John P. Blewett

Magnetic Field Configurations Due to Air Core Coils

The field configurations around a circular loop of wire bearing current are discussed, and a tabulation is presented for the field component parallel to the axis of the loop. Formulae are derived for the current distribution which must obtain in cylindrical and ellipsoidal coils in order that the field inside be uniform. Several special cases are noted. The energy storage in the return flux is evaluated in each case.

Propagation of Electromagnetic Waves in a Space Charge Rotating in a Magnetic Field

A theoretical discussion is presented of the transmission of electromagnetic waves of the symmetrical, transverse magnetic type by a space charge of uniform density, rotating under the influence of a uniform magnetic field. It is shown that the space charge presents to the wave an effective dielectric constant less than unity. By appropriate choices of magnetic field, the dielectric constant can be reduced to zero and can even become negative, so that the wave undergoes attenuation as it passes through the space charge. Experiments are described on the control of the propagation constants of 470‐megacycle waves by variation of the dielectric constant of the rotating space charge medium. The results obtained are in agreement with the theoretical predictions.

Magnetic Operation of Chemical Balances

Two types of balance are described for measuring small weights by application of a magnetic force in place of the usual system of calibrated weights. One method is applied to an analytic balance, the other to a vacuum balance.

Design of an Air Core Synchrotron

The analysis of the preceding paper is applied to the problem of designing a synchrotron in which the magnetic fields are produced by air core coils. The air core synchrotron is shown to be practical and to present certain advantages.