bluuebunny/crossref_metadata_2025 huggingface dataset:
Photon-Counting Spectrometer for Attenuation Measurements in the Soft X-Ray Region
Authors: Bedo D. E. , Tomboulian D. H.
Published: February 2005

A grazing incidence spectrograph, originally designed for photographic registration, is modified for the purpose of making attenuation measurements at selected wavelengths in the 100–300 A region. The modifications over previous procedures include: (1) the introduction of an open multistage Cu-Be electron multiplier for the purpose of comparing intensities by counting photons; (2) the use of the characteristic valence emission bands of the light metals as sources of incident radiation. The photomultiplier is mounted on an arm attached to a spindle whose axis is normal to the base plate and passes through the Rowland circle at the selected wavelength. Defining slits, placed between the grating and entrance window of photomultiplier, limit the spectral band used in irradiating the absorbers. The latter are placed in the diffracted beam at the position of ``least confusion'' and may be rotated independently about the common vertical axis of the spindle, thus varying the angle at which the incident beam strikes the surface of the sample. Various tests indicate that the source intensity and detector sensitivity are adequate for the attainment of satisfactory counting rates. In conjunction with the particular sources referred to, the photon-counting scheme makes it possible to improve materially the precision of existing attenuation measurements.
Transistorized Electronic Analog Multiplier
Authors: Deb S. , Sen J. K.
Published: February 2005

The exponential current-voltage characteristic of the input of a grounded base junction transistor is utilized to construct an analog multiplier. Four-quadrant operation is obtained by using two channels—one with pnp and the other with npn transistors. Design considerations of the various components of the multiplier are discussed. It is shown that the performance of the multiplier—particularly in respect of bandwidth—compares favorably with that of the other types described in the literature.
Method of Measuring and Controlling Evaporation Rates during the Production of Thin Films in Vacuum
Authors: Schwarz Helmut
Published: February 2005

A new method and device will be described for measuring the density in a vapor stream of any material that will be deposited on a suitable substrate in vacuum. For this purpose a ``nude'' ionization gauge is used. The new ionization method differs from others in that it discriminates between the ions of the vapor and those resulting from the background pressure in the vacuum system. The ionization gauge is placed over a hole in the substrate holder; this hole is periodically opened and closed by a shutter vibrating at a low frequency, so that the ion gauge will receive a pulsed vapor stream and detect an alternating ion current superimposed on the direct ion current. A narrow-band amplifier will amplify only the alternating ion current of the frequency of the shutter vibrator. A current integrator may control the total amount of evaporated material. The ionization gauge used in this method can easily measure the total pressure when the filtering system is bypassed. Calibration curves will be shown and a theory given. Sensitivities of the order of 1 A/sec and lower have been obtained.
Coherent Electromagnetic Effects in High Current Particle Accelerators: III. Electromagnetic Coupling Instabilities in a Coasting Beam
Authors: Laslett L. Jackson , Neil V. Kelvin , Sessler Andrew M.
Published: February 2005

The electromagnetic interaction of an intense relativistic coasting beam with itself, including the effect of a nonperfectly conducting vacuum tank, or a quiescent rf cavity, is investigated theoretically. It is shown that the resonances that may occur between harmonics of the particle circulation frequencies and the electromagnetic modes of the cavities can lead to a longitudinal instability of the beam. A criterion for stability of the beam against such longitudinal bunching is obtained as a restriction on the shunt impedance of the rf cavity, or the Q of the vacuum tank. This criterion contains the energy spread and intensity of the coasting beam, as well as the parameters of the accelerator. Numerical examples are given which indicate that, in general, the resonances with the vacuum tank will not cause instabilities, while those with an rf cavity can be prevented from causing instabilities by choosing the shunt impedance at a sufficiently low but still convenient value.
Utilization of Optical Filters in a Scintillation Detector
Authors: Boldt Elihu , Tsipis Costa
Published: February 2005

The detector described consists of a block of plastic scintillator covered by a 4π anticoincidence shield of scintillation plastic sheets. By means of optical filters, the light emitted by the shield is distinguished from the light arising from the core scintillator.
Analysis of ``Immersed'' Thermocouple Error
Authors: Bauerle J. E.
Published: February 2005

The error of an ``immersed'' thermocouple due to heat leaks through the thermocouple wires has been estimated by means of a simple model. The error is shown to decrease exponentially with quantity L1/l1, where L1 is the ``immersion'' depth of the thermocouple and l1 is a characteristic length depending on thermocouple parameters and the mode of heat transfer. It is shown that large errors generally arise if such a thermocouple is used in vacuum. Calculations for specific cases are given.
Optical Servo Control for a Spoon Gauge
Authors: Grotyohann A. G.
Published: February 2005

A pressure gauge constructed of Pyrex glass is described which can be used for vapor pressure measurements of sulfur trioxide. The gauge automatically nulls pressure differentials across a spoon gauge by optically coupling to a servo control. Pressures up to 1 atm can be measured with an accuracy of ±0.5 mm Hg.
Active Filter Element and Its Application to a Fourier Comb
Authors: May F. T. , Dandl R. A.
Published: February 2005

An active bandpass filter has been developed with the desirable feature of wide Q control over the range of frequencies extending to ∼4 kc. The Q has been made as high as 250 with good stability characteristics over this range. The flexibility of the filter has been illustrated by the construction of a filter bank tuned to select Fourier components of a 50-cps periodic wave in a typical noise environment and recombine them with no added relative phase shift and with equal gain to improve the signal-to-noise ratio.
New Technique for Measurement of Microwave Dielectric Constants
Authors: Labuda E. F. , LeCraw R. C.
Published: February 2005

A new technique is described for measuring microwave dielectric constants which overcomes several disadvantages of currently standard methods. Perturbation techniques are used with thin rod samples placed in a TM012 cylindrical cavity in such a manner that all undesirable effects of the ends of the rod are eliminated. A considerable increase in repeatability and ease of measurement is obtained.
Measurement of Electrical Resistivity of Bulk Metals
Authors: Zimmerman J. E.
Published: February 2005

This paper describes a method of measuring the electrical resistivities of metals by ac induction methods, in which the specimen is in bulk form, and no direct contact to it is required. Theoretical expressions are given for a sphere and for an infinite circular cylinder in a uniform applied ac field, and an experimental method is described which is applicable to any shape or applied field configuration.
Victawet and Sodium Metaphosphate as Parting Agents for Electron Microscope Replicas
Authors: Stiegler J. O. , Noggle T. S.
Published: February 2005

It is shown that the active material obtained in the use of Victawet as a parting layer for electron microscope replicas is the inorganic decomposition product sodium metaphosphate (S.M.P.). The results of an investigation of the parting layer characteristics of S.M.P. suggest its use in applications which have previously employed Victawet. Measurements with radioactive tracers indicate that on smooth surfaces reproducible stripping can be realized with parting layers of S.M.P. a few molecular dimensions in thickness. The use of a ribbon filament source with this material is recommended to minimize shadowing effects and thus reduce the thickness of S.M.P. required for successful stripping.
Use of a Tensile Testing Machine for the Determination of Stress and Strain-Optical Coefficients
Authors: Keedy Daniel A. , Volungis Richard J. , Kawai Hiromichi
Published: February 2005

A device which can be used in conjunction with a tensile testing machine to determine the birefringence of a polymer sample as a function of stress, strain, and temperature is described. A chamber is provided so that the sample may be held at a controlled temperature during the measurement.
Design of a Second Harmonic Flux Gate Magnetic Field Gradiometer
Authors: Morris R. M. , Pedersen B. O.
Published: February 2005

An instrument for the measurement of gradients in the earth's magnetic field has been constructed. The gradiometer, of 15-ft base length, is capable of operation for long periods with an error less than 20 γ (5 γ/m). Detectors are of the tuned, second harmonic flux gate type. An automatic ambient-field nulling feature has been introduced to ease the requirement for exact matching of the magnetic characteristics of the gradient detectors.
Capacitor Technique for Measuring the Velocity of a Plane Conducting Surface
Authors: Rice M. H.
Published: February 2005

A capacitor method for measuring the velocity of a plane, conducting surface is described. An advantage of the method is that the signal voltage developed is essentially proportional to the velocity of the surface instead of to the displacement. Consequently, the method is useful in measuring a surface velocity which persists only over a small displacement interval.
Improved Wrede Gauge
Authors: Sharpless Robert A. , Clark K. C. , Young Robert A.
Published: February 2005

An improved Wrede gauge having the following characteristics is described: (a) a response time of ∼1 sec, (b) sensitivity sufficient to detect ∼10−5 mm Hg partial pressure of atoms. This has been accomplished by (a) reducing the trapped volume bounded by the catalytic surface and the effusion diaphragm, and using 130 effusion holes of 0.020 mm diam in plastic films of 6.4×10−3 mm thickness and by (b) balancing the atom-induced pressure difference across the effusion holed as sensed by a capacitative pressure transducer with an electrostatic pressure and recording the square of the voltage between the capacitator elements. Possible sources of error when the device is used to measure the decay of atoms in pulsed afterglows of long duration are discussed.
Arc Lamp Intensity Stabilizer
Authors: Redfield David
Published: February 2005

An instrument has been developed which readily stabilizes to within 0.1% the intensity of a well-defined beam originating in a high pressure xenon arc lamp. Fluctuations due to changes in current or arc position are compensated by a shunt-type regulator connected across the lamp.
Sensitive Triple Modulation Method for Measuring Widths of Microwave Spectral Lines
Authors: Rinehart Edgar A. , Lin Chun C.
Published: February 2005

A method has been devised for the measurement of microwave spectral line widths with high sensitivity. This method consists of a combined source modulation of the microwave power at 2.3 kc and Stark modulation at 100 kc in addition to the slow sawtooth sweep voltage. The use of two rf modulations eliminates the base line which arises from the variation of the klystron power with frequency. The base remains flat for a source modulation amplitude as high as 1 v. The sensitivity is greatly improved over the previous method in which only source modulation is used. It is suggested that the technique of triple modulation may also be used to resolve closely spaced lines.
Formation of Helium Ion Beams by the Injection of a Neutral Helium Beam into a Tandem Accelerator
Authors: Rose P. H. , Wittkower A. B. , Bastide R. P. , Gale A. J.
Published: February 2005

A neutral helium beam, obtained by charge-exchange of fast He+ in helium gas, was injected into a tandem accelerator. The energetic neutral beam drifted to the central terminal where electron stripping occurred in oxygen gas, and the resulting He+ and He++ ions were accelerated from the terminal to ground. These ions were then separated by a 90° analyzing magnet. Approximately 1.6 μa He+ and 1.0 μa He++ were obtained at an injection energy of 450 kev independent of the tandem terminal voltage. Beam intensities have been measured before and after the charge-exchange reactions.
Oxygen Gauge
Authors: Weissbart J. , Ruka R.
Published: February 2005

A high temperature galvanic cell which measures oxygen partial pressure is described. Quantitative measurements in the region 1 to 10−5 atm show a nearly linear relationship between the cell emf and the logarithm of the oxygen pressure at temperatures between 600° and 750°C. The cell can measure oxygen pressures in vacuum systems as well as in flowing gas mixtures.
Device for the Rapid Measurement of Magnetic Anisotropy at Elevated Temperatures
Authors: Zijlstra H.
Published: February 2005

A method for the rapid measurement of magnetic anisotropy is described. The instrument consists of a self-exciting torsion pendulum containing the magnetic sample, which is suspended in a magnetic field in a furnace. The resonance frequency of the pendulum, which depends on the anisotropy energy in a known way, lies between 10 and 100 cps so that the time required for a measurement is shorter than in other methods. The instrument is therefore capable of following a rapidly changing anisotropy, e.g., during the magnetic annealing of the sample. The measurement of the anisotropy of a single crystal of Ticonal G magnet steel during cooling from 900° to 400°C in a magnetic field is described as an example.
Neutron Spectrometer for Producing Pure Monochromatic Beams in the Thermal Region
Authors: Mo/ller H. Bjerrum , Shore F. J. , Sailor V. L.
Published: February 2005

The combination of a Si (111) monochromator and a quartz ``single-crystal'' filter proves effective for the elimination of higher-order contamination from the monochromatic beam of a neutron crystal spectrometer in the energy range from ∼0.02–0.10 ev. This system greatly enhances the usefulness of crystal spectrometers for obtaining cross section data in the thermal range. The properties of the quartz filter have been studied at room temperature and 77°K, and it is shown that the filter is more efficient in this application at room temperature. The higher-order contaminations from Si (111) and NaCl (200) reflections are compared, and it is clearly demonstrated that Si (111) is a superior monochromator in the thermal region.
Ion-Focusing Properties of a Three-Element Quadrupole Lens System
Authors: Enge Harald A.
Published: February 2005

The focusing properties of a three-element quadrupole lens system have been studied, and the results of thicklens calculations are presented in the form of graphs showing the field-strength parameters and magnifications, as functions of object and image distances.
Characteristics of Several Carbon Thermometer-Heaters at Low Temperatures and in Magnetic Fields to 100 Kilogauss
Authors: Hornung E. W. , Lyon D. N.
Published: February 2005

Several carbon thermometers have been prepared with various sizes of carbon particles and new rugged construction methods. The resistance of the thermometers has been measured as a function of temperature from 1.217° to 20.355°K and as a function of magnetic field from 0 to 94 500 gauss. No simple functional relationship holds between resistance and temperature or between resistance and magnetic field. An approximately square dependence of the resistance on the magnetic field holds for some thermometers at small fields, but in no case does this dependence continue at high fields.
Light-Weight Refractometer
Authors: Hay D. R. , Martin H. C. , Turner H. E.
Published: February 2005

This paper describes a seven-pound device that indicates changes in the refractive index of a gas. Because it is capable of detecting refractivity fluctuations that are as small as one part per million, it is useful in studying the irregularities in the refractive index of the troposphere that are important in short radio-wave transmission. The refractometer is self-contained, so that it may be used in controlled or in free ascent through the atmosphere. The device is essentially a high frequency oscillator whose frequency is governed by the capacitance of an air sensing condenser. Special provision is made for reliable operation over the wide range of temperatures normally found in the troposphere.
Directional High Energy Gamma-Ray Counter
Authors: Fazio G. G. , Hafner E. M.
Published: February 2005

A directional Čerenkov counter has been developed for detection of energetic gamma rays from balloons and satellites. It is sensitive to photons whose directions lie within a 10° cone. It is completely insensitive to backward fluxes and almost completely insensitive to charged particles. Several different versions of the system have been constructed, and tested in bremsstrahlung beams. The angular resolution has also been indirectly confirmed by using the device to count cosmic ray muons at sea level.
Microwave Superheterodyne Induction Spectrometer
Authors: Teaney Dale T. , Klein M. P. , Portis A. M.
Published: February 2005

The limits of electron spin resonance detection sensitivity are investigated for absorption and induction spectrometers employing superheterodyne detection. The sensitivity of the conventional bridge absorption spectrometer is found to decrease rapidly below the theoretical limit set by the noise figure of the receiver when klystron power is increased above about 10 mw. This decrease is shown to arise from the extreme frequency dependence of the bridge balance. The bimodal cavity induction spectrometer, which has a highly stable frequency independent balance, shows no departure from the theoretical limit. Flicker noise is found to be produced by the i.f. current in the mixer diodes, but it may be greatly reduced by the use of high i.f. gain. The use of a balanced homodyne detector in place of the conventional second detector is found to reduce the over-all noise figure of the receiver from 13 to 9 db by suppression of carrier noise. The performance of the bridge spectrometer is greatly improved by the homodyne detector which discriminates against frequency noise that enters when the bridge drifts away from balance.
Notes on the Use of a Rubber Membrane Model for Plotting Electron Trajectories
Authors: White A. D. , Perry D. L.
Published: February 2005

Experimentation with a rubber membrane analog has disclosed sources of error in the technique which do not seem to be generally recognized. Means for reducing these errors are discussed and comparisons of observed and computed trajectories for a particular electrode system illustrate the improvement to be expected.
Design and Performance of a Five-Section Nuclear Magnetic Resonance Probe for Aligning Precision Laboratory Electromagnets
Authors: Hillier Stanton B.
Published: February 2005

A special five-section nuclear magnetic resonance probe was developed to facilitate the alignment of precision laboratory electromagnets. A description of the probe and its associated equipment is given along with a discussion of the actual use of the system to obtain detailed information about the magnetic field symmetry of a particular electromagnet. A discussion of accuracies obtainable with the probe is also included.
All-Metal Valve for Ultra-High Vacuum Use
Authors: Thorness R. B. , Nier Alfred O.
Published: February 2005

A demountable solderless all-metal valve suitable for ultra-high vacuum applications is described. A gasketed stainless steel diaphragm transmits the motion. Valves of several sizes have been constructed. One modification is useful for providing a straight path for passage of a beam of particles or light between chambers which it may be necessary to evacuate separately. A pair of valves in a common block may be used to provide a convenient, accurate metering volume. A group of valves machined from a single block may form a complete manifold. The basic mechanism has also been employed for transmitting motion in a high vacuum system as for adjusting a slit.
Simple Laboratory Electromagnets using Aluminum Foil Magnetizing Coils
Authors: Ahern S. A.
Published: February 2005

The construction of iron-cored electromagnets using aluminum foil magnetizing coils is described. A satisfactory procedure for making the coils is discussed in detail. Performance data for a small closed yoke magnet are presented, and the advantages of a system of this kind considered.
Miniature Coils for High Magnetic Field Research
Authors: De Blois R. W.
Published: February 2005

Pulsed magnetic fields greater than 100 koe and of microsecond duration are reported here to be readily producible in millimeter-diameter coils supplied by energy storage units of only several joules capacity. Demonstrative experiments are described which show the magnetic-state transitions of a 20-μg specimen of MnAs near 90 koe, the shift in transition temperature when the specimen and coil are subjected to hydrostatic pressures up to 850 atm, and the reversal of magnetization of a 0.5-μg iron cube from which all reverse nuclei were driven presumably.
An ac Silicon Resistivity Meter
Authors: Allen C. C. , Runyan W. R.
Published: February 2005

A versatile, all transistor silicon 4-point probe resistivity meter incorporating a dc probe bias supply in conjunction with an ac measuring circuit is described. It is direct reading and covers a resistivity range of from 0.01 ohm-cm full scale to 300 ohm-cm full scale. With minor changes the range can be increased to 1000 ohm-cm.
Burning Rate Measurement of Solid Propellants
Authors: Spenadel Lawrence
Published: February 2005

An improved technique for measuring the burning rate of experimental propellants is described. By using a thick ¼-in. i.d. Lucite cylinder to hold the propellant grain, none of the usual inhibition problems are encountered. In addition, since the Lucite does not char on burning, the technique is ideally suited for high speed window bomb photography. Although this technique was developed for the measurement of the burning rate of solid propellants, also liquids, pastes, gels—hygroscopic materials—can all be handled with equal facility.
Four-Specimen Liquid Helium Cryostat for Fluorescence
Authors: Lipsett F. R.
Published: February 2005

A cryostat is described in which the fluorescence spectra of four solid specimens may be obtained by rotating each specimen in turn into focus by means of a tube operated externally. Although designed primarily for obtaining fluorescence spectra in ``reflection,'' the cryostat may also be used to obtain such spectra in ``transmission'' or for the measurement of conventional absorption spectra. Helium is used as a transfer gas and the temperature is determined by a Bourdon pressure gauge used as a gas thermometer. The level of liquid helium in the reservoir is determined with the help of carbon resistors. The specimens are mounted on a small cage which may easily be removed from the cryostat and sealed back into place with an indium gasket. The cryostat is made of metal and is easily demountable.
Resistance Strip Magnetic Electron Multiplier
Authors: Goodrich G. W. , Wiley W. C.
Published: February 2005

A magnetic electron multiplier which utilizes a strip of semiconductor material rather than a conventional multielement dynode structure is described. Especially suitable for use in demountable vacuum systems, it amplifies and detects the electrons which result from bombardment of the cathode with ions, neutral molecules, photons, etc. Gains over 107, and dark currents lower than 0.1 electron per second referred to the cathode have been obtained. The addition of crossed field gates to rapidly direct the output beam to any one of several output anodes is discussed. Theory of operation and results of experimental measurements are reported.
Concentric Bipolar Oxygen Sensitive Microelectrode
Authors: Rice Edward A.
Published: February 2005

The construction of a bipolar oxygen sensitive polarographic microelectrode is described. A platinum wire serves as the active electrode and the reference electrode is a gold plate on an indium-tin base. The electrode has an outside diameter of approximately 70 μ. It is sturdy, electrically stable, highly sensitive to changes in oxygen concentration, and is nontoxic to animal tissue.
Fast Coincidence System Based on a Transistorized Time-to-Amplitude Converter
Authors: Simms P. C.
Published: February 2005

The time-to-amplitude converter is designed for time measurements in the 10−7 to 10−11 sec range. The time resolution of the system is defined as the full width at half maximum of the amplitude distribution produced by the time converter in response to prompt coincidence events. The best time resolution obtained was 4.7×10−10 sec. The time converter and all of the accessory circuits are described.
Sensitivity Error in Frequency Measurements with the Wien Bridge
Authors: Wolff Hanns H.
Published: February 2005

The limitation in the null instrument sensitivity of bridges leads to errors which are due to the uncertainty in the null adjustment. This paper deals with this sensitivity error in Wien frequency bridges. Formulas for the relative error in frequency measurement and for optimum bridge parameters are derived. The influence of deviations from the optimum parameters is shown and discussed. It is shown that, for bridges covering a wide frequency range, certain free parameters should be made adjustable to maintain good sensitivity.
High Temperature, High Vacuum, Diffractometer Attachment
Authors: Intrater J. , Hurwitt S.
Published: February 2005

A high temperature, high vacuum diffractometer camera, which fits the Norelco Wide Range Goniometer, has been designed. The construction details of the camera are presented.
Electronic Determination of the I, G, and I/G Parameters of a Tunnel Diode
Authors: Gneiting C. R.
Published: February 2005

To design a minimum noise figure tunnel diode rf amplifier, the point of minimum I/|Gd| ratio must be known. Also of importance in the design are the diode bias current required at this point of minimum I/|Gd| ratio and the conductance obtained at this bias point. Described in this paper is a scheme whereby X-Y recordings of the I-V, G-V, and I/G-V curves for a tunnel diode can be obtained.
Rotating Bowl for the Production of Uniform Drops
Authors: Brown Edward N.
Published: February 2005

An account is given of a drop generator in the form of a rotating Plexiglas bowl which dispenses large quantities of uniform drops (80–400 μ) with excellent selectivity as to drop diameter.
Electronic Disdrometer
Authors: Clardy D. E. , Tolbert C. W.
Published: February 2005

This paper describes an instrument which will rapidly and continuously measure raindrop-size distributions. A slit of light is used as the sensing element of this disdrometer. Electronic circuits analyze information from a phototube and record the number of drops, within certain size ranges, as they fall through the light slit. The disdrometers of other investigators are reviewed, the characteristics of raindrops are listed, and a raindrop-size distribution recorded by the light slit-phototube disdrometer is presented. The recorded drop-size distribution agrees well with the distribution postulated by Laws and Parsons.
Operation of Cesium-Antimony Phototubes under High Light Level
Authors: Miyake Kiyoshi
Published: February 2005

The fatigue phenomena of vacuum and gas-filled cesium-antimony photocathodes were studied. It is shown that the phototubes can be operated without fatigue at high photocurrent densities, about 90 μa cm−2, by reducing the temperature rise of the cathode due to high illumination and by lowering the anode voltage to be applied.

The photocathodes whose responses ranged from 30 to 60 μa/lu were used to study the changes of their sensitivities in the following experiments: (a) Effect of intense illumination on the sensitivity; (b) variation in the response by heating at elevated temperatures and (c) relation between the change in photoresponse and the positive potential applied to the anode. The results obtained were as follows: In red radiation the thermal effects dominated, and in blue-green radiation an effect on the photosensitivity due to the absorption in the cesium anti-monide film appears. The photoresponse was appreciably reduced when a positive potential above the ionization potential of the gas in the phototubes was applied to the anode. At a very high light level the fatigue phenomena of the cathodes may be caused mainly by the thermal decomposition of cesium antimonides.
Measuring Reactor Neutron Spectra with Threshold Detectors
Authors: Grader Roderick J.
Published: February 2005

The use of threshold detector foils to measure the external neutron spectrum of two reactors is described. The foils employed are Pu239 to measure the total fast flux, U238 for the region above 1.5 Mev, S32 above 2.5 Mev, and Au197 for thermal neutrons. Scintillation counters are used to determine the activity induced in the detectors. The foil-counting system is calibrated by using a Cockcroft-Walton accelerator as a fast neutron source. The results indicate a fission-type spectrum at each reactor.
Fast Response, Low Inertia Vacuum Furnace
Authors: Rachal L. H.
Published: February 2005

A vacuum furnace is described which possesses the following characteristics: (1) low actual thermal mass, allowing rapid temperature change when desired; (2) high effective thermal mass, resulting in precise temperature control; and (3) minimum gas evolution. In the range 150°–950°C, the maximum temperature deviation is approximately 0.1°C; the mean deviation is less than 0.05°C.
Die Forming Doubly Focusing X-Ray Monochromators
Authors: Garrett Harold J. , Lipsitt Harry A.
Published: February 2005

Reliable forming techniques for the preparation of doubly curved LiF x-ray monochromators are described. These techniques are applicable to the formation of doubly focusing one piece monochromating crystals with geometries suited to a wide range of experimental requirements. The resulting dislocation structures were analyzed and utilized in the development of the techniques and are presented as a guide for the preparation of similar focusing crystals.
Total Absorption Lead Glass Čerenkov Counter
Authors: Gatti G. , Giacomelli G. , Love W. A. , Middelkoop W. C. , Yamagata T.
Published: February 2005

A total absorption lead glass Čerenkov counter to be used as γ-ray and electron spectrometer in the 1–10 Gev region is described. The calibration of the counter with monoenergetic electrons shows its response to be linear at least up to 14 Gev. The pulse-height spread improves with increasing energy and it is better than 10% (full width at half-height) for energies above 5 Gev.
CO2-CS2 Geiger Counter
Authors: Crane H. R.
Published: February 2005

Experiments on the mechanism and characteristics of a CO2-CS2 Geiger counter are reported, and circuits and methods of operation which satisfy the special requirements are described. Counter: The active part is 2⅞ in. in diameter and 16 in. long, filled to 1 atm, 95% CO2 and 5% CS2. The cathode is copper and the anode is 0.005-in.-diam Chromel A. Characteristics: The electrons released by an ionizing particle become attached, probably to CS2. The self-quenching action of the counter is excellent, no spurious counts are observed in the absence of electronic quenching. However, a dead time of several milliseconds must be imposed electronically because of the long interval during which the negative ions arrive at the anode. Method: An electronic quench is used which is triggered both by the CO2-CS2 counter and the anticoincidence ring. This serves to impose the required dead time and also to prevent the firing of the CO2-CS2 counter by mesons. Measurements: The plateau was measured to 1900 v above threshold and was found to be level to within 1% from 400 to 1600 v above threshold. The maximum drift time of the negative ions was found to be about 9 msec with a sharp cutoff. Tests with various combinations of gas indicated, but did not prove, that the charge carrier was CS2. The effects of common contaminants were determined. At voltages over 400 above threshold, 1% O2 gave no detectable effect; 0.3% SO2 gave a 2 to 3% reduction in counting rate. Extensive tests of the efficiency were made. Comparisons of the CO2-CS2 filling with an argon-ethane filling gave identical results within the experimental error. No basis was found for supposing that there was any failure of the CO2-CS2 counter to register counts. Reliability: The counter described has been used for C14 dating purposes over a long period of time. There has been no indication that there are variations in counting rate outside those expected on the basis of statistics. The counting rate for ``dead'' CO2 in an iron shield 9 in. thick and after anticoincidence is 8 per min.
Flat Flame Burner for Burning Undiluted Premixed Hydrogen and Fluorine
Authors: Kaye Samuel
Published: February 2005

A burner capable of burning hydrogen and fluorine as premixed reactants at low pressures is described. The construction of the burner was such that the reaction, which is normally considered spontaneous when the gases come in contact, remained suppressed until the lip of the burner was reached. Combustion occurred over an extremely wide range of fuel-oxidant ratios including mixtures rich in fluorine. The flame produced by the burner was flat and symmetrical in shape.
Precision Adiabatic Gamma-Ray Calorimeter using Thermistor Thermometry
Authors: Myers I. T. , Le Blanc W. H. , Fleming D. M.
Published: February 2005

A high precision adiabatic gamma-ray calorimeter is described. For most gamma-ray sources, the calorimeter walls are thick enough to absorb more than 99% of the gamma rays emitted by the source being measured. The standard deviation of the mean in the measurement of a half-curie Co60 source was 0.2%; that of a half-curie radium source was 0.03%.
Effect of Surface Charge in Electrification Measurements
Authors: Ingraham John Charles , Philp Sanborn F.
Published: February 2005

Although the volume charge distribution in a homogeneous substance decays exponentially with time, in general this will not be true of the electric field above a free surface of the substance, due to the formation of surface charge. This must be taken into account in using the electric field or the surface potential as a measure of the electrification, or the decrease of these quantities as a measure of the time constant of a charged sample. The formation of surface charge during charge relaxation is considered in a simple one-dimensional case. The contribution made by surface charge to the surface potential and electric field above the surface may be large if a grounded object, such as a probe or field meter, is near the surface.
Carbon Resistor as a Bolometer for Low Power rf Signals
Authors: Lalevic Bogoljub
Published: February 2005

In a search for very low rf power level bolometers, a carbon disk resistor was used. Cut from an Allen Bradley resistor, such a disk has a sensitivity of 10−10 w at liquid helium temperature. The relative sensitivity of these bolometers exhibits a peculiar behavior in the temperature range between 2.05 and 1.5°K. A plausible but qualitative explanation of the observed behavior can be given by assuming a rectification process between semiconductor and metal i.e. between carbon and copper in this case.
Body-Cross-Section Scan Phantom for the Study of Scintillation Counting Problems in Nuclear Medicine
Authors: Dratz Arthur F. , Coberly James C. , Rohrer Robert H.
Published: February 2005

A body cross-section scan phantom has been designed to study problems involved in the external detection of radioactivity in human organs. It is based upon the use of serial cross-sectional drawings of a particular body area reproduced in metallic paint. A commercial scanning mechanism moves a small electrode over one of the cross sections, and simultaneously moves a small radioactive source through a tank of water. The entire system is aligned in three dimensions relative to the position of a scintillation detector. Each organ area drawn on the cross-section is part of an individual scaling circuit which is activated by the moving electrode. Thus, by scanning the drawing, a summation of the counts due to activity in each of these cross-sectional areas can be automatically registered. The three dimensional response is determined by graphically integrating the data from all the cross sections.
Apparatus for Measuring Adsorption from Solution on Solid Metal Electrodes
Authors: Green Mino , Swinkels Dominic A. J. , Bockris John O'M.
Published: February 2005

A new method for measuring adsorption of organic molecules at the metal/solution interface as a function of potential is presented. The method is designed primarily for studying the adsorption of C14- or S35-labeled organic compounds but can also be used for the adsorption of tagged inorganic species. The main feature of this method is that the large background usually present in this type of experiment has been eliminated. Any metal, which can be obtained in the form of a thin tape of sufficient tensile strength or which can be plated onto a base of sufficient tensile strength, can be investigated by this technique. Some results of the adsorption of thiourea on nickel are given.
Electrochemical Device for Measuring Oxygen
Authors: Neville J. Ryan
Published: February 2005

An electrochemical device for measuring oxygen in gases is described which utilizes a gold indicator electrode and a cadmium reference. Filled with electrolyte and encapsulated with a thin polyethylene membrane, this cell gives a current proportional to the oxygen partial pressure. The unit requires no power or polarizing voltage and can operate unattended for relatively long periods of time. Functional characteristics of the device are discussed in order to suggest potential applications.
Improved Ion Drag Pump
Authors: Jorgenson G. V. , Will E.
Published: February 2005

The measured characteristics (pressure-voltage, current-voltage, and efficiency) of an ion drag pump using razor edge emitters are reported and comparisons made with theory. The advantages of this pump over one using corona point emitters are discussed.
Hall Effect Stroboscope and Noise Discriminator
Authors: Wieder H. H.
Published: February 2005

Construction and performance criteria of a stroboscope, based upon the pulsed operation of Hall effect generators, are presented with special reference to the properties of evaporated thin films of indium antimonide. A high-frequency periodic magnetic field of arbitrary waveshape is converted by the stroboscope into a low-frequency replica of the input signal. This is accomplished by sampling the magnetic field by means of synchronized narrow rectangular current pulses applied to the Hall plate. These current pulses are phase modulated allowing the magnetic field to be scanned point by point thus producing an output voltage which, after integration, is a lower frequency synthesis of the input signal. The advantages of the stroboscope include a linearity between input and output signals to better than 1% and good frequency response between 100 cps and 5 Mc. Hall effect stroboscopes built in this manner also have superior properties as noise discriminators. They will not respond to ambient magnetic fields, except those of the same frequency as the input signal or its harmonics. The advantages of pulsed operation of thin film Hall effect devices in semiconductors with charge carriers having a short relaxation time are shown to be greatly improved sensitivities to small magnetic fields because of the greater peak current densities applicable to the film without any attendant Joule heating.
Multichannel Analyzer Data Analysis by a Least Squares Computer Program
Authors: McWilliams P. , Hall W. S. , Wegner H. E.
Published: February 2005

An analysis method for the output of a multichannel analyzer is described. The data are fitted by a least squares computer program that will determine the area under Gaussian distributions which may be only partially resolved or separated. Mathematical considerations are discussed. Examples of various fits are shown illustrating the capabilities and some of the operational difficulties involved.
Rotating Sample Method for Measuring the Hall Mobility
Authors: Ryan F. M.
Published: February 2005

A simple apparatus is described for measuring Hall mobilities. The sample to be measured is rotated in an external dc magnetic field. The sample thus ``sees'' an ac magnetic field and ac magnetic field Hall techniques may be used. Methods are described for obtaining dc or ac Hall output voltages. Probe misalignment voltages are rejected by this technique as they are in the standard ac magnetic field method. The method yielding a dc Hall voltage enables one to use simple measurement equipment. The method yielding an ac Hall voltage has all of the advantages of the standard ac magnetic field technique yet simplifies the construction of auxiliary equipment and allows one to investigate low mobility samples in the high magnetic field region by using a powerful dc electromagnet. The increased signal level found at the higher magnetic fields might extend the useful range of Hall measurements to lower mobilities than presently measurable. The results of some Hall mobility measurements using a rotating sample are compared with the values obtained by conventional techniques.
Limitations of Accelerator Magnetic Analyzing Systems
Authors: Cohen Bernard L.
Published: February 2005

The relationship between the best resolution obtainable with an accelerator magnetic analyzing system and the rate at which reaction product particles are received at the detector is studied. For cyclotrons and linear accelerators (but not for Van de Graaffs), the beam from the accelerator in all ordinary cases more than fills the phase space volume accepted by the analyzing system; the optimum resolution depends on the phase space density of the accelerator beam to the 1/6.5 power. For Van de Graaffs, the optimum resolution depends on the total accelerator current to the 1/2.5 power. For all typical cases with all accelerators, the best obtainable resolution, for situations where good resolution is needed from the nuclear physics standpoint, is between 3 and 10 kev. A.V.F. cyclotrons should obtain about the same resolutions as Van de Graaffs, but with more difficulties in alignment and stability.
Spark-Gap Switching of a 384-kJ Low Inductance Capacitor Bank
Authors: Goldman L. M. , Pollock H. C. , Reynolds J. A. , Westendorp W. F.
Published: February 2005

A three-electrode spark gap which can handle high energy (96 kJ) has been designed and used with a 384-kJ capacitor bank having an operating range from 30 to 60 kV. The gap jitter time has been reduced to less than 25 nsec. During θ-pinch experiments involving 3000 discharges of the bank, there has been no significant deterioration of the gaps or variation of the electrical characteristics of the system.
Sensitivity of an Ion Pump Leak Detector
Authors: Barrington A. E.
Published: February 2005

An analysis of the parameters governing the performance of a sputter-ion pump leak detector using oxygen or helium as the probe gas is presented. It is shown that the smallest detectable leak is proportional to the stability of the pump current and to the pressure. For optimum performance the pump control unit has to be voltage-stabilized. Expressions for the leak rate and minimum detectable leak in terms of the change of pump current are derived which predict an ultimate capability at least equal to that of conventional mass spectrometer leak detectors. This was confirmed experimentally.
In Vivo Oximeter with Fast Dynamic Response
Authors: Polanyi Michael L. , Hehir Robert M.
Published: February 2005

An in vivo oximeter which uses as a probe a standard cardiac catheter or a Cournand needle is described. The oxygen saturation is obtained from the light intensities at two wavelengths (805 and 660 mμ) diffusely reflected by the unhemolyzed blood. The light is brought to the tip of the catheter and back again to the proximal end by means of glass fibers. Details of the construction of the instrument and experimental results are given.
Modified Ultracentrifuge Synthetic Boundary Centerpiece for Some Polydisperse Systems
Authors: Bartulovich John J.
Published: February 2005

A modified filled-epon synthetic boundary ultracentrifuge cell centerpiece for use with polydisperse solutions, which contain slowly sedimenting solutes with relatively high diffusion coefficients, is described. Because the modifications permit use of the entire length of the solution sector, the period of sedimentation that satisfies Faxén's boundary conditions is increased more than threefold.
Photomultiplier Refrigerator
Authors: Wiggins C. S. , Earley K.
Published: February 2005

A liquid nitrogen refrigerator for a photomultiplier is described. This is of simple construction and involves direct immersion of the photomultiplier tube in the refrigerant. The inherent problems and advantages are discussed and a technique for preventing damage to the tube from thermal shock is described.
Rotating Commutator High-Sensitivity Fluxmeter
Authors: Horst R. L. , Oberg Paul E.
Published: February 2005

A commutator driven by a 1800-rpm motor switches and restores the state of a magnetic sample once each revolution. An overdamped ballistic galvanometer integrates the induced voltage and displays a flux change due to the applied switching pulse. Since there is one flux change per revolution, a large number of revolutions results in a large deflection due to the addition of all the flux changes. This fluxmeter has a sensitivity of 4.61 Mx-turns/cm/min of operating time. With this fluxmeter it is possible to measure magnetization curves and hysteresis loops of very small magnetic samples. The experimental error in the flux measurement is 4%.
Measurement of Thermal Conductivity in a Magnetic Field by the Series Comparative Method
Authors: Morris Robert G. , Hornstra Fred
Published: February 2005

The series comparative method has been used to measure the change of thermal conductivity ΔK of a semiconductor in a magnetic field B. A trial of the method showed the relative change ΔK/K0, where K0 is the zero-field value, was equal to −10% for InSb at 530°K, B=8000 G. The experimental arrangement also allows determination of the dependence on B of the thermoelectric figure of merit Z.
Apparatus for Thermoluminescence Measurements
Authors: Bonfiglioli G. , Brovetto P. , Cortese C.
Published: February 2005

A description is given of an apparatus for thermoluminescence experiments with the following special features: a constant rate of warming with time obtained through a suitable cam; light detection making use of phase rectification to reject noise; a special furnace to record ``glow current curves'' simultaneously. Also, the possibility of ``flattening'' the spectral response of a photomultiplier (between 2000 and 6000 Å) is investigated and the method of calculating a suitable optical filter is outlined. The performance of the apparatus was quite satisfactory, in spite of the rather simple and relatively inexpensive construction of each part.
Rubber Soller Slit Collimators for Neutron Spectrometry
Authors: Caglioti G. , Casali F. Farfaletti
Published: February 2005

In this paper we illustrate the design of rubber Soller slit collimators suitable for work in neutron spectrometry, at present in use at our Laboratory. Experimental tests performed on the collimators proved the rubber lamellae to be very effective as collimating material. The performance of these collimators is that to be expected on the basis of the ``Gaussian approximation'' applied to the attenuation of a neutron beam proceeding through the typical elements of a crystal spectrometer. The simplicity of construction and the performance of these collimators lead us to recommend their use in the field of neutron spectrometry.