Use of Polycarbonate Vacuum Vessels in High-Temperature Fusion-Plasma Research

Magnetic fusion energy (MFE) research requires ultrahigh-vacuum conditions, primarily to reduce plasma contamination by impurities. For radiofrequency (RF)-heated plasmas, a great benefit may accrue from a nonconducting vacuum vessel, allowing external RF antennas to avoid the complications and cost of internal antennas and high-voltage high-current feedthroughs. In this paper we describe these and other criteria, e.g., safety, design flexibility, structural integrity, access, outgassing, transparency, and fabrication techniques that led to the selection and use of 25.4-cm OD, 1.6-cm wall polycarbonate pipe as the main vacuum vessel for an MFE research device whose plasmas are expected to reach keV energies for durations exceeding 0.1 s.