Table of contents

Starting from basic principles of dielectric relaxation measurements, an account is given on the present state of the frequency and time domain methods. The relative merits and limitations of the different techniques of measurement are discussed.

The design and operation are described of a novel 5 dm³ rod mill and supporting apparatus for use in the hydrothermal alteration of igneous rock samples taken from quarries in northern England and Scotland. Results obtained from more than 50 eight hour runs at 350-400 degrees C and 20-25 MPa indicated that, despite the extra constraints present in the pressurised mill compared with the conventional autoclave, the equipment was reliable in operation and afforded a reproducibility of better than +or-1% based on yields of clay products recovered.

A relatively inexpensive system is described which prints out the time of day on receipt of a logic pulse. The clock resolution is 1 s; the maximum print rate is about three lines per second.

The construction of a modular single-beam microspectrophotometer is described, with emphasis on the selection and performance of the components. The system uses phase-sensitive detection, the light intensity or its logarithm being displayed on the Y channel of a two-dimensional plotter. The X deflection is synchronised with the wavelength through a ramp voltage generated by the monochromator. Possibilities exist for extending the use of the system into the ultraviolet and for digitising data. Problems in the work with drug-nucleic-acid fibres (light scattering, cylindrical lens effect) are illustrated.

A reliable, high-intensity supersonic nozzle beam is described, the beam energy of which can be varied between 66 and 350 meV. The velocity resolution is 5-8%. Very high stagnation pressures can be used, as the entire beam enclosure including the nozzle opening is water cooled.

A three-terminal cell for the measurement of conductivity and dielectric permittivity of insulating materials (chiefly polymers) over a wide range of frequency (DC to 0.6 MHz) and temperature (140-650K) in various environments (from vacuum to some pressure of the desired gas) is described. Heat is transferred by conduction from a cooling-heating unit in contact with the high-voltage electrode. The measuring electrode is insulated by a silica glass washer of very high purity and resistivity.

A simple nearly linear brightness control for a light-emitting diode has been constructed to vary the illumination of the field stop boundary and reticle of an astronomical photometer. Noise, wear and instability problems associated with simple logarithmic carbon film potentiometer controls are largely overcome by using this novel circuit. A description of the circuit is given and is followed by a comparison of experimental results with theoretical predictions. A means of improving the linearity at higher currents is suggested for more critical applications.

The frequency behaviour of piezoelectric transducers is analysed using a phase modulation technique involving an acousto-optic modulator. The results give useful information on critical elements of laser stabilisation loops.

A description is presented of a new analogue sample-and-hold circuit. For the same hold time the memory volatility is improved by an order of magnitude compared with other sample-and-hold circuits. This circuit will provide hold times of a few minutes duration with an error of less than 1%, when the sampling or acquisition time is less than one millisecond. Another source of error due to the capacitive feedthrough of the sampling switch, common to all other sample-and-hold circuits, can be eliminated using the new circuit.

A test cell which is one end of a mercury-level tiltmeter has been constructed and tested for stability and thermal compensation. It was found that the mercury level dropped by approximately 20 mu m over a one month period as a result of reduced surface tension due to contamination. An analysis is given and it is estimated that both the gain and the thermal compensation requirements of a tiltmeter might change by as much as 5% over a period of time due to surface tension effects.

An electron beam is periodically blanked off during its travel to reduce the time-averaged beam current. The effect of this current control is demonstrated using a negative-type electron resist, where a pattern gap varies from 1.0 mu m to 1.5 mu m.

A new cathode shape has improved the stability and reproducibility of the ultraviolet continuum emitted by the plasma of a miniature argon arc. This arc is used as a transfer standard of spectral radiance in the vacuum ultraviolet.

A microprocessor-controlled photometric analyser used for the analysis of crystallographic orientations in thin sections of deformed rocks is described. The analytical technique is fast and simple, and information is obtained concerning the direction of crystal c-axis orientations in the plane of the thin section; the degree of preferred orientation is quantified.

Two-component thin films are deposited in a high-vacuum system from two close sources, heated by an electron beam which is deflected between them. By using quartz-crystal monitors the evaporation rates are measured separately, which is usually considered to be problematical. One rate signal is used to regulate the appropriate deposition rate by controlling the emission current. The other deposition rate is regulated by using the rate signal to control the dwell-time ratio of the electron beam. With this system it is possible to deposit any composition with a good homogeneity, as in the case Gd-Fe and Gd-Co films.

The conventional laser Doppler velocimeter (LDV) can only furnish the instantaneous velocity at a single point in a fluid. To obtain the complete flow pattern, the measurement has to be repeated for different regions of the flow field. In the authors' laboratory new optical systems for the simultaneous measurement of flow velocity distribution have been developed (Nakatani et al. 1979). The laser beams were arranged to intersect in a line or plane in the flow region, and optical fibres connected the interfering beams at measured points to the photodetectors. By using unsteady flow in a branch tube, it was demonstrated that the velocimeter could not only be applied to obtain the flow pattern but could also be used as a flowmeter by integrating the velocities. In these systems, however, it was required to use the same number of detectors as measured points.

A simple fringe-counting interferometer for laser wavelength measurement is described. Measured values of the wavelengths of several helium-neon, argon and krypton laser lines, stabilised by saturated absorption in iodine vapour, are presented, with uncertainties of two parts in 10⁸ (99% confidence).

Two serial interfaces suitable for translating the output of the simple, economical, very low power Ross tape recorders into digital information for processing on a minicomputer are described. Both a random logic and a microprocessor solution are presented. These interfaces together with the Ross device complete a data logging system suited to the collection of essential elements of environmental data at a large number of sites in remote locations at small cost. The flexibility in data manipulation and analysis afforded by these interfaces and the mini-computer is considerable, in addition to its obvious ability to handle large amounts of data rapidly.

Design options and constraints on a dynamically polarised target for K⁺N and K^-N experiments around 1 GeV/c are discussed and the Rutherford Laboratory solution presented. The development of a recipe for 92% deuterated target material is followed. The particularly powerful ³He evaporation refrigerator is documented in some detail. The display and calibration of proton and deuteron polarisations using automatically tuned NMR spectrometers is described with regard to the elimination of systematic errors. The performance of the target is evaluated. Up to 93% proton polarisation and 36% deuteron polarisation have been achieved in continuous operation at 430 mK and 2.5 T, with 75 mW of microwave power dissipated in 50 cm³ of target material.

A digital correlator and probability analyser suitable for applications in photon correlation spectroscopy are described. The correlator incorporates a device to minimise the effect of dust (the blinker) and enable light-scattering measurements to be made on less than scrupulously clean solutions. The electronic circuits and their operation are described. Experimental results are presented to show how the effect of dust contamination in a solution of polystyrene latex spheres can be minimised.

The rate equations are examined for the first excited singlet state population for a fluorescing sample excited by a nitrogen laser pumped dye laser. A solution is found which enables the fluorescence lifetime to be calculated from the delay between the peak of the fluorescence pulse and that of the excitation pulse. A data acquisition sampling system is described which measures this delay and uses it to calculate fluorescence lifetime. The system is tested on a number of laser dyes. The wider applicability in electronics is pointed out. The importance of the technique is that only the signal peaks need be identified and with the use of filters this can be done with accuracy.

The authors describe modifications to the method of reference beam phase modulation as applied to time-averaged electronic speckle pattern interferometry. The modifications enable measurements of vibration amplitudes at frequencies in the megahertz region to be made semi-automatically across the whole surface of an object.

In order to explain the large energy broadening of the lines observed in energy spectra of electrons emitted by fast particles, an accurate knowledge of the angular acceptance function of the electron energy analyser is necessary. A simple method is proposed which can give an accurate function for most atomic collisions; the various approximations are discussed. It is also shown that the analyser transmission depends on the acceptance angle.

The authors describe a monochromator capable of high resolution (resolving power above 50000) in the near vacuum ultraviolet spectral region. The instrument is equipped with a vibrating mirror before the exit slit, in order to scan the spectral line under study several times during one Tokamak discharge. Examples of ion temperature measurements in the plasma periphery by using impurity lines are given.

A simple apparatus to measure the number of pulses present in 65 successive time intervals (channels) following a trigger event and to average over up to 32000 trigger repetitions is described. The minimum channel length is 1 mu s and the maximum counting rate is 25 MHz. The apparatus specifically built for a time-of-flight molecular beam apparatus can be fruitfully used in other applications, for instance photon counting.

The design of an easily alignable Stern-Gerlach polarimeter magnet with dihedral pole pieces, suitable for measuring the polarisation of cold neutron beams, is described. Examples are given of its use in measuring directly the polarisation of beams obtained using polarising curved Solders. It was shown that, for high intensity monochromatic beams, it is possible to use the polarimeter to measure polarisations to 0.1% accuracy in data-collecting periods of about 1 hour.

In applications requiring long-term in situ measurements, or in the operation of remote sensors as in meteorology and oceanography, power-conserving circuits are especially advantageous. The closed-loop circuit described adjusts the coil power of an electromagnetic flowmeter when flow velocities exceed a preset threshold value. As a consequence, electrical power is saved.

An electronically controlled, laboratory-scale, transfer printing press is described. The press has been designed so that a desired temperature gradient can be established across the heated plate. This feature enables the rapid evaluation of the optimum temperature conditions for both dye transfer to and fixation on a textile fabric.

While the literature contains many contactless resistivity measurement methods suitable for fairly large spherical, cylindrical and rectangular geometries, few of these are designed for small samples. After a literature review, a variable-temperature technique which is well adapted to small circular wafers is presented.

The problems of long experimental duration have been solved by the realisation of a semi-automatic apparatus. A microprocessor-based logic interface makes possible data transfer from a frequency response analyser to a numerical calculator tape. Experiment control, data transfer and storage, further mathematical treatments and plotting of diagrams are performed by this system. A detailed description of the interfacing circuitries is given.

A double chopper system is constructed, the gate function of which is similar to that of a slotted but infinitesimally thin disc for a wide velocity range of atomic or molecular beams. Since in this velocity range the gate function is absolutely independent of beam velocity, the time-of-flight (TOF) spectrum is much simpler than when the ordinary disc gate function is used-the function which takes account of their finite thickness. Using this double chopper, TOF measurements to determine the mean residence time of potassium ions on a platinum surface are performed.