bluuebunny/crossref_metadata_2025 huggingface dataset:
Goniometer for Partial Pole Figure Determination on Cylindrical Specimens
Authors: van Someren L. , Sprenkle E.
Published: February 2004

This paper describes an accessory designed for a Philips-Norelco x-ray diffractometer to allow the investigation of the spatial distribution of any particular crystal plane found near the surface of cylindrical specimens. The device holds the specimen in the exact position required for measurement, and allows it to be moved through an arc of ±33°, while it is rotated about its own cylinder axis. Adjustments are provided for examining different regions of the specimen. It will accommodate specimens between 2.8 and 8.1 cm long and between 1.0 and 2.5 cm in diameter. Results obtained from the same thin foil specimen in cylindrical and planar form show reasonable agreement.
Generation and Switching of Magnetic Energies in the Megajoule Range by Explosive Systems
Authors: Knoepfel H. , Kroegler H. , Luppi R. , van Montfoort J.
Published: February 2004

The results of an extensive experimental program on explosive-driven magnetic flux compression devices of the ``bellows'' type are described and discussed. These generators, in which explosively propelled conducting plates compress the magnetic flux into the final load, have been tested in single and multistage systems, generating axial fields of up to 700 kOe in volumes of the order of liters with a corresponding maximum magnetic energy in the load of 2 MJ. Bellows generators are best suited to match a single-turn solenoid as the inductive load and it is shown that in particular cases a combination of these generators with the recently described helical ones is of great interest. Particular attention is paid to a switching system (including a closing and opening switch) with which it is possible to transfer the magnetic energy accumulated in the generators into an appropriate inductive load within 10 μsec and less. A simple analysis and the experimental results show that this is feasible, although magnetic flux and energy losses are inevitable, particularly if high switch performances are required (e.g., opening time <5 μsec, initial current rise >1 MA/μsec).
Differentially Pumped, Large Angle Coincidence Scattering Chamber for Atomic Collisions
Authors: Kessel Quentin C.
Published: February 2004

A differentially pumped, atomic scattering chamber capable of detecting both ions following a large angle collision is described. This chamber is designed for use with incident ions having energies from 0.5 to 10 MeV. A construction technique is used which eliminates bellows and allows detection of atoms and ions over an angular range of 185°.
Operational Amplifier Differentiator for Photoemission Studies: Origin and Control of Errors
Authors: Kress Kenneth A. , Lapeyre Gerald J.
Published: February 2004

Errors encountered in time differentiating a voltage signal with a simple high gain operational amplifier differentiator are studied. Numerical and electronic means of correcting these generally small errors are suggested. The circuit, including a linear sweep voltage source, used for photoemission studies in this laboratory is presented. The coefficient of the error terms for this particular circuit are calculated numerically. Presently achieved sensitivity and resolution are discussed.
Programmable Temperature Controller for Small Diameter Wires
Authors: Emrick R. M. , McDonald D. E.
Published: February 2004

The study of lattice defects quenched into small diameter wires requires the precise control of the specimen at elevated temperatures. The circuit described has heated 0.127 mm diam wires to 350°C from 0°C in 2 msec and held the temperature constant to ±5C° in such media as air, mineral oil, and argon at 6 kilobars pressure. Maximum temperature is limited only by specimen design and environment. With an appropriate analog voltage input, the specimen temperature can be varied in any manner within the limits of maximum heating and cooling rates. Of particular interest is the ability of the circuit to provide a linear quench with time constant as long as desired.
Flyback System for a Constant Velocity Mössbauer Drive
Authors: Chase Robert L.
Published: February 2004

A flyback system is described for use with a Mössbauer drive transducer of the coupled loudspeaker type operating at constant programmed velocity. A flyback control waveform is generated which quickly returns the transducer to its starting position and reestablishes the programmed velocity without exciting mechanical resonances. In addition, the range over which the velocity is maintained constant and counting is permitted is automatically held constant, independent of the programmed velocity, to eliminate systematic errors that would result from a correlation between average position and velocity.
Channeltron Fatigue and Efficiency for Protons and Electrons
Authors: Egidi A. , Marconero R. , Pizzella G. , Sperli F.
Published: February 2004

The behavior of two type-4013 Bendix Channeltrons as single particle detectors has been investigated and the efficiency of detection for protons and electrons has been measured in a vacuum of 10−6 Torr. It has been established that under electron bombardment the gain decreases with time approaching an asymptotic value G∞ which depends only on the intensity of the incident flux. An empirical formula for the dependency of G∞ on the flux in the range 103 to 106 electrons/sec has been derived, G∞ = (1.3×1010)/J, where J is the incident flux measured in electrons per second and the high voltage applied to the Channeltron is 3 kV. When the bombarding beam is turned off the gain is always found to recover its initial value. The efficiency for electrons and protons does not show any dependency on the gain or on the particular Channeltron used.
Highly Stable High-Rate Discriminator for General Use in Nuclear Counting Applications
Authors: Rudnick S. J. , English J. J. , Howard R. H.
Published: February 2004

A new pulse amplitude discriminator, especially suitable for counting experiments, has been developed. Ten units were built and tested, and all of the threshold temperature coefficients are in the range −0.03 to +0.12mV per °C. At very high rates the threshold is stable and the output pulse width and the dead time change negligibly. Since the unit incorporates a number of convenient features, including provision for automatic dead-time correction, it is an extremely versatile instrument.
High Resolution Small and Wide Angle X-Ray Diffractometer
Authors: Kavesh S. , Schultz J. M.
Published: February 2004

A combination small and wide angle diffractometer is described. This instrument permits collection of both small angle and normal diffractometer data as a specimen is subjected to mechanical, chemical, or thermal treatment. Curved crystal focusing optics is utilized. The useful range of the apparatus is 0.023 to approximately 60° 2θ. The apparatus has the following features: (1) excellent resolution over the entire usable angular range (the focused primary beam has a half-breadth of 4×10−4 rad); (2) simplicity of design; (3) monochromatization of x rays; (4) ample specimen space, enabling one to heat, deform, or otherwise perturb specimens in situ. The unit utilizes a ground and bent quartz crystal, a Picker diffractometer, and a Hilger microfocus x-ray tube and generator. The basic unit can be assembled largely from factory-available apparatus, the exceptions being special mounts for the x-ray tube and the monochromator. The alignment procedure is briefly outlined and the positions of the necessary adjusting devices are described. A specimen heater, incorporated in this instrument and accurate to ±¼ C° from room temperature to about 150°C, is described. The heater utilizes the passage of hot gases to maintain the temperature. Finally, small and wide angle scattering curves are shown to illustrate the utility of the apparatus.
A Differential Adiabatic Microcalorimeter for the Study of Heats of Transition in Solution
Authors: Clem Thomas R. , Berger Robert L. , Ross Philip D.
Published: February 2004

A differential adiabatic calorimeter for the study of heats of transition in solution is described. The demonstrated sensitivity of the apparatus is such that a heat effect of 35 cal/liter occurring over a temperature range of 7°C was determined with a precision of ±2%. The results agreed with other reported work. The instrument employs solid state electronics and it may be operated from −10 to 90°C.
A Review of Electrical Feedthrough Techniques for High Pressure Gas Systems
Authors: Downs J. L. , Payne R. T.
Published: February 2004

Several types of high pressure electrical feedthroughs, principally pipestone cone seals, frozen oil seals, seals made with epoxy, and seals made with ceramically insulated thermocouple wire, are reviewed and evaluated with emphasis on the epoxy and thermocouple wire seals, which are especially suitable for small gas systems.
A Technique for the Rapid Measurement of Thermoelectric Power
Authors: Caskey G. R. , Sellmyer D. J. , Rubin L. G.
Published: February 2004

A new technique is described for rapid measurement of the thermoelectric power of rod-shaped specimens over a wide temperature range. The apparatus utilizes sensitive commercial dc amplifier for the sample and temperature gradient voltages and a multiple-point recorder for sampling these voltages as well as the sample temperature signal. The technique eliminates spurious thermal emf's in the leads and is based upon on-the-run recording of the sample and temperature gradient voltages as the temperature gradient slowly increases. As a test of this technique, the thermopower of pure nickel was measured between 4.2 and 300 K and the results are compared with other measurements using conventional techniques.
A Simple Modification of an X-Ray Spectrometer for Step Scanning and Filter Changing
Authors: Johnston W. V. , Romo P. C.
Published: February 2004

Inexpensive modifications to a commercial GE XRD-5 x-ray spectrometer to convert it to step scanning are described. A filter changing mechanism for optional use of the Ross balanced filter method is also described. The modified spectrometer may be used with any counting system which can be controlled by a switch closure. Some data are presented illustrating the use of the modifications in the determinations of atomic radial distribution curves for vitreous selenium.
A Sliding-Shaft Vacuum Lock for a Mass Spectrometer
Authors: Stoffels J. J. , Lagergren C. R.
Published: February 2004

A sliding-shaft type of vacuum lock for a mass spectrometer is described in which the sample carriage and pumping manifold are made entirely of sintered alumina (95% Al2O3). The hardness of this material effectively eliminates any problem of seizing due to entrance of foreign matter or gradual wear of the bearing surfaces. Components of the high voltage ion source are fully insulated when mounted directly on the carriage. The single ended design avoids the critical alignment required with two-manifold systems.
Convection Pirani Vacuum Gauge
Authors: Iglesias Guillermo E. , Santochi Orestes R. , Puparelli M.
Published: February 2004

A convection Pirani vacuum gauge covering the 1–1000 millibar range is described. It works in forced convection and Pirani modes for the high and low pressure ranges, respectively. Both effects combine in the intermediate zone. This gauge has been designed to be used with stratospheric balloons. Light weight, small power consumption, low temperature shift, and easy telemetering of information have been considered essential in the design.
Viscosity of Perfluorobutene-2; A Relative Method for Measurement of Gas Viscosity
Authors: Madhavan N. , Jones W. E.
Published: February 2004

A relative method for the measurement of gas viscosity is described. The method, similar to the Ostwald method for liquids, involves the comparison of flow times of various gases through a capillary flow meter. By this method the viscosity of perfluorobutene-2 has been determined as 118.1 μP.
Noise Power Spectrum Characteristics for an He–Ne Laser Operating under Various Discharge Conditions
Authors: Waksberg A. , Wood J.
Published: February 2004

This paper describes experiments performed to measure the noise characteristics of a helium-neon laser as a function of discharge characteristics. The discharge properties were varied by changing the pressure and current over a wide range of values. The effect of cold vs hot cathodes on the noise characteristics was also measured. Optimum regions are obtained where the laser has low noise characteristics. A large amount of data is included on noise bandwidth, laser power output as a function of pressure and current, discharge impedance characteristics, etc.
Calibration of the Atom Probe FIM
Authors: Panitz John A. , McLane S. Brooks , Müller Erwin W.
Published: February 2004

Accurate identification of atomic species in the atom probe FIM requires a highly shielded tip assembly, as well as a revision of the equation formerly used to compute the m/n ratios. Voltage reflections on the unterminated pulse transmission line cause the actual evaporation pulse at the tip to be greater than the applied pulse by a ``pulse factor'' α. In addition, the recorded flight time of the ion under investigation differs from the actual flight time by a constant electronic time delay δ. Using either of two single isotope calibration techniques, both α and δ can be determined. For a shielded tip assembly either technique gives a value of α=2.00±0.05 and a value of δ=0.06±0.02 μsec. Typical absolute mass determination using these values of α and δ is within ±0.6 amu at m/n=20, and ±1.6 amu at m/n=100. When masses near a known species, like hydrogen- or helium-metal molecular ions, are to be detected, the practical resolution reaches ±0.2 amu at the middle of the mass range.
High Temperature Continuous Creep Measuring Apparatus
Authors: Chen E. S. , Sadak J. C. , Sautter F. K.
Published: February 2004

A new apparatus for the continuous measurement of creep at high temperatures up to 1200°C is described. The apparatus is designed specifically for testing fine wire and thin tubular samples with small cross sectional areas. A unique application of the apparatus is for the creep testing of dispersion strengthened alloys where void formation and spheroidization may be monitored. The actual test procedure is presented.
A Single Charge 3He–4He Dilution Refrigerator
Authors: Critchlow P. R. , Hemstreet R. A. , Neppell C. T.
Published: February 2004

A single charge 3He–4He dilution refrigerator operating from a 3He stage at 0.3 K is described. The lowest temperature produced with this refrigerator was 0.027 K. The refrigerator was simple to construct and relatively easy to operate. The apparatus was well suited for very low temperature experiments where extended operation was not required.
A Constant Current Source for Manganin Gauge Transducers
Authors: Grady Dennis E.
Published: February 2004

The piezoresistive property of manganin has previously been exploited in producing a pressure gauge for shock wave studies. This article describes a constant current supply for the manganin gauge that utilizes an inductor as the essential constant current component. It is shown that the assumption of constant current can be made with negligible error. A termination technique is described which eliminates the gauge shunting current and hence simplifies data reduction.
Molecular Beam Reactive Scattering Apparatus with Electron Bombardment Detector
Authors: Lee Y. T. , McDonald J. D. , LeBreton P. R. , Herschbach D. R.
Published: February 2004

A crossed beams apparatus for study of thermal energy neutral-neutral reactions is described. The detector comprises a high efficiency (∼0.1%) electron bombardment ionizer, quadrupole mass filter, scintillation ion counter, and gated scalers synchronized with the beam modulation. The ionizer is nested within three chambers, each pumped by a separate ion pump and the innermost attached to a liquid nitrogen trap. The design is such that molecules which pass through the ionizer without being ionized fly on into another differentially pumped region before hitting a surface. The entire detector unit, including pumps and trap, is mounted on a rotatable platform (angular range ∼140°) which forms the lid of the scattering chamber. The beam sources also comprise modular units, mounted in differentially pumped side chambers which insert into ports in the scattering chamber. Angular distributions of reaction products have been measured for several reactions of Cl, Br, or D atoms with halogen molecules or hydrogen halides. Product velocity distributions have also been measured by time of flight for some of these reactions. In most cases, the partial pressure of interfering background species in the ionization region was ⪝ 10−15 Torr, and satisfactory data could be obtained with reactive scattering signals of a few counts per second.
Pulsed Field Emission Cathode Emittance Measurements
Authors: Uglum J. R. , Graybill S. E. , Nablo S. V.
Published: February 2004

A technique is described for the precise determination of the emittance diagrams for megavolt electron beams at energy fluences of up to 100 J/cm2. Two megaelectron volt beams from both single point hemispherical stainless steel and planar graphite emitters were studied, and emittance figures of 6.4 and 10.4 mrad·cm, respectively, were obtained for the central 4 mm diam portion of the streams generated by each configuration.
Fast Beam-Switching Electron Gun for Transient Beam-Plasma Interaction Study
Authors: Morris Glen J.
Published: February 2004

An electron gun and deflection system used to study transient beam-plasma interactions is described. The gun produces a 1 or 2 mm diam beam which can be switched off or on in ∼0.5 nsec. Two such guns used in a two beam device can easily excite large amplitude plasma oscillations. Measurements of damping in the time domain were made by measuring the damping rate of these oscillations following beam cutoff.
Simple, High Intensity Short Pulse Flashlamps
Authors: Ferrar C. M.
Published: February 2004

Various flashlamps were constructed using quartz envelopes and simple wire electrodes. The lamps were continuously evacuated to minimize explosive failures. Energies in the 10 to 1000 J range were discharged from low inductance capacitors through a triggered spark gap to the lamps. The lamp discharges occurred primarily in vapors ablated from the quartz envelopes and produced intense light pulses of 1 to 10 μsec duration with submicrosecond risetimes. Lamp explosion energies and peak light outputs were empirically found to be simply related to the lamp dimensions, making it possible to quickly design lamps for various applications. Successful pumping of high energy organic dye lasers demonstrated the effectiveness of these lamps in applications requiring short, high intensity pulses.
Potassium Ion Source
Authors: Cuderman J. F.
Published: February 2004

A potassium ion source is described in which potassium atoms diffuse through a thin, heated tantalum foil. The emitter surface is part of a sealed cell containing potassium. The potassium atoms are surface ionized as they emerge from the emitter. Ion and neutral fluxes characteristic of the source are given as a function of emitter temperature and potassium vapor pressure in the cell.
A Graphical Method for Calculating Intensities of Space-Focused Atomic and Molecular Beams
Authors: English Thomas C. , Gallagher Thomas F.
Published: February 2004

A simple graphical method for calculating focused beam intensities in an atomic or a molecular beam resonance apparatus using space focusing is described. The method takes into account the finite sizes of the source and detector and the distribution of velocities in the beam. It can be used to determine the effect of stops and other obstacles placed in the beam. In addition to serving as a calculational tool, the method provides physical insight into the focusing process. Using the method, the dependence of focused beam intensity on the length of the C field is investigated for a symmetric apparatus. It is found that as the C field is lengthened, the focused beam intensity first increases, then slowly decreases. The results of numerical calculations are presented for a molecular beam apparatus using quadrupole A and B fields, and a beam of carbon monoxide molecules. The implications for high resolution atomic and molecular beam spectroscopy are discussed.
Continuous Resistive Surface Deflection Unit
Authors: Catchpole C. E. , Ceckowski D. H.
Published: February 2004

The operation of an assembly using a uniform resistive surface to provide deflection of an electron beam is discussed. Essentially, the assembly consists of electroded plates of doped lead glass fused together and fired in hydrogen to produce the continuous resistive surface. Results indicate that when this assembly is employed in an image dissector tube, a 30° deflection can be obtained on either side of the central axis. The assembly was also operated with a vidicon gun and a test pattern was reproduced with very little distortion.
A Low Pressure Ionization Gauge
Authors: Swingler D. L.
Published: February 2004

An ionization gauge is described which uses an ion gun designed for end extraction. An out-of-sight ion collector is used to extend the x-ray limit normally present in simpler structures. The gauge head has a sensitivity of 60 Torr−1 without a secondary suppressor electrode or 20 Torr−1 with a secondary suppressor. The gauge head is not difficult to make, uses a simple power supply, and does not require any focusing adjustment. Ion trajectories, plotted by a digital computer, are used to give an insight into the efficient operation of the structure.
Gas Fed Multichannel Hollow Cathode Arcs
Authors: Delcroix J. L. , Minoo H. , Trindade A. R.
Published: February 2004

A new type of gas fed hollow cathode (multichannel cathode) has been studied. Such cathodes operate with a lower voltage drop and higher maximum current density than conventional one-channel cathodes and have a longer lifetime as well. Moreover, multichannel cathodes allow operation within a wide range of discharge currents and with extremely low gas flow rates. A theoretical analysis clarifies the principles of the operation of this type of cathode. The experimental results are explained and some general rules are presented for the cathode design.
A Laser Earth Strain Meter
Authors: Berger Jon , Lovberg R. H.
Published: February 2004

A laser interferometer for the study of earth strain is described. Changes in the length of an 800 m arm are measured by counting fringes in the interference pattern with a least count of 4×10−10. The output is linear and has a flat response from dc to 1 MHz and a dynamic range of 106. The laser wavelength is controlled by reference to a passive optic resonator contained in a stable environment. The wavelength stability is a few parts in 1010 for periods up to a laser lifetime (∼3000 h).
Writing Speed Determination of Sweeping Image Cameras Using a Photomultiplier Tube Calibrator
Authors: Marsh S. P.
Published: February 2004

A photomultiplier tube was used to detect light from an image sweeping over slits distributed across the image plane of the camera. The time interval between photomultiplier signals was measured using a Tektronix 545 oscilloscope. The resulting writing speed was determined with an error of less than 0.15% and showed a sec2θ variation over the image plane.
Quasilog Scaler
Authors: Weissman Richard
Published: February 2004

Data systems using information from long scaler chains often do not require the full resolution obtained by reading out the lower order bits of the chain when the accumulated count is large. However, if the count is small the lower order bits must be used. To reduce the total number of bits needed for a required resolution, a logarithmic readout can be used. The brute force logic to provide logarithmic readout would be cumbersome, particularly for aerospace application. A reduced logic system following a set of generalized equations to provide quasilogarithmic readout of any conventional binary scaler is described, which permits extremely simple circuitry with size, weight, and power requirements suitable for aerospace and similar applications. An example is shown of a complete circuit using a 20-stage scaler with five-bit logarithmic readout.
A Recording Detection System for Quantitation of Electron Microscope Image Contrast Using a Retractable Micro-Faraday Cage Probe
Authors: Johnson H. M. , Hausner G. G. , Parsons D. F.
Published: February 2004

A recording electrometer system is described based on a retractable micro-Faraday cage probe mounted in the beam stop port of a Siemens Elmiskop IA electron microscope. A vibrating reed electrometer is used to measure the current collected by the probe. Intensity data at different points in the image are collected by moving the image over the fixed probe by manipulation of the specimen stage controls. The total system has a noise less than 3×10−15 A, a 10 sec full scale response time, and provides immediately observable image intensity data which can be converted into contrast.
A Reliable Flashlamp Pumped Tunable Organic Dye Laser
Authors: Goldstein A. , Dacol F. H.
Published: February 2004

An improved flashlamp pumped dye laser is described. Reliable long term operation has been attained by using a low inductance capacitor bank. A linewidth of 0.3 Å and a beam divergence of 2.5×10−3 rad result from more uniform optical pumping in the flashlamp. Tuning ranges of several organic dyes are presented.
New Two-Point Calibration Method for Platinum Resistance Thermometers for the Range 75–400 K
Authors: Pratt J. P. , Ailion D. C.
Published: February 2004

In this paper we describe a new method for calibrating high quality platinum resistance thermometers to ±0.01°C over the temperature range 75–400 K. This method requires resistance measurements at only two temperatures (liquid nitrogen and the ice point) in contrast to other methods which require measurements at four temperatures. The method is based on the invariance of Cragoe's Z-functions (resistance ratios) with respect to different high quality platinum thermometers. In addition our method uses the new International Practical Temperature Scale of 1968 (IPT-68). We checked our calibration at two intermediate temperatures (liquid oxygen and the fusion point of mercury) and measured deviations of less than ±0.01°C from our calibration.
A Live Time Controlled Scanning Rate for a Whole Body Counter
Authors: Sveum M. E. , Bramson P. E.
Published: February 2004

Scanning whole body counters tend to sacrifice sensitivity and introduce measurement error through the use of constant drive rate mechanisms which do not readily compensate for changes in electronic deadtime. An electronic drive rate control has been developed at Battelle-Northwest Laboratory which largely eliminates this problem. The control automatically adjusts the relative drive rate to correspond to multichannel analyzer live time and is easily programmed for subject height and count duration. Digital circuitry, utilizing integrated circuits, controls the speed of a heavy duty stepping motor by controlling the motor stepping frequency. A scanning whole body counter utilizing the typical constant drive rate tends to underestimate the body or organ burden of a subject whose deposition caused abnormally high analyzer deadtime. A counter utilizing the live time control will spend proportionally more real scanning time over an area of high deposition, resulting in a desired amount of ``scanning live time'' for which the counter calibrations apply.
A Floating Microcompass for Measuring Millioersted Magnetic Fields in Millimeter-Cube Sampling Volumes
Authors: Helmke G. E. , Schultz-DuBois E. O.
Published: February 2004

A magnetic compass is described which permits the measurement of small magnetic fields with relatively high accuracy and in sample volumes of small linear dimensions. In a particular model, 300 mOe were measured with better than ±2% accuracy and at a distance of less than 1 mm from the source of the magnetic field. Novel features in this compass are its reduced size and the liquid suspension. By the action of surface tension, the magnetic needle floats on the rotationally symmetric meniscus of a water surface in a capillary. The suspension offers centering, damping of motion, and elimination of static friction. The paper gives design view points and technology, discusses the measurement method and error sources, and presents examples of measurements.
A Narrow Band Far Infrared Interferometer for Electron Density Measurements
Authors: Andrews Merrill L. , Brown Sanborn C.
Published: February 2004

An interferometer has been constructed with reflection optics and lamellar gratings to operate in the wavelength range of 175–400 μ. The gratings serve not only as beam splitters and recombiners but also as filters to separate out a narrow band of radiation. In this way a simple wide band Hg arc lamp can be used as the source. Because of the required response time for afterglow plasmas, a Putley detector measures the radiation. An application of the interferometer has been made to measure electron densities in repetitively pulsed plasma with λ = 200 μ and a time response of 3 μsec. The electron line density sensitivity is 3×1013 cm−2 and line densities have been measured up to 1015 cm−2, still substantially below the instrumental limit.
Degradation of Laser Optical Surfaces
Authors: Barber T. L.
Published: February 2004

Problems of optical surface degradation became apparent while measurements were being made with a laser. After examination, it was concluded that the defects fell into two categories—those caused by atmospheric dust, and those resulting from the effects of cleaning solvents. A procedure is described which minimizes both of these problems.
Aerosol Size and Velocity Determination via Holography
Authors: Fourney M. E. , Matkin J. H. , Waggoner A. P.
Published: February 2004

An experimental technique for obtaining the spatial size and velocity distributions for liquid or solid aerosols suspended in an air flow is described. The technique leaves the flow undisturbed and allows for a large range of particle sizes and velocities. The successful combination of a Q-spoiled ruby laser and holography was employed to record the desired information. A helium-neon laser was used to reconstruct the magnified image which was analyzed using closed circuit television.
Technique for Annealing Irradiated Uranium under High Hydrostatic Pressures and Temperatures
Authors: Kulcinski G. L. , Thiede R. A. , Hann C. R.
Published: February 2004

This article describes the equipment, techniques, and philosophy associated with experiments designed to anneal irradiated uranium in NaK to temperatures as high as 900°C and pressures as high as 1000 bars. Considerable attention is paid to the details of the experimental procedure owing to the inherent dangers connected with such tests.
Some Logarithmic Properties of Photomultipliers
Authors: Maydan D. , Shaanan M.
Published: February 2004

The logarithmic properties of a photomultiplier are investigated. There is a logarithmic relationship between the voltage and gain of a group of three dynodes of a photomultiplier. An exponential current generator for the calibration of logarithmic amplifiers based on these principles is described. The dynamic range of the generator is about 4 decades with an output current of 250 mA. The exponent is constant within a few percent over the entire range. The calibration of a fast logarithmic amplifier is shown. The generator can also be used to simulate the wave shape of fast scintillators with exponents as fast as a few nanoseconds.
New Crystal Spectrometer for Neutrons
Authors: Stedman R. , Almqvist L. , Raunio G. , Nilsson G.
Published: February 2004

A new feature of the spectrometer is the monochromator unit, which contains two parallel reflecting copper crystals and delivers a beam of monoenergetic neutrons through a fixed collimator which is parallel to the incident beam from the reactor. About half the neutrons reflected by the first crystal are reflected by the second crystal, though the fraction declines at the upper end of our energy scale (about 60 meV). The beam from the monochromator is free from fast neutrons, and the background extremely low. The material, thickness, and mosaic width appropriate to efficient reflection in a monochromator crystal are discussed. The sample and analyzer form a compact separate unit on a stationary base. All the angles of the spectrometer (including those of the monochromator) are continuously variable over wide ranges, with either manual control or automatic control from a programming tape. Two spectrometers which are mirror images of one another are mounted side by side at the same reactor beam hole. They are mainly intended for measurements on phonons with comparatively high resolution. An example of the accuracy attained is given.
Nonlinear Control Theory for Constant-Temperature Hot-Wire Anemometers
Authors: Freymuth Peter
Published: February 2004

The linear control theory for constant-temperature anemometers can be extended to the nonlinear case which applies for large velocity fluctuations. The nonlinear theory establishes the domain within which the linear theory is valid and reveals some nonlinear effects for large velocity fluctuations. Calculations using a second order approximation have been carried out for velocity fluctuations as large as ±64% of the mean velocity. They show in case of a sinosoidal input function the generation of a second harmonic at the output which limits the usefulness of the anemometer at high frequencies. In case of a large velocity step, a longer time is required to indicate the step correctly than is required for the indication of a small step.
Elimination of Photomultiplier Gain Shift Due to Extraneous Weak Reversible Magnetic Field
Authors: Palathingal J. C.
Published: February 2004

In measurements of circular polarization of gamma rays in which the radiation is detected by a scintillator coupled to a photomultiplier, the phototube has to be shielded from the reversible fringing magnetic field of the polarization analyzer. Weak residual fields, however, produce a small gain shift between the photomultiplier outputs during the periods of opposite magnetizations of the polarimeter. By applying slightly different voltages to the photomultiplier simultaneously with reversals of the magnetic field, this shift can be eliminated. A simple effective method of utilizing this suggestion is outlined.
A Sum-Delay Amplifier and Gate Generator
Authors: Simms P. C.
Published: February 2004

The sum-delay amplifier and the gate generator are in separate single-width NIM modules. The amplifier has five input channels which can be switched in or out. The delay can be switch selected to be 0, 1, or 2 μsec. The gate generator is very flexible. It will accept almost any type of input signal and produce an output pulse which can be adjusted to meet most gating requirements. One frequent use of the instrument is to observe the performance of an electronic system while an experiment is being performed.
Ultrahigh Vacuum Reflectometer for Use with Extreme Ultraviolet Synchrotron Radiation
Authors: Feuerbacher B. , Skibowski M. , Godwin R. P.
Published: February 2004

An ultrahigh vacuum reflectometer is described. It can be used to study reflectance, transmittance, and photoemission on samples evaporated in situ. The angle of incidence can be varied from 0 to ±90° in steps of 7.5°. The system rotates about the axis of the incident light for study of polarization effects. With the polarized continuum of synchrotron radiation and a normal-incidence monochromator the reflectometer allows measurements with polarized light at wavelengths down to about 300 Å.
Secondary Electron Yield vs Primary Energy for Commercial Coated-Glass Resistance Strips
Authors: Streeter J. K. , Hunt W. W. , McGee K. E.
Published: February 2004

The mean secondary electron yield has been determined as a function of primary electron energy from 20 to 70 eV for the dynode-strip surface of a commerical resistance-strip magnetic electron multiplier. Both the primary energy and the secondary yield were determined by measuring the multiplier output current while varying the voltage applied to the field-strip input end at each of three fixed dynode-strip input-end voltages. The measured mean secondary yield increases linearly from about 1.2 at 20 eV to about 1.7 at 70 eV.
Quantum Efficiency Measurements Using a 2π-Geometry Elliptic Mirror
Authors: van der Does de Bye J. A. W.
Published: February 2004

For measurements of photoluminescence and electroluminescence an alternative is described to the well known, but rather inefficient, integrating sphere. The new instrument consists mainly of a deep elliptic mirror with 2 π geometry with respect to the sample. Sample and photodetector are positioned at the two focal points.
Hot-Microhardness Test Equipment
Authors: Kamphouse J. L. , Blake J. C. , Moteff J.
Published: February 2004

A micorhardness tester has been developed for use in the temperature range 10 to 1400°C, with loads up to 1 kg. The apparatus utilizes a uniform strength beam instrumented with strain gauges for load determination. Temperature control, load control, holding time at full load, and the indenting process itself are performed remotely and automatically, thus facilitating the testing of radioactive specimens.
Calibration of an Image-Converter Streak Camera
Authors: Ahrens Thomas J. , Spetzler Hartmut
Published: February 2004

A new technique for time calibrating an image-converter streak camera by repetitively photographing a standard signal displayed on a wide-band sweep-delay oscilloscope is described.
Instrument for the Measurement of Surface Tensions of Aqueous Surfactant Solutions
Authors: Wilbur R. L.
Published: February 2004

This report describes an instrument capable of accurately measuring the surface tensions of aqueous surfactant solutions with slowly varying surface areas. The instrument consists of a surface balance, a strain gauge transducer, an amplifier-indicator, and an X-Y plotter. Derivation of the basic equation demonstrates achievement of an instrumental solution analogous to the algebraic equation. A brief discussion of operational procedures outlines the method used for the retrieval of accurate data.
A 500 Liter Hydrogen Bubble Chamber
Authors: Pless I. A. , Bailey B. M. , Biron R. D. , Karageorge G. K. , Marcato P. , Martin K. B.
Published: February 2004

A bubble chamber designed to operate with 500 visible liters of liquid hydrogen has been tested for performance with liquid nitrogen at Argonne National Laboratory. It features unique systems for controlling chamber overpressure and minimizing thermal gradients within the working liquid. Refrigeration requirements were determined for the full range of operating conditions from static to expansion-pulsing at a rate of 3/sec at intervals ranging from 333 msec down to 125 msec.
Analog Computer for Calculation of Second Moments in NMR
Authors: Gibson A. A. V. , Raab R. E.
Published: February 2004

A special purpose analog computer is described for calculating the second moment of the NMR absorption spectrum drawn out by a wide-line spectrometer with an integrating phase-sensitive detector (PSD). An experimental check on NH4Cl yielded a mean second moment within 1% of a previous value, and a standard error over 50 observations of 2%. The integrating PSD enabled these spectra to be recorded over 100-sec sweeps with a signal-to-noise ratio comparable to that obtained using conventional techniques with sweep times at least an order of magnitude longer.
Scanning Electron Diffraction Attachment with Electron Energy Filtering
Authors: Graczyk J. F. , Moss S. C.
Published: February 2004

A scanning electron diffraction attachment providing for energy analysis of the scattered electrons has been constructed for use in conjunction with a J.E.M. 6AS electron microscope. This attachment permits the direct recording of diffracted electron intensities as a function of angle with an accuracy of ±0.1%. The attachment can be operated to exclude all but the elastically diffracted electrons, or, alternatively, to detect electrons with a measurable amount of energy loss. The electrostatic energy analyzer has an energy cutoff of better than 1.1 eV out of 100 keV. The angular resolution of the instrument is presently 2.2×10−4 rad, with minimum detectable electron intensity of 10−14 A. The instrument performance is demonstrated by studying the effect of inelastic scattering in the diffraction pattern of aluminum, and by recording the plasma loss spectrum of aluminum. The filtered profiles have narrower peaks than the unfiltered ones and better peak resolution, and the contrast between peaks and background is enhanced. At low values of the scattering vector where the inelastic background is very intense, its removal reveals diffraction effects which otherwise would have been invisible. The attachment does not interfere with the conventional plate microscopy and diffraction, and provides, thereby, a method of energy analyzing the direct microscope image as well.
Gas Additives for Stable Pulsed Argon Ion Lasers
Authors: Gilson V. A.
Published: February 2004

Various combinations of noble gases are experimentally investigated to help improve the triggering stability of pulsed ion lasers. The results of these tests show that a 1:1 ratio of Ne–Ar stabilizes the triggering, but gas separation limits the repetition rate. Tests on He–Ar show that 15 μ of Ar combined with 15 to 100 μ of He produced triggering stability with no obvious detrimental effects at pulse rates up to 1000 Hz. Both mixtures displayed 25% power loss with respect to the optimum pure argon laser output.
Density Measurements in a Valve Driven Shock Tube
Authors: Dewey John M. , Anson W. A.
Published: February 2004

A gauge for the measurement of the density variation in a shock wave is described. It is based on the absorption of low energy beta radiation from an 169Er source. The gauge was used to study the density variation through the contact zone between the expansion chamber gas and the driver gas of a valve driven shock tube. Comparisons are made between the measured density and that calculated from pressure measurements in terms of the initial condition of the test and the driver gases. There are significant differences between these densities due to mixing of the two gases in the contact zone.
Description of a Controllable Sonic Flow Orifice
Authors: Eichhorn R. , McLean J. D.
Published: February 2004

By varying the length of a constant area passage in which the mass flow is limited by frictional effects a controllable valve results with characteristics close to those of the critical flow orifice. This design principle leads to a simple valve geometry which is easier to manufacture and is generally sturdier than a comparable needle valve. For a prototype and a bank of 10 similar valves designed to furnish 0.025 kg/sec from a 10 MN/m2 source of air, the results confirm fine control of the mass flow rate by a factor of 2 or more and a mass flow rate dependent on the square root of upstream stagnation pressure.
A Nonsuperconducting Detection System for Low Level dc Voltages
Authors: Clark Alan F. , Fickett Frederick R.
Published: February 2004

A low level dc detection system with an attainable precision of 25 pV is described. The system uses only normal metal components and commercially available equipment. Measurements can be made automatically, in the presence of large (microvolt) spurious voltages, with switched inputs, and in a non ``null'' configuration. A typical application is described in detail.
A Logarithmic Electrometer for Space Flight Application
Authors: Chater W. T.
Published: February 2004

A very simple logarithmic response dc electrometer circuit is described which makes use of a novel connection for developing the log feedback signal. The resulting improvement in bandwidth over familiar circuits is discussed.
A Differential Emissivity Calorimeter
Authors: Barkalow B. H. , Baldwin K. M.
Published: February 2004

A calorimeter utilizing a differential emissivity thermopile to measure directly the radiant heat exchange of small animals is described. Other modes of heat exchange are effectively eliminated by containing the animal in an infrared transparent container. Noise on low level signals is minimal due to a special heat sink design. Construction details, optimization, calibration, and the validity of negative thermopile signals for radiant energy absorption are discussed.
Oxide Thermistor for Use to 2500 K
Authors: Wolff Ernest G.
Published: February 2004

An oxide semiconductor thermistor for application in the range 1000–2500 K was designed, fabricated, and tested. Construction materials consisted of zirconia with 15 mole % yttria as the sensor element, iridium plus 40 wt% rhodium as the lead wires, and beryllium oxide as the insulating material. Sensors were tested for resistance and voltage characteristics, thermal shock resistance, stability, sensitivity, and response. Linearized temperature indication and time lag compensation are also discussed.
Millimeter-Wave Electron Spin Resonance Spectrometer with Homodyne Detection
Authors: van den Boom H.
Published: February 2004

A millimeter-wave electron spin resonance spectrometer working in the E band (67–74 Gc) has been assembled. Features connected with the use of millimeter waves, in particular the microwave cavity, the low temperature assembly, and the klystron stabilization, are described in detail. Furthermore the spectrometer design as a whole and the sensitivity obtained are discussed.
A Current-to-Frequency Converter for Astronomical Photometry
Authors: Taylor Donald J.
Published: February 2004

A simple current-to-frequency converter has been developed which works directly with photomultiplier currents. It has full scale input current ranges of 3×10−10 to 3×10−6 A. The feedback pulse is a square pulse that is clocked on and off by a continuously running oscillator. Drift in the oscillator frequency is compensated if the oscillator also serves as the time base of the counter used to count the pulses. With oscillator frequencies up to and including 20 kHz the linearity is 0.01% or better and the drift less than 0.01% of full scale per hour.
Flash Radiography Using Exploding Wire Technique
Authors: Stenerhag B. , Händel S. K. , Göhle B.
Published: February 2004

By exploding a thin tungsten wire in vacuum, it is found that an ultrafast (20 nsec half-width), reproducible x-ray pulse is emitted from the wire during the first half-cycle of the discharge. The half-width of the pulse seems to be independent of the ringing frequency of the discharge circuit. It is shown that it is possible to use the exploding wire as a flash x-ray source for taking radiographs of high speed events, e.g., an exploding copper wire.
High Voltage Capacitor Bank Charging through a Series Vacuum Tube
Authors: Witkover R. L.
Published: February 2004

The use of a vacuum tube as the isolating element in the charging of a high voltage capacitor bank was investigated analytically and experimentally. The series tube effectively open circuited a 60 kV power supply from a 20 μF capacitor bank upon command during bank discharge and when there was a ``crowbar'' or fault in the rf system. The tube cutoff capability allowed its operation as a switching regulator, providing precision voltage regulation for the capacitor bank. Programming the series tube grid circuitry for constant charging current allowed reduction of the peak current requirements of the charging power supply and smoothing of the load on the utility lines. Analysis of the modes of operation, description of the circuitry employed, and operational results are presented.
Simplified Instrumentation for Tone-Burst Measurements of Nuclear Spin-Lattice Relaxation Times
Authors: Smith W. C. , Torgeson D. R.
Published: February 2004

A modulation gating control, similar in function to a tone-burst generator but simpler, has been developed. The instrument is used with a digital time-averaging data system and requires a single timing circuit, an analog delay.