In order to study the disturbing effect of pulsed laser irradiation on array CCD camera, experiment of CCD camera disturbed by single pulse laser was carried out at short-distance. A 1064nm laser was chosen as the irradiation source, which was attenuated by attenuation pieces before entering the CCD lens. An aperture was set before CCD lens to limit spot size to radius of 2.5mm. 50% laser was split for monitoring the laser stability and the other 50% entered CCD camera. The entering laser energy was started with 2.48 nano Joule, and CCD camera was in normal work condition; along with the increase of laser pulse energy, saturated pixels came out in the image plane, and saturated zone increased at the same time. With the laser pulse energy increasing to 47.1 nano Joule, a short crosstalk line appeared above the main spot, and there was a certain distance between them. With increasing of laser pulse energy, distance between crosstalk line and main spot reduced and the crosstalk line became lighter and thicker, a shorter horizontal crosstalk in the middle of longitudinal crosstalk line became obvious at the same time. The experimental results has some differences between the gap on crosstalk line and unilateral crosstalk line, which provides some new experimental data for analysing disturbing effect of laser irradiation on array CCD.
Laser as a high energy density light source and silicon cell as a widely used photoelectric conversion element, the interaction between the two has become a research hotspot in wireless energy transmission and semiconductor material damage. At present, the experimental and theoretical research mainly focuses on the damage threshold and morphology, electrical output characteristics and action mechanism. The resistance of the silicon cell affecting electrical output was mainly qualitative analysis, but few quantitative studies. Different degrees of damage were simulated though pulsed laser irradiation in different positions of the silicon cell. The parallel resistance and series resistance of the silicon cell were estimated by linear fitting at V0 and I0 of IV curve, and the variation of the resistances was quantitatively obtained under different degrees damage. The results show that the damage induced by pulsed laser irradiation is obvious melting ablation and the damage is irreversible when the optical power density is 3.3×108W / cm2 , one pulse irradiation damage is equivalent to the resistances of 67 in parallel and 189 m in series for silicon cell, the output voltage decreases approximately linearly with the increase of irradiation times and the output voltage is about half of the initial voltage after 6 times irradiation. In addition, the output voltage was rapidly increased to a peak with the loading of pulsed laser, which is almost independent of the damage of the silicon cell.
In order to better study the damage effect of nanosecond pulsed laser on PIN photodiodes, a two-dimensional axisymmetric model and heat source model of nanosecond irradiation photodiodes were established according to the theory of heat conduction, and the factors of thermal physical parameters changing with temperature were considered. The finite element COMSOL Multiphysics software was used to simulate the temperature field distribution of PIN photodiodes irradiated by nanosecond pulse lasers. The research results show that the temperature change trend of the target surface under different energy densities is consistent, and there is a phenomenon of energy ac-cumulation. From the center of the irradiation to the edge of the target, the temperature gradually weakens and dis-tributes in a gradient. and the temperature rise rate of the target is directly proportional to the increase in energy density. It is found that the melting damage of the photodiode is reached. The range of energy density is, 144.01mJ/cm2 ~ 175.58 mJ/cm2 , The research results provide a theoretical basis for the research field of laser damage to materials.
Plasma assisting technique has shown great prospect in various combustion environments. Especially in terrible combustion problems, plasma brings heat effects, chemical kinetic effects, or transport effects to influence combustion. Fundamental research of non-equilibrium plasma assisting combustion is prerequisite for its engineering application. Counterflow burner provides an ideal and favourable platform to investigate aforementioned problems. This article integrated non-equilibrium plasma discharge system and counterflow burner to investigate influence of coaxial double air gap dielectric barrier discharge on counterflow diffusion flame. OH radicals generation and radiation were observed to reveal basic chemical kinetic mechanisms of plasma. Ultraviolet intensified ICCD camera was used to record OH radicals’ spontaneous radiation in flame sheet. Radiation images show that plasma discharge would increase intensity of OH radicals’ radiation and combustion of flat flame when discharge voltage was under certain value; when discharge voltage exceeded the certain value, airflow in burner would be inevitably affected by discharge, and uniformity of OH radicals’ radiation declined, while in the central zone, flow speed increased, thermal loss decreased and combustion-assistant effects weakened.
Ignition delay time of diluted iso-octane/Air mixtures were measured in a single pulse reflected shock tube. In this work, the onset of ignition was determined by monitoring both the pressure history and the emitted light corresponding to OH* emission. The photomultiplier tube (PMT) in specially designed housing at CaF2 window were used with 310±5nm filters to measure the ultraviolet OH* emission. Experiments were performed at temperatures between 1295K and 2487K, pressures about 1 atm. and varying equivalence ratios (Φ;=0.25, 0.5, 1.0, 2.0). Long shock tube dwell time (about 15ms) was achieved by tailored contact surface operation under such conditions. To simulate real engine environment, liquid fuel aerosol was generated by the supersonic atomizer, and the size of fuel droplet in aerosol was measured. Both pressure and OH*emission histories were obtained to determine the ignition delay time and the relative strength of the ignition process. The OH* emission time history data showed that there were different behaviors of iso-octane in ignition process under varying temperatures. Several potential chemical kinetics mechanisms were used to simulated iso-octane autoignition under the same conditions. Analysis of the experiments results and simulations supported the validation of those chemical kinetics mechanisms. The experimental data was consistent with the prediction of mechanism in low temperatures and the experiment data showed that the factors of temperature and equivalent ratio have different effect on the ignition delay time
Planar Laser-Induced Fluorescence (PLIF) technique, which is a non-intrusive, fast-response diagnostic method, has been widely used in measurement of various complex flow fields. Both cold flowfield[1-4] and combustion flowfield[5] have made use of PLIF for diagnosis. According to the different flow field and investigation objects, parameters such as fluorescence tracer molecule, laser wavelength, and so forth should be selected seriously in order to obtain the information concerned. This technique was used to investigate complicated flow structure of mixing between transverse jet and supersonic flow, in which acetone and OH radicals were chosen as the fluorescence tracer molecules in the experiments of cold flow and combustion flow respectively. During cold flow measurements, air was used as both the transverse jet and supersonic flow, and liquid acetone was gasfied before adding into the transverse jet, which was excited by laser sheet of 266nm. During combustion flow measurement, ethylene was used as the transverse fuel jet, and combustion between air and ethylene was sustained by plasma discharge. Laser sheet of 283nm was used excite the intermediate product of OH radicals. Fluorescence images were recorded by the intensified CCD camera after filtering interfere light. Both results show that PLIF displays as a credible and valid method for investigating complicated cold flowfield and combustion structure, so long as chosing appropriate fluorescence tracer molecule, laser exciting wavelength, optical filter, et al.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.