bluuebunny/crossref_metadata_2025 huggingface dataset:
High Speed Correlator
Authors: Kindlmann P. J. , Hooper E. B.
Published: February 2004

The real time computation of the correlation function of two signals of up to 2.5 MHz bandwidth at 30 points simultaneously has been achieved to an accuracy of better than 3% of reading ±2% of full scale by a probabilistic computational procedure. An oscilloscope display permits ``live'' observations. The maximum delay between the input signals can take values between 3 μsec and 48 msec, corresponding to delay increments of 0.1 μsec to 1.6 msec, derived from a crystal oscillator. The instrument offers an order of magnitude improvement in bandwidth and a decisive advantage in cost over commercially available units, while retaining compact size (23×48×38 cm). These features, as well as greatly simplified construction, were made possible by the extensive use of integrated circuits. The computational procedure and critical circuitry are described in detail, with briefer treatment given to auxiliary circuits and construction.
New Technique for the Design of an Extreme Ultraviolet Collimator
Authors: McGrath John F.
Published: February 2004

A mechanical collimator is described which eliminates the problem of internal reflection of off-axis radiation and is suitable for use at extreme ultraviolet (XUV) wavelengths (approximately 2 to 1500 Å). The collimator consists of a number of identical multiple-slit arrays, and makes use of the precision of microphotographic fabrication of the slit arrays. A procedure is given for the proper selection of the number and spacing between arrays to prevent cross-channel transmission of off-axis radiation [U. S. Patent No. 3,324,294 (6 June 1967)] and a typical application—wavelength discrimination in a satellite XUV spectrometer—is briefly described.
Multipurpose High Resolution Stage for the Electron Microscope
Authors: Mills J. C. , Moodie A. F.
Published: February 2004

A description is given of the design, construction and performance of an electron microscope stage which combines operation at high resolution with the following facilities: (i) translations transverse to the axis, (ii) translation along the axis over a range sufficient to include the settings for high resolution convergent beam diffraction and magnetic domain observation, (iii) tilting over a range of ±40° about two independent axes, (iv) anticontamination shielding, (v) cooling to approximately −140°C, (vi) heating to approximately 1200°C, and (vii) gas injection. Examples are given of applications in crystal physics, and in particular it is shown that surface structure can be observed directly at the unit cell level.
Production of Uniform Droplets by Means of an Ion Drag Pump
Authors: Hendricks C. D. , Tsui J. B. Y.
Published: February 2004

An ion drag pump generates a low pressure, and, when it is excited by an ac voltage, it can be made to produce a periodic pressure of rather high frequency, when compared with mechanical pumps. The pump can be used to break a cylindrical liquid jet into uniform droplets by launching a wave on the liquid jet. The sizes of the droplets depend on the jet diameter and the frequency of pressure variations. In an experimental system, the supply voltage to the pump was varied from 175 to 2000 V, and a step-up transformer was used to raise the low voltage oscillator output to the high voltage necessary for pump operation. From the relation between the frequency of applied voltage and the frequency of the pressure generated, it was found that the pressure was proportional to the square of the applied voltage. The method described has been used with multiorifice systems to produce multiple streams of synchronized droplets.
Determination of Detonation Wave Velocities
Authors: Steffes F. J. , Bowen J. R.
Published: February 2004

An inexpensive and accurate system to measure wave velocities in detonation tubes has been constructed using piezoelectric type, coaxial transducer pins and solid state, one shot pulse amplifiers. This system uses the conventional manner of generating a symmetrical raster on an oscilloscope, and gives timing precision of better than 0.4% over 2.5 m of observation.
Automatic 2-photon Spectrophotometer
Authors: Staginnus B. , Fröhlich D. , Caps T.
Published: February 2004

An apparatus is described that allows 2-photon spectra to be registered automatically. In this setup the three pulse heights, which are necessary to determine a 2-photon absorption constant, are measured by three analog-to-digital converters. Measurements on ZnO at 5 K are presented as an example.
Beam Current Regulator
Authors: Sheen E. M. , Glass W. A. , Ratcliffe C. A.
Published: February 2004

To improve the average current stability of the positive ion beam from a Van de Graaff type accelerator, a feedback regulator is described that stabilizes the beam current by controlling the portion of the beam removed by a linear-sweep deflection system. The deflection system is linear on both axes to provide a uniform current density over the face of the target. The error signal for the feedback system is derived from a measurement of the target current. Beam currents as small as 1 nA can be regulated to ±0.1% of a preset value.
Automatic Data Plotting Method for Pulsed Experiments
Authors: Harries W. L.
Published: February 2004

A general analogue method of automatically plotting the parametric dependencies of quantities measured in pulsed experiments is described, i.e., if a quantity y is measured vs time in a series of shots, each with a different value of a parameter x, then a plot of y vs x for a series of given times is obtained. An oscilloscope and film are used as readout and memory, and a specific circuit with a frequency response up to 120 kc is given.
High Impedance Langmuir Probes
Authors: Schmidt J. A.
Published: February 2004

The operating characteristics and limitations of high impedance resistive probes are discussed. A new high impedance probe employing capacitive coupling to detect plasma floating potential is described. The advantages of capacitive coupling for increasing the input impedance, reducing the size, and broadening the bandwidth are illustrated. A typical measurement is described which illustrates some of the advantages of the capacitive coupled probe for measurements of plasma properties in a toroidal octupole.
Pulse Timing System for Use with Gamma Rays on Ge(Li) Detectors
Authors: Chase Robert L.
Published: February 2004

A zero crossing technique has been employed to reduce energy-dependent time errors when detecting gamma rays with Ge(Li) detectors. The timing errors associated with pulse shape variation have been evaluated so that circuit parameters might be chosen to minimize those errors. Results of coincidence measurements using a plastic scintillator and a Ge(Li) detector are presented. Typical results using an 8 cc planar detector are 0.8 nsec FWHM at 2.75 MeV, 2.8 nsec FWHM at 511 keV, and 1.5 nsec variation in coincidence peak position from 500 keV to 2.75 MeV.
Dual Frequency Ultrasonic Fluid Flowmeter
Authors: Noble Frank W.
Published: February 2004

Ultrasonic transit time or phase delay flowmeters measure the difference in the time required for an acoustic wave to travel a fixed distance upstream vs downstream. The mechanical or electronic transposition switches introduce noise and limit the frequency response. The system to be described eliminates the need for transposition by the use of two different frequencies propagated continuously in opposite directions. Time resolution of the order of 10−10 sec and frequency response in the kilohertz range are readily attained.
Detection Method for the Normal-to-Superconducting Phase Transition of 10 μ Spheres
Authors: McLachlan D. S. , Feder J.
Published: February 2004

In order to study the superheating and supercooling in type I superconducting spheres, with diameters of the order of 10 μ, a low noise (10−11 V) mutual inductance system has been developed capable of detecting the phase transition of less than 10−9 cc of a type I superconductor.
Apparatus for Continuous Recording of Coercive Force, Maximum Magnetization, and Remanent Magnetization of Ferromagnetic Materials
Authors: English A. T.
Published: February 2004

Continuous recording of 60 Hz B-H loop parameters of ferromagnetic materials, as a function of temperature or time, is made possible by the apparatus described. Maximum magnetization is plotted simultaneously with either coercive force or remanent magnetization. The loop may also be displayed in the usual way using an oscilloscope, if desired. The main advantage of this system lies in the elimination of time-consuming point-by-point data acquisition.
Mechanically Refrigerated Liquid Hydrogen Target
Authors: Brooks J. M. , Otavka M. A.
Published: February 2004

A liquid hydrogen target which incorporates a mechanical refrigerator for cooling rather than using a liquid hydrogen reservoir or cold helium gas has been successfully operated at Argonne National Laboratory. Use of the mechanical refrigerator eliminates the hazard of a large liquid hydrogen inventory in the vicinity of the target. In addition, remote operation is greatly simplified over methods previously used. A commercially available 20.4 K refrigerator, standard gas handling and purifying components, and a specially constructed nonmetallic target flask comprise the mechanical portions of the target system. The target flask requires approximately 20 cc of liquid hydrogen. The system has operated satisfactorily in the external accelerated proton beam of the Zero Gradient Synchrotron.
Measurement of Reynolds Stress by a Single Rotated Hot Wire Anemometer
Authors: Fujita Hajime , Kovasznay Leslie S. G.
Published: February 2004

A convenient method for the measurement of turbulence level and turbulent shearing stress (u2¯,v2¯,uv¯) by a single, continuously rotated, hot wire anemometer is presented. Emphasis is placed on the simplicity in the measuring procedure and on the accuracy in the results obtained. When comparing the results of Reynolds stress measurement in fully developed turbulent pipe flow, good agreement was found with values calculated from the measured pressure drop (skin friction coefficient) along the pipe.
An Isothermal Titration Calorimeter
Authors: Christensen James J. , Johnston H. Dee , Izatt Reed M.
Published: February 2004

A new isothermal titration calorimeter has been designed to facilitate the study of heats of reaction and heats of solution at constant temperature. With this calorimeter, endothermic or exothermic processes can be studied at temperatures at a given point in the calorimeter constant to ±0.0002 C°. Heat effects are compensated by balancing the heat effect of the process taking place in the calorimeter against a variable heater and a constant cooling Peltier device. The calorimeter was tested by measuring the heat of ionization of water and the heat of dilution of aqueous HClO4 solutions. For these systems heats were measured to an accuracy of ±0.02 cal.
Pulsed Field Magnetization Measurements up to 500 kOe
Authors: Allain Y. , de Gunzbourg J. , Krebs J. P. , Miedan-Gros A.
Published: February 2004

In this paper, a pulsed field apparatus consisting of a copper-beryllium helical coil rigidly constrained radially and axially, a 120 kJ capacitor bank, and a magnetization measurement device, is described. With this apparatus magnetization curves up to 500 kOe are commonly obtained at all temperatures between 1.6 and 300 K. Special emphasis is given to the problems involved in the accuracy and the calibration of the magnetization device and experimental results on the critical fields of a few antiferromagnets are shown as examples.
Sinusoidal Molecular Beam Chopper with an Internally Generated Phase Reference Signal
Authors: Schwarz James A. , Madix Robert J.
Published: February 2004

A molecular beam chopper was developed which produces a periodic beam waveform closely approximating a pure sine wave. The chopper generates a reference signal internally for the purpose of phase lag determinations. Its reliable vacuum characteristics make it ideally suited for clean systems.
High Intensity, Low Energy Spread Ion Source for Chemical Accelerators
Authors: Menzinger Michael , Wåhlin Lars
Published: February 2004

A simple plasma ion source which is capable of delivering beams of 1×10−6 A at 200 eV and 0.1–0.2 eV energy spread is described. Gas efficiencies of the order of percents are obtained. This source was found to be very successful in experiments using low energy beams in the electron volt region.
C–Al Parallel Plate Dynode Electron Multiplier
Authors: Kanayama M. , Konno T. , Kiyono S.
Published: February 2004

An easy method of making a parallel plate electron multiplier, which is used for detection of x rays, electron beams, and charged particles, is developed. The multiplier consists of two continuous dynodes, which are prepared by evaporating aluminum onto glass substrates on which carbon has been evaporated in advance. The gain is in the range of 108 to 109, when the applied voltage is 3 kV. Some of the features are quite good linearity of response except for the saturation region, extremely small noise and long lifetime, and ease in handling. It also can be used for pulse counting techniques.
Large Scintillation Counter with Good Energy Resolution
Authors: Gottschalk B.
Published: February 2004

We have constructed a scintillation counter with a useful area 5.1 cm high by 61 cm long, to stop protons up to 160 MeV energy. The energy resolution and the variation of output over the face of the counter have been measured using 160 MeV protons. The percentage peak width is 1.6% (full width at half-maximum) everywhere and the output varies, almost linearly, by 11.5% over the length of the counter and by about 1% over the height.
New Method for Rapid and Accurate Measurement of Decay Time Constants
Authors: Bernalte A. , LePage J.
Published: February 2004

In many experimental situations involving an exponentially decaying process, the time constant of the decay is of fundamental interest. The information is usually contained in an electrical signal, or can be converted to an electrical signal by means of an appropriate transducer. We offer a new method by which the time constant of such a signal can be rapidly and accurately measured. The method was devised in connection with the measurement of resistivities by the eddy current decay technique, but its usefulness in a more general context is also discussed.
Wide-Bandwidth Logarithmic Amplifier for Analyzing Decay Kinetics
Authors: Ahrenkiel R.
Published: February 2004

A logarithmic amplifier is described which converts exponential signals to linear signals. The slope of the latter is inversely proportional to the decay constant or lifetime. This instrument facilitates the measurement of such phenomena as luminescence lifetimes and improves the accuracy of such measurements.
Instrumentation for Analog Differentiator at Low Frequencies
Authors: Chapman R.
Published: February 2004

Sources of errors and noise in analog differentiators are reviewed, together with techniques for minimizing signal distortion. A modified basic operational differentiator is augmented with a linear phase filter. Accurate derivatives are obtained over the range spanning dc to 1 Hz. An inexpensive instrument is presented which reduces noise to a low level while minimizing delay distortion of the signal.
A Semiautomatic Data Collection System Suitable for Infrared Reflectivity Measurements
Authors: Hammer R.
Published: February 2004

A data collection system has been developed to improve the accuracy of ir reflectivity measurements. A programmed sequence controller is used with an integrating digital voltmeter to sample the detector output of a spectrometer and to control the rotation of a sample holder. The digitized output is recorded on punched cards for computer analysis. The use of this system reduces the time required for the collection and reduction of data.
Determination of Accelerator Tune from Perturbed Closed Orbits
Authors: Barton M. Q. , Frankel R. , Month M.
Published: February 2004

A method for determining the ``tune'' of an accelerator is described. The effect of a perturbation on the closed orbit is measured and compared with the theoretical expression for a dipole perturbation by a least squares procedure. This yields the ν value as well as information on the amplitude function and betatron phases.
A Laboratory Apparatus for Demonstrating Principles of Automatic Control
Authors: Brockett Clyde P. , Barham David
Published: February 2004

At leisurely speed the interrelated motions of mostly standard components in this versatile assembly furnish engrossing visual instruction on the role of feedback in a number of well known modes of automatic control. The controller-recorder furnishes a continuous graph of its action, which can be seen developing at all times. A few of of these modes and their graphs are shown.
Comparison of Several Solders for Establishing Mechanical Contacts to Insulating Crystal Platelets at Low Temperatures
Authors: Kreitman M. , Wilkening D.
Published: February 2004

Five solders were compared for their ability to make mechanical contacts to CdS insulating crystal platelets at low temperatures. The percentage of total applications providing satisfactory contact strength, as tested by immersion and violent agitation in liquid nitrogen, was recorded as 95% for pure indium, 92% for silver epoxy, 50% for for silver print, 38% for Indalloy No. 1, and 24% for copper print. The favorable test results for silver epoxy are important in that its use where non-Ohmic contacts are permitted avoids diffusion effects associated with the thermal application of many other solders to insulating crystals.
Millimeter and Nanosecond Resolution of Fast Neutrons from an Intense Plasma Discharge
Authors: Bernstein Melvin J.
Published: February 2004

Polyethylene collimators have been used with fast photomultipliers to spatially resolve the source of 2.45 MeV neutrons in a pulsed, dense, high temperature deuterium plasma. The axial distribution of the neutron source was measured with a spatial resolution of 3 mm and a time resolution of 4 nsec. A time-of-flight technique was developed to measure the average neutron velocity with just one photomultiplier and two widely separated plastic scintillators.
Cryostat-Spectrometer System for Precision Measurement of Lattice Parameters of Irradiated Materials
Authors: Gruber E. E. , Blewitt T. H. , Tesk J. A. , Sharma B. D. , Black R. E.
Published: February 2004

A liquid helium cryostat and associated equipment to measure the lattice parameter of low temperature neutron irradiated materials is described. The cryostat is designed so that the irradiated capsule is a demountable sub-assembly of the helium chamber. The capsule, a small vacuum insulated Dewar, can be irradiated in a liquid helium environment and transferred to the cryostat system for measurement without intermediate warmup above 4.2 K.
An Improved Torsion Pendulum for Measuring Internal Damping
Authors: Schwaneke A. E. , Nash R. W.
Published: February 2004

A new torsion pendulum for measuring internal damping of metals and alloys is described. Improvements over earlier apparatus of this type include (1) a more convenient specimen shape, (2) an electromechanical transducer to measure angular deflections, (3) automatic compensation for eccentric vibrations when operated in the bearingfree mode, and (4) a continuous range of over 500:1 in strain amplitudes with a signal-to-noise ratio of better than 2:1 at a strain of less than 6×10−6. Specific damping capacities ranging from 80% (log decrement, 0.81) to 0.01% (log decrement, 5×10−5) have been measured, and stresses as high as 1970 kg·cm−2 have been used.
Photo-Hall Measurement by an Improved Redfield Method
Authors: Smith G. C.
Published: February 2004

Improvements in electrodes and in instrumentation allow measurement of Hall mobilities as low as 1 cm2/V·sec in photoconducting insulators. Resistance strip electrodes are replaced by parallel wire electrostatic potential dividers. Pulsed photocurrents resulting from electric fields of alternating polarity are averaged in a dual channel ``boxcar.'' This signal is then averaged over multiple field sweeps of alternating polarity by a small digital computer.
A Cold Cathode Soft X-Ray Source
Authors: Solomon J. S. , Baun W. L.
Published: February 2004

A versatile, simple, and inexpensive cold cathode soft x-ray source has been developed. Discharge characteristics are controlled either with an automatic pressure controller (APC) or a fine metering valve. X-ray output with an APC controlling the discharge is shown to have a count rate average standard deviation of ±1% or less for the first hour of operation and no greater than 1.5% for longer periods of time. The cold cathode source operates at mechanical pump vacuum which lends itself to windowless operation. The source may be used for x-ray radiography, luminescence, diffraction, spectroscopy, and as an excitation source for electron spectroscopy.
Calibrated Sensitivity Measurements of Nuclear Magnetic Resonance Spectrometers
Authors: Adler Michael S. , Senturia Stephen D.
Published: February 2004

A definition of sensitivity for NMR spectrometers is proposed. This definition relates sensitivity directly to the minimum detectable steady state NMR absorption χ″. Furthermore, the definition is expressed in a form which makes explicit the sequence of measurements appropriate to its determination. A new solid state calibrator circuit is presented which is both simple and reliable. Its use in performing sensitivity measurements is described.
Flash Calorimeter for Measuring Triplet Yields
Authors: Callis James B. , Gouterman Martin , Danielson J. D. S.
Published: February 2004

A fast, sensitive differential calorimeter is described which permits the observation of heating caused by the relaxation of the lowest triplet states of organic molecules formed by flash excitation. From the ratio of slow to total heating after flash excitation, we calculate Φt, the quantum yield of triplet formation. The detection of the small amounts of heat involved (∼10−5 cal) is accomplished by means of a capacitor microphone transducer which measures volume changes caused by the heating. The response time (∼100 μsec) is determined by the lowest cavity resonance of the sample cell. At room temperature we find for anthrance in ethanol Φt=0.66, while for acridine orange in glyerol Φt=0.23.
An On-Line Data Recording System
Authors: Krag W. , Daggett N. , Davis R. N. , Perkins F.
Published: February 2004

A relatively simple system for recording experimental data from an optical spectrometer has been built and operated. The data are transmitted by telephone at a maximum rate of about four points/sec to a central computing facility where they are recorded on magnetic tape. Several simultaneous users can be accepted. A brief description of the interface between the experiment and the computing facility is presented.
Plasma Parameter Slide Rule
Authors: Nordlund D. R. , Breaux O. P.
Published: February 2004

A slide rule has been developed to facilitate rapid calculation of basic plasma parameters such as electron number density, Debye length, and the number of particles in a Debye sphere. These parameters can be readily calculated within an accuracy of 1.5% for most practical situations involving the application of plasma probes. In addition the slide rule can be used to determine whether Coulomb collisions preclude application of collisionless probe theory in plasma diagnostics.
Pulse Risetimes in Proportional Counters
Authors: Ricker G. R. , Gomes J. J.
Published: February 2004

We present a method of calculating proportional counter pulse shapes for both point and extended ionization tracks. The method is applicable to any counter gas for which the electron drift velocity as a function of the electric field is known. The mobility of the positive ions that are responsible for pulse formation is a parameter of the theory. If we assume there is only one species of positive charge carrier, we can identify it by measuring counter pulse shapes for point ionization tracks and comparing them to calculated pulse shapes. The theory is consistent with measurements of actual pulses in four counter gases: 90% Ar-10% CH4, 90% Ar-10% N2, 90% Kr-10% CO2, and 90% Xe-10% CO2.
Two-Probe Direct Current Measurement of Fused Salt Conductance
Authors: Newman David S. , Stein Roy
Published: February 2004

A simple dc method has been developed for measuring conductance in fused salt systems using inexpensive equipment. The technique is particularly well suited to salts which are able to dissolve their own metal. Cell constants are obtained using a well studied fused salt as the reference material. Fused BiCl3 and fused NaNO3 were studied; the data are in excellent agreement with literature values. Conductance readings were made at or just above the decomposition potential for the melt being studied.
A Subnanosecond Risetime Electro-Optic Shutter for use in a Laser System
Authors: Michon Maurice , Guillet Hubert , Le Goff Denis , Raynaud Sylvain
Published: February 2004

An electro-optic shutter has been realized for use as a component of a Nd glass laser system delivering high peak power pulses. Its main characteristics are (a) switching time less than 1 nsec and (b) dynamic contrast ratio (i.e., peak pulse intensity/intensity preceding the leading edge) higher than 40 dB. This system is capable of delivering optical pulses with half-peak durations of 1 nsec. Two different synchronization schemes have been applied. The first one utilizes a Kerr-cell Q-switched laser. The same voltage step triggers, in turn, the laser and the shutter. The second one utilizes a rotating prism Q-switched laser. A fraction of the laser emission is used to trigger a spark gap which controls the electro-optic shutter.
Multipurpose Phosphoroscopic Instrument for the Study of Phosphorescence, Induction of Fluorescence, and Absorbance Change of Turbid Biological Materials
Authors: Nishimura Mitsuo , Legallais Victor , Mayer Dieter
Published: February 2004

A phosphoroscopic instrument with a high time resolution and flexibility capable of operation in several modes (phosphorescence, fluorescence, light scattering, and absorbance change) was constructed for the study of energy transfer in photosynthesis. Its operation time range is from about 20 μsec to more than 1 sec. Optical, mechanical, and electronic designs of the instrument are shown. Typical recordings obtained with the apparatus operated in several different modes are presented.
Linear Oscillation Viscometer
Authors: White M. S. , Solomons C.
Published: February 2004

The damping of linear oscillations of a thin plate suspended in a fluid from a helical spring is used as a means of measuring viscosity. Though originally designed for use with molten salts at high temperatures and pressures, the apparatus is not limited to such applications; in fact, it offers useful advantages for measurements at ambient pressure and temperature. Density measurements by the Archimedean buoyancy method may be made with the same apparatus by using an immersed body of relatively large volume in place of the plate, under nonoscillatory conditions. The design of the viscometer is presented in detail and its performance is discussed. An important advantage over torsional oscillation devices is the very simple relationship between viscosity and damping of the oscillations.
Optimum Detectors for the NMR Flowmeter
Authors: McCormick William S. , Birkemeier William P.
Published: February 2004

In the general ``time of flight'' flowmeter, the design of the downstream pulse detector is of great importance. In this paper, two optimum pulse detectors are presented which use nuclear magnetic resonance to detect a magnetically tagged segment of flowing fluid. Through the use of space gradients in the H1 and detector fields, these high H1, adiabatic detectors establish and preserve the coherence of the precessing dipoles to obtain maximum detector signal and maximum detector resolution. A discussion of the concepts of detector coherence, bandwidth, resolution, and inhomogeneity effects is presented along with the experimental verification of the new detectors. The paper concludes with a discussion of the complete NMR flowmeter emphasizing the importance of maximum detector signal to noise.
A Versatile, Inert Atmosphere Vacuum Glove Box
Authors: Pack J. G. , Libowitz G. G.
Published: February 2004

A research type, inert atmosphere vacuum glove box of stainless steel construction is described. The apparatus is suitable for a wide range of chemical and metallurgical applications as well as for physical property measurements on reactive samples. The design features a gas purification and recirculation system, automatic moisture monitoring system, and automatic pressure control system. A stereomicroscope with a long working distance to facilitate examination and experimentation on samples within the chamber is mounted over the chamber window. The vacuum glove box was designed to give a routine working environment of less than 1 ppm water and oxygen in argon. Mass spectrometric analysis on random samples of gas from the chamber has confirmed the operational efficiency of the apparatus.
The Use of a Multichannel Scaler in Electron Attachment-Detachment Experiments
Authors: Moruzzi J. L. , Phelps A. V.
Published: February 2004

The use of a multichannel scaler to improve the signal-to-noise ratio of current waveforms obtained from drift tubes is described. Using this technique very rapid improvement in the signal-to-noise ratio can be achieved which allows unstable gases to be readily studied.
Sensitive Hot Wire Level Detector for Cryogenic Liquids
Authors: de la Cruz F. , Bressan O. J.
Published: February 2004

A very simple and highly sensitive ``hot wire'' type level detector to be used with cryogenic liquids is described. The hot filament is made of tungsten wire of about 4 μ diam. The tests on the sensor were made moving the filament in and out of the quiescent surfaces of liquid helium and nitrogen. The results showed 0.006 mm sensitivity in the determination of liquid helium level and 0.002 mm sensitivity in the case of liquid nitrogen level. The sensor is assembled in such a way that it can be used without special precautions during indefinite periods of time. For the case when the full capabilities of the sensor are not necessary, a simple circuit is presented.
Attenuation Correction Factor for Scattering from Cylindrical Targets
Authors: Carpenter John M.
Published: February 2004

The target attenuation correction factor is given for the situation in which the attenuation coefficients differ for incident and scattered radiation. The calculation applies for cylindrical targets, with the scattering plane perpendicular to the cylinder axis. The correction factor is expressed in the form of a series expansion which is appropriate for cases of small attenuation.
Apparatus for Measuring Frequency Derivatives of Dielectric Functions of Surfaces
Authors: Shand M. L.
Published: February 2004

The apparatus described by Jasperson and Schnatterly [Rev. Sci. Instrum. 40, 761 (1969)] was modified to allow direct measurement of the derivatives of the optical dielectric functions of solids with respect to wavelength. The modifications are described and measurements of ∂ε1/∂λ and ∂ε2/∂λ are presented for metallic silver in the wavelength range 3300–4000 Å.
The Generation of Monodisperse Aerosols by Means of a Disintegrated Jet of Liquid
Authors: Ström Lars
Published: February 2004

A thin jet of liquid issuing from a nozzle at a high velocity disintegrates spontaneously into droplets under the action of surface tension. A periodic disturbance of the jet can be used to control the disintegration so as to make all droplets of the same size. A system for generating monodisperse sprays according to the principle outlined above has been designed and built. The jet is modulated by axial vibration of the nozzle, which is mounted at the center of a membrane. The membrane is vibrated by means of electrostrictive elements. Droplets in the diameter range 40–15 μ have been produced at a vibration frequency of 20–300 kHz. The stream of droplets has been analyzed in several ways. A jet of air perpendicular to the droplet stream has proved to be of special value. Several air jets, pulsed in suitable phase relations, are utilized to disperse the stream of droplets and to prevent the droplets from coalescing during the drying phase of the aerosol generation.
Instrumental Effects in a Retarding Field Energy Analyzer
Authors: Wei Pax S. P. , Kuppermann Aron
Published: February 2004

Measurements of the well known electron impact spectra of helium show that a retarding field energy analyzer can give spurious responses; these can be minimized but not eliminated by careful adjustments of the operating potentials. Probable sources of the trouble are discussed.
A Simple Microwave Detector and a p-i-n Reflection Modulator for F Band Application
Authors: Lichtenberger G. J.
Published: February 2004

An inexpensive 120 Gc detector, using a commercially available semiconductor wafer and whisker, is described. The construction of a simple p-i-n reflection modulator is discussed in detail. Characteristics for both devices are given.
A Nanosecond Kerr Magneto-Optic Camera
Authors: Kryder M. H. , Humphrey F. B.
Published: February 2004

A Kerr magneto-optic camera has been constructed which takes 10 nsec exposures of the dynamic magnetization configuration in a magnetic thin film during high speed flux reversal. The photographs obtained have 10 μ resolution and sufficient contrast and brightness to record, in a single exposure, the dynamic state during a 50 nsec or longer flux reversal. The time at which the photograph is taken relative to the application of the switching field is variable from -100 nsec to +10 μsec with a relative time stability at any setting of ±3 nsec. A Q-switched ruby laser is used as a light source. The 10 nsec exposure time is obtained with a Kerr electro-optic shutter. The reversing field has a risetime of 10 nsec, decay time of 20 nsec, variable amplitude (<30 Oe), duration (<10 μsec), and is applied with a stripline. Included in the description of the system are discussions of a blocking oscillator circuit used to drive KU-27 thyratrons with a jitter of less than 1 nsec, an electron multiplier pulse amplifier with a 6 nsec risetime and a 0 to 1.5 kV output into 50 Ω, and a thyratron pulse amplifier with a 10 nsec risetime and a 1.0 to 10 kV output into 50 Ω. The apparatus is particularly suitable for studying high speed flux reversal in that it gives a visual picture of the dynamic state of the magnetization. Examples of sequences of photographs depicting dynamic flux reversal are also included.
Combined Strain Gauge—Quartz Crystal Instrumented Hopkinson Split Bar
Authors: Wasley Richard J. , Hoge Kenneth G. , Cast John C.
Published: February 2004

The Hopkinson split bar, instrumented with both a set of piezoelectric X-cut quartz crystal pressure transducers and a set of strain gauge transducers, was developed to enable investigation of the stress—strain—strain rate behavior in compression of brittle and/or low strength materials. The approach was applied to the study of a brittle, strain rate sensitive, polycrystalline, organic solid, and for purposes of comparison a relatively ductile, highly filled polymer. Comparison and discussion of data from the two materials illustrate the advantage of the technique to obtain valid, more accurate stress and modulus information at strain levels significantly lower than those satisfactorily obtained by using the split bar instrumented with strain gauges alone.
Cell Sizing: A Light Scattering Photometer for Rapid Volume Determination
Authors: Mullaney P. F. , Van Dilla M. A. , Coulter J. R. , Dean P. N.
Published: February 2004

Theory predicts that small angle light scattering by spherical particles of 5 to 20 μ diam is nearly proportional to volume and insensitive to particle refractive index. A flow system photometer with helium-neon laser light source measures the scattering between 0.5 and 2.0° from individual particles at 104 to 105/min. Volume distributions of mammalian cells and plastic microspheres agree with other independent determinations.
An Apparatus for Measuring Stress in Thin Films
Authors: Klokholm E.
Published: February 2004

The average stress in thin films can be obtained by measuring the bending produced in a thin substrate by the action of the film. If the substrate is cantilevered, the deflection of the free end of the substrate is proportional to the average stress in the film. In the device described here, an electronic microbalance is used to measure the deflection of the free end of the cantilevered substrate. Continuous measurement of the film stress, in situ, during film deposition is readily accomplished with this apparatus. The sensitivity is such that continuous measurements of the film stress are possible up to film thicknesses of about 2000 Å. Furthermore, the substrate temperature can be varied from −195 to 350°C. Several examples of film stress in different materials at various substrate temperatures are shown. The limitations and experimental accuracy of this device are discussed.
An Acoustical Thermometer for the Temperature Range 300–700 K
Authors: Goring G. E. , Hardison D. L.
Published: February 2004

A fixed path ultrasonic interferometer, immersed in nitrogen gas at atmospheric pressure and utilizing a quartz crystal oscillating at 600 kHz, serves as a thermometer to define discrete temperatures in the range 300–700 K. The discrete points, occurring at intervals of 15–40°, are defined within ±0.12 and ±0.28 K, respectively, at the lower and upper limits of this range. In order to obtain this performance, it was necessary to measure certain gas phase properties, not available in the literature to sufficiently high precision, and also to utilize a sequence of data points in a least squares sense, thus obtaining lower standard deviations than those resulting from single observations.
The Behavior of Carbon Resistor Thermometers in Magnetic Fields up to 100 kOe in the Pumped Liquid Helium and Hydrogen Temperature Ranges
Authors: Belanger B. C.
Published: February 2004

Previous work has shown that the magnetoresistance of carbon resistor thermometers in applied magnetic fields below 50 kOe for temperatures in the liquid hydrogen and/or liquid helium range exhibits a quadratic dependence on field. This present investigation of the magnetoresistance of 110W, 100 Ω nominal room temperature resistance Allen-Bradley carbon resistors in fields up to 100 kOe reconfirms the fact that the magnetoresistance increases as H2 for low fields, but indicates that a modification of this simple result is necessary for accurate thermometry in fields above 50 kOe. It is shown that the percentage change in resistance due to the application of a magnetic field as a function of temperature and field can be described by the equation 100ΔR/R = CH2T−1.5/ (1+H2H0−2), where R is the resistance in zero field, ΔR the change in resistance when a field H is applied, and T the temperature. C is a constant which depends on the room temperature resistance of the thermometer, and H0 is an adjustable constant. Temperature accuracies of the order of 25 mdeg in an ambient field up to 100 kOe may easily be obtained.
Simple Flow Proportional Detector for Soft X Rays
Authors: Baun William L.
Published: February 2004

A simple small (5 cm long) flow proportional detector for soft x rays is described. The detector is constructed from 3.175 cm hexagonal aluminum bar stock. The detector window is cut in one face of the bar and the ultrathin window seals on that face. O-ring construction is used to allow easy replacement of the 0.00254 cm tungsten wire. The operation of the detector at subatmospheric pressure in a high vacuum chamber is described. Vacuum and gas connections to the detector and to a manometer are shown which allow operation at 100–150 Torr with reference to the chamber pressure. Operating voltage using P-10 gas and counting monochromatic Al Kα at 8.34 Å is 950 V at 150 Torr and 1750 V at 760 Torr.
Production of a 23S Helium Beam
Authors: Fry E. S. , Williams W. L.
Published: February 2004

Beams of metastable helium produced by electron bombardment generally contain atoms in both the 21S and 23S states. It is important in many experiments to distinguish between these states, or at least to know the population ratio. A beam of 23S and ground state helium atoms has been produced by electron bombardment and subsequent resonant quenching of 21S atoms with 21S−21P 2 μ radiation. This radiation mixes the 21S and 21P states, the latter decaying primarily to the 11S state by emission of 584 Å radiation. The quenching has been studied as a function of beam atom velocity. The results indicate that beams of metastable helium containing less than 1% 21S atoms can be produced.
Pulsed Photomultipliers
Authors: De Marco F. , Penco E.
Published: February 2004

Three methods of switching photomultipliers (pulsing of the first dynodes, pulsing of the whole chain, pulsing of the last dynodes) have been tested and compared on the grounds of a good on/off ratio, a low electrical noise, and a short risetime of the gain. In this work we report the measurements and the results of this research and we find that for our needs the best one is the last for which we obtained an on/off ratio of about 300, a risetime of 20 nsec, and a very low electrical noise.
A Metastable Atom Detection System for Ground State Atom Beams
Authors: Winicur Daniel H. , Rodgers Wayne E. , Knuth Eldon L.
Published: February 2004

A metastable atom detection system for ground state atom beams has been developed which differs from preceding systems in that the atom beam (not the electron beam) is modulated, the atom beam is velocity selected, a Bayard-Alpert type exciter is used, and an improved signal enhancement system is employed. An argon beam density five orders of magnitude lower than the background gas density has been measured with a signal-to-noise ratio greater than unity.
Electromagnetically Driven Flux Compression
Authors: Kachilla D. , Herlach F. , Erber T.
Published: February 2004

Electromagnetically driven flux compression (EMC) devices are developed with a view to applications for experiments with megagauss fields, in particular for a study of magnetic bremsstrahlung. Fields of the order of 1.3 MG are reproducibly generated by means of a 27 kJ capacitor bank of uncomplicated design. In order to optimize the EMC configurations, extensive experimental parameter studies have been undertaken by varying the geometrical dimensions, the foil material, the coil design, and the capacitor bank voltage. A comparison is made between EMC and other methods for the generation of megagauss fields.
A Method of Electron Microprobe Signal Enhancement by Pulse Rate Analysis
Authors: Reid L. R. , Smith J. P.
Published: February 2004

This paper describes a means of signal processing specifically designed for use with electron microprobe analyzers. The method of ``pulse rate analysis'' (PRA) can, however, be applied to many areas of data gathering and signal processing where it is desired to suppress randomly distributed background noise pulses. A variable rate control allows selection of the incoming pulse rate required to produce an output signal at the display unit. The pulse rate range has been optimized for microprobe work and covers a PRF of 10 Hz to 40 kHz. A binary scaling arrangement extends this range by a factor of 2 or 4 while providing an S-fold interval distribution. Improvement of up to 50:1 has been observed in the apparent signal-to-noise (S/N) ratio.
A Highly Sensitive Dynamic Bomb Calorimeter
Authors: Hajiev Saleh N.
Published: February 2004

A dynamic bomb calorimeter of a novel type has been developed for the purpose of thermochemical investigations of organometallic and inorganic compounds using the most advanced methods. The calorimeter combines the operating principles of the two existing types of calorimeters (liquid and massive) and enables to combine the advantages and to eliminate disadvantages of the two types. In addition, it is best suited to the requirements of calorimetric theory.
Improved Design Liquid Helium Temperature Regulator Using Operational Amplifier Circuits
Authors: Rochlin G. I.
Published: February 2004

We describe a liquid helium temperature regulator of unusually simple design, operation, and construction utilizing miniature solid state operational amplifiers. The combination of a unique saturating amplifier and an analog multiplier type of cross-correlation phase detection circuit eliminates fast risetime signals and switching transients, enabling the regulator to be used in a low noise shielded environment. The circuit is of the conventional ac Wheatstone bridge type using a carbon resistance thermometer for the sensing element and providing a proportional heater feedback of >1 W to the bath. The balanced input circuitry has been optimized for thermometer resistances between 500 Ω and 5 kΩ, and the regulator is capable of detecting a temperature change of 30 μK at a thermometer power dissipation of <3×10−11 W. Regulation of a superfluid 4He bath to better than ±4 μK for periods greater than 30 min has been achieved at a thermometer power of <5×10−9 W, with a response time of 0.1 sec. Owing to the high gain and broad bandwidth of this regulator, it is adaptable to a wide variety of other situations, such as a sample mounted on a copper block outside the bath, without encountering the usual problems of excessive power dissipation, instability, and thermal oscillations.
Wall Shift of FEP Teflon in the Hydrogen Maser
Authors: Zitzewitz P. W. , Uzgiris E. E. , Ramsey N. F.
Published: February 2004

The wall shift of the atomic hydrogen maser has been determined by a series of 18 measurements on a variety of storage bulbs coated with FEP Teflon. The result is −24.3 mHz for a 15.25 cm (6 in.) bulb at 30°C. This is about 25% smaller than the previous values. It is most likely that a change in the properties of the Teflon caused the difference, which is far larger than possible measurement errors. The systematic correction due to the entrance stem has been estimated using several independent models. The fractional variation of the wall shift with temperature has been measured in the range 27 to 56°C and found to be (−11.4±0.4)×10−3/deg at 35°C. It is suggested that care be taken in applying the value of the wall shift found by one laboratory to bulbs prepared by different techniques or with different samples of Teflon.
A Feedback Circuit for Generation of rf High Amplitude Traveling Waves
Authors: Buschbeck W. , Nielinger H. , Richter F. , Tuczek H.
Published: February 2004

For the investigation of the interaction between traveling magnetic fields and plasma it is necessary to excite long wave trains with high amplitudes on transmission lines. A special feedback circuit is described which permits generation of these wave trains with a relatively economical power supply. Field amplitudes of 2 kG at 1 MHz can be excited for pulse times of several milliseconds, using a 5 MW pulsed transmitter by reinjecting the output energy of the line at the input. The transient phenomena which depend upon the line losses and on a special method of self-excitation of the transmitter are calculated.
A Low Convergence Electron Gun for Energies above 2 eV
Authors: Harting Erik , Burrows Keith M.
Published: February 2004

An electron gun is described which will provide a current of 0.16 μA at 2 eV, in a beam of convergence half-angle 0.03 rad, 2.5 mm in diameter at the space charge limited waist. At electron energies above 12 eV, the beam current is 2.7 μA and independent of energy.