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.