bluuebunny/crossref_metadata_2025 huggingface dataset:
High Pressure Manganin Gauge with Multiple Integral Calibrants
Authors: Samara G. A. , Giardini A. A.
Published: February 2005

A high pressure Manganin gauge with multiple integral calibrants has been developed. It allows accurate and continuous pressure measurement in the 100-kbar range at both room and elevated temperatures. The gauge is designed for use in piston-cylinder, multianvil, and other relatively large volume pressure apparatus. One modification of the gauge consists of a Manganin coil wound on a threaded insulating sleeve which encloses a core of primary calibrants. Bismuth, thallium, and barium have been used for calibrants because they provide four widely separated fixed points in the 100-kbar range. The principle of the gauge's operation is based on (a) the nearly linear dependence of the resistance of Manganin on pressure, (b) the volume discontinuities accompanying pressure-induced first-order phase transitions in the calibrants, and (c) the appreciable strength and rigidity at high pressure of commonly used solid pressure-transmitting media. The over-all response of the gauge consists of nearly linear segments of increasing resistance vs pressure between well-established fixed points. The extension of the range of the gauge to higher pressures and its use for semiquantitative estimates of unknown volume changes accompanying polymorphic transitions are described.
Assembly and Performance of a Double-Beam Microscope Spectrophotometer from Commercial Instruments
Authors: Duecker Heyman C. , Lippincott Ellis R.
Published: February 2005

A microscope spectrophotometer assembled from commercially available instruments has been used to obtain visible and near-infrared spectra on selected specimen areas as small as 1 μ2. A commercial spectrophotometer is coupled to a research microscope equipped with a photometer tube to which the photodetector of the spectrophotometer is attached. The miscroscope spectrophotometer can be assembled easily, quickly, and in a very compact form with a minimum of machine work. The performance characteristics are discussed, as well as some applications. The instrument was designed for spectral investigations of substances under pressure, but is equally well suited to the study of conventional microscope specimens. The incorporation of cameras and polarizing optics makes the instrument particularly suited to phase studies as well. Applications discussed are the shift of absorption bands with pressure, the determination of the pressure gradient in the diamond high pressure cell, and the determination of the spectra of microsections of stained biological specimens.
Gas Reactor for Hot Stage Transmission Electron Microscopy
Authors: Gallegos E. J.
Published: February 2005

An apparatus is described by which in-microscope gas-specimen reactions are possible without recourse to gas containment or aid of an auxiliary vacuum system. The existing hot stage for the JEM-6A electron microscope in combination with the liquid nitrogen trap normally used with the cooling attachment is converted into a heated stage gas specimen reactor for transmission electron microscopy. The apparatus is described and preliminary results on the controlled oxidation of copper, iron, and nickel metal and the reduction of their oxides are discussed.
Technique for Measuring Burning Rates of Solid Propellants
Authors: Osborn J. R. , Bethel H. E.
Published: February 2005

A technique for measuring the burning rate of solid propellants inside rocket motors is described. The technique consists of embedding wires in a specimen of solid propellant and then casting or bonding the specimen to the propellant in the rocket motor. The wires employed were made of 0.0045-in.-diam lead-antimony which has a low melting point, a low thermal diffusivity, and a moderate electrical resistance. The technique involves measuring the time interval between successive interruptions of the wires caused by the burning surface of the propellant. The distance between these wires is determined from an x-ray picture of the specimen prior to placing it in the rocket motor and prior to burning. Thus, with both the distance burned and the burning time known, the burning rate can be determined. When this technique is properly employed, it does not influence the burning rate, nor does it affect the flow field. Furthermore, it can be employed to study the influence on the burning rate of the port shape of a propellant grain inside a rocket motor, since the small specimen of solid propellant containing the resistance-wire network can be cast into the grain of a solid rocket at any position in the port. This will permit measuring burning rates at selected locations and times in the rocket motor.
Scanning and Measuring Projector
Authors: Davey P. G. , Hulsizer R. I. , Humphrey W. E. , Munson J. H. , Ross R. R. , Schwemin A. J.
Published: February 2005

The Scanning and Measuring Projector (SMP) is a semiautomatic device for making rapid and accurate measurements on bubble chamber or other photographs. The SMP, its human operator, and a general purpose digital computer work together in an integrated system. The operator scans the film and specifies the approximate path of the points to be measured, and the points are accurately digitized by a novel apparatus that sweeps the specified portion of the image across a fixed lattice of reference marks. This paper describes the SMP digitizing mechanism and process, and the configuration of the over-all system. Also discussed are the pattern-recognition and time-sharing aspects of the associated computer program, and its error-correcting capabilities.
Automatic Thin Film Vacuum Deposition System of High Stability
Authors: Brownell R. B. , McLennan W. D. , Ramey R. L. , White E. J.
Published: February 2005

An automatic thin film vacuum deposition system is described which permits films of preselected thickness, in the range of 50 to 1500 Å, to be deposited automatically at selected rates between 0.1 and 10 Å/sec. The long time repeatability of the system lies within ±10 Å of the selected thickness.
Ionization Method of Measuring Contact Potential Differences
Authors: Bewig K. W.
Published: February 2005

A modification of the ionization method of measuring the contact potential difference between two surfaces is described which permits remote separation between the source electrodes and the indicating meter. Elapsed time recording is easily accomplished. The errors resulting from large separation between the electrodes are analyzed.
Spin Decoupler for NMR
Authors: Noggle Joseph H.
Published: February 2005

A homonuclear spin decoupler has been developed which, in conjunction with a Varian HR60 nuclear magnetic resonance spectrometer system, may be used for frequency sweep single or double resonance or for field sweep double resonance.
Instrumentation for Measuring the dc Conductivity of Very High Resistivity Materials
Authors: Dorcas D. S. , Scott R. N.
Published: February 2005

Instrumentation for measuring the dc conductivity of alkali halide crystals, and other high resistivity materials, in the temperature range 20–200°C is described. Conductivity as low as 2×10−18 Ω−1 cm−1 has been measured with an estimated accuracy of 5%. A vibrating reed electrometer is used, together with a special test fixture. The latter has provision for temperature measurement and control and for maintaining the specimen in an inert atmosphere. Electrodes are applied to the specimen with colloidal graphite in alcohol or, preferably, vapor-deposited gold electrodes are used. Contact pressure between the specimen electrodes and the gold-plated electrodes of the fixture is maintained by gravity, the latter electrodes being free to move in a vertical direction.
Magnetic Guide Field Measurements and Corrections in the MURA 50-MeV Electron Accelerator. VI
Authors: Pruett C. H. , Christian R. S. , Del Castillo G. , Haxby R. O. , Mulady J. R. , Otte R. A. , Parzen G. , Wallenmeyer W. A. , Young D. E.
Published: February 2005

Methods of measurement and correction of the magnetic fields of the MURA 50-MeV electron accelerator are described. Measurements of the vertical and horizontal field components were made and the field errors corrected. Correction coils, iron shims, and adjustment of magnet positions were used to produce fields within the required tolerances. Computer methods were used to calculate needed corrections and to evaluate the quality of the corrections achieved.
Electronic Servo for Synchrotron Injection Time Control
Authors: Wang C. P.
Published: February 2005

An electronic servo was developed for injection time control of an electron synchrotron. It consists of a delay time command, an error detector, an integrator, an adder, a variable time delay unit, and a time-to-pulse-height converter. The servo works with electric potential analog and contains no mechanical movable parts except the delay time command Helipot. Timing errors of the controlled system (the thyratron pulsing the synchrotron injector, together with its trigger circuit) are converted into error voltage pulses and applied to the time delay unit for self-correction. The time-height converter is sensitive to better than 1 part in 5000. This and the double-forward-path control introduced make the regulated output extend from 3.5 to 8.5 μsec, with 0 nsec error for steady timing errors in the controlled system and 10 nsec error for random fluctuations. The servo was built with transistors and was temperature compensated. The temperature stability is better than 5 nsec/°C.
Radio-Frequency Oscillator for Heteronuclear Magnetic Double Resonance
Authors: Hopkins Robert C.
Published: February 2005

An amplitude-modulated crystal oscillator to be used in conjunction with a Varian HR60 NMR spectrometer system has been developed for heteronuclear magnetic double resonance. It can be operated at frequencies from 3 to 50 Mc with a stability of about 1 part in 108 over a 5-min interval. The oscillator will transmit a useful rf magnetic field of at least 0.1 G to the NMR probe.
Technique for Measuring Position Dependent Electrical Resistivity
Authors: Johnson Eric W. , Johnson Herbert H.
Published: February 2005

An eddy current method is given for determining electrical resistivity as a function of distance beneath the surface of a cylindrical metal core within a coil. The method is also useful for studying surface phenomena such as the anomalous skin effect, and provides a relative measure of bulk resistivity values on short, thick samples with an accuracy of at least 0.05%. Bulk resistivity values for copper, obtained by this method, agree with known values. An example is presented in which the resistivity data shows that working the surface layers of a high purity copper sample led to an imperfection density 25 times higher at the surface than it was 160 μ beneath the surface.
Ferroelectric Hysteresis Tracer Featuring Compensation and Sample Grounding
Authors: Schubring N. W. , Nolta J. P. , Dork R. A.
Published: February 2005

A simple, bridge-type, compensable hysteresis tracer for ferroelectric measurements is described. Unlike conventional hysteresis circuits, one side of the sample is grounded, facilitating control of external parameters during test. Errors due to capacitance and conductance to ground become conveniently analytic. Initial balance controls uniquely neutralize these and have adequate range to accommodate complex fixtures and/or long cables for remote samples. The linear capacitance and equivalent shunt resistance of a ferroelectric sample can be accurately compensated and the values read directly from calibrated dials. The circuit is used in conjunction with a conventional oscilloscope for displaying the hysteresis loops generated but, in itself, the circuit employs no active components.
Kingdon Cage as a Molecular Beam Detector
Authors: Brooks P. R. , Herschbach D. R.
Published: February 2005

A space-charge detector has been constructed to detect beams of neutral molecules. The detector is a diode within which positive ions created by electron bombardment of the beam partially neutralize the space charge and thus produce an increase in the plate current. Beams of rare gases, hydrocarbons, alkyl iodides, nitrogen, and nitric oxide have been studied, and the detector is found to be suitable for measurements of total collision cross sections. The increase in plate current is proportional to the beam intensity raised to a power near unity. The response varies with the beam material and the electrode geometry, but is quantitative and reproducible for a given detector. The minimum detectable intensity is about 1011 molecules/cm2/sec.
Use of Fast Infrared Emitting Diodes with Semiconductor Detectors
Authors: Amsel G. , Zajde C.
Published: February 2005

The light flash of fast infrared emitting GaAs diodes operated in forward conduction at room temperature has been used to excite particle detectors made in silicon. The 9000-Å photons have a range in silicon of 10 μ and create electron-hole pairs, simulating the absorption of a charged particle. The especially designed GaAs diodes can be pulsed with nanosecond speeds. The risetime and decay time of the light flash is less than 0.5 nsec; the time jitter between the current pulse and the light flash is less than 30 psec. The amplitude spectrum of the flash intensity follows Poisson's law applied to the number of photons emitted. The resulting spread is typically of the order of 10−3. A light flash of 1 nsec equivalent to a 5-MeV particle is easily obtained. Transient and statistical characteristics of various types of detectors are quickly measured with high accuracy. The energy calibration of detectors, the adjustment of zero time in complex setups in coincidence, the stabilization of amplifier chains are possible. The coupling of a GaAs diode to a detector yields a high performance fast current integrator.
Optical Probe Techniques
Authors: Goettelman R. C. , Crosby J. K.
Published: February 2005

The application of fiber optics light guides to optical time-of-arrival measurements in the submicrosecond range is described. Methods are given for fabrication of small diameter guides which may be either rigid or flexible. Argon encapsulation techniques are described which make it possible to generate bright optical signals from flying plate arrivals in vacuum. Examples of applications of the techniques used in conjunction with a rotating mirror streak camera are given and the accuracy obtainable is discussed.
Two-Phase Mercury Plasma Tunnel
Authors: Carswell Allan I.
Published: February 2005

A mercury plasma tunnel for the generation of supersonic low density plasma streams is described. This system uses the two-phase (vapor-liquid) cycle of mercury for generating the flow and can employ either dc or rf excitation of the plasma stream. The tunnel provides continuous, high velocity flow streams without large mechanical pumping facilities. Velocities of the order of Mach 4 have been achieved at pressures down to 10−2 Torr. The system provides supersonic plasma streams with easily controllable parameters over a wide range of operating conditions.
Automatic Gain Control for Photomultiplier Tubes
Authors: Rosenthal Jerome A. , Fiehrer Marcel
Published: February 2005

When using a photomultiplier to scan photographs of bubble chamber tracks or other dark signals on a light background, the output signal one obtains depends strongly on the intensity of the background. In this paper we describe and analyze an automatic gain control circuit that helps to remove this dependency. The circuit is both simple and transistorized. Furthermore, it can adjust its gain within microseconds to a large increase in light background.
Circuit to Measure Decay Rate of a Low Frequency Signal
Authors: Swartz J. C.
Published: February 2005

Transistor plug-in circuits have been combined to deliver an output pulse whenever the ac input wave crests between two reference dc levels. This circuit is used to measure the decrement of freely decaying oscillations at frequencies below 80 cps. For decrements below 10−2 the precision of this circuit is better than ±2%.
High Pressure Microwave Cavity for Use in Magnetic Resonance
Authors: Goodrich R. G. , Everett Glen E. , Lawson A. W.
Published: February 2005

A sapphire cone terminated at the large end with a metallic sample serves simultaneously as a pressure seal and the resonant structure for a 1-cm magnetic resonance spectrometer.
Spark Chamber System for High Energy γ-Ray Detection
Authors: Calvelli C. , Kusstatscher P. , Guerriero L. , Voci C. F. , Waldner F. , Pless I. A. , Rosenson L. , Salandin G. A. , Bulos F. , Lanou R. , Shapiro A.
Published: February 2005

A description of an iron plate spark chamber is described. It covers ¾ of the solid angle about a liquid hydrogen target. The fifty steel plates (750×750×2 mm), separated by 3 mm, furnish a thickness of 5 radiation lengths. The voltage risetime of the plates is less than 10 nsec. The system has been used in a 250 000 picture experiment.
Secondary Emission Monitor as a Linear Accelerator Electron Beam Dose Monitor
Authors: Karzmark C. J.
Published: February 2005

The secondary electron emission monitor (SEM) is useful for monitoring electron beams at high dose rates since it is a vacuum device and free of the saturation problem encountered with ionization chambers. In the SEM, the current associated with secondary electrons ejected from a thin foil is collected and used to monitor the electron beam. A description is given of a SEM unit which exhibits a desirable voltage saturation characteristic and good linearity with beam current. The SEM current is about 0.035 of the transmitted beam current for a single aluminum collecting foil located between adjacent polarizing foils. The SEM is basically a current monitor, but for a scattered electron beam of constant incident energy a unique relationship exists between SEM current and the absorbed dose rate at a specified point in the radiation field. However, if the energy varies by only a few percent, the relationship between SEM current and the dose rate is greatly altered. Errors of 20 to 50% were encountered with a particular linac before the beam energy stability was improved. These errors are primarily due to a variation in scattered electron intensity stemming from the energy dependent nature of the scattering process, but also to the dependence of secondary electron yield on beam energy. The change in dose rate arising from the energy dependent aspect of scattering is similar to that occurring in bremsstrahlung production under appropriate conditions. Over a beam energy range of about 1 to 600 MeV, the variation of yield with beam energy is similar to that for electron stopping power. By improving the energy stability of a particular linear accelerator the variation in dose monitor calibration was reduced to a few percent; an improvement by a factor of about 10. The effects of voltage changes, beam loading, and temperature are discussed. In the accelerator described, the microwave power was recirculated. By servo controlling the phase of the feedback power, an important improvement in energy stability was achieved.
Beam Spread with the Princeton FM Cyclotron
Authors: Funsten H. O. , Roberson N. R. , Lieber A. , Sherr R.
Published: February 2005

Two methods have been employed on the Princeton 18-meV FM cyclotron to increase the duty cycle of the proton beam. In the first method, the dee oscillator was cut off just before normal beam extraction and turned on again about 50 μsec later. A moderate beam spread is produced. In the second method, an auxiliary accelerating electrode, in the form of a ``C'' subtending an azimuthal angle of 70° and encompassing the outer 20% of the radial orbits, was added. It is placed opposite the single dee in the region near the deflector and exit channel. In order to produce a spread beam, the regular beam is allowed to enter the region of the C without rf drive on the C. The remaining acceleration necessary for extraction is accomplished by driving the C with an rf program and turning off the dee oscillator. Several frequency-modulation programs were tried; noise, sinusoidal, sawtooth, and combinations of these. Sawtooth modulation produced best beam spread. The duty factor (as measured by the ratio of pile-up to single counts from elastically scattered protons using a sodium iodide-scintillation counter) was increased by a factor of about 4 to 5 in the first method and 12 to 15 in the second method. The average current was reduced by a factor of three. However pulsed operation of the dee oscillator makes it possible to use a higher peak dee voltage for the same average power, thereby reducing the loss of current due to stochastic extraction.
High Temperature Furnace for Melting Point Determination
Authors: Domagala R. F. , Heckenbach E.
Published: February 2005

This paper describes a device for determining by optical methods the melting points of metals, alloys, oxides, and other materials at temperatures up to at least 3000°C. The furnace is simple in design and requires only vacuum and electrical connections. There is no water cooling and the heating element is a disposable tungsten conical basket purchased from a commercial supplier.
Measurement of Photoemitted Electron Energy Distributions by an ac Method
Authors: Spicer W. E. , Berglund C. N.
Published: February 2005

By means of the ac retarding potential method, the energy distribution of photoemitted electrons can be measured much more rapidly and conveniently than is possible by conventional dc methods. In the ac method, a small (about 20 mV) ac voltage (24 cps) is added to a slowly varying (about 1 V/min) retarding potential and the in-phase ac component of the photoemission signal is measured. For the conventional dc techniques, it is necessary to impose very stringent stability conditions on the light source and measuring equipment. Since, in the ac method, the derivative of the I-V characteristic is taken electronically (to give the energy distribution) and is averaged over many cycles, the stability requirements are relaxed by a large amount and data may be obtained much more quickly and conveniently. With the complete system described, resolutions of about 0.1 eV have been attained and small signal conductances (ΔI/ΔV) smaller than 10−11 mhos have been measured.
Optimum RC Filtering and Integration for Sequential Measurement of dc Signals
Authors: Porteus J. O.
Published: February 2005

An optimization study of conventional RC filters and integrators used in measuring dc signals in the presence of noise and ripple is presented. Mathematical expressions for the variance of measurements made with such systems, used separately and in combination, are derived under the assumption that the signal remains constant over a sampling interval of given duration. Optimum filter time constants and delay times for integration are then obtained from these expressions for practical application. A comparative analysis of optimized systems leads to the conclusion that in many cases the performance of an optimized RC filter is superior to that of an integrator used without filtering. However, an optimum combination of filtering and integration may lead to a substantial gain in precision over that possible in a given time interval, using either an integrator or an RC filter alone.
Gated Integrator for Repetitive Signals
Authors: Reichert Jonathan , Townsend Jonathan
Published: February 2005

A gated integrator, using standard analog computing amplifiers, is described. Because of the placement of the diode gate within the feedback integrating loop, many of the previous requirements of high quality insulation and high input impedance electrometers are eliminated. The ``holding time'' of the integrator is such that, for an ``integrating time'' of 10−4 sec, the time required for a drift of 1% of full-scale (50V output) is at least 17 min. The minimum sampling time is 0.5 μsec. A method for taking data using two such integrators and a calibrated signal is also presented.
Apparatus for Flash Photolysis Kinetic Spectroscopy in the Vacuum Ultraviolet
Authors: Goodfriend P. L. , Woods H. P.
Published: February 2005

A description of an apparatus for flash photolysis kinetic spectroscopy is given. This apparatus allows spectra of transient species to be observed in the vacuum ultraviolet down to the fluorite cutoff and allows photolysis radiation with wavelengths as low as 1650 Å to be utilized.
Apparatus for Nuclear Orientation by Adiabatic Demagnetization
Authors: Hess J. , Greenebaum B. , Pipkin F. M. , Weyhmann W.
Published: February 2005

This paper describes an apparatus for cooling an iron foil containing a radioactive impurity to a temperature in the range of 0.012 to 0.026°K by thermal contact with an adiabatically demagnetized chromium potassium alum salt pill. The purpose of the demagnetization is to orient the nuclei of the radioactive impurity. A superconducting solenoid is used to produce the high magnetic field required to remove the entropy from the chrome alum. The apparatus uses two helium Dewars—a large one which contains the superconducting magnet and a small one which contains the salt pill, the 1°K helium bath, and the radioactive sample. The salt pill is formed by pressing a mixture of chrome alum and Octoil S around 5000 0.076-mm-diam copper wires. The salt is supported by a graphite cylinder and helium exchange gas is used to establish heat contact between the salt and the 1°K helium bath. In one form of the apparatus the chrome alum salt and the sample are surrounded by a copper can which is cooled to 0.1°K by contact with a manganese ammonium sulfate salt pill located in the fringe field of the superconducting magnet. With the chrome alum pill alone, the sample temperature is 0.019 to 0.026°K; with the guarded salt pill the sample temperature is 0.012 to 0.016°K.
Simultaneous Deformation and Internal Friction Measurements
Authors: Baker G. S. , Carpenter S. H.
Published: February 2005

An apparatus is described that will allow simultaneous tensile deformation and internal friction measurements. Kilocycle-frequency internal-friction measurements may be made as a function of strain amplitude between 10−10 and 10−4 strain. Tensile strains as large as several percent are possible with only moderate loss of accuracy in the damping measurements. Vibrations at the higher strain amplitudes affect the yield and flow stresses of the sample.
Scanning Microscope Densitometer
Authors: Hartman A. W.
Published: February 2005

A microdensitometer is described that has the form of an attachment fitting over the ocular tube of a standard microscope. It periodically scans a stationary object which can be viewed at the same time by the eye. The electrical output of the densitometer is displayed on an oscilloscope screen, with linear or logarithmic readout. Maximum resolution is 1 micron using a 20× N.A.0.5 microscope objective. Measurements can be made of photographic films and of electron beam spots on fluorescent screens without modifying the instrument.
Stroboscopic Time-Resolved Spectroscopy
Authors: Bhaumik M. L. , Clark G. L. , Snell J. , Ferder L.
Published: February 2005

An instrument for time-resolved spectroscopy with an effective time resolution capability of 2×10−7 sec has been built using a pulsed photomultiplier and the stroboscopic time resolution technique. Because of the higher voltages allowable in pulsed operation, the photomultiplier gain is found to be increased by more than two orders of magnitude and the dark current is reduced by a factor of about five. Therefore, the apparatus is very useful for analyzing weak fluorescence and absorption spectra of microsecond duration. Fluorescence rise and decay times of fractions of a microsecond have also been measured. The instrument was found to be very suitable for analyzing the fluorescence properties of rare-earth chelate laser materials.
Radio-Frequency Ion Source Producing Vibrationally Excited H3+
Authors: Chambers E. S.
Published: February 2005

H3+ ions gave an abnormally high cross section for dissociation to H2+ and a high secondary-electron yield on copper-beryllium. These ions were produced by a hydrogen ion source which is excited by a radio frequency voltage and is aperture extracted. To produce these ions this source was operated at low pressure and in a high magnetic field. It is assumed that such ions are vibrationally excited. Production of the various ions was studied as a function of source magnet field, rf voltage, and geometry. In addition to H+, H2+, and H3+, H5+ was detected. The secondary-electron yield of H2+ from H3+ on H2 was measured for different source conditions.
Multiple Molecular Beams
Authors: Anderson C. H. , Baker M. , Ramsey N. F.
Published: February 2005

A multiple molecular beam technique is described in which a series of beams are used in parallel in a single apparatus to increase total beam intensity while retaining a high sensitivity to small deflections. The particular arrangement used had a single source slit and multiple collimator and detector slits arranged such that 19 beams transversed the three meter machine, each 0.012 mm wide at the collimator and spaced 0.032 mm apart.
Circular Dichroism Measurements to 185 mμ in a Commercial Recording Spectrophotometer
Authors: Holzwarth G.
Published: February 2005

Two devices are described which permit sensitive circular dichroism measurements to 185 mμ in a Beckman DK-2A recording spectrophotometer. One device consists of a special cell holder which fits into the sample compartment of the spectrophotometer; the other device is an adaptation of the electro-optic technique of Grosjean and Legrand to the DK. Both devices are readily detached from the spectrophotometer.
Chemisorption Detector for Hydrogen
Authors: Eisenstadt Melvin M. , Hoenig Stuart A.
Published: February 2005

A chemisorption detector for hydrogen has been developed. The device depends upon the change in work function of a palladium filament when it is exposed to hydrogen. The detector is effective over the pressure range of 10−5 to 10−8 Torr. The system has been checked for sensitivity to other gases, i.e., O2 and N2; it responds strongly to O2 and weakly to N2.
Helium-Cooled Reference Noise Source in a 4-kMc Waveguide
Authors: Penzias A. A.
Published: February 2005

We describe a 4-kMc waveguide load which radiates an effective noise temperature (approximately 5°K) known to within a small fraction of a degree Kelvin. The absorber is immersed in liquid helium and the temperature distribution along the guide is measured by means of an array of germanium diode thermometers.
Seeded-Gas Plasma for Low Density Wind-Tunnel Use
Authors: Christiansen Walter
Published: February 2005

A low density plasma source has been constructed utilizing thermally ionized cesium seeded into an argon gas stream. The essential component of this system is the heat exchanger which uses graphite as the primary element of construction. A resistance-heated helical element and adiabatic stagnation chamber result in a compact arrangement. Some preliminary measurements of the plasma ion density and electron temperature are reported.
Apparatus for the Collection and Purification of Radon
Authors: Rudolph P. S.
Published: February 2005

A simple manually operated apparatus for the collection and purification of radon is described. This apparatus employs a heated platinum filament to continuously recombine the radiolytically produced electrolytic gas. The water vapor is condensed into the radium flask obviating the replenishment of water in the radium solution. The radon does not pass through any stopcocks. The apparatus described has given ten years of trouble free service.
Response Time Corrections to Data from Detection and Recording Systems
Authors: Stoddart L. Charles , Berger Robert L.
Published: February 2005

Using the method of the Laplace transform, corrections for a thermal detection system consisting of a thermocouple, galvanometer, light beam detector, amplifier, and recorder are worked out for a step function and exponential input function. Knowing the system response the rate constant of the exponential can be solved. Fortran II programs for the IBM 1620 computer were written and are available on request. The results show that such corrections make it possible to use a detection system only three times as fast as the event for visual corrections to 10% and further that this can be reduced to only a 1% error if the data are taken and analyzed by machine. In addition, the method provides a very rapid method of determining system parameter changes on recorded data and could thus furnish a convenient systems operation monitor.
General Computer Method of Analysis of Conduction and Diffusion in Biological Systems with Distributive Sources
Authors: Berger Robert L. , Davids Norman
Published: February 2005

A method of analysis by use of the computer has been developed which permits the physical laws governing conduction, or diffusion, to be expressed in first-order finite form. Solutions are obtained in the one-dimensional case for rectangular, cylindrical, and spherical geometries without the use of transcendental functions or other conventional mathematical iterative methods. The case of the cylindrical calorimeter with concentric insulating and conducting layers of varying chemical properties and with distributive heat sources arising from biochemical reactions at the center is treated in the transient and steady-state case.
PHERMEX—A High-Current Electron Accelerator for Use in Dynamic Radiography
Authors: Boyd T. J. , Rogers B. T. , Tesche F. R. , Venable Douglas
Published: February 2005

A high-current, three-cavity, standing-wave linear electron accelerator (PHERMEX) has been designed and built to produce a pulsed bremsstrahlung beam. This beam was desired for use in flash radiography of explosively driven metal configurations, as an aid in the study of shock-induced hydrodynamic phenomena. An unfocused beam exceeding 70 A for 0.10 or 0.20 μsec is available, at a peak energy of about 20 MeV. A 20 A beam for radiographic use, for the same time intervals and peak energy, is focused directly onto a tungsten target to form a 3 mm diam bremsstrahlung source.
Composition of Noble Gas Ion Beams Produced with a Duoplasmatron
Authors: Braams C. M. , Zieske P. , Kofoid M. J.
Published: February 2005

Beams of noble gas ions produced with a duoplasmatron ion source were magnetically analyzed while the gas pressure in the source was varied. At high pressure the beam consisted primarily of singly charged ions. With decreasing pressure the yield of multiply ionized ions increased and was finally limited by the rising arc voltage which caused overheating of the anode. No measurable amount of He2+ or Ne2+ was detected. In the other gases the following maximum yields were measured for the more highly ionized species: 63% A2+, 54% Kr2+, 16% Kr3+, 24% Xe2+, and 1.2% Xe3+. Traces of molecular ions were detected in all the noble gases studied.
Automatic Controlling-Recording Microbalance System for Torsion-Knudsen Effusion-Recoil Studies
Authors: Wilson Albert E. , Kim Jang H. , Cosgarea Andrew
Published: February 2005

A torsion-Knudsen effusion-recoil apparatus with an automatic controlling and recording microbalance system was devised to determine the atomicity of metallic vapors. A detailed description is given of the apparatus and the calibration procedure. Data are presented in order to evaluate the experimental reliability and precision of the instrument.
New Ultrasonic Liquid Level Gauge
Authors: Kalmus Henry P.
Published: February 2005

A new ultrasonic liquid level gauge without moving parts is described in which two wire helices are employed as acoustic waveguides, transmitting sound energy from the top of the tank to the liquid surface and back. The directional propagation in the receiving wire is controlled by the sense of the helix and synchronous reinforcement of pulse coupling between the wires by the side-by-side juxtaposition of the two helices is achieved, resulting in a high signal-to-noise ratio of the device.
Vacuum Tight Windows with Wide Band Transmission Characteristics
Authors: Vogl T. P. , McIntosh R. O. , Garbuny M.
Published: February 2005

A vacuum tight barium fluoride window with transmission range from 1800 Å to 14 μ is described. The window consists of a barium fluoride disk sealed into a suitably formed fine silver spinning with silver chloride. Evacuated envelopes incorporating this window have been made and kept for months without indication of leakage, based on the performance of photoelectric cathodes in the vacuum space. This technique has been equally successful in sealing lithium fluoride windows. The sealing procedure is fully discussed.
High Precision Gas Volumeter
Authors: Williams R. O.
Published: February 2005

A precision gas volumeter resolving 0.02 cc in a total capacity of 680 cc has been constructed. A servo-motor expands and contracts a metal bellows in response to the amplified signal from a pressure transducer. The position of the bellows is indicated on a counter. The instrument was designed to be used with a liquid-gas calorimeter but it has many other uses. Only minor modifications would be required for use with liquids. The accuracy is apparently limited by the calibration error of 0.1%. The device can also be used as a sensitive pressure gauge, with a resolution of 10−3 mm Hg.
Minimum-Noise Pulse Shaping with New Double Delay-Line Filters in Nuclear Pulse Amplifiers
Authors: Blalock T. V.
Published: February 2005

Three new double delay-line filters for pulse amplifiers were developed to circumvent the poor noise performance of conventional double delay-line filters. The operating principle of the new filters is the alteration of the noise spectrum stored in the delay lines prior to the signal arrival. With one of the new filters, a symmetrical bipolar output pulse was obtained that had a measured noise linewidth of 1.6 keV fwhm Si (189 rms electrons) for 5 pF external capacitance, 4.2 μsec delay-line length and 1.4 μsec RC integrating time-constant. The noise linewidth slope was 0.05 keV/pF.
Apparatus for the Detection of Ultraslow Atomic Motion by Magnetic Resonance Techniques
Authors: Jones G. P. , Douglass D. C. , McCall D. W.
Published: February 2005

A description is given of a nuclear resonance apparatus suitable for carrying out measurements in the rotating frame. A new method of aligning the nuclear magnetization along the rf field H1, which employs a field pulse, is discussed together with an easily constructed transistor field pulse amplifier. The apparatus is suitable for use with solids, being capable of generating an H1 field of 4 G. The over-all recovery time has been kept to about 5 μsec using a thyratron damping circuit. The probe described can be used for measurements in the temperature range −195°C to +150°C. A brief description of alignment procedure together with some illustrative results for camphor are given.
Velocity of Sound Measurements in Liquid Metals
Authors: Hill J. E. , Ruoff A. L.
Published: February 2005

The velocity of sound in liquid metals can be determined to ±0.01% using an ultrasonic pulse echo comparison technique. Several corrections must be taken into account due to thermal expansion effects in the apparatus and an apparent phase shifting to be described. The velocity of sound in liquid indium is presented as determined from this apparatus. Finally, a liquid metal cell of fused quartz is suggested which eliminates the thermal expansion effects and other operational problems of the described liquid metal cell.
Electron Echo Methods in Spin Resonance Spectrometry
Authors: Mims W. B.
Published: February 2005

The application of electron spin echo methods to spectrometry is discussed theoretically and illustrated with experimental examples. A pulsing and detection apparatus with a bandwidth of 8 Mc, constituting a relatively simple addition to a conventional X band cw spectrometer, is described. Computations have been made for the echo waveforms generated in the case where the microwave field intensity is of the same order as or less than the linewidth. The optimization of experimental conditions is considered, and an expression has been derived for the minimum number of spins detectable by the echo method. This is essentially the same as the number detectable by cw spectrometry at the same average power level and in the same time of observation. The general applicability of the method is limited by requirements regarding phase memory in the material studied. It is possible, however, that for some measurements, especially those involving broad lines, the echo method may possess advantages over cw spectrometry because of the fundamental difference in the way in which the resonance signal is obtained.
Apparatus for the Autoignition of Explosives under Various Conditions of Initial Pressure
Authors: Sinclair James E.
Published: February 2005

A new instrument capable of measuring the autoignition times of explosives, propellants, and pyrotechnics under various initial vacuum or pressure conditions up to 7 kg/cm2 is described. The notable features are the versatility of the experimental conditions obtainable and the temperature range available.
Monitored Beam X Ray Absorption Spectrometer
Authors: Panson Armand J. , Kuriyama Masao
Published: February 2005

A monitored beam x ray absorption spectrometer arrangement is described. With this geometry inaccuracies in determining absorption coefficients due to fluctuating source intensity are eliminated. In the spectrometer the incident x ray beam passes first through a monitor counter and then through the absorber specimen to a detector counter. The arrangement was tested experimentally using two commercial mica side-window proportional counters.
Cold Cathodes for Possible Use in 6328 Å Single Mode He-Ne Gas Lasers
Authors: Hochuli U. , Haldemann P.
Published: February 2005

Properly dimensioned aluminum cold cathodes promise single mode 6328 Å He-Ne gas laser lifetimes exceeding 3000 h with total gas volumes of only 50 cm3. These cathodes are simple, rugged, and require only about 0.5 W for an emission current of 5 mA dc. Beryllium cold cathodes may be even better but more time is needed for their evaluation.
150 kOe Liquid Nitrogen Cooled Pulsed Flux-Concentrator Magnet
Authors: Brechna H. , Hill D. A. , Bailey B. M.
Published: February 2005

A 150 kOe flux-concentrator magnet is described, having a 90 cm3 conical bore 7 cm long and of 10.4 cm maximum diameter. The field is held at peak value ±10% fro 30–50 msec per pulse. The flux concentrator is energized by a transformer-rectifier set delivering 600 V at 3800 A for the duration of the pulse; it is cooled by a closed loop of circulating subcooled liquid nitrogen which in turn is cooled external to the magnet by liquid nitrogen boiling at atmospheric pressure.
Mass Spectrometer Source Loading Lock and Isolation Valve
Authors: Munro R. , Ridley R. G.
Published: February 2005

An all metal sliding bar vacuum lock is described employing a new type of vacuum seal involving the deflection of the wall of the lock housing. A pressure of 2×10−7 Torr can be maintained in the main source region of a mass spectrometer during the introduction of solid samples into the source. An isolation valve utilizing a similar principle is also described.
Investigation of a Laser Triggered Spark Gap
Authors: Pendleton Winston K. , Guenther Arthur H.
Published: February 2005

The influence of parameters affecting the laser triggering of a high voltage electrical sphere-sphere gap has been experimentally investigated. Of primary interest was the delay time between arrival of the laser pulse and current flow across the gap. This delay was studied as a function of total laser beam power (0–80 MW); dielectric gas (SF6, N2, air); gas pressure (100–1400 Torr); electrode spacing (0.4–1.5 cm); gap electric field (10–100 kV/cm); and focus point location between two 5 cm diam stainless steel spheres. Delay times less than 10 nsec were observed in SF6 at atmospheric pressure with corresponding low jitter. For the cases studied delay times varied inversely with the electric field, gas pressure, and focus point distance from the anode surface. Above a certain laser beam power the delay time was not a significant function of laser power for the range studied. Applications of laser triggering are discussed with a description of current and future research areas.
Laser Photography of Hypervelocity Projectiles
Authors: Trammell Warren V.
Published: February 2005

A photographic system is described which is capable of taking photographs of hypervelocity projectiles in a free-flight range. The system consists of a Q-switched laser, a simple lens camera, and related triggering circuitry. The film size is 73×95 mm which permits an image-object ratio of two. Typical photographs of in-flight projectiles traveling between 6.4 and 7.1 km/sec are presented.
Apparatus for the Measurement of the Hall Effect in Semiconductors of Low Mobility and High Resistivity
Authors: Hermann A. M. , Ham J. S.
Published: February 2005

An apparatus for the measurement of the Hall effect in materials of low mobility and high resistivity is described. An ac technique is used: The sample is rotated in a static magnetic field at 20 cps, an electric field is applied at 13⅓ cps, and the Hall signal, preamplified by field-effect transistors mounted on the rotating shaft near the sample, is synchronously detected at 33⅓ cps. Hall mobilities as small as 0.2 cm2/Vsec in samples of resistance up to 109 Ω can be measured with negligible detector loading. A discussion is also given of the fundamental limitations of Hall effect measuring equipment. Typical Hall mobilities in iodine single crystals and in iodine complexed 1:1 with poly-n-vinyl carbazole are reported.
Thin Foil Heat Meter
Authors: Hager Nathaniel E.
Published: February 2005

A thin wafer of low density, compression-resistant thermal insulation is enclosed between two 0.00064 cm foils of edge-welded copper-constantan thermocouple material. The foils are connected to form a low-impedance differential thermocouple system which produces an emf proportional to the temperature difference between wafer faces. Under steady-state conditions, the heat flux normal to the wafer is related to the observed emf by a calibration factor computed from known properties of insulation and foil. Experimental calibration confirms to within 5% the correctness of the computed factor. Both theory and experiment show that a meter having a wafer thickness of the order of 0.0025 cm produces steady readings within 0.4 sec after an abrupt change in heat flux. The thermal resistance of the meter is ordinarily negligible compared with that of the air film adjacent to solid surfaces. Normal environmental heat fluxes produce signals read with good precision on modern microvoltmeters.
Reference Tables for Platinum-40% Rhodium/Platinum-20% Rhodium Thermocouples
Authors: Bedford R. E.
Published: February 2005

Reference tables covering the temperature range 0–1880°C have been established for platinum-40% rhodium/platinum-20% rhodium thermocouples. They are based on calibrations in air of ten thermocouples from four wire lots. These calibrations included freezing point determinations of zinc, antimony, silver, and gold; melting point determinations of palladium and platinum by the wire method; comparisons with standard platinum-10% rhodium/platinum and platinum-20% rhodium/platinum-5% rhodium thermocouples from 0 to 1750°C; and intercomparisons of the test thermocouples from 0 to 1850°C. The accuracy and stability to be expected from this thermocouple combination is discussed. More detailed tables than those presented here are available as APH Report No. 1292.