Table of contents

A brief account of the range of a three-day teaching seminar on the scope of neutron diffraction is given. The following one-day conference receives no technical summary, but the point is made that such events now easily become European in character.

Its objective was to compensate for the lack of a general textbook on inelastic scattering in particular.

A brief survey is given of some of the highlights of the 1962 Kyoto International Conference on Lattice Defects.

A series of measurements, extending over a year, was made at Enfield, Middlesex, using a grating monochromator to determine the spectral energy distribution of daylight between 3000 and 8000 Å, particularly of total sky radiation without direct sunlight. The results are considered with respect to the structure of the curves, their equivalent chromaticities and the related full radiator distributions. Average distributions are given for several daylight sources including those at the limits of the usual range of chromaticities used in colour matching. From these, specifications for real or artificial daylight at any intermediate colour temperature can be set up. The values so obtained are more realistic than the theoretical data of the Abbot-Gibson formulation.

The friction coefficient μ and the mass wear rate M during abrasion of a brittle material in single crystal form (rocksalt, cube face cleavage) are studied quantitatively as functions of the abrasive particle diameter D at load 0.5 kg. μ on emery papers coarse enough to avoid clogging is constant, μ_max. This, and the fact that μ_max is about the same as for a metal of similar hardness, indicates that μ is determined essentially by the plastic flow properties, and scarcely at all by the extensive brittle fractures which occur in addition to the plastic flow, near the grooves ploughed out by the abrasive particles. The wear, however, is greatly increased by the cracks and fractures.

Three types of (M, μ) relationship are observed, in different ranges of depth of indentation of the abrasive particles. For less than 0.5 μm depth, fracture appears to be practically absent, plastic flow predominates and the (M, μ) relation is about the same as for metals. At deeper indentations a linear (M, μ) relation occurs but with greatly increased wear. Finally, at depths greater than 5 μm, the wear rate increases strongly without much further increase in μ, showing the greatly increased spread of fractures around the indenting particles.

A modified theory of friction and wear in abrasion of such brittle solids is developed.

The migration of metal from the anode to the cathode and that from the cathode to the anode of an electrical contact have been measured over a range of low circuit inductance extending down to values of the order of 10^-8 H. The method depends upon making one electrode radioactive and assessing the quantity of material from this electrode deposited on the other by operating the contact. The contact metals considered are silver, platinum and platinum-iridium alloys. Even at the lowest values of inductance, the transfer of metal depends on the inductance. This indicates the decisive role played by the micro-arc which occurs at the breaking of the contact.

The fluorescence emission spectra of toluene solutions of seven efficient scintillator solutes (TP, QP, TPB, DPH, DPA, PPO and POPOP) have been measured with a recording photoelectric spectrophotometer at a resolution of about 8 Å. The fluorescence was excited mainly by 2537 Å radiation from a low pressure mercury lamp with filters. Self-absorption effects were studied using different solution depths and concentrations.

Thin films of collodion and Canada balsam have been prepared on water surfaces. Their thickness has been evaluated interferometrically over the range ½-1/50 λ and the relation between concentration and thickness studied. The effect of temperature on film thickness has been evaluated at 25, 100 and 150° C.

The re-emission of ionically pumped argon in a glass diode ion pump, when bombarded with the other inert gases He, Ne, Kr and Xe, has been studied. It was found that the removal efficiency increases to an apparent saturation with increasing bombarding ion energy, but even at the highest bombarding energy used (1 kev) it was never possible to recover completely all sorbed primary gas. This and other evidence leads to the conclusion that argon is released from the glass by transfer of sufficient energy by a bombarding ion, via the glass atoms, to the sorbed argon: sputtering of the glass with simultaneous argon release appears to be unimportant. The effective gas sputtering coefficients for argon releasing argon and the maximum possible surface coverage are deduced.

Measurement of the rapid growth of current in an overvolted gap has been used to determine formative time lags. Curves of formative time lag against percentage overvoltage are presented, and a method of determining electron drift velocities is discussed.

The variation of the brightness of electroluminescent emission of ZnS (Cu) phosphors prepared by iodine transport is discussed. Whereas the blue emission varies linearly with frequency the green and red emissions vary as the half power of frequency.

The Joshi effect is shown to exist in an electrodeless discharge in air when a central wire emits electrons. This is compared with the effects observed when irradiation is produced by ultra-violet or visible light.