A system may comprise a cathode, a target, one or more switches, and a conductive element. The cathode may be configured and arranged to generate an electron beam, and the target may be configured and arranged to emit radiation when electrons in the electron beam impact the target after being accelerated by an energy source. The one or more switches may be configured and arranged to apply either a first voltage or a second voltage from a power supply between the cathode and the target. The conductive element may be disposed between the cathode and the target so as to inhibit the electron beam generated by the cathode from reaching the target when a signal is applied to the conductive element.