Volume 15, Issue 10, 01 October 1944
Index of content:
15(1944); http://dx.doi.org/10.1063/1.1707374View Description Hide Description
A new type of vacuum tube is described in which a flat radial beam of electrons in a cylindrical structure may be made to rotate about the axis. Features of the tube are the absence of an internal focusing structure and resultant simplicity of design, its small size, its low voltages, and its high beam currents. The focusing of the beams and their directional control are accomplished by a magnetic field.
15(1944); http://dx.doi.org/10.1063/1.1707377View Description Hide Description
In this paper sixty‐eight nuclear monokinetic electron sources are tabulated. These sources are obtained by producing designated artificial radioactive elements. The voltage of the electrons emitted in the lowest energy group is 17 kev and that in the highest is 578 kev. Applications seem possible in special radio tubes and for certain experiments with electron microscopes and electron diffraction.
15(1944); http://dx.doi.org/10.1063/1.1707378View Description Hide Description
In electron flow, the net electronic charge may be neutralized by positive ions. In this case, for a given geometry there is a limiting current beyond which homogeneous flow is unstable. This limiting current is evaluated for flow normal to parallel plane equipotentials and for flow filling a conducting tube and constrained to motion parallel to the axis. For parallel planes at a potential V 0 volts and spaced a distance L cm apart, the limiting current density in amperes/cm2 is. For a long conducting tube the limiting current is . These limiting currents are roughly 6 times as great as in the absence of ions.
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