Automatic output-beam-collimating configuration for high-average-power multirod resonator-amplifier systems

A novel configuration for a multirod solid-state laser system is proposed. We stabilize the thermal-lens-dependent variation in the output-beam parameters by extracting the laser beam from the collimating point of periodic beam propagation. The performance is confirmed with a 100-W class diode-pumped Nd:YAG laser-amplifier system to demonstrate tenfold stabilization of the output-beam diameter.     

Development of a 2-kW XeCl laser with a surface coronapreionization scheme and a spiker-sustainer circuit

A maximum average power of 2.1 kW is demonstrated in a XeCl laser with an efficiency of 3.0% at a repetition rate of about 800 Hz. The 2-kW laser has a discharge region of 4 cm in gap length, 2.5 cm in discharge width, and an effective discharge length of 3 m with a resonator length of 5.2 m. A reverse voltage mode spiker-sustainer circuit makes it possible to apply a steep voltage rise of nearly 1000 kV/μs across the main discharge electrodes and to supply excitation energy effectively into the discharge region. The control of the preionization timing before the initiation of the spiker circuit is found to be indispensable in maintaining a homogeneous volume discharge under high repetition-rate operation. These techniques enable the laser to realize a long pulse excitation under the high repetition-rate operation conditions. The excitation process is analyzed by computer-model simulation. The application of a cascaded stable resonator has improved the average power by 6% compared with that of a conventional stable resonator     

The Effects of Small Additions of Yttrium on the High-Temperature Oxidation Resistance of a Si-Containing Austenitic Stainless Steel

The oxidation characteristics of a 19Cr–10Ni–1.5Si alloy with and without 0.03Y have been examined using scanning-electron microscopy, secondary-ion mass spectroscopy and transmission-electron microscopy. Y has been found to segregate to oxide grain boundaries and thereby to inhibit outward-cation diffusion and promote the internal oxidation of Si. The synergism between the beneficial effects of Y and Si is described, and the results are discussed in relation to the de-oxygenating and de-sulphurizing influences of Y in steel production.     

Steam absorption into films of aqueous solution of LiBr flowing over multiple horizontal pipes

The absorbers of absorption chillers consist of horizontal tube banks, over the outer surfaces of which absorbent flows and inside of which cooling water runs. The dependence of the distribution of absorption rate on the position of the pipes is important but has not been studied previously. In this paper, the cases of one to three pipes are studied experimentally in the range of film Reynolds numbers between 5 and 40. Three different surfaces are tested to study the effect of wettability. Numerical calculations are also performed using the method proposed in our previous paper. The highest absorption rates are obtained for the pipes with higher knurls, and their distributions agree with the numerical predictions. The pipe position which shows the maximum absorption rate varies with flow rate but the maximum absorption rate does not vary greatly with flow rate. The heat transfer coefficient is minimum and almost constant with flow rate at the top pipe. At lower pipes it becomes larger, but tends to decrease with increasing flow rate. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 476–485, 1996     

Theory of EELFS compared with EXAFS for catalysis study

We discuss the similarity and the difference between EXAFS and EELFS for catalysis study based on the theory developed by the present authors. The information obtained from small-and large-angle scattering EELFS is quite different, and the former setup is recommended for catalysis study.     

Screening of long-wavelength laser at high temperature and high current levels

It is found that electroluminescent mode aging at high-temperature and high-current levels is useful for selecting long-lived InGaAsP 1.3 ?m lasers. Lasers selected by this screening have little change in threshold current or forward voltage through the aging test at an elevated temperature with constant light-output power.     

Diffusion of silicon in aluminum

Interdiffusion coefficients in Al-Si alloys were determined by Matano’s method in the tem-perature range from 753 to 893 K with the couple consisting of pure aluminum and an Al-Si alloy. Temperature dependence of the impurity diffusion coefficients of Si in Al, obtained by extrapolation of the concentration dependence of the interdiffusion coeffi-cient to zero mole fraction of Si, is given by the following equation: DSi/Al = (2.02^+0.97 _-0.66 × 10^-4 exp [-(136 ±3) kJ mol^-1/RT] m²/s. p ] The Kirkendall marker was found to move toward the Si-rich side, indicating that the Si atom diffuses faster than the Al atom in Al-Si alloys. From the interdiffusion coeffi-cient and the marker shift, the intrinsic diffusion coefficients were calculated. The difference in the activation energies (ΔQ) between the impurity diffusion of Si in Al and the self-diffusion of Al was estimated by means of the asymptotic oscillating po-tential and the Le Claire theory. The calculated value of ΔQ is in fair agreement with the experimental value. The vacancy-solute binding energy for Si in Al was also dis-cussed based on the diffusion data. formerly Undergraduate Student, Tohoku University