Showing papers in "Journal of Physics E: Scientific Instruments in 1976"
TL;DR: In this paper, a new calculation following traditional methods is proposed for deducing optical constants and thickness from the fringe pattern of the transmission spectrum of a thin transparent dielectric film surrounded by nonabsorbing media.
Abstract: A new calculation following traditional methods is proposed for deducing optical constants and thickness from the fringe pattern of the transmission spectrum of a thin transparent dielectric film surrounded by non-absorbing media. The particular interest of this method, apart from its easiness, is that it makes a directly programmable calculation possible; the accuracy is of the same order as for the iteration method.
1,499Â citations
TL;DR: An analysis is presented of existing and new multi-orientation and multiprobe techniques and it is shown how they can be used to remove systematic and variable errors.
Abstract: There is an increasing demand for more accurate surface metrology instruments and for techniques which will allow complicated or large parts to be measured in situ. An analysis is presented of existing and new multi-orientation and multiprobe techniques and it is shown how they can be used to remove systematic and variable errors.
248Â citations
TL;DR: In this paper, a simple relation is obtained between the film thickness variation and the skin friction distribution, and the results confirm the theory and show that the method gives reasonably accurate measurements of skin friction distributions in low speed flows.
Abstract: An oil film on a solid surface moves under the action of gravity or of the pressure gradient and skin friction resulting from the flow of air over the oil surface. Such oil flows are studied experimentally and theoretically. If the film is thin enough, the dominant force is the skin friction, and a simple relation is obtained between the film thickness variation and the skin friction distribution. The other forces give a perturbation which may be estimated and which decreases with time. The appropriate film thickness is of the order of 10 mu m and so is conveniently measured by interferometry. Experimental results confirm the theory and show that the method gives reasonably accurate measurements of skin friction distribution in low speed flows.
246Â citations
TL;DR: In this article, a fast scanning method of producing proton density images by NMR is described which could be useful for the examination of plants as well as biological tissue in vivo.
Abstract: A new fast scanning method of producing proton density images by NMR is described which could be useful for the examination of plants as well as biological tissue in vivo. Examples are given of images produced from small samples of plant and biological material. Calculations show that imaging equipment, if scaled to deal with objects of human proportions, could under ideal conditions produce pictures close to television quality in times ranging down to a few minutes by this method.
174Â citations
TL;DR: In this paper, the amplitude range for vibration measurement by time-average recording in electronic speckle pattern interferometry (ESPI) has been extended by sinusoidal phase modulation of the reference wave.
Abstract: The amplitude range for vibration measurement by time-average recording in electronic speckle pattern interferometry (ESPI) has been extended by sinusoidal phase modulation of the reference wave. The technique is, in part, similar to the reference wave modulation technique known from holography. The low resolution of the ESPI system results in a greater need for an extension of the measuring range. In addition, the technique is more convenient to use combined with ESPI, because of the instantaneous presentation of interferograms by this system. The modulation technique also provides information about the vibration phase. Fringe patterns illustrating applications of this technique are presented.
92Â citations
TL;DR: In this article, the application of error separation techniques to roundness measuring instruments is investigated experimentally, using digital computers, and the accuracy of such techniques is substantiated by comparative measurements with two independent multi-orientation systems.
Abstract: The application of error separation techniques to roundness measuring instruments is investigated experimentally, using digital computers. The accuracy of such techniques is substantiated by comparative measurements with two independent multi-orientation systems. Results obtained with these and other systems confirm that the errors of conventional roundness measuring instruments can be reduced by a factor of ten or more and meaningful polar graphs obtained at radial magnifications of up to one million. These advances in accuracy can be achieved in relatively poor working environments and with little extra skill on the part of the instrument operator.
81Â citations
TL;DR: In this paper, an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure is described, which is based upon the transient hot wire principle.
Abstract: The paper describes an apparatus for the measurement of the thermal conductivity of non-conducting liquids under their saturation vapour pressure. The instrument, which is based upon the transient hot wire principle, has been designed so that the measuring element conforms as closely as possible to an infinite line source of heat in an infinite fluid. Under these conditions the thermal conductivity of the liquid can be determined from the slope of a plot of the temperature rise of the heating element against the logarithm of time. The measurement system has been arranged so as to provide as many as 60 points on this plot for any particular thermodynamic state of the fluid under investigation. The reproducibility of the instrument is of the order of 0.03% and the precision of the measurements is estimated as +or-0.1%. Owing to a lack of a suitable theory for the effects of radiative heat transfer, the accuracy of the thermal conductivity values cannot be defined unequivocally, but a reasoned upper bound is +or-0.3%. Preliminary results are presented for n-heptane at three temperatures in the range 20 to 30 degrees C.
80Â citations
TL;DR: The effect of pressure at low temperature (166.8K) upon the R1 and R2 lines of ruby has been investigated for the first time to establish a calibration for use in high-pressure/low-temperature work as discussed by the authors.
Abstract: The effect of pressure at low temperature (166.8K) upon the R1 and R2 lines of ruby has been investigated for the first time to establish a calibration for use in high-pressure/low-temperature work. A reinvestigation of the behaviour of R1 and R2 at ambient temperatures and at pressures up to ca 70 kbar supports previous work on the calibration under hydrostatic conditions but shows that in a 4:1 methanol:ethanol mixture conditions become nonhydrostatic at lower pressures (ca 50 kbar) than claimed (ca 100 kbar). The importance of monitoring both R1 and R2 is emphasised as their relative shifts are sensitive indicators of the presence, and approximate magnitude, of non-hydrostatic stress components. It is shown that although changes in half-bandwidths are also associated with development of shear stress, their use in estimating gradients is extremely hazardous and can indicate values greatly in excess of the known shear strength of the material.
80Â citations
TL;DR: In this article, the energy resolution and transit time spread of the 180 degrees hemispherical electrostatic analyser for nonrelativistic electrons or ions have been computed in terms of the dimensions of the analyser and the parameters describing the input particle beam for a large range of possible configurations.
Abstract: The energy resolution and transit time spread of the 180 degrees hemispherical electrostatic analyser for nonrelativistic electrons or ions have been computed. The results have been expressed in terms of the dimensions of the analyser and the parameters describing the input particle beam for a large range of possible configurations. The predictions for a particular electron analyser have been tested experimentally and good agreement has been obtained.
66Â citations
TL;DR: The role of quartz crystal oscillators which are slaved to active and passive atomic frequency standards is emphasized in this paper, where the basic concepts involved in atomic frequency standard and terminology commonly used in this field are summarized.
Abstract: The principles of operation of atomic frequency standards are described. Details are given of their physical construction. Their characteristics as well as their availability, principal uses and impact are specified. The basic concepts involved in atomic frequency standards and the terminology commonly used in this field are summarized. The role of quartz crystal oscillators which are slaved to active and passive atomic frequency standards is emphasized. The traditional atomic frequency standards are reviewed, i.e. the hydrogen maser, the caesium beam tube and the passive rubidium cell frequency standards.
58Â citations
TL;DR: In this article, the authors describe a method of producing uniform high pressure glow discharges suitable for nanosecond excitation of gas lasers and for low inductance, high voltage switching applications.
Abstract: The authors describe a novel method of producing uniform high pressure glow discharges suitable for nanosecond excitation of gas lasers and for low inductance, high voltage switching applications. The principle has been adapted to a variety of different gases with established and potential laser applications and is particularly well suited to the stabilization of transverse discharges. Stabilization can be effected over a wide range of overvoltages for different gas pressures and electrode separations.
TL;DR: In this article, a circuit is described which varies the relative alignment of the mirrors of a repetitively scanned plane Fabry-Perot interferometer until the transmitted light intensity of the strongest spectral component is maximized.
Abstract: A circuit is described which varies the relative alignment of the mirrors of a repetitively scanned plane Fabry-Perot interferometer until the transmitted light intensity of the strongest spectral component is maximized. Using this scheme an interferometer can be completely stabilized against all drifts arising due to thermal and mechanical instabilities.
TL;DR: In this article, experiments were performed to record Fourier transform holograms with carbon Kalpha X-rays at 4.48 nm, and attempts were made to reconstruct the object from the holograms using He-Ne laser light.
Abstract: Experiments were performed to record Fourier transform holograms with carbon Kalpha X-rays at 4.48 nm. Attempts were made to reconstruct the object from the holograms with He-Ne laser light. The results are compared with those obtained from holograms that were recorded with a visible analogue source of similar coherence conditions.
TL;DR: In this article, sets of coils providing linear gradients of any desired direction are described, and the coils are placed in the NMR probe head and the rise time of the pulsed gradient is extremely short (a few microseconds).
Abstract: Sets of coils providing linear gradients of any desired direction are described. The coils are small and placed in the NMR probe head. Power consumption is low and the rise time of the pulsed gradient is extremely short (a few microseconds).
TL;DR: In this paper, a modified stylus instrument scans the workpiece in a number of parallel profiles, recorded on-line by a digital computer, which also controls operation of the instrument.
Abstract: The design, construction and use of an automated system for mapping, measuring and analysing small areas of surfaces are described. A modified stylus instrument scans the workpiece in a number of parallel profiles, recorded on-line by a digital computer, which also controls operation of the instrument. The system can scan an area of up to 8 mm*8 mm in 2 h and record it as nearly half a million height readings. Examples of isometric and contour plots of recorded data are presented.
TL;DR: In this article, a new process is outlined for the production of bleached silver image holograms, which leaves phase holograms with the low noise and scatter previously only associated with amplitude holograms.
Abstract: A new process is outlined for the production of bleached silver image holograms. This paper discusses a process that leaves phase holograms with the low noise and scatter previously only associated with amplitude holograms. Much larger image volume can now be recorded with high efficiency and contrast due to the improved image quality and reduced noise. The basic improvements are due to developments in concentrated Neofin and the use of a carefully constituted mild bleach agent.
TL;DR: In this article, a method is proposed for calculation of simultaneous hyperfine magnetic fields and electric field gradient distributions in amorphous materials, where the lack of long-range order as well as a relatively poor shortrange order lead to a change in hyperfine interactions from nucleus to nucleus and the Mossbauer spectra have to be analysed in terms of a continuous distribution of characteristic parameters.
Abstract: In amorphous materials, the lack of long-range order as well as a relatively poor short-range order lead to a change in hyperfine interactions from nucleus to nucleus and the Mossbauer spectra have to be analysed in terms of a continuous distribution of characteristic parameters. A method is being proposed for calculation of simultaneous hyperfine magnetic fields and electric field gradient distributions.
TL;DR: SQUIDs are a class of very sensitive superconducting measuring devices, whose operation is based on flux quantization and the Josephson effects as mentioned in this paper, and applications of these devices in a wide variety of fields including precise electrical measurement, thermometry, magnetic properties, relativity physics, geophysical measurement and biomagnetism are dealt with.
Abstract: SQUIDs are a class of very sensitive superconducting measuring devices, whose operation is based on flux quantization and the Josephson effects. After a brief summary of these effects the principles of operation of single and double Josephson junction SQUIDs are dealt with in some detail, including noise processes and estimates of the ultimate sensitivity attainable. Applications of these devices in a wide variety of fields including precise electrical measurement, thermometry, magnetic properties, relativity physics, geophysical measurement and biomagnetism are dealt with.
TL;DR: In this paper, a simple differential AC technique for continuously measuring small voltage changes in electron transport measurements is described, which is a technique that can be used to measure electron transport changes in real time.
Abstract: A simple differential AC technique for continuously measuring small voltage changes in electron transport measurements is described.
TL;DR: This work extends the application of oil film interferometry to the measurement of skin friction in air flow and suggests that the methods can give a wealth of information concerning surface flows which would otherwise be difficult, if not impossible, to achieve.
Abstract: The application of oil film interferometry to the measurement of skin friction in air flow was described in an earlier paper by Tanner and Blows (see ibid., vol.9, no.4, p.194 (1976)). This work is extended in various ways. These include use of oil droplets as an alternative or in addition to continuous films, particularly for exploration of three-dimensional flows. The use of accidentally or deliberately introduced disturbances as streamline markers is described. The use of the characteristics method to follow transient changes of oil film profile is demonstrated. Many checks on the consistency of the methods and comparisons with theory are given. The results suggest that the methods can give a wealth of information concerning surface flows which would otherwise be difficult, if not impossible, to achieve.
TL;DR: In this article, the authors present a theoretical treatment of the pulsing properties of a multicavity device, which follows the progress of individual electron packets throughout the system, in contrast to conventional chopping and bunching theory.
Abstract: The chopper was designed for dynamic electron optical experiments where it is necessary to provide pulses of high quality with respect to both width and energy spread. The chopping action relies on the optical properties of a microwave cavity; these are exploited such that the time dependent space focusing causes a small circular aperture on the axis of rotational symmetry to transmit strongly for a single band of phase angles in each cycle of the excitation. The theoretical treatment is oriented towards computer display, and is novel in that it follows the progress of individual electron packets throughout the system. In contrast to conventional chopping and bunching theory, it is possible to analyse with ease the pulsing properties of a multicavity device.
TL;DR: The composite wall hollow cathode is a new type of source, set up for studies of the emission spectra due to electronic transitions in diatomic molecules as mentioned in this paper, which enables an easy systematic search to be made for spectra which have not yet been observed.
Abstract: The composite wall hollow cathode is a new type of source, set up for studies of the emission spectra due to electronic transitions in diatomic molecules. This lamp is characterised by the wide range of emitted spectra, its stability, its capacity to identify new molecules easily and to emit at low or very low rotational temperature. It enables an easy systematic search to be made for spectra which have not yet been observed. Moreover, the possibility of emission at different temperatures-and in particular at very low temperature-facilitates rotational studies. The best conditions of utilisation are described. The lamp is able to run for several months at an intensity of about 50 mA and, for a given low temperature of the discharge gases, it is approximately one hundred times more intense than a traditional hollow cathode lamp.
TL;DR: In this article, a review of nonlinear devices that have been used or are potentially useful for laser frequency measurement in the optical region, extending from the submillimetre to the ultraviolet.
Abstract: Reviews nonlinear devices that have been used or are potentially useful for laser frequency measurement in the optical region, extending from the submillimetre to the ultraviolet. The devices are grouped mainly in two classes: point-contact junctions and bulk nonlinear crystals or gases. Their physical principles and limitations are discussed, and attainments when constructed of various materials are listed. Ways of measuring frequencies with them are considered.
TL;DR: In this article, the brightness of the lanthanum hexaboride, LaB6, cathode electron gun of the Stereoscan S-4 scanning electron microscope has been evaluated.
Abstract: The brightness of the lanthanum hexaboride, LaB6, cathode electron gun of the Stereoscan S-4 scanning electron microscope has been evaluated. This gun is an indirectly heated Broers type of LaB6 gun design, and the several variables which affect its brightness have been evaluated using a cage device for the brightness measurements. The results indicate that when proper operating conditions are employed the LaB6 brightnesses are of the order of 15 to 20 times that of tungsten operated at 40 h life conditions, and that single crystal cathodes are more reliable for producing high brightnesses.
TL;DR: In this paper, the use of cascaded channel plates as position dependent particle counters is described and a one-and two-dimensional dissection technique based on the spread of charge between channel plate and collector is used.
Abstract: The use of cascaded channel plates as position dependent particle counters is described. A one- and two-dimensional dissection technique, based on the spread of charge between channel plate and collector, is used. The one-dimensional detector is developed for use in atomic scattering experiments. The system is tested by measuring the relative, total differential scattering cross section of electrons by helium between 1 degrees and 3.4 degrees .
TL;DR: In this article, a hydration stage is designed for the Siemens Elmiskop 1A with a minimal modification to the microscope, which is suitable for temperature and hydration dependent experiments on both biological and non-biological materials.
Abstract: A hydration stage is designed for the Siemens Elmiskop 1A with a minimal modification to the microscope. The stage is temperature controlled in the range of -10 degrees C to 50 degrees C, saturated hydration condition being automatically obtained at all temperatures. The stage is easy to operate. It is suitable for temperature and hydration dependent experiments on both biological and non-biological materials and for dynamically observing other mixed phase physical or chemical interactions.
TL;DR: Diffraction gratings in which the grooves are formed by recording optical interference fringes are rapidly becoming established as alternatives to ruled gratings as discussed by the authors, but because of both the limitations and the novel features of the interference method of manufacture, a straightforward comparison is not always possible.
Abstract: Diffraction gratings in which the grooves are formed by recording optical interference fringes are rapidly becoming established as alternatives to ruled gratings. In many respects they compare favourably with ruled gratings, but because of both the limitations and the novel features of the interference method of manufacture, a straightforward comparison is not always possible. Whether a ruled or interference grating is to be preferred will strongly depend upon the use to which it is to be put.
TL;DR: In this article, a technique is described for giving accurate measurements of cyclotron resonance and Faraday rotation in very high pulsed magnetic fields up to 130 T (13 MG).
Abstract: A technique is described for giving accurate measurements of cyclotron resonance and Faraday rotation in very high pulsed magnetic fields up to 130 T (13 MG) The megagauss fields were generated by the compression of magnetic flux with electromagnetic force in the theta -pinch configuration (Cnare (1966) effect) A tunable CO2 laser was used for the infrared light source, and fast detection of the light was carried out with a high speed infrared detector A simple method was developed for determining accurately the relative field sensitivity of pickup probes Based on the calibration of the absolute field sensitivity of the probes by the Faraday rotation of CdS at 6328 nm, the accuracy of the field intensity measurements reached +or-3% The cyclotron resonance for electrons in Ge, GaAs and InSb was measured at room temperature
TL;DR: In this article, a display system is described which allows NMR images to be viewed on a monitor oscilloscope, where density variations in the image are displayed as intensity variations with good linearity using a technique of Z axis time modulation.
Abstract: A display system is described which allows NMR images to be viewed on a monitor oscilloscope. Density variations in the image are displayed as intensity variations with good linearity using a new technique of Z axis time modulation.
TL;DR: In this paper, the optimum conditions for the growth of cobalt dendrites upon tungsten wire for use as field desorption and especially field ionization emitters are described.
Abstract: Optimum conditions for the growth of cobalt dendrites upon tungsten wire for use as field desorption and especially field ionization emitters are described. The new emitters and superior to nickel emitters for field ionization and are most simple to manufacture than carbon emitters; their growth may also be localized at will along the wire.