As for powering it - I'm sure it could be accomplished on a generic platform like the B-52 or a modified commercial liner - something capable of
high-altitude flight and long loiter times, while carrying a payload and having substantial room for an antenna.
You're just powering a short pulse - your most critical part will be a storage bank of capacitors (or possibly a superconductor). That relative
technology is advancing quite well - so it will not be a problem by time the craft were to have its design finalized and enter production.
Honestly? I'd rather have a kinetic interceptor or some kind of plasma-yield weapon.