Electron Acceleration by Inhomogeneous Radio-Frequency Field

Abstract

An investigation is made on the electron acceleration by a non-linear force due to the inhomogeneity of an electrostatic R.F. field; the electric field component is almost along the y direction and its inhomogeneity is in the x direction and the acceleration toward the x direction is investigated. A survey of a simple calculation indicates that the non-linear force consists of the zero frequency, fundamental and second harmonics components of the R.F. field, and that the electron acceleration energy is large when electrons begin to interact with the R.F. field whose amplitude is at its maximum value. In the experiment, a large increment of the electron current extracted from the thermionic cathode is observed by appling the R.F. field. Also it turns out that the electron acceleration is due to the non-linear force and that moreover some electrons are accelerated to an energy equivalent to the applied R.F. field voltage i.e. 12 V if the field frequency is higher than 40 MHz.The experimental result concerning the initial condition, i.e. the initial phase of the R.F. field agrees with that of the calculation qualitatively.