Table of contents

A method for measuring the diameter of a small hole by a coordinate measuring machine is presented. A probe with a thin mechanical stylus is constructed and, on the basis of an elastic displacement transfer principle, the deflection of the stylus during measurement is automatically adjusted. Using this method, holes of diameter 0.3 mm were measured with an accuracy of the order of .

A newly developed fast-response portable gas-detector instrument is described. The principle of operation is that of the photo-ionization detector (PID), using radiation in the vacuum ultra-violet range. The instrument described here is referred to as the ultra-violet ion collector (UVIC, registered as a trademark) detector. Several innovative design features provide very substantial performance enhancements compared with other battery-operated portable PID devices and patents have been granted in the UK, the USA and Europe. The most notable advantages are with regard to speed of response and sensitivity; the UVIC detector provides a useful calibratable range of about 0.01-1000 ppm (by volume), with a response time of about 0.02 s. A generalized model of the operation of the detector is presented in the form of a set of equations that describe the ionization, advection and recombination processes taking place in the instrument. The model is generalized in the sense that the user may specify values of a wide range of parameters, so that the model can be used both to compare predictions with the performance of a specific instrument and to predict the performance of the instrument in other possible configurations and conditions in order to investigate design options. For validation of the model, values of the input parameters are measured when that is practicable; otherwise, they are estimated on some suitable basis. A software implementation of the model is tested using data obtained under a wide range of conditions both in the laboratory and in field experiments using atmospheric air as the carrier gas and propylene as the contaminant. These tests show that the model performs very well in predicting the response of the detector.

A non-contact laser sensor based on the ring optical cutting image method to measure the size and profile of the inner wall of a pipe is developed. The sensor consists of a laser diode light source, an optical ring pattern generator and a CCD camera. The optical ring pattern from the optical ring pattern generator is projected onto the inner wall of the pipe, which is then viewed by the CCD camera. Reasonable parameters according to the theory of light scattering and reflection are chosen to simulate and optimize the measurement system. The adaptive weighted average value filter and the subpixel technique on several-step computing and half Gaussian fitting are deployed to obtain the edge and the centre of the ring image in order to filter the noise of the image and raise the resolution of the measurement system. The experimental results show that the principle is correct and the techniques are realizable.

It is shown that the heated body temperature can be measured from the energy distribution of photoelectrons appearing in the photoelectric device which serves simultaneously as detector and analyser of the body radiation spectrum. The effective wavelengths of this temperature measuring technique cannot be chosen arbitrarily because they are functions of the temperature and must be measured. A technique for measuring the series of values of the effective wavelengths , which is necessary for estimation of the procedural error , has been proposed. The latter depends on the type of spectral characteristic of the photodetector, the energy photoelectron dispersion D in a retarding field and the emissivity of a heated surface . The formulae for the procedural error calculation are obtained and the latter has been shown to be less than that for measuring the temperature by conventional optical pyrometry methods and almost independent of temperature; -3 K for tungsten (when T = 1200-2600 K) and -5 K for platinum (when T = 1200-1800 K). The calculated results have been proved by series of experiments. A photoemissive pyrometer based on this method can be employed for temperature measurements when the exact meaning of a changeable emissivity is unknown as it takes place, for example, at pulse heating processes.

The problem of estimating the subsample time delay between two noise-corrupted narrowband signals is considered. Significant improvements to two previously proposed estimators, the MXS and MSX, are made. The performance of the revised estimators is assessed through simulation over a range from -10 to 20 dB, with four well known estimators, two of which are asymptotically maximum likelihood (the direct correlator and the average square difference function) and the other two are windowed versions of them (the generalized cross-correlator and generalized least squares). Also, the estimators are applied to ultrasonic experimental data at three different SNRs. At low SNR, the MXS/MSX estimators are shown to exhibit a significant reduction in the variance of the estimates.

A new technique for the measurement of the concentration of gas species is presented. The method is based on absorption spectroscopy in the infrared region utilizing a high-power broad band amplified spontaneous emission source from an optical fibre. Vibrational bands of gas in the range 1.9-2.1 m were measured and the relative intensities of bands were calibrated in terms of concentration. The amplified spontaneous emission from a co-doped silica fibre pumped near 800 nm was used as a light source that consisted of the transition of the ion and the transition of the ion with a full width at half maximum of 225 nm and total output power over 1 mW. The technique has potential for the simultaneous detection of multiple gas species due to its high spectral energy density over a wide wavelength band in the infrared where the vibrational overtones of gas molecules are located.

A new fibreoptic reflectometric technique for the automatic detection and measurement of surface cracks is proposed, described and analysed. A relationship between the system output image and the surface crack distribution is obtained from theory and a crack measurement principle is derived. Analysis of the experimental data obtained using a first laboratory prototype has validated the proposed measurement principle. The results of a second generation prototype confirm that the technique promises to be a valuable tool in practical inspection tasks.

A 15 MHz bandwidth active homodyne fibre-optical interferometer for remote detection of laser-induced ultrasonic waves in metallic and non-metallic targets is reported. The fibre interferometer design and associated electronics are described in sufficient detail for it to be easily constructed. The interferometer uses a low-power He-Ne laser and the reflected signal from the natural surface of the target at a distance of 200 mm. Despite its use of an open air path in the sensing arm and an all-fibre design, the interferometer achieved a single-pulse noise equivalent displacement of 0.4 nm and a figure of merit of 0.1 pm .

A differential plane mirror interferometer developed at the NPL has been built into a system designed to calibrate and certify displacement transducers. Two electrical signals generated from the optical outputs of the interferometer and a voltage output of the transducer to be calibrated are read by a computer and mathematically analysed in order to calculate the proportionality and linearity of the displacement transducer. In order to realize the highest measurement accuracy from the interferometer the interferogram signals are analysed and corrected by an optimizing routine in order to interpolate the fractioning of the optical fringes accurately. Without computer optimization of the signals a standard deviation of measurement of a few nanometres is typical, whereas after optimization this is reduced to a fraction of a nanometre. The interferometer has been used to calibrate a high-precision capacitance probe and the results of these measurements are shown and discussed.

A compact scanning-probe microscope (SPM) using an ultrasmall distortion sensor has been developed for versatile implementation. The sensor is based on a coupled-cavity laser (CCL) consisting of a Fabry-Perot laser diode monolithically integrated with a photodiode, an external mirror on a cantilever, and a small ball lens for laser-beam collimation. With the CCL stabilized by a simple mechanically controlled negative-feedback loop, the temporary distortion of the cantilever's sharp tip in response to the surface structure is measured with a vertical accuracy of 0.8 nm. The SPM was verified by imaging tracking grooves of an optical disk.

A theoretical treatment of an electron-optical scheme is suggested. The system can be used for simultaneous registration of energy and angular distributions of charged particles (electrons or ions) emitted from a small source. The scheme is based on an axially calculated symmetrical electrostatic field. The source has the form of a short interval of the axis of symmetry. The system consists of a novel type of electrostatic energy analyser and an usual planar position-sensitive detector joined to it.

By processing a set of three phase-shifted interferograms one can determine the actual phase steps between recordings by assuming that the calculated map of the intensity offset has the smallest pixel to pixel variations when the supposed values of the phase steps match the actual ones. Based on this principle a new statistical self-calibrating algorithm for phase-shift interferometry is presented. Numerous tests were carried out to check the ability of the new algorithm to find the correct values of the actual phase steps. Algorithm limitations are discussed.

A measurement procedure is reported for the power density, internal current density and plasma voltage along the flow direction of a discharge section of a fast-axial-flow laser. The rf discharge has a rectangular cross section and a narrow electrode gap for operation at high pressure. Both cw and time resolved pulsed measurements have been made.

A simple XUV transmission grating spectrograph operating in the wavelength range 3-90 Å with sub-ångström resolution without using any XUV imaging optics is described. This is based on a free-standing gold microstructure grating of 2000 Å period in normal incidence geometry. A spectral resolution of 0.6 Å is obtained by optimizing the slit aperture, the source-to-grating distance and the grating-to-detector distance. Electron temperatures deduced from analysis of the spectrum of a laser-produced magnesium plasma using a plasma spectroscopic code are consistent with theoretical considerations. The spectral range can be extended to higher wavelengths by using a larger detector. The simple geometry and ease of operation of the spectrograph should make it useful in many experiments such as those involving plasma-based XUV lasers and odd-harmonic generation in the XUV spectral region using ultra-short laser pulses.

Acoustic pulse reflectometry is a non-invasive technique for measuring the internal dimensions of tubular objects. A sound pulse is produced using a loudspeaker and injected into the object under investigation via a source tube. The resultant object reflections are recorded by a microphone embedded in the wall of the source tube. Analysis of the reflections yields information about the bore profile of the object. At present, there is a restriction on the length of object that can be measured using the standard reflectometer. This restriction arises because after the object reflections pass the microphone they undergo further reflection at the loudspeaker. These source reflections return to the microphone as unwanted signal. Hence, there is only a finite time over which the object reflections can be accurately recorded which, in turn, limits the length of object that can be measured. In this paper, a method for removing the length restriction is described. The method involves the cancellation of the incoming object reflections at the loudspeaker, thus preventing the formation of source reflections. The results achieved indicate the potential of the method for accurate measurement of longer objects.

This paper describes a novel electrically passive fluid level gauge. It is based on a one-dimensional low-frequency acoustic gas resonator. The acoustical power is delivered to the resonator an the acoustic waveguide and a fibre-optic microphone is used as an acoustic pressure sensor. Distances of over 100 m between the electrically passive sensor and the electrically active controller were achieved in practice. The proposed method can be successfully implemented in systems where problems of residues, deposits, foams, etc, can be expected.

This paper presents a two-phase flow direct imaging sensor, based on multiple electrical impedance measurements. The electrode configuration is optimized to provide imaged information on the phase distribution within the probe's sensing volume. As a consequence, the time evolution of the flow topology can be represented by simply plotting the signals corresponding to the peripheral impedance measurements, and therefore needs no numerical reconstruction from the experimental data. Several transient tests are performed in a two-phase air-water loop. They demonstrate that the sensor exhibits not only large structures such as slugs and plugs, but also some finer details such as the wavy or rugged interface in stratified flow, or liquid film drainage during the transition between intermittent and annular flows. The methodology proposed in this work constitutes a simple and inexpensive alternative to tomographic imaging techniques, and is thus fully adapted to online process monitoring of multiphase flow systems.

The effect of a bubble on the virtual current of an electromagnetic flow meter is studied numerically with the bubble at various positions along the pipe axis of the flow meter. To solve the distribution of the virtual current, a two-dimensional (2D) assumption is used. The domain is divided into sub-domains. In each of the sub-domains, the potential of the virtual current is expressed in series with unknown coefficients. An alternating method is used to find the unknowns. Various bubble sizes and bubble positions along the pipe axis of the flow meter are considered in the calculation. The change of the virtual current caused by the existence of the bubble is evaluated using deviation and asymmetry.

A simple laminar pipe-flow method for hot-wire anemometer calibration in the low-velocity range is described. The stable flow was generated by draining water from an air-tight container at a constant rate. The influence of humidity variations between calibration and application was analysed. Calibration results were compared with results from another available device. One measurement of the laminar pipe-flow velocity profile using the calibration results was also performed. The present method was demonstrated to be a simple, but accurate, means for low-speed hot-wire anemometer calibration.

In turbomachinery applications, optical access needed for laser anemometry (L2F) measurements must be provided by curved glass windows to avoid introducing disturbances into the flow. However, the curvatures lead to optical distortions of the laser beams which prevent the creation of acceptable foci. These distortions can be eliminated by inserting a simple and inexpensive corrective window between the frontal lens of the anemometer assembly and the shroud window. First, a simplified analytical method is presented to determine the geometric characteristics and the position of this corrective window. Then, a more sophisticated numerical method is described and applied to the case of an axial transonic compressor currently under investigation.

This paper describes a high-speed video acquisition system designed for visualization in fluid mechanics. The need for a non conventional video system is shown. The architecture of a typical experiment of flow visualization is discussed along with the whole video acquisition system. The camera, built around the EEV CCD37 sensor, with a resolution of and a rate of 100 non-interlaced images per second, is then described in detail. Finally, examples of images obtained with our system are given to illustrate the most typical situations.

Measurements of effective angles of crossed hot-wire probes to determine their efficacy for characterizing turbulence, particularly the vertical component and shear stress, in a boundary layer with mean wind speeds in the range 0.3-3 m have been made. These results suggest that the effective angles change markedly at low wind speeds, but proper calibrations and application of effective angles which are functions of the wind speed, although tedious, will yield results comparable to those from a laser-Doppler anemometer (LDA).

This paper describes the development and application of a soft x-ray flash radiography technique. A very compact soft x-ray flash source has been specially designed for these studies. The table-top x-ray source developed in this work emits strong doses, up to one roentgen at the output window, of x-ray photons, with most of them in the characteristic lines of the anode material (photon energy in the energy range 5-10 keV), in pulse of 20 ns FWHM with an x-ray emission zone smaller than . All these characteristics make this source attractive for the x-ray radiography of high-speed phenomena, down to ten nanoseconds duration and/or for the media presenting weak absorption for the harder x-ray photons emitted by more conventional flash x-ray systems. Argon streams in ambient air were chosen as a typical case to enlighten the potentialities of this method. Single-shot radiographs of such an argon jet through rectangular nozzles were obtained. No attempt of quantitative measurement of local density in the argon stream has yet been performed, only the qualitative structure of the jet has been investigated. Nevertheless, these preliminary results enable us to state that the diagnostics of gaseous or plasma media, even at rather low pressures, can proceed using soft x-ray flash radiography.

A simple method to measure the thermal expansion coefficient using a surface-mounted Bragg-grating sensor is presented. This method uses a single, uniform-pitch Bragg-grating fibre that is only partially glued onto the specimen. To prevent cross talk between the two Bragg wavelengths reflecting from glued and free sections, a preloading is applied to the fibre before it is partially glued onto the specimen. After release, two Bragg wavelengths are observed. The Bragg wavelength reflected from the sensor section not glued onto the specimen is used to measure temperature variations; the Bragg wavelength reflected from the sensor section glued onto the specimen is affected by variations in thermal strain. Therefore, the thermal expansion coefficient can be determined by calculating the spectral separation of the two Bragg wavelengths. The measured thermal expansion coefficient of an aluminium plate is for every C in the range 35-C. It is in good agreement with the value of for aluminium. However, the scheme will lead to incorrect results if there is a temperature gradient across the Bragg grating or if the material to be measured is inhomogeneous.

A method based on nondestructive microwave characterization is used for simultaneous determination of the bulk density and moisture content of shelled corn. This method can be applied regardless of the measurement technique and thus considerably simplifies the calibration procedure. Calibration equations, both for the bulk density and for the moisture content, are given, together with the standard error of performance (SEP) at several frequencies in the range 11-18 GHz and three temperatures, 14, 24 and C. The bulk density, ranging from 695 to , can be determined with SEP in the range 11-. Neither the sample moisture content nor its temperature are required in order to determine the bulk density. The moisture content ranging from 9% to 19% on a wet basis, can be determined at each temperature without knowledge of the bulk density with SEP of less than 0.5% moisture content. Results of an error analysis of the measurements show that about half of the total uncertainties in bulk density and moisture content can be considered systematic errors and thus they are correctable.

The fabrication of prototype thick film silver-silver chloride electrochemical reference electrodes is described. Combinations of commercially available and proprietary thick film pastes have been used in their construction in a multi-layer planar configuration modelled upon the structure of the classic single junction silver-silver chloride reference electrode cell. Several variations in the basic electrode design were fabricated, involving combinations of one of three different paste formulations for the silver-silver chloride layer coupled with one of two combinations of paste formulation for the salt containment matrix. The relative performances of these different versions of reference electrode were evaluated in terms of their chloride ion sensitivity, hydration times required to achieve a stable potential and usable lifetime. It is shown that, depending on the processing methodology employed at certain stages in the fabrication of these devices, a large degree of variation in characteristics can be achieved and therefore exploited in the design of reference electrodes suitable for a range of specific applications.

This paper describes a structurally modified British Pendulum Skid Tester fitted with an optical encoder (2500 pulses per revolution), pulse timing electronics ( resolution) and a computer interface (IBM compatible PIO card). A spring-loaded rectangular slider attached to the foot of the pendulum is driven across a horizontal surface at speeds of up to . By measuring changes in the angular velocity of the pendulum, it is possible to calculate the loss of energy due to friction with 1 mm linear resolution. Values for the path-averaged coefficient of friction for thermoplastic and elastomer sliders can be determined with a precision of around 1%, enabling highly reproducible studies of the influence of slider wear and surface condition on friction losses to be carried out. Energy loss profiles measured during the passage of the slider over the surface can reveal variations in surface roughness as well as details of the slider/substrate interaction. Force profiles for natural rubber sliders travelling over smooth surfaces at speeds in excess of show well-defined stick-slip oscillations in the force of sliding friction.

The condition of steel components embedded within reinforced and pre-stressed concrete is one of the most important factors in determining the useful life of structures built from this material. Civil engineers often use magnetic methods to determine the approximate depth and diameter of steel bars and tendons. However, due to the magnetic field distribution around conductors, direct two-dimensional imaging by such methods is subject to severe blurring. A precise deconvolution expression has been developed that eliminates blurring in the one-dimensional case. By taking the Fourier transform of the magnetic field distribution, an analytical expression has been obtained for the spatial frequency response. The deconvolution algorithm was applied in its discrete form to the measurement profile of a magnetic field, in which several wire loops, representing reinforcement bars, were excited with an AC voltage. The deconvolution yielded a highly accurate reconstruction. Further work suggests that this method could be extended to the two-dimensional case. The problem of measurement misalignment in relation to the discrete-space Fourier transform is also addressed.

A triple quadrupole mass spectrometer (TQMS) system utilizing the collision-induced dissociation process has been constructed for studies of gas-phase combustion chemistry of energetic materials under various conditions of pressure and incident laser heat flux. A unique feature of the TQMS system is its capability to differentiate species at the same mass-to-charge value and to identify chemical structures of the gaseous species evolved from the energetic materials, through the recognition of the fragmentation characteristics of chemical functional groups in species. Two different settings for high and low collision energy modes were developed for the daughter mode of operation. A calibration method at the two settings in the daughter mode was also developed for the quantification of the measured species. The TQMS system developed also includes integrated vacuum system, quartz microprobes for gas species sampling, customized software for data acquisition and data reduction. Typical results are presented to illustrate the methods used to differentiate the measured species and to identify their chemical structures.

A novel colorimetric method using a new optical detector for seawater pH determination is presented. The used detector is a buried double p-n junction (BDJ) structure which provides two photocurrents whose ratio is sensitive to spectral changes. The BDJ detector directly picks up the transmitted signal for the determination of the solution pH. Both measurements and simulations have been performed to validate the suggested method which requires no spectrophotometer or colorimeter. The method, based on the concept of intensity-independent photocurrent ratio seems to provide a solution to the problems in development of compact, low cost, robust and reliable pH measuring systems. Such systems may be cost effective and miniaturized since the required BDJ detector can be monolithically integrated with electronic circuitry on the same chip in conventional CMOS technology.

An ultrasensitive noise measurement system has been used to study the intrinsic fluctuations in microwave circulators and isolators. The key element of the measurement system is a carrier suppression interferometer which contains the device under test in one of its arms. The interferometer is used to cancel the carrier at the input of a low noise microwave amplifier in the readout system. Fluctuations in the device under test are then registered by the readout system which has an effective noise temperature of 360 K and is almost equal to its physical temperature. This corresponds to a phase noise of with 20 dBm of microwave power incident on the device under test. We show that this is sufficiently low to measure intrinsic fluctuations in low noise microwave components such as ferrite circulators and isolators. The noise of the microwave isolators was shown to be independent of both, microwave power and temperature in the region +10 to and -10 to . We have also measured the phase shift in microwave isolators as a function of external magnetic fields and temperature to determine the effects of environmental fluctuations.

A first-order axial electronic gradiometer having a baseline of 10 cm was constructed by assembling two rf SQUID magnetometers with coplanar tank resonators, each having a white magnetic field resolution of about at 77 K. The gradiometer's near-field resolution was about , including the Dewar flask's noise. A peak-to-peak noise level of 3 pT was obtained in the bandwidth 0.016-250 Hz. Magnetocardiographic (MCG) measurements were performed using this bandwidth. Measurements on human subjects have been conducted in a magnetically shielded room of moderate shielding factor. Using the signal either of the lower magnetometer or of the gradiometer, high-quality heart signal traces could be collected, which were suitable for diagnostic use. A team of physicians, assisted by two of the authors, used the equipment over 10 months to perform MCG measurements in a medical study of about 80 clinical patients with cardiac arrhythmia problems and healthy persons. The system's performance was stable over that whole period.

A method for the accurate computation of the current densities produced in a wide-runged bi-planar radio-frequency coil is presented. The device has applications in magnetic resonance imaging. There is a set of opposing primary rungs, symmetrically placed on parallel planes and a similar arrangement of rungs on two parallel planes surrounding the primary serves as a shield. Current densities induced in these primary and shielding rungs are calculated to a high degree of accuracy using an integral-equation approach, combined with the inverse finite Hilbert transform. Once these densities are known, accurate electrical and magnetic fields are then computed without difficulty. Some test results are shown. The method is so rapid that it can be incorporated into optimization software. Some preliminary fields produced from optimized coils are presented.

ZnO surge arresters have become widely used for overvoltage protection in high-voltage power systems. In order to examine response in the nanosecond regime, a toroidal element from a practical arrester has been incorporated into a coaxial line and subjected to transient voltages of 5 ns risetime and 8.8 kV prospective peak. It is shown that the current in the element may be deduced from terminal voltage measurements without use of a current transducer. For the test voltages used, the element showed a high-permittivity capacitive response with no measurable relaxation time or significant voltage nonlinearity; the non-uniform electric field distribution in the element in the pre-conduction phase thus remains undistorted. Such coaxial configurations could have practical applications in power supply, communications or data systems.

A top-loading sample chamber tube, radiation shield and the vacuum shroud for interfacing a closed-cycle helium refrigerator for use with a vibrating sample magnetometer have been designed and fabricated. A lowest temperature of 12 K is achieved at the sample. The eddy current effects in the copper sample chamber tube are minimized by the use of an electrically insulating epoxy resin medium. The sample temperature is measured by a GaAlAs diode sensor attached on a sensor mount which is inserted into the sample zone and kept in helium atmosphere. The vibrations of the cryocooler's cold head are isolated from the vibrating sample magnetometer's head by incorporating a bellows. Using this facility the magnetic transitions of some rare earth elements have been measured and compared with the literature data.

The gain of a type 226EM electron multiplier with BeCu dynodes having a cylindrical shape was measured in terms of its dependence on the position where ions bombarded the surface of the first dynode. This position-impact dependence of the gain exhibits a great decrease if the bombarded position on the first dynode's surface departs from the input window into the second dynode region. The presented results show that the gain of any 226EM as well as those of other electron multipliers equipped with curved first dynodes depends not only on the charge state and the kinetic energy of detected ion species but also on the ion beam's density profile and on the impact position on the first dynode's surface. An application of the 226EM for measurement of an ion beam current is discussed. A beam of ions with a kinetic energy of 690 keV was used as a probing beam.

Many applications of lasers in research and industry require that a slave laser can be frequency locked at some selectable offset frequency from a stable reference laser. Conventionally an optical phase lock circuit has been used to provide this frequency lock. In some applications there is no requirement to ensure phase coherency between the two lasers, and in these cases, the high bandwidth requirements of a phase-locked loop make the circuit much more complicated than necessary. We describe a much simpler frequency-locking circuit, based on a commercial frequency-to-voltage converter, which is capable of reducing frequency fluctuations between the lasers to less than 400 Hz for time scales longer than 0.1 s.

A technique for reducing the effect of ambient light on ecartometry for a continuous wave laser-illuminated target is suggested. In the technique, two sets of photoresistors are used in combination. One set replaces the feedback resistors of the four-quadrant laser detector preamplifiers whose resistances are controlled by the other set. All the experiments were carried out indoors with indoor ambient light levels related to those for the outdoors. The suggested circuit is expected to function in ambient light in excess of lux.

This design note describes an inexpensive system used to control the radiofrequency field generated by magnetic resonance coils. The device is built around three main modules, a sequencer, a modulator and a phase-sensitive detector. This system permits one to detect the radiofrequency field at each point of the region of interest using a pick-up coil, without the requirement of a magnetic resonance spectrometer. Examples of radiofrequency field distributions obtained at 85 MHz are given.

Chris Fortunko has been a member of the Editorial Board since 1996. With his untimely death, we have lost a good friend and valued colleague who worked selflessly in the service of the journal. As our tribute to his memory, we publish this obituary written by his close colleague, Harry McHenry.

Julian D C Jones Honorary Editor

Chris Fortunko passed away on 27 June 1998 after a heart attack. He was born in Siemianowice, Poland, on 7 December 1948 and emigrated to the US in 1964. Chris received his BS degree from Tufts University in 1970 and a PhD in applied physics from Stanford University in 1975. At Stanford, he studied surface-acoustic-wave delay lines under Professor H John Shaw in the microwave laboratory. His research involved considerable work on wave propagation in anisotropic media, broadband transducer development, impedence matching and instrument design.

In 1976, Dr Fortunko joined the technical staff at the Rockwell International Center in Thousand Oaks, California. As a member of the ultrasonics applications group, he received six patents for the development of high-performance circuitry for ultrasonic inspection systems. He made significant contributions to the development of electromagnetic acoustic transducers, eddy current instruments, and inspection systems for quality assurance.

Dr Fortunko worked for the National Institute of Standards and Technology from 1980 until 1983, and from 1989 to 1998. From 1983 to 1988, he was Chief Scientist and Engineering Manager for the Aerojet Ordinance Company working on electronics and sensor applications. At NIST, Dr Fortunko was supervisor of the Materials Characterization Group in the Materials Reliability Division. His unique contribution was to bring the discipline and rigor of measurement science to the less orderly world of material testing and nondestructive evaluation (NDE). Specific accomplishments include the development of ultrasonic instruments for materials characterization, gas coupled ultrasonic inspection systems, and standards for nondestructive evaluation.

Dr Fortunko was a leader within the NDE community. He held adjunct faculty appointments at Johns Hopkins University and Iowa State University. He served on the Editorial Board of Measurement Science and Technology, the Industrial Advisory Board of the Center for Nondestructive Evaluation at Iowa State University, and the NDE Group of the Interagency Committee on Materials Technology. Dr Fortunko published about 100 technical papers, chaired the Gordon Research Conference on NDE, and was the US organizer for the European American Workshop on Determination of Reliability and Validation Methods on NDE (1997). In 1993, he received the Department of Commerce Silver Medal award for developing ultrasonic instruments for evaluating the quality of advanced materials.

Dr Fortunko is remembered for his remarkable scientific knowledge and his broad technical experience. He used these skills to provide leadership for his research group at NIST and for the worldwide NDE community. He will be sorely missed by his colleagues, friends and family. He leaves his wife Mira, daughter Jacqueline and brother Andrew.

Harry McHenry July 1998