bluuebunny/crossref_metadata_2025 huggingface dataset:
Forced Vibration Tester in Tension and Torsion for Plastic Materials under Tensile Strain
Authors: Lepie Albert H.
Published: February 2004

This paper describes an apparatus for applying simultaneously or alternately forced vibrations in tension and torsion on viscoelastic samples. The measurements can be made on unstrained or strained samples within a frequency range from 0.01 to 10 Hz. The temperature control of the sample is achieved either in an air circulating chamber or in a liquid environment. Typical results of measuring the dynamic moduli of a carbon black filled rubber in tension and shear are presented. The complex Poisson's ratio of filled rubber was calculated from its dynamic moduli as a function of strain.
Oscillating Fiber Microbalance
Authors: Patashnick Harvey , Hemenway Curtis L.
Published: February 2004

An instrument is described which enables direct mass determinations in the range 10−5–10−11 g and can be modified to provide greater mass sensitivity if desired. The principle involved is that of an electrostatically driven oscillating thin fiber, clamped at one end and free at the other, which changes its resonant frequency when mass is added to the free end. The over-all electromechanical design eliminates many of the disadvantages of more conventional microbalances and surpasses them in sensitivity and accuracy.
Stable 1 pF Charge Injection Capacitor for Nuclear Pulse Preamplifiers
Authors: Brenner Raul
Published: February 2004

Servostabilizers used with Ge(Li) γ-ray spectrometers are frequently referenced to pulser peaks obtained by injecting the output of a stable pulse generator into a charge sensitive preamplifier via a small capacitor. A 1 pF charge injection capacitor has been developed that meets the requirements of high resolution spectrometers. The three terminal air capacitor has a coaxial structure with electrodes made of Kovar. It has a temperature coefficient ranging from −1 to +6 ppm/°C and a long term stability of ±20 ppm, i.e., less than ±0.1 channel out of 4000. It adds only 1 pF of stray capacitance to ground at the preamplifier input and the noise added with 3 kV across it is negligible.
An Automated Resilience Apparatus for Polymer Studies from −196 to +180°C
Authors: Robbins R. F. , Weitzel D. H.
Published: February 2004

A rebound resilience apparatus was developed to study the dynamic mechanical properties of polymeric materials from −196 to +180°C. Resilience data at a frequency of about 3500 Hz are obtained by measuring ball velocity near the sample with a photoelectric device. Frequency of impact is estimated using a microphone pickup. The results are recorded automatically with a data acquisition system designed for the test. The apparatus is virtually automatic in operation and has wide flexibility in sample configuration, temperature range, and temperature control. The results can be related to other dynamic mechanical properties data, and estimates of Young's modulus in the regions of high resilience can be made.
High Vacuum Adhesion Test Apparatus
Authors: Hordon M. J. , Wright M. A.
Published: February 2004

A vacuum apparatus is described to measure the interfacial adhesion of uniaxially loaded metal surfaces. Integral abrasion and ion beam bombardment devices for removing surface contaminant films in vacuum prior to interfacial contact are contained in the system. Measurements of the tensile force to rupture contact weldments in copper showed that the adhesion strength varied with the effectiveness of surface oxide removal and with the applied compressive contact stress and corresponding deformation strain. The interfacial electrical contact resistance was observed to decrease substantially with increasing adhesion.
A Drop Calorimeter with an Electron Beam Heated Furnace
Authors: Fredrickson D. R. , Kleb R. , Nuttall R. L. , Hubbard W. N.
Published: February 2004

The design and operation of a calorimetric system for the measurement of high temperature enthalpy by the method of mixtures, or ``drop method,'' is described. Features of the system are (1) an electron beam heated furnace, with sample temperatures determined by optical pyrometry, (2) a copper block calorimeter with calorimeter temperatures obtained by quartz crystal thermometry, and (3) provision for pneumatic acceleration of the sample from the furnace into the calorimeter to minimize heat losses during the transfer. The system has been used to measure the enthalpy of tungsten in the temperature range 1300–1900 K. Values agree with literature data to ±0.5%.
A Large Desorption Cryostat for Resistivity Measurements between 1.2 and 19 K
Authors: Waldorf D. , Yaqub W.
Published: February 2004

A large desorption cryostat with a heat leak of about 150 mW is described. With the help of an electronic temperature regulator it is capable of maintaining any temperature between 4.2 and 19.0 K to an accuracy of better than 0.5%, using only 200 g of activated charcoal.
A New High Resolution Reflection Scanning Electron Microscope
Authors: Broers A. N.
Published: February 2004

A new high resolution reflection scanning electron microscope has been built with a lanthanum hexaboride cathode electron gun, a contamination-free vacuum system, and in which the deteriorating eflects of vibration and ac stray field interference have been reduced below significant levels. The microscope produces a minimum probe diameter of 30±7 Å with a current of 10−12 A at a working distance of 7 mm and an accelerating voltage of 23 kV. Point-to-point resolution of 50±10 Å has been measured in scanning reflection.
Single Detector Method for High Resolution Internal Conversion Coefficient Measurements
Authors: Avignone F. T. , Knox H. H.
Published: February 2004

A method for measuring internal conversion coefficients, in which γ rays and conversion electrons are detected in the same Si(Li) detector, was developed. The energy spread for both γ rays and electrons is 5 to 7 keV. The detector is mounted on a cold finger in a vacuum chamber with the source. The chamber has an externally controlled aluminum electron absorber between source and detector for γ-ray measurements, which can be rotated away for electron measurements. This apparatus was calibrated using nine well known conversion coefficients with electron energies from 62 to 973 keV. The αK of the 355 keV transition of 133Cs and the αK and αL of the 482 transition of 181Ta were measured by this method. The values are (0.020±0.001), (0.0234±0.0010), and (0.0054±0.0003), respectively.
Design of a Multipurpose Wind Tunnel
Authors: Stein Gilbert D.
Published: February 2004

A continuously operating wind tunnel was designed for light scattering experiments in supersonic two-phase flow. Special features permit easy modifications of the equipment for a variety of studies.
A Cell for the Infrared Study of Molecules at Low Temperatures
Authors: Hermann T. S.
Published: February 2004

A new optical cell has been designed to acquire conveniently the infrared spectra of molecules at low temperatures via the multiple internal reflection technique. This cell offers a unique means of studying the molecular structure of intractable molecules, certain liquid-solid interfaces, and the surfaces of infrared transmitting semiconductors at low temperature. A simple modification of this cell can be used to collect and analyze such gaseous samples as gas chromatographic fractions, impurities in air, and volatile toxic chemicals. The modified cell could conceivably be used to collect and analyze ``hot'' species as generated in matrix isolation studies.
Surface Ionization Source for Ion Implantation
Authors: Jamba Douglas M.
Published: February 2004

A surface ionization source was designed and developed to produce useful ion beams of elements with ionization potentials up to about 6 eV by using iridium (work function 5.27 eV) as the ionizing surface. Sources were operated successfully producing stable ion beams of aluminum, gallium, indium, and thallium with current densities up to 10 μA/cm2. Neutral atoms are shielded from the beam as it leaves the source by a special design geometry. The construction, developmental details, and operating parameters of the source are described.
Instrumental Effects of the Retarding Grids in a LEED Apparatus
Authors: Wei P. S. P. , Cho A. Y. , Caldwell C. W.
Published: February 2004

We have studied the characteristics of the retarding grids in a low energy electron diffraction apparatus by measuring the impact spectra of a tungsten (100) crystal with 66 to 200 eV electron beams. Our results indicate that the retarding field method when properly adjusted is useful for analyzing scattered electrons of energy loss which is small compared to the beam energy. At large energy loss, however, field penetration and scattering from grids may contribute considerably to the measured secondary electron energy distribution which makes the measurement less reliable.
Computer Control of the Analyzing Magnet of an MP Tandem Van de Graaff Accelerator
Authors: Bergman Clark , Hobbie Russell K.
Published: February 2004

Tandem Van de Graaff accelerators are often used to measure excitation functions, requiring that the beam energy be repeatedly changed by small amounts. These experiments can be performed with improved efficiency and accuracy by having the on-line computer which controls the experiment set the magnetic field which defines the beam energy. This paper describes the system used at the University of Minnesota.
Accurate Temperature Measurements on a Microbalance Suspension by Inductive Coupling
Authors: Dail H. W. , Knapp G. S.
Published: February 2004

We have devised a system for making accurate temperature measurements of a sample attached to a thermometer on a microbalance suspension. The thermometer is inductively coupled to the external measuring circuit so it does not disturb balance sensitivity. Using a carbon resistor thermometer and one calibration point at 4.2 K, we can reproduce temperature measurements between 4.2 and 30 K with a relative accuracy of ±0.1 K and an absolute accuracy in the range of 20–30 K of ±0.5 K. The system is presently used in susceptibility measurements but the method can be applied to other experiments with minor modifications.
Rotating Cylinder Viscometer
Authors: Snyder H. A.
Published: February 2004

A rotating cylinder viscometer is described which depends for its operation upon measuring the frequency of a periodic flow. Compared with viscometers in common use, the results of this instrument are influenced to a smaller extent by end effects, difficulties of adjustment, or the requirement for high precision parts of special materials. It features ease of construction and maintenance, the adaptability to continuous sampling and monitoring, and a precision of about 0.3% in the measurement of the kinematic viscosity. The sensitivity of the apparatus to various aberrations is illustrated. Design considerations and attainable performance standards are discussed.
Discrete Averaging of X-Ray Diffraction Data Using a Multichannel Analyzer
Authors: Berman Martin , Ergun Sabri
Published: February 2004

A system is described in which a multichannel analyzer is used to repeatedly scan a powder x-ray diffraction spectrum in discrete intervals. Counts are recorded at a given angle for the required dwell time. A preset indexer actuated by the multichannel analyzer drives a stepping motor the required increment in angle. The channel memory is advanced by one and the above process is repeated until the end of a scan. The indexer then drives the diffractometer back to the starting angle. Scans are repeated until sufficient data are accumulated. All the scans are made in the same direction to avoid backlash errors. The system prints out the contents of the memory at definite intervals (usually every 12 h) so that in the event of a malfunction only the data taken since the last printout are lost. Other advantages and some disadvantages of the system are described.
Application of a Variable Resistance to Arrest Oscillations in a Pulsed Capacitor Discharge Circuit
Authors: Cheng Dah Yu
Published: February 2004

Kirchhoff's equation for the current flow from a capacitor connected in series with an inductance and a resistance that varies with current is solved by an iterative integration scheme. The resistance of the circuit is assumed to increase during the discharge due to Joule heating. The conditions for over-, under-, and critical damping are derived such that a circuit can be designed that has a short risetime and a long decay time without current oscillation. The realistic nature of the circuit is verified experimentally.
Miniature Low Energy X-Ray Calibration Tube
Authors: Grader R. J. , Scudder J. K. , Tindall W. E.
Published: February 2004

The design and operation of a miniature x-ray tube used as a calibration source for a rocket borne x-ray astronomy experiment are described. The tube utilizes a miniature lamp filament and a 0.05 mm aluminum foil as a transmission target. Anode current of 1 μA and accelerating potential of 4 kV produce approximately 1000 1.48 keV photons/sec. Shelf life of the tube is greater than three months and the operating life is several hours.
Improvement of the Signal-to-Noise Ratio of Photomultipliers for Very Weak Signals
Authors: Topp J. A. , Schrötter H. W. , Hacker H. , Brandmüller J.
Published: February 2004

For the photoelectric detection of Raman spectra excited with a He–Ne laser, the dark current of an EMI 9558 QA photomultiplier is reduced by magnetic defocusing of the electrons originating from the inefficient part of the photocathode. A lightpipe cone concentrates the light signal to a spot of 2.7 mm diameter and enhances the quantum efficiency of the photocathode by multiple reflection. A pulse counting system with a deadtime of less than 100 nsec is described and compared with dc detection. It is now possible to detect signals with a power of less than 10−17 W or less than 35 photons/sec at 650 nm with a time constant of 1 sec. The improvement in signal-to-noise ratio is demonstrated with the Raman spectrum of polycrystalline azobenzene.
Sample Holder for Diffraction and Other Studies in Ultrahigh Vacuum
Authors: Jona F. , Wendt H. R.
Published: February 2004

A sample holder suitable for ultrahigh vacuum experimentation is described that allows, in addition to translation and tilting, rotation of the sample around two mutually perpendicular axes.
Line Broadening in Photoelectron Spectroscopy
Authors: Samson James A. R.
Published: February 2004

The factors causing line broadening in photoelectron spectroscopy are discussed. Experimental results are given for the half-width of the 584 Å helium line emitted from a variety of sources. Typical half-width values lie between 1 and 6.5 mV, which corresponds to 0.027 and 0.18 Å, respectively. Curves are presented showing the contribution of the thermal motion of the photoionized gas to the spread in the energy of the ejected photoelectrons.
An Apparatus for the Production of Very Soft X Rays at High Intensity
Authors: Clark B. C. , Gross W.
Published: February 2004

An apparatus has been developed for producing high intensity x-ray beams at constant potential between 1 and 6 kV. An electron beam produced by a specially designed electron gun of the Pierce-Müller type bombards a rotatable target. Beam currents up to 500 mA have been achieved. The design permits the positioning of each of four different target materials into the electron beam. Targets are prepared by vacuum evaporation of the desired material onto a target block. A thin window (beryllium foil and Mylar film) provides an exit path for the x rays and has acceptable transmission at energies above 1.5 keV. Such very soft x rays are strongly absorbed in air, but may be brought through a helium path and plastic foil exit window to a test system for investigation of their effects.
The Performance of a Mechanical Heat Switch at Low Temperatures
Authors: Colwell Jack H.
Published: February 2004

A mechanical heat switch used in calorimetry experiments down to 0.3 K is described and its performance analyzed in sufficient detail to be useful for design purposes. The thermal conductance of the indium-copper switch contacts was determined as a function of temperature and applied force over the range 0.3–2 K. These results are compared with other conductance measurements to evaluate choices of metals for heat switch contacts.
Two Coil rf Determination of Plasma Conductivity
Authors: Mikoshiba S. , Smy P. R.
Published: February 2004

This paper describes a new method of measuring the electrical conductivity of a plasma by utilizing the dependence of the mutual inductance of two coils upon the conductivity of the medium lying between them. In addition to its simplicity, the method has several advantages over previous single coil measurements; these are (a) high speed response ∼0.02 μsec, (b) it gives a measure of the average conductivity in the plasma rather than that very close to the coil, (c) it can be used over a continuous and wide range of frequencies with the result that a very wide range of conductivity can be measured (to 106 mhos/m). Electrostatic effects can be eliminated by the use of a third coil which avoids any necessity for electrostatic screening. Measurements have been performed upon electrolytes and plasmas with conductivities from 10 to 104 mhos/m at frequencies from 0.1 to 50 MHz, and in every case agreement with theory is excellent.
Apparatus for Determining Thermophysical Properties of Solids by Direct Electrical Pulse Heating
Authors: Finch R. A. , Taylor R. E.
Published: February 2004

A pulse heating apparatus capable of initial heating rates of 7000 to 165 000°C/sec on 0.3175 cm diam samples of zirconium-uranium hydrides is described. Currents from 1000 to 5000 A are used. Potential drops, current, electrical resistivity, power input, sample temperature, and rate of hydrogen evolution as a function of time are recorded simultaneously during millisecond pulses. In addition, elongation, uniformity of heating, and sample temperature are recorded using high speed photography. The behavior of reactor fuels during large power transients has been observed using this apparatus. Properties which have been measured include specific heat, coefficient of expansion, electrical resistivity, phase transformations, heats of decomposition, and rates of hydrogen diffusion.
A Photomultiplier and Amplifier Circuit for Kinetic Spectrophotometry
Authors: Keene J. P. , Black E. D. , Hayon E.
Published: February 2004

The circuit was developed for routine use in kinetic spectrophotometry. It has a 10–90% risetime of less than 100 nsec and can be used to measure transient changes of light intensity of less than 0.1%. The photomultiplier circuit is linear over a wide range of light intensities and the amplifier can drive a 75 Ω signal cable. Variable integration and differentiation time constants and overload protection are provided.
A Multiple Purpose Optical Instrument for Studies of Short Steep Water Waves
Authors: Wu Jin , Lawrence J. M. , Tebay E. S. , Tulin M. P.
Published: February 2004

An optical instrument, utilizing a light reflection principle, has been designed which is capable of determining not only surface slope, but also surface curvature distribution. This instrument has been successfully tested in laboratory studies of wind generated waves. Some sample results are included to illustrate the applicability of the instrument.
Liquid Filled Adjustable Optical Analog of the Human Eye
Authors: Roth Niles
Published: February 2004

Aligning, calibrating, and systems testing of automatic ir optometers are greatly facilitated by using a liquid filled analog of the human eye. Characteristics of the eye analog that render it useful as a test element are (1) corneal refractive power comparable with that of the human eye, (2) spectral transmission properties similar to those of the ocular media, (3) rotatable cornea for simulation of astigmatism of any axial orientation, (4) movable fundus (image screen) to simulate an adequate range of refractive errors, and (5) easily replaceable cornea to obtain different amounts of astigmatism.
Space Charge Effects in Proportional Counters
Authors: Hendricks Robert W.
Published: February 2004

The space charge in a gas filled proportional counter resulting from the slowly moving positive ions as they drift from the central wire toward the outer shell is known to cause a significant change in the position and breadth of the energy peak created by monoenergetic x rays. A quantitative theory for the mean shift is developed and confirmed experimentally.
Methods for the Measurement of the Drift Velocity of Ions in Liquids
Authors: Bruschi L. , Santini M.
Published: February 2004

Two methods for the measurement of the drift velocity of ions in liquids are described in detail. Both the dc voltage applied across the drift length, and the time or delays involved in the methods can be measured with an accuracy better than 0.1%. Moreover the time of flight is deduced with good accuracy from an extrapolation of a linear plot of the ionic current as a function of time. As a result, drift velocity or mobility measurements with an accuracy of 1% or better can be made. Drift velocities from 0.1 up to 3000 cm/sec, in electric fields up to 25 000 V/cm, can be measured.
New Pulse Height to Clock Pulse Converter and its Application to Neutron Dosimetry
Authors: Furuta Yutaka , Kinbara Seturo , Miyakoshi Jun-ichi
Published: February 2004

The pulse height to clock pulse converter is an electronic digital integrator and its application for gamma ray dosimetry (gamma ray pulse dosimeter) has been reported recently. In the present study, a new integration method was adopted for the pulse height to clock pulse converter in addition to its transistorization. The results of its application for neutron dosimetry are also described.
Compensation for Light Source Noise in a Sensitive Dual Wavelength Spectrophotometer
Authors: Chance Britton , Mayer Dieter , Graham Norman , Legallais Victor
Published: February 2004

Double beam (dual wavelength) spectrophotometers generally employ alternating, rather than simultaneous, illumination of a single sample with wavelengths λ1 and λ2 to secure large aperture viewing without optical cross-talk. Although this technique allows the use of phase sensitive detection, which greatly reduces the effect of noise entering the system between light switch and demodulator, it also impairs the system's immunity to lamp noise, as compared to a true differential system, in which λ1 and λ2 simultaneously illuminate the sample. To improve the noise rejection, we have devised a method of compensation which uses a second photomultiplier to monitor the time shared light beam before it enters the sample. The resulting signal is normalized and subtracted from the measure signal in a differential amplifier over a bandwidth including frequencies considerably above the switching frequency fc. Details of design are presented together with experimental data showing that greatly improved performance can be obtained with 450 W xenon and AH-6 type 1000 W mercury arc lamps. In the latter case a 20-fold decrease of low frequency noise is obtained at 280 nm.
A Quadrupole Energy Filter
Authors: Schmidt Conrad
Published: February 2004

The electrostatic quadrupole field can be applied as an energy filter using the telescopic trajectories in a plane normal to the hyperbolic electrodes. Particle dynamics, focusing properties, and energy dispersion are given for instruments with cylindrical or rotational symmetry. The cylindrically symmetric field has unidirectional focusing of the second order, while the rotationally symmetric field has bidirectional focusing of the second order.
Optimum Geometry of Saddle Shaped Coils for Generating a Uniform Magnetic Field
Authors: Ginsberg D. M. , Melchner Melvin J.
Published: February 2004

Saddle shaped coils for generating a field perpendicular to the axis of a cylindrical shell to which the coils are confined can be designed in a compact and easily constructed form. The central magnetic field of such a system and its second derivatives with respect to displacements from the center are given as functions of the coil dimensions, and conditions for minimizing these derivatives are discussed. A coil pair with a length-to-diameter ratio of 2 and circular arcs of 120° will have no second order central field derivatives in any direction.
A Differential Generating Voltmeter
Authors: Polga T. , Sala O. , Douglas R. A.
Published: February 2004

A differential generating voltmeter was developed to operate with the electrostatic accelerator of the Universidade de São Paulo. It has an energy spread of 0.2% for 1 MeV protons. The calibration reproducibility of the system is 0.15% over all the accelerator voltage range and for a time period of eight months. The linearity of the energy calibration curve is 0.1% over the whole voltage range of the accelerator.
Ion Detection Using a Continuous Channel Electron Multiplier
Authors: Yellin E. , Yin L. I. , Adler I.
Published: February 2004

A spiral type continuous channel multiplier was used for pulse counting heavy positive ions. The shape of the output pulses was studied. The pulse risetime was found to be very long and composed of numerous after-pulsing as revealed by the ``staircase'' appearance of the pulse. As a consequence, the count rate capability is greatly hampered. Detection of the positive ions by a catcher foil and collection of the secondary electrons lead to a smooth pulse clean of any after-pulsing and to a greatly improved count rate capability.
Secondary Electron Detection in a Field Emission Scanning Microscope
Authors: Crewe A. V. , Isaacson M. , Johnson D.
Published: February 2004

Operation of a field emission scanning microscope in a secondary electron mode is described. The microscope uses only a field emission electron gun without auxiliary lenses and a silicon surface barrier detector to detect the secondary electron current. Resolution of 100 to 200 Å with beam currents of 10−11 to 10−10 A is reported. Micrographs of a variety of specimens are shown.
An Inexpensive, Easily Constructed Spark Cutter for Single Crystals
Authors: Merrill J. R. , Giovanielli D. , Bright A. A.
Published: February 2004

A spark cutter design which is both versatile and very inexpensive is reported. Complete information on all major parts is included. A novice could build the machine in about four days using the information from the note. The spark cutter reported has been used to cut single crystals of a wide variety of metals as well as to do sophisticated machining jobs.
A Microwave Plasma Density Measuring System with Microsecond Response Time
Authors: Burns Stanley G. , Beyer James B.
Published: February 2004

Based on the STALO (acronym for STAbilization of Local Oscillator) system wherein an external high Q cavity is used to frequency stabilize a reflex klystron, a technique was developed using a microwave Fabry-Perot resonator (MFPR) operating at 35 GHz for performing time varying plasma diagnostics over a two to three order of magnitude range centered at 5×109 electrons/cm3. Experimental results are given for 2 MHz density variations in a 125 μ He rf induced discharge. The frequency response is an order of magnitude faster than an external feedback control system (also described) which utilizes the MFPR. Calibration techniques as well as the underlying theory are also given.
Determination of the Geometrical Factor of Cylindrical Geometries
Authors: Gillespie C. R.
Published: February 2004

An approximation for the geometrical factor of cylindrical geometries which converges rapidly is found.
A Rotating Square Wave Polarizer
Authors: Boros P. , Schwartz R. , Cahill P.
Published: February 2004

A method for determining the polarization of a light source is to observe the transmitted light intensity through a polarizer set at two azimuthal positions with respect to any arbitrary axis. If the polarizer is mechanically rotated at a constant frequency, there are just four angular positions per revolution at which cross extinction occurs and only I∥ or I⊥ are transmitted. We have constructed a rotating polarizer in which either I∥ or I⊥ is transmitted independent of the azimuthal angle for nearly one-half a cycle. Effectively, the transmitted light is square wave modulated with respect to two azimuthal positions of a stationary polarizer which differ by 90°. This rotating polarizer has been exceedingly valuable for precision and efficiency of polarization measurements where on-line computer sampling of experimental data is used.
Linearization of Resistance Thermometers and Other Transducers
Authors: Diamond Joseph M.
Published: February 2004

Given a resistive transducer which responds directly or indirectly to a physical quantity x, it is shown that the relationship may be linearized by linear methods if and only if both the resistance and conductance of the transducer are concave upward as functions of x. This result applies to either deflection output or to null balance output. The application to the common temperature transducers is considered. It is shown that thermistors, linear metals (e.g., copper), and nickel can be linearized in terms of temperature, but platinum cannot be. If linearization is desired in terms of the reciprocal of absolute temperature, then all the above mentioned transducers can be linearized, including platinum. Quantitative results are obtained for all cases.
Low Temperature Crystal Growth Cryostat for Use in Optical and Inelastic Neutron Studies of Rare Gas Solids
Authors: Dyer Ronald H. , Lefkowitz Issai , Martel Peter
Published: February 2004

We describe a cryostat which permits growth, and thermal neutron and visual examination of massive single crystals of the rare gas solids, their alloys, and other low melting point materials. Growth is from the melt at pressures up to 4 atm. Solids have been grown on a germanium substrate in an effort to preselect the desired lattice orientation. Temperature control is within a few hundredths of a degree for extended time intervals in a range of temperature from 65 to 230 K.
A Programmable Impulse Generator for Spin-Lattice Relaxation Time Measurements in High Resolution NMR
Authors: Lalanne P. , Eletr S.
Published: February 2004

This paper describes the design of a precision, programmable impulse generator capable of producing repetitive impulse trains of accurately defined parameters, selectable over a wide range. The generator was conceived for the specific purpose of gating the audio modulation of the applied magnetic field in an HA 100 Varian NMR spectrometer. The basic circuit is much more general, however, and may be used for the generation of a wide variety of impulse trains. The present configuration is capable of producing repetitive trains of one π pulse followed by several equidistant 2π pulses. The width of these pulses, their number, their separation, and the repetition rate of the sequence are independently selectable. The selections may be made manually or by remote control from an on-line digital computer. All times are increments of a basic clock period, derived in our case from the 16.7 MHz crystal oscillator of the spectrometer. Construction is modular and TTL integrated circuits are used throughout for simplicity.
Technique for the Direct Observation of Residual Defect Structures in Explosive Loaded Metal Cylinders
Authors: Foltz J. V. , Altman F. D. , Murr L. E.
Published: February 2004

A new technique has been devised to examine deformation microstructures of thin walled metal cylinders subjected to internal impulsive loading. The cylinders are strained finite amounts but are not carried to fracture. The stressing device uses a rigid stainless steel cell as a container and an explosively driven Lucite core to produce specimens of metals and alloys that have undergone a high strain rate expansion and are in a form amenable to direct observation by transmission electron microscopy. The total strain in the specimen is controlled and loading conditions may be reproduced for comparison of different materials. This approach is particularly well suited to the detailed investigation of explosive forming processes and shock hardening phenomena in cylindrical bodies.
Low Temperature Atomic 3He Beam for Use in a Polarized 3He+ Ion Source
Authors: Vyse R. , Axen D. , Craddock M. K.
Published: February 2004

The production of a polarized 3He+ ion beam by Stern-Gerlach splitting of a neutral atomic 3He beam requires slow moving atoms because of the small nuclear magnetic moment. A miniature supersonic nozzle cooled to liquid helium temperatures has been used to produce intense slow beams of both 3He and 4He. Their measured intensities are 1×1018 and 0.7×1018 atoms/sr. sec, respectively, with corresponding most probable velocities of 310 and 270 m/sec and velocity full widths at half-maximum of typically 50 m/sec.
An Electron Gun For Atomic Beam Recoil Scattering Experiments
Authors: Collins R. E. , Aubrey B. B. , Eisner P. N. , Celotta R. J.
Published: February 2004

A versatile low energy electron gun suitable for electron-atom scattering experiments has been designed utilizing photoetched grids and precision ceramic spacers which stack onto ceramic rods. Diagnostic techniques are described which determine the absolute electron energy to within ±0.1 eV. Electron guns which operate over the energy range 0.1–25 eV with currents up to 10 mA and energy spreads as low as 0.2 eV have been built using the design presented here.
A Fluorescent Backlighting System for Observing High Pressure, Low Temperature Phase Equilibria Phenomena
Authors: Ensign Mark R. , Tully Philip C.
Published: February 2004

An electro-optical system for observing high pressure, low temperature phase equilibria phenomena has been tested at 25 MN·m−2 and liquid nitrogen temperatures. The system consists of a uv source exciting an intracell fluorescent pigment which illuminates the cell interior. The cell is observed by a closed circuit television camera and monitor, and a permanent record is made with a video tape recorder.
A Parallel Plate Electrostatic Spectrograph
Authors: Green T. S. , Proca G. A.
Published: February 2004

A description is given of a new parallel plate electrostatic spectrograph. A parallel plate electrostatic analyzer has been discussed previously, in which particles issuing from a point source on the earthed plate are deflected by the electric field and brought to a focus on that plate, provided the angle of entrance to the field is 45°. This is a simple example of the more general focusing properties of a parallel plate analyzer. From consideration of these properties, it has been found possible to select a given angle of entry into the field for which second order focusing can be attained giving rise to an angular aberration term proportional to (Δθ)3. Uslng an acceptance of ±6° a resolving power of 200 is predicted and has been obtained with a prototype.
Generalized Logic Circuitry for the Control of Coherent Detection Applied to the Measurement of Ultrasonic Pulse-Echo Attenuation
Authors: Leskovec R. A. , Hunter J. L. , Davenport J. M.
Published: February 2004

Coherent signal detection techniques are applied to conventional ultrasonic pulse-echo measuring apparatus to achieve a 20–25 dB improvement in the minimum useful signal. Logic circuitry is described which generates all the reference and trigger waveforms required by the sampling oscilloscope, lock-in amplifier, and other equipment. No other pulse generators are required. Amplitude adjustment of the pulsed rf comparator is determined to be equal that of the echo by a null indication of the lock-in voltmeter.
Circulating Pump for High Pressure and −200 to +400°C Application
Authors: Ruska Walter E. A. , Hurt Lewis J. , Kobayashi Riki
Published: February 2004

The design of a simple mechanical magnetic circulating pump is given. The pump has been used in this laboratory for a wide range of applications. A pump of this design may be immersed in a bath within the temperature range of −200 to over +400°C and will operate at pressures up to 3500 kg/cm2, dependent upon the material of construction. A most significant design feature of the pump is the achievement of both chemical and mechanical cleanliness. No lubrication is required. The pump is self-flushing with no trapping or pocketing of the circulated fluid possible. The pump is durable and reliable for long periods of operation. The drive for the pump is mounted external to the constant temperature bath, which prevents thermal transfer from the drive to the bath or the pump. The design incorporates a permanent magnet.
A Synthesizer-Based 13C NMR Spectrometer with 19F Field/Frequency Lock
Authors: Bartuska Victor J. , Nakashima Thomas T. , Maciel Gary E.
Published: February 2004

Described here is a modification of the Varian HA-100 spectrometer which permits convenient observation of 13C NMR spectra at 25.1 MHz, with field/frequency stabilization based upon a 19F lock at 94.1 MHz. All radio frequencies are derived from a synthesizer. The resulting stability permits efficient storing of repetitive experiments.
An Apparatus for Measuring the Velocity and Energy Flow Direction of Ultrasonic Surface Waves
Authors: Daniel M. R. , de Klerk J.
Published: February 2004

An apparatus is described which can be used to measure the velocity of Rayleigh waves and direction of energy flow throughout any given plane in a piezoelectric material. Some results are presented for part of the X-Z plane in lithium niobate. Additionally, with the use of a thin film transducer the measurements can be extended to non-piezoelectric materials.
Laser Energy and Power Measurement with a Double Reflecting Plate Calorimeter
Authors: Rasmussen A. L.
Published: February 2004

In a double reflecting plate calorimeter, the energy from a laser beam is partially absorbed by metal mirrors. The rest is reflected through an exit where it is free to interact with some medium. Characteristics of this calorimeter with a pair of aluminum plate mirrors are (1) wavelength range ∼0.1−∼1 μ, (2) energy input range ∼0.1−∼50 J/cm2 (pulsed normal mode) and estimated power ∼100−∼1000 MW/cm2 (pulsed Q switched) depending upon energy density, (3) estimated error ±2% over most of the ranges given, (4) 5 sec for the plates to reach a uniform temperature and to make measurements, and 2–4 min required cooling time between inputs, and (5) both absorption and reflection determined from plate calorimetric data. The sensitivity and the wavelength, energy, and power ranges may be increased by using different plate dimensions and materials. Data from an intercomparison between this calorimeter and an NBS liquid cell calorimeter yield agreement of about 0.6% at 0.6943 μ. The light was p polarized (electric vector parallel to the plane of incidence). The energy of the components of polarization parallel and perpendicular to the plane of incidence of a light beam may be evaluated.
Design of an Nd-Glass Mode-Locked Laser with Frequency Doubling and Pulse Selection
Authors: Everett Patrick N.
Published: February 2004

A reliable, passively mode locked Nd-glass laser was developed. The design is described, including provision for frequency doubling with a crystal of KDP and selection of pulses with a Pockels cell. A train of three subnanosecond pulses of light was obtained with individual pulse energies between 1 and 2 mJ, at a wavelength of 530 nm.
A Spectrograph for the Simultaneous Measurement of Velocity Spectra and Charge-to-Mass Ratios of Ions
Authors: Green T. S.
Published: February 2004

The design of a new ion spectrograph is described. Using magnetic deflection, analysis can be made of the velocity spectrum of the ions. For a given entrance angle to the magnetic field the foci lie on a straight line and second order focusing can be obtained. Application of an electric field parallel to the magnetic field causes displacement of the focal line to an extent determined by the charge-to-mass ratio of the ion. The image on the focal plane is thus a set of lines one for each ion species, the velocity distribution being displayed along each line.
A Self-Adjusting Probe Positioner for Measuring Flow Fields in the Vicinity of Wind Generated Water Surface Waves
Authors: Chang P. C. , Gorove A. , Atchley R. L. , Plate E. J.
Published: February 2004

A self-adjusting positioner has been developed for allowing a sensor to measure instantaneous flow properties at a fixed distance from a moving water surface. It thus permits measuring the flow field in the troughs of progressive wind waves, which is essential information for understanding air-water interaction. With the aid of a special statistical technique to sample and average simultaneous recordings of water surface displacements and instantaneous flow properties, such as velocity, pressure, temperature, and humidity, a more complete description of both air and water flows near the interface can be obtained. The probe positioner works on the principle of the classical position servosystem. A capacitance gauge provides the actuating signal which is proportional to the depth of the water below the probe. The dynamic characteristics of the system, as expressed by its transfer function, indicate its applicability for wind waves generated both in laboratories and oceans.
A Method for Preparing Large Area Thin Foils for Transmission Electron Microscopy
Authors: Henry L. F. , Hockey B. J. , Mitchell J. W.
Published: February 2004

A convenient method has been developed for producing thin foils of metals with relatively large transparent areas for transmission electron microscopy. A thin plate with the desired orientation is cut from a single crystal and an accurately oriented plane surface is produced on one side by successive chemical and electrolytic polishing. The specimen is mounted with this side in contact with a glass support and polished in the same way to give a plane parallel plate, about 0.01 mm in thickness. Rings with an external diameter of 3.2 mm and an internal diameter of 1.6 mm are next cemented to the plate. Disks are then cut out, detached, and thinned electrolytically by a micro-window method to give a strip of uniform thickness across a diameter of the rim. The specimen can be transferred to the electron microscope holder without damage and large areas are available for examination.
The Interpretation Error in Molecular Beam Experiments
Authors: Klavins Andrew , Sentman Lee H.
Published: February 2004

This study is concerned with the interpretation of the ionization gauge detector signal in a molecular beam experiment as a particular functional of the reflected molecule distribution function, called the nominal value of the detector signal. The detector configurations examined are those used to measure number density and time-of-flight velocity distributions. Expressions for the actual detector signals are established on the basis of the apparatus geometry; the nominal expressions are derived as approximations to the actual signal. Differences between these actual and nominal functionals are examined quantitatively using the Nocilla reflection model. It is found that in the density case the significant apparatus parameter is the solid angle subtended at the detector by the illuminated target area. If this solid angle is large, the error introduced by assuming the detector signal to be represented by the nominal expression becomes significant when the reflection is highly anisotropic. In the velocity distribution measurement, the significant factor is the shutter function. For slow shutter speeds, differences between the actual and nominal expressions for the detector signal increase rapidly as the error in the time the shutter is open increases.
A Method of Measuring the Mobility of Radioactive Ions
Authors: Huertas M. L. , Marty A. M. , Fontan J. , Lanegrasse L. , Blanc D.
Published: February 2004

We have measured the mobility of ions in air. The method of measuring the mobility is a time-of-flight method. The time of flight of the ions is measured between two grids G1 and G2, as in Bradbury's method. We have improved the resolution of the apparatus, using a rectangular cyclic voltage, and we have eliminated harmonic peaks. Results with radioactive ions of ThC″ and ions created in air by the β rays of a tritium source are discussed.
Accurate Determination of the Dielectric Constant by the Method of Substitution
Authors: Andeen Carl , Fontanella John , Schuele Donald
Published: February 2004

A substitution method for highly accurate determination of the static dielectric constant of solids is presented along with techniques for refining capacitance measurements. The results for some alkaline earth fluorides are CaF2, 6.799; SrF2, 6.466; and BaF2, 7.359; and an alkali halide KCl is 4.818.
A Densitometer Unit Uniquely Suited to Extracting Transient Molecular Absorption Bands from Spectrographic Records of Flash Photolysis Experiments
Authors: Humphrey J. S. , Fielding J. H.
Published: February 2004

The design and operational characteristics of a scanning double beam-dual photometer for simultaneous comparison of two spectrographic density images are described. With a three decadic log ratio device, the photometer-log ratio converter functions as a densitometer unit providing differential density measurements of spectrographic records. The method of analysis has several limitations but the utilitarian value of the dual photometer-log ratio converter unit in extracting molecular absorption bands of metastable molecules as recorded spectrographically in flash photolysis studies is illustrated with results from experiments on flash photochemical production of phenoxyl radical from p-t-butylphenol in hydroxylic media.
A Variable Temperature, Variable Path Length Cell for ir Studies of Liquefied and Solidified Gases
Authors: Silvera Isaac F.
Published: February 2004

A versatile optical cell using light pipe optics with a self-contained detector operating at 1 K for ir studies of solids and liquids that are gases at room temperature is described. The sample length is continuously variable up to 10 cm and the sample temperature can be varied from 1 to ∼200 K.
A Modulation Scheme for Powder ENDOR
Authors: Hyde James S. , Astlind Torbjörn , Eriksson L. E. Göran , Ehrenberg Anders
Published: February 2004

The combination of amplitude modulation of the nuclear rf power at a frequency f1 and 180° modulation of the phase of the resonance microwave signal with respect to the reference microwave signal at a frequency f2, where f1≫f2, with successive amplification and phase sensitive detection at the two frequencies, has proved useful in electron-nuclear double resonance (ENDOR) of unordered solids. The alternative of amplitude modulation alone often results in poor baseline stability, and the alternative of amplitude modulation plus magnetic field modulation results in the complication of summing in an uncontrolled manner ENDOR contributions from crystallites resonating at different fields and with different orientations with respect to the applied dc magnetic field.
Parylene Thin Films for Radiation Applications
Authors: Spivack M. A.
Published: February 2004

Thin parylene films have been prepared and are available in thicknesses to 0.025 μ. The parylene polymers are shown to be extremely uniform in thickness, have good gas barrier properties, and are relatively nonabsorbing throughout the entire soft x-ray region. Comparisons are made with commercially available Mylar, polycarbonate, polypropylene, VYNS, and Formvar.
A Modified Target Current Display System for the Electron Probe Microanalyzer
Authors: Sanecki J. E. , O'Boyle D. R.
Published: February 2004

A new technique has been developed to display the target current image formed in an electron probe microanalyzer. In this method the target current signal from the specimen is converted to a frequency by the use of a voltage-to-frequency converter. The output frequency from the voltage-to-frequency converter is then used to modulate the brightness of a cathode ray tube. This method offers the advantage of allowing the contrast of the various phases in a specimen to be varied electronically, and also results in refined phase definition by creating a contrasting border around certain metallurgical phases of interest.