Table of contents

This paper reviews the development of underwater television, its application in the offshore industry, and its use on ROV systems. Further developments are also discussed together with requirements to increase TV system capability particularly by increasing system resolution and extending viewing range of both monochromatic and colour systems.

A second-order filter is described. A simple procedure is outlined for optimally satisfying a specified response.

Generalised coefficients for Abel inversion following Bockasten's method are presented. The coefficients are useful when spatial resolution is important and it is necessary that the number of chords used in the Abel inversion be varied with a minimum of computation.

The construction of a Gunn oscillator stabilised by means of a cylindrical TE₀₁₁ cavity is described. The resulting oscillator has a mechanical tuning range of about 1 GHz around a centre frequency of 9.5 GHZ. A varicap diode inserted on the wall of the stabilising cavity provides a tuning range of 20 MHz. The results obtained by the use of this oscillator as RF source in a reflection cavity homodyne spectrometer are discussed. It is shown that this kind of oscillator can substitute for low noise klystrons without significant noise degradation in ESR spectrometers.

Describes an instrument for accurate measurement of transient changes without the machine having to be synchronised. The instrument has been designed for laboratory use but the principle could be applied to practical machines.

Continuous measurements of fluorescence polarisation are made using a chopped light source and detected via a continuously rotating polariser. Lock-in amplification techniques are used to recover the information from the photomultiplier output, thus ensuring good stability and high signal-to-noise ratio.

A simple and accurate device for alignment of a linear-cavity solid state laser system is described. Alignment is obtained between the light source of the device and the surface of an optical element in the system by overlapping the outgoing laser beam and the reflection of that beam from the surface. This is then repeated for any number of surfaces in the entire optical system. A very accurate adjustment, leading to alignment of all the elements in the optical system is thereby achieved.

The design and constructional details of the cell are given together with a brief description of the analysis of the data. The results of measurements made on water at 20 degrees C are presented.

A simple refractive index cell for use in the spectral range between 0.2-20 mm^-1 is described. The module is designed to be compatible with a Beckman-FS720 interferometer and it is extremely easy to align and use. The cell has the advantage of high energy throughput and low reflection losses from the thin polymer front window. The results obtained for liquid tetrabromoethane and p-difluorobenzene agree within 1-2% of the published data, the random error in our measurements being about +or-1%.

Measurement of field-gradient induced birefringence in certain fluids permits the direct determination of molecular quadrupole moments. Two electrode assemblies (a monopole cell and a two-wire cell) having different potential distributions were constructed to provide non-uniform electric fields of known magnitude. The cells were designed for measurements on liquids and the alternative electrode configurations gave agreement in values for the field-gradient birefringence constants of benzene and carbon disulphide.

A microprocessor control system for use with a high-temperature X-ray Weissenberg continuous-recording camera is described. The unit incorporates facilities for the control (at best +or-1/40 degrees C) and programming of temperature and for the operation of an X-ray beam shutter and film-increment motor. Complex experiments, which may involve temperature cycles, ramps, plateaux, etc., are concisely specified by combinations of six different programme modes and are carried out automatically, without operator intervention. The system is principally used in lattice-parameter and other related studies of single crystals undergoing solid-state phase transitions.

Electron back-scattering patterns (EBSPS) have been obtained in a field emission gun scanning electron microscope, and the crystallographic information they contain has been shown to come from a small volume <or approximately=20*80*10 nm. A small angle back-scattered electron detector has been used to take pictures with enhanced crystallographic contrast, and is capable of clearly delineating sub-grain boundaries in a Ni (100) crystal with misorientations of order 0.5 degrees . The EBSP technique has been applied to determine epitaxial orientation relationships between sub- mu m crystals grown in situ on a single crystal substrate (Ag/W (110)) with an accuracy of +or-0.3 degrees .

The aberration constants of a deflected electron beam passing through electrostatic crossed deflection fields due to four circular electrodes arranged round the optical axis are evaluated. The results show that the aberration of a distorted beam spot deflected by the crossed deflection fields is dominated by the second- and third-order astigmatisms, and aberration constants of their astigmatisms are much greater than those for a sequential deflection system with parallel plates. Various caustic patterns of the corrected deflection beam are graphically displayed by computer calculations.

When a metallic or conductive sample is held at a potential V in an electron beam lithography machine, an electric field is created between the sample and the nearest machine parts such as the holder for backscattered electron detectors. Consequently, registration accuracy deteriorates. Deflection errors divided by deflection lengths (relative deflection errors) are found to be proportional to the sample voltage. They agree quite well with the predicted values, where relative deflection error is shown to be inversely proportional to the electron beam acceleration voltage.

A slanting hot wire placed at different angular positions is used to determine the complete Reynolds stress tensor in a three-dimensional turbulent boundary layer. The hot wire is extensively calibrated in a static way and a five parameter calibration formula is proposed to describe the directional sensitivity of the wire. Results of measured Reynolds stresses in a three-dimensional turbulent boundary layer of a curved duct experiment are presented. The present method is also used to determine the mean three-dimensional flow field.

A description is given of an apparatus which enables the measurement of damping during vibration with non-zero mean strain. The loading condition is torsion on a pair of cylindrical specimens, which may be solid or hollow. Mean strain is applied by opposite pre-twist in the two specimens. Damping is determined from energy input during steady resonant vibration, although both frequency response and free decay techniques can also be used. Operating frequency is in the range 20-100 Hz and vibratory surface shear strain amplitude up to +or-0.003 can be applied, with mean surface shear strain up to large values (in principle, unlimited). An account is given of the apparatus development and operation, with particular reference to the use of a test specimen/low damping specimen combination which effectively halves the required power input and which allows a correction for extraneous losses to be applied.

As part of a long term investigation being planned on the study of flow resistance characteristics of rotating elements, this paper describes the design and construction of a pressure transmission system suitable for making pressure measurements in a rotating duct, together with a selection of preliminary commissioning results. For flow in a tube which rotates about a parallel axis, the results obtained suggest that transition to turbulence is suppressed due to the rotation and that flow resistance may be significantly reduced as a consequence.

A novel design of probe to measure vapour superheat in a vapour-liquid droplet flow is described. The probe is an exposed junction thermocouple with a fine wire tip which is heated intermittently to remove liquid drops. The tip is heated electrically by including the thermocouple junction in a capacitor discharge circuit. The probe is shown to measure steam superheats successfully in the type of non-equilibrium steam-water droplet flows likely to be generated during water reactor reflood by emergency cooling water. Design improvements to extend the range of application of the probe are outlined.

The authors describe a fully automated process control, data recording and analysing system for measuring heat capacities in the temperature range 0.3K to 320K, using the Nernst method. The DC measuring system employs the CAMAC-norm in conjunction with an on-line-computer system (PDP 11/15-PDP 11/20), shared together with three other types of solid state physics experiments. The apparatus is characterised by a high flexibility to adapt to a wide range of different experimental conditions and has been tested in a series of high precision specific heat measurements. The low temperature calorimeter and the organisation of hardware and software components are described. The performance of the apparatus is illustrated by results obtained on a copper-standard sample.

For pt.I, see ibid., vol.13, no.12 (1980). A two-dimensional imaging photon detector has been developed using a proximity-focused transparent photocathode (S25), three microchannel plates in a 'Z' configuration and a proximity-focused 'linear' resistive anode. The device shows a detected quantum efficiency of about 15% at 500 nm, 5% at 630 nm and 1% at 800 nm and a stable performance in extended operation which should correspond to many years of continuous use in practical applications in astronomy and geophysics. With the 18 mm photocathode and microchannel plates presently used, about 4*4⁴ pixels can be obtained, corresponding to a FWHM resolution of 100 mu m at an electron gain of 10⁷.

A form of capillary viscometer is described which can be mounted inside a flask and used to monitor the progress of laboratory-scale condensation reactions (e.g. during development work in urea formaldehyde resin chemistry). The unit described operates in the range 1-10 mm²/s (i.e. 1-10 centistokes), and enables kinematic viscosity to be measured at intervals of about 1 min. A quick-filling device and automatic flow time display are incorporated in the design.

The response of a frequency optimised constant-temperature hot-film anemometer to an electronic step function is calculated using Laplace transform methods. It can serve as a standard of comparison during frequency optimisation of the anemometer by means of the convenient square wave test method.

A versatile method for analysing experimental curves with exponential character is presented. By introducing an exponential x deflection instead of the normally used linear time-base of an oscilloscope the determination of time constants of exponential curves is transferred via manual tuning to the externally generated x deflection. On account of this the time constants can be derived from a signal essentially free of noise and ambiguity and may easily be obtained in digital form. Based on this idea a device has been developed which is described in some detail. As an example of the method's application, trap studies in heated silicon are reported.

The effect of the change of scattering geometry with scattering angle in beam-beam experiments is investigated. Atomic (molecular) target distributions associated with static gas, orifice, tube, capillary array (with and without further collimation) and jet sources have been considered in model calculations for a number of commonly used electron scattering geometries. The relationship among scattering intensity, cross section and the geometrical integral called 'effective path length' is derived. Volume correction factors (the reciprocal of effective path length) have been calculated for sample cases to illustrate the effect of various beam and scattering geometry characteristics. The validity of the model calculation has been experimentally verified.