On the effect of photoinduced emission of alkali atoms from a paraffin coating on the rate of spin relaxation of atoms in the volume of a cell

The effect of photoinduced emission of alkali atoms from the paraffin coating of a cell on the spin relaxation time of the atoms was studied experimentally. No effect was detected. It was additionally found that long irradiation of the cell surface by light with a power density of about 1 mW/cm² does not cause any degradation of the coating in spite of almost complete removal of the atoms from the coating due to their photostimulated diffusion in the layer and photodesorption. After the irradiation is complete, the surface contacting with the alkali vapor is again saturated with the alkali atoms with a time constant of about 1 h.     

488 nm连续激光晶化本征非晶硅薄膜的喇曼光谱研究

利用等离子增强化学气相沉积系统制备了本征非晶硅薄膜,并选用488 nm波长的连续激光进行晶化.采用喇曼测试技术对本征非晶硅薄膜在不同激光功率密度和扫描时间下的晶化状态进行了表征,并用514 nm波长与488 nm波长对样品的晶化效果进行了比较.测试结果显示:激光照射时间60 s, 激光功率密度在1.57×10⁵ W/cm²时,能实现非晶硅向多晶硅的转变,在功率密度达到2.7 56×10⁵ W/cm²时,有非晶开始向单晶转变,随着激光功率密度的继续增加,晶化结果仍为单晶;在功率密度为2.362×10⁵ W/cm²下,60 s照射时间晶化效果较好;在功率密度为2.756×10⁵ W/cm²和照射时间为60 s的条件下,用488 nm波长比514 nm波长的激光晶化本征非晶硅薄膜效果较好,并均为单晶态.     

Laser ablation of copper and aluminium in air

The ablation behavior of copper alloy and aluminium irradiated in air by 1.06 m, 10 ns pulsed laser with power density of 6.4×10⁹W/cm² was studied using scanning electron microscopy (SEM), MCS-RBS and X-ray microanalysis. Evidence of bulk vaporization via bubble formation was observed for the copper alloy under the laser irradiation. Silver-enrichment microregions were found in the ablation crater created by the laser shots on the copper alloy sample. Material removal rates of these materials were determined by crater shape-profile measurement. Using self-similar solutions of the gas-dynamic equations, gas-dynamic parameters of the vaporization waves are obtained. These parameters are used to calculate material removal rates and impulse coupling coefficients of these materials under the pulsed laser irradiation. The calculated mass removal rates and the coupling coefficients are compared with the corresponding experimentally determined values. The surface kinetic energy of the irradiated area on the Al sample is estimated. Possible mechanisms for laser ablation of the materials under study are discussed.     

Indicatrices of the Radiation Intensity of Laser Plasma Formations in the Air

We have investigated the indicatrices of the visible and IR radiation of laser plasma formed under irradiation of cadmium, indium, and silicon in the air by radiation from a monopulsed neodymium laser with a power density at the irradiation spot of up to 12 GW/cm² on the first harmonic and up to 4 GW/cm² on the second harmonic. It is shown that the radiant intensity indicatrices have a prolate form depending on the target material, the spectral range of observation, and the power density of the acting laser radiation. The radiant intensity of laser plasma in the 0.3–4.2 m range is approximately proportional to the laser radiation power density and depends on the target material.     

Degradation of gallium arsenide under irradiation with an excimer laser

The results of a study of degradation of the surface of gallium arsenide resulting from irradiation with a power excimer laser at power densities ranging from the threshold power to the power level causing local melting of the surface are presented. Two degradation mechanisms have been identified, one of which causes the formation of a thin near-surface layer of modified nonstoichimetric gallium arsenide at a power level higher than 1×10⁷ W/cm² and the other of which causes the formation of a separate gallium phase. The formation of the separate gallium phase can be produced either by a single pulse of laser radiation with a power density exceeding 2.7×10¹¹ W/cm² or by a few less powerful pulses. An empirical relationship has been established between the power density and the number of pulses causing the formation of the separate gallium phase. It has also been established that as a result of laser irradiation at the boundary of “cold” and “hot” gallium arsenide, periodically ordered defects in the form of blocks aligned along the [100] directions emerge.     

Changes in the chemical state and concentration of iron in carbon nanotubes obtained by the CVD method and exposed to pulsed ion irradiation

Data on the distribution of iron in nitrogen-containing multiwall carbon nanotubes (N-MWCNTs) and changes in its chemical state and concentration under different parameters of irradiation by a pulsed ion beam are obtained by methods of transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersion analysis. It is shown that the irradiation of N-MWCNTs with an energy density of 0.5 J/cm² lead to the formation, on their lateral surfaces, of structures with a size of 2–10 nm, consisting of metallic iron encapsulated in a carbon shell. An increase in the energy density to 1–1.5 J/cm² leads to a substantial removal of iron clusters from the tips of carbon nanotubes and a reduction in the amount of iron in the bulk of the N-MWCNT layer.

     

High-power module based on inert gas–halogen mixtures for UV irradiation

We have developed a module based on exciplex barrier-discharge lamps for irradiation by high-power narrow-band ultraviolet radiation. The module uses air cooling and is intended for irradiation of substrates such as those used in microelectronics. The module provides close to uniform irradiation on a flat surface with power density up to 35 and 25 mW/cm² as a result of emission in B–X bands of the molecules XeBr^* (282 nm) and XeCl^* (308 nm) respectively.     

Validity of reciprocity rule on mouse skin thermal damage due to CO2 laser irradiation

CO₂ laser (10.6 μm) is a well-known infrared coherent light source as a tool in surgery. At this wavelength there is a high absorbance coefficient (860 cm^?1), because of vibration mode resonance of H₂O molecules. Therefore, the majority of the irradiation energy is absorbed in the tissue and the temperature of the tissue rises as a function of power density and laser exposure duration. In this work, the tissue damage caused by CO₂ laser (1–10 W, ～40–400 W cm^?2, 0.1–6 s) was measured using 30 mouse skin samples. Skin damage assessment was based on measurements of the depth of cut, mean diameter of the crater and the carbonized layer. The results show that tissue damage as assessed above parameters increased with laser fluence and saturated at 1000 J cm^?2. Moreover, the damage effect due to high power density at short duration was not equivalent to that with low power density at longer irradiation time even though the energy delivered was identical. These results indicate the lack of validity of reciprocity (Bunsen-Roscoe) rule for the thermal damage.     

B<Subscript>4</Subscript>C protective coating under irradiation by QSPA-T intensive plasma fluxes

The effect of the QSPA-T pulsed plasma irradiation on the crystalline boron carbide B₄C coating was examined. The duration of the rectangular plasma pulses was 0.5 ms with an interval of 5–10 min between pulses. The maximum power density in the central part of plasma stream was 1 GW/m². The coating thickness varied from 20 to 40 μm on different surface areas. Modification of the surface layers and transformation of the coating at elevated temperature under plasma pulse irradiation during four successive series of impulses are described. It is shown that the boron carbide coating withstood the full cycle of tests under irradiation with 100 plasma pulses with peak power density of 1GW/m². Constitutive surface deterioration was not detected and the boron carbide coating kept crystal structure B₄C throughout the irradiation zone at the surface depth no less 2 μm.     

Effectiveness of ultrasound for the destruction of Mycobacterium sp. strain (6PY1)

Ultrasound is widely used to disinfect drinking water and wastewater due to its strong physical and chemical effects on microorganisms. The aim of this study was to investigate the effect of ultrasound on the destruction of Mycobacterium strain 6PY1. Ultrasound waves (20 kHz or 612 kHz) were used to treat aqueous suspensions of Mycobacterium at different volumes, initial bacterial concentrations, and power densities. At the same power density and the same exposure time, sonication at high frequency resulted in a lower destruction of Mycobacterium sp. 6PY1 (35.5%) than sonication at low frequency (93%). The percentage of removal was not significantly affected by the volume of the irradiated suspension (150–300 ml) or the initial cell concentration (2.15 × 10⁻³–1.4 × 10⁻² mg protein L⁻¹). At low frequency, the removal percentage of Mycobacterium sp. 6PY1 increased with increasing the power density, with a constant level reached after a certain power density. At high frequency, the removal percentage of Mycobacterium sp. 6PY1 increased with increasing the power density. The mechanism of cell killing was investigated by examining the effects of OH radical scavengers such as sodium carbonate. At high frequency the presence of sodium carbonate suppressed the removal process. However, at low frequency the removal process was not affected, thus indicating that OH radicals have a negligible role in this case. The latter result was supported by ten time’s H₂O₂ production at high frequency greater than that at low frequency.     

质子辐照对纯铝薄膜微观结构的影响

利用透射电子显微镜(TEM)详细分析了不同剂量的质子辐照纯铝薄膜样品的微观结构, 质子的能量E=160 keV.实验表明,质子辐照能够在Al薄膜中诱发空位位错圈,在实验范围内,位错密度随辐照剂量的增加而增加;质子辐照在1×10¹¹—4×10¹¹/mm²范围内随辐照剂量的增加,位错圈数量密度以及位错圈尺寸都随之增加.在较高剂量6×10¹¹/mm²辐照下,位错圈数量密度减小,但其尺寸显著 关键词： 质子辐照 空位簇缺陷 位错圈 微观结构     

Synergistic effect of sonication on photocatalytic oxidation of pharmaceutical drug carbamazepine

Photocatalytic, sono-photocatalytic oxidation of pharmaceutical drug of carbamazepine was successfully carried out using Ag/AgCl supported BiVO₄ catalyst. For this purpose, firstly, photocatalytic oxidation was optimized by central composite design methodology and then synergistic effect of sonication was investigated. Low frequency (20 kHz) probe type and high frequency (850 kHz) plate type sonication at pulse and continuous mode were studied to degrade the carbamazepine (CBZ) containing wastewater. Pulse duties of 1:5 and 5:1 (on : off) were tested using the high frequency sonication system in the sono-photocatalytic oxidation of CBZ. The effects of frequency, power density measured from calorimetry by changing amplitudes were discussed in the sono-photocatalytic oxidation of CBZ. Complete carbamazepine removal was achieved at the optimum conditions of 5 ppm CBZ initial concentration with 1.5 g/L of catalysts loading and at an alkaline pH of 10 at the end of 4 h of photocatalytic reaction under visible LED light irradiation. Both low frequency and high frequency sonication systems caused an increase in photocatalytic efficiency in a shorter treatment time of 60 min. CBZ removal increased from 44% to 65.42% in low frequency sonication of 20 kHz at the amplitude of 20% (0.15 W/mL power density). In the case of high frequency ultrasonic system (850 kHz), CBZ removal increased significantly from 44% to 89.5 % at 75% amplitude (0.12 W/mL power density) within 60 min of reaction. Continuous mode sonication was observed to be more effective than that of pulse mode sonication not only for degradation efficiency and also for electrical energy consumption needed to degrade CBZ. Sono-catalytic oxidation was also conducted with simulated wastewater that contains SO₄^2-, CO₃^2–, NO^3–, Cl^- anions and natural organic component of fulvic acid. The CBZ degradation was inhibited slightly in the presence of NO₃^– and Cl^-, and fulvic acid, however, the existence of SO₄^2- and CO₃^2– increased the degradation degree of CBZ. Toxicity tests were performed to determine the toxicity of untreated CBZ, and treated CBZ by photocatalytic, and sono-photocatalytic oxidations.     

Investigation of the irradiation effect on erbium-doped fiber amplifiers composed by different density erbium-doped fibers

Two erbium-doped fibers (EDFs) with different densities, which can make the erbium-doped fiber amplifier (EDFA) achieve the same output power, have been irradiated by ⁶⁰Co at the same rate and same total dose. In addition, the irradiation effect on EDFA composed by different density EDFs is firstly analyzed in this paper. The experimental results indicate that, considering the length of EDF, the high density EDF can make the EDFA deteriorate less than the low that in the irradiation environment. Furthermore, the small change of the central wavelength and the half-wave width also confirm that the irradiation effect on EDFA chiefly introduces the transmission loss, but the physical mechanics of EDFA is not changed by the irradiation. The experimental results and conclusions will be a good reference for EDFA designers who are trying to apply the EDFA in an irradiation environment.     

红外激光对可见光CCD成像系统的干扰

采用连续波红外激光对可见光面阵CCD成像系统进行了干扰实验,观察到饱和串扰、全屏饱和等干扰现象,并测到串扰阈值小于2.0×102W/cm2,全屏饱和阈值为1.2×104W/cm2。通过分析CCD输出电压、视频信号,提出基于有效干扰面积的干扰效果评估方法,并利用该方法对干扰面积与激光功率密度、辐照时间之间的关系进行了半定量分析。结果显示:激光功率密度对干扰效果的影响较大,而辐照时间在0.5~2.0 s之间时,辐照时间对CCD干扰效果的影响不明显。     

Tritium recovery from co-deposited layers using 193-nm laser

Recovery of tritium from co-deposited layers formed in deuterium–tritium plasma operations of the TFTR (Tokamak Fusion Test Reactor) was investigated by the use of an ArF excimer laser operating at the wavelength of 193 nm. At the laser energy density of 0.1 J/cm², a transient spike of the tritium-release rate was observed at initial irradiation. Hydrogen isotopes were released in the form of hydrogen-isotope molecules during the laser irradiation in vacuum, suggesting that tritium can be recovered readily from the released gases. In a second experiment, hydrogen (tritium) recovery from the co-deposited layers on JT-60 tiles that had experienced hydrogen-plasma operations was investigated by laser ablation with a focused beam of the excimer laser. The removal rate of the co-deposited layers was quite low when the laser energy density was smaller than the ablation threshold (1.0 J/cm²), but reached 1.1 μm/pulse at the laser energy density of 7.6 J/cm². The effective absorption coefficient in the co-deposited layers at the laser wavelength was determined to be 1.9 μm^-1. The temperature of the surface during the irradiation at the laser energy density of 0.5 J/cm² was measured on the basis of Planck’s law of radiation, and the maximum temperature during the irradiation decreased from 3570 K at the initial irradiation to 2550 K at the 1000th pulse of the irradiation. Received: 5 August 2002 / Accepted: 7 August 2002 / Published online: 28 October 2002 RID="*" ID="*"Corresponding author. Fax: +81-29/2825917, E-mail: shu@tpl.tokai.jaeri.go.jp     

Transport of metals in Si by the thermal effect of continuous CO2 laser radiation

The influence of the local thermal effect of continuous CO₂ laser radiation with a power density as high as 10³ W/cm² on metal-Si films is investigated. It is discovered that the structural defects formed as a result of irradiation influence the transport of the metal in Si. Zh. Tekh. Fiz. 69, 135–137 (October 1999)     

Theoretical and experimental investigation of desalting and dehydration of crude oil by assistance of ultrasonic irradiation

In this paper desalting/dehydration process of crude oil by ultrasonic irradiation in a novel batch standing-wave resonator reactor is studied both theoretically and experimentally. The effect of main parameters including ultrasonic irradiation parameters, namely irradiation input power and irradiation time, and also operating parameters, such as temperature and injected water, on the removal efficiencies of salt and water is examined. The obtained results demonstrate that finding the optimum values of the above mentioned parameters is important to prevent a significant decrease in the removal efficiencies of water and especially salt. Thus, crude oil was subjected to optimal ultrasonic irradiation with an input power of 57.7 W, and irradiation time of 6.2 min at temperature of 100 °C. The injected water to dissolve the salt of crude oil was 7 vol.%. Also, the applied settling time and dosage of chemical demulsifier were 60 min and 2 ppm, respectively. Under these optimum conditions the removal efficiencies of the desalting/dehydration process were 84% and 99.8%, respectively, which are suitable for refineries.Also, based on the optimal experimental data, two inferential estimators are developed to obtain the relationships between the salt and water removal efficiencies, and input energy density. These empirical relationships can offer a proper estimation for the salt and water removal efficiencies with irradiation input energy.     

Removal of carbamazepine from aqueous solution using sono-activated persulfate process

This study investigated systematically the removal of carbamazepine (CBZ) in solution using the combination of ultrasound and persulfate anions to identify the factors affecting the kinetics of the process. The effects of reaction time, initial persulfate anion concentration, initial CBZ concentration, ultrasonic power input, solution pH and temperature on CBZ removal efficiency were examined. The sulfate radical oxidation of CBZ in the presence of ultrasonic irradiation showed a significant synergistic effect on CBZ removal. It is found that up to 89.4% CBZ removal efficiency was achieved after 120 min reaction. The removal process of CBZ in solution could be described using pseudo-first-order kinetics. In this system, sulfate radicals (SO₄⁻) were considered to be the mainly oxidant to remove CBZ while ultrasound power input could affect CBZ removal efficiency significantly. Changing solution pH influenced the CBZ removal efficiency and the best performance would be achieved at pH 5.0.     

Interaction of the radiation of the high-power ytterbium-fiber laser with inhomogeneous dielectric targets

The action of the radiation of the ytterbium-fiber laser (λ = 1.07 μm) on the Nd³⁺Y₂O₃ target with nonuniform transparency in the course of the nanopowder production is studied. It is demonstrated that the laser irradiation leads to an extremely rough surface with the stalagmite roughness due to a relatively large melting depth. The resulting powder consists of two fractions. The first fraction (99% of the total mass of the powder) consists of nanoparticles with a mean size of 29 nm (BET data). The second fraction consists of micro- and submicroparticles that represent circular drops condensed from the melt and shapeless debris of the target. The peaks on the diameter distribution of the drops at 2, 8, and 80 μm are determined by different effects. The laser heating of the inhomogeneous target with the nonlinear refractive index is numerically analyzed. It is demonstrated that the melting of the target is initiated at a mean laser power of 700 W, a power density of 5.6 × 10⁵ W/cm², and an irradiation time of 150 μs.     

Effects of irradiation parameters on metal surface erosion by pulsed ion beams

Potential application of high-power ion beams of submicrosecond and microsecond durations with the initial particle energy from 50 to 1000 keV and power density 10⁷–10⁹ W/cm² to ensure metal surface erosion are investigated. Evaporation is treated as a major erosion mechanism and the erosion coefficient is taken as an efficiency indicator. Dependences of the erosion coefficients of several metals on beam parameters obtained via calculations using a technique based on the solution of thermal conductivity equation with phase transitions are presented. The ion species, their initial energy, current pulse duration and power density are used as the beam parameters controlling the result of irradiation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 49–54, August, 2007.