Table of contents

Transparent architecture and controllable performance are prime considerations in the design of large instrumentation. The vast amount of aspects involved, many of which need careful consideration, necessitates a design methodology. Already system reticulation into four or five goal-oriented structures, in combination with a hierarchy in design phases, can lead to sufficient control over the design effort. The methodology is also applicable to the teaching of engineering design.

The active permanent magnet suspension (APMS) is presented and reviewed as a suitable means for laboratory and industrial realisation of non-contacting devices. Static and dynamic properties of axial and radial APMS rotary systems are discussed. A gas friction detector and a molecular beam chopper are described as typical scientific instrument applications.

A simple method for the fabrication of interdigital evaporation masks is described. The accuracy of the electrode separation is better than 5% at a separation of 0.2 mm. A minimum electrode width of 0.1 mm can be achieved with this method.

A 6 MHz bandwidth surface acoustic wave spectrum analyser has been used to process digital signals from a photomultiplier in a laser Doppler anemometer. Good signal recovery is demonstrated in the photon noise limit; speed and flexibility over a wide range of frequency can be achieved.

A modification to the Chromatix CMX-4 dye laser is described which enables the wavelength of the ultraviolet frequency-doubled output to be switched on alternate pulses between two values up to about 1 nm apart. This dual-wavelength operation is required in differential lidar detection of atmospheric pollution.

When a dye laser is tuned with a filter, the slope of the curve of gain plotted against wavelength causes the lasing wavelength to be displaced towards the centre of the gain curve. The form of the gain curve can be deduced from measured values of the displacement.

The Sydney University particle telescope has been operating for three years. In this time, a search has been made for unaccompanied relativistic particles of fractional charge and for slow, heavy, penetrating particles of any charge. The equipment and its calibration are described in detail. Fast muons and slow protons are used to assess the behaviour of the system and the associated analysis technique. Sea-level fluxes for slow protons, deuterons and tritons in the 1-2 GeV c^-1 momentum range are derived and compared with results from other experiments.

A description is given of a method for using narrow-bandpass optical interference filters to make a number of simultaneous chord observations of plasma radiation from a Tokamak. Employed with the Canberra Tokamak LT-3 the method has been applied to provide measurements of O III, O IV and O V impurity radiation from a hydrogen plasma.

A 42 MHz CW Doppler experiment for radio auroral studies is outlined. A highly accurate reference signal is achieved by employing a stable audio oscillator and a VHF phase-locked loop in the receiving system. The system output contains frequencies in the 1562+or-400 Hz range which are recorded on analogue magnetic tapedecks. Two simple units, an envelope detector and a frequency demodulator, used for continuous recording of the signal strength and mean Doppler shift variations are described.

The physical properties of colloidal dispersions often depend on the mechanical shear history. The dependency can be explained in terms of shear-induced changes in particulate structures. A full understanding of the physical behaviour requires, therefore, measuring techniques that are able to analyse the varying structure. An instrument is presented which can follow the changing dielectric spectrum at low frequencies under various shear histories. The mechanical requirements of such a device are discussed. The performance of the electronics is verified by means of computer simulation. The application of the instrument is demonstrated for a carbon black dispersion; the evolution of the dielectric spectrum, after cessation of flow, is followed.

Frequency responses of the measuring and reference cells as well as the total frequency response of a differential adsorption calorimeter have been determined experimentally. The frequency response of each cell is described by two time constants in the frequency range 10^-4-10^-1 Hz. Values of the time constants taken from a Bode diagram together with the second-order differential equation valid for the measuring cell permit the determination of the energy and power of an adsorption process as a function of time. The frequency response of the measuring cell has been found to be a very important factor in determining the ability of the calorimeter to measure the dynamics of a chemical process. The total frequency response of the calorimeter is such that the compensation of the thermostat temperature oscillations by the calorimeter depends on their frequency.

A technique for measuring the magnetocrystalline anisotropy torque of a single crystal under stress, in which the specimen is incorporated as one layer of an anisotropic laminated plate, has been assessed by measurements on a (100) nickel disc.

A versatile tethered balloon sounding system capable of measuring horizontal-vector wind, temperature, humidity and pressure altitude is described. It has a novel combination of features which include low weight, low power consumption, completely self-contained operation and good data accuracy at reasonable cost.

Characteristics of the National Semiconductor Corporation LX1600A pressure transducer are examined with the object of using the device as a short-range altimeter for probing the lowest kilometre or two of the atmosphere. In this application the device is subject to large temperature changes and stringent power restrictions. It is shown that pressure determination to +or-1.5% over ranges of 2 and 20 kPa is possible provided that temperature effects are calibrated out. Operation of the device in a pulsed mode results in a considerable saving in power consumption.

A technique is described in which large batches of fibre can be tested in a short time. Some 200 m of fibre in 50 cm gauge lengths are tested simultaneously. This offers the possibility of obtaining strength statistics on kilometre lengths without extrapolation whilst retaining the mass of data on small flaws, which testing on long-gauge lengths fails to do. The method is useful for strains of up to 3% and as such can be used for the study of static fatigue on optical fibres.

A technique is described that allows the routine preparation of preselected areas, such as leaky p-n junctions on silicon wafers, for transmission electron microscopy. The method yields thick, mechanically stable specimens with an electron-transparent centre, the thinnest part being at the preselected position. The crystal is first thinned by local ultrasonic dimpling from the reverse side, and then is chemically etched to the required final thickness. The technique may possibly be used for other non-ductile materials such as germanium, gallium arsenide, glasses, garnet crystals, ceramics. etc.

The design, construction and operation of a compact, high-efficiency Bragg diffraction spectrometer are described. An accurate method of alignment is presented. The spectrometer has been tested with a lead stearate analysing crystal by measuring carbon K (methane) and argon L X-ray energies produced by direct electron beam excitation. The high efficiency of this apparatus is demonstrated by measuring satellite lines of the neon K spectrum with a RbAP analysing crystal.

A spark erosion technique for the preparation of finely divided metallic and intermetallic powders is described. An X-ray diffraction line-broadening analysis was used to compare the average particle size obtained for a spark-produced nickel powder with that of a commercially prepared catalyst, Raney nickel. The average particle size of the Raney nickel powder was found to be approximately 6 nm smaller than that obtained from nickel powder sparked at an electrode potential of 700 V and a discharge energy of 3.92 J. Although certain intermetallic compounds could be prepared as powder blacks using the spark erosion method, traces of one of the individual elemental components were usually found in the powder. It appears that, in general, many materials may be produced as powders by a spark erosion technique provided they are electrically conductive.

The two-parameter frequency optimisation theory which was originally developed for the constant-temperature hot-wire anemometer is extended to hot-film anemometers. It is found that the constant-temperature hot-film anemometer behaves as a control system of order ⁵/₂ which allows for a two-parameter optimisation of its dynamic response. The cut-off frequency of the hot-film anemometer can be estimated by means of a sine-wave test. A combination of sine-wave and square-wave testing seems to be the best strategy for optimising the system.

A number of new filter glasses for photometric use have recently been developed at the NPRL. The visual spectral transmittance curves have bandpass characteristics closely resembling the standard photometric functions x( lambda ), V'( lambda ) and V( lambda ) (Res and Kok 1974, Res et al. 1975, 1977). Further work was carried out to develop glasses simulating the CIE spectral tristimulus value z( lambda ). Silicate glass doped with CuO together with different amounts of CeO₂, TiO₂ and CoO proved to be most promising. The work resulted in a glass whose spectral transmittance, in conjunction with a 2 mm thick Schott GG 420 filter, yielded quite close simulations of the z( lambda ) function.