High-Power Lasers Require High Voltage
These are the guts of the high voltage power supply, which provides juice to the electron gun. When the system is fully assembled, the six-foot-high metallic coils will be sealed in a pressurized chamber filled with a gas called sulfur hexafluoride. The massive amounts of power--hundreds of kilovolts--that the coils produce can cause arc discharges, when energy is discharged into the air. The sulfur hexafluoride prevents that from happening because it doesn't conduct electricity as well as air does.
Image: Jefferson Laboratory