Source for intra-pulse multi-energy X-ray cargo inspection

A method for generating a multiple-energy X-ray pulse, the method comprising:

• generating a beam of electrons with an electron gun, wherein a temporal profile of the electron gun is characterized by at least two distinct levels of the amplitude of electron beam In;
• modulating the beam of electrons prior to injection into an accelerating structure to achieve at least a first specified beam current amplitude and a first specified beam current temporal profile, and a second specified beam current amplitude and a second specified beam current temporal profile, wherein the beam of electrons is characterized by an electron beam pulse duration and the accelerating structure includes a standing wave resonator;
• applying to the accelerating structure a radio frequency field with a specified RF field amplitude and a specified RF temporal profile characterized by an RF pulse duration;
• injecting the beam of electrons at a first specified beam current amplitude and then at the second specified beam current amplitude after a specified delay, in such a manner as to achieve at least two distinct endpoint energies of electrons accelerated within the accelerating structure during a course of a single RF-pulse;
• optimizing a coupling coefficient between an RF source and the accelerating structure so as to achieve zero RF power reflection at the first specified beam current amplitude or the second specified beam current amplitude, wherein the RF source provides a constant level of RF-power and wherein the coupling coefficient of accelerating resonator βo is chosen to be optimal at a first level of beam current I1;
• accelerating the beam of electrons with the radio frequency field within the accelerating structure to produce accelerated electrons;
• and
• impinging the accelerated electrons upon a target for generating X-rays by Bremsstrahlung.