Fusion Science and Technology / Volume 54 / Number 4 / November 2008 / Pages 946-961
The original Translation, Confinement, Sustainment (TCS) experiment was upgraded [TCS Upgrade (TCSU)] to provide an ultrahigh vacuum (UHV) environment with modern discharge cleaning and wall-coating technologies. This has allowed rotating magnetic field formed field reversed configuration plasma temperatures to increase from the TCS radiation-dominated tens of electron volts to >200 eV (Te + Ti), and FRC magnetic fields to double. The improvements are directly attributable to reduced impurity levels and reduced plasma recycling losses. Some of the technologies utilized to achieve these results included replacing O-rings with wire and conflat seals; developing high-temperature, differentially pumped, elastomeric seals for bonding extremely large quartz tubes (needed for rapid field penetration) to the stainless steel vacuum chambers; and using heater blankets for vacuum baking. Extensive testing using electron microprobe and various spectroscopic techniques was performed to establish appropriate UHV cleaning and handling methods.