Light Guides Research Articles

Simulation and efficiency studies of optical photon transportation and detection with plastic antineutrino detector modules

In this work, the simulation of optical photons is carried out in an antineutrino detector module consisting of a plastic scintillator connected to light guides and photomultipliers on both ends, which is considered to be used for remote reactor monitoring in the field of nuclear safety. Using Monte Carlo (MC) based GEANT4 simulation, numerous parameters influencing the light collection and thereby the energy resolution of the antineutrino detector module are studied: e.g., degrees of scintillator surface roughness, reflector type, and its applying method onto scintillator and light guide surface, the reflectivity of the reflector, light guide geometries and diameter of the photocathode. The impact of each parameter is investigated by looking at the detected spectrum, i.e. the number photoelectrons per depositing energy. In addition, the average light collection efficiency of the detector module and its spatial variation are calculated for each simulation setup. According to the simulation results, it is found that photocathode size, light guide shape, reflectivity of reflecting material and wrapping method show a significant impact on the light collection efficiency while scintillator surface polishing level and the choose of reflector type show relatively less impact. This study demonstrates that these parameters are very important in the design of plastic scintillator included antineutrino detectors to improve the energy resolution efficiency.

Study of light backgrounds from relativistic electrons in air light-guides

The MOLLER experiment proposed at the Thomas Jefferson National Accelerator Facility plans a precision low energy determination of the weak mixing angle via the measurement of the parity-violating asymmetry in the scattering of high energy longitudinally polarized electrons from electrons bound in a liquid hydrogen target (Møller scattering). A relative measure of the scattering rate is planned to be obtained by intercepting the Møller scattered electrons with a circular array of thin fused silica tiles attached to air light guides, which facilitate the transport of Cherenkov photons generated within the tiles to photomultiplier tubes (PMTs). The scattered flux will also pass through the light guides of downstream tiles, generating additional Cherenkov as well as scintillation light and is a potential background. In order to estimate the rate of these backgrounds, a gas-filled tube detector was designed and deployed in an electron beam at the MAMI facility at Johannes Gutenberg University, Mainz, Germany. Described in this paper is the design of a detector to measure separately the scintillation and Cherenkov responses of gas mixtures from relativistic electrons, the results of studies of several gas mixtures with comparisons to simulations, and conclusions about the implications for the design of the MOLLER detector apparatus.

Integrated catheter for simultaneous radio frequency ablation and optoacoustic monitoring of lesion progression

Radio frequency (RF) catheter ablation is commonly used to eliminate dysfunctional cardiac tissue by heating via an alternating current. Clinical outcomes are highly dependent on careful anatomical guidance, electrophysiological mapping, and careful RF power titration during the procedure. Yet, current treatments rely mainly on the expertise of the surgeon to assess lesion formation, causing large variabilities in the success rate. We present an integrated catheter design suitable for simultaneous RF ablation and real-time optoacoustic monitoring of the forming lesion. The catheter design utilizes copper-coated multimode light guides capable of delivering both ablation current and near-infrared pulsed-laser illumination to the target tissue. The generated optoacoustic responses were used to visualize the ablation lesion formation in an ex-vivo bovine heart specimen in 3D. The presented catheter design enables the monitoring of ablation lesions with high spatiotemporal resolution while the overall therapy-monitoring approach remains compatible with commercially available catheter designs.

Guiding Light

As automotive designers try to balance limited cabin space with additional display elements, many are turning to light guides as a solution.

Analytical and regression models of glass rod drawing process

The process of drawing glass rods (light guides) is being studied. The parameters of the process affecting the quality of the light guide have been determined. To solve the problem, mathematical models based on general equations of continuum mechanics are used. The conditions for the stable flow of the drawing process have been found, which are determined by the stability of the motion of the glass mass in the formation zone to small uncontrolled perturbations. The sensitivity of the formation zone to perturbations of the drawing speed and viscosity is estimated. Experimental models of the drawing process, based on the regression analysis methods, have been obtained. These models make it possible to customize a specific production process to obtain light guides of the required quality. They allow one to find the optimum combination of process parameters in the chosen area and to determine the required accuracy of maintaining them at a specified level.

Improving edge crystal identification in flood histograms using triangular shape crystals

This work presents a method to improve the separation of edge crystals in PET block detectors. As an alternative to square-shaped crystal arrays, we used an array of triangular-shaped crystals. This increases the distance between the crystal centres at the detector edges potentially improving the separation of edge crystals. To test this design, we have compared the flood histograms of two 4 × 4 scintillator arrays in both square and triangular configurations. The quality of the flood histogram was quantified using the fraction of events positioned in the correct crystal based on a 2D Gaussian fit of the segmented flood histograms. In the first study, the two crystal arrays were coupled with the SiPM directly using optical grease, and the flood histogram quality for the edge and corner crystals in the triangular-shaped array were much better than that for those crystals in the square-shaped array. The average light collection efficiency for the triangular-shaped array was 5.9% higher than that for the square-shaped array. The average energy resolution for the triangular and square shape array were 11.6% and 13.2% respectively. In the second study, two light guides with thickness 1 mm and 2 mm were used between the crystal arrays and the SiPM. The thicker lightguide degraded the light collection efficiency and energy resolution due to the light loss introduced by the light guide. However, in the 2 mm thick lightguide case, the flood histogram quality for the edge and corner crystals in the square-shaped array were improved due to better separation of those crystals in the flood histogram. Comparing the performance of the two crystal arrays with three different light guides, the triangular-shaped crystal array with no lightguide gave the best performance.

Tomography in Optically Axisymmetric Media

A generalization of the Cormac algorithm for the inversion of the Radon transformation in an optical medium with an axisymmetric index of refraction has been proposed. The distribution of rays is such that only one ray passes through any two points in the circle. A “parallel scanning scheme” of tomography has been considered: a cylindrical object is illuminated by a parallel beam of light, the rays of which are deflected into the cylinder. There is no refraction on the surface of the cylinder. The algorithm assumes the possibility of attenuation on a ray, which also has an axisymmetric character. Such a type of ray deflection occurs in problematic issues of the tomography of GRADANs, light guides, and plasma.

Advanced Multilayer Composite Heavy-Oxide Scintillator Detectors for High Efficiency Fast Neutron Detection

We have developed and evaluated a new approach to fast neutron and neutron-gamma detection based on large-area multilayer composite heterogeneous detection media consisting of dispersed granules of small-crystalline scintillators contained in a transparent organic (plastic) matrix. Layers of the composite material are alternated with layers of transparent plastic scintillator material serving as light guides. The resulting detection medium – designated as ZEBRA – serves as both an active neutron converter and a detection scintillator which is designed to detect both neutrons and gamma-quanta. The composite layers of the ZEBRA detector consist of small heavy-oxide scintillators in the form of granules of crystalline BGO, GSO, ZWO, PWO and other materials. We have produced and tested the ZEBRA detector of sizes 100x100x41 mm and greater, and determined that they have very high efficiency of fast neutron detection (up to 49% or greater), comparable to that which can be achieved by large sized heavy-oxide single crystals of about Ø40x80 cm3 volume. We have also studied the sensitivity variation to fast neutron detection by using different types of multilayer ZEBRA detectors of 100 cm2 surface area and 41 mm thickness (with a detector weight of about 1 kg) and found it to be comparable to the sensitivity of a 3He-detector representing a total cross-section of about 2000 cm2 (with a weight of detector, including its plastic moderator, of about 120 kg). The measured count rate in response to a fast neutron source of 252Cf at 2 m for the ZEBRA-GSO detector of size 100x100x41 mm3 was 2.84 cps/ng, and this count rate can be doubled by increasing the detector height (and area) up to 200x100 mm2. In summary, the ZEBRA detectors represent a new type of high efficiency and low cost solid-state neutron detector that can be used for stationary neutron/gamma portals. They may represent an interesting alternative to expensive, bulky gas counters based on 3He or 10B neutron detection technologies.

Solar Light Guide and Window Design Based on Energy Conservation and Renovation of Old Office Buildings

A multiple of researches have been conducted at home and abroad on indoor natural lighting. However, the current lighting methods suffer from different degrees of defects, with high operation and maintenance costs. Therefore, this paper proposes a new type of multifunctional lighting window, integrating the lens fiber optic light guide device and the photovoltaic film, forming a new type of light window integrating optical lens and photovoltaic film, which can effectively meet the needs of energy conservation and environmental protection.

A 1.8e $^{-}_{\mathrm {rms}} $ Temporal Noise Over 110-dB-Dynamic Range 3.4 $\mu \text{m}$ Pixel Pitch Global-Shutter CMOS Image Sensor With Dual-Gain Amplifiers SS-ADC, Light Guide Structure, and Multiple-Accumulation Shutter

A 1.8e $^{-}_{\mathrm {rms}} $ temporal noise over 110 dB dynamic range 3.4 $\mu \text{m}$ pixel pitch global shutter (GS) CMOS image sensor (CIS) single-slope analog digital converters (ADCs) with dual-gain amplifier (SSDG-ADC), light guide (LG) structure, and multiple-accumulation shutter has been developed for various accuracy required applications. The newly developed CIS pixel achieves low noise, high saturation, high sensitivity, and high frame rate with seamless GS function. Low noise, high saturation, and high frame rate are realized by small photodiode, large charge-domain memory, and seamless multiple-accumulation readout procedure with SSDG-ADC. Furthermore, high sensitivity is realized by the optimized shape LG structure. The GS CIS is fabricated in a 130 nm 1Poly-Si 4Metal with light shield CMOS process. This image sensor achieves 1.8e $^{-}_{\mathrm {rms}} $ temporal noise, 16 200e− full-well capacity with 60 fps multiple-accumulation and 28 000e−/lx $\cdot \text{s}$ sensitivity. This image sensor also realizes high-dynamic range readout procedure and in-pixel coded exposure for deblurred images. We also describe the examination results about the relationship of the sensitivity, parasitic light sensitivity, and LG structure.

导光板发光质量评价与优化设计

导光板发光质量评价与优化设计

The Effect of Moving Light Guide System in Traffic Jam focused on Acceleration Behaviors

The Effect of Moving Light Guide System in Traffic Jam focused on Acceleration Behaviors

Reactor power monitoring using Cherenkov radiation transmitted through a small-bore metallic tube

The use of a small-bore highly reflective metallic tube has been demonstrated at a pool-type nuclear reactor for transmitting Cherenkov radiation emitted from a quartz cylinder placed near the reactor core. The study revealed the promising prospect of using a metallic tube to remotely make localized measurements in order to independently monitor reactor power using Cherenkov light generated in the water pool or inside an attached radiator. This study confirmed qualitatively and quantitatively that commercially available stainless steel tubes with highly reflective inner surfaces can adequately transport Cherenkov light, produced in the proximity of a SLOWPOKE-2 reactor core operated at 20 kW, with acceptable transmission losses over significant distances. It was demonstrated that this Cherenkov-based instrument has a fast response, high fidelity, and the Cherenkov-induced output current varies linearly with the reactor power. Scans in the orthogonal directions showed the possibility of using the Cherenkov-based instrument for 3-D mapping of the general gamma field around the reactor core. Analytical and numerical models were developed and validated by experiments to predict the transmission efficiency of light in the highly polished small-bore light guides. This paper provides details of calculations and experimental validation under laboratory conditions and at a pool-type SLOWPOKE-2 reactor.

Model-based feasibility assessment of a deep solar photobioreactor for microalgae culturing

A deep photobioreactor (PBR) based on cone-shaped light guides was conceived to improve the solar light utilization efficiency of microalgae cultures, optimizing light distribution over the culture surface and thus minimizing photoinhibition and photosaturation occurrence. A preliminary model based on local light intensities and local growth rates was developed in order to check its viability. The model was applied to a conceptual PBR unit using irradiance data of Santander (Spain). Areal biomass productivities of 15.17 and 34.57gm−2d−1 were predicted for the most unfavorable and favorable months respectively, both under monthly average cloud cover. These results are, in average, 2.72 times higher than predicted values for an open pond PBR under identical irradiance conditions. A procedure to scale-up the deep PBR in any location was developed. The procedure provides the optimal arrangement of the light guides and its operational parameters as a function of the surface incident light intensity. According to the obtained results, the novel configuration is highly efficient in land use, providing a low surface requirement solution.

Crystals and light guides for the mid-infrared spectral range

The physicochemical properties of crystals of AgClxBr1−x solid solutions and new AgBrxI1−x, Ag1−xTlxBr1−xIx, and Ag1−xTlxBr1−0.54xI0.54x crystals grown by the Bridgman method using equipment created at the Ural Federal University are studied herein. The crystal compositions are determined from the region of existence of solutions stable at room temperature using the state diagrams of the AgCl–AgBr, AgBr–AgI, AgBr–TlI, and AgBr–(TlBr0.46I0.54) systems studied here. The refractive indices are determined by Michelson interferometry and by a spectroscopic method using an infrared (IR) Fourier spectrometer in the wavelength range from 0.632 to 14.0 μm. Accordingly, the transmission spectra of the crystals and light guides in the range from 0.19 to 41.6 μm are measured, and their mechanical properties are studied. The photon structure of IR light guides is simulated.

Решение для фундаментальной моды ступенчатого оптического волоконного волновода с керровской нелинейностью

Решение для фундаментальной моды ступенчатого оптического волоконного волновода с керровской нелинейностью

Upgrade of the monitoring system of LHCb ECAL

In order to improve the stability of the LHCb ECAL monitoring system, the light guides transporting LED light to PMTs have been replaced by radiation hard quartz fibers. The behavior of transparency of the selected fibers under moderate radiation doses, up to few kGy, was studied in detail. The performance of the upgraded version of the LHCb ECAL monitoring system is also discussed.

Display Light Guide Swelling Due to Moisture Absorption

Display light guides, commonly constructed of a polymer such as polymethyl methacrylate (PMMA), are known to be susceptible to moisture absorption, swelling, and warping in the field when exposed to elevated ambient humidity levels. This work presents a quantitative theoretical framework for calculating water absorption over time. In addition, a simple theory is laid out, which connects mass absorption of water to linear expansion of the polymer. Finally, a simple quantitative analysis of out-of-plane warping of the light guide is presented. Experimental data from laboratory PMMA coupons and two different sizes of large displays are used to establish the values of key parameters of the theoretical model. General purpose results for any size of PMMA display are presented. The approach can easily be adapted to light guides fabricated using other polymers.

Choice of mathematical models for technological process of glass rod drawing

The technological process of drawing glass rods (light guides) is considered. Automated control of the drawing process is reduced to the process of making decisions to ensure a given quality. The drawing process is considered as a control object, including the drawing device (control device) and the optical fiber forming zone (control object). To study the processes occurring in the formation zone, mathematical models are proposed, based on the continuum mechanics basics. To assess the influence of disturbances, a transfer function is obtained from the basis of the wave equation. Obtaining the regression equation also adequately describes the drawing process.

Photorefractivity of germanosilicate light guides

In the fabrication of single-mode germanosilicate light guides, we studied how a reducing atmosphere in the high-temperature compression process of fiber preforms in a modified chemical vapor deposition process affects the photorefractive properties of the light guides. The results indicate an increase in photorefractivity and a decrease in the fiber drawing temperature with additional doping of the core of the light guide with fluorine.