An analysis of steady-state electron trajectories by simultaneous solution of the equation of motion and the dispersion relation (DR) for electromagnetic wave wiggler in free-electron laser (FEL) with axial magnetic field is presented. The effects of the normalized axial magnetic field and the normalized angular frequency of electromagnetic wave wiggler on axial and transverse velocity for group I and II orbits are investigated. A fluid model is used to obtain the DR for electrostatic wave and the right and the left circularly polarized electromagnetic waves with all relativistic effects included. This dispersion relation is solved numerically to investigation the unstable coupling among all waves. When the transverse velocity is small, only the FEL instability is found. In group II orbits, with large transverse velocity, new coupling between the negative and positive energy space charge waves as well as between the left circular wave and positive energy space charge wave are found.

Laser-induced spallation is a process in which a stress wave generated from a rapid, high-energy laser pulse initiates the ejection of surface material opposite the surface of laser impingement. Through knowledge of the stress-wave amplitude that causes film separation, the adhesion and interfacial properties of a film-on-substrate system are determined. Some advantages of the laser spallation technique are the noncontact loading, development of large stresses (on the order of GPa), and high strain rates, up to 108/s. The applicability to both relatively thick films, tens of microns, and thin films, tens of nm, make it a unique technique for a wide range of materials and applications. This review combines the available knowledge and experience in laser spallation, as a state-of-the-art measurement tool, in a comprehensive pedagogical publication for the first time. An historical review of adhesion measurement by the laser-induced spallation technique, from its inception in the 1970s through the present day, is provided. An overview of the technique together with the physics governing the laser-induced spallation process, including functions of the absorbing and confining materials, are also discussed. Special attention is given to applications of laser spallation as an adhesion quantification technique in metals, polymers, composites, ceramics, and biological films. A compendium of available experimental parameters is provided that summarizes key laser spallation experiments across these thin-film materials. This review concludes with a future outlook for the laser spallation technique, which approaches its semicentennial anniversary.

In this paper, the oblique propagation of the ion-acoustic quantum soliton in polarized quantum plasma including relativistic degenerate electrons and positrons is studied. By using the reductive perturbation method, we derived the ZK equation for this model. This equation shows that in presence of the negative ion there are two slow and fast ion-acoustic modes. Our numerical results indicate that there are only compressive and refractive solitons for fast and slow modes, respectively. The effect of the negative ion parameters on the amplitude and width of the ion-acoustic quantum soliton are studied, as well.

In this experimental work, we have studied induced changes in refractive index, extinction coefficient, and optical band-gap of Bisphenol-A-polycarbonate (BPA-PC) coated with a uniform and thin, anti-scratch SiO2 film irradiated by visible to near-infrared lasers at 532 nm (green), 650 nm(red), and 980 nm (IR) wavelength lasers with different energy densities. Our lasers sources are indium-gallium-aluminum-phosphide, second harmonic of neodymium-YAG-solid state lasers and gallium-aluminum-arsenide-semiconductor laser. The energy densities of our sources have been changed by changing the spot size of incident laser. samples transmission spectra were monitored by carry500 spectrophotometer and induced changes in optical properties are evaluated by using, extrapolation of the transmission spectrum through Swanepoel method and computer application

Propagation and Interaction of Electrostatic and Electromagnetic Waves in Two Stream Free Electron Laser in the Presence of Self-Fields

In this paper, an analysis of equilibrium orbits for electrons by a simultaneous solution of the equation of motion and the dispersion relation for electromagnetic wave wiggler in a free-electron laser (FEL) with ion-channel guiding has been presented. A fluid model has been used to investigate interactions among all possible waves. The dispersion relation has been derived for electrostatic and electromagnetic waves with all relativistic effects included. This dispersion relation has been solved numerically. For group I and II orbits, when the transverse velocity is small, only the FEL instability is found. In group I and II orbits with relatively large transverse velocity, new couplings between other modes are found.

The surface modification of polycarbonate (PC) by 193 nm ArF laser radiation with fluences of 24–62 mJ/cm 2 and pulse numbers of 1–100 is reported. Noticeable changes including microcone structures on irradiated surfaces have been observed through scanning electron microscope (SEM). It has been shown that the geometrical characteristics (apex angle and base diameter) of the microcones depend on the incident laser fluence. With the increase of the radiation fluence the microcone apexes become sharper, however, their base diameters increase.

Electron motion in the combined ion-channel, helical wiggler and axial magnetic fields is analyzed in the absence of a radiation field. Detailed analysis of the gain equation in a free-electron laser is presented. Numerical calculations are made to illustrate the effects of the two electron-beam guiding devices on the gain when applied separately and simultaneously.

Photoinduced birefringence in PMMA-DSR1 system has been investigated using Nd3+-YAG pulsed laser with wavelength of 532 nm which is in the near resonance with absorption line of trans isomer of azobenzene molecules. The effects of parameters such as pumping intensity, pulse repetition rate in the induced birefringence have been studied, using a probe He-Ne laser.

The purpose of this paper is to provide mathematical expressions for the duration and convexity of a convertible preferred stock. In general, the duration of a convertible preferred stock is the product of the Macaulay duration for a pure preferred stock and an elasticity measure that relates the convertible's price to the price of its straight preferred component. Convexity has two parts. The first is based on the convexity of the pure preferred element, while the second is predicated on the gamma coefficient of the embedded call option.

In this paper, we report on the atomic layer epitaxy (ALE) of CdTe on GaAs and Si by the organometallic vapor phase epitaxial process at atmospheric pressure. Self-limiting growth at one monolayer was obtained over the temperature range from 250°C to 320°C, under a wide range of reactant pressure conditions. A study of growth mechanism indicates that DMCd decomposes into Cd on the surface and the Te precursors react catalytically on the Cd covered surface. We have used this ALE grown layer to improve the crystal quality and the morphology of conventionally grown CdTe on GaAs. Improvement in the crystal quality was also observed when ALE CdTe nucleation was carried out on Si pretreated with DETe at 420°C. Atomic layer epitaxy grown ZnTe was used to obtain (100) oriented CdTe on (100) silicon.