photonic Crystal at Angular Incidence

The transmission spectra of 1-D quasi-periodic photonic crystal of positive-negative index structure at angular incidence was studied by transfer matrix method. The results show that the photonic band gap structure changes along with different incidence angles, a new photonic band gap corresponding toω/ωpe=1 will appear, whose centric position is invariant with the changes of incidence angle, but the width broadens as the incidence angle increases; likewise, for a Bragg gap, the centric position and width of band gap also change, which provides conditions for achieving complete phase matching for the second harmonic effect.

Measurement of neutron energy spectrum from 241 Am-B source using CR-39 detectors and an in-house image analysis program (autoTRAK_n)

An attempt has been made in the present work to estimate the neutron spectrum of a standard 241 Am-B source using CR-39 solid polymeric track detector and an in-house image analysis program autoTRAK_n. The program works on the principle of greyscale variations in and around the recoil tracks and calculates the track parameters such as diameter, major, minor axes and estimates three dimensional parameters like recoil track depth and angular incidence. It is also capable of counting overlapping tracks without any segregation procedure. In the present study, the standard 241 Am-B neutron spectrum generated from the recoil track parameters with the autoTRAK_n program is compared with the reported values measured using the time of flight method and found to be matching well, mainly at the characteristic peak. The total neutron fluence and dose equivalents are also determined with the program and are compared with the standard source measurements. The results obtained from autoTRAK_n are found to be in close agreement with the standard measurements with less than 5% error for both the parameters. Hence, this methodology can be used as a backup technique for neutron spectrum measurements along with other techniques considering its low cost, small size, easy irradiation, and processing.

Verification of Response of Neutron Monitor for In-Flight Neutron Dosimetry

In this work, we present the results of verification of special neutron monitoring equipment for use in aircrew dosimetry inside aircraft. The equipment was precalibrated with conventional neutron sources in a National Standard Laboratory of the Institute for Radioprotection and Dosimetry (IRD, Brazil) and verified in a Cosmic Energy Reference Field (CERF), a special field from CERN (Centre European de Recherche Nucleaire), a facility that reproduces the shape of neutron field encountered in the atmosphere at aircraft altitudes. The equipment consists of a special neutron probe from Thermo Scientific with response up to 5 GeV neutrons and was verified with respect to ambient dose equivalent rate linearity and angular incidence. The results show the adequacy of the equipment for this type of measurement and the feasibility to use conventional neutron sources to calibrate this specific equipment, in the absence of access to the CERF field.

Quantification of Ge in Si1‐xGex by using low‐energy Cs+ and O2+ ion beams

Several studies have been reported on the quantification of Ge in Si1‐xGex using SIMS with oxygen or cesium primary ions. Most of them were limited to lower Ge concentrations. In this paper, we discussed procedures to quantify Ge content in Si1‐xGex with x ranging from 0.11 to 0.70 by using low‐energy Cs+ and O2+ primary beams. The results showed that at impact energy of 250 eV, the Ge secondary ion yield changed dramatically against the SiGe matrix composition with a Cs+ primary beam, whereas the change was minimal with an O2+ primary beam. As a result, quantification by using the reference signal inside Si substrate became difficult as no linear correlation exists between the Ge intensity and the Ge concentration in the case of Cs+ primary ions. However, the correlation between the ratios of secondary intensities I(Ge)/I(Si) within the SiGe layers and the composition ratio [Ge]/[Si] is monotonic (although nonlinear). Hence, quantification based on the ratios of the secondary ion intensities versus the ratios of the corresponding contents worked for both Cs+ and O2+ primary beams to quantify the Ge content of an unknown SiGe sample. In addition to this, we reported the angular (incidence angles between 0° and 70°) dependence of the sputter yield of SiGe as a function of Cs+ primary ion energy (150–500 eV). Copyright © 2012 John Wiley & Sons, Ltd.

Photonic band effect in single-layers of high refractive index spheres of different compactness

Transmission spectra from single-layers of high dielectric permittivity (ɛ = 7) glass spheres have been measured, in microwave region, for different angular incidences. The same systems have been calculated by Finite-Difference Time-Domain (FDTD) method. The dispersion diagrams of photonic bands in triangular geometries have been obtained for a number of different compactness cases. The experimental and the calculated photonic band structures show a good agreement in all the compactness values studied. They were also compared with the Mie resonances of the isolated spheres. The results indicate that the characteristics of the Mie resonances appear dominant in the photonic band structure as the compactness of the lattice decreases. Dispersion diagrams present several low dispersion photonic bands, independent of incidence-angle, with high Q-values, that could be useful for future applications of the considered structures like filters or solar cells.

Transmission of electrons through a tapered glass capillary

The transmission of high-current electrons through a tapered SiO2 capillary was investigated. The angular distribution and incident energy dependence of transmitted electrons were observed. We found that the transmitted fraction decreases with the incident energy. The transmitted electrons had significant energy loss but could not be focused by the tapered capillary.

COMPARISON OF TWO DIFFERENT TYPES OF LIF:MG,CU,P THERMOLUMINESCENT DOSIMETERS FOR DETECTION OF BETA RAYS (BETA-TLDS) FROM 90SR/90Y, 85KR AND 147PM SOURCES

Targeted radionuclide therapies in nuclear medicine departments increasingly depend on using unsealed beta radiation sources in the labeling of peptides and antibodies. Monitoring doses received by the fingers and hands during these procedures is best accomplished with TLD dosimeters that can be located at the fingertips. The present study examines the response of two TLD dosimeters (MCP-Ns and GR200A) to 90Sr/90Y, 85Kr, and 147Pm. The dosimeters were supplied by two different services, and all irradiations were performed at the PTB Institute in Germany. Each dosimetry service evaluated the dosimeters without knowledge that they had been purposefully irradiated. The accuracy and precision of the dosimeters were evaluated as a function of delivered dose, energy of beta particles and angular incidence. The results are compared to performance measures recommended by the IEC. Both dosimeter types displayed significant energy dependence. Angular dependence was moderate. Accuracy and precision as a function of dose (linearity) differed between the two systems, with the MCP-Ns being noticeably better than the GR200A. The superior precision makes the MCP-Ns much more useful for extremity dose measurements. The differences between these two dosimeter systems reinforce the need to evaluate a dosimeter carefully before using it in the daily work routine.

The Effect of Layout Topology on Single-Event Transient Pulse Quenching in a 65 nm Bulk CMOS Process

Heavy-ion microbeam and broadbeam data are presented for a 65 nm bulk CMOS process showing the existence of pulse quenching at normal and angular incidence for designs where the pMOS transistors are in common n-wells or isolated in separate n-wells. Experimental data and simulations show that pulse quenching is more prevalent in the common n-well design than the separate n-well design, leading to significantly reduced SET pulsewidths and SET cross-section in the common n-well design.

X-ray interferometer with bent gratings: Towards larger fields of view

Recently, a Talbot–Lau interferometer was proposed to achieve phase contrast and dark field imaging in the hard X-rays domain (10–100 keV). This technique attracts much interest since it does not impose strong requirements on the coherence of the radiation while being sensitive to small phase changes of the beam. However, the limited size of the field of view, some centimeters, prevents its use in many applications where large objects have to be investigated. In the following article, the authors investigate a solution to extend the size of the field of view. After introducing the fundamental limitation on the size of the field of view, a Talbot–Lau interferometer with gratings bent on a cylindrical form is proposed and demonstrated in a compact (60 cm-long) configuration. A significant improvement of the performance could be achieved in comparison to the standard geometry. The theoretical limit imposed by the non-perpendicular angular incidence can thus be practically overcome and large fields of view become realistic. The authors envision a significant impact for high resolution phase sensitive imaging and/or industrial systems.

Trackerless ultrasound-integrated bone cement detection using a modular minirobot in revision total hip replacement

Medical robots are superior to freehand manipulation if an accurate, precise, and time-efficient implementation of a preplanned intervention is required. In the first part of this contribution a new modular minirobot for automatic ultrasound-based bone cement detection followed by subsequent cement milling in revision total hip replacement is presented. A minirobot integrated ultrasound module eliminates the need for external position tracking (e.g. by an optical system) as well as patient registration since the scanned contours can be directly provided within the robot's coordinate system. Further, the modular minirobot concept allows kinematics, workspace, and mechanical parameters to be easily adapted to the requirements of related or even new surgical applications. In the experimental part, the impact of ultrasound module integration on the implementation of optimized scanning strategies is investigated and evaluated in a laboratory set-up. As wave mode conversion and refraction artefacts due to angular sound incidence influence the detection accuracy, the transducer alignment can be optimized with respect to the number of degrees of freedom (DOFs) provided by the minirobot. A model-based scanning approach using two degrees of freedom (2DOFs), three degrees of freedom (3DOFs), and four degrees of freedom (4DOFs) respectively is presented. For automated scanning path calculation, a 2DOF distal-proximal prescan has been performed to estimate the principal components of the cement cavity's geometry using either a model-based or a statistical approach. In a cadaver study, the model-based approach consistently outperformed the statistical approach. The 3DOFs and 4DOFs scanning strategies yielded a significantly higher scanning accuracy if compared with the 2DOFs approach whereas the 3DOFs approach represents a trade-off between system complexity and detection accuracy.

Optical bistability at angular incidence in a one-dimensional photonic crystal containing single negative materials

Nonlinear wave propagation is studied theoretically in a one-dimensional photonic band gap structure containing single negative materials. It is found that Kerr nonlinearity is greatly enhanced near the lower edge of a recently explored angular gap for transverse magnetic polarized light. Consequently, optical bistability is achieved at very low values of input intensity in a periodic structure composed of only a few repeating units. The characteristics of optical bistability are affected only slightly with the variation of the incident angle and thickness ratio of the layers. The effect of losses is also found to be relatively insignificant in such a small structure.