Table of contents

The nature and properties of analytical utility of high-frequency inductively-coupled plasma sources employed for optical emission spectroscopy are reviewed. Instrumentation and applications are described and particular attention is given to the development of methods of sample introduction into these sources.

Describes the design of a continuous-flow helium cryostat for the study of the dynamical behaviour of bound and free ionic charge carriers in the temperature range from 3.5 to 450K. Samples up to 10*10*5 mm can be investigated. The background current amounts 5*10^-17 A or lower. For illustration the thermally stimulated depolarisation current (TSDC) spectrum of a La_1-xBa_xF_3-x (x=0.0126) single crystal obtained with this cryostat is presented.

A rotating dynamic capacitor is described for measurement of contact potential differences, in which the sliding contact is avoided by using an additional fixed capacitor which provides a capacitive link with the electronic circuit. The dynamic capacitor is included in a measuring device containing a phase-sensitive detector (PSD) synchronised with the modulation frequency of the capacity which makes it possible to change the modulation frequency within a wide range. The measuring device supplied with a PSD ensures stability, high input resistance (over 10¹² Omega ) and enhanced accuracy of measurement (from 10 mV to 4 V with 0.2% accuracy for all ranges).

A novel application of a well known principle is used to attach vibration-dampening plates to a Plexiglass wind tunnel without drilling holes in the walls or using bonding agents. The resulting assembly, which was simple to install and easily removed, could be equally applicable to other large panels requiring stiffening to reduce or minimise vibration.

The position of the measuring volume, formed by laser beam intersection in laser Doppler anemometry (LDA), needs to be known accurately. The use of a thermistor probe for determining measuring volume location is described. This is accomplished by allowing the beams to impinge on a thermistor and measuring its resistance, which changes as the thermistor is heated by the beams. Resistance values indicate whether one, two, or three beams of a three-beam LDA system are striking the thermistor. The probe system design is described, and experimental results are presented.

A dispersive optical system consisting of a grating and a prismatic beam expander is described and analysed. The function of the prism beam expander is to enhance significantly the dispersion of the grating. The application of the principle to a simple wavelength meter, suitable for pulsed and CW lasers, capable of resolving 0.01 nm at 568.8 nm is outlined.

A low-cost variable beam splitter is described. It is based on frustrated total internal reflection and is practically free from losses. During its regulation, no deflection is introduced of the output beams, whose intensity distribution remains unaffected.

A light beat method for generating frequency markers on the diffraction efficiency versus frequency curve of acousto-optic (AO) cells is described. The output signal of a photodetector detecting all of the Bragg-diffracted laser beams produced by an AO cell driven by the sum of a chirp signal and a multifrequency signal has been calculated and experimentally confirmed. This method can be applied in the testing and aligning procedure of AO cells and in the field of AO spectrum analysis of signals.

A simple and efficient algorithm of digital phase detection is presented. From data sampled at two instants of time separated by a quarter of the signal period an estimate of phase and magnitude can be obtained. The additional use of coherent averaging improves the accuracy of phase detection in signals with poor signal-to-noise ratio. A system implementation of the algorithm and error caused by the harmonics of the measured signal is discussed.

A simple hand-held refractometer is described, which has a linear scale of refractive index. It is intended mainly for applications where simplicity and ease of use are the main requirements, and where the required accuracy does not warrant temperature correction. It provides a quick check of concentration to within 1% for most aqueous solutions and emulsions. Two versions of the refractometer are described, a reflection version using internal illumination, and a transmission version using external or ambient light. The former is potentially the more accurate, as it is free from geometrical aberrations, but the contrast tends to be low if there is any scattering material in the liquid; the latter gives a very high contrast, even in milky liquids.

An inexpensive Teflon dilatometry cell, using an integral movable diaphragm allows high-sensitivity scanning differential dilatometry to be carried out on liquids using any conventional displacement sensor, such as a capacitance dilatometer, strain gauge or LVDT. It is most suitable for the study of phase transitions in liquids, or solids immersed or suspended in liquids. The authors have studied the phase transitions of unsonicated dispersion of dipalmitoyl-phosphatidylcholine and water using a capacitance dilatometer.

Simple infrared field thermometers appear to suffer from small internal heat flows which influence the sensor when the instrument is used outdoors. Further research into higher sensitivity of the sensor must be accompanied by increased attention to heat insulation of the instrument and sensor.

A piezoelectric pressure bar gauge is described in which the piezoelement is fixed (without soldering or cementation) by sandwiching it between two pieces of the pressure bar. The gauge has a high time resolution and significant advantages. Conventional low-cost components are used for all parts of the gauge. The results of plasma pressure measurement by the gauge described are presented.

Preparation techniques for specimens for the study of interfaces with atom-probe field-ion microscopy have been developed. Grain boundaries in stainless steels were brought within the depth of analysis using pulsed electropolishing. Cemented carbide specimens with carbide-carbide interfaces for analysis were prepared using ion etching.

A D'Arsonval mechanism is terminated with a negative-input-resistance amplifier which nearly cancels the effect of the resistance of its windings and extends its low-frequency response as an inertial angular sensor. The behaviour is essentially identical to that of a force-balanced angular accelerometer in series with a high-pass filter with a break frequency typically below 0.1 Hz.

An inductive non-contact method of velocity measurement of discontinuous dust fluxes is developed. The method was verified in laboratory experiments and it was found that the measuring procedure is both quick and sensitive, the flow of particulates is not disturbed by the measuring ring probes applied, the measuring system is reliable and simple and the measurements performed are also simple. The total costs of this method are not too high. After suitable modifications, this method may be applied to continuous flows of both solids and fluids in various pneumatic systems. The results of measurements and calibration of the method are discussed and applications to velocity measurements in continuous flows are proposed.

A new version of the charge-density method, applicable to the analysis of the potential distribution in multi-element electrostatic lenses used for focusing beams of charged particles, is presented. A study of the optical properties of a four-cylinder lens has been carried out. Data are given for this lens over a wide range of the voltages applied to the electrodes.

For pt.I see ibid., vol.16, no.7, p.625-30 (1983). A four-cylinder electrostatic lens can be used to keep both the position and magnification of the image of a fixed object constant while the energy of the image is varied. The required relationships that must be maintained between the variable voltage ratios of the lens have been determined using a new version of the charge-density method, and the spherical aberration of the resulting zoom-lens has been evaluated.

A novel electrostatic lens system consisting of several short, closely-spaced elements is described. By applying the appropriate voltages to these elements it is possible to simulate a lens having longer elements and a variable position. If such a lens has n independent voltages it can be used to maintain (n-1) properties of an image, or of more than one image, constant while other properties are varied, within the constraints imposed by the Helmholtz-Lagrange relationship. The properties are the position, energy, linear magnification and angular magnification. A movable three-cylinder lens is considered as an example and the necessary data are presented to enable three different pairs of image properties to be kept constant. It is shown that the lens can be operated over wide ranges of the variable image properties.

A coherent pulse and double resonance NQR spectrometer system, for investigations in the pure quadrupole regime, has been described. The pulsed NQR spectrometer is capable of operation typically over the range of 10-40 MHz and can be adapted with ease for spin echo investigations, relaxation time measurements and double resonance experiments such as spin echo double resonance (SEDOR) and double resonance in the rotating frame (DRRF). Besides the Hartmann and Hahn DRRF scheme, a DRRF scheme involving off-resonance irradiation of the abundant spins can also be implemented. To simplify construction, commercially available devices have been extensively incorporated into the spectrometer system. The general features of the spectrometer are presented and the performance is illustrated by a few typical signal recordings.

A description is given of a Q-meter that is equipped with a wide-band (10-160 MHz) cryogenic preamplifier and is especially suited for NMR experiments at very low temperatures, where it is attractive to sweep and modulate the frequency rather than the field. The spectrometer can detect absorption and dispersion signals simultaneously.

A new opto-electronic ellipsometer operating on laser interferometric principles has been developed into an automated system based on a microprocessor. The latter performs the gain and offset calibrations and adjusts the various mode settings, followed by fast on-line data acquisition. Subsequently, data are processed via an interfaced minicomputer. The instrument is unique in providing absolute ellipsometric data. It permits perpendicular incidence ellipsometry, the handling of both vertically and horizontally mounted (liquid) samples, as well as precision reflectometry. Alignment is easily and quickly achieved because the signals are displayed on a cathode ray oscilloscope (CRO) screen. Some of the valuable features of this system are discussed in the light of results obtained in the visible spectrum.

The neutron optics of a three-axis spectrometer with curved ideal monochromator and analyser crystals is considered. The computation technique allows for both real- and reciprocal-space focusing effects. The possibility is revealed of obtaining very high resolutions based on the correlation between the monochromator and analyser units introduced by a thin sample with a suitable orientation. The high resolution conditions can be satisfied by varying the curvature of the monochromator and analyser crystals and the sample orientation. Simple analytical relations are given for connecting the desired high-resolution direction in the Q, omega space with the necessary spectrometer geometry.

The authors have designed and built a gated 64-channel random pulse input register and controller unit. In conjunction with segments of a commonly used LeCroy qVt multichannel analyser, it comprises a stand-alone counter system which is useful in experiments with a large number of detectors. In particular, when hardware and software components are still in the debugging phase, this device can largely reduce the labour of data taking for diagnosis. Input and output levels of the device are TTL for general compatibility. In its present configuration, the system can be used wherever samples of random pulses with rates up to 2 kHz per channel must be taken on up to 64 channels simultaneously, for example in cosmic ray tests. After making minimal modifications to the unit, rates to about 10 kHz can be accepted.

An analysis of the thermal response of an electrical resistance thermometer or bolometer is presented which takes into account the thermal feedback produced by Joule self-heating. It is shown that this can lead to significant changes in the gain and bandwidth, particularly in the case of high-sensitivity superconducting transition edge bolometers, and that such changes can be controlled and utilized by appropriate choice of electrical bias network.

A detailed analysis is made of a linear system model of self-balancing bridge systems which maintain some detector element at a constant temperature by Joule heating in its own resistance. Such systems are widely used in anemometry and have applications in other areas such as bolometric radiation detection. Concise expressions for the system transfer functions for both thermal and electrical signals are obtained and a detailed discussion of the dependence of the bandwidth on system parameters and operating point conditions is given. A characteristic frequency relating to thermal feedback by Joule self-heating in the detector is recognized which has fundamental significance in describing the potential for bandwidth enhancement by negative feedback in these systems.

A new development in temperature control is presented. This consists in using a Wheatstone bridge in a proportional thermostat both as a monitoring and a heating unit. The sensor is a copper wire closely and evenly wound around the volume to be temperature controlled. The other bridge resistors are manganin wires and are wound around the same volume. The theoretical limit of control is 0.5 mu K or 1 part in 10⁹ of the sensor resistance. In practice the stability of the resistors and the design of the thermal system limited somewhat the temperature stability. Tests at 25 and 37 degrees C operating temperatures showed a 15 mu K/day long term drift, including the drift of the relatively modest system used to measure the temperature.

A simple continuous-flow cryostat suitable for use with optical microscopes is described. Its working range is from 10K to 350K with stability +or-0.1K. The specimen is mounted within an exchange-gas filled cell to ensure thermal equilibrium. Access to the specimen is via small easily demountable vacuum-tight low-temperature windows made using PTFE gasket seals.

A novel pressure-scanning calorimeter (PSC) is described for the pressure range 0.1-35 MPa and temperatures up to 473K. The calorimeter measures directly the thermal power and/or the energy as a continuous function of pressure. Thermal parameters are measured in a differential calorimeter by a power compensation method. The pressure variation is imposed as a linear function of time by a programming system with a feedback loop. The crystallisation and fusion of di-phenyl-ether induced by a linear pressure change are described as an example of application.

The authors report measurements of the thermal conductivity, specific heat, and critical temperature of the aluminium alloy 5056 in the range 0.05 to 1.3K. The absence of magnetic anomalies in the specific heat and the rather high thermal conductivity in the superconducting state would allow reasonably fast cool-down below 0.1K of multiton gravitational wave antennae made of this material. On the basis of the measured properties, the desired refrigerator characteristics are discussed.

An automatic electronic system for measuring the electrical resistivities of a large number of concrete sample cubes over a period of up to 100 days is described. Results obtained using the equipment are presented and the possible applications to concrete quality control and fundamental research are briefly discussed.

A relatively inexpensive binary correlator is described which can perform both cross correlation and autocorrelation. It has been used to determine the distribution of speeds of sand grains in a sand-blast erosion test. Motion of the grains is detected by an optical sensor, with no moving parts, which does not interfere with the grains. Speeds up to 500 m s^-1 can be measured with a theoretical error less than +or-1%, practical values obtained have errors in the range +or-5%-+or-10%; particle sizing can also be performed. Good agreement on particle speeds of up to 25 m s^-1 has been found with high-speed photography. The correlator uses a popular inexpensive microcomputer, and time to perform correlation is minimised using an efficient algorithm. Equipment is not restricted to this application and thus forms part of a flexible laboratory system.

A novel form of liquid level gauge is described, based on a coaxial transmission line mounted vertically and partly filled by the liquid. A tunnel diode mounted at the top of the line sustains a square-wave oscillation, the period of which is a linear function of the distance between the diode and the surface of the liquid. Factors influencing the accuracy are discussed and results are presented for experiments using water and kerosene as working fluids. It is concluded that in comparison with conventional capacitance and transmission line gauges the method is capable of greater measurement accuracy for a given precision in manufacturing the electrode assembly, especially when a long working range is required.

A new directional coupling system for a waveguide has been developed. The system is the combination of two loop elements on the narrow side of a waveguide and a coaxial 3 dB, 90 degrees hybrid coupler and can easily be installed on the waveguide-array mouth for launching a lower hybrid wave into plasma. An experimental test of the system was carried out near a frequency of 1250 MHz and the directivity was found to be about 20 dB.