bluuebunny/crossref_metadata_2025 huggingface dataset:
A Zone Refiner for Crystal Growth
Authors: Wood C. , Van Pelt B. , Hyland E.
Published: February 2004

A horizontal zone refiner has been developed for crystal growth of group V-VI compounds. Tin-oxide coated fused quartz tubes were used as transparent heating elements.
Conductivity Type Determination for Different Semiconductor Materials
Authors: Håkansson Håkan
Published: February 2004

A device is described which utilizes the rectification between a metal and a semiconductor to determine the conductivity type. Measurements can be done very rapidly by this method. The results that have been obtained for different semiconductor materials, such as silicon, germanium, gallium arsenide, gallium phosphide, and gallium nitride, are given and discussed.
Method for Vacuum Evaporation of SiO on Thin Plastic Films
Authors: Lachance Y. , Roy J. C.
Published: February 2004

A technique for the vacuum evaporation of layers of SiO, ≈300 Å thick, on metallized and nonmetallized plastic films, 1500–3000 Å thick, is described. We have found that these coated films are excellent substrates for thin uniform radioactive sources and targets in different applications.
Mercury Contamination Associated with McLeod Gauge Vacuum Pumps
Authors: Carstens C. J. , Hord C. A. , Martin D. H.
Published: February 2004

Some simple measurements on the mercury vapor emission from mechanical pumps which evacuate McLeod gauges are described. Conclusions are that such pumps are likely to filter the mercury vapor, rather than to pass it directly, thus reducing the mercury emission to a very low level. However, contamination of these pumps, their subsequent emission of mercury vapor, and their final disposal should be taken into consideration.
An 80 kV Do It Yourself High Voltage Vacuum Feedthrough
Authors: Gould Harvey A.
Published: February 2004

A high voltage vacuum feedthrough which can be constructed with limited facilities is described. Its main feature is a compression O-ring seal used in place of the conventional metal-to-ceramic, or metal-to-glass seals. This sealing technique permits fabrication of the feedthrough from easially machined materials, which may also be nonmagnetic.
Electrical Resistance Ratios of Evanohm Heater Wire at Low Temperatures
Authors: Hust J. G.
Published: February 2004

As a consequence of using Evanohm wire as heater elements in our thermal conductivity apparatus we have obtained extensive resistance-temperature data for wires from several spools at temperatures from 5 to 300 K. These data, reduced to resistance ratios, R(T)/R(273 K), show the variation of resistance with temperature as well as the degree of material variability.
An Optical Fluorescence System for Quantitative Pressure Measurement in the Diamond-Anvil Cell
Authors: Barnett J. D. , Block S. , Piermarini G. J.
Published: February 2004

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.
High-Pressure Dilatometer up to 22 Kilobars
Authors: Mizouchi Nobuyuki
Published: February 2004

A high-pressure dilatometer was devised to measure the length change of specimens under hydrostatic pressure up to 22 kilobars. The dilatometer uses a linear variable differential transformer and exhibits a hysteresis with pressure cycling. With a careful calibration of the dilatometer vs pressure, instantaneous measurements of the length change of a specimen can be made within a precision of less than 0.025%.
Production of Alkali Plasmas by Photoionization
Authors: Lieberman M. A. , Berg T. , Luksenberg M.
Published: February 2004

Pulsed, low temperature, alkali plasmas have been produced by photoionization of the vapor using a xenon flashtube uv source. Results are as follows: for cesium, ne>1011 cm−3 with 100% ionization; for potassium, ne≈1010 cm−3 with 2% ionization; and for lithium, ne≈2×1010 cm−3. The flashtube spectrum in the 2100–3200 Å range was measured.
A Technique to Measure High-Power Electron Beam Currents
Authors: Pellinen D. , Staggs V.
Published: February 2004

A technique has been used to measure electron beams in excess of 200 kA/cm2 with energies of 105−106 eV. The technique uses a high-level nanosecond risetime Faraday cup combined with a dielectric differential range filter to separate the primary electrons from low-energy charge carriers in the transport system. This technique has been the one used to measure primary beam currents in excess of 5×105 A with pulsewidths on the order of 100 nsec. When combined with a knowledge of particle energy, power flux and deposition profiles may be inferred. A derivation of the electric field generated at the cup collector is included.
Precision Wavelength Measurements in Near Infrared
Authors: Fredrickson J. E.
Published: February 2004

Wave number markers are simultaneously traced on the strip chart recording of near infrared spectra by use of an auxiliary optical system employing a Fabry-Perot etalon. The method is applicable to plane grating scanning spectrometers and is independent of spectrometer source, slit, and detector arrangement.
A Gas Cell Method for the Measurement of Secondary Electron Ejection Coefficients for Metastable Atoms on Metal Surfaces
Authors: Rundel R. D. , Dunning F. B. , Howard J. S. , Riola J. P. , Stebbings R. F.
Published: February 2004

A convenient method is described for measuring the secondary electron ejection coefficient for thermal metastable atoms striking a metal surface, thereby permitting the absolute determination of metastable atom fluxes. Potential sources of systematic error are discussed. Results are presented for He(21S) and He(23S) metastables striking a gas-contaminated stainless steel surface.
A Four-Pulse NMR Experiment Using Maximum Pulse Width
Authors: Mehring Michael
Published: February 2004

The classical four-pulse experiment of Waugh, Huber, and Häberlen (WAHUHA) is extended to the upper limit in pulse width which is possible in the four-pulse timing, i.e., the pulse width equals 1/6 of the cycle time. It is shown that coherent averaging is still in effect and high resolution in solids can be achieved to the same extent as in the δ pulse limit.
A Switching Circuit for a Low Voltage, Medium Current dc Power Supply
Authors: Luke Keung , Jacobs Robert , Whiteley Richard
Published: February 2004

A switching circuit is described by which the ouput of low voltage, medium current power supply may be converted to two square waves 180° out of phase from each other. Frequency response at 100 Hz, 1 kHz, and 5 kHz is shown. Maximum voltage and current are 9 V and 20 A, respectively.
In-Vacuum Foil Changer for Intense Relativistic Electron Beam Generators
Authors: Davitian H. , Sanford J. , Fleischmann H. H.
Published: February 2004

A device was built permitting in situ changes of the anode foil of high current electron accelerators and thus allowing sizable pulse rate increases of these accelerators.
Formation of Negative Hydrogen Ions in Direct Extraction Sources
Authors: Prelec K. , Sluyters Th.
Published: February 2004

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.
High Magnetic Field Production by Electromagnetic Energy Storage in a Superconducting Coil
Authors: Hairie A. , Fortini A. , Huissier M. , Sauzade M.
Published: February 2004

A new method to produce high pulsed magnetic fields has been developed. Capacitors generally used for the storage of energy have been replaced by a superconducting coil which requires less space and lower operating cost. The choice for the different elements of the setup is discussed. A low energy model has produced a field of 20 teslas with a time constant of 15 msec.
A Diode-Quad Bridge Circuit for Use with Capacitance Transducers
Authors: Harrison Dean R. , Dimeff John
Published: February 2004

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.
Low-Noise ac Bridge for Resistance Thermometry at Low Temperatures
Authors: Anderson A. C.
Published: February 2004

A bridge circuit is described which provides an increase in signal/noise by a factor of 10–100 over previous designs frequently used to monitor very low temperature resistance thermometers. The four-terminal arrangement reads directly in ohms and requires that only the thermometer be located in the cryostat.
Performance Characteristics of a Translatory, Magnetic Suspension System
Authors: Forgacs R. L.
Published: February 2004

An experimental study was conducted of the performance of a translatory, magnetic suspension utilizing ceramic permanent magnets for vertical support and servo-controlled electromagnets for lateral stability. Drag measurements were confined to low velocities ([less than double sim] 40 cm/sec); a typical measured value of drag coefficient is drag force/weight = 1.8 × 10−4 at 18 cm/sec. Use of laminated electrical sheet rather than mild steel should provide an order of magnitude reduction in this value. For low amplitude oscillations in a magnetic valley, drag decreases further by about two orders of magnitude; free oscillations have been observed to continue for 12 min. In contrast, instrument quality ball bearings have a friction coefficient in the 10 to 40 × 10−4 range. The total power required to maintain support is about two orders of magnitude lower than for a dc electromagnet suspension system. Assuming eddy current drag force proportional to velocity and hysteretic drag force independent of velocity, measured drag values extrapolated to high speed indicate that with laminated magnetic elements, the magnetic drag force would be low compared to air drag for a similarly suspended vehicle traveling at 270 m/sec (600 mph) in a tube evacuated to 10−3 atm. The vehicle coasting at this velocity would lose little more than 1% of its velocity in 93 km (53 miles).
An X-Ray Photoelectron Spectrometer Designed for Surface Research
Authors: Fraser W. A. , Florio J. V. , Delgass W. N. , Robertson W. D.
Published: February 2004

An x-ray photoelectron spectroscopy (ESCA) apparatus designed specifically for surface research is described. The features, included in one vacuum envelope, are ultrahigh vacuum, a high intensity x-ray source, a 10 cm mean radius hemispherical electron energy analyzer, sample cleaning by argon ion bombardment, sample heating by electron bombardment, and the facility for the collection of electron spectra as a function of angle relative to the surface plane of the sample. It is shown that (1) sample cleaning increases net signal strengths by factors as great as 14; (2) less than 2% of a monolayer of cesium on a clean molybdenum substrate can be readily detected; and (3) that ultrahigh vacuum is essential for investigation of well-defined surfaces. Surface sensitivity is increased by an order of magnitude when spectra are collected at low electron take-off angles relative to the surface plane, and the importance of measuring angular dependence of spectra for interpretation of data from surfaces is demonstrated.
Coaxial Cylinder Oscillating Viscometer
Authors: Masera M. Bosco
Published: February 2004

A new version of an oscillating crucible viscometer is described which presents some advantages over previous types: (1) simpler mechanical construction which does not need great accuracy;(2) the two parameters of the viscometer can be varied in an ample range, allowing the measurement of the kinematic viscosity of all kinds of liquids.
An NMR Preamplifier with Improved Signal-to-Noise Performance
Authors: Davies T. K. , Manning B. C.
Published: February 2004

A practical preamplifier modification is described which replaces the vacuum tube amplifier by a low noise cascoded dual field effect transistor. An improvement of 10 in signal-to-noise ratio has been effected using the Varian 4333 probe. These modifications are of potential application to NMR spectrometers other than the HA series.
Time Resolved Momentum Measurements of Charged Particles in an Intense Electron Beam
Authors: Patterson E. L.
Published: February 2004

A technique is described for using a fast scintillator and high speed streak camera in conjunction with a magnetic spectrograph to measure the time dependence of the momentum to charge ratio of particles. Time resolution, limited by the scintillator decay time, was 1.7 nsec. Momentum to charge ratios of positive ions and of electrons were measured in an intense relativistic electron beam.
20 kA PFN Capacitor Bank with Solid-State Switching
Authors: Posta Stephen J. , Michels Charles J.
Published: February 2004

A compact high-current pulse-forming network capacitor bank using paralleled silicon controlled rectifiers as switches is described. The maximum charging voltage of the bank is 1kV and maximum load current is 20 kA. The necessary switch equalization criteria and performance with dummy load and an arc plasma generator are described.
A Simple 2100°C 600 Watt Tube Furnace
Authors: Webb G. W. , Miller R. E.
Published: February 2004

We describe a quenching furnace suitable for inert gas or vacuum operation.
High Temperature Calibration of the P.A.R. Vibrating Sample Magnetometer
Authors: Hines W. A. , Moeller C. W.
Published: February 2004

A method is described for calibrating the sample temperature in the high temperature oven accessory of a Princeton Applied Research Corporation vibrating sample magnetometer over the range from room temperature to 1050 K.
A cryo-cooled mass spectrometer ion source for atmospheric composition measurements at supersonic rocket velocities
Authors: Offermann D. , Tatarczyk H.
Published: February 2004

The helium cooled mass spectrometer ion source was modified to avoid the formation of a shock in front of it during a supersonic rocket flight. Thus the undisturbed measurement of major and minor atmospheric constituents including reactive species becomes possible in the denser parts of the atmosphere. Two instruments of this kind were extensively tested and calibrated in the laboratory. Mass spectra were obtained from them during two successful rocket flights at altitudes above 83 km.
A photoionization mass spectrometer utilizing a high intensity molecular beam sampling system and synchrotron radiation
Authors: Parr Gary R. , Taylor James W.
Published: February 2004

A compact photoionization mass spectrometer utilizing a supersonic molecular beam sampling system is described. Beam intensities of the order of 3 × 1018 molecules/sr sec are obtained for CO2. The use of this apparatus with synchrotron radiation is discussed. Results are presented for C2H2 and CO2 which indicate the usefulness of the nozzle beam with its attendant thermal relaxation for photoionization mass spectrometry studies.
A versatile optical diffusiometer including a large optical bench of new design
Authors: Gosting L. J. , Kim H. , Loewenstein M. A. , Reinfelds G. , Revzin A.
Published: February 2004

An instrument is described which was designed for precision studies of isothermal diffusion in liquids by optical methods using interference fringes. This optical diffusiometer is described in some detail because it has been found to function exceptionally well for such studies and also because its main components and general design allow it to be adapted to a wide variety of optical measurements and other studies. It is basically a large precision optical bench. An 884 cm long steel beam serves as the rigid base on which are bolted stainless steel dovetail ways which extend along the full length of the beam; the contact surfaces of these ways are straight and flat to about 0.005 cm over their entire length. Riders which support the optical components may be clamped at any position along the 884 cm length of the ways. The riders are designed so that components mounted on them may be centered on and made perpendicular to the optic axis of the instrument. A special measuring rider is used in conjunction with measuring notches cut every 30.48 cm (12 in.) in one edge of the ways in order to determine the position along the ways of any other rider with an accuracy of about 0.002 cm. The entire instrument was designed with special emphasis on versatility, rigidity, precision, ease of adjustment, and freedom from vibration. This instrument permits diffusion coefficients to be measured with a greater precision than has been possible with previous models.
Measurement of hypersonic attenuation by means of stimulated Brillouin scattering
Authors: Leiderer P. , Berberich P. , Hunklinger S.
Published: February 2004

A light scattering technique to determine the lifetime of longitudinal phonons in the GHz range is described. The method allows one to measure phonon lifetimes between 5 and 1000 nsec and is applicable to transparent media, in which stimulated Brillouin scattering can be generated.
Emission properties of oxide cathodes using photoresist binder
Authors: Gray Henry F. , Haas George A.
Published: February 2004

The electron emission capability of recently developed thermal electron emitters which can be delineated into small areas of almost any desirable shape by standard photolithographic processes has been studied. The emission performance is found to be comparable to standard sprayed oxide coated cathodes, i.e., the effective work function φE(1000 K) ≃ 1.66 ± 0.50 eV and ΔφE/ΔT ≃ 6.3 × 10−4 eV/K.
A bridge method for simultaneous measurements of coupling coefficient and loaded Q of a single-ended cavity
Authors: Watanabe Kenzo , Takao Iwao
Published: February 2004

A bridge method which allows the simultaneous measurements of the coupling coefficient and the loaded Q of a single-ended cavity is described. The measuring system consists of a ``magic T'' bridge and incident power monitor circuits. Two collinear arms of the magic T are terminated by the cavity under measurement and the built-in short at equal distances. Measurements are made by comparing the reflected power from the bridge with the incident power on the cavity.
Sealable sample holder with internal reference for NMR measurements on cellulosic materials
Authors: Nanassy A. J.
Published: February 2004

A Pyrex sample holder encloses a polytetrafluoroethylene container which seals the sample. The nuclear magnetic resonance (NMR) spectrum of fluorine in the material of the container serves as a reference.
Longitudinal magnetic fields for Mössbauer experiments with a conventional electromagnet
Authors: Petitt Gus A. , Walter Robert J.
Published: February 2004

A conventional electromagnet has been modified by using tapered pole caps with axial holes drilled through the pole cap faces to apply longitudinal fields to the absorber in Mössbauer absorption experiments. Fields in excess of 25 kOe are obtained with the apparatus described. In order to demonstrate the performance of the apparatus, spectra of the ferrite Li0.2Zn0.4Fe2.4O4 are shown and the magnetic hyperfine fields at A and B sites are obtained.
Miniaturized logarithmic count-rate circuit
Authors: Rochelle J. M. , Kennedy E. J.
Published: February 2004

A four-decade, logarithmic count-rate circuit with a log transistor as the feedback element in an electrometer amplifier was designed and constructed for measuring periodic or random inputs. This new design enables a much greater degree of miniaturization than possible with the conventional, parallel diode-pump configuration. Pulses of constant charge are supplied to the log electrometer by a common-base transistor current source that is driven by a stable univibrator. Frequency compensation of the electrometer is not required because of the stabilizing influence of a 0.1 μF feedback capacitor that maintains the output voltage ripple at < 1 mV peak-to-peak for periodic inputs. The electrometer output changes 1 V per decade from + 4 to 0 V as the average input rate increases from 10 to 105 counts/sec. From 0 to 50 °C the total output voltage zero drift is < ± 10 mV and the 1 V per decade calibration changes < ± 10 mV. The maximum error of the logarithmic conversion is < 1% referred to the output voltage. A figure of merit for the output response to a step change in input frequency is defined as the number of pulses required for the output to reach 90% of the difference between the initial and final output voltages. This response number is plotted as a function of the ratio of the initial and final input rates.
A simple double-pass spherical Fabry-Perot interferometer
Authors: Cannell David S. , Lunacek Joseph H. , Dubin Stuart B.
Published: February 2004

We have constructed a double-pass spherical Fabry-Perot interferometer using an optical isolator. The resulting instrument is completely stable and has an instrumental profile with a full width of 4.8 MHz. The transmission drops to 10−3 of the peak transmission at 17 MHz from the frequency of maximum transmission.
Fringe-shift generators for characterizing interferometer system response
Authors: Henry K. W. , Carlson G. A.
Published: February 2004

Two techniques have been developed for the generation of well characterized fringe patterns in displacement and velocity interferometers. In the first, a piezoelectric crystal placed at the interferometer target location is oscillated at resonance with applied ac voltages near 100 V. Quartz or lithium niobate crystals with resonant frequencies near 1 MHz produce surface displacements of 200–1000 nm, and peak surface velocities of 0.4–4.0 m/sec. The fringe-shift patterns produced in the interferometer using this technique can be used to test various aspects of the interferometer performance. The second technique employs a fused silica disk which is rotated in one leg of the interferometer. This rotation introduces a large variation ([inverted lazy s] 0.3 mm) in the optical path length of the interferometer leg during each revolution, giving a fringe shift of hundreds of fringes. This technique is especially useful for maximizing interferometer fringe contrast during setup of the instrument.
Direct digital output of time-resolved mass spectrometric data
Authors: Seyse R. J. , Anderson W. R. , Ormerod R. C. , Powers T. R. , Rose T. L.
Published: February 2004

A simple, inexpensive method to obtain digital information about the time development of the intensity of a mass peak from a time-of-flight mass spectrometer is described.
High-gain imaging electron multiplier
Authors: Colson W. B. , McPherson J. , King F. T.
Published: February 2004

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.
The electric field and geometrical factor of an annular curved plate electrostatic analyzer
Authors: Moestue H.
Published: February 2004

Response and geometrical factor of a charged particle energy spectrometer are presented. Both a theoretical and an experimental approach are used. A set of two annular curved deflection plates constitutes the energy analyzer of the spectrometer. The analyzer has the features of large geometrical factor, high angular and energy resolution, and small size, which makes it specially well suited for space flight applications.
A simple turbidimeter for rapid determination of low bacteria concentrations
Authors: Piccialli Aldo , Piscitelli Sergio
Published: February 2004

A differential photometric ratio system for turbidity measurements is described. The high sensitivity of this instrument permits the measurement of very low densities of bacterial populations suspended in liquid media. The sensitivity is in the range between 104 and 106 cells/ml in natural aquatic environments.
A double beam photon counting spectrophotometer
Authors: Schlesinger M. , Szczurek T.
Published: February 2004

A rather simple double beam adapter which makes possible the use of a McPherson model 225 vacuum uv monochromator as a double beam spectrophotometer is described. The principal features of the instrument are a photon counting arrangement resulting in a digital ratio measurement and an analog trace end result.
A versatile and inexpensive electronic system for a high resolution NMR spectrometer
Authors: Kan S. , Gonord P. , Duret C. , Salset J. , Vibet C.
Published: February 2004

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.
Ultrahigh vacuum systems using low temperature pumps
Authors: Shen L. Y. L.
Published: February 2004

Low temperature pumping is utilized to achieve pressures as low as 10−11 Torr. In the first method, the entire sample chamber is immersed inside liquid helium. The second method, which is more economical than the first one, combines a large capacity titanium sublimation pump and a small cold trap immersed inside a liquid-helium storage Dewar. The ultrahigh vacuum system described here is economically competitive with the best ion-pumped vacuum system available today.
Theoretical and experimental sensitivities of ESR spectrometers using maser techniques
Authors: Mollier J. C. , Hardin J. , Uebersfeld J.
Published: February 2004

We have considered theoretically and experimentally a paramagnetic resonance spectrometer, whose cavity contains both the sample to be studied and a beam of ammonia molecules capable of stimulated emission. Different modes of operation are investigated: classical, ``Q-multiplier'' and marginal oscillator spectrometer. In these two latter cases, the ultimate sensitivity is determined only by the thermal noise in the cavity. It is shown to be the theoretical sensitivity of a spectrometer using a perfect receiver. This sensitivity can be achieved if the stored energy does not exceed an upper limit, depending on properties of the active molecules-typically 5 × 10−18 J for NH3.
A filter-wheel solar radiometer for atmospheric transmission studies
Authors: Shaw Glenn E. , Peck Ronald L. , Allen Garry R.
Published: February 2004

A filter-wheel solar radiometer has been developed for monitoring the atmospheric optical depth at multiple narrow-wavelength intervals in the visible and near ir regions of the spectrum. Measurements of the direct solar radiations are converted to a digital format and stored in punched tape for eventual analysis by a computer. During stable clear weather condition, the instrument is capable of providing monochromatic optical depths to an estimated rms accuracy of 0.005.
Technique for making a groove for an O-ring distorted to a nonplanar configuration
Authors: Hertzler B. L. , Kaufman M.
Published: February 2004

An O-ring vacuum seal is made around a small hole in the wall of a circular tube by using a groove that is machined in a flat copper disk, which is then pressed to the curvature of the tube.
A technique for high precision angular displacement using a modified Ortec 3701 B positioning mechanism
Authors: Peixoto E. M. A. , Nogueira J. C. , Ayrosa A. G. , de Souza G. G. B.
Published: February 2004

A technique is described for improving the angular resolution of the Ortec 3701 B positioning mechanism by one order of magnitude. This technique extends the original resolution to an angular resolution of 0.01°.
Low temperature InSb Hall plate with suppressed de Haas-Shubnikov effect
Authors: Polák M.
Published: February 2004

A modified InSb Hall plate for measuring magnetic fields at low temperatures is described. The quantum de Haas-Shubnikov oscillations of the Hall voltage are suppressed by heating the semiconducting plate inserted in a ceramic cover.
The Measurement of Short-Lived Fluorescence Decay Using the Single Photon Counting Method
Authors: Lewis Colin , Ware William R. , Doemeny Laurence J. , Nemzek Thomas L.
Published: February 2004

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.
Transition Region Response of the Symmetric Double Probe and Its Application in the Lower Ionosphere
Authors: Szuszczewicz Edward P.
Published: February 2004

The technique of the symmetric double probe lends itself to the in situ measurement of plasma temperature in the ionospheric D region because it can lead to meaningful results under relatively high collision frequencies where the Langmuir probe has been observed to fail. For a completely thermalized plasma and over parametric ranges 0.1≤λia / Rp ≤100 and 0.004≤Rp/λD≤100, where λia is the ion-atom mean free path, Rp is the probe radius, and λD is the Debye length, it is shown that the modification to the original collision-free double-probe theory of Johnson and Malter for the determination of electron temperature is never greater than 12%, with a value of (8 ± 2)% nominally applicable in the case of D-region diagnostics. This technique has been successfully operated on a Nike-Cajun payload flown at midday from White Sands, N. M. to an apogee of 78.5 km. The associated electronics and deployed double-probe configuration are presented, and a current-voltage characteristic collected in the ascent stage at 73.7 km is briefly discussed. The values of electron temperature indicated by the sampled data are [inverted lazy s] 30% higher than those predicted by theory for the anticipated state of thermal equilibrium with the ambient neutrals. The importance, however, is that these values, of the order of 300 K, are the lowest ever reported by any in situ method operative in the D region and consequently point out the strong potential of the double-probe technique in future applications to regions of planetary ionospheres which cannot be considered as collision-free.
A Bellows-Type Differential Compressimeter for Determining the Difference between the Compressibilities of Two Seawater Solutions to 900 bars
Authors: Duedall I. W. , Paulowich S.
Published: February 2004

An apparatus was constructed to measure directly, to 900 bars, the difference between the isothermal compressibilities of two seawater solutions whose compositions differ with respect to one component. The instrument is being used to determine how specific sea salts affect seawater compressibility; this information will be used to study hydration of ions in seawater. The main design feature of the apparatus is that two equal-volume bellows-type densimeters are arranged back-to-back inside the same high-pressure vessel. In operation, one bellows is filled with a test solution and the other bellows is filled with a reference solution. As hydrostatic pressure is applied to the two solutions the bellows compress differentially owing to the difference between the compositions of the reference and test solutions. The differential displacement of the two bellows is measured with a linear differential transformer network, and it is directly related to the difference between the isothermal compressibilities of the test and reference solutions. The apparatus has been calibrated using an absolute technique. In a series of trial runs at 15°C, as a check on the calibration, where the reference solution was distilled water and the test solution was seawater of 35‰, the precision of the method ranged from ±0.03×10−6 to ±0.07×10−6 bar−1 over the pressure range 100–900 bar. The actual compressibility difference values ranged from −3.42×10−6 ±0.06×10−6 bar−1 at 100 bar to −2.41×10−6±0.03×10−6 bar−1 at 900 bar; these values are within +0.01×10−6 to −0.39×10−6 bar−1, respectively, of one set of present literature values. Some additional seawater measurements made at 10°C were within −0.06×10−6 to −0.12×10−6 bar−1 of the most recently determined compressibility measurements carried out by Bradshaw and Schleicher who used a glass dilatometer. Also some measurements made at 25°C on 0.7615 m NaCl vs deionized-distilled water compared within −0.07×10−6 to −0.22×10−6 bar−1 with the recently reported compressibility data of Millero et al., who made their measurements using a high-precision magnetic float densimeter.
An Evaluation of the Heat Pulse Anemometer for Velocity Measurement in Inhomogeneous Turbulent Flow
Authors: Tombach Ivar H.
Published: February 2004

A velocity measuring probe that creates a train of heat pulses at one point in the flow and detects their arrival at a sensing wire a short distance downstream has been developed for the measurement of turbulent flows of unknown composition. In such a turbulent flow the detected pulses are highly disturbed, but reconstruction of a mean pulse, by digital computer, from several hundred pulses enables calculation of a mean velocity and a velocity fluctuation level. To illustrate the application of this technique, velocity profiles were measured in inhomogeneous turbulent jets over a wide range of jet ambient density ratios.
An External Goniometer for Orientation of a Cryostat
Authors: Lockhart N. C. , Nichols L. F. , Eckhardt C. J.
Published: February 2004

An economical two-circle orienting external goniometer has been designed and fabricated for an Andonian liquid helium Dewar. The Dewar can be tilted ±30° from the vertical in two perpendicular directions. The geometrical center of the Dewar's optical cavity moves a maximum of 1 mm when the cryostat is tilted the full 30°. The basic design involves the rotation of two concentric cylinders riding on bearing surfaces. Two chain belts and gear boxes are used as drive mechanisms.
A Resistive Electrode, High Energy, Transverse Laser Discharge
Authors: Johns T. W. , Nation J. A.
Published: February 2004

A two electrode discharge system for use in TEA carbon dioxide lasers is described. Stabilization of the discharge against the formation of spark channels is achieved through the use of resistive composition electrodes. These provide a series ballast resistance preventing the negative dynamic resistance of the plasma from leading to spark formation. Energy depositions of up to 300 J/liter have been achieved in a lasing mixture without spark channels forming.
A Microwave Resonator for Studying Chemical Laser Reactions
Authors: Wollrab J. E. , Rasmussen R. L.
Published: February 2004

A near semiconfocal Fabry-Perot resonator has been integrated with a small chemical laser to permit detection of ground and excited vibrational state rotational transitions of the reaction products within the laser cavity without perturbing the laser system. The effective lifetimes of unstable gas-phase species can also be followed by monitoring the maximum value of the absorption coefficient.
Detection of Paramagnetic Resonance by Saturation Effect
Authors: Boivin C. , Jacolin C. , Savard J. Y.
Published: February 2004

Bloch equations are solved in amplitude modulation of the rf field, and it is shown how the saturation can be put to use in obtaining a new kind of detection. A practical realization of a saturation effect spectrometer is given and some experimental results shown.
Production of Uniform Microspheres
Authors: Fulwyler M. J. , Perrings J. D. , Cram L. S.
Published: February 2004

A new technique has been developed for producing microspheres uniform in volume and fluorescence or radioactive tracer. Very uniform spheres with selected diameters are produced by introducing one liquid into the center of a moving stream of a second liquid (of differing surface tension) and breaking the core stream into uniform droplets by the action of a piezoelectric transducer. Fluorescent spheres of 10 μ diam have been produced having a coefficient of variation in volume and fluorescence as low as 3.6%. This corresponds to a diameter variation of about 1.5%.
Use of Open-Structure Channel Electron Multipliers in Sounding Rocket Experiments
Authors: Timothy J. G.
Published: February 2004

The performance of open-structure channel electron multipliers has been investigated in a laboratory simulation of the ascent pressure profile for a typical sounding rocket. The results of this test demonstrate that evacuation of the payload prior to launch is necessary for experiments where stability of response is an essential parameter.
Optimal use of Double Pin Ionization Gauges for Shock Wave Detection
Authors: McClenahan James O.
Published: February 2004

Quantitative use of a high speed shock tube depends upon the ability to detect the time of arrival of the shock wave at a given position, with a resolution of 1 μsec or better so that (1) the velocity of the shock wave can be determined and (2) the various instruments attached to the shock tube can be triggered or energized at the proper time. Of the many types of gauges available for detecting the arrival of a shock wave at a given point, ionization gauges are the simplest and are capable of producing higher signal levels without the use of complicated electronic circuitry. For these reasons ionization gauges are usually the preferred shock wave detectors. Their use has been limited, however, by the fact that the range of shock tube operating conditions at which they perform satisfactorily is small. This paper describes a new method of using ionization gauges by systematically adjusting the electronic circuitry to allow for large ranges in shock tube operating conditions. This method should be useful in various applications where ionization gauges are used to detect shock waves.
A Simple Microscope Attachment for a Cary 14 or 17 Spectrophotometer
Authors: Ferguson J. , Orr W.
Published: February 2004

A description is given of a simple device which uses two 15-power reflecting objectives, mounted in the cell compartment of a Cary 14 or 17 spectrophotometer. Spectra of crystals with surface area as small as 0.1 mm2 can be measured in polarized light at temperatures as low as 6 K. The absorption spectrum of a crystal of 9, 10 dimethylanthracene is given as an example.
Liquid Level Detector for Use by the Blind
Authors: Roberts Richard W. , Jernakoff George
Published: February 2004

A novel, safe device is described which indicates when a vessel is filled to some predetermined level with a conducting liquid.
A Recirculation Compressor for Hot Gases
Authors: McGregor D. E. , Walsh G. T. , Lana I. G. Dalla
Published: February 2004

A conventional sliding-vane rotary compressor was modified for use in recirculating hot gases at design temperatures up to 425°C. The compressor has performed well at 350°C with gaseous streams of H2S, SO2, COS, CO2, N2, H2O, and Sx. Completely free of lubricants, only stainless steel and graphite surfaces are exposed to hot gases. The unit may be mounted within a heating medium for isothermal operation.
A Simple Technique for Determining the Sign of Thermal Conductivity Anisotropy in Nematics
Authors: Rajan Varagur S. V. , Picot Jules J. C.
Published: February 2004

A simple method of observing the anisotropy of heat conduction in nematic mesophases is discussed.
A Simple Optical Attachment to the Lang Camera for Selecting the Photographed Region on the Crystal
Authors: Mardix S.
Published: February 2004

An attachment to the Lang camera is described, consisting of a light source and a mirror. When the mirror is switched in the x-ray beam path, the light beam is reflected by the mirror through the collimating slits on the crystal, thus giving a simple way for selecting the photographed region.
Short Sample Testing of Very High Current Superconductors
Authors: Purcell John R. , DesPortes Henri
Published: February 2004

An apparatus is described for ``short sample'' testing at high currents using the induced current method. Primary currents of 100 A would produce up to 16 000 A secondary current. The method of measuring the secondary current and results are given.
A High Speed X-Radiographic Camera for Use in the Electron Beam Environment
Authors: Wood Donald Scribner
Published: February 2004

A high-speed X-radiographic camera to radiograph blowoff products from materials subjected to high-energy deposition by pulsed electron beams is described. Information obtained is average material density as a function of time and distance from the sample surface and is used to improve predictive hydrodynamic models. The camera design overcomes the difficult diagnostic problems of intense background radiation (bremsstrahlung), scattered electrons and electromagnetic interference usually associated with the electron beam environment. Conventional x-ray film is mounted on a disk which rotates inside of a shielded housing. Data are recorded through a slit in the housing near the edge of the film disk (polar coordinate geometry) in either a flash (framing) or continuous (streak) mode. X-ray energies used were 20–30 keV. Maximum speed of the film past the slit is approximately 0.04 cm/μsec.
An Improved Infrared In Situ Cell for Gas Adsorption Studies
Authors: Igarashi A. , Ogino Y. , Onodera S.
Published: February 2004

A simple infrared cell was developed to study gas adsorption on a catalyst. The main body of the cell was made of Pyrex glass. Windows were attached to the cell body by means of O-ring seals with water-cooled brass rings. A heating assembly with tungsten windings was set in the cell. This cell could be used at temperatures up to 450°C, either under vacuum to a pressure of 10−6 Torr or in any controlled atmosphere.
Hall Probe Loop for Nulling Induced Voltages from ac Magnetic Fields
Authors: Cottles V. M. , Hermann A. M.
Published: February 2004

A simple Hall probe loop which can be adjusted to null induced voltages from ac magnetic fields is described. With its use induced voltages have been reduced to the microvolt region allowing Hall effect measurements without the use of bucking voltages in low mobility materials.
A Two Frequency ac Hall Apparatus for Measurements in Metals
Authors: Yahia J. , Perluzzo G.
Published: February 2004

A novel and simple two frequency ac Hall apparatus is described and some results obtained using it are presented.
Logarithmic Readout Attachment for Double-Beam Spectrophotometers
Authors: Shepherd J. R. , Hedgpeth H. R.
Published: February 2004

The described attachment will process the output from a manual readout spectrophotometer, take the log10 of reference minus the log of the signal (log10 Io/I), and feed that to a recorder.
A Digital Electrode Controller for the Spark Source Mass Spectrometer
Authors: Fergason Lewis A. , Dowdy John D.
Published: February 2004

An automatic electrode controller is described for an r.f. spark source mass spectrometer. It maintains the spacing between the electrodes to provide constant breakdown voltage.
Measurement of Contrast Changes in Scanning Electron Microscopy
Authors: Schulson E. M.
Published: February 2004

A direct and rapid method is described for measuring changes in contrast on SEM images. The method is based on the fact that a given level of contrast can be detected only if the beam current at the specimen exceeds a critical value.
A Function Generator for Dynamic Control of a Plasma
Authors: Ogata Atsushi , Watari Tetsuo
Published: February 2004

A function generator is constructed to generate voltage as any given function of input voltage. The generator approximates any function including a nonmonotonic one by quantizing it into 11 steps. It has fast response (less than 100 nsec), good frequency characteristic (up to 10 MHz), and is easy to construct. It is to be used with a V-to-f converter in a feedback loop of rf confinement of a plasma, where the most favorable frequency is given as a nonlinear function of plasma density.
Measurement of Work Function Change in a Display-Type LEED-Auger Apparatus
Authors: Fritz J. H. , Haque C. A.
Published: February 2004

A facility to determine work function changes was developed in a display-type Varian 120 LEED-Auger apparatus, using the electron beam retarding potential technique. Using the known work function value of a reference material that is atomically clean, as verified by Auger electron spectroscopy, the average work function of other materials of interest can be evaluated.
A Low Resolution Scanning Multiple Fabry-Perot Spectrometer
Authors: Drummond David , Gallagher Alan
Published: February 2004

A low resolution scanning multiple Fabry-Perot spectrometer has been built for the observation of very weak extended light sources. The instrument consists of three sets of 7.6 cm diam Fabry-Perot plates operated in central order; their spacings are in a 3–4–5 ratio and are servo controlled using reference light provided by a single master grating monochromator. The instrument is scanned by varying the wavelength setting on the grating instrument. The resolution of the instrument is variable through the range 0.5–15 A, and its luminosity is equal to that of a 5 cm interference filter with a 65% peak transmittance. The free spectral range is about 125 times the peak half-width. Wavelengths in that range are transmitted at a level of 10−4 or less of the central transmission peak.