bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Study of Slit Scattering
Authors: Burge Edward J. , Smith David A.
Published: February 2005

An expression is derived for the flux of multiply scattered charged particles emerging from a square-edge collimating slit for a parallel beam at normal incidence. Full allowance is made for the continuous energy loss in the slit material, and the results are compared with those from Courant's theory. The effective increase in aperture is calculated for 50-MeV protons on elements throughout the periodic table and the optimum materials for collimators are discussed. A computation of the origin on the collimator face of the slitscattered flux from 50-MeV protons on copper shows that over 90% originate in the first 0.025 cm from the edge, when all energies are detected, and in less than 0.01 cm for energies above 37.5 MeV. The energy distribution is calculated as a function of the angular range accepted. The projected angle distribution, integrated over all energies, is found to have a maximum at about 1.5° for carbon, 4° for copper, and 7° for lead, with 50-MeV incident protons. The higher energy slit-scattered protons are shown to peak at smaller angles. Approximations in the theory are discussed and the results compared with those from Monte Carlo calculations by Becker and from the work of Överås.
Circuit for the Rapid Determination of Langmuir Probe Data
Authors: Crawford F. W. , Harp R. S.
Published: February 2005

The frequent use of Langmuir probes in the determination of electron temperatures and number densities in plasmas makes it desirable to have rapid methods of data reduction. This paper describes a simple and accurate instrument for carrying this out without the necessity of using logarithmic amplifiers or oscilloscope displays. Apart from its advantages in ease of construction, its calibration is particularly simple and drift-free. In operation, the device samples the probe characteristic at two values of current, and yields a numerical value for the electron temperature on a meter. Linearity of the characteristic is examined by varying the sampling currents. Provisions are made for ion current to be compensated and measured, and for the electron saturation current to be estimated.
Self-Sampling System for Measurement of Picosecond Pulse Characteristics
Authors: Agouridis Dimitrios C.
Published: February 2005

The self-sampling system utilizes the sampling of a pulse by itself for measurements of the pulse characteristics. The system can be used to measure characteristics of pulses rising in substantially less than one nanosecond. The pulse being measured is initially split into two pulses by a power divider. Then the two pulses so formed are delayed unequally as they propagate in separate transmission lines. Finally the pulses are brought together in the coincidence circuit which consists of a power divider and a wide-band crystal detector. The operation of the system is based on the square law characteristics of the crystal detector. From the variation of the output of the coincidence circuit with variation in the delay difference, information can be obtained about the pulse amplitude, the pulse width, and the sum of the pulse rise and fall times. This system has been used to measure the characteristics of subnanosecond rise and fall time pulses generated by a mercury switch pulse generator.
Negative Feedback Electrometer Circuit
Authors: Spangler Robert A.
Published: February 2005

An electrometer circuit, utilizing a commercially available differential operational amplifier, is described and its basis of operation briefly analyzed. By virtue of the negative feedback configuration employed, interelectrode potential relationships in the electrometer tube are maintained virtually constant, thus providing highly stable performance, linear gain characteristics, and a high effective input impedance. Provision for compensation of nonideal amplifier characteristics and input capacitance neutralization is included.
A 4π Positron Scintillation Spectrometer
Authors: Rhode J. I. , Johnson O. E.
Published: February 2005

A 4π scintillation-spectrometer system applicable to the measurement of positron spectra is described. It is comprised of a 4π beta-ray detector (two plastic scintillators), three gamma-ray detectors (NaI crystals), and associated pulse-height analysis and coincidence circuitry. Source techniques, calibration procedures, and various pertinent experimental considerations essential to its operation are presented. An evaluation of the system is made on the basis of its performance in the measurement of both positron spectra (Zn65 and Na22) and negatron spectra (Pm147 and W185). The implications of the experimental results obtained from beta spectra concerning a possible nonlinearity at low energies (<50 keV) in the scintillation response of the plastic phosphor to electrons are discussed.
Phase Fluorometer to Measure Radiative Lifetimes of 10−5 to 10−9 Sec
Authors: Brewer Leo , James C. Geoffrey , Brewer Richard G. , Stafford Fred E. , Berg Robert A. , Rosenblatt Gerd M.
Published: February 2005

Apparatus to measure radiative lifetimes by the phase-shift method is described. A rotating-wheel, reflection grating modulates light at 60 kc for the measurement of lifetimes of 10−5 to 10−7 sec. An ultrasonic grating is used for modulation at 5.2 Mc to study lifetimes of 10−7 to 10−9 sec. Optical and electronic sources of systematic error have been investigated. Procedures have been developed to minimize systematic errors in the lifetime measurements. Measurements on solid BaPt(CN)4·4H2O are reported. Iodine vapor and solutions of organic molecules also have been studied.
Semiconductor and Gas-Ion-Chamber Detector System for the Mass Identification of 10- to 30-Mev Particles
Authors: Wegner H. E.
Published: February 2005

A charged-particle detector system, which consists of a gas-ion-chamber ΔE counter and a semiconductor E counter, is described. The detector system has been employed in the study of nuclear reactions leading to protons, deuterons, tritons, He3, and alpha particles in the 10- to 30 Mev region, with mass and charge identification for each kind of detected particle. Although many particles have sufficient energy to penetrate beyond the sensitive depletion region of the semiconductor detector, the electronic selection system discriminates effectively against such particles. Those particles ending their range in the depletion region may be studied under conditions of energy resolution and mass discrimination much improved over the usual NaI scintillation detector system. Preliminary results of measurements with a lithium-drifted p-i-n junction with a depletion region 2 mm thick are shown, and the advantages of using the thicker depletion region available with such devices with the same electronic system are demonstrated.
Center-of-Mass Corrections in Nuclear Reaction Experiments
Authors: Lorenzi Henry , Cohen Bernard L.
Published: February 2005

In nuclear reaction experiments with heavy target nuclei, corrections for center-of-mass motion may be simplified by various approximations. Several methods of applying these corrections with varying accuracy and ease of computation are discussed. One of these involves a short hand computation using tables given in the Appendix; another involves the use of curves which give very accurate results in a few seconds of hand calculation.
Panoramic Mass Spectrometer
Authors: Marsden D. G. H.
Published: February 2005

A panoramic rapid scanning sector mass spectrometer is described. A mass range of ten to one may be scanned in times ranging from 10 msec to 300 μsec; the peaks are displayed on the screen of an oscilloscope. Alternatively, single peak height variations may be displayed down to times of 10 μsec. The instrument is designed for following gas reactions at pressures up to 200 mm and temperatures up to 450°C. Some comparison is made with fast-scanning time-of-flight instruments.
Problems Arising in the Measurement of Small Magnetic Forces at Low Temperatures by the Faraday Method
Authors: Gerritsen A. N. , Damon D. H.
Published: February 2005

In the course of an investigation of the magnetic susceptibility of germanium at temperatures below 4.2°K, it has been found that the behavior of the exchange gas may strongly affect the accuracy of the measurements. Both the force measurements and the temperature of the sample are affected. If the dimensions of the suspension and the exchange gas pressure are chosen properly, then for a sample that is adequately shielded from thermal radiation this interference can be reduced to a tolerable amount.
Automatically Controlled Isothermal-Adiabatic Calorimeter
Authors: Hiller L. A. , Brink I. J.
Published: February 2005

A calorimeter has been constructed to measure specific heats, heats of solution, heats of reaction, and other thermal changes in liquid systems. For endothermic processes the calorimeter jacket is maintained at constant temperature while heat is supplied to the reaction chamber at a rate sufficient to keep the temperature of chamber and jacket equal. During exothermic processes, including specific heat determinations, the jacket temperature is raised at a rate sufficient to maintain temperature equality between chamber and jacket. The recording and controlling of temperature in the calorimeter are continuous and largely automatic. The heat input to the calorimeter is also automatically recorded by means of an integrating watt-second meter. Experimental specific heat data are presented to illustrate the performance of the calorimeter. The results of specific heat measurements on toluene and water agree with previously reported values within 1% over a temperature range from approximately 20–40°C. The temperature difference between jacket and reaction chamber during these experiments was automatically controlled within 0.05°C and no oscillation of the control was apparent.
Water Cooled Magnets
Authors: Bitter F.
Published: February 2005

This paper discusses the construction of water cooled solenoids at power levels ranging from 1 to 100 Mw and with cylindrical inner working spaces having radii ranging from 1 to 10 cm. A first limitation is due to the fact that the power density in the magnet cannot exceed a value set by the surface cooling rate allowable in the water passages. Present designs go up to a power density of 1.5×104 w/cm3 and a surface cooling rate of 1.5×103 w/cm2. With these limitations, useful coils can be built operating at power levels ranging from 1 to 10 Mw and giving fields ranging from 100 to 250 kilogauss. In the range of 200 to 300 kilogauss, Zr-Cu or Cr-Cu alloys may be used to avoid plastic deformation at the inner surface. The strengthening and cooling of coils to operate at higher power levels is discussed. A preliminary design is presented for a high precision magnet for nuclear magnetic resonance experiments.
Simple Recording Spring Balance
Authors: Fujii C. T. , Carpenter C. D. , Meussner R. A.
Published: February 2005

A simple recording balance has been designed for use in high temperature oxidation studies. A helical spring is the weighing mechanism; a light beam and silicon solar cell, the spring position detector. The signal from the solar cell is fed directly to a strip chart recorder without prior amplification. The construction allows for heating of the system which permits the use of the balance in condensable atmospheres. The specifications of the balance in use are: maximum load, 1.5 g; range, 200 mg; sensitivity, 0.5 mg.
Suspension Balance Employing a Large Permanent Magnet
Authors: Pankey Titus
Published: February 2005

A simple device consisting of an iron sphere constrained with fine copper wire and suspended in the field of a large permanent magnet is described. Weight changes of 2 parts in 106 are measurable. The device was employed to measure the forces exerted on a magnetized object by other substances according to their magnetic susceptibility.
Technique for the Zone Melting of Insulators
Authors: Neumann Leo , Huggins Robert A.
Published: February 2005

Apparatus is described which permits insulators to be zone melted by electron beam techniques. The primary feature is the use of secondary emission from the sample to prevent build-up of an electrostatic charge. In addition to remelting solid rods, this procedure can be applied to the melting and zone refining of sintered polycrystalline rods and tubes.
Some Geometrical Considerations for X-Ray Collimation in Single-Crystal Diffraction Work
Authors: Cole H. , Chambers F. W. , Wood C. G.
Published: February 2005

In positioning an x-ray tube in an experiment in order to gain optimum usable power, the variables at the operator's control are the take-off angle and the collimation (or slit) system. These variables should be fixed by consideration of sample size, focal-spot size, target ``absorption shadow,'' and the amount of divergence to be permitted. Consideration of these factors leads to an uncommon collimator for simple large single-crystal diffraction work.
Harmonic Analysis in Systems Using Phase Sensitive Detectors
Authors: Russell A. M. , Torchia D. A.
Published: February 2005

An analysis is made of a system utilizing modulation and synchronous detection. The signal after modulation is expressed both as a Taylor expansion and as a Fourier series. The evaluation of the coefficients and subsequent comparison show that the first derivative of the signal can be expressed as f′(x)=A−1[H1−3H3+5H5−7H7+…+(−1)n−1(2n−1)H2n−1+…),where A is the amplitude of the cosine modulation and H1, H3, etc., are the amplitudes of the odd harmonics of the modulated signal.
New Anisotropy Recorder for Ferromagnetic Thin Films
Authors: Collette René
Published: February 2005

A new instrument is presented for measurement of the anisotropy energy of thin ferromagnetic films. It permits rapid and simple investigation of the anisotropy over a 360° range. The method is purely electrical; the results are automatically displayed on the oscilloscope screen. The circular film is rotated uniformly in a homogeneous dc field. The magnetization vector oscillates around the direction of this field. Its movement is recorded, and relates directly to the anisotropy energy function. Three examples of results obtained are presented. The resolving power, expressed in terms of magnetic flux inside the sample, is determined by the ambient 60-cycle field; its value is of the order of 10−11 Wb, which corresponds to a thickness of approximately 10 Å for a 80% Ni Permalloy film one cm in diameter. The simplicity and the small cost of the instrument are attractive features. In many cases, both the present analysis and that obtained with a static torquemeter at high field would be complementary.
Resonant Depolarization of a Beam of Polarized Protons During Acceleration in a Synchrocyclotron
Authors: Lobkowicz F. , Thorndike E. H.
Published: February 2005

The loss of initial polarization of a proton beam during acceleration in a synchrocyclotron is investigated. It is shown that, due to resonance effects, substantial depolarization occurs unless the field inhomogeneities are kept well below 0.01%.
Single Cavity High Current Electron Accelerator
Authors: Venable Douglas
Published: February 2005

A single 50-Mc cavity electron accelerator has been built. When operating in the TM010 mode, it is capable of delivering a 29-amp, 0.2-μsec, 8-Mev, 2-cm radius beam to a target downstream from the cavity. When focused to a 3-mm-diam spot, the beam current is reduced to about 9 amp; the resulting radiation flux is about 1.2 r at one meter for a 0.2-μsec pulse length.
Simple rf Phase Detector for NMR Spectrometers
Authors: Flautt T. J.
Published: February 2005

A phase detector system which can be easily adapted to bridge or crossed-coil NMR spectrometers is described. Modifications to the NMR spectrometer include addition of a constant impedance attenuator for control of the probe excitation voltage, a leakage control system independent of probe balance, and a differential dc amplifier to cancel changes in the leakage from spurious modulation of the transmitter power.
Plasma Potential Probe Using Electron Time-of-Flight
Authors: Slattery J. C. , Kemp R. F.
Published: February 2005

A technique is described for measuring the potential within a plasma by monitoring the time-of-flight of a beam of electrons directed through the plasma. The electron beam, intensity modulated at 30 Mc, is accelerated to an initial velocity determined by its cathode potential. The velocity then varies from this initial value as the potential along the flight path varies, changing the arrival time of the 30-Mc signal at the collector. The phase of the collector signal is continuously compared to that of a reference signal derived from the intensity modulator. The phase comparator has an output which is linearly proportional to the phase difference between the two signals. The sensitivity of the technique depends principally on the energy of the electron beam and the response time of the circuits. Using 900-v electrons, it is possible to measure a potential of 2 v along a 10-cm path, or follow changes of this magnitude which occur in a microsecond. The sensitivity can be raised to look at potentials which change more slowly. Under the operating conditions used, 2 v along 10 cm represent a phase change of about 0.1°, or a time change of about 1×10−11 sec.
Use of Germanium as a Second Sound Receiver
Authors: Snyder H. A.
Published: February 2005

It is shown that doped germanium crystals can be used as second sound receivers. Their frequency response, sensitivity, and noise level have been measured for samples of several thicknesses. By comparing the results with the corresponding values found in other types of second sound receivers, it is concluded that germanium receivers are superior to the other types in common use for applications below 10 kc.
Glass Dewars for Optical and Other Studies at Low Temperatures
Authors: Schoen L. J. , Broida H. P.
Published: February 2005

A small, rugged glass Dewar using a liquid nitrogen cooled metal shield is described. This Dewar is relatively inexpensive to construct and to modify, stores helium with only a moderate loss rate, and can be adapted for a wide variety of low temperature experiments. Two other Dewars, in which vapor-cooled radiation shields replace liquid nitrogen cooled shields, also are described. Helium loss rates show that a liter of liquid helium will keep these Dewars at 4°K for about 5 to 10 hr.
Evaporation of Helium I Due to Current-Carrying Leads
Authors: Sobol Harold , McNichol James J.
Published: February 2005

The heat introduced into a cryogenic system by current-carrying leads has been investigated experimentally and theoretically. The experimental work consisted of measuring the heat conducted by various cables and wires into a helium Dewar. The experimental results show that the use of long coaxial cables to the helium bath minimizes boil-off and also that there are optimum wire sizes for the current ranges 0–0.5 amp (#38 AWG) and 0.5–1.0 amp (#34 AWG). The theoretical analysis of the heat input takes into account the varying electrical and thermal conductivities of the leads and also allows for heat exchange with the effluent helium vapor. The results of this analysis indicate the importance of including gas cooling in predicting the boil-off rate.
Measurement of Photomagnetic Susceptibility by Means of a Vibrating Reed Balance
Authors: Kessler J. O. , Moore A. R.
Published: February 2005

An apparatus employed for studying light-modulated changes in the magnetic susceptibility of semiconductors is described. Its chief parts are a flat reed spring from which the specimen is suspended, an electrostatic counter-balancing system, a frequency modulation phase sensitive motion detector, and a modulated light source. The light modulation operates at the mechanical frequency of reed and specimen, whose forced harmonic motion is proportional to the light-induced susceptibility changes. The chief advantages of this new method are the elimination of drifts due to changes in the nonmodulated part of the susceptibility, the excellent nonsynchronous noise elimination, and the high detection sensitivity, which was 10−11 cgs mass-susceptibility units at a value of H gradH of 107 gauss2/cm. Another incidental advantage is a simplicity and ruggedness not generally encountered in high sensitivity instruments.
Space-Charge Expansion of a Positive Hydrogen Ion Beam Leaving a Duoplasmatron Ion Source
Authors: Wittkower A. B. , Galejs A. , Rose P. H. , Bastide R. P.
Published: February 2005

Space-charge is shown to be the controlling influence in the expansion of a positive hydrogen ion beam leaving a duoplasmatron source aperture. This implies that there is an optimum source aperture radius for each application. In particular, when high currents are required, this aperture may be large—i.e., greater than 0.05 in. radius. The gas flow from the source into the vacuum system may then become excessive; an extraction system which allows the aperture radius to be increased without this attendant gas flow, is described.
Detection Efficiency of Plastic Scintillator for Neutron Energies 4 to 76 Mev
Authors: Wiegand Clyde E. , Elioff Tom , Johnson William B. , Auerbach Leonard B. , Lach Joseph , Ypsilantis Thomas
Published: February 2005

The neutron detection efficiency of plastic scintillator counters 15 cm thick has been determined for neutron energies from 4 to 76 Mev. Neutrons in this energy range were obtained by scattering a 205-Mev neutron beam from a hydrogen target. A proton-range telescope selected the forward-scattered protons from the n-p reaction, thus monitoring the flux of monoenergetic neutrons scattered in a prescribed direction. Near 10 Mev the efficiency is 30%, and it slowly decreases to 20% at 76 Mev.
Magnetometer Based on the Hall Effect
Authors: Viehmann Walter
Published: February 2005

This paper describes a magnetometer for the determination of the saturation magnetization of magnetic materials. Unlike conventional magnetometers, the instrument described does not require well-defined movements of the sample and pickup coil relative to each other because the dipole field of the magnetized sample is converted into a dc electrical signal by means of a sensitive Hall probe. The instrument is simple in design, easy to construct, and relatively inexpensive. Test samples are prepared by pressing the magnetic powder into a brass cartridge to a constant volume. This technique yields samples of uniform and reproducible dimensions. Calibration of the instrument is made with a nickel sample of known magnetization. Magnetic moments of 20 gauss cm3 have been measured with an accuracy of 1%.
Measurements on Gallium-Doped Germanium Thermometers
Authors: Blakemore J. S. , Schultz J. W. , Myers J. G.
Published: February 2005

Germanium doped with controlled amounts of gallium and compensated with antimony has a useful thermometric sensitivity in the liquid helium and hydrogen ranges. The effects of magnetic fields on resistance—and hence on thermometry—are reported over the 2–25°K interval. Preparation and encapsulation of germanium ``bridges'' is described, and the thermal properties of encapsulated assemblies measured, including the variation of resistance with input power, and the thermal response time (∼0.1 sec at 4°K). A simple method for checking the reproducibility of thermometers is described.
Drilling Coordinates for Crystal Structure Models
Authors: Peacor Donald R. , Prewitt C. T.
Published: February 2005

Calculation of the spherical drilling coordinates ρ and φ for crystal structure models often requires a prohibitive amount of time, especially for structures of low symmetry. The coordinates are readily calculated using a vector algebraic method which is applicable to any crystal system. This method is designed for computation with a digital computer.
Distortion of Proportional Counter Spectra by Counter Poisons
Authors: Smith C. F. , Conway D. C.
Published: February 2005

Distorted spectra were obtained when the Mn K x-ray peak was observed in a proportional counter filled with CO2 and small pressures of the counter poison O2. The spectra can be explained with the assumption that the only effect of the poison is to capture electrons as they drift toward the anode. The rate of attachment of electrons at an average electron energy of 0.054 eV and 298°K was found to be equal to K2(O2)+K3(O2)(CO2), where the values of K2 and K3 are 5×10−12 cc/sec and 1.7×10−30 cc2/sec, respectively.
Use of Traveling Wave Helices in ESR and Double Resonance Spectrometers
Authors: Webb Robert H.
Published: February 2005

Use of a traveling wave helix for concentrating microwave fields is discussed, with special attention given to application to electron spin resonance and Overhauser effects (double magnetic resonance). Some practical design considerations are treated. The influence of the standing wave pattern in the helix is treated in the Appendix.
Total-Absorption Scintillation Counter for High-Energy Photons
Authors: Bowman William C. , Carroll Jim B. , Poirier John A.
Published: February 2005

A total absorption scintillation counter for high-energy photons has been developed with ±7% energy spread for 130-MeV photons. The counter was built of enough plastic scintillator to contain most of the energy and maintain a high detection efficiency. We employed the technique of observing a statistical sampling of light from an integrating volume. The integrating volume was obtained by painting the surface of the counter with a diffuse reflector and detecting the light with a large number of photomultiplier tubes placed symmetrically about the counter. Use of a scintillator enabled us to work with a light source of high intensity, thus assuring optimum photon statistics.
Magnetic Suspension Balance Method for Determining Densities and Partial Specific Volumes
Authors: Beams J. W. , Clarke Alexander M.
Published: February 2005

Two modifications of the magnetic suspension balance are described for determining densities and partial specific volumes. Both modifications are capable of high precision. Also, they require comparatively small amounts of the materials and short times for the determinations.
Vibrating Vane, Absolute Gas Pressure Gauge
Authors: Neher H. V.
Published: February 2005

An oscillating rectangular vane suspended by a fine quartz fiber is used to determine the absolute pressure of the gas in which it is located. Aside from being an absolute instrument, the advantages of such a device are (1) simplicity, (2) the fact that it does not change the pressure when an observation is made as do many other types of gauges, and (3) the absence of a heated filament which may decompose the gas under study.
Triggered Film Advance System
Authors: Lande Kenneth , Mann Alfred K. , White D. Hywel
Published: February 2005

A system is described which provides a triggering signal for a scintillation or spark chamber from a coincidence circuit. Power is supplied to label the recording film with a register number and to advance the film to a clear position. Multiple exposures of events are prevented.
Pulsed Voltage Multiplier
Authors: Mobley R. C.
Published: February 2005

A suggested multistage high voltage multiplier design utilizing a low duty cycle 10-kc pulse drive has been built, tested, and found reliably operable at twice the dc voltage gain per rectifier stage of conventional sine wave drive Cockcroft-Walton multipliers. Low capacitance rf tuned circuits across the ends of similarly tuned filament and anode lines permit simultaneous independent utilization of these lines for conveying pulse drive and rf filament heating current. A novel rf compensating and pulse canceling arrangement substantially eliminates output voltage ripple. The ten-stage prototype tested utilizes miniature commercial 1AX2 vacuum rectifiers and 20-kV T.V. doorknob condensers and has been successfully operated at output voltages in excess of 250 kV and at output currents exceeding 500 μA. Output impedance was 60 MΩ. Voltage gains in excess of 200 kV/ft appear feasible.
Apparatus for Continuous Recording of Internal Friction
Authors: Kofstad P. , Butera R. A. , Craig R. S.
Published: February 2005

An internal friction apparatus based upon the principle of the torsion pendulum is described. Attached to the inertia member of the pendulum are two coaxial coils which are located in the field of a permanent magnet. Oscillations of the pendulum induce an emf in one coil (the pick-up coil). The signal is amplified and converted into a square wave of constant amplitude which is used to energize the other coil (the driver coil). Interaction between the driver coil and the magnetic field maintains the system in oscillation, the amplitude being proportional to Q. The output of the pickup coil is measured on a strip chart recorder. After a straightforward calibration procedure, the Q of the system is quantitatively related to the output. The device has been used from 4°K to 150°C.
New Wavemeter for Millimeter Wavelengths
Authors: Zimmerer Robert W.
Published: February 2005

A new wavemeter of simple design is described. The principle of operation makes use of a new development in physical optics. The actual performance of the device was measured and compared with the theory.
New Detector for the Vacuum Ultraviolet
Authors: Lincke R. , Wilkerson T. D.
Published: February 2005

A new method is described for detecting vacuum uv radiation. This radiation is converted to visible light in two steps, the first being creation of photoelectrons at a high voltage cathode, the second consisting of stopping these electrons in a scintillator at ground potential. The visible scintillations are detected with a standard photomultiplier. The system has been compared with a sodium salicylate detector, using a vacuum uv monochromator and a steady light source. Spectral lines between 500 and 1300 Å have readily been recorded. Compared to other systems, the new detector offers a number of advantages which are discussed. Preliminary results for pulsed light sources indicate that the method is also useful for studying phenomena whose time scales are of the order of 1 μsec.
Ignitron-Switched 0.6- to 90-kV Impulse Generator
Authors: Beckner Everet H. , Kotoski Ralph H.
Published: February 2005

An ignitron-switched impulse generator has been developed, capable of providing a variable output voltage of from 0.6 to 90 kV with no circuit alterations. The generator consists of 6 capacitor stages, yielding a total energy of 5000 J at 90 kV, and is discharged with a single trigger pulse. The discharge time can be controlled to within 0.1 μsec.
Magnetic Lens System of Unit Magnification for High Energy Charged Particles
Authors: Marshall L.
Published: February 2005

A magnetic lens system designed from studies made with computing machines has been built and used at the Brookhaven cosmotron. It collected pions of 1020 MeV/c mean momentum produced at a target in the external proton beam, selected a narrow momentum bandwidth from a continuous momentum spectrum, recombined the selected momenta, and refocused the pions to an image of unit magnification. The effective solid angle of acceptance was 5.04×10−3 sr and the momentum band pass width was ±30 MeV/c. The measured particle yield on 1 in.2 at the focus was 5×105 for 6×1010 internal 3BeV/c protons; 27% were positive pions and 73% were protons.
Construction of a Gaseous Optical Maser Using Brewster Angle Windows
Authors: Brangaccio D. J.
Published: February 2005

A description is given of the materials, tools, and techniques used to make a successful gaseous optical maser whose output windows are oriented at the Brewster angle in respect to the beam axis.
Apparatus for the Measurement of Thermal Conductivity in the Range 1.7 to 300°K
Authors: Holland M. G. , Rubin L. G.
Published: February 2005

An apparatus for the measurement of thermal conductivity in the range 1.7 to 300°K is described. Precautions on the use of gold-cobalt thermocouples as well as details on automatic operation of the equipment are included. A qualitative analysis of the transient behavior indicates a method for detecting errors in the measured thermal conductivity values.
Gimbal Goniometer
Authors: Cole H. , Okrasinski M.
Published: February 2005

A goniometer for single-crystal diffraction work, based on the use of a gimbal system, is described. The gimbal is driven by the rolling of a spherical section in frictional contact with a movable plane. The special features of the device are discussed.
Electron Showers in a Lead Plate Spark Chamber
Authors: Cronin James W. , Engels Eugene , Pyka Manfred , Roth Richard
Published: February 2005

A spark chamber, containing 40 Pb plates of one-third radiation length each, has been exposed to electron beams of energy 85 to 750 MeV. The total number of sparks in the showers and their distribution is measured. For electron energies up to 200 MeV the results agree well with Wilson's Monte Carlo calculations. Above 200 MeV poor multiple track efficiency destroys the agreement. It is concluded that such a spark chamber is a good detector for electrons, and with further development could serve as a spectrometer.
Kelvin Device to Scan Large Areas for Variations in Contact Potential
Authors: Parker James H. , Warren Roger W.
Published: February 2005

Many devices depend for their operation upon the establishment of known, uniform electric fields. Unknown contact potentials between the parts of the device often impair its performance. An apparatus has been constructed to measure the magnitude as well as the variation of such contact potentials with an accuracy of ±1 mV under conditions typical of bakeable high vacuum systems.
Bridge for Tracing the Tunnel Diode I–V and Conductance Curves
Authors: Wilfinger R. J. , Zolotar B. A.
Published: February 2005

A bridge circuit is described in this paper which permits tracing of both the I–V and conductance curves of tunnel diodes. To insure accuracy, a constant voltage ac source employing feedback is used for the derivative measurement. Equipment used is relatively simple and the majority of it is commercially available. The circuit also allows fixed point measurements to be made at the user's option. Reproducibility and accuracy are mainly dependent on output indicator and the parameter being measured. Equations for small errors introduced by the bridge are presented (Appendix); they can be used to determine when a measurement is subject to excessive error. Measurements at other than room temperatures may be made with the bridge by physically isolating the high frequency circuitry containing the diode from the remainder of the bridge. Representative data from the bridge are presented.
Effect of Photocathode-to-First Dynode Voltage on Photomultiplier Noise Pulses
Authors: Pagano R. , Damerell C. J. S. , Cherry R. D.
Published: February 2005

Attention is drawn to a simple method of improving the signal-to-noise performance ratio of photomultiplier tubes used in scintillation counting. Representative results are presented and the underlying physical principles are discussed briefly.
Contribution to the Realization of the Visual Optical Pyrometer Temperature Scale
Authors: Thorn R. J. , Winslow G. H.
Published: February 2005

An examination of the results of a recent international exchange of tungsten strip lamps reveals that an addition can be made to its analysis. An application of the analysis of variance to the reported data demonstrates, with high probability, the existence of differences between laboratories. It also demonstrates, with the same high probability, the existence of a scale change error in some laboratories, but not in others, at the place where one changes from the H range to the XH range on a Leeds and Northrup pyrometer. Since both sorts of differences are, thus, demonstrably greater than the precision that is available in any one laboratory, the sources of them can, presumably, be found. Procedures for doing so are suggested.
Detection of 10- to 100-keV Ions by Nuclear Track Plates
Authors: Davis W. D.
Published: February 2005

The efficiency of 10- to 100-keV ions of He, Ne, and Ar in producing developed grains in nuclear track plates was determined by counting the individual grains. This efficiency is compared with the estimated range of the ions in the emulsion.
High Speed Infrared Bolometer
Authors: Camac Morton , Feinberg Robert M.
Published: February 2005

A new type of heat transfer gauge that operates in the presence of highly ionized plasmas and in strong electric and magnetic fields has been developed. The principle of its operation is to use a thin opaque surface as the heat transfer element. Aerodynamic and radiative heating is applied to one side of this layer, while measurements are made of the change of the infrared emission from the other side. This system is essentially a bolometer. Since the gauge is initially at room temperature, the predominant radiation from the opaque layer is in the infrared band from 5 to 30 μ. Changes in the temperature of the element are determined by the variation in its infrared emission. The opaque layer is made thin enough so that the temperature of the front surface can be determined in less than 0.1 μsec. This paper describes the components of the heat transfer system and the methods for calibrating the gauge for heating pulses of long and short duration. Gauge calibrations by heat pulses from shock heated air are presented, and the response time of the gauge to short heat pulses is evaluated.
Multiple-Heater Turret for Vapor Deposition
Authors: Simmons John G. , Moister Douglas E.
Published: February 2005

A rotary multiple-filament turret is described which permits sequential vapor deposition of several materials from the same position within a vacuum chamber, thereby eliminating angle-of-incidence problems at the receiving surface of the substrate. No dynamic feed-throughs are used in the system, and only one high-current feed-through is used, thus minimizing high-vacuum leaks.
Rapid Method for Measuring Seebeck Coefficient as ΔT Approaches Zero
Authors: Ivory J. E.
Published: February 2005

A rapid method for obtaining the Seebeck coefficient is described. A Seebeck voltage obtained across a sample with respect to one material of a thermocouple is plotted against that obtained across the sample with respect to the second thermocouple material on an X-Y recorder as the temperature gradient across the sample is slowly varied. The slope of this curve, which is not dependent upon accurately matched thermocouples, yields the Seebeck coefficient of the sample. This slope can be measured at a point corresponding to zero ΔT.
High Speed Semiconductor Photodiodes
Authors: Riesz R. P.
Published: February 2005

The theory and practical behavior of P+−π−N+ semiconductor photodiodes are given. It is shown that under operating conditions response may be anticipated for light modulated at frequencies in excess of 1010 cps. The signal-to-noise ratio of such a diode is discussed both for simple detection of amplitude-modulated light and for the case of optical heterodyne detection. In the latter case a favorable comparison is found with a photomultiplier tube detector. A description of the structure and fabrication of a germanium device is given, and results are presented which exhibit the long wavelength response, high quantum efficiency, and high frequency sensitivity expected. Measurements indicate no reduction in response at frequencies as high as 2000 Mc.
Device for Jerking Dendrite Interfaces Rapidly from the Melt
Authors: Bennett A. I. , Fekete J. M. , Hamilton D. R. , O'Hara S.
Published: February 2005

An electromechanical device is described which will abruptly remove growing crystals from melts in order to preserve interfacial detail. High initial acceleration, of the order of a thousand gravities, is provided by an impact mechanism. This acceleration, the subsequent travel, and the damping are adjustable, and the entire sequence is triggered electrically. Dendritic samples of germanium indicate preservation of interfacial detail on a scale of a few microns.
Fabricating Liquid-Hydrogen Targets from Mylar
Authors: Mehr David L. , McLaughlin Edwin F.
Published: February 2005

A method of constructing laminated Mylar containers for cryogenic-liquid targets is described.
Preparation of Evaporated Silicon Films
Authors: Kilgore Ben F. , Roberts Richard W.
Published: February 2005

A simple method for preparing evaporated thin films of silicon from an etched silicon filament is described. The method of mounting and processing the filament ensures low gas evolution during evaporation and makes possible the deposition of silicon films in a vacuum of ∼5×10−10 Torr.
Optical Cell for Pressurized Solids and Liquids at Cryogenic Temperatures
Authors: Smith B. L.
Published: February 2005

An apparatus designed to measure the refractive indices of the inert gases over the temperature range 77 to 273°K and at pressures up to 100 atm is described. Techniques are given for calibration of the optical cell and the production of a suitable solid specimen. The accuracy of the method is discussed and it is shown how polarizability and compressibility may be deduced from the refractive index data.
Device for NMR Measurements Under Axial Stress and Hydrostatic Pressure
Authors: Veigele Wm. J. , Bevan A. W.
Published: February 2005

A device for making NMR measurements in a double-coil nuclear induction system under axial stress on single crystals in excess of 10 000 psi or hydrostatic pressure on powders, single crystals, or other materials up to 10 000 psi has been constructed of Fiberglas. This device is simple in design and operation and is relatively inexpensive. Results of measurements on I127 in NaI powder, which exhibit the expected decrease in intensity with pressure, are given.
Crystal Sphere Orienter
Authors: Papike J. J. , Bright R. C. , Zoltai T.
Published: February 2005

A crystal sphere orienter for nonopaque crystals has been designed. It is used in conjunction with a petrographic microscope to orient crystal spheres optically.
Instrument for the Continuous Measurement of the Density of Flowing Fluids
Authors: Miller C. E. , Jacobs R. B. , Macinko J.
Published: February 2005

This paper describes the development of a new electromechanical method of measuring the densities of flowing cryogenic fluids. The instrument uses a movable section of flow passage, vibrated transversely at a constant amplitude and frequency, as the sensing element. A dynamometer, inserted between the flow passage and driver, continuously measures the acceleration reaction (product of mass and acceleration) of the fluid in the passage. A measure of this reaction is also a measure of the fluid density in the passage. Performance results indicate that the densitometer should be well suited for service in liquid oxygen and nitrogen single- and two-phase flow systems, and with only minor changes for use with liquid hydrogen.
Suppression of Total Reflection of Neutrons from Collimator Surfaces
Authors: Jones Ian R. , Bartolini William
Published: February 2005

Well-defined beams of thermal and long-wavelength neutrons are often difficult to obtain because of reflection from collimator surfaces. Reflection is minimized if the product of the number of scatter centers per cm3 and their net coherent scattering amplitude is as small a negative number as possible. This amplitude balancing can be achieved to almost any degree by the proper selection of organic compounds. When used as surface coatings, these compounds possess distinct advantages over other materials. Tetradecanoic acid (C14H28O2) has shown extremely low reflectivity and excellent properties as a surface coating.
Spark Chamber Performance in High Intensity Pulsed Magnetic Fields
Authors: Platner Edward D. , Orr J. R.
Published: February 2005

Performance of a 9-plate ⅛-in. gap stainless steel foil spark chamber was tested in close proximity to a 200-kG pulsed magnetic field. No detrimental effect on efficiency was observed for axial field intensity variation of from 20–100 kG.
High Intensity Electrodeless Sources for Raman Spectroscopy
Authors: Powell F. X. , Fletcher O. , Lippincott E. R.
Published: February 2005

The construction and performance of high intensity electrodeless arcs powered by a 3-kW rf oscillator, operating at about 5 Mc, are described. The inherent light intensity which is realized is as great as any system which uses electrodes. These sources have been used with mercury, cadmium, thallium, helium, potassium, rubidium, and cesium. Any substance which exhibits or is at a pressure near 10−3 Torr can be converted to a plasma by the technique described. The effectivenss of these arcs for use in Raman spectroscopy is illustrated.
Semiautomatic Single Crystal Orienter
Authors: Kelly J. W.
Published: February 2005

A semiautomatic method is described which enables the orientation of metal single crystals to be rapidly determined to within ±1°; it is a scanning method and requires a three-circle goniometer with automatic drives on two circles at right angles to each other, and a fast acting recorder. A further use of the instrument for the study of the perfection of metal single crystals is also demonstrated.
Pressure Distribution and Hysteresis Effects in a Tetrahedral Anvil Device
Authors: Deaton B. C. , Graf R. B.
Published: February 2005

Measurements have been made on the distribution of pressure and hysteresis effects in a tetrahedral anvil apparatus by simultaneously monitoring the resistances of calibration wires placed at various positions in the pyrophyllite tetrahedrons. A pressure gradient of about 1% is observed, and it is therefore suggested that pressure calibration wires may be placed on the tetrahedron face to determine the pressure throughout the tetrahedron volume. This technique will allow pressure calibration when sample porosity is not known and could possibly permit pressure calibration at elevated temperatures.
Packless All-Metal Ultra-High Vacuum Valve for Temperatures from −196°C or below to 450°C
Authors: Chapin Douglas S.
Published: February 2005

A type Y 440 Hoke valve has been modified so that an 18-carat gold disk is forced by a captive tool steel driver against a stainless steel seat. Gases in the valve contact only hard solder, stainless steel, the gold disk, and aluminum (or copper). One series of tests with a helium mass-spectrometer leak detector showed that, with several hundred closures each at temperatures around 450°, room temperature, and 77°K and repeated cycling, the conductance across the seat using a closing torque of 5 ft-lb was less than 10−10 cc(NTP)/sec. The driver is not removed for high-temperature operation or baking. No galling was experienced using a driver of oil-hardened tool steel against stainless steel with graphite lubrication. The need for a spring for withdrawal of the gold plate was eliminated by positive withdrawal with the driver. The valve is recommended for applications requiring one or more of the following features: (1) helium leak detector tight closure both from the atmosphere and across the seat; (2) bakeable; (3) all-metal; (4) operable over the region 450° down to 77°K or lower.
Two High Velocity Plasma Guns
Authors: Hagerman D. C. , Osher J. E.
Published: February 2005

The design and operating parameters of two coaxial plasma guns are described. The high speed gun performance depends upon the use of (1) gas valve ports near the muzzle end of the central electrode, (2) an optimized gas diffusion delay time, and (3) a small injected gas load. The 10-cm-diam gun employs a low inductance power supply and a light gas load to yield a plasma containing ∼5×1016 D+ ions with a mean energy of 13 keV. The larger 25-cm-diam gun requires more energy and a larger gas load to yield a plasma containing a similar number of D+ ions but at a higher mean energy of ∼20 keV. As an example of gun performance, the 25-cm-diam gun produces a neutron yield of ≈108 when incident upon a D2O ice target located 3 m from the gun muzzle.