Filament
A heated filament is used to boil off seed electrons to assist with breakdown. It can be biased to emit an electron current. Bias supply is on top of middle rack in L209, typically maximum of 10 mA emission. Filament heating supply built into pump duct rack, typically variac set to 50%. Extra filament wire and large bolt with proper diameter / thread pitch for winding replacement filament stored in S235.
