Showing papers in "Review of Scientific Instruments in 1973"
TL;DR: In this article, an optical system for rapid routine pressure measurement is described which utilizes a pressure shift in the sharp R-line fluorescence spectrum of ruby or similar materials, which can be employed with suitable modification in any pressure system which has optical access.
Abstract: An optical system for rapid routine pressure measurement is described which utilizes a pressure shift in the sharp R‐line fluorescence spectrum of ruby or similar materials. The system, which consists of a standard polarizing microscope and a 1/4 m monochromator with associated photodetection system, is used with the diamond‐anvil pressure cell, but can be employed with suitable modification in any pressure system which has optical access. The precision of the pressure measurement in a hydrostatic environment up to 100 kilobar is 0.5 kilobar using ruby as the pressure sensor. This precision is better than the accuracy of the present pressure scale above 40 kilobar. The merits of fluorescent materials other than ruby as pressure sensors are also discussed. A description of a Waspaloy diamond cell with some modifications in design is given. This improved cell and associated techniques extends the pressure range in gasketed systems up to 200 kilobar at room temperature and to moderate pressures at 700° C.
873 citations
TL;DR: In this paper, over 1200 Alnico magnets are used to contain a conventional discharge plasma produced by 1-20 A of emission from 6-48 small filaments at − 60 V.
Abstract: Over 1200 Alnico magnets (1.3 × 1.3 × 4 cm) are used to contain a conventional discharge plasma produced by 1–20 A of emission from 6–48 small filaments at − 60 V. Densities up to 1012 ions/cm3 are produced in argon at 2 × 10−3 Torr. At 5 × 10−6 Torr typical parameters are: 8 × 1010 ions/cm3; ni / n0 ≈ 0.7; Te ≈ 5 eV; Ti ≈ 0.5 eV; noise 〈 δn/n 〉 ≈ 2 × 10−4; and < 1% nonuniformity over a volume 31 cm diam by 69 cm. Uniform dense plasmas of He, D, and H are also produced. The ion containment appears to be both magnetic and electrostatic.
468 citations
TL;DR: A new flow‐system instrument for quantitative analysis and sorting of microscopic particles, particularly biological cells, based on multiple measurements of physical and biochemical properties has been developed.
Abstract: A new flow‐system instrument for quantitative analysis and sorting of microscopic particles, particularly biological cells, based on multiple measurements of physical and biochemical properties has been developed. Cells stained with fluorescent dyes in liquid suspension enter a unique flow chamber where electrical and optical sensors measure cell volume, single‐ or two‐color fluorescence, and light scatter, and emerge in a liquid jet that is broken into uniform droplets. Sensor signals are electronically processed several ways for optimum cell discrimination and are displayed as pulse‐amplitude distributions using a pulse‐height analyzer. Processed signals trigger cell sorting according to preselected parametric criteria. Sorting is accomplished by electrically charging droplets containing the cells and electrostatically deflecting them into collection vessels. This instrument is described in detail with illustrative examples of experiments using polystyrene fluorescent microspheres, cultured human cells,...
245 citations
TL;DR: A resonator and a pulse method for relative ultrasonic absorption measurements in liquids from about 0.5 to 100 MHz are described and discussed, which are suitable for relaxational studies on fast biochemical reactions.
Abstract: A resonator and a pulse method for relative ultrasonic absorption measurements in liquids from about 0.5 to 100 MHz are described and discussed. Due to the small sample volumes needed (around 1 ml) both techniques are suitable for relaxational studies on fast biochemical reactions. Cells are described, which have been operated with aqueous and organic media in a temperature range from − 10 to 80 °C.
194 citations
TL;DR: In this paper, simple analytic formulas that can be used to design a finite width uniform field electrode for any desired aspect ratio and field uniformity are derived, and the resulting profile is superior to those of Rogowski, Bruce, and Harrison in its smoothness, compactness, and uniformity.
Abstract: Simple analytic formulas that can be used to design a finite width uniform‐field electrode for any desired aspect ratio and field uniformity are derived The resulting profile is superior to those of Rogowski, Bruce, and Harrison in its smoothness, compactness, and field uniformity A procedure for designing a three‐dimensional profile is also given
166 citations
TL;DR: In this article, the beam divergence and perveance of a single aperture three electrode extraction system using helium ions at energies between 10 and 30 keV were investigated. But the most critical parameter was the ratio of the radius of the first aperture to the distance between the first and second electrodes, the highest current density being obtained at values of this ratio less than 0.5.
Abstract: Experimental results are given for the perveance and beam divergence of a single aperture three electrode extraction system using helium ions at energies between 10 and 30 keV. The aperture radii, the electrode thicknesses, and the spacings were varied and from the results a preferred design was obtained for use in a multiaperture array. The most critical parameter was the ratio (S) of the radius of the first aperture to the distance between the first and second electrodes, the highest current density being obtained at values of this ratio less than 0.5. The optimum beam divergence observed corresponded to a Gaussian beam profile with a width (ω) of ± 1.2° at 2 m from the source. The measured perveance at small values of S and at minimum ω lay between 75% and 90% of the value predicted on the basis of a simple model using the Langmuir‐Blodgett formula for the spherical diode.
166 citations
TL;DR: In this article, a light scattering instrument is described for measuring, as a function of scattering angle, the elements of the matrix describing light scattered from small particle systems using a piezo-optical birefringence modulator to modulate the polarization state of the incident light beam.
Abstract: A new light scattering instrument is described for measuring, as a function of scattering angle, the elements of the matrix describing light scattered from small particle systems. The instrument uses a piezo‐optical birefringence modulator to modulate the polarization state of the incident light beam, and uses lock‐in amplifier detection of the scattered light. The first and second harmonics of the modulation frequency are used with various combinations of filters and orientations to give the separate matrix elements. A treatment of a simple scattering experiment by means of Mueller calculus is carried through to illustrate the interactions of the light with the scattering system and with the various components of the measuring instrument. Evaluation of the instrumental performance is shown through measurements on two systems of monodisperse polystyrene spheres of average radius 550 and 3940 A, compared with Mie calculations. Further measurements on sulfur colloids are presented, and suggestions of the va...
157 citations
TL;DR: In this paper, a photomultiplier voltage distribution circuit is described, which permits one to optimize the performance of the photon counting photomULTiplier either for sensitivity, time resolution or both in order to assure the validity of the convolution integral as the representation of the instrument output.
Abstract: Refinements of the single photon technique are reported, which are concerned for the most part with the photon timing photomultiplier, its associated circuitry, and the signal processing equipment between this multiplier and the time to amplitude convertor. A photomultiplier voltage distribution circuit is described which permits one to optimize the performance of the photon counting photomultiplier either for sensitivity, time resolution, or both in order to assure the validity of the convolution integral as the representation of the instrument output. An investigation of the variation of the instrumental response with stop discriminator level is reported, and the origin and elimination of wavelength effects and photocathode area effects associated with the timing photomultiplier are also described.
143 citations
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TL;DR: In this article, a novel atom probe is described which can determine the mass-to-charge ratios of all ion species produced during a single desorption event or of individual species at several preselected crystallographic locations during each DES event.
Abstract: A novel atom probe is described which can determine the mass‐to‐charge ratios of all ion species produced during a single desorption event or of individual species at several preselected crystallographic locations during each desorption event. This is accomplished without tip movement in an instrument no larger than a conventional field ion microscope by using a new channel plate photomultiplier detector. Alignment, aiming, and pulse stability problems common to all previous designs have been eliminated. Although the present mass resolution is 4 amu at m/n = 184/3, single isotope resolution, if desired, seems possible.
134 citations
TL;DR: In this article, a quadrupole mass filter with a radio frequency of 650 kc was used to detect large clusters in supersonic water jets, where water cluster ions in the form of H(H2O)n+, where n = 1 to 180 corresponding to mass 19 to 3241 amu, were observed.
Abstract: A quadrupole mass filter with a radio frequency of 650 kc was used to detect large clusters in supersonic water jets. Numerous water cluster ions in the form of H(H2O)n+, where n = 1 to 180 corresponding to mass 19 to 3241 amu, are observed.
124 citations
TL;DR: In this paper, liquid helium cooled InSb hot electron bolometers are used in a balanced mixer configuration as detectors for an imageless microwave receiver at the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, for the study of rotational line spectra of interstellar gas molecules.
Abstract: Liquid helium cooled InSb hot electron bolometers are used in a balanced mixer configuration as detectors for an imageless microwave receiver. The system is designed for mounting at the prime focus of the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, and is suitable for the study of rotational line spectra of interstellar gas molecules. Currently the operating frequency is in the 90–140 GHz band where the double sideband system noise temperature is 250 K.
TL;DR: In this paper, a guarded approach to the van der Pauw method was used for the measurement of the electrical transport properties of semiconductors with resistance values over 1012 Ω.
Abstract: Apparatus is described that permits measurement of the electrical transport properties of semiconductors with resistance values over 1012 Ω. The system utilizes a guarded approach to the van der Pauw method which simplifies sample geometry and contacting and permits evaluation of thin layers. The equipment is easy to operate, reliable, and constructed of readily available commercially purchased components.
TL;DR: In this article, a high sensitivity, near-infrared circular dichroism (CD) instrument is measured by the standard modulation method; phase modulation is provided by an Infrasil quartz photoelastic modulator.
Abstract: We report a high sensitivity, near‐infrared circular dichroism (CD) instrument CD is measured by the standard modulation method; phase modulation is provided by an Infrasil quartz photoelastic modulator The spectral range 08–30 μ is spanned Incorporation of a superconducting magnet allows magnetic circular dichroism (MCD) measurements to be made The natural CD of nickel and samarium tartrate complexes and the MCD of a single crystal of Co/MgO at 12 K and 406 kG are reported Performance of the instrument is comparable to visible‐ultraviolet CD instruments
TL;DR: In this paper, a modification of a scanning x-ray topographic camera is described which automatically plots the lattice curvature of single crystal substrates strained by thin films or surface treatments such as diffusion and ion implantation.
Abstract: A modification of a scanning x‐ray topographic camera is described which automatically plots the lattice curvature of single crystal substrates strained by thin films or surface treatments such as diffusion and ion implantation. Film and substrate stresses are calculated from the radius of curvature. The unit operates as an electromechanical feedback system which maintains the orientation of a wafer such that the diffracted x‐ray intensity remains within preset limits while a finely collimated x‐ray beam traverses the wafer. An x‐y recorder continuously plots the changes in orientation as a function of position yielding a trace whose slope is proportional to the radius of curvature of the substrate lattice. The sensitivity of the apparatus is such that radii of curvature of 2000 m can be measured. In addition, the lateral spatial resolution is such that the local substrate lattice curvature can be determined under alternating and overlapping 2.5 mm wide stripes of metal and oxide films. It is also shown t...
TL;DR: In this paper, the configuration and operation of a field spectroradiometer (Exotech model 20B) that measures the intensity of incident and reflected radiation from 0.37 to 2.52 μ and emitted radiation from 2.76 to 13.88 μ are described.
Abstract: The configurations and operation of a field spectroradiometer (Exotech model 20‐B spectroradiometer) that measures the intensity of incident and reflected radiation from 0.37 to 2.52 μ and emitted radiation from 2.76 to 13.88 μ are described. The instrument was built by Exotech Inc. from specifications and plans developed by the USDA. Exotech contributed many engineering concepts based upon knowledge of the theory involved. The instrument consists of two systems, each made up of an optical unit and a control unit. One system covers the spectral range 0.37–2.52 μ; the other system covers the spectral range 2.76–13.88 μ. The optical units of the two systems mount side‐by‐side on a tiltable base mounted on an aerial lift truck. Separation between the objective lenses is about 30 cm to minimize parallax. The systems may be operated separately or in the tandem, boresighted mode. The control units are mounted in a camper‐type equipment van and are connected to the optical units by 60 m of armored cable. Preamplifiers and auxiliary electronics in the optical units are designed to operate without picking up interferences over this length of cable. The entire system is designed to operate in an outdoor environment. Provision has also been made for photographic annotation of field data setups.
TL;DR: The complete electronic system of a frequency sweep 240 MHz NMR spectrometer working with a superconducting magnet is described in this article, where full circuit and construction details are given for the rf sideband generator, pretuned coaxial cavity, aperiodic synchronous detector, digital frequency synthesizer as well as a phase coherent, variable frequency, time sharing pulse generator.
Abstract: The complete electronic system of a frequency‐sweep 240 MHz NMR spectrometer working with a superconducting magnet is described. Full circuit and construction details are given for the rf sideband generator, pretuned coaxial cavity, af aperiodic synchronous detector, digital frequency synthesizer as well as a phase‐coherent, variable‐frequency, time‐sharing pulse generator. This system, with multichannel irradiation possibilities uses extensively standard integrated logic circuits and can be inexpensively built by any laboratory engaged in NMR research.
TL;DR: In this paper, an experimental electrostatic chuck and its high voltage square wave power supply have been fabricated and full clamping action has been provided by electrostatic pressures of 1/6 atm, and 1 atm pressures are feasible.
Abstract: Vacuum wafer chucks are useless for electron beam microfabrication. An analysis of the required electrostatic forces and frequency response of a specimen wafer on a field plate is made. An experimental electrostatic chuck and its high voltage square wave power supply have been fabricated. Full clamping action has been provided by electrostatic pressures of 1/6 atm, and 1 atm pressures are feasible. In‐vacuum operation is excellent down to supply frequencies of 0.01Hz.
TL;DR: A review of direct extraction sources of negative hydrogen ions can be found in this article, where four types of direct ion sources are described: hollow discharge duoplasmatrons, hollow discharge de-duplasmatron, penning sources, and magnetron sources.
Abstract: The article represents a review of direct extraction sources of negative hydrogen ions. During the past year or so interest in this method of producing high intensity beams of negative ions has increased considerably because of new developments resulting in currents of more than 20 mA. The first part of the article deals with inelastic collisions between particles which lead to the creation or destruction of negative ions. The knowledge of such elementary processes is relevant because the intensity of extracted H− currents is determined primarily by the equilibrium between the competing processes of creation and destruction. Attempts by several authors to analyze theoretically the production of H− ions in the plasma of a discharge will be explained subsequently and their results compared with experiments. Four types of direct extraction sources will be described next: duoplasmatrons, hollow discharge duoplasmatrons, Penning sources, and magnetron sources. Details of their design and beam characteristics will be given, as well as suggestions for further improvements.
TL;DR: In this article, a detailed analysis of the transmission properties of low-energy spherical electrostatic electron spectrometers employing preacceleration or preretardation is presented, which shows that the transmission efficiency of such instruments is not necessarily related inversely to electron energy nor directly to analyzer pass energy.
Abstract: A detailed analysis of the transmission properties of low‐energy spherical electrostatic electron spectrometers employing preacceleration or preretardation is presented, which shows that the transmission efficiency of such instruments is not necessarily related inversely to electron energy nor directly to analyzer pass energy. A prescription, which enables observed spectra to be corrected over a wide energy range for intensity variations resulting from instrumental effects, is provided, and a detectable shift (≤ 0.1 eV) in the apparent position of electron lines under certain conditions is predicted. The theory is applied to the design and performance of two spherical photoelectron spectrometers employing ultraviolet and soft x‐ray sources. The analysis may readily be extended to other forms of electrostatic spectrometers employing preacceleration or preretardation.
TL;DR: In this paper, the authors describe a method of accurately measuring the secondary electron yield of solids over the entire incident energy range of 0-1000 eV in less than 30 msec using a commercial LEED/Auger system.
Abstract: We describe a method of accurately measuring the secondary electron yield of solids over the entire incident energy range of 0–1000 eV in less than 30 msec using a commercial LEED/Auger system. Particular attention is paid to the region of low‐energy incident electrons (Ep=0 to 100 eV), and the spatial and energy resolution there are considered. The method is fast enough to see temporal changes in yield on the scale of hundreds of milliseconds. Criteria for measuring the yield of semi‐insulators are considered, as well as measurements of fine structure in the yield near Ep=0 eV.
TL;DR: In this paper, an analysis of the Kelvin method employing a variable shield potential, which takes nonuniformity of the surfaces into account, is given, and the influence of stray capacitance can be determined and eliminated by measuring as a function of spacing between the Kelvin electrodes for different values of the shield potential.
Abstract: An analysis is given of the Kelvin method employing a variable shield potential, which takes nonuniformity of the surfaces into account. The influence of stray capacitance can be determined and eliminated by measuring as a function of spacing between the Kelvin electrodes for different values of the shield potential. These extended Kelvin measurements make it also possible to detect nonuniformity of the sample electrode and to eliminate its influence in certain cases, as is demonstrated by measurements on a vacuum cleaved TiO2 (rutile) (110) surface.
TL;DR: In this article, a new capacitance method is described for the measurement of local, time-varying or steady-state film thickness in two-phase flow studies, suitable for use in simple and complex geometries, and works for either electrically nonconducting or slightly conducting fluids.
Abstract: A new capacitance method is described for the measurement of local, time‐varying or steady‐state film thickness in two‐phase flow studies The method is suitable for use in simple and complex geometries, and works for either electrically nonconducting or slightly conducting fluids Test data were obtained on bubbles of different lengths rising in a circular tube filled with water Results for film thicknesses and bubble residence times showed good self‐consistency and agreement with other available data
TL;DR: An isothermal titration microcalorimeter with a volume of 4 ml and temperature control to ± 2 × 10−5 °C is described in this article, which is suitable for measuring heat where small samples are used such as in the investigation of biological systems.
Abstract: An isothermal titration microcalorimeter having a volume of 4 ml and capable of temperature control to ± 2 × 10−5 °C is described. Major components include a constant temperature water bath controlled to ± 3 × 10−4 °C, a platinum reaction vessel, and an isothermal control circuit consisting of constant Peltier thermoelectric cooling and variable Joule heating controlled by a thermistor in an ac Wheatstone bridge circuit. The calorimeter was tested by measuring the heat of ionization of water and was found to produce data accurate to ±0.1% for this system. The instrument is ideally suited for measuring heats where small samples are used such as in the investigation of many biological systems.
TL;DR: In this paper, the design and construction of high power nitrogen 3371 A laser is described in detail, and the laser produces 13 mJ in a 12 nsec FWHM pulse at a repetition rate of 5 pulses per second.
Abstract: The design and construction of high‐power nitrogen 3371 A laser is described in detail. The laser produces 13 mJ at 3371 A in a 12 nsec FWHM pulse at a repetition rate of 5 pulses per second. Various models of the laser have yielded 108 pulses with very infrequent component failure. When a second mirror is added, strong laser action is observed in the N2 first positive system; the total resultant ir output energy is about 3 mJ in a 50 nsec FWHM pulse.
TL;DR: In this article, a thin-film passive dosimeter system using poly(halo)styrene matrix doped with malachite green methoxide as an indicator has been developed, which has an optical density proportional to dose over the range 104−107 rad and may be calibrated to above 3×107 rad.
Abstract: A useful thin‐film passive dosimeter system has been developed through use of a poly(halo)styrene matrix doped with malachite green methoxide as an indicator. Extensive characterization studies of the chlorostyrene dosimeters have been completed and the range of conditions under which they are useful has been defined. Exposure to radiation causes development of a blue color (absorption at 630 and 430 nm) which has an optical density proportional to dose over the range 104−107 rad and may be calibrated to above 3×107 rad. No effects of dose rate have been observed between 102 and 1015 rad/sec, and no effects of photon energy between 2 keV x‐rays and 1 MeV gamma rays. Of the environmental parameters studied, only extraneous uv light, temperature, and a few noxious gases have a significant effect on the performance of the dosimeters. Oxygen has only a small effect (a few percent) at low dose rates, but acidic gases such as NO2, SO2, and HCl will first color, then bleach the films. The rate and ultimate amount of coloration are dependent on temperature, but this effect is negligible from 0 to 35°C. These films have an indefinite shelf life at room temperature in the absence of light and corrosive gases, and the small effects of oxygen and temperature can be compensated for in the calibration for a particular application.
TL;DR: In this paper, a diode-quad transducer bridge circuit was developed with a high output that is independent of excitation frequency and waveform, and a fractional capacitance resolution of 4.4 × 10−8 at a bandwidth of 10−30 Hz.
Abstract: A new diode‐quad transducer bridge circuit has been developed which features: (1) a high output that is independent of excitation frequency and waveform; (2) a fractional capacitance (ΔC/Co) resolution of 4.4 × 10−8 at a bandwidth of 10–30 Hz; and (3) the capability of conveniently grounding the transducer. Application to a capacitive transducer for pressure measurements yielded an output resolution of 0.003% corresponding to a pressure resolution of ± 1.5 × 10−4 Torr.
TL;DR: The chevron-shaped channel electron multiplier (CEEM) as discussed by the authors is a single-channel multiplier that produces charge pulses averaging more than 107 electrons and these gain magnitudes fall into a quasi-Gaussian distribution with a full width at half-maximum FWHM of approximately 130%.
Abstract: The chevron‐shaped channel electron multiplier is a device which combines the high‐gain pulse‐counting operation of single channel electron multipliers with the imaging capabilities of microchannel arrays. It produces charge pulses averaging more than 107 electrons and these gain magnitudes fall into a quasi‐Gaussian distribution with a full width at half‐maximum FWHM of approximately 130%. Suppression of ion feedback makes possible both imaging and low noise counting applications over large areas. Dark count rates are typically 1 count/sec cm2, and the dynamic range of operation covers 5–6 decades. Active areas over 45 mm diam have been fabricated, with uniform characteristics. Limiting resolution has been measured at 5 line pairs per millimeter. Because of the short length of each channel electron multiplier, the rise time and width of the output charge pulses are extremely short; large signal pulses have been detected with rise times as short as 400 psec.
TL;DR: A method is described for producing thin, hydrophilic support films for electron microscopy that can be made as thin as 10–15 A and used as ultrathin ``windows'' for frozen, aqueous specimens.
Abstract: A method is described for producing thin, hydrophilic support films for electron microscopy. These films have a well defined composition and can be made as thin as 10–15 A. An application is described in which these hydrophilic films are used as ultrathin ``windows'' for frozen, aqueous specimens.
TL;DR: In this article, reflected power profiles were used to determine complex dielectric permittivity of low, medium, and high permittivities of low and high dielectrics by one single method if nonideal plunger properties are taken into account.
Abstract: Computer analysis of reflected power profiles allows accurate determination of complex dielectric permittivity of low, medium, and high permittivity liquids by one single method if nonideal plunger properties are taken into account. For low loss measurements account is taken of the losses in the waveguide walls. For medium and high permittivity liquids, dumbell plunger design leads to important errors due to higher mode excitation and propagation.
TL;DR: In this article, a supersonic molecular beam source was attached to an electron diffraction unit in order to study molecular structures and cluster structures, which was accomplished by means of a very deep (45 mm) beam stop and a mask.
Abstract: A supersonic molecular beam source was attached to an electron diffraction unit in order to study molecular structures and cluster structures. Because the density in a molecular beam is only a few times 1012 molecules per cm3, it was necessary to lower the pressure in the diffraction chamber to 5×10−8 Torr and to eliminate the back‐scattered electrons at large s values. This was accomplished by means of a very deep (45 mm) beam‐stop and a mask. Liquid helium cryopumping makes it possible to reduce the beam source bulkiness which, in turn, permits the placement of the scattering point as close as possible to the source (about 55 mm from the nozzle). Thus a target of the highest density is obtained, while a wide range of scattering is permitted. Reliable diffraction data have been obtained out to s = 45 A−1. The main components of the diffraction unit are described, as is also the supersonic molecular beam source. A discussion is presented on the use of the apparatus.