bluuebunny/crossref_metadata_2025 huggingface dataset:
Two Spectrographs for Use with Image Intensifier Tubes
Authors: Sharpless R. L. , Young R. A.
Published: February 2004

This article describes two spectrographs using image intensifier tubes for increased sensitivity. One spectrograph uses an echelle grating to give a resolution of about 0.10 nm and has all-reflecting optics for use in the ultraviolet. It is usable over the range from 250 to >600 nm and covers about 150 nm on a 24×36 mm frame. The second spectrograph uses transmission optics of high optical speed and covers roughly the range from 400 to 760 nm on a 24 mm long frame with a resolution of about 2 nm.
Nanosecond Fluorescence Apparatus with a Spontaneously Fissioning Excitation Source
Authors: Calo Joseph M. , Axtmann Robert C. , Persing Robert G.
Published: February 2004

We report the development of a versatile apparatus for the precise measurement of fluorescent lifetimes. Based on the pulse sampling method, the device utilizes a unique excitation source—a few microcuries of the spontaneously fissioning nuclide 252Cf. A stochastic analysis of distortion effects demonstrates that the random risetimes and amplitudes of the excitation pulses cause negligible distortion in comparison to that produced by convolution with the photomultiplier tube's impulse response function. Experimental results for the nitrogen second positive group (SPG) and the first negative group (FNG) were in excellent agreement with values reported by others. Simultaneous observation of the processes N2(C3Πu)→ lim k1N2(B3Πg)+hν,  and  N2(C3Πu)+N2(X1Σg+)→ lim k2products,gave τ=1/k1=40.5±1.3 nsec and k2/k1=1.75±0.06×10−2 Torr−1.
A Novel Microwave Noise Temperature Generator Having an Output Temperature of from below 40 to above 370 K
Authors: Jordan Paul R.
Published: February 2004

A variable microwave noise temperature standard having an output from below 40 to above 370 K is described. This temperature standard is unique in that a closed cycle low temperature cooler used in conjunction with a proportional control heater network provides continuously variable low temperatures which are independent of the boiling temperatures of cryogenic liquids and may be readily changed and known with an accuracy of better than 1.0 K. A variable temperature output is obtained without the use of a microwave attenuator thus eliminating the inherent errors associated with the attenuator. The output noise temperature is completely calculable using measured parameters (i.e., thermal temperatures, waveguide insertion loss, and impedance mismatch factors) and as a result may qualify as a primary noise standard.
Absolute Efficiency Measurements for Channel Electron Multipliers Utilizing a Unique Electron Source
Authors: Paschmann G. , Shelley E. G. , Chappell C. R. , Sharp R. D. , Smith L. F.
Published: February 2004

A unique low energy (0–50 keV) electron accelerator has been developed which provides a broad, parallel, low intensity electron beam with excellent long term stability. The beam intensity is approximately 106 electrons·cm−2 ·sec−1 and the long term stability is better than 2%/day. A prototype of this accelerator is described and the results of its application to instrument calibration and channel electron multiplier (CEM) efficiency measurements are presented. The absolute electron detection efficiency for CEM's was found to vary from approximately 90% at 1 keV to 73% at 14 keV with a probable error of ±10%. The large disagreement among the various published measurements of CEM detection efficiency is discussed.
A Method for Determining the Dynamic Response of an Elastic Load Cell Element
Authors: Potzick James
Published: February 2004

A method has been developed for determining the dynamic characteristics of a load cell element by subjecting it to sinusoidally time dependent forces, and an experiment using a piezoelectric shaker is described which illustrates the feasibility of the method. At present a simple viscoelastic model is assumed for the load cell element, and relaxation times on the order of 10−7 sec have been measured. The application of this information to load cells subjected to other types of dynamic forces is also discussed.
A Screened Emitter Photoelectron Analyzer
Authors: Pierce D. T. , DiStefano T. H.
Published: February 2004

A retarding field energy analyzer for photoelectron spectroscopy is improved by adding a screened field-free region around the emitter. For preliminary measurements on nickel, the analyzer error was estimated to be <2.8% of the kinetic energy. The electronic circuit configuration which performed best is presented along with a description of spurious effects introduced by circuit variations.
Apparatus for the Measurement of High Temperature Plasma Reactions
Authors: Mullen J. H. , Madson J. M. , Medgyesi-Mitschang L. N. , Peng T. C. , Doane P. M.
Published: February 2004

An experimental apparatus designed for studying reaction processes in high temperature plasmas is described. An rf induction plasma produced at gas temperatures from 1000 to 4000 K is passed through a reaction channel at sonic velocity where it reacts with supersonically injected target gas molecules. Pressures in the reaction channel can be varied from 25 to 125 Torr. The plasma, together with the reaction products, undergoes a free jet expansion into a vacuum chamber at 0.2 Torr where the expansion core flow is sampled by a molecular beam mass sampling system using a quadrupole mass spectrometer for analysis. The electron density in the free jet is measured with a Ka-band interferometer. The electron temperature in the plasma source and reaction channel is measured spectroscopically; in addition, the electron temperature in the source is monitored with an X-band radiometer. The change in the electron density, together with the change in the intensity of the positive and negative ion signals as a function of the number of target gas molecules injected, is used to evaluate the reaction rates. Examples of electron attachment rate measurements in N2O–Ar and SF6–Ar mixtures at 3000 K are given.
Magnetically Insulated Transformer for Attaining Ultrahigh Voltages
Authors: Winterberg F.
Published: February 2004

A high voltage transformer in which a high magnetic field inside a hard vacuum insulates against breakdown is proposed. The magnetic field is generated by electric currents in high field superconductors. Voltages up to 109 V may be attainable with such a system. A rectifier using high magnetic fields can transform the end voltage from ac to dc. The energy output at the terminal of the secondary coil can be extracted in the form of either an electron or an ion beam through the use of the field emission process. Potential applications include (1) high energy particle accelerators with beam intensities many orders of magnitude larger than in conventional accelerators or meson factories, (2) use in controlled thermonuclear fusion devices, and (3) continuous pumping of powerful lasers. The feasibility of the system will depend upon depressing the breakdown perpendicular to the direction of the high magnetic field.
Quantitative Space and Time Resolved Laser Schlieren System for the Study of Hypersonic Flow
Authors: Koziak W. W.
Published: February 2004

A space and time resolved quantitative schlieren system has been developed for the measurement of density gradient distributions in a two-dimensional hypersonic flow field. The device uses a narrow beam helium-neon continuous laser which is scanned across the flow field by a fast revolving multifaced mirror. A knife edge-photomultiplier assembly monitors the deflection of the laser beam caused by the presence of density gradients in the test gas. Spatial resolution which is determined by the diameter of the laser beam in the flow field is less than 0.6 mm. Time resolution is determined by the speed of rotation of the mirror and the number of mirror faces but in the present setup it is limited to approximately 2×10−3 sec by the frequency response of the data recording system. Quantitative performance has been checked for a known density gradient which was simulated by the use of an accurately specified glass wedge.
A Pulsed Electron Paramagnetic Resonance Spectrometer
Authors: Brown I. M. , Sloop D. J.
Published: February 2004

A pulsed X-band superheterodyne electron paramagnetic resonance spectrometer with coherent pulse generation, phase sensitive detection, and a response time of 40 nsec is described. The experimental details of the circuitry used in the measurement of electron spin-lattice relaxation times are given. A transient technique of performing electron-nuclear double resonance (ENDOR) which entails monitoring the two-pulse or three-pulse electron spin echo is discussed.
Minimum Image Size in a Parallel Plate Electrostatic Spectrograph
Authors: Proca G. A. , Green T. S.
Published: February 2004

Previous analysis of the focusing properties of a parallel plate electrostatic spectrograph has shown that second order focusing can be achieved. In the present paper it is demonstrated that as a corollary, there exists an optimum focal line in which the angular aberrations are reduced to one quarter of their values on the normal focal line, as is the case in optical systems. Results of computations of the line shapes are also presented.
High Resolution Cinematography at High Temperature in the Electron Microscope
Authors: Lugton Frank D. , Warble Charles E.
Published: February 2004

Required microscope conditions and the technique of photography and development procedures are described, and means of improvement suggested for high resolution, high magnification 16 mm cinematography of chemical reactions at high temperature in the electron microscope. It is shown experimentally that, even with an externally mounted camera, resolutions of 12–15 Å can be achieved in practice at reaction temperatures of 1000–1100°C and magnifications of 110 000 × on the microscope fluorescent screen. Standard 16 mm reversal film exposed at 2 frames/ sec for 0.2 sec/frame and f/1.8 lens aperture are adequate but require accurately controlled development conditions. It is therefore shown quantitatively that it is possible to obtain higher resolution at shorter exposure times by photographic means than by more complicated and more costly electronic equipment. Standard electron microscope movie attachments were considered but vibration alone prohibits their use for high resolution recording. Photographic grain structure remains the major factor limiting high resolution cinematographic recording in the electron microscope. Reaction is observed between MgO and the Pd specimen support grid. A phase behaving like a liquid forms and extends over the surface, stripping the crystal via a surface mechanism, changing shape and contracting back into the main body of the phase.
A Small Bragg Diffraction X-Ray Spectrometer
Authors: Der R. C. , Boster T. A. , Cunningham M. E. , Fortner R. J. , Kavanagh T. M. , Khan J. M.
Published: February 2004

A small, easily constructed, and high efficiency Bragg angle x-ray spectrometer has been developed. Employing either a lead stearate or a KAP crystal, it has been used to measure x rays in the 150–1000 eV region from ion-atom collisions. At the carbon-K energy (277 eV), it has an FWHM of 14 eV and an efficiency of 10−2 counts per incident x ray. Electronics and controls for fully automatic scans are described.
A New Method for Low Energy (0–10 eV) Ion-Gas Total Cross Sections Using an Electrostatic Repulsion Technique
Authors: Martin D. H. , Davis D. A. , Christian W.
Published: February 2004

A method is described for measurement of low energy total cross sections using an analysis of the uncollided portion of the beam by electrostatic repulsion. Instead of energy separation of the initial beam, a (retarded) spectrum of energies (0–10 eV) is accepted and analyzed with and without interactions. The method applies, in principle, to energies arbitrarily close to zero, limitations occurring in beam intensity and in the smallness of energy group treated in the associated computer analysis. A further limitation is that only large angle scattering is measured. Test measurements for argon ions in argon gas show total cross sections above 1 eV to be indistinguishable from quoted values of charge transfer. In the vicinity of 1 eV a steep rise in cross section is observed.
Small Computer Data System for a Portable Quadrupole Mass Filter: A Reexamination of the Hydrogen-Deuterium Self-Exchange Reaction H2O+D2O = 2HDO
Authors: Jones N. A. , Friesen R. D. , Pyper J. W.
Published: February 2004

A small computer data system was constructed and evaluated for use with a portable quadrupole mass filter. The system is composed of two conventional audio tape decks, one interfaced to the portable mass filter and the other to a small shared computer. In operation, a series of mass spectra is recorded on magnetic tape. Next, the tape is transferred to the audio tape deck interfaced to the computer. The computer adds the spectra together and performs appropriate spectrum stripping and arithmetic routines. By reexamining hydrogen-deuterium self-exchange in water, we show that the mass filter-recorder-computer system gives results that are as accurate and precise as results obtained from other mass spectrometric methods.
A Method for the Calibration of Synchrotron Beam Pickup Electrodes
Authors: Baron A. I. , Vogel U.
Published: February 2004

A method is described for the measurement of characteristics of pickup electrodes (PUE) for monitoring coordinates of an accelerator beam. A new representation is discussed for determining the coordinates of the center of charge for the entire PUE aperture. A few prototypes of PUE's to be installed in the AGS were tested and the results show that nonlinear deviations are at least 1 mm/25 mm. The method of measurement has a resolution of at least 0.1 mm/25 mm; it can therefore be used for (a) the design of high quality PUE's and (b) calibration of PUE's as installed in the accelerator in order to increase the usable aperture and the accuracy of beam coordinate monitoring.
Photodetector Triggered Pulse Selection from a Mode Locked Ruby Laser
Authors: Billman Kenneth W. , Burnham David C.
Published: February 2004

A technique for external selection of a single pulse from the output train of a mode locked ruby laser is presented. Ease of optical alignment and the ability to be triggered by a small individual pulse early in the train are the chief advantages of this photodetector technique over that of spark gap triggering.
A Method of Detecting Viscous Effects in a Pulsed Supersonic Nozzle Beam
Authors: Skinner G. T.
Published: February 2004

A room temperature supersonic nozzle source beam was constructed as the target for a shock tube driven molecular beam. It is actuated electropneumatically and provides a few hundred microseconds of nearly constant intensity. The beam is formed from a supersonic flow by a two-stage skimming process. In optimizing the configuration of skimmers and nozzle it was found that viscous regions in the system could be detected by observing the transient flux in the peripheral region around the beam.
An Electrical Sensor of Plane Coordinates
Authors: Hurst G. S. , Parks J. E.
Published: February 2004

The general need for an inexpensive sensor of plane coordinates has been satisfied by devising a simple electrical method. Two orthogonal sheets of conducting paper are connected in such a way that x and y coordinates appear as independent dc potentials. For example, one may wish to process graphical information, y(x), by reading digitized x and y coordinates, by replotting a function y(x), or by feeding y(x) into a computer. These operations and others are performed by using the plane coordinate sensor with existing electronic systems.
Optical Method for Measuring Amplitudes of Damped Spreading Ripples
Authors: Walbridge N. L.
Published: February 2004

An accurate method for measuring the amplitudes of sinusoidal ripples using the intersection of caustic surfaces has already been developed. By comparison with the sinusoidal case, we find that the same equations for the amplitudes apply to damped spreading ripples, for example, those produced by a small spherical source in a real liquid. The limitations on the ratio of the spatial absorption coefficient to the wave number and on the distance from the point source are discussed.
The Production of Plane Surfaces on Single Crystals of Copper and Copper Alloys
Authors: Ahearn J. S. , Monaghan J. P. , Mitchell J. W.
Published: February 2004

Chemical and electrochemical polishing methods which allow submicroscopically smooth optically flat surfaces to be produced on crystals of copper and copper alloys are described. This is made possible by the use of solutions for cloth chemical polishing which have as additives nitrogen-containing mercapto-sulfur compounds and surface active agents, which facilitate rapid flattening of the surfaces. Conditions for producing surfaces with the best compromise between flatness and submicroscopic smoothness have been worked out. A new system in which an endless cotton belt, saturated with a phosphoric acid electrolyte containing chromic acid, moves between a stationary cathode and the stationary anodic specimen has been introduced for electrochemical finishing. This almost eliminates the fine grained structure often seen on electropolished surfaces of alloy crystals.
Determining the Thermal Expansion Coefficient of Liquids by Observing the Onset of Convection
Authors: Caldwell Douglas R.
Published: February 2004

The coefficient of thermal expansion of a fluid can be measured by determining the critical temperature difference for the onset of thermal convection in a fluid layer heated from below. This method is particularly useful for fluids of very low thermal expansion because its accuracy is independent of the magnitude of the thermal expansion. It is easily adapted to measurement at elevated pressures. Accuracy of 0.5% is obtainable with care.
The Dynamical Behavior of a Chopper-Rotating Crystal System in a Neutron Time-of-Flight Experiment
Authors: Eder O. J.
Published: February 2004

The installation of a phased chopper in front of a rotating crystal time-of-flight experiment is described. The results on the dynamics of the system, the background improvement, and the luminosity of the chopper rotating crystal spectrometer are presented. It is found that the significant background is reduced by a factor of 10, while the luminosity is decreased by about 10% only.
A Semiautomatic Spreading Resistance Probe
Authors: Gupta D. C. , Chan J. Y.
Published: February 2004

The spreading resistance probe technique of measuring resistivity in epitaxial layers requires precise control of the parameters that affect the area of contact and damage under the probe. The effects of these parameters on the measurements are described and the design of a semiautomatic probe is presented. The probe can be lowered with the same velocity during each measurement and the IR drop across the contacts is kept independent of resistivity. The mechanical design and the electronics of the probe are discussed in detail. The reproducibility of the measurements is found to be independent of resistivity in the constant voltage mode and is compared with the customary constant current mode. The (3σ) multioperator reproducibility of the measurements is better than ±0.39% for n-type silicon and ±0.65% for p-type silicon.
Description of an Apparatus Allowing Mechanical Tests under Hydrostatic Pressure up to 15 Kilobars
Authors: Carpentier D. , Contre M.
Published: February 2004

An apparatus allowing deformation experiments under hydrostatic pressure up to 15 kilobars is described. The pressure environment is a gas. The load measurement is performed under pressure and the load vs elongation curve is directly recorded during the test.
Liquid Helium Temperature cw NMR S/N Improvement Using a MOSFET rf Amplifier
Authors: Alderman D. W.
Published: February 2004

Improvement of the signal-to-noise (S/N) ratio of cw NMR spectrometers by cooling circuit components to liquid helium temperature is discussed. Criteria for design of a low temperature circuit using a twin-T bridge and MOSFET amplifier are presented. A liquid helium temperature spectrometer for operation at 16 MHz which improves S/N ratio by a factor of 5 over conventional techniques is described.
Equipment for Thermal and Differential Thermal Analysis to 3000°C
Authors: Baldwin N. L. , Langer S. , Kester F. L. , Hancock C.
Published: February 2004

The design and application of high temperature thermal analysis equipment is described in this paper. Radiation emitted from the inductively heated samples impinges on an ir semiconductor device, the output of which is amplified and displayed on an X-Y two-pen recorder. Small heat effects associated with condensed state phase transitions can readily be detected using the techniques of thermal analysis (TA), derivative analysis (DA), or differential thermal analysis (DTA). Solid state transformations found in thorium dicarbide are illustrated using the various TA techniques. Data presented for phase changes in the uranium present in hypostoichiometric uranium dioxide show that isothermal enthalpy changes of <7 cal can be detected by the TA apparatus when using the DA mode of operation.
Location of Primary Cosmic Ray Particles in Photographic Emulsion Using Spark Chambers
Authors: Goza E. R. , Krzywdzinski S. , Stafford E. G.
Published: February 2004

Spark chambers have been used in conjunction with photographic emulsion to investigate the accuracy and reliability in the location of primary cosmic rays in emulsion exposed at balloon elevations. The location of these primaries in the emulsion stack has been determined using measurements made on spark chamber photographs. A sample of 118 primaries with Z>1 which did not interact in the emulsion target has been used to calibrate the positions of the emulsions with respect to the spark chambers. The standard deviations of coordinate location errors in the emulsion plane and perpendicular to the emulsion plane were both 0.2 mm after calibration. The standard deviation of errors in the projected angles in the emulsions for these primaries was 0.2°. The mean and standard deviation of errors in the dip angles for these same events were 0.1 and 0.2°, respectively. A total of 191 out of 192 Z>1 primaries, and 24 out of 39 Z=1 target interacting primaries have been located in the emulsion without significant ambiguity. All the 63 Z=1 noninteracting primaries with energies greater than 50 GeV have also been located in the emulsions without any ambiguities. Scanning efficiencies for the Z>1 primaries and the Z=1 noninteracting primaries were both about 100%. The scanning efficiency for the Z=1 target interacting primaries was approximately 43%. The scanning time required for the location of Z>1 and Z=1 primaries which did not interact in the emulsion target was 2–3 h. Corresponding scanning times for the location of Z>1 and Z=1 target interacting primaries were on the order of 6–8 h and two to four days, respectively.
A Pulsed Electron Gun Suitable for Exciting Semiconductors to Inversion
Authors: Kramer B. M. , Stille R.
Published: February 2004

For the study of bulk properties of electron excited semiconductors, it is necessary to apply high energy electrons for excitation which have a large penetration depth. A pulsed electron gun designed for investigating semiconductors under high excitation is described. It generates rectangular electron beam pulses with current densities up to 20 A/cm2. The profile of the current density in the focus plane is of Gaussian shape, its half-width being up to 410 μ. The electron energy can be varied from 160 to 300 keV, the pulse duration from 20 to 1000 nsec with a shortest risetime of 5 nsec without deviating from rectangular shape. The repetition frequency can be varied from 50 Hz down to single shots. The pulses are triggered from earth potential allowing easy investigation of time dependent effects. As a first application, time behavior of laser action of CdS single crystals is reported.
Apparatus for the Calibration of Shear Sensitive Liquid Crystals
Authors: Klein Enrique J. , Margozzi Angelo P.
Published: February 2004

An experiment was designed in which shearing forces acting on a film of shear sensitive liquid crystals could be measured directly while additional instrumentation was used to measure the peak spectral intensity of the light scattered by the substance. A liquid crystals sample of low temperature sensitivity was tested and a calibration curve was obtained with a linear slope of 0.208 (g/cm2)/nm from 0 to 3 g/cm2.
Infrared-Visible Window Composite for Ultrahigh Vacuum
Authors: Roepke Wallace W.
Published: February 2004

This note describes a composite window design which will allow visual or photographic observation and permit ir irradiation of test materials simultaneously in an ultrahigh vacuum system. The uhv compatibility has been ascertained by irradiating the sealant materials with a CO2 laser while monitoring desorbed species with a quadrupole mass spectrometer.
A Field-Frequency Locked NMR Spectrometer for Knight Shift Measurements
Authors: Goodrich R. G. , Khan H. R. , Khan S. A. , Reynolds J. M.
Published: February 2004

An NMR spectrometer is described which allows a direct plot of the Knight shift in metals to be recorded. The device uses a wide field range field-to-frequency lock unit with the output of the entire spectrometer being directly proportional to the Knight shift. Preliminary results of the field dependence of the Knight shift in aluminum obtained using the spectrometer are given.
Techniques for the Measurement of Photoemission Energy Distribution Curves by the ac Method
Authors: Eden R. C.
Published: February 2004

A new circuit for measuring photoemission energy distribution curves (EDC's) by the ac retarding potential method is described which offers greatly improved noise performance over earlier circuits. General techniques for EDC noise reduction are outlined and the noise performance expected from different electrometer detectors is compared. A method for quantitatively evaluating the noise performance of an EDC measurement system from an experimental EDC is presented and applied to EDC's obtained with this new measurement system. Equivalent noise currents in energy distribution curves obtained with this system are found to be as low as 2 to 3×10−15 A rms. This low noise allows the measurement of EDC's with total dc photocurrents of less than 10−13 A.
Stress Dependence of Contact Potential: The ac Kelvin Method
Authors: Craig Paul P. , Radeka Veljko
Published: February 2004

Measurements of the influence of stress upon contact potential necessitate the observation of shifts in contact potential of the order of 100 μV or less. The ac Kelvin technique was selected to yield this sensitivity. The application of phase sensitive detection techniques to the ac Kelvin method is discussed, and the equations are solved. The success of the method depends upon the use of a guarded field effect transistor input stage located within the Kelvin probe. The effect of nonuniform contact potentials and nonuniform capacitor plate separation is analyzed, and conditions are given for the balance point to be independent of plate spacing. The stress dependent contact potential measurements may be continuously displayed using a new nonlinear second harmonic detection scheme. This method is discussed.
Effect of Magnetic Field Fluctuations in Spin-Echo NMR Experiments
Authors: Allerhand Adam
Published: February 2004

The effect of magnetic field drift and ripple on spin-echo NMR experiments is discussed with emphasis on Carr-Purcell spin-echo (CPSE) experiments. It is shown that magnetic field fluctuations dephase the echo maxima with respect to the pulsed rf signal phase. This makes it difficult to use phase sensitive detection in the presence of a large field ripple even when the average field is very stable. The effect of ripple is particularly serious in CPSE experiments because the Meiboom-Gill improvement of the CPSE sequence requires phase coherence of the echo signals. Closed equations are derived for the magnitude of the dephasing at a single echo and at the nth echo of a CPSE sequence, caused by linear magnetic field drift, sinusoidal ripple, and nonsinusoidal ripple. The results indicate that the effect of ripple is proportional to the ratio of its amplitude to its frequency, and that the effect on a CPSE sequence can be minimized by making the 180° pulse repetition rate large with respect to the ripple frequency. The results of various experimental tests are also given. They are in agreement with the theoretical predictions. The performance of several magnet systems is compared.
Adiabatic Fast Passage Method for Spin-Lattice Relaxation Time Measurements
Authors: Parker R. G. , Jonas J.
Published: February 2004

The apparatus for the adiabatic fast passage experiments used for the measurement of NMR spin-lattice relaxation times is described. The different experimental conditions and techniques for the T1 measurements of chemically shifted nuclei are briefly discussed.
Comparison of Hollow Cathode and Conventional Argon Ion Lasers
Authors: Jennings W. C. , Noon J. H. , Holt E. H. , Buser R. G.
Published: February 2004

A detailed comparison between an argon ion laser system utilizing the hollow cathode discharge (HCD) and one employing a conventional, externally heated oxide cathode, but with identical geometry, has established that there are no significant differences in their microscopic behavior, and that the excitational processes occurring in the two systems are the same. A comparison of the over-all efficiency of the two systems operating at the same output power level shows that when bariated tungsten cathode cylinders are used in the HCD, this device does not require greater input electrical power than the conventional device. It is further shown that operation of the HCD laser does not require a continuously flowing gas system as has previously been reported. This study shows the HCD to be an attractive alternative to conventional discharge geometries for ion laser systems.
A High Precision Ratio Potentiometer
Authors: Bishop R. L. , Barber R. C.
Published: February 2004

A high precision potentiometer has been constructed to determine the ratio of two voltages presented by the University of Manitoba second order mass spectrometer. The ratio can be determined to a precision of 0.4/ΔV ppm, where ΔV is the smaller of the two voltages. ΔV is variable from a few millivolts to several volts. For ΔV>4 V the precision remains near 0.1 ppm.
Design and Performance of a Pulse Radiolysis System Capable of Picosecond Time Resolution
Authors: Bronskill M. J. , Taylor W. B. , Wolff R. K. , Hunt J. W.
Published: February 2004

A unique stroboscopic pulse radiolysis system is described which detects the transient light-absorbing species formed in solutions by individual fine structure pulses from a 40 MeV linear accelerator. A measured time resolution of 23 psec is attained by using, as the analyzing light, the short (<10 psec) Čerenkov light flashes produced in air by the fine structure pulses of the electron beam. This light is suitably delayed by an optical system in which the path length is slowly changed, then passed through the irradiated sample. The integrated light passing through the sample id detected, and variations in the optical absorption at varying times after the irradiation pulse are observed. The design and performance of the optical, mechanical, and electronic devices which retrieve the absorption signal out of the noise are described in some detail. As an integrated unit, this system meets its expected performance capability, being able to successfully detect absorption signals as small as 0.2%.
Atmospheric Analysis Device for Balloon Experiments
Authors: Ponzi S. , Astor J. L. , Fontanari J. , Sanitas R.
Published: February 2004

A balloon borne apparatus has been designed to analyze atmospheric minor constituents: CO2, H2O, CH4. The sampling system, consisting of a compressor, delivers samples up to 35 km. Cyclic analyses are performed by gas chromatography. Concentrations as low as 1 ppm may be detected in air samples.
Study of the Electron Optical Properties of an Electron Spectrograph with Coaxial Cylindrical Electrodes
Authors: Aksela S. , Karras M. , Pessa M. , Suoninen E.
Published: February 2004

The article gives a general treatment of the electron optical properties of cylindrical electron spectrographs. The resolution, the transmission, and the ratio of them (figure of merit) for electrostatic spectrographs are computed and compared for various choices of focusing arrangement and location of the source and the image. The second order focusing, which occurs in the evaluation as an asymptotic case of the first order focusing arrangement, is shown to yield a figure of merit which is in most cases superior to first order focusing. Locating the source and the image at the cylinder axis is also found to be the optimal setup using this figure of merit as a criterion.
Electrochemical Meter for Activity Measurements in Natural Environments
Authors: Wilde Pat , Rodgers Peter W.
Published: February 2004

An electrochemical meter designed for measurements in the marine environment but equally useful in other natural environments is described. Some features of the instrument are (1) all input channels are high impedance; (2) up to 11 reading electrodes can be monitored from one reference electrode; (3) voltages are measured with respect to solution ground; (4) a null balance circuit option; (5) an accuracy of better than 1 mV. With suitable operative ion-selective electrodes, the instrument can monitor (a) operational activities, (b) activity ratios, (c) solubility products, or (d) states of saturation.
Studies of a Plasma Wind Tunnel for Simulating the Collisionless Bow Shock of the Earth
Authors: Condit William C.
Published: February 2004

Formulas are given for the plasma density and velocity required to simulate the flow of the solar wind over the magnetosphere of the earth. A description of a plasma source (coaxial arc-jet) intended to produce appropriate plasma flows is given. The operation of the device is described. Preliminary measurements of the density and velocity, made with a bolometer and a ballistic pendulum, indicate that plasma densities of 1013/cm3 and velocities of 107 cm/sec have been achieved in a jet of 1 m diameter. These parameters have been verified by microwave and Langmuir probe measurements and are appropriate for the desired simulation. In addition, it has been shown for the first time that this plasma has the required percentage ionization for solar wind simulation.
A Dual-Disk Chopper for Time-of-Flight Measurements
Authors: Young Wen S. , Rodgers Wayne E. , Knuth Eldon L.
Published: February 2004

A novel dual-disk chopper for time-of-flight (TOF) measurements is described. Analytical expressions relating the dual-disk TOF signals to the density and the pertinent parameters of the speed distribution function of a molecular beam are presented. It is demonstrated that use of this new chopper simplifies greatly the experimental and data reduction procedures by obviating, for the determination of most molecular beam parameters, the need for information concerning the gate function of the chopper, the dynamic function of the detector and its electronics, and the absolute zero-time reference point.
A High Precision Electron Diffraction Unit for Gases
Authors: Fink M. , Bonham R. A.
Published: February 2004

An electron diffraction unit using counting techniques has been built which makes it possible to record relative total (elastic and inelastic) differential scattering cross sections directly. Features of the unit which deviate from those in conventional units (which incorporate a rotating sector and photographic plates) are described in detail. The possible uses and limitations of the new instrument are discussed. The total scattered intensities in the range 1.5≤s(Å−1)≤7.2 with 40 keV electrons from N2O and CO2 are presented as examples. The results are compared to the predictions of the independent atom model and differences due to chemical binding and electronic correlation effects are observed.
A New Type Planimeter
Authors: McGinn John H.
Published: February 2004

A wheel which is mounted in a carriage is held in nonsliding contact with the surface of a cylinder. Both translation of the carriage parallel to the cylinder and the angle that the plane of the wheel makes with the axis are coupled mechanically with the motion of a stylus. Tracing the boundary of a closed figure of arbitrary shape causes the cylinder to rotate. It is shown that the total rotation is directly proportional to the enclosed area. Details of construction and some estimates of accuracy are also given.
Measurement of Minor Reactance Changes with Synchronized Electronic Oscillators
Authors: Dalins Ilmars
Published: February 2004

The use of ``phase modulated'' synchronized electronic oscillators is discussed in considerable detail, including the theoretical background as well as practical circuitry for measuring minor reactance changes (capacitance as low as 0.00004 pF or correspondingly low inductance). The proposed circuitry has some definite advantages over certain other schemes and has been used for some time in seismographic and other instrument design where remote sensing, taking advantage of reactance changes, is employed.
Fast Accurate McLeod Gauge System
Authors: Richman Edward , Wharton Lennard
Published: February 2004

The use of an orifice and a secondary mercury source near it as means for reducing the trap pumping error of the McLeod gauge is discussed. With the proper utilization of an orifice, trap pumping is not a serious hindrance to the use of the McLeod gauge as a primary pressure standard. Accuracy better than 1% with a time constant less than 30 sec can be achieved using a conventional McLeod gauge. Experiments that directly demonstrated a reduction of the trap pumping error gave good agreement with the theoretically expected reduction.
Ratiometer for the Measurement of Mass Abundance Ratios with a Quadrupole Mass Spectrometer
Authors: Yinon J. , Klein F. S.
Published: February 2004

A device is described which, attached to a quadrupole mass spectrometer, permits the selection of any two mass peaks and the measurement of the abundance ratio of the selected masses. The principle of operation of the ratiometer is to focus alternately the two masses onto the collector by applying a periodic square wave voltage to the input of the rf/dc generator. The resulting signals are fed into two channels and converted into two direct voltages. The ratio of these voltages, which are proportional to the two ion peaks, is then measured and displayed by a digital ratiometer.
Merging of Multichannel Signals and its Application to Molecular-Beam Time-of-Flight Measurements
Authors: Young W. S. , Winicur D. H. , Rodgers W. E. , Birely J. H. , Knuth E. L.
Published: February 2004

A technique for merging multichannel signals in order to improve greatly the time resolution of the output signals recorded by a multichannel signal averager is described. The determination of the input signal frequency for optimum merging effect is emphasized. A dual-disk time-of-flight argon signal extracted from an arc heated argon-helium beam is presented as an example; signal merging improved the time resolution from 39 μsec to from 5 to 7 μsec.
The Design and Performance of a Gas Čerenkov Counter with Large Phase-Space Acceptance
Authors: Hinterberger H. , Lavoie L. , Nelson B. , Sumner R. L. , Watson J. M. , Winston R. , Wolfe D. M.
Published: February 2004

We describe the design and performance of a threshold gas Čerenkov counter used to detect electrons from lambda beta decay. To achieve the very large phase-space acceptance required, the counter incorporates a novel technique of light collection, the light funnel which we developed for this purpose. By means of the light funnel one can, in principle, make the entire phase-space acceptance of a photomultiplier tube useful for particle detection.
High Quality Sputtered Multilayer Coatings for Infrared Laser Applications
Authors: Gaver R. L. , Seguin H. J.
Published: February 2004

This paper reports on experiments utilizing a low pressure triode sputtering technique for the fabrication of high quality multilayer mirrors for ir laser applications.
A Programmed Digital IC Pulse Generator for Transient NMR Spectrometry
Authors: Franconi C. , Terenzi M.
Published: February 2004

A pulse pattern generator for NMR spectrometry using SGS micrologic IC's for the logic and counters is described. Time intervals between pulses, gate times controlling the number of pulses in a sequence, and delay times controlling the sequence repetition rates are all digitized. Auxiliary pulse outputs to use as suppression pulses, for controlling delay lines, and for gated signal averaging devices are provided. The pulse sequences are those most commonly used in relaxation times measurements, including T1ρ. The generation of further sequences and the possibilities of using the flexible logic of this apparatus for extending its use are discussed.
Simplified Direct Speed Measurements of Nonrepetitive Signals
Authors: Wittig Sigmar L. K. , Mlynarik J. Martin , Borsare David C.
Published: February 2004

A method is described for measuring speed directly without the necessity of any subsequent calculations. Using basically the method of discharging a capacitor through a resistor the advantage consists in matching the voltage to the hyperbolic velocity vs time relation. Thus, by giving a direct speed readout, this inexpensive design is preferable in many cases to the generally used counters and oscilloscopes. Speeds in practically all ranges can be measured and accuracies within fractions of a percent can be achieved. This opens wide fields of application in ballistics, gas dynamics, and primarily in shock tube techniques.
High Pressure Apparatus for Gaseous Hydrogen and Deuterium up to 25 Kilobars and Temperature Range −50 to 100°C
Authors: Wiśniewski Roland
Published: February 2004

A high pressure device for gaseous hydrogen and deuterium in form of a double piston-cylinder system is described. Any contact between gaseous volume and the pressure transmitting liquid is avoided. The device has 15 electrical leads from gaseous volume to the outside of the apparatus. Resistance data for palladium under hydrogen and deuterium pressures are presented.
Resistance Comparisons at Nanovolt Levels Using an Isolating Current Ratio Generator
Authors: Crovini L. , Kirby C. G. M.
Published: February 2004

A circuit has been developed for the generation of isolated currents having precisely defined ratios. It can be used to compare resistances with accuracies up to 0.03 ppm and with sensitivities as low as 1 nV. When comparisons are made using low frequency currents, thermal emf's are eliminated. Several variations of the circuit which can be made easily in the laboratory are described.
Fast Polynomial Function Generator
Authors: Radeka V. , Rogers E. J.
Published: February 2004

A direct coupled function generator has been developed which provides a fourth degree polynomial function in times of the order of 100 nsec. Analog multipliers utilizing field effect transistors are used. A unique circuit configuration allows the generation of a fourth degree polynomial having individually adjustable coefficients with only two multipliers. The instrument, operating at 5 V input and output levels, achieves an accuracy of 1% for the lower order terms and 2% for the higher order terms.
Construction of a Screen Manipulator and Its Application in Parallel Section X-Ray Topography
Authors: Caslavsky J. L.
Published: February 2004

The quality of transmission diffraction topographs is strongly dependent on many experimental factors. Among them the fixed screen is one of the more important elements. A new design of a good performing screen manipulator is described and its practical application to the ``parallel section'' x-ray topography is discussed.
Apparatus for Surface Temperature Studies in Vacuum
Authors: Vasilakis J. D.
Published: February 2004

An apparatus is described for the measurement of temperature near the interface of bodies sliding in a vacuum. The rotating element or slider is electromagnetically suspended inside the vacuum system and rotated with an induction motor positioned outside the vacuum system. Because of the suspension system, the only contacts in the apparatus are the stationary elements or riders acting on the slider. The temperatures measured near the sliding interface can be used in analysis as boundary points to provide the temperature and temperature gradient at the interface of each element. The juncture condition of continuity of temperature and its gradient can then be checked. To avoid unnecessary contacts in the system, the temperatures on the slider are telemetered out of the vacuum system by transmitters located on the slider. Thermocouples are used to measure temperature on the rider. The vacuum system is hermetically sealed, with suspension and rotation being affected from outside the vacuum system. The torque in the system and the normal load of the rider are also measured. The maximum sliding speed is 39 cm/sec and a vacuum of the order of 10−3 Torr was used. Results are given for Teflon sliding on steel.
Magnetic Thermometry
Authors: Anderson A. C. , Peterson R. E. , Robichaux J. E.
Published: February 2004

The paper describes a highly stable ac mutual inductance bridge suitable for low temperature use. The application of the bridge to magnetic thermometry below 3 K is discussed.
A Technique for Launching Intermediate Velocity Thin Plastic Sheets
Authors: Dueweke Paul W.
Published: February 2004

Short duration pressure pulses generated by impacting samples with thin plastic sheets, or flyers, are being widely used to investigate dynamic materials properties. Peak pulse pressures are directly dependent upon impact velocity. Two types of exploding foil launchers are currently available that can produce flyer velocities of 0–0.4 and 0.8–4.0 mm/μsec. A ``velocity gap'' has existed between 0.4 and 0.8 mm/μsec which has limited the usefulness of the over-all technique. A third launcher design has been developed that can accelerate flyers to velocities between 0.4 and 0.8 mm/μsec. The new design uses a free expansion gas chamber to moderate the performance of the older high velocity launcher. This design produces flyers with planarities usually less than 0.4 mm.
A High Pressure Optical Vessel for Corrosive or Sensitive Liquid Samples
Authors: Hawley S. A. , Chase C. E.
Published: February 2004

This paper describes a pressure vessel which accommodates optical measurements in liquid samples in the pressure range extending to about 4000 kg/cm2 and is designed to be used in conjunction with corrosive or sensitive materials. The sample is enclosed in such a manner as to contact only a Teflon compartment and the window surfaces. Simplicity of design is achieved by forming the high pressure seal on the inside window surfaces, an expedient which also permits the inclusion of more than one sample cell in the pressure vessel.
A Trapped Ion Analyzer Cell for Ion Cyclotron Resonance Spectroscopy
Authors: McIver Robert T.
Published: February 2004

Ion cyclotron resonance spectroscopy has been adopted for the detection of gaseous ions formed within an analyzer cell of new design. Ions formed by electron impact have been trapped within the analyzer cell for as long as 0.10 sec and detected with a half-height mass resolution of 5000. Even at pressures of 10−5 Torr ion-molecule reactions of high kinetic order may be observed. An important feature of the trapped ion analyzer cell is that it retains the capability of the ICR double resonance experiment for elucidating the reaction sequence occurring in a complex mixture of primary ions and high order product ions. A pulsed magnetic field detection scheme accurately limits the residence time of the ions within the trapped ion analyzer cell.
Criterion for Comparing Analyzers
Authors: Sar-El H. Z.
Published: February 2004

In view of the recent development of several new electrostatic analyzers, the need arises for a criterion for comparing their figures of merit. A criterion usually used in β spectrometry is proposed and is shown to be preferable to another criterion proposed recently.