bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Spinning Zeeman Modulation in Microwave Spectroscopy with Cosine Distribution Magnets
Authors: Woods R. Claude
Published: February 2004

The technique of field spinning Zeeman modulation in microwave spectroscopy has been extended to long cylindrical absorption cells by using orthogonal pairs of cosine distribution magnets. This magnet configuration permits economical application of the field spinning approach to rather long path length, large diameter cells with substantial homogeneity of the field. Fields adequate for microwave spectroscopy may be obtained even within a metallic (preferably austenitic stainless steel) cylindrical vacuum chamber. The solutions of Maxwell's equations for an idealization of the latter situation of an intervening conducting layer are presented, so that with the formulas given here, one may easily calculate available field as a function of geometry, amplifier power, modulation frequency, and circuit parameters. Two new microwave spectrometers have been constructed using such magnets, and our experiences with applying the field spinning technique to them will be discussed. Because the absorption cells are discharge tubes, we will consider the effects which the presence of the plasma has on the field spinning modulation method. While the plasma does give rise to the complication of a nonflat base line, it will be demonstrated that this can be held to quite manageable levels over a wide range of conditions. The spurious baseline fluctuation is likely to be observed in other configurations of Zeeman modulation of a plasma sample and appears to be related to a modulation of the plasma density and the resultant change in its refractive index.
A Microwave Spectrometer with an Internal Glow Discharge
Authors: Woods R. Claude
Published: February 2004

A microwave spectrometer which utilizes the positive column of a dc glow discharge as its sample region has been constructed and operated successfully. This instrument employs free space microwave propagation through a large industrial Pyrex pipe, along with Zeeman modulation, and is intended for the study of transient paramagnetic molecules which are likely to be found in active discharges. This spectromenter features no mechanical tuning, instantaneous broad band width, resolution limited by Doppler broadening, and sensitivity comparable to that of conventional Stark modulated waveguide cells. Extensive observations primarily of the microwave spectrum of the OH radical in a water vapor discharge, have been made in order to delineate the range of application of this technique and to determine the effects of various operating parameters on the spectrum observed. Although the glow discharge is an extremely complicated phenomenon and is capable of manifesting its complexities in the behavior of our spectrometer, a wide range of conditions exist in which the presence of the plasma in the transmission path has negligible impact on the microwave spectrometer signal. Theoretical considerations of basic plasma physics will be employed to support the proposition that this is not unexpected and that a wide range of microwave spectroscopic studies of plasma samples are possible.
A Sampling Unit for an X - Y Recorder
Authors: Smith Todd I.
Published: February 2004

An inexpensive sampling circuit is described which allows high frequency repetitive signals to be plotted on an x - y recorder. The minimum sample width of 100 nsec is short enough that the effective high frequency 3 dB down point is about 6 MHz. The circuit includes provisions for signal averaging which allows significant improvement in the signal-to-noise ratio in many situations.
Design of a Thermal Reference System for Use in Thermography
Authors: Charles John A. , Francis John E.
Published: February 2004

Increased interest in the use of the scanning infrared camera as both a diagnostic and research tool by the medical profession has led to the need for an external temperature reference. The scanning infrared camera detects the infrared radiation leaving a surface and converts the energy into a visual image which is photographed and termed a thermogram. This paper presents a thermal reference made by constructing an extended surface or fin in such a way as to produce a linear temperature profile down the fin axis. A fin was made following the theoretical model and tested. The resulting fin was quite linear and provides an excellent thermal reference.
Analytical Fit of the Transfer Function of a Logarithmic Electrometer and Correction for Ambient Temperature Variations
Authors: Huggins Raymond W.
Published: February 2004

An analytical fit has been derived for the transfer function of a logarithmic electrometer utilizing a p-n junction diode as a feedback loop element. Elementary semiconductor theory has been used to describe the diode current-voltage characteristic, and the diode ohmic resistance and an external parallel resistance have been included in the circuit analysis. A temperature correction has been applied to account for a difference in the temperature of the diode during calibration and during the taking of data. The analytical fit with temperature correction is believed to be accurate to better than 10% of the absolute current input over seven current decades.
A Method of Measuring Thermal Conductivity in the Presence of Extraneous Heat Currents and the Thermal Conductivity of Brass at Low Temperatures
Authors: Cappelletti R. L. , Ishikawa M.
Published: February 2004

A modification of the absolute, longitudinal, steady-state method of measuring thermal conductivity at low temperatures using one calibrated thermometer is described. By this method the effects due to any type of constant extraneous heating are completely canceled. The method is applied to measure the thermal conductivity of machined brass between 0.3 and 2 K.
An Optical Distance Measuring Instrument
Authors: Payne John M.
Published: February 2004

This paper describes an instrument that measures the transit time of a modulated light beam out and back over the path whose length is required. The instrument has a digital readout and an rms (1σ) accuracy of ±0.08 mm on a single measurement over ranges up to 60 m. The measurement time is 2.7 sec.
An Automatic Recording Device for Zimm-Crothers Viscometer
Authors: Bernengo J. C. , Marion C. , Roux B.
Published: February 2004

A high precision, easy to build, digital recording system has been adapted on a commerical Zimm-Crothers rotating viscometer. It allows intrinsic viscosity measurements on very diluted nucleic acid solutions.
High Temperature Density Measuring Apparatus Using the Photon Attenuation Technique
Authors: LeVert F. E. , Dillon I. G. , Tarng H. J.
Published: February 2004

Equipment has been designed and developed that allows one to use the gamma attenuation technique to measure the densities of metals at high temperatures. Saturated liquid density values have been measured from room temperature up to 1841°C. The density values obtained by this technique compare very well with those measured by other methods.
A Nanovolt-Level MOSFET Reversing Switch for Low Temperature Applications
Authors: Anderson Jack R. , Zrudsky Donald R.
Published: February 2004

A remote reversing switch is presented, which is operable at low temperatures and useful for eliminating thermal lead voltages by means of an average. It utilizes four n-channel enhancement mode MOSFET's with the channels connected in a balanced bridge configuration. Input signal reversal is achieved by gating on alternate pairs of transistors. The use of sapphire heat sinks for all channel leads is critical to the achievement of a switch resolution of better than ±2 nV, measured at 4.2, 77, and 300 K. The switch was also used as a remote chopping element for a phase-synchronized dc to ac inversion, again at 4.2, 77, and 300 K with resolution approaching the limits of the equipment used to test its performance. The small size, infinitesimal power dissipation, predicted immunity to large magnetic fields, and almost perfect isolation of the driving circuit from the desired signal makes this reversing switch superior to any other device which has previously been used for such purposes.
Derivation of Second Order Geometric Factor G
Authors: Kan J. T. C.
Published: February 2004

The geometric factor G is a major parameter in determining differential cross sections with a gas target. Silverstein has calculated G for several detector aperture geometries with a finite sized, but parallel incident beam. Critchfield and Dodder have calculated G for a parallel-edge front aperture and circular back aperture with a divergent incident beam. In this article, G is calculated for a parallel edge front aperture and a rectangular back aperture with a divergent incident beam. The present calculation follows the method outlined by Critchfield and Dodder and employs a convenient combination and slight modification of their notation and that of Silverstein.
Optical Fiber Breaking Stress Distributions Obtained by a Cantilever Method
Authors: Saunders M. J.
Published: February 2004

A description is given of a cantilever apparatus to determine the mechanical strength and elastic modulus of optical fibers. This test method overcomes the problem of fiber breakage in the jaws of tensile machines. Young's modulus, the breaking stress distribution, and values of the breaking radius of curvature and strain are presented for fused quartz fibers.
Elimination of Need for Special Purpose Switches in Accurate Four-Terminal Circuitry
Authors: Zair E. , Greenfield A. J.
Published: February 2004

An arrangement is suggested which avoids the need for specialized, high-priced, bulky switches in four-terminal resistance circuitry.
Temperature Control Using a Platinum Resistance Sensor
Authors: Brabson G. D. , Fannin A. A.
Published: February 2004

A platinum resistance sensor can be used in conjunction with a resistance bridge to generate an error signal that is proportional to the difference between the actual and desired temperatures. The magnitude of the error signal, 0.4 mV/°C, is 10 times that generated by a Chromel-Alumel thermocouple.
Differences Between ac and dc Determinations of Germanium Thermometer Resistances
Authors: Swenson C. A. , Wolfendale P. C. F.
Published: February 2004

The resistances of several germanium thermometers are found to differ for ac and dc measurements. At 300 K, these differences are frequency independent from roughly 5 to 103 Hz. The ac resistances always are smaller, and the approximate temperature differences (Tdc − Tac) vary from 100 mk at 77 K to 0.2 mK below 17 K.
Inexpensive High Vacuum Feedthroughs
Authors: Gerber S. , Post D.
Published: February 2004

Rigid coaxial cable has been used to construct simple, inexpensive high vacuum coaxial and coaxial push pull rotary motion feedthroughs.
A Pulse Amplitude to dc Voltage Converter
Authors: Yamashita Mikio
Published: February 2004

A simple instrument is described which provides a dc voltage corresponding to the amplitude of a pulse train. The instrument permits measurements of input pulse amplitudes with an accuracy of [inverted lazy s] 0.1%.
A Compact Demountable Superleak - Tight Seal for Low Temperature Experiments
Authors: Little Roger E. , Liu Yu
Published: February 2004

A technique for applying and removing a superleak - tight epoxy seal is described. The advantages of the seal are that no heat or pressure is required to make the seal.
An Optical Absorption Cell with Vapor Cross Flow
Authors: Hendrickson P. E. , Walls W. L. , Broersma S.
Published: February 2004

In order to avoid wall contamination, and to simulate an open air system, a water vapor cross flow instrument has been designed. Vapor equilibrium is established within 30 min. A 6.3 μ infrared beam traverses the pressure, temperature, and humidity controlled vapor column. The effect of these thermodynamic parameters can be examined.
High-Resolution Polarizing Microscope for the Observation of Magnetic Structures at Low Temperatures
Authors: Kirchner H.
Published: February 2004

A polarizing microscope is described, in which solid state samples can be cooled down to liquid-helium temperatures and can be observed with a resolution of the order of 1 μ. By means of this microscope and thin magneto-optical EuS/EuF2 films, the intermediate state in type-I-superconducting films of lead and tin could be resolved for the first time.
A Solid State Driver for Pulse and Fourier Transform NMR
Authors: Burnett L. J.
Published: February 2004

A four-channel solid state rf driver, which can provide the complex sequences of rf pulses necessary for recently developed pulse and Fourier transform nuclear magnetic resonance (NMR) experiments, is described. Suitable for use over a wide frequency range, the device features a high ratio of carrier suppression, accurate control of the rf phase in four separate channels, and a 100% duty cycle. The use of gated rf phase shifters allows considerable simplification in design and results in the need for but one rf gate.
Application of Channel Multiplier Plates as Image Information Preprocessors
Authors: Seko Atsuya , Kobayashi Hiroshi
Published: February 2004

The dead time of a channel plate has been regarded so far as an inevitable defect in many applications; however, it is pointed out in this paper that it can be considered as the memory time during which the input image is stored. Line drawing, moving object detection, and inversion of images were performed by an experimental preprocessor using the dead time characteristics. The device should be recognized as a two-dimensional operator with no scanning and without an electronic computer. The features of the device are very high-speed operation and high sensitivity for dark images.
Improved Uniform-Field Electrode Profiles for TEA Laser and High-Voltage Applications
Authors: Chang T. Y.
Published: February 2004

Simple analytic formulas that can be used to design a finite width uniform-field electrode for any desired aspect ratio and field uniformity are derived. The resulting profile is superior to those of Rogowski, Bruce, and Harrison in its smoothness, compactness, and field uniformity. A procedure for designing a three-dimensional profile is also given.
An Automatic Electric Field Measuring Equipment of Very High Resolution and Its Application for the Study of Acoustoelectric Phenomena
Authors: Zold T.
Published: February 2004

An electric field measuring equipment with a capacitive probe of 40 μ resolution was constructed using only ordinary materials and techniques. The operation of this equipment was completely automatic and the electric field profiles were recorded continuously by an x-y recorder. The duration of one measurement, consisting typically of the recording of about 50 profiles and of the sample current vs time diagram, in 4 mm long samples, was [inverted lazy s] 50 min. The usefulness of this equipment has been proven through its use for the observation of a large number of new electric field domain formations in photoconducting CdS samples. The detailed description of these observations will be reported elsewhere.
A Superconducting Suspension with Variable Restoring Force and Low Damping
Authors: Hebard Arthur F.
Published: February 2004

A technique for the magnetic suspension of small (< 1 mm diam) superconducting niobium spheres is described in which the restoring forces (shape of the applied field) can be conveniently adjusted and low losses in the translational modes of oscillation easily obtained. The suspension was developed for use in an experiment designed to detect the existence of fractional electric charge but is applicable to other experimental situtations as well. A typical sphere is suspended with a vertical period of oscillation of 1.5 sec and a Q of 3000. Adjustments can be made over the period range 0.6 to 9 sec and Q's as high as 8000 have been achieved.
Electron Difraction Unit with Supersonic Molecular Beam and Cluster Beam
Authors: Raoult B. , Farges J.
Published: February 2004

A supersonic molecular beam source was attached to an electron diffraction unit in order to study molecular structures and cluster structures. Because the density in a molecular beam is only a few times 1012 molecules per cm3, it was necessary to lower the pressure in the diffraction chamber to 5×10−8 Torr and to eliminate the back-scattered electrons at large s values. This was accomplished by means of a very deep (45 mm) beam-stop and a mask. Liquid helium cryopumping makes it possible to reduce the beam source bulkiness which, in turn, permits the placement of the scattering point as close as possible to the source (about 55 mm from the nozzle). Thus a target of the highest density is obtained, while a wide range of scattering is permitted. Reliable diffraction data have been obtained out to s = 45 Å−1. The main components of the diffraction unit are described, as is also the supersonic molecular beam source. A discussion is presented on the use of the apparatus.
Quasimodo—A Device for Suspending Small Solid Targets at the Focus of a High Power Laser
Authors: van Hulsteyn D. B. , Anderson L.
Published: February 2004

Using a magnetically retracted pedestal, small targets of a solid material can be accurately positioned at the focus of a laser pulse. The particular system to be described is relatively inexpensive, has proved capable of holding a vacuum of the order of 10−8 Torr, and has provided successful firings in more than 95% percent of the attempts. It has the added advantage of being easily adaptable to a variety of applications, such as toroidal confinement devices, mirror or minimum B machines, Z and Θ pinch systems and plasma focus devices.
Fast, Accurate Secondary-Electron Yield Measurements at Low Primary Energies
Authors: Henrich Victor E.
Published: February 2004

We describe a method of accurately measuring the secondary electron yield of solids over the entire incident energy range of 0–1000 eV in less than 30 msec using a commercial LEED/Auger system. Particular attention is paid to the region of low-energy incident electrons (Ep=0 to 100 eV), and the spatial and energy resolution there are considered. The method is fast enough to see temporal changes in yield on the scale of hundreds of milliseconds. Criteria for measuring the yield of semi-insulators are considered, as well as measurements of fine structure in the yield near Ep=0 eV.
A ``Differential Reflectometer'' for Measurements of Small Differences in Reflectivity
Authors: Holbrook J. Alfaro , Hummel R. E.
Published: February 2004

An instrument is described which measures small differences in optical reflectivity or transmissivity of two specimens. The apparatus has been used to investigate surface effects such as corrosion or deformation of thin surface layers as well as metallurgical transformations or compositional modulation. A complete ``differential spectrogram'', i.e., scan through the visible and near uv region, is performed in less than 1 min.
Digital Correlation Technique for Third Order Intensity Correlation Measurements of Light
Authors: Chopra S. , Mandel L.
Published: February 2004

An electronic correlator is described in which the arrival times of photoelectric pulses are registered directly in digital form. Pairs of interval times, corresponding to three photoelectric pulses, are then mapped onto a one-dimensional array of numbers, and are stored in the memory of a multichannel analyzer. The stored set of numbers provides a two-dimensional histogram, that is a measure of the third order intensity correlation function. This technique allows information to be accumulated at a higher rate than with time-to-amplitude converters.
An Absolute Method of Measuring Energy Outputs from CO2 Lasers
Authors: Jacob J. H. , Pugh E. R. , Daugherty J. D. , Northam D. B.
Published: February 2004

In the energy meter described here the CO2 laser radiation is almost completely absorbed by an Al2O3 surface on an aluminum plate. The high absorption of the surface (≥95%) eliminates the need for calibration and the laser energy is computed by measuring the temperature rise of a plate with known thermal capacity. Experimentally we find that the calorimeter noise level corresponds to an energy density of about 2 mJ/cm2. Calculations indicate that the instrument is capable of measuring the energy of a single pulse that is 1 nsec wide, provided the pulse contains an average energy density of 10 mJ/cm2. We have estimated the radiation and convection losses and found them to be negligible. The calorimeter is good for radiation between 8.5 and 11 μ; however, with modifications the bandwidth could easily be increased.
A cw Interferometer for Elastic Constant Measurements
Authors: Day J. Paul , Ho Paul S. , Ruoff Arthur L.
Published: February 2004

A continuous wave ultrasonic interferometer is described which makes possible measurement of both absolute values of and small changes in the elastic constants of solids using commercially available subsystems.
An Isothermal Titration Microcalorimeter
Authors: Christensen J. J. , Gardner J. W. , Eatough D. J. , Izatt R. M. , Watts P. J. , Hart R. M.
Published: February 2004

An isothermal titration microcalorimeter having a volume of 4 ml and capable of temperature control to ± 2 × 10−5 °C is described. Major components include a constant temperature water bath controlled to ± 3 × 10−4 °C, a platinum reaction vessel, and an isothermal control circuit consisting of constant Peltier thermoelectric cooling and variable Joule heating controlled by a thermistor in an ac Wheatstone bridge circuit. The calorimeter was tested by measuring the heat of ionization of water and was found to produce data accurate to ±0.1% for this system. The instrument is ideally suited for measuring heats where small samples are used such as in the investigation of many biological systems.
Modifications to High Temperature Thermal Analysis Equipment
Authors: Perrott C. M. , Read D. B.
Published: February 2004

Modifications of commercial equipment for high temperature thermal analysis are described. Physical changes allow the use of silica or alumina as encapsulating materials in addition to the normal metallic sample holders, while electronic modifications facilitate instrument use to study small thermal effects at temperatures in the range 1000–1500°C. A method for encapsulating samples in alumina tubes is also described.
A High Resolution Dynamic Technique of Thermoelectric Power Measurements
Authors: Zrudsky Donald R. , Showalter Alan B.
Published: February 2004

A new technique, principally applicable to metals and alloys, has been developed for high resolution absolute thermoelectric power (TEP) and differential thermoelectric power measurements. It utilizes two continuously monitoring dc nanovolt amplifiers, one for the sample couple thermoelectric voltage and the other for a thermocouple voltage proportional to temperature differences developed across the samples. The outputs of these amplifiers are attached to the channels of an X-Y recorder, thus yielding direct slope-proportional data. By using heat from a low-mass, electrostatically guarded heater to develop transient temperature gradients across samples, it is possible to dynamically determine the absolute TEP of a sample versus lead (Pb) or the differential TEP of two nearly similar samples, one of whose composition or history of treatment has been slightly altered. Reducing thermal time constants with an independent heat leak permits the completion of a TEP measurement in a few seconds, thus yielding high resolution determinations under adverse experimental conditions. The use of a special sample necking and ``heat sinking'' techniques, as well as a low melting point, low TEP, ternary eutectic indium alloy solder, make it possible to obtain results with a range of high resolutions. The experimental resolution attainable with these two dynamic techniques can be summarized as ±[10−3)(ΔT)−1(μV/K)+1.0%] for absolute TEP and ±[ΔT)−2+Sabsolute2]1/2 10−3(μV/K) for differential TEP, where ΔT is the range 0.01–1.0 K increment of differential temperature and Sabsolute is the approximate value of the thermopower of one of the samples. Data utilizing this newly developed technique are presented on Chromel-P, Wood's metal solder, and the ternary eutectic InSnCd solder alloy, as well as differential TEP measurements of two opposing Chromel-P samples over the temperature range of T = 1.5–300 K.
Laser Mirror with Variable Focal Length
Authors: Mikoshiba S. , Ahlborn B.
Published: February 2004

A simple and inexpensive method of making a concave/convex mirror (2–-13 cm or more in diameter) with variable focal length, f (1m <f<∞) is presented. By using such a mirror in a CO2 TEA laser cavity it was found that the energy output and alignment tolerances vary as functions of f as predicted by theory and that the variable focal length mirror serves as a useful tool for obtaining the optimum laser cavity configuration.
Variable Temperature Probe
Authors: Lewis R. T.
Published: February 2004

A simple method for varying the temperature of a sample from 4.2 K to over 800 K is described.
An Informative Method for Recording Partial Discharges in Insulating Materials
Authors: Johnson R. G. , Tibbetts S. J.
Published: February 2004

A method of recording large numbers of partial discharge pulses graphically as a function of specimen voltage on a linear time base is described. The conventional method, using a Lissajous figure synchronized with the specimen voltage, does not show a graphic relation between the pulse occurrence and specimen voltage, and is limited by the repetitive nature of the Lissajous figure. Examples of the discharge pulse patterns obtained with the new method are given to illustrate the versatility of the technique. The method provides useful information in the study of partial discharge characteristics and causes.
A Precision Hydromechanical Displacement Micropositioner
Authors: Sapp Alvin E. , Cook Clarence C.
Published: February 2004

A compact self-contained linear displacement micropositioner is described which is ideal for very precise positioning along a single axis. The micropositioner has a useful range of about 1.8mm and a resetability of about 0.025μ. Backlash in the device is nil.
A Thermistor Bimetal Thermocouple Hemisphere Electrode for Simultaneous Electrochemical/DTA Measurements
Authors: Graves Bruce B.
Published: February 2004

Construction techniques are described for a thermistor bimetal thermocouple electrode sensitive to thermal changes at the single electrode during scanning electrochemical experiments in liquid solutions. Incorporation of a thermocouple in this device permits caloric standardization of (DTA) thermogram peak areas from the known bimetal Peltier effect enthalpy change for passage of a known charge across the couple.
A Scanning Electron Microscope Stage for the Observation of Chip Formation
Authors: Ramalingam S. , Bell Adam C.
Published: February 2004

By a direct examination of chip formation while machining, a considerable amount of data pertinent to the development of the theory of metal cutting can be obtained. However, the microscopically heterogeneous plastic flow involved in the process calls for high magnification observations. To facilitate this, a new cutting stage has been designed and built to carry out metal cutting studies within a scanning electron microscope. Permanent records of the dynamic cutting operations are then obtained by videotaping the experimental results. This paper describes the stage designed and briefly summarizes the results obtained.
A 10 nsec Resolution Counter for Multiparticle Atom Probe Time-of-Flight Measurements
Authors: Berger A. S.
Published: February 2004

The atom probe field ion microscope allows single atom identification by combining a field ion microscope with a time-of-flight mass spectrometer. A circuit is described which provides time resolution of ±10 nsec in an interval of 100 μsec for up to eight particles arriving at the detector in any one field evaporation pulse cycle. The duty cycle of the instrument is limited only by the data recording system. The ±10 nsec resolution allows identification of species separated by one mass unit under the worst case conditions of high atomic weight and high accelerating voltage.
Design and Performance Characteristics of A Small Subsonic Flow HF Chemical Laser
Authors: Glaze James A. , Linford Gary J.
Published: February 2004

A small, transverse flow, moderate power cw hydrogen fluoride chemical laser is described. This laser provides up to 10 W of cw output power on a number of Pv(J) lines associated with 3→2, 2→1, and 1→0 vibrational transitions of hydrogen fluoride (HF). Single line power levels of up to 1.5 W were obtained on the strongest HF transitions. The measured electrical efficiency was [inverted lazy s] 1% for a total mass flow of 100 mg/sec. The gain and spectral power distributions were found to be characteristic of a complete inversion rather than a partial zero field inversion on the 2→1 transitions.
An Apparatus for Study of Secondary Ions from Ion Bombardment of a Metal Surface
Authors: McCaughan Daniel V. , Sloane R. H. , Geddes J.
Published: February 2004

An apparatus for the study of secondary positive and negative ions from metal surfaces under positive ion bombardment has been constructed in stainless steel using ultra-high vacuum technology. It provides for triple mass analysis (i.e., of primary and both secondary beams), and energy analysis of the secondary ions. A retarding technique suitable for wide energy distributions has been developed. Some preliminary results obtained are given.
A Linear Gate for Photomultiplier Signals
Authors: Albach G. G. , Meyer J.
Published: February 2004

A linear gate is presented for gating output pulses from a photomultiplier. Measurements with an EMI 9558A tube show the circuit to have a very high cutoff efficiency, turn-on/off times of about 5 nsec, and very small noise transients.
Beam Position Measurement During Fast Ejection
Authors: Cupérus Jan H.
Published: February 2004

A series of electrostatic pick-up electrodes is used to measure the horizontal position of a single bunch during fast ejection in the Serpukhov proton synchrotron. Any one of the 30 circulating bunches can be followed, whether it is being ejected or stays in the accelerator. The electrode signals go directly into long coaxial cables and no active components are present in the radioactive zone. The signals are digitized and go to a minicomputer. The response of the system is linear over the whole width of the electrodes (200 mm).
A Simplified Double Plasma Device for Plasma Wave Studies
Authors: Cohn D. B. , Taylor R. J. , Ault E. R.
Published: February 2004

A variation of the DP (double plasma) device is described which allows the generation of plasma waves in the DP manner without the necessity for producing two separate plasmas.
Some Modulus Arithmetic Algorithms for Binary Logic
Authors: Clark B. G.
Published: February 2004

Simple logical designs are exhibited which test a binary number for divisibility by numbers of the form 2l(2m − 1)(2n + 1).
An Optical Curve Tracer for Pulsed Laser Diodes
Authors: Thomson I.
Published: February 2004

A simple apparatus is described which displays the light intensity from semiconductor laser diodes as a function of current. The method uses low duty cycle current pulses and is useful for light emitting device evaluation in the same way as V-I curve tracers are for other semiconductor devices.
Attaching Ohmic Leads to Lead-Filled Vycor Glass
Authors: Moore S. E. , Meincke P. P. M.
Published: February 2004

Electrical connections can be made to porous Vycor glass filled with lead by inserting the glass sample into molten Wood's metal containing the leads. When the Wood's metal freezes, contacts of very low resistance which are strong enough to permit repeated cycling from room temperature to liquid helium temperature are formed.
Technique for Containing Low-Boiling Liquids in a Sealed Pt Capsule
Authors: Anderson B. C. , Hoover C. L.
Published: February 2004

Techniques are described for fabricating, filling, and sealing a Pt capsule for liquids boiling as low as − 10°C. Such a container, with volume of 0.25 ml, has been used in experiments in a tetrahedral-anvil apparatus for conditions up to 60 kilobar and 300°C.
A Transient Recorder to Magnetic Tape Interface
Authors: Ratcliffe C. A. , Felix W. D.
Published: February 2004

An electronic interface coupler has been designed which extracts data from a digital transient recorder and prepares the signal for recording by a magnetic tape unit which is compatible with a laboratory computer. System operation, circuitry, and software are discussed.
Note on Signal-to-Noise Ratios for Ion and Metastable Detection of Neutral Molecular Beams
Authors: Collins Frank G.
Published: February 2004

S/N ratios for ion and metastable detection of neutral molecular beams which utilize time integrated measurements of an electron multiplier output are discussed. It is shown that the excitation probability is considerably less than the ionization probability for most molecules causing S/N improvements with metastable detection to be less than previously expected. An additional decrease results from the low electron yield of the metastable molecule compared to the ion at the electron multiplier surface.
Thermal Resistance of Contacts
Authors: O'Callaghan P. W. , Probert S. D.
Published: February 2004

In order to obtain accurate thermal resistance data for contacts under high loads (i.e., P/M > 2×10−3) it is not always necessary to employ a high vacuum for transverse thermal insulation, or a guard-heater arrangement.
Thermocouple Structure for Measurements of Surface Temperature
Authors: Rogoff Gerald L.
Published: February 2004

This Note describes a thermocouple network for measuring an average temperature of a convex surface. A version for a cylindrical surface is illustrated. The device combines advantages of a resistance thermometer and of a simple thermocouple. It is relatively easy to mount; it provides a distributed temperature measurement; and it is operated as an ordinary thermocouple.
Preparation of Electron Microscope Disk Specimens by Ultrasonic Impact Grinding
Authors: Rennhack E. H.
Published: February 2004

A relatively simple and rapid method for preparing high-quality electron microscope disk specimens from electrically conductive and nonconductive brittle bulk materials is described. The technique utilizes a model 2–334 Raytheon ultrasonic impact grinder to generate and transmit high frequency vibrational energy through a tube-shaped tool tip to an abrasive-water slurry circulated over the bulk material. Machining is accomplished by the abrasive particles resonating and impacting the bulk material in a vertical plane below the tool tip. The net effect produces a microscopic grinding action on the workpiece that parallels the contour of the end of the tool tip.
Method of Measuring the Fluorescence Lifetime by Using the Distortion of an Electric Pulse
Authors: Osada K.
Published: February 2004

A method is proposed for resolving the convolution integral of fluorescence pulse by means of an electric circuit to deduce the lifetime since it is concluded from the theoretical results that the behavior of fluorescence is analogous to the distortion of an electric pulse after passing through a circuit.
Fringing Emitter Field and Energy Resolution in uv Photoelectron Spectroscopy
Authors: Abbati I. , Braicovich L. , De Michelis B.
Published: February 2004

The effect of the fringing emitter field on the energy distribution curves measured with screened retarding field spectrometers is discussed; a simple technique is presented which can remove the effect in a large number of cases.
A Simple Computer Interface for a Pulsed NMR Spectrometer
Authors: Rhodes N. L. , Cross B. P. , Tignor S. L. , Roeder S. B. W.
Published: February 2004

Described here is a simple and relatively inexpensive (less than $500) computer interface between a pulsed NMR spectrometer and the Varian 620/i computer. The basic design should be suitable for interfacing most minicomputers and pulsed spectrometers (NMR and others). It features an oscilloscope display, a fast ADC, and circuitry for proper pulse and signal conditioning.
An ac Bridge Circuit for Low Temperature Thermometry
Authors: Zair E. , Greenfield A. J.
Published: February 2004

The introduction of a precision, inductive, decade ratio transformer to serve as a voltage divider together with voltage followers permits one to construct a 4-terminal ac bridge with an accuracy of better than 0.001%. Such a bridge is particularly suitable for accurate (0.003%) low-temperature Ge resistance thermometry. This bridge also makes possible the direct intercomparison of different Ge resistance thermometers, thus allowing a direct and therefore more accurate determination of temperature gradients.
A Gas Discharge Electron Gun for the Generation of Submicrosecond Pulses of High Energy Electrons
Authors: Carmichael C. H. H. , Garnsworthy R. K. , Mathias L. E. S.
Published: February 2004

The pulsed electron gun described in this paper is of simple construction and is intended for use in studies of ionization and excitation in high pressure gases. It employs a high-voltage discharge in helium gas and emits a 50 mm diam beam of 100 keV electrons through a titanium foil window, the transmitted pulse having an energy of approximately 1 J. The use of a coaxial discharge circuit results in a pulse duration of the order of 100 nsec. Graphs are presented showing the performance as a function of the voltage applied to the gun and of the gas pressure in the discharge region. It was found that adjustment of this pressure over the range 1–40 Pa varied the pulse duration from 300–30 nsec.
Distortions of Time-of-Flight Signals
Authors: Young Wen S.
Published: February 2004

Use of the time-of-flight (TOF) technique in molecular beam applications is reviewed. If the peak signal height and the hydrodynamic flow time are used as the normalization quantities, then a convenient dimensionless TOF signal is obtained in a double-convolutional integral form which involves three dimensionless functions: the molecular beam speed distribution function, the chopper gate function, and the dynamic function of the detector and its electronics. The latter two functions are characterized, respectively, by the dimensionless characteristic times T̃ and τ̃e. Numerical examples demonstrate distortions of TOF signals caused by these characteristic times and errors made in analyzing TOF signals when not taking into account the effects of T̃ and τ̃e. The orders of magnitudes of T̃ and τ̃e are not negligible; therefore, their effects should be treated in TOF signal data reductions.
Magnetic Multipole Containment of Large Uniform Collisionless Quiescent Plasmas
Authors: Limpaecher Rudolf , MacKenzie K. R.
Published: February 2004

Over 1200 Alnico magnets (1.3 × 1.3 × 4 cm) are used to contain a conventional discharge plasma produced by 1–20 A of emission from 6–48 small filaments at − 60 V. Densities up to 1012 ions/cm3 are produced in argon at 2 × 10−3 Torr. At 5 × 10−6 Torr typical parameters are: 8 × 1010 ions/cm3; ni / n0 ≈ 0.7; Te ≈ 5 eV; Ti ≈ 0.5 eV; noise 〈 δn/n 〉 ≈ 2 × 10−4; and < 1% nonuniformity over a volume 31 cm diam by 69 cm. Uniform dense plasmas of He, D, and H are also produced. The ion containment appears to be both magnetic and electrostatic.
Automatic Recording of Faraday Rotation and Circular Dichroism
Authors: Harms H. , Feldtkeller E.
Published: February 2004

An instrument is described which allows automatic recording of the temperature or magnetic-field dependence of both the magneto-optic Faraday rotation and the ellipticity angle of circular dichroism of magnetic samples. The instrument includes a Wollaston analyzer prism, two light detectors, and an operational amplifier circuit containing an electronic divider for eliminating the influence of light intensity variations. Changes of 10″ in the Faraday rotation angle and of 1′ in the angle of circular dichroism are detectable with our equipment.
UHV Systems for Surface Studies by Ion Scattering
Authors: Wheatley G. H. , Caldwell C. W.
Published: February 2004

Two UHV systems have been built for studies of solid surfaces by ion backscattering in the energy ranges (a) 0.5–50 keV and (b) 100–300 keV on separate ion accelerators. The UHV systems are similar in most respects except that (b) has LEED optics. The stainless steel chamber with integral pumping system encloses a goniometer in which the sample can be rotated and tilted for alignment of a crystal axis with the beam. The sample can also be translated across the beam. The energies of backscattered ions are measured in an electrostatic analyzer which has three independent motions to allow the analyzer to be precisely aimed at the beam spot on the sample. The chamber sits on a table which can be adjusted vertically and horizontally. Samples can be inserted conveniently through a 3.8 cm side port and attached to the goniometer with a special tool. Special problems encountered in mating a UHV system to an ion accelerator will be discussed. Results of measurements in system (a) have been reported [D. J. Ball, T. M. Buck, D. MacNair, and G. H. Wheatley, Surface Sci. 30, 69 (1972)].
A Portable Millisecond-Integration-Time Photoelectric Photometer
Authors: McGraw John T. , Wells Donald C. , Wiant Jerry R.
Published: February 2004

Portable equipment for recording millisecond-integration-time photoelectric photometric data is described. Digital data are reliably recorded on standard 6.35 mm audio grade magnetic tape via a quadradial audio grade tape deck. The system is designed specifically for recording lunar occulations of stars, but the data recording technique is independent of the data source. Recovery of the data is made via minicomputer.
An Infrared Cell for Catalyst Studies
Authors: Ryason P. R.
Published: February 2004

A stainless steel quartz cell for infrared transmission spectrophotometry of catalyst wafers is described. Wafer temperatures can be varied over a range from 900 to −196°C. The spectral range covered depends on the window material; a variety of windows can be used. With a 5–10 mg catalyst wafer in place in the cell, pressures in the low 10−9 Torr region have been attained.
A Rotatable Target Holder for a LEED Diffractometer
Authors: Burkstrand James M.
Published: February 2004

A target holder suitable for ultrahigh vacuum experimentation is described that allows rotation of the target about an axis perpendicular to its surface, in addition to the motions supplied by a commercial sample manipulator.
A Low Energy Electron Source for Mobility Experiments
Authors: Jahnke James A. , Silver M.
Published: February 2004

Thin film Al–Al2 O3–Au diodes were used as sources of low energy electrons (∼1 eV) in a drift velocity spectrometer. These diodes were found to offer several advantages over other sources used for electron mobility studies in dense gases and liquids.
Use of a Stable Polarization Modulator in a Scanning Spectrophotometer and Ellipsometer
Authors: Treu J. I. , Callender A. B. , Schnatterly S. E.
Published: February 2004

An improved oscillator system is described for use in high-frequency polarization modulation experiments. The improvement provides constant polarization modulation even when the resonant Q of the modulator crystal varies. A scanning split-beam spectrophotometer providing digital output of optical density has been developed which is readily interchangeable with other applications of the system.
An Apparatus for the Exposure of Plants to Selected Particulate Aerosols
Authors: Arvik Jon H. , Zimdahl R. L. , Olson K. W. , Dick D. , Skogerboe R. K.
Published: February 2004

A simple, inexpensive apparatus is described for the generation of particulate aerosols of known identity with aerodynamic size distributions characteristic of urban atmospheres. Means for using this system for the exposure of plants to selected lead aerosols are described. The design offers improvements over other systems used for similar purposes.
A High Temperature Vitreous Carbon Thermal Cavity System
Authors: Peng T. C.
Published: February 2004

A high temperature thermal cavity system, designed for material and material-environment studies, is described. A cylindrical cavity (17.4 mm diam and 25.4 mm long) is formed by a 2 mm thick vitreous carbon tube and two vitreous carbon end plugs. Provisions were made on the vitreous carbon tube and end plugs for temperature and mass spectrometric measurements and for admittance of environmental gases. The thermal cavity is resistively heated to 2000 K at an input power level of 2.5 kW with a partially open, four-layer molybdenum heat shield. Higher temperatures are obtained with a smaller cavity. The design of the thermal cavity, the temperature performance of the cavity, the change in electrical resistance of the vitreous carbon at high temperatures, and the mass spectrometric analysis of vitreous carbon-oxygen reaction are discussed.
A Biaxial Split Hopkinson Bar for Simultaneous Torsion and Compression
Authors: Lewis Jack L. , Goldsmith Werner
Published: February 2004

A biaxial split Hopkinson bar which operates in simultaneous compression and torsion is described. The device utilizes torsional stress waves generated by release of a stored torque and compressive waves generated by mechanical impact of a long rod onto a loading bar. The torque is released by capacitive discharge explosion of a thin foil in a holding adhesive joint. The two stress waves travel in opposite directions toward a specimen sandwiched between two rods, arriving at the specimen within 10 μsec of each other. The machine is used on specimens of compact bone, and it is found that plastic deformation without fracture can be achieved under the combined dynamic torsion and compression, whereas it seldom occurs under either of these loading modes alone.
An Array Simulation Facility
Authors: Aitken G. J. M. , Lewis J. R.
Published: February 2004

A system employing a small digital computer and a multichannel tape recorder produces a set of signals simulating those obtained from the elements of an array when a source moves through its field of view. Source and array may be two-dimensional, the source may move in real time and a change in the array or source characteristics is simply a program change. The principles of operation and two test simulations are described.
A New Technique for Auger Analysis of Surface Species Subject to Electron-Induced Desorption
Authors: Pepper Stephen V.
Published: February 2004

A method is presented to observe surface species subject to electron-induced desorption by Auger electron spectroscopy. The surface to be examined is moved under the electron beam at constant velocity, establishing a time-independent condition and eliminating the time response of the electron spectrometer as a limiting factor. The dependence of the Auger signal on the sample velocity, incident electron current, beam diameter, and desorption cross section is analyzed. It is shown that it is advantageous to analyze the moving sample with a high beam current, in contrast to the usual practice of using a low beam current to minimize desorption from a stationary sample. The method is illustrated by the analysis of a friction transfer film of PTFE, in which the fluorine is removed by electron-induced desorption. The method is relevant to surface studies in the field of lubrication and catalysis.
Properties of Microwave Cavities Containing Magnetic Resonant Samples
Authors: Rages Kathy A. , Sawyer Robert E. , Hale Edward B.
Published: February 2004

Properties of TE011 cylindrical, microwave cavities containing cylindrical samples of various radii and dielectric constants are calculated. The properties considered are the resonant frequency, quality factor (Q), relevant magnetic filling factor for spin transitions (η), and a signal sensitivity factor (Qη) for a lossless sample. Sample sizes range from zero radius to full cavity radius with some experimental data on less than full length samples. The choice of dielectric constants ranges from one to sixteen. The data are presented in dimensionless form since they will be of use to other ESR experimentalists. It is shown that use of large samples is undesirable even if they are lossless. Furthermore, elongated cavities (D/L ratios less than one) are to be preferred over shortened cavities.