I did construct a small tesla coil once. I powered it with a twelve volt lead-acid battery and used a vibrating aquarium air pump to make and break
the battery power going to the automotive coil primary. They call it a kicker coil arrangement. This charged the capacitor of the primary circuit. Sparks off the secondary were like half an inch long, but a good 2 inch plasma when a clear light bulb was connected. When my ignition burner transformer arrived
in the mail, it was so powerful that I never looked back to the kicker setup.
Never heard of radiant energy back then.