scholarly journals Neutral and Ionic Particle Emission Produced by Laser Irradiation of a GaAs Surface

1984 ◽  
Vol 5 (1) ◽  
pp. 1-10 ◽  
Author(s):  
G. R. Möhlmann
Keyword(s):  
Radiation Power ◽  
Incident Radiation ◽  
Particle Emission ◽  
Gaas Surface ◽  
Experimental Result ◽  
Atomic Ions ◽  
Neutral Particles ◽  
Incident Laser Radiation ◽  
Thermal Mechanism ◽  
Set Up

The emission of gas phase particles from a GaAs surface, due to irradiation at 1064 nm by an unfocussed Q-switched Nd:YAG laser beam, has been studied. Mass spectra have been recorded with the aid of a quadrupole mass spectrometer, and the ion-neutral ratio of the emitted particles has been measured with an electrical diode set up. The applied incident laser radiation power density was varied in the range 1.2–9.6 × 107 Watts/cm2 and was delivered as 10 ns (fwhm) long pulses. It appeared that mainly Ga atoms and As2 molecules were emitted, together with minor amounts (<1%) of Ga2 and GaAs molecules. Besides the emission of neutral particles, the formation of Ga+ atomic ions was observed. By measuring the ratio of Ga+ ions and Ga neutral atoms it could be shown that the (ionic) particle emission is governed by a thermal mechanism for 1064 nm incident radiation. This latter experimental result differs from that obtained if a ruby laser (694 nm) is used as the radiation source.

scholarly journals Высокоэффективное преобразование лазерного излучения высокой плотности

2019 ◽  
Vol 45 (2) ◽  
pp. 26
Author(s):  
А.Н. Паньчак ◽  
П.В. Покровский ◽  
Д.А. Малевский ◽  
В.Р. Ларионов ◽  
М.З. Шварц
Keyword(s):  
Laser Radiation ◽  
Power Density ◽  
Open Circuit Voltage ◽  
Radiation Power ◽  
Incident Radiation ◽  
Open Circuit ◽  
Incident Laser ◽  
Voltage Level ◽  
Incident Laser Radiation ◽  
Radiation Conversion

AbstractAlGaAs/GaAs-based semiconductor photovoltaic converters (PVCs) of laser radiation, capable of operating at an illuminance up to 9 kW/cm^2 with retained isothermal state have been studied. This state was confirmed by the logarithmic shape of dependences of the open-circuit voltage on the power density of incident laser radiation. At maximum illuminance, the open-circuit voltage level was close to 1.33 V. It is shown that the proposed PVCs can provide laser radiation conversion at an 840-nm wavelength with efficiency above 51% at an incident radiation power density of 2.5 kW/cm^2.

scholarly journals Боковой перенос энергии при возбуждении плазмонов терагерцовой волной в периодической пространственно несимметричной графеновой структуре

2019 ◽  
Vol 53 (9) ◽  
pp. 1189
Author(s):  
Д.В. Фатеев ◽  
К.В. Машинский ◽  
И.М. Моисеенко ◽  
В.В. Попов
Keyword(s):  
Incident Wave ◽  
Radiation Power ◽  
Power Conversion ◽  
Incident Radiation ◽  
Terahertz Wave ◽  
Wave Power ◽  
Excitation Condition ◽  
Maximum Conversion

AbstractThe power conversion of a terahertz wave normally incident on a periodic graphene structure to propagating-plasmon power is theoretically studied. The conditions of the maximum conversion of the incident radiation power to the propagating-plasmon power and excitation condition of unidirectional traveling plasmon are determined. It is found that up to 15% of the incident wave power can be converted to propagating-plasmon power.

UPGRADE FOR THE CBELSA/TAPS EXPERIMENT AT ELSA FOR η AND η′ DECAYS

2010 ◽  
Vol 19 (05n06) ◽  
pp. 938-945 ◽  
Author(s):  
◽  
MICHAEL LANG
Keyword(s):  
Cross Sections ◽  
Major Part ◽  
Charged Particles ◽  
Final State ◽  
Accelerator Facility ◽  
Neutral Particles ◽  
Tracking Detector ◽  
Set Up ◽  
Photo Production

The CBELSA/TAPS experiment is a set up installed at the accelerator facility ELSA in Bonn. It is used to measure cross sections of hadronic reactions by observing final state particles. The set up is well suited for the identification of neutral particles such as neutrons and photons (e.g. from π0 decay). It is planed to access the major part of η and η′ photo production and decays as also strangeness. This requires a neutral trigger capability for the detector set up and a tracking detector for charged particles.

scholarly journals Nonuniform Heat Transfer Model and Performance of Molten Salt Cavity Receiver

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1001
Author(s):  
Jianfeng Lu ◽  
Yarong Wang ◽  
Jing Ding
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Thermal Efficiency ◽  
Radiation Flux ◽  
Incident Radiation ◽  
Heat Transfer Model ◽  
Experimental Result ◽  
Transfer Model ◽  
Fluid Temperature ◽  
Primary Role

The temperature distribution and thermal efficiency of a molten salt cavity receiver are investigated by a nonuniform heat transfer model based on thermal resistance analysis. For the cavity receiver MSEE in Sandia National Laboratories, thermal efficiency in this experiment is about 87.5%, and the calculation value of 86.93–87.79% by a present nonuniform model fits very well with the experimental result. Different from the uniform heat transfer model, the receiver surface temperature in the nonuniform heat transfer model is remarkably higher than the backwall temperature. The incident radiation flux plays a primary role in thermal performance of cavity receiver, and thermal efficiency approaches to maximum under optimal incident radiation flux. In order to increase thermal efficiency, various methods are proposed and studied, including heat convection enhancement by an increase of flow velocity or the decrease of the tube diameter and number of tubes in the panel, and heat loss decline by a decrease of view factor, surface emissivity and insulation conductivity. According to calculation results by different modes of the nonuniform heat transfer model, the thermal efficiency of the cavity receiver is reduced by nonuniform heat transfer caused by variable fluid temperature or variable circumferential temperature, so thermal efficiency calculated by variable fluid temperature and variable circumferential temperature is lower than that calculated by average fluid temperature and bilateral uniform circumferential temperature for 0.86%.

scholarly journals Optical Ray-Tracing Performance Modeling of Quartz Half-Shell Tubes Aperture Cover for Falling Particle Receiver

2019 ◽  
Author(s):  
Julius Yellowhair ◽  
Clifford K. Ho
Keyword(s):  
Ray Tracing ◽  
Quartz Glass ◽  
Side Wall ◽  
Incident Radiation ◽  
Concave Side ◽  
Test Facility ◽  
Optical Performance ◽  
The North ◽  
Set Up ◽  
Cfd Analyses

Abstract A 1 MWt falling particle receiver prototype was designed, built and is being evaluated at Sandia National Laboratories, National Solar Thermal Test Facility (NSTTF). The current prototype has a 1 m2 aperture facing the north field. The current aperture configuration is susceptible to heat and particle losses through the receiver aperture. Several options are being considered for the next design iteration to reduce the risk of heat and particle losses, in addition to improving the receiver efficiency to target levels of ∼90%. One option is to cover the receiver aperture with a highly durable and transmissive material such as quartz glass. Quartz glass has high transmittance for wavelengths less than 2.5 microns and low transmittance for wavelengths greater than 2.5 microns to help trap the heat inside the receiver. To evaluate the receiver optical performance, ray-tracing models were set up for several different aperture cover configurations. The falling particle receiver is modeled as a box with a 1 m2 aperture on the north side wall. The box dimensions are 1.57 m wide × 1.77 m tall × 1.67 m deep. The walls are composed of RSLE material modeled as Lambertian surfaces with reflectance of either 0.9 for the pristine condition or 0.5 for soiled walls. The quartz half-shell tubes are 1.46 m long with 105 mm and 110 mm inner and outer diameters, respectively. The half-shell tubes are arranged vertically and slant forward at the top by 30 degrees. Four configurations were considered: concave side of the half-shells facing away from the receiver aperture with (1) no spacing and (2) high spacing between the tubes, and concave side of the half-shells facing the aperture with (3) no spacing and (4) high spacing between the tubes. The particle curtain, in the first modeling approach, is modeled as a diffuse surface with transmittance, reflectance, and absorptance values, which are based on estimates from previous experiments for varying particle flow rates. The incident radiation is from the full NSTTF heliostat field with a single aimpoint at the center of the receiver aperture. The direct incident rays and reflected and scattered rays off the internal receiver surfaces are recorded on the internal walls and particle curtain surfaces as net incident irradiance. The net incident irradiances on the internal walls and particle curtain for the different aperture cover configuration are compared to the baseline configuration. In all cases, just from optical performance alone, the net incident irradiance is reduced from the baseline. However, it is expected that the quartz half-shells will reduce the convective and thermal radiation losses through the aperture. These ray-tracing results will be used as boundary conditions in computational fluid dynamics (CFD) analyses to determine the net receiver efficiency and optimal configuration for the quartz half-shells that minimize heat losses and maximize thermal efficiency.

Effect of Clay on Tensile, Flex and Fatigue Behavior of Carbon Fiber Reinforced Epoxy

2011 ◽  
Author(s):  
Yuanxin Zhou ◽  
Mahesh Hosur ◽  
Zainuddin Shaik ◽  
Shaik Jeelani
Keyword(s):  
Distribution Function ◽  
Weibull Distribution ◽  
Fatigue Behavior ◽  
Damage Model ◽  
Experimental Result ◽  
Weibull Distribution Function ◽  
Set Up ◽  
Static Failure ◽  
Good Agreement ◽  
Properties Of Composites

In this study, the nanophased epoxy with 2 wt.% clay was utilized in a vacuum assisted resin transfer molding (VARTM) set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on mechanical properties of composites has been evaluated by tensile, flexural and fatigue test. The tensile and flexural strengths improved by 5.7% and 13.5%, respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental result, a linear damage model combined with the Weibull distribution function has been established to describe static failure processing of neat and nanophased carbon/epoxy. The simulated stress strain curves from the model are in good agreement with the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull distribution function.

INVESTIGATION OF NONLINEAR INTERACTION OF ELECTROMAGNETIC RADIATION WITH SPACE CHARGE IN VACUUM ELECTRONIC DEVICES

2012 ◽  
Vol 15 ◽  
pp. 105-112
Author(s):  
A.H. MAKARYAN ◽  
H.S. HAROYAN ◽  
V.A. SAHAKYAN ◽  
V.R. TADEVOSYAN
Keyword(s):  
Electromagnetic Radiation ◽  
Space Charge ◽  
Nonlinear Interaction ◽  
Radiation Power ◽  
Incident Radiation ◽  
Polarization Current ◽  
Vacuum Electronic Devices ◽  
Power Direction ◽  
Current Characteristics ◽  
Detection Characteristics

The nonlinear interaction of electromagnetic radiation in microwave, terahertz, and optical regions with non-uniformly distributed space charge in the interelectrode space of vacuum devices is investigated. The detection of electromagnetic radiation in the vacuum electronic tubes (diode and triode) with parallel plate electrodes is experimentally demonstrated. The dependence of the detected signal on the incident radiation power, direction of wave polarization, current characteristics and frequency of modulating signal has been investigated. The equation of motion of an electron in the field of electromagnetic wave in the presence of space charge was obtained, according to which, the detection is due to nonlinearity associated with the non-uniform distribution of electrons along the electrostatic field direction. The measured detection characteristics are in reasonable agreement with theoretical estimates.

Research of Test Model for Eggshell Crack Detection

2013 ◽  
Vol 846-847 ◽  
pp. 655-658
Author(s):  
Jian Yang ◽  
Chun Yan Xia ◽  
He Pan ◽  
Ying Shi ◽  
Xiu Ying Li
Keyword(s):  
Neural Network ◽  
Crack Detection ◽  
Fuzzy Neural Network ◽  
Detection Method ◽  
Experimental Result ◽  
Test Model ◽  
Inference Rules ◽  
Characteristic Parameters ◽  
Fuzzy Neural ◽  
Set Up

In order to realize the precise identification of eggshell crack, we design eggshell cracks detection method based on image processing and fuzzy neural network. Firstly this method gets two pieces image of eggs and processes, and then counts number of the same gray pixel. Determine five characteristic parameters as the input of fuzzy neural network. Set up a fuzzy neural network. Its structure is 5-10-1. Eggshell cracks and noise in egg images were distinguished using automatically learning and inference rules of fuzzy neural network. Use 147 groups of parameters for training network and rest 58 sample for verifying. Experimental result shows that the model can meet actual testing requirements with fast, stable, high precision and good robustness, easy to implement. Its precision reached 94.55%.

Equation-Solving DRESOR Method for Radiative Transfer in an Absorbing–Emitting and Isotropically Scattering Slab With Diffuse Boundaries

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Wang Guihua ◽  
Zhou Huaichun ◽  
Cheng Qiang ◽  
Wang Zhichao
Keyword(s):  
Boundary Surface ◽  
Computation Time ◽  
Incident Radiation ◽  
Dimensional System ◽  
Equation Solving ◽  
The Monte Carlo Method ◽  
Order Of Magnitude ◽  
Reflecting Boundaries ◽  
Overall Performance ◽  
Set Up

The distribution of ratios of energy scattered by the medium or reflected by the boundary surface (DRESOR) method can provide radiative intensity with high directional resolution, but also suffers the common drawbacks of the Monte Carlo method (MCM), i.e., it is time-consuming and produces unavoidable statistical errors. In order to overcome the drawbacks of the MCM, the so-called equation-solving DRESOR (ES-DRESOR) method, an equation-solving method to calculate the DRESOR values differently from the MCM used before, was proposed previously. In this method, a unit blackbody emission is supposed within a small zone around a specified point, while there is no emission elsewhere in a plane-parallel, emitting, absorbing, and isotropically scattering medium with transparent boundaries. The set of equations for the DRESOR values based on two expressions for the incident radiation was set up and solved successfully. In this paper, the ES-DRESOR method is extended to a one-dimensional system with diffusely reflecting boundaries. The principle and formulas are given. Several examples with different parameters are taken to examine the performance of the proposed method. The results showed that all the DRESOR values obtained using the ES-DRESOR method agree well with those got using MCM. The average relative error for the intensity obtained by the ES-DRESOR method is 9.446 × 10−6, lower by over 1 order of magnitude than the 2.638 × 10−4 obtained by the MCM under the same conditions. More importantly, the CPU time for computing the DRESOR values, which ranges from several hundred seconds to several thousand seconds using the MCM, is reduced to 0.167 s using the ES-DRESOR method. The computation time is shortened by about 3 orders of magnitude. The overall performance of the ES-DRESOR method is excellent.

Research of Object Tracking Algorithm Based on BRISK

2014 ◽  
Vol 1049-1050 ◽  
pp. 1496-1501
Author(s):  
Shi Xu Guo ◽  
Jia Xin Chen ◽  
Bo Peng
Keyword(s):  
Object Tracking ◽  
Real Time ◽  
Feature Matching ◽  
Tracking Algorithm ◽  
Experimental Result ◽  
Moving Target ◽  
Target Template ◽  
Result Show ◽  
Search Feature ◽  
Set Up

In view of the problems that high complexity, large calculation and the difficulty to apply to real-time systems in the current moving target tracking algorithm, this paper introduce the BRISK feature extraction algorithm, and proposed the object tracking algorithm based on BRISK. Set up the background model and use the background difference method to detect the moving target template. Then match in the next frame and track the target. In order to reduce the search feature matching area, further improve the real-time of the algorithm, we also introduce the kalman filter algorithm to estimate the target motion trajectory. The experimental result show that comparing with the SURF, SIFT feature tracking algorithm, the algorithm of this paper has greatly improved in real-time.

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