Selective generation of radiation at multiple energy levels

A method, comprising:

• (a) applying a first voltage between a first cathode that generates a first electron beam and a first target that emits radiation when electrons in the first electron beam impact the first target after being accelerated by an energy source;
• (b) applying a second voltage, which is different than the first voltage, between the first cathode and the first target;
• and
• (c) applying a first signal to a first conductor disposed between the first cathode and the first target so as to inhibit the first electron beam generated by the first cathode from reaching the first target,
• wherein the step (c) is performed during portions of periods during which step (a) is performed.

A system, comprising:

• a cathode configured and arranged to generate an electron beam;
• a target configured and arranged to emit radiation when electrons in the electron beam impact the target after being accelerated by a voltage difference between the cathode and the target;
• means for applying either a first voltage or a second voltage, which is different than the first voltage, between the cathode and the target;
• means for inhibiting the electron beam generated by the cathode from reaching the target;
• and
• a controller configured to control whether the means for applying applies either the first voltage or the second voltage between the cathode and the target, and to control whether the means for inhibiting inhibits the electron beam generated by the cathode from reaching the target.