Table of contents

Absolute single-particle detection efficiencies and pulse height distributions of a cascaded microchannel plate (MCP) detector are reported for the ions , , , and in the impact energy range 0 - 4.75 keV. The detection efficiencies have been obtained using the photoelectron - photoion coincidence (PEPICO) technique which allows the determination of detection efficiencies without knowledge of the absolute ionization rate. The mean gain is found to increase with increasing ion impact energy and decreasing ion mass. Depending on the ion mass, the absolute detection efficiencies saturate above 2.5 keV and reach about 63%.

In-fibre Bragg grating (FBG) sensors are one of the most exciting developments in the field of optical fibre sensors in recent years. Compared with conventional fibre-optic sensors, FBG sensors have a number of distinguishing advantages. Significant progress has been made in applications to strain and temperature measurements. FBG sensors prove to be one of the most promising candidates for fibre-optic smart structures. This article presents a comprehensive and systematic overview of FBG sensor technology regarding many aspects including sensing principles, properties, fabrication, interrogation and multiplexing of FBG sensors. It is anticipated that FBG sensor systems will be commercialized and widely applied in practice in the near future due to the maturity of economical production of FBGs and the availability of cost effective interrogation and multiplexing techniques.

The use of Compton backscattering for the contactless measurement of the thickness of steel sections and similar dense materials up to 25 mm thick, when access is available only from one side of the sample, has been investigated. The expected intensity of back-scattered photons in a Compton thickness gauge has been estimated using a simple model, whose predictions have been verified and extended by the use of the GEANT3 Monte Carlo package which allowed the scattering geometry to be modelled accurately and the effects of multiple scattering to be estimated. The simulations have been confirmed by experimental measurements on steel samples 1 - 45 mm in thickness. With a 5 radioactive source, a rapid, reliable measurement of wall thickness can be obtained with steel samples up to 20 mm thick, but for thicker samples the absorption of backscattered photons limits the accuracy that can be achieved.

A new user-friendly method for measuring dilatation parameters of non-volatile liquids, based on an optoelectronic hydrolevelling sensor, is described. The system is capable of measuring a liquid column height with an accuracy of about and allows determination of the temperature dilatation volume coefficient for transparent liquids with an accuracy that depends on the used thermometer accuracy. The method is also suitable for specific mass or density measurements with an accuracy comparable to that obtained with the pycnometric method.

This paper describes a computer-controlled, multiple, constant, slow-displacement-rate tensile testing machine. The primary use of this machine is for investigating the durability of adhesive bonds. It also has application in the study of the hydrogen embrittlement of metals. A simple design facilitates manufacture of the mechanical parts of the test machine. The computer-controlled stepper-motor drive permits variation of the displacement-rates over a wide range while maintaining long-term stability. The computer also monitors the load and displacement during the course of the experiment. Several different displacement rates may be applied successively to a single specimen for defined regions of displacement. This capability allows the overall testing time to be reduced when determining the effect of the displacement rate on the elastic energy release rate, (also known as the crack extension force).

This paper describes a complete fast imaging microsystem for biological applications. The main goal of this microsystem is to provide, at a very low cost, a high-speed camera with an associated storage data system. We attained this goal by using a standard area CCD image sensor connected to a PC-compatible computer.

Low-amplitude ultrasonic signals are generated by a pulsed laser and detected either by optical techniques or by conventional piezoelectric transducers. A one-dimensional model of laser-induced displacements of the sample back surface is explained, taking into account the bulk absorption of laser light. Experimental confirmation of the model was attained. Excimer-laser-induced waves were detected by a stabilized Michelson interferometer and simultaneously by a piezoelectric transducer. By extrapolating the calibration, it is shown that displacements of order are generated with low-intensity laser pulses via a thermoelastic mechanism and that these can be detected by using a piezoelectric transducer.

Phase Doppler anemometry (PDA) is a laser optical method to determine particle diameters and velocities within two-phase or multiphase flows simultaneously and with high spatial and temporal resolution. The measured phase difference between two Doppler bursts is related to the particle diameter.

The proposed method for signal processing is based on a combined Hilbert transform and Fast Fourier transform (FFT) phase Doppler burst analysis. The numerical determination of the burst envelopes gives an estimation of the time delay between two related signals or, more generally, of the burst maximum position within the record time. This estimate is completed by the conventional FFT based signal analysis which is used to estimate frequency and phase difference. By this two-step estimation the restriction to the interval resulting from conventional signal processing can be avoided. The feasibility of the method in terms of an on-line determination of absolute phase differences is investigated by Monte Carlo simulations and demonstrated by means of a standard PDA arrangement with ball lenses rotating as spherical particles through the measurement volume. Phase differences up to were determined reliably.

In addition, algorithms to calculate Doppler frequencies and Doppler intensities, burst lengths and further characteristic parameters taking the signal quality into account are introduced and studied by Monte Carlo simulations. Based on these results validation strategies to reduce the influence of maltriggered bursts, trajectory or Gaussian beam effects on measurement results can be developed. Furthermore, by using the information of burst length and maximum position, optimized signal processing algorithms can be realized in order to achieve maximum accuracy in frequency, phase difference and signal-to-noise ratio (SNR) estimation.

A method of calibration of multiple-sensor probes and for interpretation of measurement signals is presented in a systematic way in this paper. The method is based on an extension of Jorgensen's directional response relationship. The measurements are not affected by deviations of the sensors from nominal construction angles or by interference and positioning imperfections. These errors are automatically balanced during the calibration phase. The use of a statistical approach reduces the random errors when the calibration data set presents a sufficient degree of overdetermination. The technique allows the determination of the influence cone as a function of the accepted uncertainty, by means of a post-processing procedure. The method allows an ad hoc angular calibration resulting in an error reduction when a very small variation in velocity direction is expected. The calibration and measurement procedures are very easy to perform. Finally the accuracy of the method for a three-sensor probes has been evaluated by comparison with acquired data and available nominal values.

This paper describes measurements made on a gravity drop conveyor using two arrays of axially spaced electrodynamic sensors to measure axial velocities close to the wall of the conveyor and velocity profiles both of flowing sand and of plastic beads. The level of correlation obtained using pixels is investigated. The velocity profile is combined with a tomographic concentration profile to estimate the mass flow profile, which is summed over the measurement cross section to estimate the mass flow rate. A calibration of the tomographically determined mass flow rate versus the actual mass flow rate is presented.

A technique for the rapid evaluation of the optical performance of wafers grown for fabricating visible-light-emitting diodes (LEDs) is presented. The technique is simple, non-destructive and can be used to qualify wafers prior to the relatively expensive device-processing stage. The technique resolves the problem resulting from the lack of correlation between photoluminescence measurements on as-grown materials and electroluminescence on the final structures. The lack of such correlation has been a pertinent problem for the material growth industry. The materials used for this investigation are those grown specifically for the fabrication of high-performance LEDs.

Since the type A evaluation of standard uncertainty according to the rules given in the ISO Guide to the Expression of Uncertainty in Measurement does not take into account the uncertainty that arises from the limited resolution of indicating devices, we show in this design note that the treatment of this problem calls for a quantity about which no statistical information is available; therefore, its uncertainty has to be derived from a type B evaluation.

A special pulsed instrument has been constructed for short-range remote nuclear quadrupole resonance experiments. The instrument was designed for detection of nitrogen-14 chemical compounds (in the low-frequency band 0.5 - 10 MHz). High sensitivity has been achieved by using a special construction of main sub-units and optimum experimental techniques. A description of the construction and performance of this instrument is given. As an example the results of the short-range remote detection of RDX are presented.

A multichannel photodetection system for the use in ultra-fast spectroscopy is presented. The system consists of pairs of photodiode-arrays combined with amplifier circuits and a gated analogue-to-digital converter. It allows real single-pulse analysis at repetition rates well above 1 kHz, gating in the submicrosecond regime and a sensitivity high enough to allow one to perform multichannel experiments at weak light energies.

Photon counting by means of a digital oscilloscope controlled by a computer is presented. For many applications this system can replace commercially available gated or multichannel photon counters.

An imaging photon detector (IPD) is routinely used with a Fabry - Pérot interferometer (FPI) for observations of 630 nm air glow above Beveridge () 50 km north of Melbourne, Australia. A fourfold improvement in signal-to-noise ratio allowed air-glow observations to be continued during the present solar minimum when the number of photons recorded by the detector often fell below . The cooling system is described. Cooling curves and samples of data recorded during a period of low-intensity air glow are presented.

Entries marked by * appear here for the first time. 1997 April 14 - 18 Introduction to Materials Analysis: Methods for Bulk, Surface and Structural Characterisation, Guildford, UK Details: Margaret Morgan, Short Course Organiser, Department of Materials Science and Engineering, University of Surrey, Guildford, Surrey GU2 5XH, UK. Telephone: 01483 259378, fax: 01483 259508, e-mail: M.Morgan@Surrey.ac.uk 19 - 22 Scanning 97, Monterey, CA, USA Details: Mary K Sullivan, FAMS Inc., SCANNING 97 Program Committee, Box 832, Mahwah, NJ 07430-0832, USA. Telephone: (201) 818 1010, fax: (201) 818 0086, e-mail: fams@holonet.net, WWW: http://www.scanning-fams.org 22 - 24 MIOP '97: Microwave and Optronics Conf. and Exhibition on Microwaves, Radio Communications and Electromagnetic Compatibility, Sindelfingen, Germany Details: NETWORK GmbH, Wilhelm-Suhr-Str., 14, D-31558 Hagenburg, Germany. E-mail: schrade@networkgmbh.de, WWW: http://www.networkgmbh.de 28 - 1 May Laboratory Health and Safety, Loughborough, UK Details: Joyce Bostock, Centre for Hazard and Risk Management, Loughborough University, Loughborough LE11 3TU, UK. Telephone: 01509 222175, fax: 01509 223991 * 29 - 1 May Council for Optical Radiation Measurements 25th Anniversary Conference, Gaithersberg, MD, USA Details: Jim Butler, tel: (301) 286 4606, Richard Young, tel (407) 422 3171 May 12 - 15 2nd Int. Conf. on Spectroscopic Ellipsometry, Charleston, SC, USA Details: David Aspnes, Physics Department, NCSU, Raleigh, NC 27695-8202. Telephone: (919) 515 4261, fax: (919) 515 1333, e-mail: aspnes@unity.ncsu.edu * 13 Laser-Based Characterisation of Surfaces, London, UK Details: Professor R J Dewhurst, DIAS, UMIST, PO Box 88, Manchester M60 1QD. Telephone: +44 (0)161 200 4886, fax: +44 (0)161 200 4911, e-mail: Richard.Dewhurst@umist.ac.uk * 13 - 16 Geotechnica, Cologne, Germany Details: Tony Pittman, KölnMesse, German Chamber of Industry and Commerce, 6th Floor, Carolyn House, Dingwall Road, Croydon CR0 9XR, UK 13 - 16 Control and Instrumentation Europe, Birmingham, UK Details: Miller Freeman Exhibitions Ltd, Marlowe House, 109 Station Road, Sidcup DA15 7ET, UK. Telephone: +44 (0)181 302 8585, fax: +44 (0)181 302 7205 18 - 23 Conf. on Lasers and Electro-Optics, Baltimore, MD, USA Details: Optical Society of America, Conference Services Department, 2010 Massachusetts Ave., NW, Washington DC 20036-1023, USA 18 - 23 Quantum Electronics and Laser Science Conf., Baltimore, MD, USA Details: Optical Society of America, Conference Services Department, 2010 Massachusetts Ave., NW, Washington DC 20036-1023, USA 19 - 23 Conference on Radionucleide Metrology and Its Applications (ICRM'97), Gaithersburg, MD, USA Details: J M R Hutchinson, Radioactivity Group, NIST, Gaithersburg, MD 20899, USA. E-mail: j.hutchinson@nist.gov 20 - 22 Surface Analysis '97, Albuquerque, NM, USA Details: R J Simonson, Sandia National Laboratory, PO Box 5800, MS 1349, Albuquerque, NM 87185, USA. Telephone: (505) 272 7631, fax: (505) 272 7304, e-mail: rjsimon@sandia.gov * 27 - 28 Optical Fibre Sensors for Smart Structures, Loch Lomond, UK Details: Craig Michie, Smart Structures Research Institute, University of Strathclyde, 204 George Street, Glasgow G1 1XW, UK. Telephone: +44 (0)141 5482625, fax: +44 (0)141 5531955, e-mail: w.c.michie@strathclyde.ac.uk June 9 - 11 10th Scandinavian Conf. on Image Analysis (IAPR), Lappeenranta, Finland Details: SCIA `97, Department of Information Technology, Lappeenranta University of Technology, PO Box 20, FIN-53851, Lappeenranta, Finland. E-mail: SCIA97@lut.fi, WWW: http://www.lut.fi/scia97 16 - 19 Machine Vision for Intelligent Vehicles and Autonomous Robots, Florence, Italy Details: Alberto Broggi, Dipartimento di Ingegneria dell'Inforazione, Universita` di Parma, I-43100 Parma, Italy. Fax: +39 521 905723, e-mail: broggi@CE.UniPR.it, WWW: http://WWW.CE.UniPR.IT/isata, http://WWW.spincom.com/isata July 6 - 9 CRYO 97 (Low Temperature Microscopy and Analysis), York, UK Details: Royal Microscopical Society, 37/38 St Clements, Oxford OX4 1AJ, UK. Telephone: +44 (0) 1865 248768, fax: +44 (0) 1865 791237 * 15 - 17 3rd Int. Conf. on Laser Metrology and Machine Performance, Huddersfield, UK Details: Lamdamap '97 Secretariat, School of Engineering, University of Huddersfield, West Yorkshire, HD1 3DH, UK * 20 - 25 Int. Conf. on Scanning Tunneling Microscopy/Spectroscopy, Hamburg, Germany Details: Professor Roland Wiesendanger, University of Hamburg, Institut für Angewandte Physik und Zentrum für Mikrostrukturforschung. Telephone: +49 40 4123 5244, fax: +49 40 4123 6188, e-mail: wiesendager@physnet.uni-hamburg.de August * 4 - 6 Ultrasonic and Dielectric Characterization Techniques for Suspended Particles, Gaithersburg, MD, USA Details: Dr Vince Hackley, NIST, Building 223, Room A256, Gaithersburg, MD, USA. Telephone: 301 975 5790, fax: 301 90 8729, e-mail: vince.hackley@nist.gov 25 - 27 Inter-noise '97, Budapest, Hungary Details: Congress Ltd, 11-1026 Budapest, Szilagyi Erzsébet fasor 79, Hungary. Telephone: 36 1 212 0056, fax: 36 1 156 6581 September 1 - 4 5th Triennial Int. Symp. on Fluid Control, Measurement and Visualization, Hayama, Japan Details: FLUCOME Desk, Kintetsu International, 7th Floor Takakyu Building, 19 Kanda Matsunaga-cho, Chiyoda-ku, Tokyo 101, Japan * 3 - 5 Modern Practice in Stress and Vibration Analysis, Dublin, Ireland Details: M Gilchrist, Mechanical Engineering Department, University College Dublin, Dublin 4, Ireland. E-mail: svcon97@ucd.ie * 8 - 10 Sensors and their Applications VIII, Glasgow, UK Details: Meetings and Conferences Department, The Institute of Physics, 76 Portland Place, London W1N 4AA, UK 8 - 12 World Tribology Congr., London, UK Details: Conference Services Department (C491), Institution of Mechanical Engineers, 1 Birdcage Walk, London SW1H 9JJ, UK 8 - 12 7th Int. Conf. on Laser Anemometry Advances and Applications, Karlsruhe, Germany Details: B Ruck, Institut für Hydromechanik, Universität Karlsruhe, Kaiserstraße 12, 76128 Karlsruhe, Germany. Telephone and fax: +49 721 608 3897 15 - 18 2nd Int. Coll. Micro-Tribology `97, Poland Details: Zygmunt Rymuza, Warsaw University of Technology, Institute for Design of Precise and Optical Instruments, Chodkiewicza 8/623, 02-525 Warszawa, Poland October 11 - 17 OSA'97 Annual Mtg, Long Beach, CA, USA Details: Optical Society of America, Conference Services Department, 2010 Massachusetts Ave., NW, Washington DC 20036-1023, USA 11 - 17 Interdisciplinary Laser Science Conf., Long Beach, CA, USA Details: Optical Society of America, Conference Services Department, 2010 Massachusetts Ave., NW, Washington DC 20036-1023, USA November * 4 - 6 BEMC '97, Teddington, UK Details: Stuart Pollitt, BEMC '97 Conference Chairman, Centre for Electromagnetic and Time Metrology, National Physical Laboratory, Teddington TW11 0LW, UK. Telephone: +44 (0)181 977 3222, fax: +44 (0)181 943 6098, e-mail: stuart.pollitt@npl.co.uk 1998 March 31 - 2 April Second Scientific Instrument Association Conf. and Exhibition, London, UK Details: SiA, PO Box 192, Watford, Herts WD1 8GF. WWW: http://www/interlab.co.uk/interlab July 13 - 16 9th Int. Symp. on Applications of Laser Techniques to Fluid Mechanics, Lisbon, Portugal Details: M V Heitor, Instituta Superior Técnico, Mechanical Engineering Department, 1096 Lisboa Codex, Portugal. Fax: 351 1 849 61 56 August 24 - 28 11th Int. Conf. on Experimental Mechanics, Oxford, UK Details: BSSM, Surrey Technology Centre, Surrey Research Park, 40 Occam Road, Guildford GU2 5YG, UK. Telephone: +44 (0)1483 295715, fax: +44 (0)1483 573704

This book is formed from the `fall out' of the Second Mediterranean Workshop and Topical Meeting on Novel Optical Materials and Applications. The editors have primarily aimed this work as a reference text for a broad spectrum of research scientists both in academia and industry.

Consisting of eleven chapters, the book does as the title suggests and exposes the reader to a variety of materials ranging from `conventional' organic materials for applications such as second harmonic generation to more esoteric materials exhibiting optical limiting behaviour via the phenomenon of reverse saturable absorption. Methods are described for preparation of all the novel materials covering areas such as crystal growth techniques and sample configuration for exploitation in envisaged optical devices.

In conjunction with this, the authors manage to describe a wide range of nonlinear optical measurements and experimental methods used for study. This is done in a manner that is generally useful to both experienced researchers and those who are venturing into this field for the first time.

Although a fair amount of prior knowledge is assumed, the topics covered do expand from basic concepts to include some of the more recent discoveries, making it reasonably easy to assimilate the updated information. Concentrating mainly on experimental aspects of nonlinear optics, excursions are made into the theoretical domain, including the world of quantum optics, thereby providing a refreshing change.

Throughout the book, attempts are made to show the applicability of this technology to the real world. Not surprisingly, therefore, the reader is referred to the concept of all optical communications. Bearing in mind the origins of this work, a good attempt has been made at providing a book that somewhat lives up to the original aim envisaged by the editors and therefore should be a useful addition to the bookshelf of anyone involved in this sphere.

The book is part of the NATO Advanced Science Institute Series and comprises papers given at an Advanced Research Workshop in Budapest in May 1995. There were five technical sessions together with a poster paper session organised by ISHM - Hungary. The conference provided an opportunity to bring together some of the well known work in the West with academe in the former eastern bloc. The emphasis was on miniaturization of sensors with incorporated control electronics for a wide variety of applications and the associated materials, reliability and processing issues.

The first session, entitled `Reliability Effects for MCM and Sensors', comprised seven papers culminating with a review by George Harman of the effect of material properties on reliability and yields of wire bonding. The other six papers were from universities and included non-destructive thermal analysis techniques, accelerated life testing and simulation for life prediction.

The next two sessions were on various MCM types, (MCM-C, ceramic MCM-D, deposited and MCM-L, laminate). Included was a report from the EU collaborative programme on high performance packaging (CHIPPAC), which described an MCM-C demonstrator for data processing and MCM-C and MCM-L demonstrators for a high speed telcom ATM switch. Other papers included materials technologies to produce buried passive components, CoB and MCM-L using thin film techniques on BCB boards.

A sensors session followed in which a variety of materials, fabrication techniques and applications were described for microsensors usually integrated into electronic circuitry to enable microprocessor controlled decision making and data storage. Properties measured included temperature, pressure, acceleration, ion concentration, light and humidity.

The final formal session was entitled `Systems Requirements and Integration'. A theoretical paper discussed moving from MCMs to microsystem modules by developing 3D structures and a second paper discussed the 3D medical demonstrator developed under the EU BARMINT project. The session was rounded off by an organizational paper on a taxonomy for prototyping and a paper describing a gas sensor combining MCM-D and silicon.

The conference was completed by eight poster papers on materials from academic institutions in Hungary. In particular, there was interest in producing conducting tracks on various substrate materials and making good ohmic contacts to III - V semiconductor devices. Finally, one paper discussed high temperature superconductivity which is an area that is now showing promise.

The importance of sensors in the areas of electronic engineering and applied research is becoming more and more substantial. A special case is the development of gas sensors due to the ecology problem. The new types of the gas sensors use the latest smart microelectronic technologies and computational treatment of signals. For productive application of these sensors one needs to know rather well the principles of the action and comparative characteristics of numerous gas sensors. The main feature of this book is that its topics are restricted to gas sensors based on metal-alloy oxides, acoustic wave sensors and image sensors.

The first type of sensor belongs to the most widely used type of gas sensors. In the book, however, the new materials, namely metal-alloy oxides, are proposed. It is important to stress that some of these new materials have rather low activation energies (0.18 eV for , 0.19 eV for LaO,6BaO,4MnO, 0.3 eV for ) - some of them even have no barrier. Therefore, it is possible to prepare sensors, acting at relatively low temperatures ( for sensing, for NO, etc). Peculiarities of the detection of gas mixtures (such as ) are also considered.

One of the main problems for gas sensors is long-term stability. Different models have been considered, which have to explain the origin of the gas sensitivity on the basis of the gas - metal-oxide reactions. Up to now, however, there is no completely adequate explanation of the observed electrical phenomena for the considered type of sensors. Nevertheless, the chemical reactions with creation of the surface ions and surface defects, backed with statistical theory developed by Engel, Haufe and Wolkenstein, have been considered as a good basis for explanation of the main principles of the action of the metal-alloy oxide gas sensors. Note that some difficulties appear under quantitative comparison of the parameters of the proposed systems with those developed earlier because the corresponding data are absent in the book.

Acoustic wave sensors (AWS) represent a relatively new direction in the gas sensor technique. The advantages of these sensors are operation at low temperatures (even below ), good reproducibility and long-term action and sensitivity to different adsorbed molecules. Because the surface acoustic wave (SAW) has two parameters - velocity of propagation and power of dissipation - it is possible to discriminate the moving adsorption process and adsorption with fixed position of particles. The degree of the perturbation of the wave velocity gives a quantitative way to determine the values of the adsorbed material (mass-sensors). The AWS have also selective properties. Other important applications of AWS are the vector voltmeter, phase interferometer, phase demodulator, etc. To fabricate AWS the electroacoustic materials (like quartz, ZnO etc) with a surface plated combined contact as generator and receiver of the acoustic signal are usually used.

For modern sensors it is desirable to have an image system (to have surface distribution of the gas sensitivity and to treat signals received from many-element selective sensors). In such cases the most sensitive electronic systems were used, such as a CCD scanner matrix.

Further material is devoted to electronic treatment of the sensor signals such as computations of artificial neural network, pattern recognition analyses and microsystem modelling. These only have an indirect relation to the topic of gas sensors.

In conclusion it is to be stressed that the book is useful both for scientists and for engineers of the corresponding fields.

Process tomography is the general name given to a range of techniques in which data are recorded using remote sensors and then manipulated to provide measurements of concentration distribution and flow phenomena within process equipment such as pipes and reactors. In principle, this technology can be used to identify, for example, the distribution of mixing zones in stirred reactors, and the position of interfaces within systems such as multiphase flows and complex mixtures during separation processes. Potential applications of process tomography fall into three broad categories. First, on-line, real-time sensing offers exciting developments in on-line process control. Second, visualization of concentration distributions as a function of time and flow phenomena within process vessels provides new insights into the operation of process equipment. Third, these visualizations yield data against which to validate the output of, for example, computational fluid dynamics simulations. This book is written in four sections: Principles of Process Tomography (Part I), Sensing Techniques (Part II), Data Processing Techniques (Part III) and Process Applications (Part IV). The articles are written assuming the reader has no particular specialization in the basic discipline of process tomography; the principles of the techniques are therefore discussed and other more detailed publications in each area are referenced.

Part I introduces the fundamental principles of process tomography in the context of the three broad sensor types which are based on transmission, diffraction and electrical measurements. Examples of typical process applications and the sensing methods that can be used to probe these systems are briefly described. The computational techniques that are used in process tomography are also introduced. Part II provides a more detailed description of sensing methods; the section is introduced with an overview of the relevant strengths of different tomographic methods in various process applications, with a particular focus on dual-modality and multi-modality tomographic imaging systems. Subsequent chapters address each of the major tomographic methods including impedance sensors for application to dielectric and conducting systems, mutual inductance tomography, electrodynamic sensors, ultrasonic sensors, microwave sensors, optical tomography and emission tomography.

Part III addresses data processing techniques in process tomography and includes chapters both on hardware and software requirements necessary for fast data capture and real-time image reconstruction and display. The principles upon which the image reconstruction algorithms required for each tomographic method are based are also described. The use of computer modelling in the design and optimization of process tomography sensors and systems, and in the interpretation of the sensor output data is discussed. The important topic of error analysis in the processing of tomography data is also addressed.

The book concludes with chapters on specific process applications. The examples included are the measurement of bed porosity distribution in particulate flows using photon transmission tomography; powder mixing studied by positron-emission tomography; pneumatic conveying and control using capacitance imaging; capacitance imaging of fluidized beds; mixing processes in fluids studied by light absorption and interferometric techniques; resistivity imaging of mixing, transport and separation processes and, finally, optical tomography as applied to the visualization of temperature distributions in flames.

Clearly, this book covers all the major aspects of development and application of process tomography. If there was a weakness it would be that the limitations of the various techniques and the theoretical limit to their application are not always obvious. For example, how does resolution vary throughout an image during typical process applications? How soon will we see the tomographic techniques described yielding real-time flow measurements? Undoubtedly, the answers to these questions are contained within this book but an overview of limitations and the expected short-term developments in process tomography in general would have been useful. However, this is a minor criticism and the text is essential reading for any researcher or industrial process engineer wishing to learn about the state-of-art in the field of process tomography. To those already working in the field it provides a useful collection of papers representing current practice in hardware, data analysis and process applications.

This paperback edition, which first appeared early in 1996, is a reprint of the hardback version published in 1992. Practical Surface Analysis comes in two volumes; Volume 1: Auger and X-ray Photoelectron Spectroscopy and Volume 2: Ion and Neutral Spectroscopy. Both are now in their second editions. Volume 1 is a revision of the very successful first edition published in 1983 - the `blue book' - which became something of a bible for the practising surface analyst working with the electron spectroscopies. Ion based techniques were sadly lacking from the blue book and we had to wait for the second edition before these equally useful spectroscopies were afforded the same treatment as the electron spectroscopies.

I have to admit that we have both editions of the companion volume in hardback but neglected to buy this volume when it was published. It is already proving to be extremely useful. I left the book lying around only to find people picking it up and reading it! It is a useful and well referenced introduction to this field for both the newcomer and practitioner alike.

The majority of the content of the book deals with SIMS in its various manifestations, as this is probably the most powerful of the surface analytical techniques. Low and medium ion scattering spectroscopies are covered but high energy ion scattering (RBS) is not, something of an omission in a work on practical surface analysis. There is a chapter on SNMS and, at the time the book was written, this was clearly the way forward. The conclusions of several other chapters also indicate the potential of SNMS. However, with the benefit of hindsight that comes from reading a book in 1997 that was conceived almost a decade previously, one can but observe how this promise still remains to be fulfilled.

Surface analysis has become a mature discipline; although the technology does progress it does so slowly now. This volume covers all the basic background to the subject and, whilst analysts will continue to find new and challenging applications and push the technology forward, the underlying science described in this book will not change. I am confident it will remain a benchmark for years to come.