bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic Zone Refiner for Organic Compounds
Authors: Sloan G. J. , McGowan N. H.
Published: February 2005

A simple mechanism has been developed to carry out reciprocating motion in zone refining; this motion pattern provides, in effect, an infinitely long heater. The ingot is raised slowly into a battery of heaters, and is then cyclically moved quickly downward and slowly upward through one interzone distance. The unit includes a programmer that discontinues the refining after one to 100 passes. An easily fabricated heater assembly, suitable for use between 50 and 350°C, is also described.
Nozzles for Air Flow Measurement
Authors: Voss L. R. , Hollyer R. N.
Published: February 2005

A relatively simple relation between the discharge coefficient and the Reynolds number is developed for low-velocity air flows through a smooth approach nozzle. This expression is experimentally verified for a range of flows up to 650 ft3/min. It is shown to be accurate to ±½% of the measured values. For the particular approach profile used in these tests, it has been found that flow separation occurs in the smaller nozzles.
Apparatus for the Measurement of the Photomagnetoelectric Effect
Authors: Cunningham R. W.
Published: February 2005

This paper considers the requirements for construction of equipment to measure short circuit photomagnetoelectric currents. A material figure of merit is defined. From this an equipment sensitivity is obtained as the minimum measurable diffusion length per unit signal-to-noise ratio at small magnetic fields. The equipment described is able to measure a diffusion length as short as 4.2×10−4 cm for most semiconductors. The effect of nonlinear short circuit currents with photon flux is considered. It is shown that the measured short circuit current, expressed as a power series in the photon flux, can be analyzed with negligible error for expansions up to third order. If more terms are required, the relative error will remain small for higher order expansions. Extension to other photo experiments is also discussed.
Beckman IR-7 Infrared Spectrophotometer Modifications
Authors: Krueger P. J. , Schulze G. H.
Published: February 2005

The design, construction, and operation of a fiducial wavenumber marking system for the Beckman IR-7 infrared spectrophotometer is discussed. The system is activated by the uniform rotation of the main monochromator shaft, and superimposes regularly spaced marks on the recorded spectrum. This modification permits an exact evaluation of the frequency precision and linearity of a spectrophotometer with a cam frequency drive system, as well as the measurement of absolute frequencies with an accuracy of up to ±0.05 cm−1 in the first and second grating orders, and up to ±0.10 cm−1 in the third and fourth orders. A variable scanning speed control circuit and an auxiliary gear train for abscissa expansion are also described.
Sample Holder for Dielectric Measurements up to 700°C
Authors: Hrizo J. , Subbarao E. C.
Published: February 2005

A sample holder is described which has been used for the investigation of dielectric properties of ferroelectric materials from room temperature to over 700°C at frequencies up to 100 kc. It has also been used to observe hysteresis (D-E) loops of ferroelectrics in ceramic and single crystal form.
High Intensity Molecular Beam Apparatus
Authors: Deckers J. , Fenn J. B.
Published: February 2005

A high intensity molecular beam apparatus is described which is based on a supersonic stream gas source. Intensities of the order of 1017 molecules/cm2/sec have been achieved with nitrogen. The effects on performance of Mach number, source pressure, and geometry are summarized. Results are compared with theory.
Wide-Band Pulse Transformers for Matching Low Impedance Loads
Authors: Tansal Sabih , Sobol Harold
Published: February 2005

Pulse transformers capable of matching the low impedance load characteristics of integrated circuits are discussed. Experimental models constructed by winding transmission lines on cores were found to pass pulses with rise times between 1 and 2 nsec and with little droop for pulses of 300-nsec width. A transformer in liquid helium transmitted a 1-μsec pulse with less than 10% droop.
Magnetic Suspension Balance Method for Measuring Resistivities of Metals
Authors: Pankey Titus
Published: February 2005

The excellent sensitivity of a permanent-magnet type magnetic suspension balance was utilized in a simple method for measuring the resistivities of bulk quantities of metals and alloys, based on the Arago effect. An estimated accuracy of 2% was obtained on samples 2.85 cm in diameter in the range 10−4 to 10−6 Ω-cm. Skin effects were negligible in samples this size, as the frequency of the excitation field was less than 1 cps.
Light Probe for the Measurement of Turbulent Concentration Fluctuations
Authors: Lee Jon , Brodkey Robert S.
Published: February 2005

The design, construction, and theory of a light probe for the measurement of turbulent concentration fluctuations are given. Consideration is given to the measurement of the mean concentration, as well as the necessary corrections for noise. The limitations associated with the sample volume size, frequency response, and signal-to-noise ratio are discussed. Recommendations for improvement beyond the present sample volume of 5.6×10−4 cc, and a frequency response of 10 000 cps are given.
GaAs p-n Junction Diodes for Wide Range Thermometry
Authors: Cohen B. G. , Snow W. B. , Tretola A. R.
Published: February 2005

It has been observed that the forward voltage drop, at constant forward current, of a GaAs diffused p-n junction varies almost linearly with temperature from 2.0°K to above 300°K. Since carrier ``freeze-out'' at low temperatures is not observed, these junctions make excellent cryometers. In addition, these diodes exhibit good repeatability on temperature cycling and an insensitivity to magnetic fields. The sensitivity of the devices measured near room temperature is ΔV/ΔT≈−3.5 mV/°C, If=0.1 μA; ΔV/ΔT≈−2.0 mV/°C, If=1.0 mA. The sensitivity decreases slowly toward lower temperatures and at liquid helium is −1.5 mV/°C and is essentially independent of current. This high and nearly uniform sensitivity over such a wide temperature range is unique among low temperature thermometers. The shape of the temperature-voltage characteristic, with current as a parameter, is explained quite satisfactorily for T>50°K by assuming that the device conducts primarily recombination-generation currents, according to the theory of Sah, Noyce, and Shockley. Below 50°K certain deviations from this theory occur, but the applicability of the devices to thermometry is not affected. It appears likely that these devices are capable of a temperature resolution of at least ±0.01°C over the entire range investigated, using ordinary current sources and precision potentiometers.
Deflecting Mode in Circular Iris-Loaded Waveguides
Authors: Hahn H.
Published: February 2005

The theory of the deflecting or hybrid electromagnetic mode in an iris-loaded waveguide is presented. The dispersion diagrams of the two lowest passbands are computed and compared with experimental data. TM1 and TE1 modes are no longer independent solutions of Maxwell's equations if the phase velocity equals the velocity of light. In this case the most general field expressions require the use of hybrid solutions, which are derived from Hertzian vectors with transverse components. The hybrid solutions, in contrast to transverse solutions, are able to give a transverse deflection to synchronous, ultrarelativistic particles. The fields in the slot region and the center region of the iris-loaded waveguide are represented as Fourier series. Matching the four tangential field components results ultimately in an infinite matrix. A vanishing determinant constitutes the relationship between wave number, phase velocity, and geometry. A simple first-order approximation is derived and interpreted.
Regulation of Ionization Gauge Emission Current to Better than 0.05%
Authors: Yee Kenneth W. , Carpenter Robert J.
Published: February 2005

A control system is described for regulating the temperature-limited emission current from the filament of an ionization gauge tube. A dc transistor circuit is used with a lamp and a photosensitive resistor to provide electrical isolation between the control and the controlled circuits. Emission currents from 10 to 0.5 mA can be maintained with a stability of better than 0.05% with the system.
Application of Differential Thermal Calorimetry to Measurements of Stored-Energy Release in Metals
Authors: White J. L. , Koyama Karl
Published: February 2005

A differential calorimeter operating by the method of quantitative differential thermal analysis was developed to study stored-energy release spectra in metals. The method involves the heating of a test specimen and a fully annealed reference specimen by heat transfer from a uniformly heated calorimeter block programmed to a reproducible increase in temperature with time. The initial stored-energy release run is followed by a base-line run under identical conditions to compensate for differences in thermal coupling of the specimens to the block. The most stable conditions of thermal coupling have been obtained by the use of cells to contain the specimens and by continuous purification of the helium used as a thermal-exchange gas. Calibration experiments on the heat of fusion of lead were carried out to evaluate the thermal coupling between specimens and to confirm the calorimetric technique. Typical results for high purity copper deformed in compression are given to demonstrate the existence of an appreciable grain-size effect on the stored-energy release; the precision is approximately ±0.4 cal/g-atom for total stored energies of the order of 5 cal/g-atom.
High-Vacuum Dual-Motion Feedthrough
Authors: Gerber J. F.
Published: February 2005

This paper describes several versions of a single, simple device to provide rotary and linear motion within a vacuum chamber without causing even a temporary rise in pressure. Through the use of metal gaskets, bellows, seals, and magnetic couplings, many difficulties arising from the transmission of rotary and linear motion through vacuum-chamber walls are overcome. In the device described, freedom of rotation is unlimited in either direction, but linear movement is limited to 2 in. Actually, stroke limits are determined by choice of bellows and space considerations. The device makes use of magnetic coupling for the rotary component, and a bellows-sealed, lead-screw mechanism controls linear movement.
Beam-Profile Detector
Authors: Solomon Julius , Andreae Sypko W.
Published: February 2005

A beam-profile detector that employs a pair of continuously moving scintillation counters as a detector and a PHA as a multichannel scaler is described. The number of counts per fixed number of incident particles at every 0.1 in. of travel is recorded in consecutive channels of the analyzer. A total of 7 in. is traversed in 42 sec after which the profile may immediately be displayed on the CRT readout of the PHA. The device is useful in its present form at accelerators having high beam repetition rates. Plans for its adaptation for use at pulsed accelerators are also discussed.
Instrument for Measuring the Magnetomicrowave Kerr Effect in Semiconductors
Authors: Brodwin Morris E. , Vernon Ronald J.
Published: February 2005

An instrument is described which measures the transport properties of high-conductivity semiconductors. It employs a microwave turnstile junction to determine the complex orthogonal amplitudes of the reflected waves from a magnetized sample. The data are obtained by a double-bridge technique of high sensitivity. Some experimental results on germanium at room temperature are presented.
High Vacuum Motor
Authors: Anastasio Thomas A. , Pokorski Richard G.
Published: February 2005

A contamination-free motor suitable for use in high vacuum is described. Torque, speed, power, and temperature rise data are given.
Liquid Helium Dewar Attachment for an X-Ray Diffractometer
Authors: Stochl Charles A. , Ullman Selma G.
Published: February 2005

A double Dewar attachment has been designed for use with a Norelco x-ray diffractometer. Operating temperatures are the points fixed by the coolant used or by pumping on the inner Dewar, although data can also be taken on a warming cycle. Experiments on Mn3O4 at liquid helium temperature give no evidence for a crystal structure change associated with the ferrimagnetic transition at 43°K.
The Magnetic Field on a Sample in the Electron Microscope
Authors: Luborsky F. E. , Koch E. F.
Published: February 2005

The magnetic fields on a sample in the Philips EM 100B electron microscope have been calculated as a function of objective lens current. Experimental measurements gave values of 6180 Oe/A for the high resolution pole piece and 1860 Oe/A for the diffraction pole pieces. These values are about 20% lower than calculated. This discrepancy is attributed to the uncertainty in the position of the sample. The calculations and measurements are applicable to other electron microscopes.
Jig for Handling and Plating Fine Wires
Authors: Miller James A.
Published: February 2005

A self-contained jig for the spot plating of fine wires, as are employed in hot wire anemometry, is described. The unit consists of a plating bath fixture, Schmitt trigger intervalometer circuit, plating current control and measuring circuit, and power supply, all housed in a 6×4×4 in. instrument cabinet. Setup time is of the order of 5 min and production rates of 30 wires/h may be achieved.
Charging and Acceleration of Microparticles
Authors: Vedder James F.
Published: February 2005

Development work on charging and acceleration of microparticles gives promise of a micrometeoroid simulator capable of producing velocities well into the meteoric range. Velocities up to 7 km/sec have been attained with highly charged micron-size diamond particles with a 70-kV accelerating voltage. Single particles electrodynamically contained in a high vacuum are charged positively by an ion current to give charge-to-mass ratios approaching 400 C/kg. Once charged, the particle is extracted from the containing field and accelerated by a high potential. Preliminary work on charging microparticles of other materials demonstrates the possibility of producing high charge-to-mass ratios on many substances by this technique.
Apparatus for Observing Phase Transitions of Incandescent Materials
Authors: Rupert George N.
Published: February 2005

The temperature vs time curve of a cooling or heating incandescent material is displayed either on a cathode ray oscilloscope or a strip chart recorder. Temperatures at which phase transitions occur are seen as discontinuities in the curves. The temperature-sensing device is a photomultiplier tube. The sample is heated in an eddy current concentrator by induced radio-frequency currents. Light from the sample is divided by a beam splitter between the phototube and an optical pyrometer which is used for temperature calibration. The temperature range displayed for a fixed starting temperature may be reduced by opposing the phototube's output voltage with an adjustable fixed voltage. Typical cooling curves are included.
High Temperature Vacuum Furnace with Metallic Sheet Resistance Elements
Authors: Bacon J. F. , Veltri R. D. , Whittier J. Y.
Published: February 2005

A resistance-heated furnace is described in which samples, 3½ in. long by 2½ in. in diameter, can be heated to 2800°C in an atmosphere of purified inert gas or in a vacuum of 3×10−5 mm Hg at temperature. Furnace heating elements are four flat sheets of tungsten or tantalum and are easily fabricated. Replacement of these elements and full restoration of vacuum (1×10−7 mm Hg for cold furnace) can be accomplished in 1 h.
Scanning Single-Crystal Multichannel X-Ray Spectrometer
Authors: Spielberg N. , Ladell J.
Published: February 2005

The design of a scanning, single-crystal, multichannel x-ray spectrometer for spectrochemical analysis is discussed. This design makes use of two or more sets of reflecting planes in the same crystal, and an individual detector is used for each set of planes. Such an instrument permits the choice of optimum resolution and detection conditions for different spectral regions, without compromising source design and without the introduction of mechanical complexity. It is possible also to scan different portions of the spectrum simultaneously. The features of such an instrument are contrasted with other types of spectrochemical analysis instruments, and some results obtained using such an instrument are described.
Fast Response, Blackbody Furnace for Temperatures up to 3000°K
Authors: Metzler Allen J. , Branstetter J. Robert
Published: February 2005

An inductively heated graphite furnace having a ⅜-in.-diam source of blackbody radiation for pyrometer calibration is described. The furnace is fabricated from simple, easily demountable parts and may be operated at 1800°K for 6 h with only infrequent attention; temperatures to 3000°K may be obtained for shorter periods. Source temperatures are stable and are rapidly attained. The time constant is approximately 2½ min. Special atmospheres are not required for furnace operation since graphite oxidation is minimized through furnace design.
Magnetic Shielding by a Superconducting Cylinder
Authors: Vant-Hull L. L. , Mercereau J. E.
Published: February 2005

Eddy current magnetic shielding by a rotating conductor has been utilized to create a low magnetic field region in the interior of a hollow cylinder. The enhancement of this effect by cooling to the superconducting state has been studied and applied to a superconducting device which easily generates and maintains an extremely low magnetic field region as a laboratory environment. The operation of certain commercial Hall probes at helium temperatures is discussed, and a novel method of measuring bulk resistivities as low as 10−14 Ω-m is suggested.
Beam Profile Monitor for Linear Electron Accelerator
Authors: Martz Dowell E. , Robinson J. Darrell
Published: February 2005

The use of a lead sulfide detector in a device for monitoring the intensity distribution of high energy electron beams from a linear accelerator is described. Experimental measurements of the beam profile for a 6-MeV linear accelerator are presented.
Timing Slow Pulses for Fast Coincidence Measurements
Authors: Strauss Michael G.
Published: February 2005

The circuit described defines accurately the time of arrival of slow pulses. The circuit consists of a compensated delay univibrator generating a signal whose width increases with the input pulse height so that it ends at a time almost independent of the input trigger amplitude. The trailing edge of this signal shifts only 10 nsec when the input is varied from 0.5 to 10 V, and less than 5 nsec when it is varied between 1 and 9 V. The univibrator has been incorporated in a simple fast-slow coincidence circuit. Resolving times (2τ) of 10–30 nsec have been obtained with Co60 and NaI detectors without losing coincident events.
Combined Fluorometer and Double-Beam Spectrophotometer for Reflectance Measurements
Authors: Chance Britton , Legallais Victor , Schoener Brigitte
Published: February 2005

An apparatus suitable for recordings of extracellular oxygen tension in terms of the degree of hemoglobin dissociation and intracellular oxidation-reduction state in terms of the fluorescence level of mitochondrial and cytoplasmic reduced pyridine nucleotide has been constructed. A time sharing sequence permitting light and dark intervals for reflectance fluorometry and two flashes of different wavelengths for reflectance spectrophotometry operates at a repetition frequency of 60 cps. Fixed filters are used in fluorometry for excitation and emission and continuously variable interference filters are used in spectrophotometry.
Choice of Betatron Oscillation Frequencies in a Spiral Sector FFAG Accelerator
Authors: Parzen G. , Morton P.
Published: February 2005

In a fixed-field alternating gradient (FFAG) accelerator, the stability limits and the stability of the machine against field perturbations are very much affected by the choice of the betatron oscillation frequencies, νr and νz. A general criterion for the stability of the accelerator is proposed and, using this criterion, a computer study was carried out on the dependence of the stability on νr and νz. The results of this stability survey seem to indicate a a relatively unique choice of νr and νz to obtain the desired beam intensity.
Some Interactions between Vacuum Gauges
Authors: Worrell Francis T.
Published: February 2005

Interactions have been found between a magnetron gauge and ionization gauges, and between two ionization gauges in close proximity. Evidence is presented to show that the first resulted from positive ions coming from the magnetron gauge. The second interaction was caused by some electrons emitted by one gauge migrating to the other.
Automatic Area Compensator for Constant Stress Cycling
Authors: Feltner C. E. , Jackobs J.
Published: February 2005

A device is described which may be added to an Instron tensile testing machine that allows cycling between stress limits rather than load limits. Changes in specimen length are used as an index of area change. Specimen extension, converted to an electrical signal, is used as a feedback signal which continually adjusts the calibration of the load control chart so that the stress limits are maintained constant throughout a test.
Continuous Ion Source for a Time-of-Flight Mass Spectrometer
Authors: Studier Martin H.
Published: February 2005

With simple modifications improved performance of continuous ion sources in a time of flight mass spectrometer has been obtained. The system was developed for use with heated filament surface ionization sources; however, the advantages of its use with an electron bombardment source seem more significant. With an electron gun operating continuously, a factor of 300 increase in sensitivity over that of the pulsed mode of operation is attained with improved resolution and no increase in the ratio of noise to signal.
Miniature Cryostats: Design and Application to Matrix-Isolation Studies
Authors: White David , Mann D. E.
Published: February 2005

A cryostat of novel design has been constructed and tested for use in matrix-isolation spectroscopy at low temperatures. The refrigeration is supplied by a built-in miniature open-cycle Joule-Thomson liquefier which operates from tanks of high-pressure nitrogen and hydrogen. At 15–16°K, the lowest temperature that can be achieved, the device supplies up to 2 W of refrigeration. The temperature of the cold window on which the matrix is deposited can be varied continuously in the range 15–200°K and readily controlled to ±0.3°K or better. The small, compact, and efficient cryostat design that has been achieved permits great flexibility of coupling to spectrometers and other instruments, and offers many interesting possibilities for a variety of other applications.
Low Frequency Ferromagnetic Resonance Spectrometer
Authors: Lenzo P. V.
Published: February 2005

During an investigation of the effects of anisotropy on the conditions for ferromagnetic resonance at low frequencies in gallium and aluminum substituted YIG, the need arose for a ferromagnetic resonance spectrometer which would operate from about 100 to 1000 Mc. This memorandum describes a marginal oscillator technique which has proved to be both rapid and accurate. The operation is analogous in many respects to the operation of marginal oscillators for nuclear magnetic resonance. The system is similarly characterized by simplicity of equipment, ease of linewidth calibration, and high sensitivity of detection. Linewidths measured from 250 to 1000 Mc on YIG-Ga spheres and disks are given to illustrate the technique.
Instability in the Magnetron Gauge
Authors: Worrell Francis T.
Published: February 2005

Chart records of the ion current in a magnetron gauge of the Redhead design show frequent small downward jumps, and occasional jumps into a different mode of operation. Unstable operation, resulting in a noisy trace, has also been seen during pressure surges in the system. Possible interpretations are mentioned.
High Speed Shutter Mechanism
Authors: Clayton John O.
Published: February 2005

An electromechanical shutter for high speed spectroscopic studies is described. The device utilizes the energy of an electrically exploded metal foil to accelerate a movable slit, and propel it across a fixed slit. The minimum delay time is 19±2 μsec. A 20-μ fixed slit may be opened and closed in 2 μsec by a 20-μ moving slit. No medium is introduced into the optical path to alter spectral distribution.
Bright Field Photography in a Hydrogen Bubble Chamber
Authors: Firth D. R.
Published: February 2005

The performance of bright and dark field optics in a bubble chamber is analyzed. A modification of the usual bright field scheme is proposed, so that very high contrasts may be achieved even in liquid hydrogen. The new scheme can also be used in a single-window chamber. Results of tests of the scheme are presented to support this modification. Photography of bubbles smaller than the resolution limit is discussed; in this case a dark field scheme shows a clear advantage.
Nonsaturating Ionization Chamber for High Intensity External Proton Beam
Authors: Swartz C. E. , Levine G. S. , Carmen R. L.
Published: February 2005

A low density parallel plate ionization chamber which exhibits a linear response to high intensity pulses of 3-GeV protons is described.
Instrument for Continuous High Resolution Measurement of Changes in the Velocity of Ultrasound
Authors: Blume R. J.
Published: February 2005

The frequency of the ``reference'' oscillator in a coherent pulse echo apparatus is phase-locked to the spacing in time of the acoustic echoes. A change in echo spacing is thereby converted to the same fractional change of oscillator frequency, which is measured continuously. Echo spacing changes of 2 to 3 parts in 108 have been resolved at 12 Mc. The gated AFC circuit which controls the reference oscillator derives its error voltage from a phase-detected echo. The error voltage is zero when the echo is in quadrature with the reference. When the echo spacing changes, the AFC shifts the reference frequency to preserve the quadrature condition. The system is largely insensitive to changes of echo amplitude because such changes do not affect the quadrature condition. The attainable accuracy is set mainly by the temperature stability of the sample. There is a detailed discussion of circuitry, performance, and suggested refinements.
Device to Prepare Sodium Chloride of High Reactivity and Surface Area by Vacuum Sublimation
Authors: Adams R. J. , Harrison L. G.
Published: February 2005

This paper describes an apparatus in which sodium chloride can be sublimed in a high vacuum, in amounts in the range 0.1 to 0.5 g, from a quartz tube on to a water-cooled quartz condenser. Without breaking vacuum, the product can be scraped down into a receiver, transferred to a gas adsorption apparatus for surface area measurement, and introduced into a reaction system. The sublimate has a specific surface most commonly between 20 and 36 m2/g. It exhibits unusually high bulk reactivity for isotopic exchange of anions at room temperature.
Spectrometer for Optical Studies of Ultra-Thin Films
Authors: Tweet A. G.
Published: February 2005

An optical spectrometer for study of the optical absorption of monomolecular films spread on water is described. The spectrometer is a multiple-pass instrument, suitable for measurements from approximately 3800 to 8000 Å. It employs a chopper-stabilized monochromatic light source, with a collecting lens and integrating sphere combination to circumvent light shimmering noise. Detection is by means of a photomultiplier tube. Representative results for monomolecular films of chlorophyll a are presented.
Some Interferometer Techniques for Observing Sedimentation
Authors: Beams J. W.
Published: February 2005

Simple and convenient interferometer methods are described for determining the concentration of a substance in solution at various radial distances in an ultracentrifuge cell. These measurements are necessary for the usual molecular weight determinations by the ultracentrifuge method. The methods are particularly well adapted to equilibrium ultracentrifuge determinations of molecular weight and weight-average molecular weights.
Cryostat for Absorption Spectrophotometry
Authors: Sousa John A. , Weinstein Julius
Published: February 2005

A cryostat is described for use in absorption spectrophotometric measurements. With liquid nitrogen as coolant optical cells of variable path length can be maintained at any temperature from −194 to −40°C with a precision of ±0.1°. An optical cell assembly is also described which eliminates the problem of cracking of windows due to rapid temperature changes.
Wide-Range Photographic Photometry
Authors: Dobbins Richard A. , Crocco Luigi , Glassman Irvin
Published: February 2005

Methods of developing a photosensitive film to a high degree of uniformity are demonstrated to be dependent upon the effectiveness of the mixing of the developing solution and the disruption of the formation of a concentration boundary layer during the developing process. Adaptation of the hydraulic brush developing technique and use of film and microphotometer calibration procedures based on a primary standard of measurement made possible the extension of the useful range of commercial films for photometric purposes to a density of over 2.5. These methods permit the use of photographic photometry to make measurements of irradiance varying over a range of 100 to 1 with an accuracy of better than 10% over the entire range.
Image Furnace Radiant Power Control
Authors: Shults Eugene C. , Poplawsky Robert , Bohm Henry V.
Published: February 2005

The design and mechanical details of a rotating-vane radiant power control for use with a vertical, paraboloidal mirror, arc image furnace are given. Optical measurements show this design to give an attenuation of total radiant power at the image point which is approximately a linear function of vane angle, in the vane angle range 0 to 25°. In addition, the radiant flux profile is left essentially unchanged. The loss in maximum total power incurred by introduction of a specific design of the device, and an example of results obtained by its use in crystal growth experiments are also included.
Apparatus for Low-Temperature Tensile Deformation and Simultaneous Measurements of Thermal Properties of Metals
Authors: Erdmann Joachim C. , Jahoda James A.
Published: February 2005

A cryostat has been constructed and is described which permits the tensile deformation of metal specimens under loads up to 150 kg and simultaneous measurements of the thermal and electrical conductivity, thermal diffusivity, and heat of deformation, preferably at temperatures of liquid helium. The apparatus is designed to keep liquid helium for approximately 20 h, which permits the investigation of occurrences requiring high resolution in time, as for example the discontinuous slip at low temperatures. The measurement of the temperature and small temperature differences is achieved through the application of gas thermometers in connection with electronic differential pressure sensors of small dead volume. Automatic recording allows for an accurate observation of thermal transients. The thermal conductivity measurements are based on the Kohlrausch method. Some results which are representative for the application of the apparatus are presented.
Automatic Plotting Device for the Second Derivative of Langmuir Probe Curves
Authors: Branner G. R. , Friar E. M. , Medicus G.
Published: February 2005

An electronic device for automatically plotting the second derivative of probe curves is described in detail. A small sinusoidal signal is superimposed on the dc probe voltage which is swept manually. The second harmonic in the probe current is filtered, amplified by a low noise cascode amplifier, rectified by a phase-true rectifier, and plotted by an X-Y recorder. The components, the critical points in their wiring, and the performance of the system are described. A quantitative comparison is made with related devices. The system described here is somewhat simpler than the competing ones and has the advantage of being applicable to the first and the third derivatives as well.
Two Synthesizer Nuclear Spin Decoupling; INDOR Spectroscopy
Authors: Baker Edward B. , Burd L. W. , Root G. N.
Published: February 2005

A proton-stabilized, frequency-swept, high resolution NMR spectrometer using a frequency synthesizer was described previously by E. B. Baker and L. W. Burd. The addition of a second synthesizer and suitable power amplification allows a variety of nuclear spin decoupling experiments to be carried out with any pair of nuclear species, including INDOR experiments. For INDOR experiments a dispersion signal lock-on provides extra stability for resting on the peak of a very sharp absorption line. A P31 INDOR spectrum of trimethyl phosphite is shown as an example.
Transistorized Electrometer Voltmeter
Authors: Rogers Howard H.
Published: February 2005

A completely transistorized direct current electrometer voltmeter with an input impedance greater than 108 Ω, the accuracy and stability of which is virtually independent of moderate changes in transistor characteristics, has been developed. The high input impedance was attained because transistors with high current gain at very low collector currents are now available.
Experimental Investigation on the Limits of Time Resolution of Scintillation Counters
Authors: Bartl W. , Weinzierl P.
Published: February 2005

The widths of the time-resolution curves of scintillation counters (Philips 56 AVP, plastic, and stilbene scintillators) are measured as a function of the height at which the timing pulse is derived from the rising edge of the scintillation pulse. A very small fraction of this leading edge is used to create a timing signal in a biased two-stage limiter circuit. The arrangement agrees closely with a timing method discussed by Gatti and Svelto and the results are compared to their theoretical predictions.
Variable-Path Magnetic Ion Buncher
Authors: Mobley R. C.
Published: February 2005

Following a previously proposed method for producing short intense monoenergetic ion bunches, a complete variable-path magnetic ion buncher was constructed. Tests in 1958 showed that bunching did occur, but available ion beam intensity and instrumental resolution were too low for detailed measurements at that time. Reconstruction of the available accelerator to give a high current (≥100 μA), well-focused ion beam, and correspondingly high resolution pulse measuring equipment permitted meaningful resumption of testing by late 1960. Bunching performance in accordance with design predictions was then observed. Measurements with ½-MeV protons indicated pulse lengths ≤1 mμsec, peak currents ≥4 mA, and a bunching ratio of ≥40. Average bunched current was >30 μA. Although tested with ½-MeV protons, the design permits operation with protons or deuterons to more than 1 MeV. Bunching is accomplished by deflecting successive portions of a continuous monoenergetic ion beam from an electrostatic accelerator over progressively shorter paths between foci of a multifocusing 103° deflection magnet in a manner such that all ions come together essentially simultaneously at one focal point in high intensity short duration ion pulses. Sinusoidal electrostatic deflection at 8.8 Mc, linearized by cylindrical electrostatic lenses, or through harmonic synthesis, provides the required sweep.
Response of a Large NaI(Tl) Crystal to High Energy Electrons
Authors: Pondrom Lee G. , Strelzoff Alan
Published: February 2005

The resolution function of a 9-in.-diam by 10-in.-long cylindrical NaI(Tl) crystal for incident electrons of 55-, 72-, and 83-MeV energy has been measured. A wedge magnet defined the electron energy. Spark chambers were used on either side of the magnet to insure against spurious scattering of electrons and to estimate the magnet system momentum spread. The most probable pulse height from the crystal varied linearly with electron energy. The pulse-height distribution had a full width at half-maximum of 13.4 +0.3 or −0.7%.
Laser Q-Spoiling Using an Exploding Film
Authors: Masters J. I. , Ward J. , Hartouni E.
Published: February 2005

Q-spoiling is observed when an easily vaporized absorbing film located within the resonant structure of a ruby laser is destroyed by initial stimulated emission. Two features of this new technique are operational simplicity and no severe power handling limitations. The resulting laser output is characterized by a single giant pulse of micro-second duration whose rise time (in the 20- to 40-nsec range) is at least as fast as reported for Q-spoiling by Kerr-cell shutters.
Protection of Superconducting Coils
Authors: Smith P. F.
Published: February 2005

Superconducting magnets of sufficiently high inductance can be damaged by overheating during an accidental transition to the resistive state. Possible protection circuits are analyzed theoretically, and some of the practical consequences of the analysis are summarized.
X-Ray Tube with a Built-In Secondary Target for Exciting K Lines
Authors: Jacobson Bertil , Nordberg Lars
Published: February 2005

A special continuously pumped x-ray tube has been developed for producing high intensities of characteristic K-emission lines. The rotating primary target consists of a gold-plated copper cylinder, which is water-cooled. The conical secondary target is placed inside the primary target and close to it so as to achieve a high output yield. With the tube windows used at present, wavelengths between 0.1 and 0.5 Å can be produced by choosing the appropriate elements for the secondary target. To obtain a high purity of the radiation, the tube voltage should be less than three times the minimum excitation potential for the K radiation in question. The x-ray yield is 108−109 quanta/mA-sec-sr.
Microplasmas in Silicon p-n Junctions as Detectors for Gamma Radiation
Authors: Ruge Ingolf , Keil Günter
Published: February 2005

A counting device of very small dimensions is described which may preferably be used as counter for γ radiation. When operating a silicon diode (alloyed type) in its prebreakdown region, where the breakdown is unstable and giving voltage pulses, the rate of these pulses is a linear function of the incident radiation. In that way the device shows a behavior like a Geiger-Müller tube with large breakdown pulses and small ``deadtime'' (several micro-seconds). Measurements were taken with a 350-C Co60 source in the range of 10 to 104 R/h. As an extrapolation indicates, the device may be used for dose rate measurements up to 107 R/h. Temperature and time stability of the effect are discussed.
Nonlinear Resonance Device for Measuring Uniform Force Fields
Authors: Fitzgerald J. V. , Matusik F. J.
Published: February 2005

Uniform force fields deflect an elastic member when it is rotated at a critical resonant speed equal to the natural frequency divided by the square root of two. At the critical speed the centrifugal force nearly neutralizes the restoring force; consequently, the elastic member becomes responsive to external forces such as gravity, wind, magnetism, or intertial forces which act on it. The dynamic deflection may be hundreds of times the static deflection. The capacity to respond to forces is a feature of the simple model described in this paper. Instrumental applications in accelerometers and gravimeters are possible.
Electromagnetic Flowmeters for Void Fraction Measurement in Two-Phase Metal Flow
Authors: Heineman J. B. , Marchaterre J. F. , Mehta S.
Published: February 2005

The use of electromagnetic flowmeters for measuring the vapor volume fraction in liquid metal two-phase flow is described, and both theory and experimental results from NaK-argon mixtures are presented. The flowmeters must be calibrated before use. The method is applicable to vertical flow channels in which the void fraction is less than 65% and the quality is less than 0.01.
Continuously Oxygenated Tungsten as a Surface Ionization Source
Authors: Haque C. A. , Donaldson E. E.
Published: February 2005

A surface ionization source with a controlled work function has been produced by exposing a polycrystalline tungsten filament to a steady flow of oxygen. The displacement of characteristic method was used to determine its electron work function at different temperatures. The data are supported by the evidence of surface ionization of aluminium.
Simplified System for the Measurement of Fluorescence Lifetimes Using the Stroboscopic Method
Authors: Brown G. C.
Published: February 2005

A simplified and convenient technique for the electronic instrumentation of a stroboscopic system for the measurement of fluorescence lifetimes is described. A modified Tektronix 545 A oscilloscope obtains all the necessary triggers for such a system including a delayed trigger of continuously variable delay. The display of the integrated fluorescence signal is such that the decay time is obtained directly from the calibrated time bases of the oscilloscope.
Stoichiometric Optimizer for Propellant Evaluation Research
Authors: Martin Kenneth J. , Scrogham Kenneth G.
Published: February 2005

An instrument for the stoichiometric optimization of new propellant systems is described. The value of the instrument in substantially reducing the number and cost of computations required for the evaluation of the theoretical performance of propellants is discussed. Several other unique advantages of the instrument are considered.
Hot-Cathode Magnetron Ionization Gauge with an Electron Multiplier Ion Detector for the Measurement of Extreme Ultra-High Vacua
Authors: Lafferty J. M.
Published: February 2005

A hot-cathode magnetron ionization gauge capable of measuring pressures as low as 10−14 Torr has been described in previous publications. The low-pressure limit of this gauge has been extended by the addition of an electron multiplier ion detector. The ions generated in the magnetron gauge are focused onto the first dynode of the multiplier by an electrostatic lens system. The multiplier gain is high enough to permit the use of an ion counting technique for the measurement of very low pressures. The lens system focuses the ions from the gauge into a beam that passes through two limiting apertures before striking the first dynode. This arrangement prevents the soft x rays generated at the magnetron gauge anode from falling directly on the first dynode. The x-ray photoemission from the first dynode has been reduced by a factor of 50 000 below that observed for the magnetron gauge alone. Measurements of sensitivity and x-ray photocurrent indicate that this device should have a linear response down to pressures of 2×10−17 Torr. Ability to measure low pressures with the gauge appears to be limited by the inherent dark current of the multiplier. The gauge may be used to advantage for the measurement of higher pressures by operating at reduced emission current levels to minimize pumping and degassing effects. Photoemission from the first dynode caused by incident light from the magnetron gauge filament has been reduced to values below the x-ray photoemission by the use of a lanthanum hexaboride cathode which operates at only 675°C. This low operating temperature reduces the problem of gas reactions with the filament. Radiation from gas molecules excited by electron impact in the magnetron gauge has been observed in the 10−9 Torr pressure range.
Tilting-Plate Apparatus for the Measurement of Contact Angles in Corrosive Liquids as a Function of Temperature and Pressure
Authors: Muraca Raffael F. , Longwell Anna P. , Burns Eugene A.
Published: February 2005

An apparatus for the measurement of contact angles of corrosive liquids by the tilting-plate method as a function of temperature (−30 to 140°F) and pressure (5 to 100 psia) is described.
Solid-State High-Impedance Voltmeter
Authors: Scheibe Paul O.
Published: February 2005

This report describes an electronic voltmeter which has high input impedance and good thermal stability even though it is constructed entirely with solid-state components. The system is built around a phase-locked oscillator system which inherently has a perfect integrator within its control loop; as a result, the steady-state series error is zero. A discussion of system operation and results obtained from an experimental model of the voltmeter are given. First the system is described and an elementary analysis is given. Experimental results and other possible uses then follow.
Density of Particle Tracks in the Hydrogen Bubble Chamber
Authors: Fabian B. N. , Place R. L. , Riley W. A. , Sims W. H. , Kenney V. P.
Published: February 2005

Measurements have been made of the density of charged-particle tracks in the Brookhaven 20-in. hydrogen bubble chamber as a function of particle velocity and chamber operating conditions. The track density m is given by the function A (Ps)nβ−2 where, at 27°K, A=7.5×10−8 bubbles/cm of track, n=5.4, and Ps is the superheat pressure in psia in the chamber. The pressure superheat dependence Δm/(mΔPs)≅10% per psia; for tracks at different temperatures but with the same pressure superheat, the temperature dependence Δm/(mΔT) is in the range 5–15% per 0.1°K, over the region of normal chamber operation. Macroscopic bubbles grow at the rate 0.21 mm msec−½, until they are quenched by chamber recompression in proportion to their degree of internal energy. The measured track density dependencies are consistent with the view that bubbles originate on stopped secondary electrons produced in close collision processes, where distant collision influence is suppressed by the density effect much more for hydrogen than for the heavier bubble chamber liquids. It is shown that formation and growth of bubbles to critical size may be understood in terms of conventional fluid dynamics provided the expansion is extremely rapid. The secondary electron energies required for bubble formation at 27°K range from 80 to 292 eV depending on the superheat of the chamber.
Fast-Response Thermistor Probes for Temperature Microstructure Studies at Sea
Authors: Cook John C. , Kenyon Kern E.
Published: February 2005

Thermistor probes were built capable of resolving 0.01°C temperature differences in times as short as 0.02 sec, as shown by direct measurement. An approximately linear relation of output signal to temperature, and insensitivity to variations in water velocity require careful choices of circuit resistances and operating power dissipation. Preliminary tests at sea illustrated the importance of eliminating the velocity effect, but also showed that small thermal microstructures could be detected with the new probes.
Apparatus for Tensile Testing to 5400°F in Vacuum
Authors: Taylor Jack L.
Published: February 2005

An apparatus for tensile testing in vacuum to 5400°F is described. A load-elongation curve is plotted during testing of a standard specimen at a selected nominal strain rate between 0.005 and 5.0 in./in./min. The load train design provides that the grips, as well as the specimen, are in the furnace hot zone. The specimen is heated by radiation from an induction-heated susceptor, and its temperature is uniform within the limits of detection of an optical pyrometer.
Transistorized Automatic Data Recording for Cosmic-Ray Detectors
Authors: Richard K. F. , Rao U. R. , Smith W. B.
Published: February 2005

A transistorized automatic data recording system has been developed to provide more reliable instrumentation for the cosmic-ray physicist. The system includes a counting rate integrator, a memory circuit, an electronic clock, and a serial-to-decimal converter. Besides reliability, small size, and low power consumption, the system can give both BCD and decimal output which are automatically punched on IBM cards.