bluuebunny/crossref_metadata_2025 huggingface dataset:
Coupling of space-time and electromagnetic gauge transformations
Authors: Cattaneo U. , Janner A.
Published: February 2004

A kind of topological extensions of a space-time group Q by an electromagnetic gauge group J are investigated in order to determine covariance groups of electrodynamics. Here Q stands for the Poincaré group, for the Galilei group, or for their neutral components, and J is the Abelian group of all real-valued functions of class Cm (m ∈ N or m = ∞) defined in space-time. The topological groups JφfQ so obtained, already important in the study of charged particles in external electromagnetic fields, are analyzed and placed in the general context of combining different symmetry groups. They are characterized by a given operation φ of Q on J and by factor sets f such that f(q,q′) is a constant gauge function for all (q,q′) ∈ Q × Q. It is shown that all these groups JφfQ are topologically isomorphic to the external topological semidirect product of Q by J relative to Φ.
Invariants of Born reciprocity theory
Authors: Shamaly A.
Published: February 2004

In an attempt to use Born reciprocity theory as a possible scheme for explaining elementary particles we calculate all the invariants of this theory. It turned out that all the invariants are functions of the operator (x2+p2). Thus there is only one independent invariant which characterizes this theory.
The T operator and an inverse problem for nonlocal potentials
Authors: Yao Te Hai
Published: February 2004

For a class of short-ranged nonlocal potentials, the T operator T(k) is studied in the region Imk> -γ, where γ > 0 is some parameter of the potential. Inversion formulas are obtained which determine the potential from t(E)=T(E) for any real E, for which t(E) is defined, perhaps with the exception of a countable set of points.
Polynomial algebras. II. Commutation relations
Authors: Raghavacharyulu I. V. V.
Published: February 2004

The present work completes the algorithm which Bhabha had prescribed so as to set up the commutation relations of spin algebras but could implement it only for spin one algebra using a third order permutation identity. Generally this work is concerned with the setting up of the commutation relations of derived polynomial algebras which are obtained by addition operation from a basic polynomial algebra. To obtain these commutation relations, a set of identities called Josthna identities are introduced among the permutations of a finite set of elements. With the help of these identities it is established that commutation relations for derived algebras can be set up directly. Applications to spin and parafield algebras are considered to obtain their commutation relations which make their deduction trivial.
Canonical transforms. I. Complex linear transforms
Authors: Wolf Kurt Bernardo
Published: February 2004

Recent work by Moshinsky et al. on the role and applications of canonical transformations in quantum mechanics has focused attention on some complex extensions of linear transformations mapping the position and momentum operators x̂ and p̂ to a pair η̂ and ζ̂ of canonically conjugate, but not necessarily Hermitian, operators. In this paper we show that for a continuum of complex linear canonical transformations, a related Hilbert space of entire analytic functions exists with a scalar product over the complex plane such that the pair η̂, ζ̂ can be realized in the Schrödinger representation η and −id/dη. We provide a unitary mapping onto the ordinary Hilbert space of square-integrable functions over the real line through an integral transform. The transform kernels provide a representation of a subsemigroup of SL(2,C). The well-known Bargmann transform is the special case when η̂ and iζ̂ are the harmonic oscillator raising and lowering operators. The Moshinsky-Quesne transform is regained in the limit when the canonical transformation becomes real, a case which contains the ordinary Fourier transform. We present a realization of these transforms through hyperdifferential operators.
Equilibrium statistical mechanics of relativistic particles with variable masses. I. Nonquantal theory
Authors: Hakim Rémi
Published: February 2004

The necessity for statistical mechanics of relativistic particles endowed with variable rest masses essentially arises from astrophysics (when dealing with clusters of stars or galaxies which do exhibit a mass spectrum) and from the statistical bootstrap model of Hagedorn and Frautschi for inclusive reactions of elementary particles. We begin this series with the simplest case of classical particles since this case demonstrates more clearly the main features of the theory. Moreover, this classical case is an excellent approximation for the statistical bootstrap near the ``hadronic boiling point.'' We first derive the one-particle distribution function using the standard maximization procedure, in the implicit case of a uniform mass spectrum. It is shown that the actual mass spectrum possesses a part due to thermal agitation. An equation of states is derived. Other distributions are obtained (energy, 4-velocity). In the case of weak collisions, space-time correlations for the numerical and proper energy densities are derived and applied to the hadronic matter near the ``hadronic boiling point.'' Finally, several extensions of these ideas are discussed.
Asymptotically simple space-time manifolds
Authors: Lerner D. , Porter J. R.
Published: February 2004

Asymptotic simplicity is shown to be k-stable (k≥3) at any Minkowski metric on R4 in both the Whitney fine Ck topology and a coarser topology (in which the Ck twice-convariant symmetric tensors form a Banach manifold whose connected components consist of tensor field asymptotic to one another at null infinity). This result, together with a sequential method for solving the field equations previously proposed by the authors, allows a fairly straightforward proof that a well-known result in the linearized theory holds in the full nonlinear theory as well: There are no nontrivial (i.e., non-Minkowskian) asymptotically simple vacuum metrics on R4 whose conformal curvature tensors result from prescribing zero initial data on past null infinity.
Exact solution of a one-dimensional three-body scattering problem with two-body and/or three-body inverse-square potentials
Authors: Calogero F. , Marchioro C.
Published: February 2004

The exact solution is presented of the scattering problem of three equal particles interacting in one-dimension via two- and/or three-body inverse-square potentials. Both the classical and the quantal problems are treated. It is shown that the outcome of this scattering problem is an extremely simple relation between initial and final momenta, the latter being univocally determined by the former even in the quantal case. The solvability of the problem, and the simple results just mentioned, are peculiar to the equal particle case.
Schrödinger equation with inverse fourth-power potential, a differential equation with two irregular singular points
Authors: Bühring Wolfgang
Published: February 2004

The Schrödinger radial equation with inverse fourth-power potential is treated analytically. Solutions in the form of integral representations of the generalized Laplace type are considered. Standard solutions are defined relative to each of the two irregular singular points of the differential equation. The coefficients in the linear relations persisting between any three of the standard solutions are obtained. The expressions for the coefficients, which contain some Taylor and Laurent series and finite determinants, are suitable for electronic computation. From the coefficients the S matrix and the scattering phase shifts may be obtained immediately.
Special relativity in general relativity?
Authors: Hirondel D.
Published: February 2004

Starting from the metric in harmonic coordinates for a test particle m1 around a heavy particle m2(m2≫m1) at rest, the EIH Lagrangian is recovered by making a Lorentz transformation, followed by a canonical transformation and an appropriate symmetrization in the two masses. This raises the question of a special relativity content in general relativity, a feature not directly implied by the general covariance.
Stability of stochastic functional differential equations
Authors: Chang M. H. , Ladde G. , Liu P. T.
Published: February 2004

A system of functional differential equations with random retardation, ẋ(t) = f(t, xt), is studied, where xt(θ) = x(t + θ), η(t, ω) ≤ θ ≤ 0, − r ≤ η(t, ω) ≤ 0, and η(t, ω) is a stochastic process defined on some probability space (Ω, μ, P). Some comparison theorems are stated and proved in details under suitable assumptions on f(t, xt). Sufficient conditions for stability in the mean for the trivial solution then follow. The usefulness of the sufficient conditions is illustrated by an example with two different Lyapunov functions.
Lattice Green's function of the body-centered cubic lattice at arbitrary points
Authors: Katsura Shigetoshi , Watanabe Hiroshi
Published: February 2004

Lattice Green's function for the body-centered cubic lattice at arbitrary points outside and inside the band is evaluated by the method of analytic continuation using Mellin-Barnes type integral.
Elimination of a coordinate singularity in the three-body problem
Authors: Hill Robert Nyden
Published: February 2004

One of the coordinate systems commonly used in the three-body problem consists of three center-of-mass coordinates, three interparticle separations, and three Euler angles specifying the orientation of the triangle whose vertices are the three particles. The usual specification of the Euler angles for this system, which aligns the axes of the body-fixed coordinate system with the principal axes of the moment of inertia tensor, results in a coordinate singularity whenever two of the moments of inertia are equal. An alternative specification of the Euler angles for the equal mass case which treats the three particles symmetrically and eliminates the coordinate singularity at the equilateral triangle configuration is presented.
Electromagnetic scattering from two circular, coaxial disks
Authors: Marin Lennart
Published: February 2004

The electromagnetic field scattered from two perfectly conducting, circular, coaxial disks is calculated when the incident field is a plane wave. Two quantities are of special interest: namely, the electric field at the center of the axis of the two disks and the integral of the electric field along the axis between the two disks. Analytical expressions for the low-frequency behavior of these two quantities are derived in the case where the distance between the two disks is large compared to the radii of the disks. For other frequencies and for separations of the two disks not too large these two quantities of interest are calculated numerically. Expressions for the scattered far field are also derived.
Condensation and gelation: Clarification of Stockmayer's analogy
Authors: Cohen Claude , Gibbs Julian H. , Fleming Paul D.
Published: February 2004

To explore the analogy, originally noted by Stockmayer, between vapor condensation and gelation in ``three-dimensional'' chemical polymerizations, we here explore the special case of reversible gelation in more detail. We show how the partition function of a one component system the molecules of which reversibly form branched-chain clusters can be adapted, under certain approximations, to display its correspondence to Stockmayer's formulation of the molecular size distribution in branched-chain polymers formed from random chemical polymerization of polyfunctional monomers. Thus, we obtain, for the reversible case, a statistical thermodynamic counterpart to Stockmayer's purely statistical calculations concerning gelation by relating his ``extent of reaction'' α to the thermodynamic variables temperature and density. The relation between Stockmayer's gelation theory and Mayer's condensation theory is accordingly clarified. A key step in this analysis involves the use of Hill's criterion for a ``bond.'' The similarity of condensation to gelation is noted to be particularly close in the case of liquids with directional interactions which saturate at low coordination numbers. In such cases, of which water is the outstanding example, the condensation-gelation analogy provides a helpful physical picture of the liquid state.
13C NMR chemical shift anisotropy for benzene adsorbed on charcoal and silica gel
Authors: Kaplan S. , Resing H. A. , Waugh J. S.
Published: February 2004

The 13C NMR chemical shift anisotropy powder patterns under conditions of proton decoupling have been determined for benzene (13C enriched) adsorbed on charcoal and silica gel and for toluene adsorbed on charcoal. These spectra do not differ significantly from those of the pure solid as far as principal values of the chemical shift tensor are concerned. The simultaneous presence of molecules in various states of motional narrowing of the anisotropy powder pattern is revealed, in agreement with earlier observations of dipolar broadened proton spectra for similar systems. Motional narrowing effects observable for the toluene molecule in the adsorbed state aid in the assignment of principal axes.
Static and dynamic paramagnetism of the undistorted triplet state of benzophenone
Authors: Shain Albert L. , Sharnoff Mark
Published: February 2004

Existing discrepancies in reports of the EPR fine structure of triplet traps in uv-excited benzophenone are clarified by studies of the population kinetics and the EPR of triplet benzophenone-h10 in crystals of deuterobenzophenone. Benzophenone-h10 provides a triplet trap of depth ≈30 cm−1 below the triplet exciton band of the deuterobenzophenone host and phosphoresces copiously at liquid helium temperatures. In deuterated crystals containing 1 mole% benzopheone-h10, only the phosphorescence of ordinary benzophenone is detectible below 4.2°K; the quantum yield is 42%. The ordinary benzophenone traps are shown to have the same conformation as the triplet molecules formed by direct T1←S0 absorption and the molecules responsible for the excitonic phosphorescence of ordinary benzophenone crystals. The traps earlier reported by Sharnoff are shown to have nearly this conformation. The triplet states of the traps reported by Chan, Schmidt, Veeman, and van der Waals and by Winscom and Maki are shown not to have this conformation. The kinetics of depopulation of triplet benzophenone are shown to be sensitive to the conformation of the emitting state. The decay rates from the spin sublevels of undistorted triplet benzophenone-h10 molecules are kz = 768 sec−1, ky = 70 sec−1, and kx = 60 sec−1. Population heavily favors (85%) the z sublevel. At liquid helium temperatures the zero-field EPR transitions have the frequencies 1241 MHz (x ⇄ y), 3930 MHz (y ⇄ z), and 5171 MHz (z ⇄ x). The z sublevel is highest in energy.
Additional molecular bound states in a diabatic approach
Authors: Atabek O. , Lefebvre R.
Published: February 2004

The bound states which may result from the interaction between a discrete state and a continuum of states truncated from below are investigated in a diabatic approach for two models of a diatomic molecule. In each case the bound level can be identified as being a level allowed for by the potential energy changes resulting from the electronic configuration interaction. The various possibilities for the bound state to appear along the diabatic → Born-Oppenheimer → adiabatic → nonadiabatic chain of calculations are also discussed.
Spectrum of light scattered from a viscoelastic gel
Authors: Tanaka Toyoichi , Hocker Lon O. , Benedek George B.
Published: February 2004

We report measurements of the spectrum of light scattered from thermally excited displacement fluctuations in polyacrylamide gels. These measurements have been carried out on the polarized scattered light as a function of scattering angle and temperature for 5% and 2.5% polyacrylamide gels using the methods of optical mixing spectroscopy. We also present a theory for the amplitude and time dependence of the thermally excited longitudinal and transverse displacements of the gel fiber network. These displacements are responsible, respectively, for the polarized and depolarized scattered light. The correlation function for the displacements having wave vector q is predicted for these gels to have the form of an exponential decay: exp(− Γt). The decay rate is given by Γ = Glq2/f or Gtq2/f, where f is the frictional force per unit volume on the fiber network as it moves with unit velocity relative to the gel liquid. Gl is the longitudinal compressional modulus for longitudinal displacements and Gt is the shear modulus for transverse displacements of the fiber network. We have measured, using macroscopic methods, the friction factor f, and the elastic moduli Gl, Gt and compared the numerical predictions of the theory with the experimental measurements of the correlation function of the scattered light intensity. The theory is quite successful in predicting the size and q dependence of the decay rate of the time correlation function of the scattered light. Conversely, these experiments demonstrate that the correlation function of the light scattered from thermal fluctuations of the gel fiber network provides a detailed quantitative characterization of the viscoelastic properties of gels.
50 Microdegree Temperature Controller
Authors: Larsen N. T.
Published: February 2004

A temperature controller has been developed using a platinum resistance thermometer in a bridge with inductively-coupled ratio arms. It is capable of maintaining water bath temperatures constant to within ±25 microdegrees Celsius for 24 h in an environment varying as much as ±1.5°C at any temperature from 18 to 28°C. The sensitivity of the controller approaches the theoretical limitation imposed by Johnson noise. The design makes possible control dials which are direct reading in °C.
Measurement of the Polarization of Thermal Neutron Beams of Mixed Velocities
Authors: Barkan S. , Bieber E. , Burgy M. T. , Ketudat S. , Krohn V. E. , Rice-Evans P. , Ringo G. R.
Published: February 2004

We have tried three methods of measuring the polarizations of beams of thermal neutrons reflected from magnetized mirrors. These methods were based on (a) depolarizers, (b) a current-carrying foil (Dabbs foil), and (c) a Stern-Gerlach magnet. The Stern-Gerlach method appears to be the most reliable; with reasonable care it is accurate to ±1%.
New Design for an Automated Bacterial Colony Counter
Authors: Ingels Neil B. , Daughters George T. , Burzio Agostino
Published: February 2004

The discovery that translucent bacterial colonies growing on the surface of an agar medium take the form of spherical lenses allows the design of a new generation of automated bacterial colony counters. The lens properties of these colonies are explored in detail and a parallel scanning technique, ``nearest neighbor inhibition,'' which allows an electronic system to produce only one count for each colony detected, is described. A complete colony counting instrument is presented and its possible sources of error are discussed.
Photon Coupled Stimulus Isolation Unit
Authors: Duffin E. , Geselowitz D. B. , Briller S. A.
Published: February 2004

A photon coupled stimulus isolation unit designed for myocardial stimulation is described. Canine records are presented illustrating the effectiveness of the device in reducing electrical stimulus artifacts in electromagnetic flowmeter recordings.
Hot-Film Sensor for the Study of Wall Turbulence Phenomena
Authors: Armistead Robert A. , Keyes John J.
Published: February 2004

A stable, durable hot-film sensor has been developed to enable the direct determination of the local instantaneous rate of heat transfer from a small source at the interface between a solid wall and a turbulently flowing fluid. This instrument can be adapted to any geometry by contouring to fit flush with the surface. A study of the dynamic response of the sensor energized by a Lintronic Laboratories constant temperature compensating circuit indicated that in the worst case (lowest Reynolds number) considered, the frequency response should be flat up to approximately 4000 cps. Heat-transfer intensities and dimensionless power spectra obtained with these sensors were in good agreement with measurements made by other experimenters using mass-transfer and pressure-sensing techniques.
Nanosecond Rise Time, High Power, Variable Delay Double Pulser with Application to Electron-Hole Plasmas
Authors: Robbins William P. , Lantz Robert M. , Ancker-Johnson Betsy
Published: February 2004

A new double pulse system has been designed and tested which offers several advantages over previous methods of generating and delaying one square wave pulse with respect to another. Characteristics of the new system are: fast rise and fall times (2 nsec typical); high power pulses (150 V into 50 Ω); very low time jitter (less than 0.2% of pulse separation time); accurate repeatability of time delay (±1% typical); extremely wide range of time delay (nanoseconds to milliseconds); dc readout of the time separation of the two pulses accurate to ±1% and suitable for X-Y pen recorders. A special summing junction circuit allows both pulses to be applied to the same load without power being split between the load and the other pulse generator, and also without the first pulse prematurely triggering the second pulse or affecting its amplitude. Some results obtained by applying this system to the study of electron-hole plasma decay are briefly presented.
Cryostat for Radiation Damage Experiments
Authors: Peters P. B. , Shearin P. E.
Published: February 2004

A cryostat designed especially for the performance of experiments where metals at low temperatures are irradiated by high energy electrons is described. This device is ideally suited for isochronal anneal studies of the recovery spectrum following irradiation. The sample holder used is also described.
Recording Fabry-Perot Interferometer
Authors: Kuhn H. G. , Lewis E. L. , Stacey D. N. , Vaughan J. M.
Published: February 2004

A recording interferometer is described in which a direct plot of spectral intensity against wavenumber is obtained without the use of a time base. When used as a double recorder, the instrument records two spectral profiles simultaneously. In this form, the recorder is particularly suited to the comparison of spectral profiles and the measurement of small line shifts.
Apparatus for the Thermal Diffusion Separation of Stable Gaseous Isotopes
Authors: Rutherford W. M. , Weyler F. W. , Eck C. F.
Published: February 2004

An efficient and easily fabricated thermal diffusion column design was developed for the thermal diffusion separation of stable isotopes. The design is based on the use of commercial tubular electric heaters for the hot wall. As many as 18 of these columns can be placed in a common cooling water jacket. Tests of a prototype column with argon, methane, and xenon gave results in reasonably good agreement with theory. Application of the column design and associated equipment and techniques was demonstrated by the successful operation of a 24-column 6-stage cascade for enriching 124Xe.
Current Sweep Circuit with Sweep Speed Feedback
Authors: Leslie J. D. , Smith H. J. T. , Van Beek B.
Published: February 2004

A current sweep circuit is described which allows the quick and accurate recording of narrow current peaks in the I-V characteristic of a Josephson tunnel junction driven by the circuit. A feedback feature senses the current peaks and slows the sweep rate in these regions to allow for the finite slewing speed of the X-Y recorder. The performance of the circuit is demonstrated using a simple test arrangement.
Vibrating Sample Magnetometers
Authors: Noakes J. E. , Arrott A. , Haakana C.
Published: February 2004

In order to eliminate the sensitivity to field noise and microphonics of a vibrating sample magnetometer it is sufficient to add trimming coils which are adjusted to produce no signal when the applied field is deliberately driven at the frequency ω0 which is to be used for vibrating the sample. A mechanical chopper which discriminates against all even harmonics and against third harmonics is discussed. The use of eddy currents to precisely align a sample in a null measurement of magnetization is described.
Microminiature Pirani Gauge for Measurements of Low Pressures
Authors: Rayfield G. T. , Boynton F. P. , Potter O. W.
Published: February 2004

The design and operation of a small Pirani gauge, suitable for surface pressure measurement in low density flows, are described. The gauge is made from two microminiature lamp elements. One element senses the external pressure, and the other provides temperature compensation. The electrical circuitry is essentially a Wheatstone bridge. The pressure range is approximately 0.1–10 Torr, with a possible accuracy of 2%.
AgCl Seal: A Simplifying Improvement
Authors: Caras Bernard
Published: February 2004

A simplification and/or improvement for AgCl seal to glass is presented. Metallization of the seal area was avoided. Instead, preferential spreading of molten AgCl on glass was achieved via local surface grinding of the glass seal area. Direct visual and microscopic inspection of the entire seal was made possible by elimination of the opaque metallization.
Four-Sequential-Output Generator for Research in Electroanesthesia
Authors: Deutsch Sid
Published: February 2004

Focusing is important in electroanesthesia research because it is conjectured that we should achieve high current density in some internal structure and zero current elsewhere. If current is applied sequentially to many opposing electrodes on a solid conducting sphere, the current density magnitude at the center of the sphere is three times the average current density under each electrode. This technique thus appears to focus current although, in reality, the individual current flow lines diverge. Because of the presence of low resistance pathways in an actual brain, however, the results using the homogeneous sphere model are only qualitatively correct. A four-sequential-output unit is described. The outputs are individually controlled so that it is possible to alter the internal current density distribution, in the experimental subject, by decreasing one output while increasing another. Each output supplies maximum values of 250 V peak open circuit and 50 mA peak short circuit.
Cell for Dielectric Measurements in the High Radio Frequency Region
Authors: O'Konski C. T. , Edwards Adrian
Published: February 2004

The design and construction of a dielectric cell and adaptor suitable for use with the Boonton RX meter are presented. The geometry of the cell can be varied easily to accommodate a wide range of permittivity. Data illustrating the cell performance are included for several known liquids.
Mass Selector for Ion Beam Experiments
Authors: Theard Lowell P.
Published: February 2004

A mass selector which efficiently produces mass filtered beams of both primary and secondary ions in the medium current ranges is described. Currents up to 10−6 A for the mass filtered beam can be obtained with beam energies of 3–5 keV. Ions are produced in a hot cathode, gas discharge ion source of relatively simple construction, and are extracted as a parallel beam. Mass analysis is accomplished over a short pathlength with a compact, high current, sector field electromagnet which is entirely contained within the analyzer chamber. An electrostatic quadrupole lens is used for optimum shaping of the incident ion beam for high transmission through the magnetic sector. A second quadrupole lens is used to restore parallelism to the mass filtered ion beam and is mounted beyond the image slit, which was made wide enough to pass the entire image focused beam. The instrument has no object slit, as the entire incident beam is brought to a crossover at the object position. Beam transmission through all elements in the analyzer chamber, including the two quadrupole lenses, the sector magnet, and the image slit, is approximately 50%. Oscillating beam scanners are used to measure the beam density profile and to monitor the mass spectrum. The resolving power for spatial separation is about 60. Secondary ions such as N4+ and CH5+ can be generated with intensities comparable to those of primary ions.
High Temperature Debye-Scherrer X-Ray Camera
Authors: Intrater Josef , Smith Deane K.
Published: February 2004

A multipurpose, high temperature, Debye-Scherrer camera has been constructed which has a temperature range from −100 to 1050°C. Temperatures may be controlled to less than 1 C° with gradients essentially nonexistent. Samples are hung vertically to minimize any chance of sagging, and are rotated in a ball bearing guided mechanism. The unit may be operated in high vacuum or in special atmospheres. The film cassette is detachable and self-positioning. Using the camera fiducial marks, accuracies to 1 part in 5000 are obtainable. The film cassette covers the range from −45°2θ to 135°2θ with the region from −12°2θ to 12°2θ blocked by the beam stop. Exposure times are comparable with standard Debye-Scherrer cameras. The general construction is relatively simple. Furnace elements are easily replaceable. Water cooling paths are straightforward with all connections between detachable parts of the unit being external. The cover assembly which supports the specimen and its drive mechanism is self-aligning to assure correct centering of the specimen in the camera.
Method of Applying a Modern Potentiometer for Resistance Thermometry
Authors: Daneman H. L. , Mergner G. C.
Published: February 2004

In resistance thermometry, a potentiometer can have certain advantages over a resistance bridge. The method described consists of using the ratio of the ``measure'' to the ``standardize'' voltage of a conventional dc precision potentiometer to measure the ratio of a thermometer resistance to a resistor of known value connected in series with the thermometer. By appropriate selection of potentiometer and thermometer currents, potentiometer range, and known resistor, a measurement direct reading in ohms, or Rt/R0, is obtained. Normal potentiometer measuring procedure is used. Reversal of thermometer current to avoid influence of thermoelectric effects may be included. Tables are provided which indicate temperature resolution achievable by this method at various temperatures and levels of nominal thermometer resistance. Advantages and disadvantages compared with a bridge method are presented and discussed, as are experimental results using the two methods.
Apparatus for Adiabatic Rotation of a Sample in a Magnetic Field at Liquid Helium Temperatures
Authors: Halloran M. H. , Kunzler J. E.
Published: February 2004

An apparatus for adiabatic rotation of a sample in a magnetic field at liquid helium temperatures is described. It has been used for the observation of magnetothermal oscillations of metal single crystals as a function of their orientation in a magnetic field. While the sample is being rotated, magnetothermal oscillations as small as 10−6 K were observable; nonsteady (random) heat transfer or heat generation (heat pulses) under favorable conditions was found to be less than 10−5 K (a few milliergs). It appears that the apparatus is useful for a variety of other experiments where it is desirable to change the orientation of a sample in a solenoid either adiabatically or isothermally.
Direct Display of Electron Temperature in Magnetized and Time Varying Plasmas
Authors: Zakrzewski Z. , Beaudry C. , Cloutier G. G.
Published: February 2004

A method of direct display of electron temperature, which uses three closely spaced Langmuir probes at constant biases, is presented. Ion components of probe currents, which are relatively large in magnetized plasmas, are subtracted in the probe circuit. Direct display of the local value of the electron temperature is possible without any sweeping to the probe voltage. The sources of error are known and their effect can be readily evaluated during the experiment. Measurements of electron temperature in a P. I. G. discharge in hydrogen is presented as an example of application of this method.
Airborne Low Frequency Antenna Q Meter
Authors: Orsten G. S. F.
Published: February 2004

Low frequency radio astronomy measurements in space require a precise measurement of the impedance characteristics of the antenna. With weight, space, and electrical power at a premium, an instrument is needed to make measurements of X and R on command from a programmer or other source, and deliver the measurements with an output signal of 0 to +5 V, dc, ready for telemetry. Such an instrument, using less than 300 mW of power, is described.
Indium Arsenide Laser for Use in Infrared Detector Response Time Measurements
Authors: Linden K. J.
Published: February 2004

Indium arsenide lasers have been used in measuring both risetimes and fall times as short as 60 nsec in impurity-activated germanium detectors. The diffused lasers are pulse-excited by an avalanche transistor circuit and emit narrow band infrared radiation at 3.175 μ when operated at liquid nitrogen temperature, thereby providing a convenient means for the measurement of infrared detector response times at this wavelength. The method is applicable to photoconductive, photovoltaic, or photoelectromagnetic detector response time measurements.
Flexible High Voltage Supply for Experimental Electron Microscope
Authors: Lewis R. N. , Jung E. A. , Welter L. M. , Van Loon L. S. , Chapman G. L.
Published: February 2004

A system of power supplies has been developed to operate a new scanning electron microscope. The high voltage supply is variable from 9 to 30 kV in steps of 0.58 V and has a peak-to-peak ripple of 50 mV and an instability of 4 ppm/h. A corona-free ``hot top'' provides ample space for circuits which are referenced to the high voltage output and includes a 0.6 to 1.6 kV supply for a field emission electron source. This supply exhibits an instability of 20 ppm/h and a peak-to-peak ripple of 10 mV. The use of rechargeable batteries as the energy source within the ``hot top'' eliminates noise and leakage problems which are typically encountered when using high voltage isolation transformers for this application.
Calibration of the Electrode Spacing of a Dielectric Sample Holder
Authors: Levi A. A.
Published: February 2004

Some dielectric sample holders with adjustable micrometer electrodes lose their calibration when used at other than room temperature. A method is presented to calibrate the electrode spacing, and results are given that show reliability of the method.
Field Due to Current in Toroidal Geometry
Authors: Bhadra Dilip
Published: February 2004

Analytical expressions have been obtained to represent the field due to various types of steady current distributions in a torus. Of interest are some symmetric current distributions: uniform density surface and volume current distributions; and currents with density varying inversely as the distance from the axis (e.g., the distribution obtained when a radial cut is made in the torus and a constant emf is applied across it). Also, suitable expansions have been obtained for fields due to a helically wound current-carrying coil in a torus. Finally, certain inherent analytic difficulties in determining true magnetic surfaces in this case are pointed out.
POLLY I: Operator-Assisted Bubble Chamber Film Measuring System
Authors: Barr R. G. , Clark R. K. , Hodges D. , Loken J. G. , Manner W. E. , Musgrave B. , Pennock P. R. , Royston R. J. , Wehman R. H.
Published: February 2004

A new computer-controlled, bubble chamber film measuring device has been designed, constructed, and has been in use since July 1967. It uses a cathode ray tube as the digitizing light source. The unit of measurement is a ``slice scan'' which is the flying spot digitization of a small, variable-sized, rectangular area that can be oriented in any one of 32 equally spaced directions around 360°. Facilities are provided for an operator to view the picture currently being measured and to engage in an efficient dialogue with the control computer. Measurement of film is controlled by computer programs and has proceeded at a maximum rate of 60 two-prong events per hour, with the computer requesting operator assistance when required. A coordinate precision of about ±2 μ on 70 mm film is attained.
Constant True Strain Rate Apparatus
Authors: Lautenschlager E. P. , Brittain J. O.
Published: February 2004

A variable speed motor and a step gear train have been combined to form a drive input to the speed control of an Instron tensile machine to produce a nearly constant true strain rate. The apparatus functions for both tension and compression over a wide range of strain rates.
Frequency Modulation CW Technique for the Measurement of Very Small Changes in Ultrasonic Velocity
Authors: Melcher R. L. , Bolef D. I. , Merry J. B.
Published: February 2004

An improved continuous wave technique capable of measuring changes in ultrasonic velocity of 1 part in 107 or better is described. The technique utilizes frequency modulation of the cw carrier signal and subsequent lock-in amplification.
Specific Heat of Some Polymers Used in Cryostat Construction (1.7 to 4 K)
Authors: Zoller Paul , Decker P. R. , Dillinger J. R.
Published: February 2004

The specific heats of Araldite 502, Epibond 121, and Epibond 100A have been measured at temperatures between 1.7 and 4K. Results are given in the form of fits to the relation C=AT3+BT5+CT7+DT9 and in a table of selected values.
Amplitude Stabilizer for Magnetic Field Modulators
Authors: Alon Yosef , Shaltiel David
Published: February 2004

It is desirable to stabilize the amplitude and phase of magnetic field modulation applied to dc swept laboratory magnets for better approximation of true line shape, when large sweeps affect modulation coil impedance along with magnet yoke permeability. A stabilizing circuit is proposed in the form of a gain-controlled preamplifier, the control signal being derived from the integrated output of a pickup coil, which is also used as reference for synchronous detection. This instrument adapts to existing power modulators to provide a unity cosine reference signal and to stabilize modulation amplitude to 1% over 3 decades of dynamic range, over a band of 25 cps to 150 kc. The use of the instrument in ESR spectrometry is demonstrated; in a specific case of measuring the g shift of magnetic impurities in metals, results obtained with and without the use of the stabilizer are compared. Detecting a broad line of 1380 G at 16.5 kG center field with standard equipment produces an apparent shift of the line center of 280 G, due to modulation changes. By using the stabilizer, the real smaller shift can be recovered and the line shape is practically restored. Design features and necessary construction details are included.
Capillary Bearings
Authors: Reno Robert , Young Niels
Published: February 2004

A circular ring can be centralized by capillary forces when it is wetted by liquid within a cylindrical hole. This behavior is analyzed and the results of computation are given as a guide to designing capillary bearings at ambient and at zero gravity. Experimental results confirm the theory.
X-Ray Spectrographic Camera
Authors: Koenig Jude H. , Schoeffel James A. , Carron Gene J.
Published: February 2004

Polaroid film records of the x-ray spectral range 0.5 to 7 Å are obtained with a compact x-ray spectrographic camera. Samples ranging in size from virtually any bulk specimen to those of microgram quantity can be analyzed nondestructively. The camera operates with either x-ray spectrographic or x-ray diffraction tubes and requires analysis times of 1 to 60 min.
Plasma Electron Density Measurement with a Feedback Oscillator
Authors: Simonen T. C. , Tutter M.
Published: February 2004

A new method is described to measure average plasma number density using a feedback oscillator. This simple technique is applicable for electron densities ne≤1010 cm−3 and has the novel feature that it can be calibrated to read the density directly on a digital frequency counter. Using an argon plasma, density measurements are made and good agreement is found with independent Langmuir probe data. The feeeback oscillator technique essentially measures the dielectric constant and thus has a wide range of application.
Techniques and Instrumentation for Measuring the de Haas-van Alphen Effect in Metals
Authors: Windmiller L. R. , Ketterson J. B.
Published: February 2004

The field modulation measurement technique is currently being used to obtain accurate and complete de Haas-van Alphen spectra for many metals. A system is described, consisting of a superconducting magnet and low temperature cryostat, which is capable of simultaneously extending the measurement ranges for temperature down to 0.3 K and for magnetic field up to 62 kG. In addition, techniques for accurate alignment of the specimen in the magnetic field and electronic instrumentation important for the detection of dHvA spectra are discussed. Finally, accurate temperature measurement techniques are described which are currently being used for the precise determination of effective cyclotron masses in metals through the amplitude dependence of the dHvA effect.
Linearization of Thermocouple Voltages
Authors: Conrad Gerald
Published: February 2004

A Wheatstone bridge, with a thermocouple as the source of bridge voltage, and a temperature-dependent arm, can have a voltage output which contains a square term in the temperature. If this output is connected in series with that of another thermocouple, the combined voltages may be more or less linear than that of the thermocouple alone, depending on the temperature range, and the polarity of the series connection. In particular, in the range extending 50° each side of 0°C, good linearity may be obtained. This may have some value for obtaining realtime readout of temperatures for meteorological purposes.
Scanning Microwave Echo Box Spectrometer
Authors: Radford H. E.
Published: February 2004

A resonant cavity microwave spectrometer for wavelengths between 3 and 30 cm, which uses radar echo boxes as absorption cells, is described. The minimum detectable absorption coefficient at 10 cm wavelength is 10−10 cm−1, and this sensitivity is maintained during frequency scans by automatic feedback tuning of the echo box. The spectrometer is well suited to studies of gaseous chemical reactions, and some preliminary observations are reported, including the negative results of a search for the 10 cm spectrum of CH, and measurements of OH spectra at 4.7 and 6.0 GHz.
Microsecond Response System for Measuring Shock Arrival by Changes in Stream Electrical Impedance in a Shock Tube
Authors: Dannenberg Robert E. , Humphry Donald E.
Published: February 2004

An instrument is described that is suitable for measuring the position and velocity of high speed compression waves, rarefaction waves, and gas interface regions in shock tubes. The sensor is a twin electrode probe mounted in the wall of the tube with a small dc voltage impressed across the electrodes. A simple power supply, amplifier, and gate pulse generator complete the instrument. The probe provides a sensitive microsecond response to changes in the electrical impedance of the gas stream flowing across the sensor. In addition, the probe is inexpensive, rugged, and easy to install. It has been possible to correlate the output signals from this instrument with the different regions of shock tube flow at shock speeds from 2.29 to 7.01 km/sec into air.
Temperature Control System for Small Angle X-Ray Scattering Experiments
Authors: Gravatt C. C. , Brady G. W. , Lundberg J. L.
Published: February 2004

A temperature control and measurement system is described in which it has been possible to obtain temperature stability of ±0.003 C° for periods of weeks over the temperature range from 75 to 200°C. The constant temperature cell was designed to fit between the crystals of a Hart-Bonse type, small angle diffractometer. With minor modifications it can be used with a wide range of instruments.
Transmission Electron Microscopy with an ARL Microprobe
Authors: Murphy A. P. , Metzger C. A.
Published: February 2004

A method has been devised to permit a scanning transmitted electron image of the sample to be displayed in the ARL electron microprobe. This technique permits ultrathin sections prepared for electron microscopy to be transferred to the electron probe where the same area seen in the electron microscope can be easily found. Areas as small as 1 μ diam can then be accurately positioned under the stationary electron beam to permit elemental analysis of fine structures. The low sample current required (1 nA) permits good resolution of fine detail with no detectable damage to the specimen, thus leaving it intact for further electron microscopy. The determination of Ca/P molar ratios in a precipitate from a calcium phosphate solution is cited as an example of the method.
Apparatus for the Precision Measurement of Internal Friction
Authors: Detwiler D. P. , Holden S. J. , Sowa W. A. , Woronowicz T. J. , Heslin T. M. , Hudick M. G.
Published: February 2004

An apparatus, which permits routine measurement of internal friction as low as 2×10−7 and Young's modulus as a function of temperature, frequency, and strain amplitude in extremely low loss materials, is presented. The system described herein can be used to investigate a variety of materials and is not hampered by the limitations placed upon composite resonator systems. It has been successfully used to study internal friction in the amplitude-independent and amplitude-dependent regions in pure and CaCl2-doped NaCl.
Timed Signal Grounding Switch for Observation of Low Level Signals following Large Transients
Authors: Czerlinski George H.
Published: February 2004

A signal grounding circuit and the associated timing control circuits designed for the observation of low level signals that follow large initial transients are described. The transition between grounding (<1 Ω) and ungrounding (>100 MΩ) proceeds within about 1 μsec (with a jitter in ungrounding time of the same amount). Attenuations of 60 to 80 dB are easily obtained. The (exponential) discharge time constant of a transient step was designed to become as small as 1 μsec (stepwise variable up to 2 msec).
Transient Voltage Decoupling Elements
Authors: Gruber J. E.
Published: February 2004

Premature and inexact timing of thyratron generators may occur during parallel operation of capacitor discharge circuits. Voltage transients which enter the trigger circuits can be eliminated by decoupling spark gaps. A simple, two electrode, spark gap with corona illumination is described. The low jitter of this gap allows its insertion in the output line of a 15 kV thyratron generator without changing the output performance of the generator.
Interferometer for Determining Autocollimator Errors
Authors: Saunders M. J.
Published: February 2004

A simple interferometer comprised of two glass plates and a frame for changing the angle between the plates is described for the determination of the measurement errors of an autocollimator. The interferometer is useful in that it generates angles which are measured with an autocollimator and allows the values of these angles to be determined by counting the passage of multiple beam interference fringes. The instrument is easy to use and is very insensitive to both thermal gradients and vibration. The sensitivity of the interferometer depends upon the wave-length and the distance from the wedge apex to the point at which the fringes are observed and, for this instrument, can be varied from about 1 to 3″/fringe. For the particular location at which the fringes were observed in this experiment, the sensitivity of the interferometer is 1.429±0.004″/fringe. Typical percentage errors obtained in measurements of three autocollimators varied from 0.2 to 1.0% over a range of 285.8″.