Showing papers in "Review of Scientific Instruments in 1970"
TL;DR: By producing a train of absorption or dispersion signals (continuous wave magnetic resonance) or free induction decays (pulsed magnetic resonance), it is possible to save time in spin-lattice relaxation measurements as mentioned in this paper.
Abstract: By producing a train of absorption or dispersion signals (continuous‐wave magnetic resonance) or free induction decays (pulsed magnetic resonance) it is possible to save time in spin‐lattice relaxation measurements due to the fact that it is not necessary to wait for equilibrium magnetization before initiating the train. The relaxation time may be calculated from the train according to a simple rapidly converging iteration.
795 citations
TL;DR: In this article, the resistive (Coulter) method of counting and sizing particles in a conducting fluid has been extended to polystyrene spheres 900 A in diameter, with a present detection limit near 600 A, through the use of individual submicron pores etched in irradiated plastic sheet.
Abstract: The resistive (Coulter) method of counting and sizing particles in a conducting fluid has been extended to polystyrene spheres 900 A in diameter, with a present detection limit near 600 A, through the use of individual submicron pores etched in irradiated plastic sheet. The use of a nonionic surfactant and ultrasonic cleaning effectively relieves the problem of plugging. The particles may be driven through the pore by the electric field, without the use of pressure, to yield the vector sum of the electrophoretic and electro‐osmotic velocities. A new theory, yielding an upper limit to the resistive pulse on passage of a sphere, agrees well with data for spheres with diameters d 0.9D. We estimate that a detection limit near 250 A will be attainable with the further development of current techniques.
580 citations
TL;DR: In this paper, an electron monochromator for use in an axial magnetic field is described, where the electrons are injected parallel to the magnetic field and an electric field is applied in a perpendicular direction.
Abstract: An electron monochromator for use in an axial magnetic field is described. Electrons are injected parallel to the magnetic field and an electric field is applied in a perpendicular direction. The electrons thus describe trochoids and drift in a direction perpendicular to both the electric and magnetic fields and disperse according to their initial velocities. An electron energy width at half‐maximum of 0.020 eV can be obtained, with a transmitted current of about 10−9 A.
338 citations
TL;DR: In this paper, a split sphere apparatus has been developed to generate exceedingly high hydrostatic pressures more than 300 kilobars at temperatures over 1500°C in a sample chamber of ample volume.
Abstract: A split sphere apparatus has been developed to generate exceedingly high hydrostatic pressures more than 300 kilobars at temperatures over 1500°C in a sample chamber of ample volume. The calibration of pressures is made by the use of known phase transition points in Bi, Fe, and Pb. The calibration above the Pb point (161 kilobars) is discussed in terms of resistance changes for In and CdS previously reported by Drickamer et al.
317 citations
268 citations
252 citations
TL;DR: Ion cyclotron resonance spectroscopy has been adopted for the detection of gaseous ions formed within an analyzer cell of new design as discussed by the authors, which has been trapped by electron impact for as long as 0.10 sec and detected with a half-height mass resolution of 5000.
Abstract: Ion cyclotron resonance spectroscopy has been adopted for the detection of gaseous ions formed within an analyzer cell of new design. Ions formed by electron impact have been trapped within the analyzer cell for as long as 0.10 sec and detected with a half‐height mass resolution of 5000. Even at pressures of 10−5 Torr ion‐molecule reactions of high kinetic order may be observed. An important feature of the trapped ion analyzer cell is that it retains the capability of the ICR double resonance experiment for elucidating the reaction sequence occurring in a complex mixture of primary ions and high order product ions. A pulsed magnetic field detection scheme accurately limits the residence time of the ions within the trapped ion analyzer cell.
171 citations
TL;DR: A detailed description of a 10.16 cm gas gun that has been designed and installed at Washington State University is presented in this paper, where the maximum velocity achieved to date is 0.9 mm/μsec with an 1100 g projectile.
Abstract: A detailed description of a 10.16 cm gas gun that has been designed and installed at Washington State University is presented. The design velocity is 1.5 mm/μsec; the maximum velocity achieved to date is 0.9 mm/μsec with an 1100 g projectile. Angular misorientation of the projectile with respect to the target surface is consistently below 0.5 mrad. Brief descriptions of ancillary instrumentation and equipment are also given.
168 citations
TL;DR: In this paper, an inexpensive electrical sensor of plane coordinates employs juxtaposed sheets of conducting material having electrical equipotential lines extending across each sheet and arranged normal to each other, which causes separate signals to be applied to one or more conventional information-indicating units.
Abstract: An inexpensive electrical sensor of plane coordinates employs juxtaposed sheets of conducting material having electrical equipotential lines extending across each sheet and arranged normal to each other. A probe upon touching each sheet at a selected intersection of the equipotential lines causes separate signals to be applied to one or more conventional informationindicating units.
152 citations
TL;DR: In this paper, the authors reviewed the electrical excitation of pulsed CO2 laser operating at atmospheric pressure and proposed a double transverse discharge (DTD) based approach for the design of a 3.8 m long laser.
Abstract: The problems encountered in the electrical excitation of pulsed CO2 lasers operating at atmospheric pressure are briefly reviewed, with some solutions developed at the Defence Research Establishment Valcartier, and their limitations. A new approach, based on a double transverse discharge technique, has permitted the design of a 3.8 m long laser which delivered up to 9 J/pulse with a peak power of 12 MW. An output energy density of 5.5 mJ/cm3 of excited gas has been achieved.
146 citations
TL;DR: In this paper, a parallel plate electrostatic analyzer has been proposed, in which particles issuing from a point source on the earthed plate are deflected by the electric field and brought to a focus on that plate, provided the angle of entrance to the field is 45°.
Abstract: A description is given of a new parallel plate electrostatic spectrograph. A parallel plate electrostatic analyzer has been discussed previously, in which particles issuing from a point source on the earthed plate are deflected by the electric field and brought to a focus on that plate, provided the angle of entrance to the field is 45°. This is a simple example of the more general focusing properties of a parallel plate analyzer. From consideration of these properties, it has been found possible to select a given angle of entry into the field for which second order focusing can be attained giving rise to an angular aberration term proportional to (Δθ)3. Uslng an acceptance of ±6° a resolving power of 200 is predicted and has been obtained with a prototype.
TL;DR: In this article, saddle-shaped coils for generating a field perpendicular to the axis of a cylindrical shell to which the coils are confined can be designed in a compact and easily constructed form.
Abstract: Saddle shaped coils for generating a field perpendicular to the axis of a cylindrical shell to which the coils are confined can be designed in a compact and easily constructed form. The central magnetic field of such a system and its second derivatives with respect to displacements from the center are given as functions of the coil dimensions, and conditions for minimizing these derivatives are discussed. A coil pair with a length‐to‐diameter ratio of 2 and circular arcs of 120° will have no second order central field derivatives in any direction.
TL;DR: In this paper, a bakable ultrahigh vacuum system has been constructed to sample the particle flux incident on the substrate of a planar diode sputtering system, where a beam of particles from the discharge is extracted into a long mean free path environment where it passes through a 90° deflection electrostatic analyzer into a quadrupole residual gas analyzer.
Abstract: A bakable ultrahigh vacuum system has been constructed to sample the particle flux incident on the substrate of a planar diode sputtering system. A beam of particles from the discharge is extracted into a long mean free path environment where it passes through a 90° deflection electrostatic analyzer into a quadrupole residual gas analyzer. The mass spectra of positive ions incident on a substrate during dc sputtering of copper and aluminum bronze are shown and the influence of hydrogen contamination is illustrated. The energy distribution of the Ar+ ions is presented for several values of the substrate bias.
TL;DR: A unique stroboscopic pulse radiolysis system is described which detects the transient light‐absorbing species formed in solutions by individual fine structure pulses from a 40 MeV linear accelerator, and meets its expected performance capability.
Abstract: A unique stroboscopic pulse radiolysis system is described which detects the transient light‐absorbing species formed in solutions by individual fine structure pulses from a 40 MeV linear accelerator. A measured time resolution of 23 psec is attained by using, as the analyzing light, the short (<10 psec) Cerenkov light flashes produced in air by the fine structure pulses of the electron beam. This light is suitably delayed by an optical system in which the path length is slowly changed, then passed through the irradiated sample. The integrated light passing through the sample id detected, and variations in the optical absorption at varying times after the irradiation pulse are observed. The design and performance of the optical, mechanical, and electronic devices which retrieve the absorption signal out of the noise are described in some detail. As an integrated unit, this system meets its expected performance capability, being able to successfully detect absorption signals as small as 0.2%.
TL;DR: In this article, a photomultiplier is used to measure the total soft x-ray fluorescence of the anode surface of a vacuum diode and the derivative of multiplier current as a function of anode potential rises abruptly at the appearance potentials of characteristic x rays.
Abstract: A simple, nondispersive spectrometer has been designed which allows the binding energies of core electrons to be determined for atoms at a solid surface The spectrometer consists of a photomultiplier which measures the total soft x‐ray fluorescence of the anode surface of a vacuum diode The derivative of the multiplier current as a function of the anode potential rises abruptly at the appearance potentials of characteristic x rays The derivative is taken by superimposing a small oscillation on the anode potential and synchronously detecting the variation in multiplier current The information obtained is comparable to that usually derived from absorption spectroscopy but is much more sensitive to the surface region Thus, in addition to determining the elemental composition of the surface, chemical shifts in the binding energies of core electrons are readily observed
TL;DR: The parylene polymers are shown to be extremely uniform in thickness, have good gas barrier properties, and are relatively nonabsorbing throughout the entire soft x-ray region.
Abstract: Thin parylene films have been prepared and are available in thicknesses to 0.025 μ. The parylene polymers are shown to be extremely uniform in thickness, have good gas barrier properties, and are relatively nonabsorbing throughout the entire soft x‐ray region. Comparisons are made with commercially available Mylar, polycarbonate, polypropylene, VYNS, and Formvar.
TL;DR: In this paper, a new electron beam injection gun was developed to produce pulsed relativistic electron beams with a power of 1010 W. The annular shaped beam propagates in a magnetic field with efficiencies approaching 100% and its radius may be controlled by the magnetic field configuration.
Abstract: A new electron beam injection gun has been developed to produce pulsed relativistic electron beams with a power of 1010 W. The annular shaped beam propagates in a magnetic field with efficiencies approaching 100% and its radius may be controlled by the magnetic field configuration.
TL;DR: In this paper, a general treatment of the electron optical properties of cylindrical electron spectrographs is given and the resolution, the transmission, and the ratio of them (figure of merit) is computed and compared for various choices of focusing arrangement and location of the source and the image.
Abstract: The article gives a general treatment of the electron optical properties of cylindrical electron spectrographs. The resolution, the transmission, and the ratio of them (figure of merit) for electrostatic spectrographs are computed and compared for various choices of focusing arrangement and location of the source and the image. The second order focusing, which occurs in the evaluation as an asymptotic case of the first order focusing arrangement, is shown to yield a figure of merit which is in most cases superior to first order focusing. Locating the source and the image at the cylinder axis is also found to be the optimal setup using this figure of merit as a criterion.
TL;DR: In this paper, a new circuit for measuring photoemission energy distribution curves (EDC's) by the ac retarding potential method is described which offers greatly improved noise performance over earlier circuits.
Abstract: A new circuit for measuring photoemission energy distribution curves (EDC's) by the ac retarding potential method is described which offers greatly improved noise performance over earlier circuits. General techniques for EDC noise reduction are outlined and the noise performance expected from different electrometer detectors is compared. A method for quantitatively evaluating the noise performance of an EDC measurement system from an experimental EDC is presented and applied to EDC's obtained with this new measurement system. Equivalent noise currents in energy distribution curves obtained with this system are found to be as low as 2 to 3×10−15 A rms. This low noise allows the measurement of EDC's with total dc photocurrents of less than 10−13 A.
TL;DR: In this paper, a tunnel diode oscillator is described which has been successfully used for paramagnetic susceptibility measurements at frequencies from 3 to 55 MHz, at temperatures from 1.2 to 77 K, and at magnetic fields up to 18 kG.
Abstract: A tunnel diode oscillator is described which has been successfully used for paramagnetic susceptibility measurements at frequencies from 3 to 55 MHz, at temperatures from 1.2 to 77 K, and at magnetic fields up to 18 kG. In appropriate cases, such measurements may be used to infer magnetic specific heats and spin‐lattice relaxation times.
TL;DR: In this paper, the construction and performance of mechanical transducers suitable for generating and detecting second sound in pure 4He, and also in dilute 3He-4He mixtures at millidegree temperatures, are described.
Abstract: The construction and performance of mechanical transducers suitable for generating and detecting second sound in pure 4He, and also in dilute 3He–4He mixtures at millidegree temperatures, are described. It is shown that when the normal fluid density is small, the behavior of the transducers can be explained by a simple acoustical model which enables their sensitivity, frequency response, and reflection coefficient to be calculated in terms of easily measured parameters.
TL;DR: In this article, it was shown that there exists an optimum focal line in which the angular aberrations are reduced to one quarter of their values on the normal focal line, as is the case in optical systems.
Abstract: Previous analysis of the focusing properties of a parallel plate electrostatic spectrograph has shown that second order focusing can be achieved In the present paper it is demonstrated that as a corollary, there exists an optimum focal line in which the angular aberrations are reduced to one quarter of their values on the normal focal line, as is the case in optical systems Results of computations of the line shapes are also presented
TL;DR: In this paper, the soft particle spectrometer uses electrostatic deflection for simultaneous measurement of the differential energy spectra of electrons and protons, and the energy range is from 10 eV to 10 keV per unit charge with ±40% energy spread.
Abstract: The soft particle spectrometer uses electrostatic deflection for simultaneous measurement of the differential energy spectra of electrons and protons. The energy range is from 10 eV to 10 keV per unit charge with ±40% energy spread. Twelve stage BeCu electron multipliers are used as detectors in the counting mode over a five decade dynamic range. A swept mode of energy selection provides a spectrum in 0.5 sec for high fluxes, while a stepped mode suitable for lower fluxes takes 40 sec. A typical electron spectrogram for a transpolar pass is included as an example of the data reduction procedure used.
TL;DR: In this article, the application of phase sensitive detection techniques to the ac Kelvin method is discussed, and the equations are solved, and conditions are given for the balance point to be independent of plate spacing.
Abstract: Measurements of the influence of stress upon contact potential necessitate the observation of shifts in contact potential of the order of 100 μV or less. The ac Kelvin technique was selected to yield this sensitivity. The application of phase sensitive detection techniques to the ac Kelvin method is discussed, and the equations are solved. The success of the method depends upon the use of a guarded field effect transistor input stage located within the Kelvin probe. The effect of nonuniform contact potentials and nonuniform capacitor plate separation is analyzed, and conditions are given for the balance point to be independent of plate spacing. The stress dependent contact potential measurements may be continuously displayed using a new nonlinear second harmonic detection scheme. This method is discussed.
TL;DR: In this paper, a unique low energy (0-50 keV) electron accelerator has been developed which provides a broad, parallel, low intensity electron beam with excellent long term stability.
Abstract: A unique low energy (0–50 keV) electron accelerator has been developed which provides a broad, parallel, low intensity electron beam with excellent long term stability. The beam intensity is approximately 106 electrons·cm−2 ·sec−1 and the long term stability is better than 2%/day. A prototype of this accelerator is described and the results of its application to instrument calibration and channel electron multiplier (CEM) efficiency measurements are presented. The absolute electron detection efficiency for CEM's was found to vary from approximately 90% at 1 keV to 73% at 14 keV with a probable error of ±10%. The large disagreement among the various published measurements of CEM detection efficiency is discussed.
TL;DR: In this article, an instrument system for optical pyrometry with a precision of 2 K or less in 1 msec was presented. But the accuracy was limited to a few kelvins.
Abstract: Incandescent solids at temperatures above 1500 K radiate sufficient energy to allow optical pyrometry with a precision of 2 K or less in 1 msec. An instrument system has been built which achieves accuracy of a few kelvins. The sensitivity is 0.4 K when making 1200 measurements/sec near 2000 K or it can be increased as required to 0.01 K with a measurement rate of 1/sec. The system permits dynamic measurement of high temperature thermal properties of refractory metals with better accuracy than has been obtained by methods using slow heating.
TL;DR: In this paper, a criterion for comparing electrostatic analyzers is proposed and is shown to be preferable to another criterion proposed recently, which was used in β-spectrometer analysis.
Abstract: In view of the recent development of several new electrostatic analyzers, the need arises for a criterion for comparing their figures of merit. A criterion usually used in β spectrometry is proposed and is shown to be preferable to another criterion proposed recently.
TL;DR: In this article, an instrument for the measurement of circular dichroism in the vacuum ultraviolet was described, where a magnesium fluoride Rochon prism serves as polarizer and a stress plate modulator is the ¼-wave retardation element.
Abstract: An instrument is described for the measurement of circular dichroism in the vacuum ultraviolet. A magnesium fluoride Rochon prism serves as polarizer and a stress plate modulator is the ¼‐wave retardation element. CD spectra have been recorded to 165 nm, but substitution of two elements in the optical system by available parts is expected to allow further extension of the wavelength region accessible. A previously used less successful system is also described which used a rotating Rochon prism and a Fresnel rhomb.