Effect of Neodymium Laser Pulses of Nanosecond Duration on Brown Coal

Journal of Applied Spectroscopy - The stages involved in the evaporation and ignition of brown coal under the influence of nanosecond laser pulses on tablets of brown coal of density 1 g/cm3 and...     

Luminescence From Minerals Excited by Subnanosecond Pulses of Runaway Electrons Generated in an Atmospheric-Pressure High-Voltage Discharge in Air

The duration of the luminescence from minerals excited by low-current subnanosecond pulses of runaway electrons generated in an atmospheric-pressure high-voltage discharge in air at high overvoltages was used to characterize specific minerals. Advantages of using an atmospheric-pressure air discharge as the electron source versus the use of evacuated acceleration tubes are discussed. The luminescence-duration measurement is a simpler approach as compared to other methods that are conventionally employed in the elemental analysis of minerals. PACS: 52.80.-s; 52.80.Tn; 52.80.Yr; 78.60.Hf; 91.60.Mk.      

High-Efficiency Relativistic Generators of Nanosecond Pulses in the Millimeter-Wavelength Range

Radiophysics and Quantum Electronics - We propose and study a scheme of a microwave pulse generator operating in the frequency ranges near 37 and 73 GHz, in which the electron interaction with both...     

Ultraviolet Luminescence of Microorganisms and DNA Excited by Nanosecond Laser Pulses

Studies of the luminescence of Bacillus thuringiensis spores and DNA of chickenblood erythrocytes are presented. Luminescence was excited by pulse-periodic ultraviolet laser radiation with duration of a separate pulse of 20 ns. The decay kinetics of luminescence and changes in the shape of the luminescence spectrum are considered. Noticeable changes in the photoluminescence spectra with delay in the registration system are detected. For a pulseperiodic mode of excitation, exciton–exciton quenching of luminescence in bacterial and DNA suspensions is observed. Studies of the influence of the geometrical shape of the cell on the photoluminescence spectra are performed.     

A Study of the Influence of Irradiation of Carbon Diamond-Like Coatings with Nanosecond Laser Pulses on Their Structural-Phase Composition and Tribological Properties

Russian Physics Journal - Using the methods of Raman spectroscopy, optical metallography and scanning electron microscopy, combined with the measurements of tribological characteristics, special...     

飞秒和纳秒激光脉冲作用下等离子体X射线辐射特性

对飞秒和纳秒激光作用下的Ａｌ和Ｃｕ等离子体的Ｘ射线辐射进行了测量、分析和比较．实验结果表明在飞秒激光脉冲下等离子体Ｘ射线峰值向短波方向移动．同时Ａｌ等离子体的的电离阶数和温度在飞秒下比纳秒高．     

Compression of Nanosecond Pulses upon Reflection from a Thermally Nonlinear Medium

We consider a boundary-value problem for nonlinear total internal reflection of laser pulses from a semi-infinite thermally nonlinear medium. Numerical modeling of the pulse forming upon reflection under the conditions of interaction of counter-propagating waves in a scheme with a retrodirective mirror has been carried out the approximation of noninterfering pulses, the possibility of controlling the shape and compression of the pulse in the nanosecond range of durations has been shown. The results obtained are in qualitative agreement with the known experimental data.     

Effect of Doping on the Properties of Hydrogenated Amorphous Silicon Irradiated with Femtosecond Laser Pulses

A comparative analysis of the effect of femtosecond laser irradiation on the structure and conductivity of undoped and boron-doped hydrogenated amorphous silicon (a-Si: H) is performed. It is demonstrated that the process of nanocrystal formation in the amorphous matrix under femtosecond laser irradiation is initiated at lower laser energy densities in undoped a-Si: H samples. The differences in conductivity between undoped and doped a-Si: H samples vanish almost completely after irradiation with an energy density of 150–160 mJ/cm².     

Diagnostics of Radiative Processes in Semiconductors,Excited by Ultrashort High-Voltage Pulses

A configuration of the multichannel system for diagnostics of radiative processes in various regions of the discharge appearing in semiconductors in response to high-voltage pulses is considered. The system allows real-time recording of spectra, dynamics, and energy of radiation in nine emitting object zones 200–400 μm in diameter. The recording equipment is connected to objects under study by fiber-optic cables (FOCs). The system temporal resolution can be varied from 40 to 250 ps depending on the FOC diameter. An example of the simultaneous study of spatiotemporal characteristics of the streamer discharge at seven points of a CdS _x Se_1?x semiconductor wafer is given.     

Effect of the Power-Frequency Electromagnetic Field on the Physicochemical Properties of Aluminum Micro- and Nanopowders

Technical Physics - The effect of power-frequency (50 Hz) electromagnetic field on variation in the physicochemical properties of aluminum powders with different dispersities is studied. It is...     

Cumulation of a High-Current Electron Beam During a Nanosecond High-Voltage Discharge in a Low-Pressure Diode

Russian Physics Journal - The results of an experimental investigation of the effect of cumulation of a beam of runaway electrons formed in a high-voltage nanosecond discharge at a reduced air...     

Diffraction of Acoustic Compression–Tension Pulses Generated by High-Density Nanosecond Electron Beam in Solids

Propagation of longitudinal acoustic signals through a D16T aluminum alloy, polycrystalline copper, and single-crystalline silicon was studied experimentally by laser interferometry. An asymptotic differentiation phenomenon was revealed in the acoustic signal in the transition from the near to the far wave field. Our experimental data analysis and theoretical calculation are indicative of the diffraction character of the phenomenon.     

Effect of Surface Plasma on Nanosecond Laser Ablation

For the first time, the effect of target surface plasma on nanosecond laser ablation is studied. Surface plasma was generated by a high-power cw fiber laser beam incident on an iron target. A comparison of laser ablation by nanosecond Nd:YAG laser pulses (1064 nm, 5 ns) was performed upon exposure to the cw laser and during its short-term (5 ms) turn off. It was found that the emission intensity twofold increases in the presence of surface plasma. The temperature and electron density of the laser plume induced by the nanosecond laser also increased.     

Transformation of Nanosecond Laser Pulses under the Conditions of Total Internal Reflection from a Layer with Thermal Nonlinearity

The nonlinear, total internal reflection of a laser pulse from an absorbing layer of finite thickness in the presence of a retrodirective mirror has been considered in the framework of the plane-wave approximation. The dynamics of reflection of a pulse from a nonlinear layer has been investigated on the basis of the solution of Maxwell equations for a refracted wave and constitutive equations for a medium with thermal nonlinearity. The numerical solution of the unsteady equations obtained allows one to determine the evolution of the reflectance of a layer. The time evolution of the energy parameters and the shape of the reflected and transmitted pulses has been numerically simulated.     

Effect of Stimulated Radial Scattering Accompanied by Excitation of Converging Acoustic Waves in Optical Media Pumped by High-Power Nanosecond Pulses with Broad Spectrum

Optics and Spectroscopy - The mechanism of stimulated radial scattering and caused by it specific damage in surface layers of optical media revealing itself most prominently in media characterized...     

Increase of Kinetic Energy of Dusty Cluster Particles Due to Parametric Instability Caused by Nanosecond Electric Pulses

Experimental investigations of high voltage nanosecond pulses influence on charged dust particles in low pressure rf–plasma were carried out. Application of repetitive pulses leads to the vertical oscillations of the mi‐croparticles. Evolution of the total kinetic energy for the cluster consisting of 14 particles is investigated. Flat clusters exhibit parametric instabilities of horizontal modes. In the initial phase the kinetic energy oscillates around a certain value and its amplitude grows very slowly. At a certain moment during the instability it goes into the exponential growth phase and then saturates under the effect of repetitive pulses. It is possible if the eigenfrequency is the function of height and the dust particle oscillates vertically in the non uniform electric field (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Properties of LBO and Generation of Mode-locking Blue Femtosecond Pulses

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Physicochemical Mechanisms of Nanostructuring of Glass by Femtosecond Laser Pulses with the Use of Selective Etching

JETP Letters - Processes occurring at nanostructuring of glass irradiated by tightly focused single femtosecond laser pulses with selective chemical etching in the alkaline solution have been...