The present invention is an RF cavity for accelerating electrons in imaging applications such as x-ray tubes and CT applications. An RF cavity having electron emitters placed therein accelerates the electrons across the cavity. The geometric shape of the cavity determines the electromagnetic modes that are employed for the acceleration of electrons. The fast electrons are used to generate x-rays by interacting with a target, either a solid or a liquid target. The electron accelerator may be used in an arc source for a stationary computed tomography application, in an x-ray tube, as a booster for an electron gun, and other imaging applications.