Showing papers in "Review of Scientific Instruments in 1975"
TL;DR: A diamond-anvil type optical cell of improved design has produced static pressures in gasketed samples up to 500 kilobar as measured by the ruby fluorescence technique as discussed by the authors.
Abstract: A diamond‐anvil type optical cell of improved design has produced static pressures in gasketed samples up to 500 kilobar as measured by the ruby fluorescence technique. The ruby R1 line pressure shift is linear to 291 kilobar, and the maximum measured shift is extrapolated to 500 kilobar assuming continued linearity of the pressure dependence. The ultimate pressure capability of this diamond cell has not been established. Transition pressures in the semiconductors Si, ZnSe, ZnS, and GaP measured by the ruby method indicate that the revised 1970 fixed point scale and the ruby (NaCl) scale diverge above 135 kilobar and disagreement may be by as much as a factor of 2 in the 500 kilobar range with the ruby scale defining the lower pressure.
486 citations
TL;DR: In this paper, a flow system for the production of diatomic metal oxides and halides is described, where molecules are formed by reacting metal vapor in a flowing, inert gas with a suitable oxidizer.
Abstract: A flow system for production of diatomic metal oxides and halides is described. Molecules are produced by reacting metal vapor in a flowing, inert gas with a suitable oxidizer. Product molecules are frequently formed in electronically excited states, making this system particularly useful for optical emission spectroscopic studies. Specific advantages are: (a) large number of reactant products; (b) little thermal excitation in the reaction region; (c) spectra uncluttered by emission from undesirable species; and (d) in many cases, formation of molecules in electronically excited states not produced or detected in other sources. Also discussed is a variation of the design which is used to produce small metallic particles. These particles are formed by homogeneous nucleation of the metal vapor and range in size from 5 to 500 nm.
190 citations
TL;DR: In this article, an apparatus for making transport measurements, especially thermopower, on single crystals of highly conducting organic solids is described, designed specifically for small fragile anisotropic samples such as TCNQ salts.
Abstract: An apparatus is described for making transport measurements, especially thermopower, on single crystals of highly conducting organic solids. It is designed specifically for small fragile anisotropic samples such as TCNQ salts. The temperature range is 400−1.2 k. A slow ac technique is used so that stray thermal emfs are eliminated and measurements can be taken with a small (0.5 K) temperature gradient for good temperature resolution in regions where the transport properties are changing quickly.
185 citations
TL;DR: A monolayer trough with two movable barriers and several compartments is described in this article, where a precision multilayer depositing lift, a simplified Langmuir trough, and a technique for isolating monolayers remaining in contact with water are discussed.
Abstract: A monolayer trough with two movable barriers and several compartments is described. In addition, a precision multilayer depositing lift, a simplified Langmuir trough, and a technique for isolating monolayers remaining in contact with water are discussed. Various applications of this combined instrumentation in the study of monomolecular films are presented.
184 citations
TL;DR: In this article, the results of a systematic study of the design considerations of a low-temperature tunnel diode oscillator are presented, which satisfactorily describes the measured frequency noise and dependence on bias voltage, magnetic field, and temperature.
Abstract: The results of a systematic study of the design considerations of a low‐temperature tunnel diode oscillator are presented. The calculated circuit performance satisfactorily describes the measured frequency noise and dependence on bias voltage, magnetic field, and temperature. The overall performance allows measurement of changes in the resonant frequency of an LC circuit with a precision of 0.001 ppm. One can thereby detect extremely small changes in a number of material properties such as thermal expansion, surface impedance, and electric and magnetic susceptibilities.
166 citations
TL;DR: In this paper, a system for producing 300μsec bursts of 1017 metal atoms with 3eV average energy is described, which can be successfully used to introduce impurities into CTR-oriented tokamaks for transport and confinement studies.
Abstract: A system for producing 300‐μsec bursts of 1017 metal atoms with 3‐eV average energy is described. It is shown that this system can be successfully used to introduce impurities into CTR‐oriented tokamaks for transport and confinement studies.
157 citations
TL;DR: In this paper, a miniaturized Kautsky apparatus was developed for measuring chlorophyll fluorescence induction in photosynthetic plants in situ, based on a new sensor-emitter combination of a phototransistor on the back of a light emitting diode.
Abstract: A miniaturized Kautsky apparatus was developed for measuring chlorophyll fluorescence induction in photosynthetic plants in situ. The instrument is based on a new sensor–emitter combination of a phototransistor on the back of a light emitting diode (piggy‐back arrangement). Fluorescence curves can be recorded with a time resolution of 250 μsec, illumination time is infinitely variable from 0.1 to 100 sec, and light intensity variable from 0 to 104 erg⋅cm−2sec−1. In combination with portable recorder the new instrument provides a rapid and reliable means of measuring photosynthetic activity of plants in natural environments. The piggy‐back sensor–emitter combination is suggested to be of general importance as a new opto‐electronic device for detecting fluorescence and reflected light. Examples of operation are given which demonstrate time resolution, sensitivity, and specificity of the new instrument.
101 citations
TL;DR: The pulsed EPR spectrometer of Huisjen and Hyde as discussed by the authors is suitable for determination of spinlattice relaxation times as short as 10−7 sec, and is designed particularly for measurements on dilute solutions of free radicals and of spin-labeled biomolecules.
Abstract: Further improvements to the pulsed EPR spectrometer of Huisjen and Hyde [Rev. Sci. Instrum. 45, 669 (1974)] are described. Special attention is given to techniques for separation of free‐induction‐decay and saturation‐recovery signals. The instrument is suitable for determination of spin‐lattice relaxation times as short as 10−7 sec, and is designed particularly for measurements on dilute solutions of free radicals and of spin‐labeled biomolecules. Analytical solutions of the Bloch equations are obtained that are appropriate for this instrument. The predictions of the equations have been verified by comparison with experiments on the tetracyanoethylene (TCNE) radical anion.
89 citations
TL;DR: In this article, the measured frequency response of wires in turbulent flow systems using circuits especially developed for the purpose was used to correct a temperature spectrum measured in a heated jet, and the corrected spectrum agreed well with the expected shape.
Abstract: In many areas of turbulence research of current interest, it is of increasing importance to make reliable measurements of high frequency, small scale temperature fluctuations. Platinum wire resistance thermometers provide adequate spatial resolution, but may, after a period of time, suffer a degradation in frequency response when used in air. Relative effects of various sensor parameters on sensor performance under various flow conditions are also discussed as a guide to sensor selection. However, measurements of actual frequency response of wires in turbulent flow systems using circuits especially developed for the purpose show substantial deviations from the analytic results, as well as a dependence of the frequency response on a probe aging effect, which is possibly due to surface contamination. The measured frequency response was used to correct a temperature spectrum measured in a heated jet. The corrected spectrum agreed well with the expected shape.
87 citations
TL;DR: In this paper, an apparatus was developed for the measurement of the effective permeability-thickness product of magnetic films for frequencies 1-100 MHz and permeances up to 20,000 μ with an accuracy of ±100 μ.
Abstract: An apparatus has been developed for the measurement of the permeance (effective permeability–thickness product) of magnetic films for frequencies 1–100 MHz and permeances up to 20 000 μ with an accuracy of ±100 μ. This is suitable for permalloy films in the 0.5–5 μ thickness range, which are used in thin film recording heads operating in this frequency range.
87 citations
TL;DR: In this article, the authors compared Ermer and Lifson's model with the most rational general CFF available, and found that the most significant discrepancies found to occur are those for certain stretch-stretch couplings assumed to be zero in the CFF, but shown to be appreciable by quantum calculation.
Abstract: Electron spectrometers working with electrostatic deflection are characterized by a typical background structure. Experimental investigations and model calculations for a 127° analyzer show that the major part of this background is caused by specular reflections of the electrons from the deflection plates towards the exit slits. The background is reduced by a factor ≳10 when the deflection plates are appropriately corrugated. In a comparison with the most rational general CFF available, that of Ermer and Lifson, the most significant discrepancies found to occur are those for certain stretch–bend couplings assumed to be zero in the CFF, but shown to be appreciable by quantum calculation. It is observed that these couplings, but not the stretch–stretch couplings, are well accounted for by a steric interaction model. The ab initio cubic constants examined display the same pattern of conformity with a steric model. Bend–bend–bend and bend–bend–stretch but not all stretch–stretch–stretch interactions agree wit...
TL;DR: In this article, the construction and signal processing methods of several experimental gas-filled, position-sensitive proportional counters (PSPCs) using resistance-capacitance (RC) position encoding are described, and guidelines for the design and operation of these counters are given.
Abstract: The construction and signal processing methods of several experimental gas‐filled, position‐sensitive proportional counters (PSPCs) using resistance–capacitance (RC) position encoding are described, and guidelines for the design and operation of these counters are given. Using these guidelines, we were able to improve the spatial resolution and shorten the signal processing time; for example, the intrinsic spatial uncertainty in the position measurement was reduced to 28 μ FWHM for alpha particles and 100 μ FWHM for low‐energy x rays (2–6 keV). Also, the signal processing time was reduced to 0.6 μsec without seriously degrading the spatial resolution. These results have widened the field of application of the RC position encoding method for position measurements of low‐energy photons, neutrons, and charged particles in a wide variety of nuclear physics experiments, in nuclear medicine imaging, and in low‐dose, medium‐resolution radiography.
TL;DR: In this article, a Drickamer-type apparatus was made in which the highly-stressed tip regions of the Carboloy pistons are of dense sintered diamond and the results showed that this apparatus is capable of attaining static pressures of over 400 kilobar on a newly revised scale.
Abstract: A Drickamer‐type apparatus has been made in which the highly‐stressed tip regions of the Carboloy pistons are of dense sintered diamond. Experiments indicate that this apparatus is capable of attaining static pressures of over 400 kilobar on a newly revised scale. The results show that the 1970 revised pressure scale of Drickamer needs further revision downwards for the range above about 150 kilobar. A pressure scale based on electric resistance transitions up to 400 kilobar is proposed. Resistance vs press force curves are shown for Bi, Fe20Co, Fe40Co, CdS, GaP, BP, NaCl, and graphite.
TL;DR: In this article, a stroboscopic pulse radiolysis system was described which detects the transient absorption generated by a 20 psec pulse from a 20 MeV linear accelerator, which was obtained by using, as the analyzing light, the short pulse of?erenkov light generated by the portion of the electron beam which passes through xenon.
Abstract: A stroboscopic pulse radiolysis system is described which detects the transient absorption generated by a 20 psec pulse from a 20 MeV linear accelerator. The time resolution is obtained by using, as the analyzing light, the short pulse of ?erenkov light generated by the portion of the electron beam which passes through xenon. The remaining portion of the electron beam is delayed by passing around a 270° magnet and the delay of the light may be varied by an optical delay line. Block diagrams for the electronics and the optics are given. The magnitude of sources of errors are discussed.
TL;DR: An x-ray monochromator system for the Al Kα emission line has been developed specifically for xray photoelectron spectroscopy as discussed by the authors, which is composed of a fine focus, high power xray tube with a water-cooled rotating anode and a spherically bent quartz crystal.
Abstract: An x‐ray monochromator system for the Al Kα emission line has been developed specifically for x‐ray photoelectron spectroscopy. It is composed of a fine focus, high power x‐ray tube with a water‐cooled rotating anode and a spherically bent quartz crystal. The parameters have been chosen to achieve very high resolution with acceptable intensity and to fulfill the geometrical conditions imposed by the electron spectrometer. A description is given of the adjustments and tests of the different components of this equipment. It is demonstrated, on the basis of spectra particularly suitable for this purpose, that a total instrumental line width of 0.3 eV or better is achieved.
TL;DR: In this paper, the secondary electron ejection coefficients for rare gas metastable atoms striking a stainless steel surface have been determined using an improved gas cell technique, and data are presented for He(2 1S), He( 2 3S), and Ne(3P0,2) atoms.
Abstract: Secondary electron ejection coefficients for rare gas metastable atoms striking a stainless steel surface have been determined using an improved gas cell technique. Data are presented for He(2 1S), He(2 3S), and Ne(3P0,2) atoms, and limitations of this technique are discussed. An alternative method for γ determination is described which utilizes laser induced photoionization rather than chemiionization, and results are presented for He(2 1S) and Xe(3P0).
TL;DR: In this article, a technique for making four probe conductivity measurements on small, fragile single crystals of organic compounds is described, where the physical constraint of the sample is minimal, allowing repeated thermal cycling.
Abstract: A technique is described for making four probe conductivity measurements on small, fragile single crystals of organic compounds. Physical constraint of the sample is minimal, allowing repeated thermal cycling.
TL;DR: In this paper, a two-way structural analysis of the accurate calibrations of 12 platinum resistance thermometers in the temperature range 2.5 to 14 K is presented. But the accuracy of these calibrations depends on the altitude of the thermometer.
Abstract: Calibration procedures are developed for platinum resistance thermometers in the temperature range 2.5–14 K. Two recommended methods require calibration points at the boiling point of liquid helium (4.215 K) and the triple point of hydrogen (13.81 K); in addition, the first method requires a point at 7.201 K while the second method requires the slope of the calibration curve at 13.81 K. For temperatures from 3.5 to 14 K, the calibrations are accurate to within 0.01 K for the first method and 0.025 K for the second method. For temperatures from 2.5 to 3.5 K, the calibrations are somewhat less accurate. Therefore, if a thermometer has been calibrated for temperatures of 13.81 K and above, its calibration may be easily extended to lower temperatures with sufficient accuracy for many applications. These calibration procedures were developed from two‐way structural analysis of the accurate calibrations of 12 platinum resistance thermometers.
TL;DR: In this article, a tunable CW laser was used to selectively remove either of the two metastable species, 3P 0,2, which are initially present in a neon metastable beam.
Abstract: A tunable CW laser has been used to selectively remove either of the two metastable species, 3P 0,2, which are initially present in a neon metastable beam. The method is applicable to other rare gases and provides the opportunity for separate investigation of effects due to atoms in either the 3P 0 or 3P 2 state.
TL;DR: In this paper, the counting efficiency of a channel electron multipier is measured for H+ and H− impact with the input of the Channeltron grounded and for impact energies between 0.3 and 5 keV.
Abstract: The counting efficiency of a channel electron multipier is measured for H+ and H− impact with the input of the Channeltron grounded and for impact energies between 0.3 and 5 keV. The counting efficiency is found to be about 30% greater for H− than for H+ at energies below 1 keV. This difference and an observed difference between H− and H+ in the variation of counting efficiency across the Channeltron opening are attributed to the surface potential of the Channeltron near the opening, which can accelerate or decelerate the incident particles.
TL;DR: In this paper, the detailed design and performance of a digital clipped correlator constructed as an integral part of a photon correlation spectrometer (PCS) is described, and the correlator is of a modular design and easily expandable to several hundred channels.
Abstract: The detailed design and performance of a digital clipped correlator constructed as an integral part of a photon correlation spectrometer (PCS) is described. The correlator is of a modular design and easily expandable to several hundred channels. Each channel contains a 4‐bit buffer storage, and the overflow bits from the storage are serially transferred into the memory of a multichannel analyzer. The dead time associated with the transfer is negligible. The sampling time of the correlator can be varied from 1 sec to 50 nsec. The principal features of the design are its simplicity, expandability, low cost, and optimal use of commercially available equipment.
TL;DR: In this article, a new merged-beam apparatus is described, which permits the measurement of the energy dependence of absolute cross sections for ion-neutral and neutral-neutral reactions yielding ionic products over the energy range <0.010 to ∼10 eV.
Abstract: A new merged‐beam apparatus is described, which permits the measurement of the energy dependence of the absolute cross sections for ion–neutral and neutral–neutral reactions yielding ionic products over the energy range <0.010 to ∼10 eV. The apparatus has a somewhat different geometry than that of any previous merged‐beam instrument and incorporates several innovations which facilitate the rapid measurement of relative cross sections, the accurate determination of the beam overlap integral, and the high‐resolution measurement of the product energy distribution. The performance of the instrument is illustrated with data on the reaction H+2 + H2 → H+3 + H.
TL;DR: In this paper, the beam focusing by aperture displacement (Δx) in a duoPIGatron ion sources was studied and the beam deflection angle was shown to be linear with Δx/z for the round aperture and with Δz/z*2 for the slit aperture, where z and z* are the extraction gap distance and the effective gap distance, respectively.
Abstract: Results are given of an experimental study of beam focusing by aperture displacement (Δx) in duoPIGatron ion sources Measurements with a single aperture, accel–decel electrode geometry show that the beam deflection angle is linear with Δx/z for the round aperture and with Δx/z*2 for the slit aperture, where z and z* are, respectively, the extraction gap distance and the effective gap distance Applying the result of the single aperture study to the multiaperture duoPIGatron sources, it was possible to increase the neutral beam injection power to the Oak Ridge Tokamak (ORMAK) plasma by ?40% Also presented are a discussion and comparison of other work on the effect of aperture displacement on beam deflection
TL;DR: The mass spectrometer for the investigation of the upper atmosphere composition and density employs a spherical antechamber connected to an electron impact ion source, an analyzing field of the monopole type, and a threefold detector system including one multiplier operated in the analog mode as discussed by the authors.
Abstract: On 22 November 1972 a gas analyzer was launched into earth orbit on board the satellite ESRO 4. This mass spectrometer for the investigation of the upper atmosphere composition and density employs a spherical antechamber connected to an electron impact ion source, an analyzing field of the monopole type, and a threefold detector system including one multiplier operated in the analog mode. The instrument measures neutral constituent number densities within the mass range 1−44 amu. The sampling frequency is one mass scan per 9 sec using a total bit rate of 90 bps. The laboratory calibration of the instrument sensitivities was performed using a gas flow method.
TL;DR: In this paper, a new technique, developed to measure the linewidth of a vibrating wire, is presented, with particular regard to the conditions under which the Stokes theory can be applied to real experiments.
Abstract: A new technique, developed to measure the linewidth of a vibrating wire, is presented in this paper. After a discussion on the accuracy of the method, the theory of the vibrating wire is reviewed, with particular regard to the conditions under which the Stokes theory can be applied to real experiments.
TL;DR: An automated calorimetry system for measuring heat capacity in the range 1–35 K and is capable of performing rapid, accurate specific heat measurements on very small samples.
Abstract: We describe an automated calorimetry system for measuring heat capacity in the range 1–35 K. The system employs an on‐line computer for signal averaging and data reduction and is capable of performing rapid, accurate specific heat measurements on very small (1–100 mg) samples.
TL;DR: An apparatus for inelastic neutron scattering experiments at low temperature is described in this article, which consists of an autofrettaged aluminum 7075-T6 alloy cell and a shield.
Abstract: An apparatus for inelastic neutron scattering experiments at low temperature is described. This pressure assembly consists of an autofrettaged aluminum 7075‐T6 alloy cell and a shield. The rupturing pressures for some cells have been measured at different temperatures; the efficiency of the shield has also been tested. These studies demonstrate the feasibility and the safety of experiments under high pressure up to 4 kilobar even at very low temperature.
TL;DR: In this article, the construction of proximity-focused MCP arrays of novel design in which photometric information from (n x m) picture elements is read out with a total of (n + m) amplifier and discriminator circuits is described.
Abstract: The production of simple and rugged photon-counting detector arrays has been made possible by recent improvements in the performance of the microchannel array plate (MCP) and by the parallel development of compatible electronic readout systems. The construction of proximity-focused MCP arrays of novel design in which photometric information from (n x m) picture elements is read out with a total of (n + m) amplifier and discriminator circuits is described. Results obtained with a breadboard (32 x 32)-element array employing 64 charge-sensitive amplifiers are presented, and the application of systems of this type in spectrometers and cameras for use with ground-based telescopes and on orbiting spacecraft discussed.
TL;DR: In this paper, the development of a large magnetized plasma source for wave propagation experiments is described, which employs a dc discharge in a weak magnetic field region and subsequent particle diffusion into a strong, uniform B‐field region.
Abstract: The development of a large magnetized plasma source for wave propagation experiments is described. The method employs a dc discharge in a weak magnetic field region and subsequent particle diffusion into a strong, uniform B‐field region. The resultant steady‐state plasma is uniform (8 cm⊥B0, 120 cm∥B0), quiescent (δn/n≲1%), has high density (ne≳1011 cm−3), a B0=1 kG, argon (3×10−4 Torr), and low collision rates (νen≃105 sec−1). The source can be easily scaled to larger dimensions. Plasma diagnostics with probes, microwaves, and spectroscopy for steady state and afterglow are described. Examples of wave propagation for ion acoustic waves, electron Bernstein waves, and lower hybrid waves indicate the versatility of the device.
TL;DR: In this paper, an inexpensive method to stabilize the frequency of a CO2 laser is described. The method is completely electronic and utilizes variations in the impedance of the laser plasma tube to produce a frequency correction.
Abstract: An inexpensive method to stabilize the frequency of a CO2 laser is described. The method is completely electronic and utilizes variations in the impedance of the laser plasma tube to produce a frequency correction.