The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation have been investigated using a Sr(90)-Y(90) beta emitter as the electron source. Spectral emission curves of uv-grade, optical-grade, and electron-irradiated samples of MgF(2) and LiF, and of CaF(2), BaF(2), sapphire, fused silica, and uv-transmitting glasses were obtained over the 200-650-nm spectral range. Fluorescence yields, expressed as the number of counts in a solid angle of 2pi sr/MeV of incident electron energy deposited [MeV(-1) (2pi sr)(-1)], were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S-20) photocathodes, respectively. Typical yields observed with a uv/visible sensitive bialkali cathode range from 10 MeV(-1) (2pi sr)(-1) for uv-grade MgF(2) to approximately 200 MeV(-1) (2pi sr)(-1) for CaF(2). For comparison, sodium-activated cesium iodide, one of the most efficient scintillator materials, yields about 700 MeV(-1) (2pi sr)(-1). High-purity fused silica has the lowest yield, approximately 6 MeVW(-1) (2pi sr)(-1). Optical-grade MgF(2)and LiF, as well as electron-irradiated uv-grade samples of these two materials, show enhanced fluorescence due to color-center formation and associated emission bands in the blue and red wavelength regions. Large variations in fluorescence intensities were found in uv-grade sapphire samples of different origins, particularly in the red end of the spectrum, presumably due to various amounts of chromium-ion content. Phosphorescence decay with time is best described by a sum of exponential terms, with time constants ranging from a few minutes to several days. Phosphorescence intensity expressed as a fraction of the steady-state fluorescence intensity is an extremely sensitive measure of crystalline perfection and purity. This fraction ranges from a high of approximately 10(-2) for some fluoride samples to a low of

The effect of simulated Nimbus spacecraft orbital (1100 km, circular, and polar) radiation on wide-band-pass glass filters, narrow-bandpass thin-film interference filters, and several fused silicas was determined by transmittance measurements over the 200-3400-nm wavelength region. No changes were observed in the filters, which were shielded with fused silica during irradiation, after exposure to a 1-yr equivalent orbital dose of electrons, nor were changes observed in the fused silicas after the same electron exposure plus a 1-yr equivalent dose of protons. Exposure to a (1/2)-yr equivalent dose of solar uv radiation, however, caused a significant degradation in the transmittance of two uv-transmitting interference filters but had no effect on two colored glass filters that transmitted in the visible and near-ir regions. As a result of the uv exposure, the fused silicas exhibited losses of several percent over the 200-300-nm wavelength region.

An investigation was made of the effect of surface roughness on the oxidation rate of iron in air at 800~ Specimens of ingot iron were grit blasted to give surfaces of different textures. The roughened specimens were found to oxidize more slowly than as-rolled ones, the difference in rate becoming greater with increasing roughness. The as-rolled specimens oxidized parabolically with a certain rate constant at the beginning; however, with continued oxidation, roughness developed on the metal surface, and a change in the rate constant occurred. Specimens of high-purity iron with smooth surfaces, on the other hand, not only remained smooth throughout a 3-hr oxidation period, but they also oxidized parabolically with a single rate constant. It was found that the reduction in rate due to roughening was not caused by surface contamination or by surface cold work, but by voids that form in the scale layers on roughened surfaces. These voids apparently act as diffusion barriers for iron ions and, thereby, Iower the rate at which roughened specimens oxidize.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 152.14.136.77 Downloaded on 2015-03-18 to IP Vol. 109, No. 5 EFFECT OF ROUGHNESS complete study of the roughness effect was undertaken. The goals were twofold: i, to determine by controlled oxidation tests in air at a single temperature (800~ if the oxidation rate of iron specimens could, in fact, be reduced by roughening of the surface, and ii, if such a reduction was observed, to arrive at the most probable explanation for the reduction. The 800~ temperature was used because the study was a phase of an investigation concerned with ceramic-metal systems in which this particular temperature was of primary interest.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 152.14.136.77 Downloaded on 2015-03-18 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 152.14.136.77

A series of porcelain enamel ground coats of the same basic composition but with various amounts of cobalt oxide was fired on enameling iron in atmospheres consisting of various oxygen‐nitrogen mixtures. The effect of the oxygen content of the atmosphere on adherence was determined and the effect on interface roughness was estimated from an examination of metallographic cross sections. A decrease in the amount of oxygen in the firing atmosphere necessitated an increase in the amount of cobalt oxide in the enamel if optimum adherence was to be secured. Ground coats containing 3.2% cobalt oxide or more developed a weak but definite bond in oxygen concentrations as low as 0.02 mole %. A qualitative correlation was found between adherence and surface roughness regardless of the oxygen content of the firing atmosphere.

A probe assembly is described which permits the use of an electron microscope to irradiate materials with low energy (50–150 keV) electrons. The electron beam current produced by the microscope can be monitored quickly and accurately with this unit so that the irradiation rate can be closely controlled. Although developed for use in the Hitachi HU-11 electron microscope, the device can, with but minor modifications, be utilized in other microscopes as well.