Laser science has now entered in new era in many countries and the demand for appling this technique to industry is rapidly growing up in these days. Several applications are now being used for production, such as drilling of diamond, watch stones, ceramics, plastics, stainless steels and tungsten carbides, cutting of metals and non-metals, welding of small components .in watch and electronics industry, resistor trimming and ceramics scribing. The present situation of laser material processing not only in Japan but also in foreign countries are described.
Molecular beam investigations throw light to the dynamical character of adsorption on surfaces. In a collision between an atom (or molecule) and a surface the processes such as scattering (elastic, inelastic) and adsorption (perfect, imperfect) are possible. In this article a brief review is given on the recent development in the study of molecular beam scattering from solid surfaces. Recent studies of adsorption using metallic beams are also reviewed. The residence time on surfaces and the sticking coefficient are discussed from our point of view. A rate theory based on BET model is developed to interpret some sticking coefficient curves given in recent molecular beam experiments.
Establishment of accurate and reliable methods for estimation and measurement of the absorbed dose is an urgent need in using low-energy electron accelerators. For the purpose of giving a firm basis for the estimation of the absorbed dose, experimental investigations on transmission and backscattering have been made for electrons of energies most utilized in industrial applications, i. e. 200-400 keV. By using the results obtained, an empirical formula expressing the absorbed dose under a practical condition of irradiation parameters has been developed for the case of 300 keV electrons. In order to find a practical and reliable method of dosimetry, characteristics of various film dosimeters have been studied ; the characteristics considered are linearity of response, accuracy, and fading effect. Inaccuracy of optical measuring devices for films has also been revealed in this study. Preparation of a manual describing, standardized treatments in film dosimetry and centralized supply of films are considered to be necessary for the advance of irradiation engineering.
A laser interferometer, which uses the coupling effect between the laser cavity and an external one, is used here for measuring the time variation of the electron density simultaneously with its radial profile. Expansion rate of the laser beam while passing through the external cavity containing the plasma, whose radial electron density profile is approximated to be parabolic, is calculated by the ray transfer matrix. The relation between the amplitude decrement of the fringe pattern and the electron density profile is then deduced. The electron density on the axis and its radial profile are determined simultaneously from the observed fringe patterns for the afterglow plasmas in He and Ar at pressures of 4. 6 torr and 1.7 torr respectively, using a He-Ne laser at 3. 39 μm. The principle of the measurement is confirmed by measuring the electron density at 0. 5 cm from the axis.