Ion Cyclotron Resonant Heating slot antenna for the Tandem Mirror Experiment-Upgrade

The Ion Cyclotron Resonant Heating (ICRH) slot antenna has been a part of the ion and electron plasma heating system in the central cell region of the Tandem Mirror Experiment-Upgrade (TMX-U). This paper presents the mechanical design and arrangement of the antenna, coax feed lines, feedthroughs, and matching network for the slot antenna. This antenna is a slotted, hollow tube that completely surrounds and conforms to the plasma shape in the east end of the central cell region. The shell is made of copper sheet with 1-inch-diameter copper tubing leads. The three feed lines are coax pipe with 3-inch inner and 5-inch outer conductors. The three feedthroughs are a triaxial design for high radio frequency (RF) voltages and currents of 30 kV and 700 amps peak, respectively. The capacitor matching network is external to the vacuum chamber. It consists of two remotely controllable capacitors, variable from less than 100 to 1800 pF, and six 1000-pF fixed capacitors that can also be remotely switched into and out of the circuit. The antenna has been operated to power levels in excess of 300 kW