Table of contents

The author examines the problems of X-ray flash production and its applications, similar to those of continuous X-radiation. Special problems are the fast production of high X-ray intensities to produce detectable radiation and the high-voltage and high-current discharge circuits required. Anode voltages from some 10 kV to about 1 MV and currents up to 10 kA are normal for laboratory equipment, but 100 MV and 1 MA are possible. The flash time is mostly between 10 ns and 1 mu s. Cineradiography with frame rates up to 10⁶ pictures s^-1 can be achieved.

The frequency and amplitude dependence of velocity-induced harmonics in thin-wire resistance thermometers are derived. The influence on the measured mean temperature and on the skewness is discussed.

Describes a simple sample holder which is constructed to reduce stresses placed on samples by thermal cycling.

A simple system is described which transfers information contained in photographic reproductions of structure models into digital form necessary for further computer evaluation. A transparent film is scanned by the light spot of an oscilloscope and the amount of light passing through the film is detected by a photomultiplier without optical imaging. Examples demonstrating the resolution of the system and its application in structure analysis are given.

The main construction features and salient operating characteristics of a lensless high-magnification high-resolution positive-ion transmission microscope are described. Evidence relating to resolution and transmission using positive hydrogen ions is given. Spatial resolution of 1-2 nm at 180000* direct magnification is achieved for opaque metal specimen edges.

A multiple-arc system using six separate arcs which appear to coalesce to form a large volume of ionised gas is described. Results of high-speed photographic techniques including an assessment of the effect of the persistence of luminosity are also given.

A 50 mm diameter furnace which fits in the gap of a magnet and has a temperature gradient of less than 10 degrees C m^-1 in the range 25-1600 degrees C is described. Its application in nuclear magnetic resonance measurements when the NMR frequency is strongly temperature-dependent is explained.

A simple digital-analogue lock-in circuit is described which is used to stabilise the frequency of a laser on the central frequency of a narrow fluorescence line at very low fluorescence intensities (about 10² to 10⁵ detected photons s^-1).

An automatic system to monitor temperature and humidity in biological exposure chambers is described. The temperatures are converted into proportional voltages which are fed into a microprocessor which controls the necessary steps to calculate the relative humidity. The calculations are performed on a mathematical model that relates relative humidity to dry and wet temperatures measured at a given pressure.

Describes an inexpensive TTL circuit for easy manual setting of stepper-motor-controlled devices.

A thermovoltage-controlled circuit is described which, in connection with a programmable power supply, permits controlled heating and flashing of specimens in ultra-high vacuum. With resistance-heated specimens the heating rate is variable over a wide range (2-50K s^-1). Although the circuit is designed for applications in flash desorption spectroscopy, it can be used for continuously adjusting sample temperatures up to 1500K.

A method for proper alignment of commercially available miniature wall shear probes for biomedical application is described. By means of a casting technique a probe body with a defined rotationally symmetric cross-sectional area is obtained, which can be inserted into a mounting bore.

The device described consists of two concentric cylinders with the outer one rotating, with Laminar Couette flow established within the gap. As the inner stationary cylinder holds the probes, the analytical determination of the shear stress at the wall of the inner cylinder allows the calibration of the probes.

A parametric preamplifier of the up-converting type is described for use with SQUIDS. The amplifier works in a self-oscillatory mode. The theory of its operation, including equations for gain and noise properties, is presented. The design and performance of a built amplifier are described and possible improvements in the results discussed.

A non-steady-state method for measuring the thermal conductivity and thermal diffusivity of transparent solids is described. A thin metal strip is pressed between two plane pieces of the material to be tested and, through electrical heating, works as a continuous plane heat source. The temperature distribution is monitored with uncollimated-beam interference, the experimental conditions of which are discussed in some detail. The method is tested on fused quartz and the accuracy and the internal consistency of the measurements are demonstrated.

The authors perform an evaluation of the usefulness of selected approximation methods to determine the complex frequencies of natural oscillations in cylindrical TE_01n cavities partly filled with highly dissipative material. The limitations of classical approximation methods, which are used for determining the relations between the parameters of the cavity and the complex permittivity of the sample, are shown.

A two-channel rapid-scanning polychromator is described which provides time and space resolution of visible-wavelength SF₆ arc emission lines. Use of a multiple-entrance-slit assembly and divided-fibre optics enables five sequential sets of side-on line profiles to be obtained spaced over 30 mu s. A novel method of polychromator exit slit construction and precision alignment is used, and the side-on data are digitised and stored prior to computer processing to obtain the instantaneous radial temperature profiles.

The choice of a computer suitable for general-purpose laboratory automation is discussed, with particular reference to those facilities which provide convenient and straightforward operation. A detailed design is presented for a versatile yet economical interfacing system for use with one particular computer. Its compatibility with other systems is briefly discussed, and an indication given of how the system may be modified to suit other processors.

A method is described in which the change of stored energy with deformation is measured. For determination of the dynamic energy balance of plastic deformation, metal single crystals are deformed by tension and the applied load, the effective deformation rate and the temperature of the specimen are measured with high precision during deformation.

The system described incorporates two pneumatically operated changeover valves, of a new design, with electrically heated capillaries in the dual-inlet system, which reduce the instrumental effects of this system to a negligible level. The changeover valves show many advantages such as high accuracy of closure, fast establishment of steady conditions after switching, simple construction and automatic control. Information on installation of stainless steel capillaries is also included.

The adaptation of inductive-resistive loads to explosive-driven generators by means of pulse transformers is discussed in practical terms. An analytical procedure for optimising the energy transfer is derived, and conditions are stated under which this is valid. Representative examples of generators, transmission lines and pulse transformers are given, including some experimental results on the performance of a helical/bellows generator capable of delivering 1 MA into 100 nH.

A new ENDOR cell is described which serves both microwave and RF irradiating functions. The strong RF magnetic field is created by a relatively small current and allows the study of free radicals in solution. This field is continuous and consequently the analysis of ENDOR spectra is facilitated. Another feature is that no modulation of the static magnetic field is required.

A simple technique is described whereby the reactive residuals of resistors may be accurately measured. It can be applied to individual, decade, or multi-decade resistance units. The method uses a precision dielectric cell containing an aqueous electrolyte as a standard of resistance parallel to capacitance. The principal advantage over conventional primary standards is the continuously adjustable nature of the cell impedance.

Describes a method for precise temperature measurements on thin vapour-deposited films, developed for magneto-optical Kerr studies of the critical magnetic behaviour of thin nickel films. The combination of a bulk platinum resistor and a thin-film Au-Pt thermocouple eliminates errors which usually occur if only one of these probes is used. Local temperature changes down to 10^-2K can be measured reliably.

A Mossbauer in situ cell for studies of catalysts and small particles is described. The cell allows studies in the temperature range 78-725K with the sample either in ultra-high vacuum or in the presence of gases. Furthermore, the cell is designed for studies in applied magnetic fields. Its application is illustrated by studies of superparamagnetic alpha -Fe particles supported on silica.

The improvements described include a quartz-crystal-controlled power supply with outputs at 16²/₃, 50 and 100 Hz, which permits motor operation at 1000, 3000, 6000 and 9000 rev min^-1, and the use of an all-dielectric system with a smooth surface for the rotor.