On the Theory of the Electrostatic Beta-Particle Energy Spectrograph. III

A study is made of the focusing action of the electrostatic analyzer (the electrostatic field between two concentric cylindrical-segment electrodes) on particles having relativistic speeds. A dependence of focal length on particle speed is derived; and its effects on the use of the analyzer for continuous spectra is examined. This study is an extension of a previous one of the same title in that: the central angle subtended by the electrode segments need not be 127° 27′, and the region of (relativistic speed) validity is somewhat greater.