Volume 30, Issue 2, February 1959
Index of content:
30(1959); http://dx.doi.org/10.1063/1.1716491View Description Hide Description
A laboratory tube has been developed which produces scale models of the forms assumed by streams of charged particles in the earth's dipole magnetic field. The forms are unexpectedly intricate and complicated, as are also the contacts on the earth's surface. Photographs of some representative stream forms and contacts are presented. The tube has served as an analog computer for stream forms and contacts and, in addition, has revealed the importance of the generation of ring currents of charged particlesscattered into Störmer's periodic orbits. The same techniques can be applied in studies of stream forms in high‐energy accelerators and in other complicated kinds of magnetic fields.
30(1959); http://dx.doi.org/10.1063/1.1716492View Description Hide Description
The instrumentation used, the measurements obtained, and the uses of the Vanguard I satellite are described. This satellite contains two transmitters, one powered by batteries for about three weeks and one powered by solar cells (still operating). From the transmitted frequencies temperature information and rotation rates are obtained. The transmitted signals are also used to determine the satellite orbit. An approximate free orbital lifetime of 200 years is predicted.
30(1959); http://dx.doi.org/10.1063/1.1716493View Description Hide Description
Equipment was constructed to demonstrate the practicability of using a Vidicon camera tube for measuring the space orientation of spin stabilized Aerobee‐Hi research rockets. While ordinary television pictures are badly blurred by camera rotation, laboratory photographs which were obtained by means of a spinning, line‐scan camera demonstrated that this method can be used to obtain pictures whose quality is similar to those of standard television.
30(1959); http://dx.doi.org/10.1063/1.1716494View Description Hide Description
30(1959); http://dx.doi.org/10.1063/1.1716495View Description Hide Description
The modification of the single particle theory of particles subject to radio‐frequency acceleration caused by electrostatic repulsion between particles is calculated. With the aid of an appropriate Hamiltonian the Boltzmann equation is reduced to a one‐dimensional integral equation for the case of a uniform particle density in a limited region of phase space. For a range of parameters that includes most accelerators, this equation is approximated by an algebraic equation, and an analytic solution valid below the transition energy is obtained. Computations are given of the ``longitudinal space charge limit,'' as well as the effect of space charge on the azimuthal bunching of a beam by an accelerating cavity. Numerical examples of these two effects are given.
30(1959); http://dx.doi.org/10.1063/1.1716497View Description Hide Description
A transistorized marginal oscillator type of nuclear resonance probe is described. The main advantages of transistor use are in obtaining portability, eliminating external power sources, and low cost. The sensitivity and stability equaled that of a standard transition vacuum tube circuit when compared using protons in water.
30(1959); http://dx.doi.org/10.1063/1.1716498View Description Hide Description
The roots of polynomials of high degree are obtained with a stated accuracy in a time of ten to thirty minutes by use of an electromechanical harmonic synthesizer. The machine consists of sine‐cosine potentiometers which are driven by meshed gears to produce sinusoidal potentials of frequency f, 2f, 3f, …. The algebraic polynomial is transformed into a trigonometric polynomial in which the terms are expressed in multiple angle form and applied to the machine. As the fundamental gear is rotated through 180°, the potentials are summed in a recording high impedance voltmeter in such a manner that when the curve f(θ)=0 passes through zero values, the angles are read from a large dial and the roots x=r cos θ are obtained.
Examples of the solutions are given, and the results of some twenty‐five solutions reported to show an average accuracy of 1.19% and an average time of solution of 16 minutes. For higher accuracy a time of about 7 minutes is required for each additional substitution, until an accuracy of 0.30% may be obtained. Multiple or repeated roots are obtained by use of the factor theorem and repeated differentiation.
30(1959); http://dx.doi.org/10.1063/1.1716499View Description Hide Description
Electrical leads carrying currents into cryogenic apparatus also introduce heat. Even with an ideal Carnot cycle, the mechanical power needed to remove this heat can be one hundred or more times the heat flow itself. If the currents and hence the input leads are heavy, a very sizeable refrigerator may be required. In this article the configuration of the leads which minimizes the influx of heat is derived theoretically, taking variations in thermal and electrical conductivity into account. Graphs are given for the minimum heat flow and optimum cross section of a copper input lead carrying arbitrary currentI. The optimum is found to be fairly sharp. If the diameter of the lead differs by a factor of two from the optimum, the influx of heat is increased by over 100%.
30(1959); http://dx.doi.org/10.1063/1.1716472View Description Hide Description
A short duration (1 or 2×10−8 second) high‐intensity explosive light source, that may be used in the laboratory, has been proved experimentally. The charge, weighing 4.8 grams, yields a luminosity estimated in the neighborhood of 8×107 lumens. Pictures of high‐speed shocks in air, transparent solids, and metal jets have been taken using this lighting system.
30(1959); http://dx.doi.org/10.1063/1.1716473View Description Hide Description
Using paralleled power transistors driven by a transistor and a chopper amplifier, supplemented by a coarse feedback loop to the generator field, we have regulated to <0.001% the field of an electromagnet requiring 80 amp at 200 v. The dissipation in the regulator is 250 w. The magnet current may be varied from zero to maximum by setting the reference potentiometer to the appropriate voltage, and sufficient protective measures are incorporated so that the circuit is not injured by misuse. The circuit is usable to perhaps a megawatt.
Construction and Characteristics of Teflon‐Covered Polarographic Electrode for Intravascular Oxygen Determination30(1959); http://dx.doi.org/10.1063/1.1716474View Description Hide Description
30(1959); http://dx.doi.org/10.1063/1.1716476View Description Hide Description
The thermoelectric force developed by the following junctions up to 2200°C has been measured: Re vs W, Re vsMo, Re vs W‐30Re, and Re vs Mo‐50Re. The thermoelectric force for W vs W‐30Re and Movs Mo‐50Re has been calculated. The Re vs W junction develops about 15 mv at 1000°C and may be usable up to 2600°C. Re vsMo develops about 17 mv at 1000°C; the thermoelectric power is low above 1600°C. The outputs of Re vs W‐30Re and Re vs Mo‐50Re couples are low and change signs at about 1200 and 1800°C, respectively. The calculated outputs of W vs W‐30Re and Movs Mo‐50Re are high; the W vs W‐30Re output is nearly linear over a wide range in temperature, and the thermocouple should be useful to about 2600°C. All of these couples must be used in vacuum or in neutral or reducing atmospheres.
30(1959); http://dx.doi.org/10.1063/1.1716477View Description Hide Description
A description of an instrument for measuring C14, percent CO2, and C14 specific activity in the breath of human subjects is presented. Ionization chamber assay for the C14 is used. The design parameters of radioactivity sensitivity and response time are discussed. For simple carbon‐14 metabolites some 1 to 10 μC are required for an eight‐hour respiration analysis with this instrument.
30(1959); http://dx.doi.org/10.1063/1.1716478View Description Hide Description
An adiabatic calorimeter designed primarily for measurements on bulk metal samples is described. Details of the calorimeter design and operation are given. Experimental problems associated with precise high‐temperature measurements are emphasized. Measurements from room temperature to 1000°C have been made and include determinations of specific heats, heats of transformation, and heats of solution. Representative data on pure nickel are shown with reported accuracy of ±0.5%.
30(1959); http://dx.doi.org/10.1063/1.1716479View Description Hide Description
Gas flow through capillaries obstructed by wire inserts was investigated for ratios of core to capillary diameters (B/A's) of 0.08 to 0.9. For a given core‐capillary combination, laminar and turbulent as well as an intermediate region are well defined. Deviations from Poiseuille flow for the range of B/A's are presented in a working curve, which will give flow rates for laminar flow correct to from 5 to 10%.
The pressure drop vsflow curves for the intermediate and turbulent flow regions are reasonably reproducible. The use of the cored capillary for very small leak rates looks especially attractive because, with large B/A's such that the maximum crescent clearance is less than 0.25 mm, the onset of turbulence is postponed to much higher pressure drops.