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Influence of cooling on edge effects in laser forming
摘要： Edge effects in laser forming influence the possible tolerances that can be achieved with laser forming. Edge effects arise due to uneven temperature profiles along the laser scan line. It has been suggested that an increased cooling rate can minimize the occurrence of edge effects. This work will examine the effect of increased cooling to reduce edge effects. The height profile along the laser scan line is reported and compared for different levels of cooling using experiments and simulations. The results show that increased cooling has no impact on the edge effects.
关键词： Laser forming,Edge effects,Active cooling
更新于2025-09-12 10:27:22
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Thermal and optical performance characteristics of a spatial light modulator with high average power picosecond laser exposure applied to materials processing applications
摘要： A spatial light modulator (SLM) addressed with Computer Generated Holograms (CGH’s) can create structured light fields when an incident laser beam is diffracted by a phase CGH. The power handling limitations of SLMs based on a liquid crystal layer have always been of some concern. Now, with careful engineering of chip thermal management, we present the detailed optical phase and temperature response of a liquid cooled SLM exposed to picosecond laser average powers up to 220W at 1064nm – new knowledge critical for determining device performance at high laser powers. SLM chip temperature rose linearly with incident laser exposure, increasing by only 5°C at 220W incident power, measured with a thermal imaging camera. Thermal response time with continuous exposure was 1-2 seconds. The optical phase response with incident power approaches 2π radians with average powers up to 130W while above this power, liquid crystal thickness variations limit phase response to just over π radians. These remarkable performance characteristics show that liquid crystal based SLM technology is highly robust when efficiently cooled. High speed, multi-beam plasmonic surface micro-structuring at a coverage rate of 8cm2s-1 is achieved on polished metal surfaces at 25W exposure, while diffractive multi-beam surface ablation on stainless steel at an ablation rate of ～4mm3min-1 is demonstrated with average power 100W. Continuous exposure for many hours exceeding 100W laser power did not result in any detectable drop in diffraction efficiency hence no permanent changes in SLM phase response characteristics have been observed This research work will help to accelerate the use of liquid crystal SLMs for both scientific and ultra-high throughput laser-materials micro-structuring applications.
关键词： Spatial light modulator,active cooling,high average power picosecond laser,high power laser micro-machining
更新于2025-09-12 10:27:22
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A Heat Pipe Cooler for High Power LED’s Cooling in Harsh Conditions
摘要： The paper presents an innovative method for High Power LEDs cooling in harsh conditions. To take full advantage of the benefits of LEDs, proper thermal management must be realized. This paper describes the limits of the cooling solution based on heat pipe, to maintain the junction temperature close to the nominal value, to avoid the color shift, recoverable light output reduction, voltage decreases. The most important, the reliability of any LED is a direct function of junction temperature, knowing that the higher the junction temperature, the shorter the lifetime of the LED.
关键词： LED Cooling,Energy Efficiency.,Heat-Trap,Heat Pipe
更新于2025-09-12 10:27:22
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Characterization of a 100 micrometer-scale cryogenically cooled gas jet for near-critical density laser-plasma experiments
摘要： We present the design and characterization of a thin, high density pulsed gas jet for use in the study of near critical laser plasma interactions with ultrashort Ti:sapphire laser pulses. The gas jet uses a range of capillary nozzles with inner diameters between 50 and 150 μm and is operated in the sonic regime. Cryogenic cooling of the gas valve body to ?160 ○C provides the necessary density enhancement for reaching overcritical plasma densities at λ = 800 nm (Ncr ≈ 1.7 × 1021 cm?3) using hydrogen gas at jet backing pressures below 1000 psi. Under certain conditions, fast expansion of the gas from a nozzle can lead to formation of clusters; here, we use our previously demonstrated all-optical method to estimate the cluster mean size and density. For the jets studied here, we find that cluster formation only begins at distances from the nozzle exit greater than a few times the nozzle orifice diameter.
关键词： laser-plasma interactions,cluster formation,gas jet,high density plasmas,cryogenic cooling
更新于2025-09-12 10:27:22
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Natural cooling of two axis tracking photovoltaic module
摘要： Recently, the solar energy is considered as one of the most essential alternative sources of energy, which make it significant to operate the photovoltaic (PV) modules at optimal points to attain maximum output powers at utmost efficiencies. In this work, a novel operational optimization scheme is proposed to maximize the electrical output power and its efficiency for two axis sun tracking PV module. The technique incorporates the influence of the surrounding environmental parameters; such as ambient temperature, wind speed, and wind direction to improve performance. The increase in power and efficiency is accomplished by benefiting from the local wind speed and wind direction to cool the cells temperatures, which in return assist the PV to operate at its Maximum Power Point Tracking (MPPT). These newly proposed operating angles (i.e., Azimuth and Tilt) for two axis sun tracking systems may not necessarily coincide with the perpendicular orientation used by conventional sun tracking PV modules. Finally, the effectiveness of the operational optimization technique and its effect on MPPT was verified using computer simulations using actual collected weather data that was obtained from Shams Maan weather station in Jordan.
关键词： PV cooling,solar optimization,Solar Tracking,PV improved efficiency,two axes tracers
更新于2025-09-12 10:27:22
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LASER ANEMOMETRY METHOD FOR PARTICLE VELOCITY MEASUREMENT IN THE BOSE-EINSTEIN CONDENSATE
摘要： Studying of physical and engineering conditions of the process of atom velocity measurement in Bose-Einstein condensate is performed in the paper. In order to provide for the metrological support of the particle laser cooling process it is suggested the laser anemometry method based on measuring the Doppler frequency shift due to scattering of laser radiation by the moving particles to be cooled. The laser anemometry method for estimation of the particle velocity during the particle laser cooling process and the interferential model of the laser Doppler anemometry are provided. The requirements set to technical specifications of the laser Doppler anemometer are determined. The results of the paper form the basis of providing for the metrological support of the particle laser cooling process performed in order to create new frequency standards, the Bose-Einstein condensate and the quantum memory.
关键词： Bose-Einstein condensate,velocity measurement,laser Doppler anemometry,laser cooling of the particles
更新于2025-09-12 10:27:22
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The spectroscopic properties of the low-lying excited states and laser cooling scheme of SrBr molecule
摘要： The potential energy curves and the transition dipole moments for seven electronic states of SrBr molecule are obtained via the multi-reference configuration interaction method and the all-electron basis sets. The Davidson and relativistic corrections are also included. Based on the obtained potential energy curves, the rotational and vibrational energy levels of each electronic state are determined by solving the nuclear motion equation of the molecule. The spectroscopic parameters are fitted from the obtained energy levels by using Dunham expression. Moreover, the spin-orbit coupling splits of the A2Π state are considered to construct the optical laser cooling scheme. The Frank-Condon factors, radiation lifetimes, radiation widths between the ground electronic state and 2Π1/2, 3/2/B2Σ+ states are calculated. Then, the feasibility of laser cooling is explored and the optical scheme is proposed. The results demonstrate that the SrBr molecule is a promising candidate for laser cooling.
关键词： Frank-Condon factors,optical scheme,laser cooling,Radiative lifetime,Spectroscopic parameter
更新于2025-09-12 10:27:22
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An algorithm for designing a cooling system for photovoltaic panels
摘要： Solar energy is an abundant source of energy for generating electricity. One of the main challenges in using solar energy is that solar photovoltaic (PV) panels are typically used in regions where solar radiation is high; consequently, the temperature of the panels will increase, and the efficiency of the panels will decrease. Adding cooling tubes to the PV panel is a possible approach to cool it down. To design such cooling systems, CFD simulations may be used; however, this approach tends to be time-consuming. In this paper, we report a new algorithm for designing straight cooling tubes. The algorithm can be used to determine important design parameters such as tube center-to-center length, diameter of the tube, and the minimum tube length needed to achieve a desired outlet temperature. The accuracy of the algorithm was tested using real-world data (including various ambient temperatures and solar radiations) and the maximum temperature difference between desired outlet temperature and CFD simulation for the designed cooling system was found to be 1.7oK.
关键词： Solar energy,Conjugated heat transfer,Design algorithm,Renewable energy,PVT,Cooling system
更新于2025-09-12 10:27:22
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Integrative passive and active cooling system using PCM and nanofluid for thermal regulation of concentrated photovoltaic solar cells
摘要： An integration of passive and active cooling systems for thermal regulation of concentrated photovoltaic (CPV) solar system has been developed and modeled. A heat storage battery of phase change material (PCM) is combined with a closed loop water cooling system in the developed design. A two dimensional model has been developed for the simulation of the CPV layers with the integrated cooling system. Results have been investigated to evaluate the thermal and electrical performances of the system components and the entire system. Further investigations have been conducted to study the effects of different arrangements of the PCM plates in the water tank on the system performances. Enhancing the system performance by using nanofluid as heat transfer fluid (HTF) was also evaluated. Results showed that the proposed system achieves 60% reduction in the CPV average temperature compared to the conventional direct PCM-PV and water-cooling individual systems. At 10 concentration ratio (CR) and 0.01 m/s HTF velocity, the cell temperature does not exceed 78 °C. Moreover, the PCM maximum temperature is kept below the degradation temperature limit. The effect of the PCM plates’ arrangements in the water tank on the system performance is negligible. Using nanofluid as HTF enhancer increases the CPV efficiency by 2.7% and reduces the PV maximum temperature and the PCM melting time by 4 °C and 12%, respectively.
关键词： Concentrated photovoltaic,Integrative passive-active cooling system,PCM,Thermal regulation,Nanofluid
更新于2025-09-12 10:27:22
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An Amateur's Guide to Observing and Imaging the Heavens || Imaging with Cooled CCD Cameras
摘要： The latest DSLR cameras can do a very good job of astro-imaging and can, of course, be used for general photography as well, so why go to the expense of buying a cooled CCD camera? The main reason lies in the word ‘cooled’. All imaging chips produce dark current noise which increases with exposure time and is also highly dependent on its temperature, that of a typical chip dropping by half for each drop of 6 degrees Celsius in temperature. So, if the chip is cooled by 30 degrees below ambient temperature, the dark current noise will have dropped by about 5 times, so allowing longer exposures to be taken before dark current noise becomes a problem. Given dark skies that do not suffer from light pollution, this can allow images to reveal faint nebulosity that would otherwise be lost in the noise. When significant light pollution is present, the exposure times, and hence the dark current contribution, have to be less, before the skylight becomes obtrusive, and so cooling does not confer as great an advantage. The latest chips have very low dark currents, and it is rarely worth cooling them down below about –20 C. This temperature can normally be reached with the single-stage Peltier cooling employed in CCD cameras aimed at the amateur market.
关键词： Peltier cooling,light pollution,cooled CCD cameras,dark current noise,astro-imaging
更新于2025-09-12 10:27:22