Table of contents

The review covers the elementary aspects of construction and use of instruments for electrode process research, dealing with both electrochemical and biological applications where these methodologies overlap. There is a guide to desirable specifications in commercial instrumentation and a list of manufacturers of equipment.

Random access memories are used to store data from a temperature-depth (TD) probe in a system for short submarine TD profiling. The cost of the equipment not including the platinum resistance and the strain-gauge pressure transducer, is approximately Pounds 200.

The corrections necessary in fluorescence polarisation measurements, when light emitted into a finite solid angle is detected, are derived and explicitly calculated for idealised experimental conditions.

In high-resolution spectroscopy, the Doppler broadening is suppressed through the use of two counter-propagating beams so that one of the beams is obviously reflected back into the laser cavity. Conventional optical isolators are efficient enough to reduce the coupling but some intensity fluctuations always remain due to residual feedback. A simple technique is described which does not suppress the residual optic feedback but completely cancels its effect on line shapes and signals.

Measurement of the instantaneous temperature in heated turbulent air flows has often been carried out with cold-wires operating at a constant current supplied by an electronic circuit. A new electronic circuit for such a resistance thermometer offering simplicity with good accuracy, has been developed. The advantages over previous configurations are low voltage drift and simple construction and operation. The circuit is described in detail and measurements in a heated homogeneous shear flow are provided as an application.

A pulse generator designed for making detailed studies of fast echo signals is described. This TTL generator is coupled to a fast signal averager consisting of an analogue memory used as a buffer memory, and a normal-speed multichannel analyser. The electronic circuits used are discussed in detail and as a test the spin-echo signal from ⁵⁷Fe nuclei was recorded.

The design of a thermostat which gives a temperature stability of +or-3.5 mu K over long periods of time is described. Heat input to the thermostat is derived by stirring only. The temperature balance is maintained by changes in the speed of stirring in accordance with the state of a thermistor-based AC Wheatstone bridge. Since the heat input source is so directly coupled to the thermostat water, the thermostat responds very rapidly. Therefore, the thermostat can adjust itself easily to the surrounding temperature without noticeable fluctuations. This method obviates hot spots inside the thermostat and therefore decreases the temperature gradients. It also eliminates the electric and magnetic fields usually created by heating elements. The thermostat has a stabilisation factor of the order of 10⁶ with respect to room-temperature fluctuations.

Measurements of the flow direction error of some accepted designs of combination pressure-sensing probes in a shear flow have been made. For a spherical probe an inviscid shear flow theory predicts the flow direction error with good accuracy for normal hole spacing, namely 65-85 degrees , but becomes less accurate at much larger hole spacing (about 110 degrees ). The problem of determining the direction of the free shear jet used for testing was solved by measuring the apparent flow direction with several sizes of geometrically similar probes and extrapolating to zero size for the true direction. An important observation of error in the use of a parallel hot-wire probe in a shear flow has been made.

The method proposed by Delage and Carette (1971) for the study of electrostatic spectrometers, the calculation of energy distributions, is used for the optimisation of the 180 degrees hemispherical electrostatic deflector. Energy distributions were computed for a large range of possible dimensions; by means of least-squares fits, parameterised relations giving energy resolution values Delta E₁2//E₀ and Delta E_B/E₀ are proposed. Using as a criterion the optimisation of both the profile and intensity of the energy distributions, that the relation alpha ²=0.56 Delta S/R₀ between the semi-aperture angle and the aperture width determines the optimum conditions. This relationship represents the ideal compromise between the respective contribution of these factors to the energy resolution. Its validity for circular apertures is confirmed by further calculations which take into account the effect of the third dimension on the electron trajectories.

To monitor geomagnetic pulsations at the southern auroral zone station, Macquarie Island, a sensor consisting of a solenoid wound on a ferrite core was used. The design of the sensor and a suitable preamplifier and their field operation and calibration are described.

A digital system for a programmable frequency synthesiser is described. It performs a staircase frequency sweep with a step of 1 Hz and digitally programmed bidirectional square-wave frequency modulation in an NQR spectrometer with a frequency-locked super-regenerative oscillator. The system is particularly convenient when using digital averaging techniques. NQR spectra parameters are not influenced by frequency modulation even when extremely large frequency modulation deviations are used. Parameters such as the sweep rate and the amplitude of frequency modulation deviation are stable, accurately fixed and independent of the running frequency. NQR spectra of ³⁵Cl in p-dichlorobenzene and ⁶⁵Cu in Cu₂O were plotted against frequency by an X-Y recorder.

The paper describes the construction and performance of an atom-probe field-ion microscope which uses a time-gated microchannel plate as a single-ion detector with spatial resolution. The instrument has a mass resolution Delta m/m in the range 1/15 to 1/25, and a spatial resolution of the order of 1 nm. It is particularly suitable for the detection of segregation at grain boundaries, and an example (oxygen in molybdenum) is given.

An instrument for maintaining a torsional pendulum at constant amplitude is described. Automatic plotting of internal friction against temperature over a frequency range of more than three decades is obtainable. The instrument is simply constructed from commercially available components and can be adapted easily to suit most torsion pendulums in use. A modification that permits the frequency of oscillation to be varied by more than an order of magnitude without otherwise disturbing the apparatus is also presented. Measurement technique is discussed and two major sources of error are evaluated. A Zener peak measured with this apparatus is compared with that obtained by the classical 'decaying amplitude' method.

An experimental device for studying heavy particle collisions in the energy ranges 5-40 keV is described. Differential inelastic cross sections are measured by means of an energy loss analysis at scattering angles ranging from 0.5 to 4 degrees . Typical energy loss spectra obtained at 6.5 keV and 40 keV are given for two diffusion angles.

The concept of an apparatus function which is only a function of the centre-of-mass scattering angle theta and relative velocity g is used to analyse elastic laboratory differential cross section data in terms of an intermolecular potential. The apparatus function is calculated by Monte Carlo simulation techniques. Examples are given for calculated laboratory angular distributions under various experimental resolutions. The method is applied to differential cross section measurements of Ar-Ar, Ar-Kr, Ne-Ar and Ne-Kr. Good fits are obtained for the existing Ar₂ potentials, while potentials published for the other systems are to be altered slightly to produce the best fits.

Compton scattering spectra from various metallic and ionic crystals have been measured at three energies in the range 40-80 keV using monochromated radiation from the 5 GeV electron synchrotron NINA. Good statistical accuracy was obtained with thin samples in short measurement periods. This indicates that Compton profile studies of the electron momentum density with synchrotron radiation are not only practicable but also currently offer the best method of minimising parasitic multiple scattering effects.

Five replicate measurements of the low-field anisotropy of magnetic susceptibility (AMS) of 10 basaltic samples were made using a torque magnetometer and a Digico spinner magnetometer to compare the azimuthal precision for these instruments. AMS measurements of 100 additional basaltic samples are used to compare magnitude determinations between the two devices. It is shown that although analyses using the torque magnetometer are more time consuming that similar measurements using the Digico spinner magnetometer (1.5 h as opposed to less than 4 min), the precision of the torque magnetometer is superior. The instruments gave similar results for measurements on two samples constructed from homogeneous dispersions of equidimensional magnetite grains.

Describes an electronic device which, by means of the piston and anvil technique, facilitates the quench from the liquid state for alloys whose liquid-solid region is large at high temperature. The block diagram of the device is given and the performance of the casting apparatus is evaluated.

Using numerical solutions of the Bloch (1946) equations under boundary conditions representing the local external magnetic field, and with the aid of a simple model of the nuclear spin process, various effects occurring during selective excitation are described. In particular it is shown that in extending the technique for one to two dimensions there arises the possibility of spurious image response, and that this can be corrected by a suitable combination of signals from a set of three excitation sequences. Since two-dimensional selection activates a column of nuclei, the subsequent application of a lengthwise magnetic field gradient followed by Fourier transformation of the resulting spin signal will directly yield an image line. This provides a technique for full three-dimensional imaging which satisfies moderate data-processing requirements and yet retains (line by line) the advantage of Fourier methods.

The thickness of the barrier metal on a Schottky solar cell is very critical to the conversion efficiency. Precise control of the optimum thickness can be achieved by monitoring the first derivative of the photocurrent during deposition. A true DC differentiator with fast response time for a very slowly varying field can be made by using sample-and-hold circuits.

The characteristics of Borda inlets when used as flowmeters are investigated, and the parameters which have to be taken into account when predicting the calibration coefficient (commonly referred to as the 'discharge' coefficient) of any particular device are determined. Standardised positions for locating the pressure tappings are proposed, and the variation of discharge coefficient with Borda diameter and relative thickness of the inlet edge is established. The modified method of using a Borda inlet which is presented avoids the need to use any corrections for compressibility effects, but the relationships found between discharge coefficient and the various parameters have been obtained for tests in air only, and so should not be used for any compressible fluid with an appreciably different specific heat ratio.

The use of a hot-wire anemometer in bubbly, two-phase flow has been studied with important results by several authors, among them Bremhorst and Gilmore (1976). In connection with the authors' attempts to use hot-film probes for measurements of the liquid velocity, the turbulence intensity of the liquid and the bubble velocity in three-dimensional, turbulent, bubbly, two-phase flows (Remke 1976), it was important to investigate the response of probes with inclined sensor elements, especially of 45 degrees probes of the wire type, to passage through an air-water interface. The results of observations have been made during static and dynamic interfacial piercing tests with the above-mentioned probes. They are suited to complete the explanation of the interaction between probe and interface given by Bremhorst and Gilmore. The main differences between the tests reported below and the experiments carried out by Bremhorst and Gilmore are (i) the application of commonly used probes with inclined sensors instead of a specially designed probe, and (ii) in the kind of traversing of the probes through the interface.