bluuebunny/crossref_metadata_2025 huggingface dataset:
Infrared Techniques for Fused Salts
Authors: Bandy Alan , Devlin J. Paul , Burger Ronald , McCoy Billy
Published: February 2005

By capitalizing on the unusual properties of ultrapure silicon, two methods of measuring the infrared spectra of molten salts have been developed. Silicon is used as a cavity cell in one method, while in the second method a silicon reflecting prism allows the measurement of attenuated total reflection spectra. The two methods combined permit routine measurement of the infrared spectra of many molten salts for path lengths greater than the wavelength of the radiation. The utility of these techniques is exemplified by data for fused lithium nitrate.
MURA 50-MeV Electron Accelerator—General Description and Review. I
Authors: Cole F. T. , Parzen G. , Pruett C. H. , Wallenmeyer W. A. , Young D. E.
Published: February 2005

General descriptions of the history, construction, and operation of the MURA 50-MeV electron accelerator are given. In its operation, this accelerator has been used to stack large circulating currents of accelerated particles and to investigate multiturn injection, acceleration processes, resonant effects, and collective instabilities.
Equipment and Procedures Used in Magnetic Field Measurements on the MURA 50-MeV Electron Accelerator. VII
Authors: Mulady J. R. , Bush G. E. , Haxby R. O. , Pruett C. H. , Wallenmeyer W. A.
Published: February 2005

Magnetic field measuring equipment and procedures used in measuring the magnetic guide field of the MURA 50-MeV electron accelerator are described. Systems for measuring the field gradient index and the vertical, radial, and azimuthal components of the field on the median plane are considered. Methods of using these systems to attain field measurement accuracies of the order of 0.1% in a very inhomogeneous field ranging in magnitude from 20 to 5000 G are discussed.
Injector for the MURA 50-MeV Electron Accelerator. IX
Authors: Curtis C. D. , Mills F. E. , Christian R. S. , Lee G. M. , Radmer C. A. , Shea M. F. , Swenson D. A.
Published: February 2005

An electron gun and an inflection system which satisfy the injection requirements of the MURA 50-MeV electron accelerator are described. Electrons emitted from a tungsten ribbon filament are accelerated to 100 keV by a converging radial field of cylindrical geometry and deflected parallel to the equilibrium orbit of the accelerator by a 60° electrostatic inflector. The inflector also provides focusing of both the radial and vertical motion of the beam. The gun and inflector are located within the guide field region of the magnets and are adjustable in position as a unit. The emittances of the system are 0.5 π and 1.0 π mrad-cm for the horizontal and vertical motions, respectively. Although the injector is capable of delivering several hundred millamperes, it is normally operated at much lower currents since fewer than 20 mA are required to reach the space-charge limit of the accelerator when multiturn injection techniques are employed.
Multiturn Injection Techniques in the MURA 50-MeV Electron Accelerator. X
Authors: Mills F. E. , Curtis C. D. , Peterson F. L. , Radmer C. A. , Shea M. F. , Swenson D. A. , Young D. E.
Published: February 2005

Multiturn injection techniques employed in the MURA 50-MeV electron accelerator are described, together with an evaluation of their performance. These include shifting of the equilibrium orbit by a time-varying bump, damping of betatron oscillation amplitudes by an rf voltage, and damping of amplitudes by space-charge effects. Multiturn injection is achieved by filling the accelerator radial phase space with injected beam. The capture of injected charge approaches 100% when the programmed field bump is used. This high efficiency has been achieved for about 15 turns of total beam from the inflector and for about 40 turns of collimated beam. Injection at the higher beam intensities gives rise to spontaneous longitudinal bunching of the circulating beam for all energies from injection to above transition with the magnitude generally greatest just above transition.
Control and Protection Systems for the MURA 50-MeV Electron Accelerator. XIV
Authors: Peterson F. L. , Radmer C. A.
Published: February 2005

The control system for the MURA 50-MeV electron accelerator is designed for maximum versatility consistent with ease of operation and personnel and component protection. Since the purpose of this project is to study many different accelerator phenomena, and the accelerator is capable of producing intense background radiation, it must be capable of functioning in several modes of operation and observation with adequate safety precautions. In addition to the flexible injection, acceleration, and beam stacking controls, accurate probe positioning devices are needed for detailed analysis of beam characteristics. Numerous limiting interlocks on various components and systems are also necessary because of the extremely tight tolerances involved. A description of some of the major control elements is presented and the over-all system described.
Temperature Measurement in Thermogravimetry
Authors: Manche Emanuel P. , Carroll Benjamin
Published: February 2005

A method is described whereby the temperature of a sample in a thermobalance may be determined directly without the large uncertainty that usually accompanies these measurements. The procedure consists of using a unijunction transistor relaxation oscillator with a thermistor as the resistive part. The entire primary circuit including the power supply is made part of the balance suspension and is weighed along with the sample. The frequency of oscillation which is a function of sample temperature is relayed to an events-per-unit-time meter via a mutual inductance between two suspended coils. The nonlinearity of the thermistor is removed to a considerable extent by a compensating circuit.
Temperature Compensation of Transistor Integrator
Authors: Wang C. P.
Published: February 2005

It is shown that the temperature dependence of (ICEO)inverted of an inverted transistor can be very effectively used for temperature conpensation. Conditions were derived for complete compensation of an integrator amplifier with emitter follower output and single-stage amplifier. Both compensations were used in the integrator unit incorporated in a delay time electronic servo, giving a temperature stability of better than 0.01 V/°C at the integrator output, or better than 5 nsec/°C at the servo output. Smaller drift can be achieved, if desired, with more careful choice of transistor types and transistors for compensation.
Reproducible Magnetic Field Sweep
Authors: Blume R. J. , Williams W. L.
Published: February 2005

The need for a reproducible and jitter-free magnetic field sweep in high resolution NMR (nuclear magnetic resonance) is discussed, and one means of approaching the ideal is reported in detail. A magnetic field of 11.7 kG is phase-locked to a digital frequency synthesizer. The field-to-frequency transducer is a Pound-Freeman super-regenerative NMR detector. The magnetic field sweep can be stepped reversibly in increments as small as 0.01 cps (2.35×10−6G for protons). Smaller steps are readily obtained. The spectral purity of the magnetic field is 1.6 parts in 1010 for a 1-sec average. The long term stability approaches that of the master crystal oscillator. It is proposed that the synthesizer, and therefore the magnetic field, be controlled directly by the address selector in a continuous averaging memory. The present system appears to make feasible NMR spectroscopy with a resolution of ≲0.01 cps.
Time-Resolving Infrared Polarization Analyzer for the 2- to 4-μ Range
Authors: Craig John P. , Gribble Robert F. , Dougal Arwin A.
Published: February 2005

A polarization analyzer for time-resolved rotation measurements of polarized infrared radiation from 2- to 4-μ wavelength is described. The instrument employs air-germanium interfaces, uncooled InAs photovoltaic detectors, and 10-Mc-bandwidth low noise preamplifiers. Angular resolution of approximately ½° for polarization oscillations as high as 1 Mc is obtained for ½-mW emission from a He-Ne maser at 3.39 μ. It is useful, with reduced resolution, up to 10 Mc; the resolution can be improved through reduced preamplifier bandwidth for below 1 Mc. Application of the instrument to measurement of the Faraday rotation of a 3.39-μ polarized maser beam propagated through a dense, high temperature, deuterium plasma in an intense magnetic field is discussed.
Reflection Properties of Deflecting Magnet Systems
Authors: Bliamptis E. E.
Published: February 2005

Certain properties of mirror symmetric magnet deflection systems are derived. By suitable choice of parameters, such as the radii, angles of deflection, angles of incidence, and component separations, a magnet system may be designed which, to first order, is achromatic, nondispersive, and has high resolving power. The resulting constraints are given in terms of the matrix elements of the first half of the deflection system.
High Resolution Gas Čerenkov Counter—DISC
Authors: Duteil P. , Gilly L. , Meunier R. , Stroot J. P. , Spighel M.
Published: February 2005

The limit set by chromatic dispersion on the velocity resolution of Čerenkov counters can be reduced by more than an order of magnitude by optical correction of chromatism. Performance of a counter built according to this principle is presented, showing ability to separate particles differing in velocity by only a few parts in 106.
Charcoal Trap with Rapid Thermal Response
Authors: Coffin Don O.
Published: February 2005

A charcoal trap for separation of gases by selective adsorption is described. Unique features claimed for the design are (a) operation to 300°C without auxiliary heaters, (b) rapid thermal cycling over a 500°C range, and (c) modular construction adaptable to a wide range of capacities.
Far-Infrared Circular Polarizer
Authors: Richards P. L. , Smith G. E.
Published: February 2005

This paper describes several devices (circular polarizer, isolator, circulator) which will be useful for the manipulation of far-infrared radiation. These devices depend on the properties of a class of magneto-rotary solids which are operated at or near their cyclotron resonance frequency. Experimental results on the use of InSb as a circular polarizer are described.
Dielectric Cavity Resonator for ESR Experiments
Authors: Rosenbaum Fred J.
Published: February 2005

A high Q, open boundary, microwave, resonant cavity suitable for electron spin resonance (ESR) spectroscopy is described and design data presented. The resonant structure employs a dielectric tube or rod separating two metal endplates. Samples may either be placed in the tube or prepared as rods and employed directly as the resonant medium. ESR measurements involving (1) the perylene ion, (2) Mn(II) in dilute sulfuric acid, and (3) ruby are reported to demonstrate the application of this device.
Total Absorption Coincidence Spectrometer
Authors: Grenier R. P. , Samuelson R. R.
Published: February 2005

A total absorption beta-gamma coincidence spectrometer utilizing anticoincidence shielding is described. The main detector assembly consists of two NaI(Tl) well crystals each 22.9 cm in diameter by 12.7 cm thick. The wells in the crystals are each 5 cm in diameter by 3.8 cm deep. The crystals are positioned to face each other and present a 4π geometry to the source of activity. A 4π beta chamber operated in the Geiger region is positioned inside the wells. A 7.6-cm-thick plastic phosphor serves as an anticoincidence guard. The system may be used in a variety of double and triple coincidence configurations. The responses of the crystals to gamma rays under various coincidence conditions are included. The facile determination of absolute disintegration rates obtainable with this system by using the coincidence technique and detectors that present a uniform sensitivity to the source of activity is discussed. Experimentally determined total gamma efficiency and peak-to-total ratio vs energy curves are presented and the techniques and isotopes used to obtain them are discussed. In the region from 70 to 2800 keV the 4π crystals have gamma efficiencies ranging from 0.765 to 0.645, respectively, with a max efficiency at 530 keV of 0.895. The peak-to-total ratio ranges from 0.92 at 70 keV to 0.47 at 2800 keV.
Dewar System to Attain −140 to 550°C in an NMR Crosscoil Probe
Authors: Schreiber D. S.
Published: February 2005

An L-shaped glass Dewar and associated thermometry which will provide temperatures from −140 to 550°C in a conventional NMR crosscoil nuclear induction probe is described. A particular temperature is maintained by streaming hot or cold nitrogen gas around the sample. Details on the relatively simple construction and mounting of the Dewar in the probe and of heating and cooling the nitrogen heat exchange gas are discussed.
Magnetohydrodynamic Flow Angle Indicator
Authors: Fuhs Allen E. , Gibb O. L.
Published: February 2005

By using the directional sensitivity of the electrical conductivity instrument, it is possible to measure the direction of the flow of a conducting gas. If only one coil set is used, a complex calibration procedure is necessary; however, by using two coil sets, the flow angle becomes a function only of the ratio of two signals. It is shown theoretically, and verified experimentally, that the signal varies as the cosine of the flow angle. The flow angle can be expressed analytically as a function of signal ratio. Calculated and observed signal ratios are in agreement. The precision of measurement is ±(1°+5%) for flow angles of +45 to −45°.
Electrometer for Ionization Chambers Using Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: McCaslin Joseph B.
Published: February 2005

A pair of unguarded metal-oxide-semiconductor field-effect transistors has been used to measure ionization-chamber currents in the range 10−15 to 10−8 A. A portable instrument has been constructed which has an input leakage current less than 10−16 A. It exhibits a high degree of stability, circuit simplicity, ruggedness, low drift, and 0.7-mA drain, which will permit continuous operation for several months. Also, guarded MOS devices, investigated for this application, have been found to have leakage currents in the region of 10−18 A.
Pulsed-Beam Low Energy Electron Diffraction System for Rapid Precision Measurements
Authors: Park Robert L. , Farnsworth H. E.
Published: February 2005

A pulsed-beam low energy electron diffraction (LEED) system using the electrical method of detection has been developed, by means of which the reciprocal lattice of the surface structure is obtained as an oscilloscope display. In addition, a precise plot of the intensity of a given diffraction beam as a function of electron energy can be obtained in reduced form as an oscilloscope pattern. The system employs a moving Faraday collector and a rotating crystal to scan the diffraction pattern. The pulsed beam permits measurements by ac techniques.
Design of a Mercury Vapor Target X-Ray Tube
Authors: Bearden J. A. , Huffman F. N. , Spijkerman Jon J.
Published: February 2005

A mercury vapor target x-ray tube has been constructed and utilized for bremsstrahlung studies. An electrically heated boiler at the bottom of the target chamber vaporizes mercury which is expanded through a nozzle to form the target. The mercury jet expands into a water-cooled condenser at the top of the target chamber and the liquid mercury is returned to the boiler. A Pierce type electron gun provides the bombarding beam which exits from the high vacuum beam-formation region through a 3-mm-diam aperture into the higher pressure target chamber. The radiation produced can be observed from ports in the target chamber wall. The apparatus is operable up to 30 kV with beam currents as high as 50 mA. The equivalent solid thickness of the target ranges up to 500 Å, which yields a photon intensity near the high frequency limit comparable to that from a solid target. Design and operational features of the device are discussed.
Alternate Approach to the Resolution of Tunneling Current Structure by Differentiation
Authors: Patterson William R. , Shewchun J.
Published: February 2005

Structure in the current-voltage characteristics of tunneling junctions is very clearly revealed by displaying the second derivative of current with respect to voltage (d2i/dv2) as a function of junction bias. Equipment for doing this was first described by Thomas and Klein. This paper describes an alternate approach to the recovery of the first and second derivatives using a transistorized electronic circuit which, in addition to being compact and rather inexpensive, provides as good, if not better, resolution than that previously reported. The current-voltage characteristic of a typical silicon tunnel diode at 4.2°K and the first and second derivatives of this characteristic using the apparatus described are given.
Orbitron Vacuum Pump
Authors: Douglas Ross A. , Zabritski J. , Herb R. G.
Published: February 2005

A pump was constructed in a casing 10 cm in diam in which electrons are orbited around a central anode consisting of a tungsten rod supporting a titanium cylinder. Electrons have mean free paths of several hundred centimeters, they ionize inert gas and they heat the titanium cylinder to give sublimation. Some values determined for pumping speeds when sublimation rate is sufficient are 900 liters/sec for hydrogen, 500 liters/sec for nitrogen, 300 liters/sec for air, and 7 liters/sec for argon. Sticking probabilities were measured for active gases and for inert gas ions as a function of the ratio of atoms of gas bound to atoms of titanium deposited. The pump is very stable in operation; it is simple and dependable.
Single-Crystal Filters for Attenuating Epithermal Neutrons and Gamma Rays in Reactor Beams
Authors: Rustad B. M. , Als-Nielsen J. , Bahnsen A. , Christensen C. J. , Nielsen A.
Published: February 2005

The total neutron cross sections of representative, single-crystal samples of bismuth and quartz have been measured at room and liquid nitrogen temperatures over the neutron energy range of 0.0007 to 2.0 eV to obtain data for the design of single-crystal filters for attenuating fast neutrons and gamma rays in reactor beams. The epithermal neutron and gamma-ray transmissions of these crystals, calculated from cross sections given in various compilations, are also presented graphically. From this information, filters composed of one or both crystals may be constructed to optimize beam characteristics for low energy neutron experiments. The design and performance of the 32-cm bismuth, single-crystal filter at the Danish DR-3 reactor are described. The average thermal transmission of a typical reactor beam through this filter is 16%. In the wavelength region from 5 to 15 Å, the transmission is 72%. Neutron intensity in the resonant energy region is attenuated by a factor of 5000, and gamma rays of all energies by more than 5×105. The filter improved the Cd ratio of the reactor beam by a factor of 800.
New Method of Observing the Phase Oscillations in a Synchrotron
Authors: Crebbin Kenneth C.
Published: February 2005

This report covers a new method of displaying the signal from a beam-induction electrode signal in a synchrotron. A dual-axis time display is produced by using a ramp and a series of trigger pulses, generated from the rf, to produce a raster on an oscilloscope. The results give a picture that retains the details of a fast sweep and at the same time covers a relatively long time period.
Combined Calorimeter and Spectrophotometer for Observing Biological Reactions
Authors: Berger Robert L. , Stoddart L. Charles
Published: February 2005

A stopped-flow fast reaction apparatus is described which permits chemical reactions with rate constants of 50 sec−1, or less, to be followed both spectrophotometrically and calorimetrically. The thermal detector is a single copper-constantan thermocouple, 5μ thick, with a response time of 3 msec. Using a bandpass of 0 to 80 cps, the signal-to-noise ratio is 1:1 for a heat change of 100 μcal/ml. The apparatus is housed in a 30×30-cm aluminum cylinder which is temperature stable to ±0.00001°C; reactants can be brought to within 0.001°C of equilibrium in less than 1 h. Acrylic light pipes are employed in the optical detection system to conduct a monochromatic light beam to the observation tube and to conduct the transmitted light to a photomultiplier. Solenoid valves control the mixer inputs; a third solenoid valve stops the flow in 2 msec. The thermal system and calorimeter were analyzed mathematically and two computer programs developed which make corrections for the response time of the system, correct the data for heat diffusion from the observation tube during the reaction, and calculate the first-order rate constant. The dehydration of carbonic acid was used as a test reaction. Experiments run at 3.8, 18, 24.1, and 36.9°C, using 0.04 molar NaHCO3 and 0.02 M HCl gave results thermally of 3.12, 15.8, 22.7, 49 sec−1 and optically of 3.15, 15.1, 20.6, for the rate constant and 2100, 1413, 970, and 460 cal/mole for ΔH.
Fast Recovery, Low Noise Transistorized Voltage Regulator for Tungsten Lamps
Authors: Berger Robert L. , Peterson Jerald M. , Budge E.
Published: February 2005

A solid-state voltage regulator was developed to supply 12 V at up to 5 A to a fixed load (two tungsten lamps) of approximately 4 Ω. The circuit employs a high gain operational amplifier in the feedback loop and the reference potential is supplied by a temperature-compensated Zener diode in an impedance cancelling bridge. The complete system has a line regulation of 4.5×10−4% for line variations from 100 to 130 V. The dc output impedance for the regulator is 0.003 Ω and the ripple is less than 5μV peak-to-peak at full load. Transient recovery is 120 μsec no load to full load.
Interferometer for Aerodynamic and Heat Transfer Measurements
Authors: Goldstein R. J.
Published: February 2005

An interferometer for use in aerodynamic and heat transfer studies has been designed and tested. As in a Mach-Zehnder interferometer, the light beam is large in cross section (to permit a large field of view in the test apparatus) and traverses the test section only once. Using a continuous wave laser as a source, the light beam is split and eventually recombined when small in cross-sectional area. This permits all optical components, other than two paraboloidal mirrors, to be much smaller than the field of view in the test section. The new design results not only in a less expensive unit, since most of the components are small, but also one that is much simpler to adjust than a conventional Mach-Zehnder interferometer.
Production of Dense Beams of Low Energy Ions
Authors: Kofoid M. J. , Braams C. M. , Zieske P.
Published: February 2005

Dense beams of positive ions of less than 1.0 keV energy have been produced using a duoplasmatron with an extraction voltage of 20 kV as a source. Outward radial electrostatic forces due to space charge impose a restriction upon the intensity of an ion beam while it is being formed in vacuum. This paper discusses the problem of designing the electrostatic lens system for decreasing the energy of the ions while simultaneously focusing them to produce a maximum density parallel beam. The system consisted of a unipotential lens, which was integral with the source (Radiation Dynamics type DY-1), and two additional immersion lenses. Most of the deceleration and beam compression was accomplished in the last lens. Its design was the major problem. Because a fairly exact analysis would have been very complicated, a simple approximate method for designing this lens was devised. The design values of current in the final low energy beam checked well with those from experiment.
Magnetic Double Resonance Spectrometer for Dynamic Nuclear Polarization and Relaxation Time Measurements at 175 G
Authors: Grützediek H. , Kramer K. D. , Müller-Warmuth W.
Published: February 2005

A magnetic nuclear-electron double resonance spectrometer operating in magnetic fields of about 175 G is described. It is suited for measurements of dynamic nuclear polarization and relaxation times in proton and fluorine containing solvents. The NMR spectrometer is a Q-meter device synchronized by a crystal oscillator. The uhf setup for the saturation of the ESR lines consists of a frequency multiplied driver stage and a 493 Mc power stage. The sample is placed inside a quarter wavelength coaxial cavity with the NMR coil around it. A rapid modulation technique allows u-mode detection and convenient comparison of NMR signals with and without ESR irradiation. The nuclear relaxation times (T2) are measured by observing the decay of the magnetization brought into the x,y plane by an adiabatic passage in the presence of a strong rf field. The performance is demonstrated with examples of proton polarization studies in organic solutions of free radicals.
Microscopic Measurement of Step Movement during Crystal Growth by Chemical Vapor Deposition
Authors: Seltzer M. S. , Albon N. , Paris B. , Himes R. C.
Published: February 2005

The design and operating procedure of apparatus for direct microscopic measurement of step movement during crystal growth is presented. The equipment consists of a microscope for observation of growth features, a reaction cell, furnace, and gas-flow control system. The apparatus has been employed to investigate growth mechanisms operative during the deposition of germanium by dissociation of GeI2 in an open tube flow system.
Sensitive Detector for Metastable He+(2S) Ions
Authors: Harrison M. F. A. , Dance D. F. , Dolder K. T. , Smith A. C. H.
Published: February 2005

Singly charged helium ions excited to the 22S½ metastable state were detected by counting the 40.8 eV photons emitted when the ions were quenched in a static electric field. High sensitivity was achieved by using a photomultiplier whose photocathode almost completely surrounded the quenching field. The efficiency of the detecting system was estimated to be (8.3±2.6) 10−3 and the sensitivity was adequate to measure a total flux of 103 He+(2S) ions/sec present in a 1 μA beam of 5 keV ground state He+ ions. The lifetime, τ[sec], of the 22S½ state of He+ was measured as a function of quenching field, U[V/cm], and was found to be τ=(1.4±0.2) 10−2/U2.
Variable-Frequency Radially-Stable Micrometeoroid Accelerator
Authors: Becker D. G. , Friichtenicht J. F. , Hamermesh B. , Langmuir R. V.
Published: February 2005

A linear accelerator for micrometeoroids, employing a Wideröe-Sloan-Lawrence configuration, is described. The accelerator is operated in the radially-stable mode, and the frequency of the accelerating voltage is automatically adjusted to accept charged microspheres with q/m∼1−300 C/kg. The waveform applied is a ``drooping square wave'' which allows focusing adjustments to be made independent of frequency and phase. The change in phase over 93 gaps can be kept sufficiently small by proper selection of droop and other parameters so that acceleration occurs at all gaps. Injection is at 1.6 MV from a modified Van de Graaff. The linac adds an additional 9.3 MV. Speeds up to 70 km/sec should be reached with 0.1 μ diam microspheres.
Improved Field Meter for Electrostatic Measurements
Authors: Gathman Stuart G. , Anderson Robert V.
Published: February 2005

An instrument system for the measurement of electrostatic fields is described. The use of more than 40 dB of negative feedback in the amplifier results in a sensitivity stable to within 1%. Careful attention to grounding and to surface preparation in the transducer head results in a zero level stable to within 1 V/m in ideal conditions. The effect of atmospheric variations in limiting the usable sensitivity is demonstrated.
Time-Sharing Modulation at 200 kc Applied to Broad and Narrow Line NMR for Base-Line Stability
Authors: Baker E. B. , Burd L. W. , Root G. N.
Published: February 2005

The time-sharing method of alternately pulsing an NMR transmitter and receiver has proven useful in reducing base-line instability due to leakage signal. In this paper, methods are described for increasing the repetition rates to 200 kc and higher, which displace the sidebands well away from the carrier, giving undistorted broad line absorption signals, and high resolution spectra without side band overlap (e.g., 19F spectra). Some undesirable features associated with field and frequency modulation are thus avoided. The method is accomplished quite simply using two pulsers, fast diode switches, and a broad band power amplifier.
Elastic Constants and Debye Temperature of TiC Using a New Ultrasonic Coherent Pulse/cw Technique
Authors: De Klerk J.
Published: February 2005

A new simple but sensitive ultrasonic velocity measurement technique, using a coherent pulse/cw system, is described. The technique can readily be used for velocity measurements in either small or large samples, and does not require elaborate instrumentation. This technique has been used to measure the velocities of all three pure acoustic modes along a (110) direction of a single crystal of TiC. These velocities were then used to calculate the elastic constants and the Debye temperature for this sample. The measured velocities are vL = 9.230×105 cm sec−1, vT1 = 6.425×105 cm sec−1, and vT2 = 5.927×105 cm sec−1. The calculated elastic constants are c11 = 3.891×1012 dyn cm−2, c12 = 0.433×1012 dyn cm−2, c44 = 2.032×1012 dyn cm−2, and the room temperature Debye temperature is 935°K.
Alternating Current Electromagnet Type Hysteresis Loop Tracer for Minerals and Rocks
Authors: Likhite S. D. , Radhakrishnamurty C. , Sahasrabudhe P. W.
Published: February 2005

A hysteresis loop tracer employing an alternating current electromagnet capable of providing fields up to 3600 Oe is described. Merits of the present system over other types of loop tracers are pointed out. Some typical hysteresis loops obtained using the apparatus are also presented.
Effect of Soller Slits on X-Ray Intensity in a Modern Diffractometer
Authors: Stoecker W. C. , Starbuck J. W.
Published: February 2005

The properties of Soller slits in a modern diffractometer are discussed in relation to the effect they have on the x-ray intensity distribution within the plane that contains the line focus and diffractometer axis. On the basis of an idealized Soller slit collimator, equations are derived for computing relative x-ray intensity in terms of the distance from the edge of the specimen. An independent mathematical derivation substantiates these equations and also shows the effect of varying the number of slits while keeping other properties of the collimator unchanged. When the equations are used to calculate the over-all intensity profiles of two diffractometers at the specimen position, the results are found to be in reasonable agreement with photographically determined profiles. Similar equations are used to explain the effect of the receiving Soller slits on the diffracted rays.
Liquid Helium Cryostat for Mössbauer Scattering Experiments
Authors: Barrett P. H. , Grodzins L.
Published: February 2005

A simply constructed cryostat designed for Mössbauer γ-ray scattering experiments is described. The sample volume is part of the transfer line from a liquid helium reservoir to a mechanical pump; the sample is thus cooled by helium flow. The helium vapor exiting from the sample volume cools the transfer line and radiation shield. The temperature of the sample is controlled by the helium flow rate determined by a needle valve at the pump. The operating range is from 9 to ∼300°K. The liquid helium consumption in liters/h is 0.3 at 10°K, 0.2 at 16°K, and 0.1 at 34°K. Possible modifications to improve the operating characteristics are discussed.
Design Variables for a High Pressure Cell with Supported Taper Pistons
Authors: Forsgren K. F. , Drickamer H. G.
Published: February 2005

A systematic investigation of the design variables for a high pressure cell with supported taper pistons has been undertaken. The variables studied include: the effect of center thickness, the effect of flat diameter and piston diameter, the pressure gradient across the flat, the pressure gradient on the taper, and the effect of different materials supporting the center. It is concluded that any scaling up in size from the dimensions used in the electrical resistance cell previously described in the literature (2.29 mm diam flat and 0.33 mm center thickness) results in a drastic reduction in pressure range. Scaling down the flat size results in a modest increase in pressure range. The pressure is remarkably independent of radius in the region of the flat which contains the electrical resistance sample. A piston with a double taper might suppy a greater degree of support for the piston tip.
Phototaxigraph: Recording Instrument for Determination of Rate of Response of Phototactic Microorganisms to Light of Controlled Intensity and Wavelength
Authors: Lindes DeArmond , Diehn Bodo , Tollin Gordon
Published: February 2005

An instrument has been developed which measures the rate of phototaxis in a suspension of microorganisms by recording the increase in optical density which results when the organisms accumulate in a beam of stimulating light. Intensity and spectral quality of the actinic light, as well as of randomly scattered background illumination, can be controlled. Density changes are measured with a dual chopped beam arrangement using infrared light. Thermostatic control of the temperature of the sample is provided.
Electron Beam Evaporator for In Situ Electron Microscope Studies
Authors: Olsen K. H. , Hutchinson T. E.
Published: February 2005

A device for evaporating metals by electron beam bombardment within the electron microscope has been developed which operates without loss of image resolution or stability. This device is particularly applicable to dynamic studies of nucleation and growth of metallic films characterized by unusually high purity and/or high melting points. A hanging drop of molten material, formed by bombardment of the end of a vertical wire by a focused beam of 2–5 kV electrons, provides a controllable source of pure metal vapor.
Measurement of Capillary Blood Flow Using an Electronic Double Flash Light Source
Authors: Gallagher Philip N. , MacRoberts Vernon E. , Edgerton Harold E. , Wells Roe E. , Rees Searle B.
Published: February 2005

An electronic double flash unit has been constructed to measure photographically average linear velocity of blood flow in the bulbar conjunctival vessels of the human eye. Two exposures on the same photograph separated by a predetermined time delay (adjustable from 2 to 200 msec) permit computation of velocity from the displacement of red cells per delay time. The equipment is small and mobile, the procedure innocuous.
Basic Properties of Electron Multiplier Ion Detection and Pulse Counting Methods in Mass Spectrometry
Authors: Dietz Leonard A.
Published: February 2005

The critical role played by first stage gain in shaping the output pulse height distribution and detection efficiency of an electron multiplier used as an ion detector is studied theoretically and experimentally. In a well-focused electron multiplier it is found that anode pulse height distributions observed for different ion species agree well with distributions calculated by using compound Poisson statistics. Models are developed to explain measurement bias in an electron multiplier which is used in either the dc or pulse counting modes and it is shown how these results can be applied to isotope ratio measurements. Design and operating characteristics are described for a 20 stage electron multiplier which was developed for high speed pulse counting and high detection efficiency. The surface of the first dynode is coated with a thin film of Al2O3 to provide a stable first stage yield of 7–9 secondary electrons/incident ion for monatomic alkali ions with 20 kV impact energy. The polyatomic ion Na2BO2+ yields about 16 secondary electrons/incident ion at 20 kV impact energy. Resolving time of the entire detector system is reduced to 10 nsec by using a specially designed solid state discriminator and pulse shaper. Also, a technique is described for the simultaneous detection and pulse counting of two ion beams.
Hydrofluorination Unit for Purification of Fluoride Laser Materials
Authors: Warshaw Stanley I. , Jackson Robert E.
Published: February 2005

An apparatus for the fluorination of hydroxyl- and oxygen-contaminated fluoride compounds is described. This purification process yields oxide-free fluorides. Optically clear lanthanum trifluoride single crystals were grown from material subjected to this treatment.
High Field Air-Cored Betatron Used to Investigate Intense Runaway Electron Streams
Authors: Skarsgard H. M. , Gore J. V.
Published: February 2005

An air-cored betatron has been constructed whose coil is effectively a single turn made up from four circular turns connected in parallel. The design was facilitated by choosing independently the positions of the four parallel turns and the current distribution through them. The desired current distribution was obtained by making two of the turns in the form of toroidal coils whose inductance could be adjusted. The betatron has been used in combination with an azimuthal magnetic field for the production of an intense stream of runaway electrons, consisting of essentially all the electrons of a plasma. After a short interval (∼0.1 μsec) of normal acceleration, the electrons experience less-than-normal acceleration followed by deceleration and disruption of the stream. Intense bursts of microwave radiation occur during the current pulse. The observed stream behavior is reasonably well explained by the theory of the two stream instability.
Elutriation Particle Separator
Authors: Scholz J. T. , Uhlmann D. R. , Chalmers B.
Published: February 2005

An elutriation particle separator is described which provides an inexpensive, efficient, and accurate method of obtaining from an original mixed sample sizable fractions of particles with diameters within preselected size ranges. Preliminary results for three size ranges between 10 and 100 μ are presented, together with proposed modifications (including a connected series of separators) for more efficient operation.
Time Resolution of Photoluminescent Spectra by Phase Controlled Chopping
Authors: Thomas D. E. , Colbow Konrad
Published: February 2005

In the study of photoluminescence, simple spectra obtained by dc excitation often do not contain sufficient information for complete analysis of the kinetics of the luminescent light emission. This paper describes a system with which the spectral emission can be studied at controlled times after photoexcitation. The system uses separate mechanical chopping of the photoexcitation source and the photoluminescent emission. The two light choppers are hysteresis synchronously driven from a single alternating current source and their relative positions are, therefore, phase locked. Their relative positions and, therefore, the time between termination of photoexcitation and detection of photoluminescent emission is controlled by a 0–360° precision electrical phase shifter placed between the common alternating current source and the power amplifier driving one of the chopper motors. This time controlled system is described. The photoluminescence is wavelength resolved by a spectrometer, detected by a photomultiplier and lock-in amplifier, and automatically recorded as a function of wavelength by an X-Y recorder. X-Y recorded tracings of photoluminescent spectra at various times after termination of photoexcitation are shown to illustrate the capabilities of the system.
General Purpose Analog Pulse Height Computer
Authors: Strauss M. G. , Brenner R.
Published: February 2005

Experimental techniques in nuclear physics often call for arithmetic operations on pulses whose amplitudes convey the experimental data. An instrument capable of pulse height multiplication, division, exponentiation, as well as pulse height addition and subtraction is described. These operations are performed in about 0.5 μsec with a precision of ±0.1% of full scale over a pulse height range of 20:1. At room temperature the computer exhibits a drift of about 0.05%/C° or ±0.3%/day. With an input rate of 10 000 counts/sec the pulse height distribution shifts 0.2%, and with 25 000 counts/sec it shifts 1%. Multiplication, division, and exponentiation are performed by using logarithms and antilogarithms. The log and antilog function generators are based on the fact that the emitter-base voltage of a silicon planar transistor is proportional to the logarithm of its collector current. Addition and subtraction are performed by using linear operational amplifiers. Results of experiments are shown in which the computer was used for identification of charged particles, pulse shape discrimination, measurement of mass yield distributions in fission, as well as for other on-line data reduction techniques.
Large-Format Spark Chamber Camera with Ten-Millisecond Deadtime
Authors: Williams Robert W. , Sander Oscar R. , Guldenmann Heinz
Published: February 2005

A camera is described which will take six photographs with stationary images and good optics in a total time of 40 msec. It is designed to record spark chamber events in experiments at pulsed accelerators in which the trigger rate during the pulse is high. Independently movable plane mirrors are positioned between the lens and the six separate films. After a photograph is recorded on one film the associated mirror is removed, allowing the image to fall on the next film. The films are advanced during the accelerator offtime. The frame size is 29×41 mm. Tests show a slight loss of resolution due to the presence of a mirror. The resolution was the same in pictures taken 10 msec apart as in static test pictures.
Stable Pirani Gauge for Precision Pressure Measurements
Authors: Hughes E. J. , McQuillan A. D.
Published: February 2005

A modified form of the Pirani gauge has been constructed in which a potential difference between two extra electrodes attached directly to the heated filament is measured rather than the change of resistivity of the whole filament assembly. In this way changes in the long term stability, which are a common feature of most Pirani gauges, can be avoided. The modified instrument may be relied on to maintain its stability after calibration for very long periods, and hence it can be used as a precision gauge for the accurate measurements of pressures in the range 1 to 10−3 mm Hg.
Magnetically Shielded Solenoid with Field of High Homogeneity
Authors: Hanson Roger J. , Pipkin Francis M.
Published: February 2005

The theory, design, and construction of a magnetically shielded solenoid are described. Three correction coils are employed in addition to the main solenoid winding. The solenoid is enclosed in three concentric magnetic shields which serve to screen the inner region of the solenoid from external magnetic fields. First the theory and design of a solenoid with correction coils and no magnetic shielding are discussed. Then calculations of the magnetic field due to a solenoid inside a closed cylinder of infinite permeability are summarized. These calculations show that a properly constructed shield can improve the homogeneity of the field due to a single solenoid by an order of magnitude. Optical pumping measurements of the field homogeneity in the central region and of the field distribution along the axis of the solenoid are reported. The measurements of the field distribution agree with the calculations to within a few hundredths of a percent. The shields reduce the disturbance due to changing external fields by a factor of 100. The main solenoid is 91.44-cm long and has an inner diameter of 32.41 cm. The solenoid field is 18.6 G/A and the solenoid dissipates approximately 320 W when producing a field of 60 G. The solenoid-shield system has at 60 G a homogeneity of 1 part in 105 over an 8-cm-diam sphere at the center of the solenoid. Construction details of the shields and coils are given and the solenoid power supply is described.
Elimination of the Compton Component in Amorphous Scattering
Authors: Warren B. E. , Mavel G.
Published: February 2005

Experimental elimination of the Compton component in amorphous scattering has been obtained by using crystal monochromated Rh Kα radiation (λ=0.615 Å). The scattered radiation from the sample falls upon a sheet of Mo (λK edge=0.620 Å). The fluorescence radiation, which is received in a Kr filled counter placed near the Mo, is closely a measure of the unmodified scattering since most of the modified scattering cannot excite fluorescence. The counter reading is high enough for direct chart recording.
Method for Pressure-Casting Refractory Alloys
Authors: Ryan J. J. , Peters E. T.
Published: February 2005

A modification to standard arc-melting equipment is described which allows arc-melted alloys to be chill-cast by a pressure differential technique into uniform grain-size, homogeneous ingots 6.3 mm in diameter by 5 to 6.3 cm in length. Pressure-cast refractory alloys with melting points up to 1700°C have been obtained using a 30-V dc welding generator operating at 175 A.
Properties of Wide-Gap Spark Chambers
Authors: Garron J. P. , Grossman D. , Strauch K.
Published: February 2005

The operation of spark chambers with gaps of up to 40 cm has been studied. By applying electric fields of the order of 10 kV/cm particle spark tracks suitable for accurate curvature measurements have been obtained. The uniformity of the electric field represents a very important factor in determining the limit of accuracy of curvature measurements. By comparing two 40-cm chambers located in a magnetic field against each other, it is found that the momentum of a 1-BeV/c cosmic ray can be measured to an accuracy of ±1.4% with one 40-cm chamber located in a 13.3-kG magnetic field. Sensitive times of 5 μsec are typical.
Efficient Low Pressure Sputtering in a Large Inverted Magnetron Suitable for Film Synthesis
Authors: Gill W. D. , Kay Eric
Published: February 2005

Electrical and sputtering characteristics of a 10-cm-diam inverted magnetron configuration have been investigated in the transition region from positive to negative space-charge modes. Radial voltage and ion energy distributions were obtained for both modes. The positive space-charge mode resulted in the most efficient transport of sputtered material from cathode to anode. Dependence of space-charge sign reversal on apparatus dimensions and magnetic field strength are discussed showing that operation in the 10−5 Torr range can be expected for a 40-cm-diam configuration. The deposition profile at the anode was in good agreement with the calculated profile showing that ion current and hence sputtering is uniform over the effective cathode area.
Tagging System for High Energy Photons
Authors: Caldwell David O. , Dowd John P. , Heinloth Klaus , Rousseau Michael D.
Published: February 2005

An apparatus has been built to determine the energy of each photon in a bremsstrahlung spectrum which produces an interaction of interest in a hydrogen target. The technique was applied specifically to charged pion photoproduction with photons of 2 to 5 BeV. The tagging system utilized a monoenergetic (to ± 1%) positron beam which produced photons and associated recoil positrons in a thin radiator. The recoil positrons were momentum analyzed and detected by a 19-counter hodoscope. The difference between the energies of an incident and a recoil positron is the photon energy, and this was determined to ±2.5%. Since the photon beam is relatively weak, the interactions it produces must be detected with good efficiency. Such a large-solid-angle spark chamber, magnet, and counter system, which was used to measure the photoproduced pions, is also described.