Radiofrequency (RF) powered electron beam accelerators (or accelerator guides) have found wide usage in medical accelerators where the high energy electron beam is employed either directly for therapeutic purposes, or converted to generate x-rays for therapeutic and diagnostic purposes. The electron beam generated by an electron beam accelerator can also be used directly or indirectly to kill infectious pests, to sterilize objects, and to change physical properties of objects and materials. A further common use of electron beam accelerators is to perform radiographic testing and inspection of objects, such as containers for storing radioactive material, and concrete and steel structures.
The RF power for an electron beam accelerator is generally desired to be controlled, such that the beam energy from the accelerator can be delivered in a desired manner. It is common practice that the RF power be delivered to the accelerator as a series of short pulses, resulting in an electron beam output of a corresponding series of beam pulses. In some applications, it may be desirable that the accelerator be capable of generating beam energy pulses that vary between different energy levels, even on a pulse-by-pulse basis. However, existing systems may not be able to accomplish these objectives. Also, existing RF systems may not be able to control generated power such that power delivered to the accelerator can be varied quickly, e.g., in the order of milliseconds, between at least two power levels, which may be desirable in certain accelerator system applications.
Further, in existing systems, RF power provided by a power generator to an accelerator may be reflected back to the power generator. In many applications, it is desirable that such reflected RF power from the accelerator be controlled such that the frequency of a power generator will be “pulled” to the accelerator frequency, resulting in a stable operation of the power generator and the accelerator. If the reflected power is not controlled, the frequency of the power generator may be forced or “pulled” away from the operational frequency of the accelerator, resulting in failure of the accelerator to operate correctly.