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Feb 1940

Volume 11, Issue 2, pp. 47-78

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An Electrical Method for Compounding Sine Functions

Louis R. Maxwell

Rev. Sci. Instrum. 11, 47 (1940); http://dx.doi.org/10.1063/1.1751625 (8 pages) | Cited 1 time

Online Publication Date: 27 December 2004

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An electrical device is described for evaluating the series ΣAi sin aix. For each term in the series there is constructed one compounding element composed of three coils; a long solenoid acting as a primary (60‐cycle a.c.) within which are mounted two short secondary coils, one a rotor (order of 1/5 r.p.m.) and the other a stator. The mutual inductance between the primary and rotor varies as the sine of the angle aix of rotation while the primary current is held proportional to Ai. The vector sum of the peak voltages induced in the rotor and stator varies about a constant value proportional to Ai sin aix. Thus the variations of the resultant voltage from all of the elements about a constant value are proportional to the sum of the series. A record of the sum is made on photographic paper by means of a vacuum tube voltmeter circuit. Satisfactory tests have been made on a machine containing two elements. The application to structure determinations of gas molecules by electron diffraction is presented.

Generating Voltmeter for Pressure‐Insulated High Voltage Sources

J. G. Trump, F. J. Safford, and R. J. Van de Graaff

Rev. Sci. Instrum. 11, 54 (1940); http://dx.doi.org/10.1063/1.1751641 (3 pages) | Cited 15 times

Online Publication Date: 27 December 2004

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A description is given of a generating voltmeter suitable for a voltage source insulated by compressed gas. The calibration is linear and the design simple in that neither amplification nor mechanical commutation is required. The paper discusses the principle of operation, the construction, calibration, and sensitivity, and tests indicating that the influence of corona on the voltage readings is negligible.

The Production of Annular Magnetic Fields of Great Uniformity

Michael Ference, A. E. Shaw, and R. J. Stephenson

Rev. Sci. Instrum. 11, 57 (1940); http://dx.doi.org/10.1063/1.1751642 (6 pages) | Cited 12 times

Online Publication Date: 27 December 2004

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In the magnetic focusing of electron or ion beams, it is important to secure magnetic fields which possess homogeneity over the region in space traversed by the beam. Helmholtz coils, frequently used for this purpose, provide the desired uniformity of field only for a limited region coaxial with the coils, but for regions off the axis in the median plane, the magnetic field is not uniform. It has been shown theoretically and verified experimentally that in order to obtain the necessary uniformity off the axis in the median plane, the axial separation of the coils must be diminished; this separation depends upon the region in which the uniformity is desired. A pair of coils whose separation may be varied has been constructed of mean radius 30.712 cm, each having 900 turns and an approximate square cross section of windings of side 6.856 cm. The field due to the coils has been explored off the axis in the median plane using a standard coil and magnetometer. The measurements reveal that the uniformity produced with the new separation is vastly superior to that which results from the usual Helmholtz separation.

Two Small Portable Geiger‐Müller Counters

Robert B. Taft

Rev. Sci. Instrum. 11, 63 (1940); http://dx.doi.org/10.1063/1.1751643 (2 pages)

Online Publication Date: 27 December 2004

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The Use of Electrets in Electrical Instruments

Andrew Gemant

Rev. Sci. Instrum. 11, 65 (1940); http://dx.doi.org/10.1063/1.1751644 (7 pages) | Cited 9 times

Online Publication Date: 27 December 2004

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An electret is a permanently electrically polarized material and exhibits an electric field near its free surface which keeps undiminished for years. It is possible to utilize this field in electrical appliances. Experiments and devices on this line are described in the following paper.

Hormone Studies with the Ultracentrifuge III. An Application of Toepler's Schlieren Method to the Analytical Ultracentrifuge

James A. Chiles and Aura E. Severinghaus

Rev. Sci. Instrum. 11, 71 (1940); http://dx.doi.org/10.1063/1.1751645 (6 pages) | Cited 1 time

Online Publication Date: 27 December 2004

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The Preparation of Thin Films of Uranium and Thorium by Cathode Sputtering

C. C. Van Voorhis

Rev. Sci. Instrum. 11, 77 (1940); http://dx.doi.org/10.1063/1.1751646 (1 page) | Cited 1 time

Online Publication Date: 27 December 2004

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Excitation of Active Nitrogen

Harold P. Knauss and Allen E. Murray

Rev. Sci. Instrum. 11, 78 (1940); http://dx.doi.org/10.1063/1.1751647 (1 page)

Online Publication Date: 27 December 2004

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