bluuebunny/crossref_metadata_2025 huggingface dataset:
Thin Fused Quartz Window for Far Infrared Radiation
Authors: Rogoff Gerald L. , Brown Sanborn C.
Published: February 2004

A fused quartz bubble window approximately 0.115 mm thick and several centimeters in diameter has been constructed. It has high far infrared transmittance (∼70–90% for 180 μ<λ<3 mm), can pass a beam of large cross section, and can support a vacuum. The window is a bubble blown inward (convex toward low pressure) to be under tension. Its use avoids the temperature dependent transmission characteristics of crystal quartz, a material often used for vacuum envelope windows because of its high far infrared transmittance. Unlike crystal quartz windows, the fused quartz window can be fused to the envelope. Transmission measurements, lens effects, and reflection losses are discussed.
Current Profile Monitor for Use in Scanning Electron Beam Irradiations
Authors: Okabe Shigeru , Tsumori Kunihiko , Tabata Tatsuo
Published: February 2004

A current profile monitor for the scanning electron beam from the accelerator is described. It utilizes the fact that the electrons scattered through large angles by the exit window of the scanner show a profile similar to that of the main beam at the irradiation site. The scattered electrons are collected by small probes arranged in a linear array parallel to the scanning direction, and the beam profile in this direction is displayed by a storage oscilloscope or an X-Y recorder. This device has been used for electrons of energies 4–16 MeV from a linear accelerator and proved to be useful for continual monitoring with negligible disturbance to the irradiation in progress.
Fast Fission Chamber Amplifier-Discriminator System
Authors: Ingle R. W. , Gillespie F. E. , Weston L. W.
Published: February 2004

To measure the fission cross section of 233U as a function of neutron energy, instrumentation with fast pulse rise-time and short resolving time characteristics is required. The efficient detection of fission-fragment pulses in the presence of a high alpha background requires these characteristics. A fission detector with an electron collection time of 25 nsec and containing 1 g of 233U, and an amplifier with a risetime of 7 nsec and an over-all gain of 1000 were developed for this measurement. This system, detecting the fast rising current pulse from a parallel plate ionization chamber, is an integral part of the instrumentation used by a group at ORNL engaged in the measurement of the neutron fission and capture cross sections as a function of neutron energy. With this system, the fission cross section of 233U was successfully measured over a neutron energy range from 0.4 to 2000 eV.
A Method for Mapping a Toroidal Magnetic Field by Storage of Phase Stabilized Electrons
Authors: Sinclair R. M. , Hosea J. C. , Sheffield G. V.
Published: February 2004

We describe a method for measuring the shape of a toroidal magnetic field (such as in a stellarator) to demonstrate the existence and nature of magnetic surfaces. We detect the successive circuits of a pulse of low energy, phase stabilized electrons injected parallel to the field and stored for many thousands of circuits. We find that the cumulative effect of various field perturbations alters the parameters of the surfaces significantly, but does not destroy them. In certain special cases, there is excellent agreement between the measured and computed field shapes for our specific device. These results and methods are of immediate application to a broad class of magnetic (or other area preserving) mappings. The same experimental technique can also be used for the long term storage of low energy ions.
A Miniature Centrifugal Pump
Authors: Sixsmith H. , Giarratano Patricia
Published: February 2004

A miniature centrifugal pump designed to circulate helium in a flow loop is described. It is designed to operate in the liquid helium temperature range under ambient pressures up to 100 atm (107 N/m2), producing a maximum flow rate of 50 cm3/sec and a maximum pressure rise of 3400 N/m2. The operating characteristics obtained from preliminary tests with cold nitrogen gas and an analysis of the performance are included.
Increasing the Versatility of the General Electric Miniature X-Ray Probe
Authors: Larson John A. , Ziemke William A.
Published: February 2004

Modifications to a commercial miniature x-ray probe are described which allow elemental analysis to be made on diffusion samples with an effective aperture of 15 μ. Elemental concentrations as a function of depth are shown for Al, Nb, and Ta.
Double Discharge Excitation for Atmospheric Pressure CO2 Lasers
Authors: Laflamme Albert K.
Published: February 2004

The problems encountered in the electrical excitation of pulsed CO2 lasers operating at atmospheric pressure are briefly reviewed, with some solutions developed at the Defence Research Establishment Valcartier, and their limitations. A new approach, based on a double transverse discharge technique, has permitted the design of a 3.8 m long laser which delivered up to 9 J/pulse with a peak power of 12 MW. An output energy density of 5.5 mJ/cm3 of excited gas has been achieved.
Observation of Low Level Transient Light Signals with 1 nsec Resolution
Authors: Everett Patrick N.
Published: February 2004

The problem of observing low level transient optical signals, with better than 1 nsec resolution, is discussed. A practical system is described which is limited by shot noise in the photocathode current and by the quantum efficiency. Novel circuitry was developed which automatically reduces the gain of the photomultiplier to avoid damage from excessive average anode current.
Apparatus for the Measurement of Internal Friction Under Hydrostatic Pressure
Authors: Nelson Carl W. , Goettler Hans J.
Published: February 2004

An apparatus is described for the measurement of internal friction under conditions of hydrostatic pressure transmitted by a liquid. The material to be tested is in the form of a helical spring. The motion of this spring under the influence of an axial sinusoidal force is compared to the motion of a reference spring made of a material exhibiting negligibly small losses under the influence of the same force. The phase angle between stress and strain and thus the internal friction in the specimen can be determined by this procedure. External damping due to viscous interaction between the specimen surfaces and the pressure transmitting fluid is kept inappreciably small by employing very low frequencies of vibration (in the order of 1 cycle/min and less). There is no theoretical limit to the lowest frequency that can be used. Strain amplitudes of 10−7−10−5 have so far been realized; values beyond these limits are possible. A simple theoretical analysis of the behavior of the test arrangement is discussed. Some experimental results are presented.
Automatic Measurement of Ultrasonic Velocity Changes
Authors: Parks Jack G.
Published: February 2004

A technique is described for the automatic measurement of ultrasonic velocity changes of one part in 105 in continuous wave experiments. An oscillator is frequency modulated by an analog circuit which terminates frequency change when a mechanical resonance is achieved in an ultrasonic interferometer. Velocity changes appear as changes in terminal frequencies of the oscillator and are easily recorded. A typical result is presented. The possibilities of using the technique to measure temperature changes of 10−3°C and displacements as small as 10−6 cm are discussed.
Self-Switching Damping Circuit for Reducing Transmitter Ringdown Time in High Power Pulse NMR
Authors: Samuelson Gary L. , Ailion David C.
Published: February 2004

In this paper we describe a circuit for reducing the transmitter ringdown time and thereby improving the recovery time in pulse NMR experiments. The circuit uses only solid state devices and requires no external switching. For transmitter voltages less than 0.5 V peak to peak the effective resistance in parallel with the transmitter coil in a crossed coil spectrometer is only 6 Ω, whereas for larger voltages the shunting resistance is of the order of 1–2 kΩ. This circuit thus has the effect of significantly squaring the envelope of an rf pulse. It has the extra advantage of suppressing noise generated by the transmitter during the time interval between pulses.
Oscillating Superleak Second Sound Transducers
Authors: Sherlock R. A. , Edwards D. O.
Published: February 2004

The construction and performance of mechanical transducers suitable for generating and detecting second sound in pure 4He, and also in dilute 3He–4He mixtures at millidegree temperatures, are described. It is shown that when the normal fluid density is small, the behavior of the transducers can be explained by a simple acoustical model which enables their sensitivity, frequency response, and reflection coefficient to be calculated in terms of easily measured parameters.
A Thermostated Glass Stopped Flow System
Authors: Dewald R. R. , Brooks J. M.
Published: February 2004

Construction of an all-Pyrex stopped flow apparatus capable of high vacuum and variable temperature operation is described. The thermostated system is capable of studying reactions from above room temperature to −40°C. The closed system has been used to study the fast reaction of the ammoniated electron with the ammonium ion in liquid ammonia at −35°C.
A Small Tissue Equivalent Automatic Ionization Chamber
Authors: Sims C. S.
Published: February 2004

A quartz fiber electrometer (QFE) dosimeter system has been designed, developed, and tested to demonstrate the applicability of small dosimeters of the Neher type for use as space qualified instruments. The electrometer consists of a 3 mm diam×30 mm cylindrical quartz rod partially coated with Au, and a 10 μ diam quartz fiber coated with Signa-Kote to a resistance between 0.25 and 1.5 MΩ/cm. The 9 cm3 tissue equivalent ionization chamber is filled with 1 atm of C2H4, and consists of the automatic recycling QFE inside a 112 mg/cm2 Signa-Kote coated Delrin electrode and a 103 mg/cm2 Al case. Eight design verification units with various electrometer properties were subjected to tests involving calibration with 60Co for five decades of dose rate, temperature variation from −40 to +82°C, simulated mission vibration and shock, orientation in the earth's gravity field, and gas leakage. The performance of the instruments indicates that they can indeed be developed into meritorious space qualified radiation dosimeters.
New Type of Molecular Mass Gauge for Use with Small Gas Samples
Authors: Kendall B. R. F. , Englehart Gladys
Published: February 2004

Networks can be constructed which consist of chambers interconnected by porous membranes. If a gas sample is suddenly injected into the input of such a network, and free molecular flow conditions apply, the resultant output pressure waveform is characteristic of the injected gas. This principle has been used as the basis for a simple, compact molecular mass gauge with an output reading directly in atomic mass units. Its design, construction, and operation are discussed. Molecular weights can be measured in less than 1 min with a standard deviation of about 1 part in 2500. Sample volumes are typically about 10−1 cm3 but can be several orders of magnitude smaller. Calibration for analyzing two-component gas mixtures is also discussed. Two fundamentally different modes of operation are identified, corresponding to homogeneity and inhomogeneity of the gas within each chamber. It is shown that the latter mode gives a more linear calibration.
An Integrated Deoxygenation Apparatus for Stopped Flow
Authors: Fox J. Lawrence , Schenkkan Dirk M.
Published: February 2004

A deoxygenation apparatus for stopped flow which fits directly into the reservoir syringe inlet of any stopped flow apparatus has been developed. A description of the apparatus, an explanation of other uses which this basic design permits, and a typical kinetic tracing are given.
High Intensity Hot Filament Vacuum Ultraviolet Light Source
Authors: Eastman D. E. , Donelon J. J.
Published: February 2004

We describe a simple modification of a McPherson-Hinteregger-type capillary discharge lamp which converts it from a cold cathode discharge to a hot filament discharge. This results in about a 10-fold intensity increase in the 7–12 eV photon energy range and about a fourfold increase in operating time between cleanings. The spectral output power is presented.
A Versatile System for In-Beam Mössbauer Spectroscopy
Authors: Hardy K. A. , Hicks J. A. , Russell D. C. , Wilenzick R. M.
Published: February 2004

An experimental system for Mössbauer studies following Coulomb excitation or nuclear reactions is described. A drift-free high velocity Doppler spectrometer is incorporated in the apparatus, and a closed cycle helium refrigerator is used for cooling the target and absorber to low temperatures. The system also operates successfully as a conventional Mössbauer spectrometer with radioactive sources.
Cadmium/Sulfur Isothermal Source for CdS Deposition
Authors: Beecham D.
Published: February 2004

This paper describes the theory and construction of apparatus for the vapor deposition of highly resistive, highly oriented, piezoelectrically active cadmium sulfide films from the constituent elements. The cadmium and sulfur are evaporated from a double coaxial isothermal source, the composition of the vapor beam being determined predominantly by the area of an orifice in each source. The source operates at 420°C, and condensation rates of 300 Å/sec are readily obtained. The deposition rate may be varied over a wide range (say, 15 to 1) with little resultant change in resistivity. Films were deposited on fused quartz to serve as electromechanical transducers. A shear mode coupling constant kt of 0.12 was measured. The longitudinal mode signal level was 46 dB below that of the shear mode at the upper 3 dB shear mode frequency. A longitudinal mode kt of 0.12 has been obtained with a shear mode suppression of 60 dB.
Multihundred Watt Nd:YAG Continuous Laser
Authors: Koechner Walter
Published: February 2004

The operating characteristics and design parameters of a high powered continuously pumped Nd:YAG laser are summarized. Primary attention is given to a discussion of some of the limitations in output power and efficiency.
The Use of a Single Plate Interferometer in the Hook Method of Roschdestvensky
Authors: Spurk J. H. , Gion E. J. , Sleator D. B.
Published: February 2004

The theory of a simple inexpensive single plate interferometer coupled to a spectrograph is developed and the feasibility of this instrument in the hook method is demonstrated by observing the anomalous dispersion of sodium vapor. This instrument appears especially attractive for use in the vacuum ultraviolet region of the spectrum.
Microwave Micromanipulator
Authors: Day Howard M. , Cohen Eliot D. , Gleason K. Reed , Macpherson Alan C.
Published: February 2004

A waveguide micromanipulator is described which permits rapid measurement of the microwave detection properties of semiconductor diodes at the slice level. Schottky diodes of various diameters were deposited on an epitaxial silicon slice and the detector sensitivity was measured at 3 GHz. The dependence of detector sensitivity on diameter is shown to be in agreement with the conventional theory of microwave Schottky barrier diodes.
Vibrating Sample Magnetometer for Use at Very Low Temperatures and in High Magnetic Fields
Authors: Mangum B. W. , Thornton D. D.
Published: February 2004

A high sensitivity vibrating sample magnetometer for use at very low temperatures is described. It can be made extremely compact by the use of a piezoelectric element as the vibrator. The complete magnetometer can be placed in the cryostat between the poles of an electromagnet and can be operated at high applied magnetic fields.
A Two-Wire IC Compatible Capacitive Transducer Circuit
Authors: Harrison Dean R. , Kerwin William J. , Schaffer Gregory L.
Published: February 2004

The important features of the transducer bridge circuit considered here are that under certain conditions the circuit output can be made relatively independent of (1) changes in the carrier period, (2) changes in branch resistance, and (3) changes in capacitances due to temperature. Additional features are (4) the circuit is located at the transducer and (5) requires only two connecting leads to the necessary energizing and indicating equipment, and (6) the branch containing the transducer can be balanced by a pure resistor in the other branch. Each of these features is important for integrated circuit considerations. Some pressure transducer assemblies incorporating a hybrid integrated circuit version of the circuit bridge are shown in addition to sample calibrations.
A Dual-Cell Sample System for High Temperature Mass Spectrometric Investigations
Authors: Joyce T. E. , Ridley T. Y. , Grimley R. T.
Published: February 2004

A dual-cell high temperature sample system is described which is designed for use with the mass spectrometer. This device consists of two high temperature furnace assemblies whose temperatures may be independently controlled and which may be interchangeably and precisely located below the entrance slit of a mass spectrometer. This unit permits one to make direct measurements of evaporation coefficients, activity coefficients, and also permits one to make use of more flexible calibration techniques.
An Optical Interferometer Using Polarization Coding to Obtain Quadrature Phase Components
Authors: Bouricius G. M. B. , Clifford S. F.
Published: February 2004

We have demonstrated the feasibility of using polarization coding in an interferometric measurement of optical phase. Phase variations can be followed continuously, relative to the beginning of any desired time interval. Typical phase fluctuations of a laser beam traversing the open turbulent atmosphere are presented.
An Electron Beam Method for Measuring High Sheet Resistances of Thin Films
Authors: Chester A. N. , Kosicki B. B.
Published: February 2004

Measurement of sheet resistances of high resistance (up to 1016 Ω/□) thin films using conventional methods is both difficult and subject to error. We have developed a method for making sheet resistance measurements in which a low velocity electron beam is used to inject charge into the film. The injected charge drifts under the influence of its self-induced field to metal electrodes evaporated on the film, where it is collected and measured externally as a time dependent current. We give examples of thin GaAs films for which the measured current can be fit with a current predicted by a simple model over many orders of magnitude by adjusting only one parameter, the sheet resistance of the film. The good agreement between experimental and theoretical currents provides reliable values for the sheet resistance. This allows an estimation of a lower limit on the carrier density native to our GaAs films.
Stereo Height Measurements in Scanning Electron Microscopy
Authors: Cripps J. B. F. , Sang H.
Published: February 2004

Determination of relative heights from SEM stereo photographs is considered. It is shown that by the choice of suitable geometry it is possible to derive exact formulas for both the case of translating and tilting the specimen. The translation method is shown to be useful for determining the true working distance whereas the tilting method is more sensitive to small height differences. A comparison between exact and approximate (infinite working distance) formulas is made in the specimen tilting case. Experimental requirements are considered and methods are suggested.
An X-Ray Pinhole Camera with Nanosecond Resolution
Authors: Bernstein M. J. , Hai F.
Published: February 2004

A pinhole camera system giving time resolved photographs of the x-ray source in an intense plasma discharge is described. Each pinhole projected an image of the x-ray source onto a sheet of scintillation plastic which converted the x rays into a visible light image that was photographed with an image convertor camera. Use of twin pinholes with appropriate filters and scintillator thicknesses provided some spectral resolution. A spatial resolution of 2 mm was achieved with a time resolution of 10 nsec.
Magnetic Field Calculations for Thick Solenoids
Authors: Merrill John R.
Published: February 2004

This paper describes a simple computer program which calculates the magnetic field B inside the bore of any system of coaxial uniform current density solenoid of rectangular cross section using Garrett's method [J. Appl Phys. 22, 1091 (1951)]. Two versions of the program exist, the first in the Dartmouth form of the language BASIC, the second in the language FORTRAN IV. Both versions are ideally suited to modern digital computers, including time shared computers. Copies or listings of the programs are available upon request. The programs are based on those used to design a miniature superconducting magnet for dip experiments.
A Simple Submicrosecond, High Intensity Flash Lamp
Authors: Pfeil A. , Porter G. B.
Published: February 2004

A high pressure nitrogen flash lamp is described which has a half-height width of less than 200 nsec and a light output of more than 5×1014 quanta/pulse.
An Automatic Data Acquisition System for Calorimetry: The Specific Heat of α-Al2O3 between 300 and 470 K
Authors: Martin Douglas L. , Snowdon Robert L.
Published: February 2004

The data acquisition system, using a commercially available automatic ac bridge, digital voltmeter, and transistorized digital logic modules, is suitable for both discrete and continuous heating calorimetry. The output, via a Teletype, is a printed record and punched paper tape. The total cost of parts was less than $25 000. The computer program to handle the output is described. As an illustration of the operation of the system the results of measurements in the range 300–470 K on the calorimetric standard sample α-Al2O3 are given. The measurements, having a precision of ±0.1%, were made in an improved form of the calorimeter described by Martin and Snowdon [Can. J. Phys. 44, 1449 (1966)]. Agreement with the latest National Bureau of Standards results (Ditmars and Douglas) is around 0.1% when they are corrected to the same temperature scale. The effect of heater lead resistance on the results has been experimentally determined.
Apparatus and Methods for the Precise Determination of Boltzmann Temperature
Authors: Corson Bayard R.
Published: February 2004

Apparatus and methods have been devised for the rapid and precise determination of the Boltzmann temperature of oxide coated cathodes in scanning beam tubes. The measuring apparatus comprises a digital voltmeter connected between cathode and collector of the tube under test by means of a high input resistance amplifier connected to have unity gain, and a variable shunt from cathode to collector consisting of tap switches and 20 precisely calibrated resistors having values from 104 to 2×1010Ω. The 19 temperatures determined by the 20 retarding potentials measured with this apparatus are computed on a GE 265 calculator. The interfering side effects which are encountered in practical measurements, viz., contact potential drift, contact potential instability, Ohmic and non-Ohmic leakages, collector thermionic and photoelectric emission, heater-to-collector emission, and interelectrode potential minimum, nonuniform geometry, and poorly activated cathodes, are discussed, and the means taken to overcome these effects described in detail. The use of a magnetic field parallel to the electric field to effect collimation is described. It is shown that a very high field may be required to obtain the correct temperature in tubes with nonuniform geometry. It is estimated that in most cases the electron temperature can be measured with an absolute probable error of 1.7°, and that the relative probable error is approximately an order of magnitude lower.
Energy Resolution of the Photoemission Analyzer
Authors: DiStefano T. H. , Pierce D. T.
Published: February 2004

Resolution in the photoemission energy analyzer is investigated theoretically for the case of a finite emitter in a spherically symmetric retarding field with a magnetic field present. Resolution errors shift and broaden structure in measured energy distribution curves by an amount which is energy dependent. The analysis is applicable to the spherical capacitor analyzer, the screened emitted geometry, the multiscreened LEED system, and others. Electrolytic tank measurements show field distortions caused by a flat emitter, the emitter support, and the window aperture. Spherical symmetry is restored to a configuration with a large emitter or support structure by surrounding the emitter with a screened, field-free region. An explanation is given for the reasonable resolution obtained for any small emitter completely enclosed by a collector. Distortion of measured electron energy distributions caused by reverse photoemission, reflected electrons, and fringing fields at the emitter is also discussed.
An Electromechanical Feedback Device for Fine Control of a Platform Position
Authors: Bird H. M. B. , Dixon G. C. , Knowles J. W.
Published: February 2004

The thermal expansion or magnetostriction of wires controlled by a feedback circuit is used to compensate for the effect of environmental disturbance on a movable platform. The system provides linear control of the platform position to plus or minus a few angstroms and angular control to plus or minus a few milliarc-seconds.
A Miniature Pulsed Light Source and Applications to Particle Detector Design
Authors: Ely J. T. A. , Ringle J. C.
Published: February 2004

An alpha emitter (241Am) deposited externally as a thin source on a small NaI(Tl) crystal has been employed as a miniature light pulser. Applications include photomultiplier tube calibration and stabilization, and high precision light collection efficiency mappings for design optimization of scintillation and Čerenkov detectors. Improved resolution has been reported by Menefee and Cho [IEEE Trans. Nucl. Sci. NS-13, No. 3, 159 (1966)] for NaI(Tl) crystals doped internally with 241Am.
An Apparatus for the Measurement of Dichroism in a Pulsed Electric Field
Authors: Allen F. S. , Van Holde K. E.
Published: February 2004

An instrument is described for the measurement of the dichroism produced in solutions of macromolecules by pulsed electric fields. Measurements can be made with monochromatic radiation in the wavelength range from 240 to 600 nm. The pulse generation equipment employed is similar to that used by previous workers but the optics and signal detection system are novel and allow a direct measurement of the dichroism. The relation between the output signal of the apparatus and the dichroism of the sample is derived. Representative experimental data from a study of tobacco mosaic virus are presented to demonstrate the performance of the apparatus. Limitations of the instrument are noted and possible improvements are discussed.
Simultaneous Q-Switching of Two Independent Ruby Lasers
Authors: Faries D. W. , Shen Y. R.
Published: February 2004

Simultaneous Q-switching of two independent ruby lasers has been achieved by a single rotating prism. Frequencies of the two lasers are independently tuned. A difference frequency in the range of approximately 0–50 cm−1 could be obtained.
A Method for Subnanosecond Pulse Measurements of I-V Characteristics
Authors: Jantsch Wolfgang , Heinrich Helmut
Published: February 2004

A method for subnanosecond pulse measurements of I-V characteristics is described. The sample is mounted at the end of a transmission line and the incident and reflected pulse is observed. In this way the sample resistance is compared with the known impedance of the coaxial transmission line and no current measuring series resistance is needed. Short pulse risetimes (170 psec) are obtained and difficulties which arise from the current measuring resistor, like temperature dependence and nonlinearity at high currents, do not obscure the measurements.
A Stabilized 70 Gc Plasma Interferometer
Authors: Cummins W. F.
Published: February 2004

A 70 Gc microwave interferometer for plasma density measurements has been constructed which separates the time varying amplitude and phase signal components induced by the plasma. A superheterodyne technique is used with amplitude limiting and phase detection at the 30 Mc intermediate frequency. Amplitude detection is performed prior to limiting. Phase stability is achieved by locking the local oscillator frequency to the sum or difference of the master oscillator and intermediate frequencies with an AFC loop.
Time Saving in Measurement of NMR and EPR Relaxation Times
Authors: Look D. C. , Locker D. R.
Published: February 2004

By producing a train of absorption or dispersion signals (continuous-wave magnetic resonance) or free induction decays (pulsed magnetic resonance) it is possible to save time in spin-lattice relaxation measurements due to the fact that it is not necessary to wait for equilibrium magnetization before initiating the train. The relaxation time may be calculated from the train according to a simple rapidly converging iteration.
Spectrographic Errors in Pulsed Discharges
Authors: Wright William H.
Published: February 2004

The method of electronically processing the detector signal can be critical when making spectrographic measurements on a pulsed discharge. The output of the commonly used synchronous detector is dependent on both signal amplitude and signal pulse shape, and, when the shape of the radiated light pulse varies with wavelength, serious errors can be introduced. Two disparate spectrograms are shown that were taken from the same light source, differing only in signal processing, and the reasons for the discrepancies are explained. When taking spectrograms of pulsed light sources where afterglow effects may result in a variable pulse shape, it is recommended that the synchronous detector not be used; if the resultant spectrogram is to be power vs wavelength, then some form of signal sampling should be used instead. A measurement technique using a sampling oscilloscope for signal processing is described. A curve is included that predicts the magnitude of error introduced when using the synchronous detector to process a rectangular pulse-exponential decay signal. The error discussed does not exist when studying a mechanically chopped continuous light source since the pulse shape then depends only on the chopper and is invariant.
Velocity Measurement of Slowly Moving Surfaces Using an He–Ne Laser Heterodyne System
Authors: Ippolito S. J. , Rosenberg S. , Teich M. C.
Published: February 2004

A simple and compact laser Doppler radar system capable of high resolution velocity measurements of a slowly moving surface is described. The system is nondestructive and does not contact or interfere with the object whose speed is to be measured. All required beam splitting and reflective surfaces are integrated in a solid crystal block, greatly simplifying alignment. Experiments are performed using a rotating scattering wheel in which velocities as low as 0.21±0.02 mm/sec have been measured.
An Environmental Mean Radiation Temperature Meter
Authors: Strong John , Hopkins George W.
Published: February 2004

The theory for a radiation meter with freedom from necessity for convection cooling correction is developed, and a parameter, the ``mean radiation temperature,'' is defined. An experimental demonstration of the use of the meter is described and discussed. Examples of applications are given.
A Crossed Field Velocity Analyzer for Plasma Ions
Authors: Bastian C. , Cosler A.
Published: February 2004

A crossed electric and magnetic field analyzer has been developed to select ions of a given mi/q ratio and record their velocity distribution. The initial velocities of the ions are mainly directed along the magnetic field of the analyzer; the detection is performed in a plane perpendicular to it. The ion optical properties of the analyzing structure and its sensitivity to space charge effects are illustrated by the synoptical recordings of the velocity distributions of protons leaving a conical theta pinch plasma accelerator. The velocity spectrogram appeared on an ion sensitive plate positioned in the detection plane, showing a series of well focused images of the inlet. In some cases, the particle density in the proton beam could be deduced from the features of the spectrogram.
Single Photon Counting Pileup Corrections for Time-Varying Light Sources
Authors: Davis C. C. , King T. A.
Published: February 2004

Data obtained in a single photon counting experiment used to observe weak decaying light sources, for instance in lifetime measurements, are distorted at high count rates. It is shown that the data can be corrected either theoretically or by an experimental modification.
Stereo Reading Apparatus with Redundancy
Authors: Clark A. F. , Hansen N. E. , Smith D. E.
Published: February 2004

A stereo apparatus for cloud chamber pictures has been developed which uses four cameras to give six possible stereo pairs. Comparison among the various views permits positive identification and measurement of every track in the chamber, even with a large number of tracks.
A High Impedance ac Hall Effect Apparatus
Authors: Olson Eugene E. , Wertz John E.
Published: February 2004

Measurement of the Hall effect in oxide crystals of high resistivity has been made possible by the use of a very high impedance ac apparatus. The shunt capacitance of leads degrades the input impedance in such a system. However, this effect is minimized by driving the shield of the coaxial line from a low impedance source with a voltage of the same amplitude and phase as that of the input signal. The frequency is chosen sufficiently high to minimize the effects of space charge.
Characteristics of the Trochoidal Electron Monochromator
Authors: Stamatovic A. , Schulz G. J.
Published: February 2004

An electron monochromator for use in an axial magnetic field is described. Electrons are injected parallel to the magnetic field and an electric field is applied in a perpendicular direction. The electrons thus describe trochoids and drift in a direction perpendicular to both the electric and magnetic fields and disperse according to their initial velocities. An electron energy width at half-maximum of 0.020 eV can be obtained, with a transmitted current of about 10−9 A.
Ratio Pyrometer for Use in Q-Machines
Authors: Guilino E. , Müller P.
Published: February 2004

A new ratio pyrometer is described the indication of which is proportional to the ratio of intensities of thermal radiation emitted by an incandescent object into two narrow spectral bands within the visible region. The ratio is computed automatically and continuously by servoattenuating the entire incoming light flux in such a way that the intensity in one of the two passbands is kept constant, regardless of the intensity of the incoming light. Due to its basic principle the instrument reading is independent of the magnitude of the target emissivity. In the present setup, temperature differences of the order of 1 deg can be resolved in a temperature range between 1400 and 2900 K. Thus, the pyrometer is especially suited for investigation concerning plasma confinement in Q-devices.
Improved Apparatus for the Measurement of Absolute f-Values
Authors: Bell Graydon D. , Tubbs Eldred F.
Published: February 2004

The absolute oscillator strengths of the ground state transitions of metallic elements can be determined by measuring the optical absorption from a continuous spectrum in a beam of the evaporated material. The apparatus makes use of synchronous detection for the optical signal and a pivotal microbalance for the determination of beam density. This form of microbalance does not require the usual magnetic damping and thus permits accurate measurements to be made on ferromagnetic materials.
A Sensitive Nonmagnetic Pressure Transducer for Use at Very Low Temperatures
Authors: Landau J. , Tough J. T. , Brubaker N. R. , Edwards D. O.
Published: February 2004

A sensitive diaphragm-type pressure transducer suitable for use at very low temperatures is described. The device is useful over the differential pressure range of −200–+200 Torr at ambient pressures up to 20 atm. Differential pressure deflects the prestressed diaphragm causing a change in capacitance between a gold layer on the diaphragm and a fixed plate. The transducer can easily resolve changes of 10−3 Torr in pressure. The method of constructing the device is described in detail.
Sampling and Averaging Techniques in the Analysis of Fast Random Signals
Authors: Amsel G. , Bosshard R.
Published: February 2004

Problems arising when averaging fast signals random in shape and occurrence time are systematically examined. A setup is described, comprising a sampling oscilloscope and a memory unit, allowing high speed random operation. The system logic, which insures one-to-one delay-channel correspondence under the most stringent conditions, allows averaging signals satisfying various specified conditions and optimizes the statistical accuracy of the results. An add-subtract method allows elimination of synchronous transient noise, either external or arising from the sampling unit itself. Signals of 30 μV were averaged out in this way with a 0.1 nsec instrumental risetime. Applications are shown to a broad range of problems which include fast signal enhancement, optical signal measurements, photomultiplier single electron response studies, illumination function measurements for fast organic and slow scintillators, and semiconductor detector risetime observation. Two-dimensional representation of random signal properties is also shown. It allows, for example, time jitter determinations with some tens of picosecond precision. The setup allows direct measurement of noise correlation and cross correlation functions.
A Small-Tipped Microelectrode Designed to Minimize Capacitive Artifacts during the Passage of Current through the Bath
Authors: Schwartz Tobias L. , House C. Randall
Published: February 2004

In the presence of an electrical current through the bathing medium, the measurement of electrical potentials in solution with glass micropipettes is characterized by an error. This error is very troublesome when glass microelectrodes are used to sense the membrane potential during voltage clamping. The source of the error is identified and discussed. The construction of a microelectrode that minimizes the error is described in detail.
Stress Dynamics in High Speed Piezoelectric Pressure Probes
Authors: York Thomas M.
Published: February 2004

In the design of high speed piezoelectric pressure probes the criterion of matching the acoustic impedance of elements in the stress transmission system composed of piezoelement and backing rod is found to be inconsequential. Analysis and empirical evaluation of a typical probe configuration indicate that optimum probe performance can be achieved by utilizing backing rod material with minimum lateral strain (ν/E) characteristics so as to serve effectively to damp induced radial stress oscillations in the piezoelement.
An Automatic Ellipsometer for Use in Electrochemical Investigations
Authors: Greef R.
Published: February 2004

An automatic ellipsometer based on the principle of measurement of intensities is described. Use is made of a rotating analyzer with a three-channel strobing voltmeter to read the photomultiplier output at chosen analyzer angles. The outputs are recorded in digital form, and the time for one optical measurement is 150 msec. Sources of error and ways of eliminating noise from the signal are discussed. The system incorporates a cell specially engineered for electrochemical investigations, and its performance is illustrated with results from an experiment on the electrochemical formation of a thin oxide layer on platinum.
A Rugged, Stable, Differential Platinum Resistance Thermometer
Authors: Kleven Lowell , Lofgren Lyle , Felsenthal Peter
Published: February 2004

A new stable platinum resistance thermometer, and the methods of construction, calibration, and testing are described. The design provides a differential (±2 K) thermometer over the range of 200 to 270 K. After environmental testing, the thermometer has demonstrated differential stability of better than ±1×10−3 K over one year.
Boxcar Integrator Attachment for Oscilloscopes
Authors: Swain David W.
Published: February 2004

A simple circuit that can be used to improve the signal-to-noise (S/N) ratio of a repetitive signal is described. Major simplifications in the circuit design are achieved by use of the amplifying and timing circuits of an oscilloscope to generate the input and timing signals for the boxcar integrator. The device can improve the S/N ratio of the input signal by better than 35 dB. It is usable over the 100 Hz-160 kHz frequency range.
Low Temperature Silicon Thermometer and Bolometer
Authors: Bachmann R. , Kirsch H. C. , Geballe T. H.
Published: February 2004

By simple diffusion and etching procedures low temperature sensitive surface layers can be prepared on otherwise insulating silicon substrates. Temperature coefficients of the resistance of these layers of the order of unity can be obtained at any temperatures below 20 K. The usefulness of this silicon device as a low temperature thermometer and bolometer is demonstrated.
Simple Fatigue Machine for Wires and Foils
Authors: Benedetti R. L. , Creighton D. L.
Published: February 2004

A simple fatigue machine suitable for testing wires, filaments, foils, and other specimens of small cross section has been designed and built. The axial-load machine applies an alternating stress about a tensile mean stress and is of the constant amplitude of force type utilizing electromagnetic loading. One data curve for commercially pure titanium wire is presented to demonstrate the performance achieved.
Sample Preparation for Ferroelectric Switching Measurements
Authors: Plumlee Ralph H. , McLachlan Wilbur D.
Published: February 2004

Small thin fully electroded disk samples (e.g., 0.05 cm diam by 0.01 cm thick) are necessary for measurements of ferroelectric switching times less than 50 nsec. Techniques are described for forming and processing such disks. Electroded disks are suspended by the lead wires in an oil filled electroded cell for ease and reliability in handling. The cell technique allows high field switching measurements on a large range of sample sizes for determination of dimensional effects.
Real Time Laser Propagation Data Analysis Technique
Authors: White Kenneth O. , Schleusener Stuart A.
Published: February 2004

A new technique for real time analysis and display of pulsed laser propagation data is described and initial test results of the method are presented. The technique centers around the use of a dual parameter, pulse height analyzer to record and display data in a rectangular X-Y field. The display gives a real time visual indication of the quality of the test results. It is shown that the emission from long pulse ruby and erbium lasers can be analyzed and displayed in the proposed manner.
A Simple High Performance Triode Sputtering Module for Very Low Pressure Applications
Authors: Seguin H. J.
Published: February 2004

The design, construction, and operational characteristics of a simple low pressure sputtering module are presented. This device which is of the triode configuration has proven to be unusually reliable and has consistently produced films of metals, semiconductors, and insulators having excellent physical, electrical, and optical properties.
A Laser Interferometer Schlieren System for High Frequency Gas Density Measurements
Authors: Burton Rodney L. , Slaybaugh John C.
Published: February 2004

A modification of the Ashby-Jephcott laser interferometer is described, by which both interferometric and schlieren information from an unsteady gas flow can be recorded at rates up to 5 MHz. The laser interferometer schlieren system (LIS) facilitates interpretation of the fringes recorded by the Ashby-Jephcott system by recording both fringe and density gradient information in time. Use of the LIS is described in measuring ρ(t) for the shock and subsequent expansion flow from an open ended shock tube in air.
Conductive Rubber Pressure Transducers for Fluids Research
Authors: Kavrak Ibrahim
Published: February 2004

In the following, an account of the research and development for a new technique of pressure measurement in fluid flow is given. Performances of various pressure transducers using conductive rubber as the sensing element have been investigated. Transducers believed to be the smallest of their kind have been manufactured, with sensitivity high enough to record ordinary speech level pressure variations (about 60 dB) in the af range.
A Magnetic Solenoid Electron Transporter
Authors: Kotajima K. , Beringer R.
Published: February 2004

A magnetic solenoid electron transporter has been constructed to investigate conversion electrons produced in a target by the bombardment of heavy-ion beams. It measures 32 cm in diameter, 124 cm in length, and weighs approximately 290 kg. The target is located at the center of the magnet so that the emitted electrons can be transported toward either end and their energies measured in Si(Li) counters. The energy resolution (for the 624 keV line of 137Cs) and the over-all detection efficiency (for the energy range between 500 and 1200 keV) have been determined to be 6.9±0.2 keV and 6.0±0.4% for a 110 mm2 counter, and 22.0±0.9 keV and 16.0±1.1% for a 500 mm2 counter. This distortion of the energy spectrum for the same energy range is less than 7%.
Generation of Ultrafine Aerosols with a Transpiration Cooled Anode in a High Intensity Arc
Authors: Pfender E. , Boffa C. V.
Published: February 2004

In this paper a new method is described for the generation of monodisperse ultrafine aerosols using a transpiration cooled graphite anode in a high intensity arc operated in argon at atmospheric pressure. Electric current and transpirant mass flow rates are identified as decisive parameters for observed particle size distributions. The results indicate the potential and flexibility of this new method for generating well controlled monodisperse ultrafine aerosols.
A Method of Obtaining High Plasma Temperatures Using Pulsed Constricted Arcs
Authors: Morris J. C. , Morris R. U.
Published: February 2004

A simple method of pulsing constricted electric arcs to high power inputs is described. Using this method, peak power inputs six times greater than can be run continuously have been achieved. An analysis of this method has been made for argon to determine the maximum temperature to be expected as a function of arc channel diameter and generator construction material. In addition, a number of methods used for electric and spectroscopic diagnostic studies of the pulsed high current arc column are discussed.
A Radial Disk Velocity Selector for Molecular Beams
Authors: Cowley L. T. , Fluendy M. A. D. , Lawley K. P.
Published: February 2004

A molecular beam velocity selector is reported in which the beam passes diametrically across a rotating slotted disk. Alignment is checked without reference to assumptions about the source velocity distribution. The selector is compact, easily constructed, and is mounted directly on the driving motor shaft.
Arc Source for Spectroscopic Measurements of Isothermal Plasma Samples at Various Pressures
Authors: Klein Lothar
Published: February 2004

A wall stabilized arc is described which incorporates new design features in order to increase the versatility of this source for quantitative spectroscopic measurements, extending its useful range to lower pressures and to the study of molecular gases. Spectral measurements of different arc portions can be made radially and compared with measurements along the arc axis. It was thus established that in end-on measurements of argon arcs an essentially homogeneous plasma is viewed by the spectrometer.