The Pelletron is pressurized with SF6 insulating gas and includes a recirculation system for the SF6. The size of the Pelletron is dependent on the terminal voltage of the system, the type of column/support structure, and whether it is a tandem or single-ended accelerator.
NEC designs the Pelletron and recirculation systems to conform to local or international codes, including ASME, CE, and additional standards. The pressure vessel is typically rated at 125 psig internal pressure and 15 psig external pressure, designed to be filled with about 80 psig pressure of SF6 as an insulating gas. Ports are incorporated into the pressure vessel for components such as a generating voltmeter, a capacitive pickup, electrical feedthroughs, and windows.
There are typically two sections of the tank – the bell section and the end plate. The accelerator column is attached to the end plate and can be removed from the bell section for maintenance.
On accelerator systems over 4MV, maintenance is performed inside the accelerator tank by using manways and, in some cases, moving platforms. This allows a smaller footprint by removing the need to pull the accelerator column out of the pressure vessel.