Patent ID: 8564224
Filing Date: 2013-10-22
Classification: H01J

Abstract:
1. An electron injector comprising: an electron source configured to emit electrons into the injector; a conducting grid situated close to the electron source; an RF accelerating/bunching cavity on an opposite side of the grid from the electron source the conducting grid being electrically connected to the RF accelerating/bunching cavity; a DC voltage source configured to bias the electron source at a small positive voltage with respect to the grid; a first RF drive configured to apply a first RF drive signal to a gap between the electron source and the grid, the applied first RF drive signal containing both the fundamental and at least one first selected harmonic RF frequency of an RF linac configured to receive electrons from the electron injector; and a second RF drive configured to apply a second RF drive signal to the accelerating/bunching cavity, the second RF drive signal containing both the fundamental and at least one second selected harmonic RF frequency of the RF linac, the second RF drive being electrically separate from the first RF drive so that at least one of an amplitude, a phase, and a harmonic of the second RF drive signal is controllable independently from an amplitude, phase, and a harmonic of the first RF drive signal; wherein the first RF drive signal is configured to cause the electrons emitted from the electron source to form electron bunches that travel through the grid into the accelerating/bunching cavity, the fundamental frequency causing the electron bunches to be configured to fill each accelerating RF bucket and the at least one first selected harmonic being configured to cause the electron bunches to have a desired first size; wherein the second RF drive signal is configured to accelerate and optimize the electron bunches for input into the RF linac, the at least one second selected harmonic being configured to cause the electron bunches to have a desired second side; and wherein the electron bunches are configured to fill each RF bucket of the linac as a result of the first and second applied RF drive signals.