Table of contents

The report deals with the papers presented at the above conference, attention being directed mainly to the new devices and circuits which were discussed. The topics covered include new magnetic devices for memory storage, digital logic and analogue-digital conversion, new semiconductor devices including field effect transistors and silicon tetrodes, opto-electronic devices, including a cuprous chloride light modulator, and several new circuits, both analogue and digital. Discussions on high frequency limitations of semiconductor devices, and the study of sensory elements are also briefly reported.

This article describes the techniques used for the isotopic and chemical analysis of solid materials employing the mass spectrometer as an analytical tool. It describes in detail the types of ion sources and detectors needed for this work, and reviews some of the more recent developments in these fields. Spark source mass spectrometry is discussed, and applications of the mass spectrometer to nuclear physics, isotope dilution, geology, thermodynamic studies and field ionization are discussed.

The relaxometer described enables changes in stress with time in a vulcanizate at a known extension to be measured automatically in a closed atmosphere or in a vacuum. Measurements may be made either with the sample continuously stressed (continuous relaxation) or stressed only for short periods at fixed time intervals (intermittent relaxation).

Mass discrimination is a variable and unpredictable source of systematic error in mass spectrometric analysis using surface ionization techniques. A method of eliminating it through an internal standard technique is investigated. To simplify the algebra a method of describing mass discrimination has been developed (equations (11)) which is symmetrical with respect to all isotopes in a sample. A set of equations for mixtures of samples with different isotopic compositions is set up and solved for elements with three or four isotopes, four isotopes giving the simplest solutions. The solutions can be applied to quantitative analysis by the isotopic dilution technique, to the measurement of absolute isotopic abundances and to the measurement of relative abundances of samples of polyisotopic elements which have undergone isotopic fractionation. To make the most of these proposals the precision of measurement of ion current ratios from thermal ionization sources must be improved.

The characteristics of a spark chamber containing a neon-alcohol mixture are described with particular reference to the variation of efficiency with the parameters of the pulse and the determination of the spark formation time. An interpretation of the characteristics is made on the basis of a model for spark formation and the validity of the mechanism is examined by an internal comparison of the data.

The results are used to derive the electron drift velocity as a function of field over the range of E/p from 0.05 to 4 v cm^-1(mmHg)^-1 and to determine the probability of a single electron initiating a spark.

Measurements are also reported on the geometrical properties of the sparks and conditions are studied both for minimizing the angle between the direction of a particle trajectory and the ensuing spark, and for reducing the error in location of the trajectory.

The atomizer, which is based on an electrically maintained vibrating hypodermic needle, is constructed for use within a steam atmosphere, and incorporates adjustments for varying the jet direction.

Using water in air it was found that for break-up into a single uniform stream of droplets three independent criteria were operative: (i) the accepted Rayleigh criterion, (ii) a criterion related to the resonant frequency of the vibrating system of the atomizer, and (iii) a criterion relating to the properties of the liquid under test.

The design of a bridge for determining, at various frequencies, the differential capacitance of the electrical double layer at a perfectly polarized dropping mercury electrode is described. The time interval between the birth of a mercury drop and the balance of the bridge is directly measured using pulses to trigger an electronic timer.

The apparatus described has been designed for measuring the total magnetic susceptibility in any one direction, and the orientations, but not the magnitudes, of the axes of anisotropic susceptibility in rocks. The method, a transformer bridge, has a limit of sensitivity of 5 × 10^-7 e.m.u. cm^-3. A description of the method of measurement is followed by a detailed description of the calibration.

A method of calibrating reflection interference microscopes is described and results for the variation of effective wavelength with aperture and wedge angle are given.

A variable retardation plate based on the photoelastic effect in fused silica is described. A rectangular plate of fused silica, held in a special frame, is subjected to a uniform stress across opposite edges. The stress is applied by direct screw pressure acting through liquid-filled plastic capsules, which distribute the pressure extremely uniformly. The plate is suitable for use in the visible, ultra-violet and near infra-red, and will give continuously variable retardation up to a half-wave in the visible. Drift in the initial setting is minimized by the provision of an air spring.

A description is given of a substitution bridge for the measurement of the complex permittivity of dielectric samples in a three-terminal electrode. Samples of capacitance 10 to 30 PF whose loss angle tan δ does not exceed 0.5 are measured with an error in tan δ of 5% ± 0.0001, over the frequency range 100 kc/s to 10 Mc/s.

A system is described which generates carrier signals to drive the three time signal transmitters of the Dominion Observatory radio station CHU and generates the time signal impulses and controls the modulation programme of the transmitters. The three carrier frequencies of 3.330, 7.335 and 14.670 Mc/s are synthesized from the signal supplied by a precision 100 kc/s quartz oscillator. The time signal impulses are developed from, and the modulation programme controlled by, the same oscillator by means of a phonic motor driven switching system and electronic gating circuits so that phase coherence between the radio-frequency carrier signals and the time signal impulses is maintained. The accuracy of the radio-frequency and time signals is held as closely as possible to the internationally agreed value for UT2.

The apparatus uses capacity gauges to measure cyclic strains of magnitudes between 0.1% and 50% in linear metal specimens. The stress-strain loop is displayed on a cathode-ray tube together with reference calibration points. An overall accuracy to better than 1% is achieved.

An attachment is described which permits the use of a single crystal goniometer head with the Philips powder camera (114.59 mm in diameter). Use of the attachment does not require any modification of the powder camera beyond removal of the cover. This device permits accurate determination of the Bragg angles of the reflections obtainable in a zero layer Weissenberg photograph with only small orientation corrections.

The design of a microscope stage cooled by a thermoelectric device is discussed. The temperature was stabilized near 0° C using the latent heat of fusion of ice.

Methods are described for the making of rubber objects of pre-vulcanized natural latex, These include dipping formers of suitable material in the latex and `painting' thin latex films on the formers. Removal techniques for limited numbers of specimens include using formers made up of different parts joined by screws which can be removed separately and employing a vacuum technique. Formers and vessels must be free from copper as this contaminates the products.

The design and use of a simple and inexpensive gauge is described which is suitable for thickness probing on fragile crystal platelets between 10 μm and 500 μm thick. It employs a miniature optical lever which gives an optical magnification of 10³, and the local crystal thickness can be determined to within 0.5 μm.

This specimen holder, made for a Norelco type x-ray diffraction goniometer for solid specimens, maintains a constant controlled atmosphere over the sample. The system is useful in studying the controlled oxidation of metallic surfaces.

A simple accessory for recording x-ray texture diagrams on a moving flat film is described. The accessory is easily fitted to a single-crystal oscillation camera, and the movement of the film is synchronized with the 15° oscillation of the sample. An example of such a texture diagram taken on a sample of native copper is shown.

In the fabrication of evaporated circuits it is often desirable to deposit different materials through different masks on to the same substrate, without breaking the vacuum. A jig has been designed for this purpose and is described.

The chief design feature is that the substrate is held in a fixed position and the appropriate mask is brought into contact with it. It is also arranged that all movement should be by rolling rather than by sliding, as the latter will result in the seizing up of surfaces.

Examples of circuits deposited by using the jig are mentioned.

A technique is described for sealing off metal tubes either under vacuum or with a positive pressure of an inert or reducing gas, using only hand tools.