The LLNL HFTF-a flexible superconducting test facility for fusion magnet development

A description is given of the High-Field Test Facility providing the capabilities needed to develop the superconducting magnet systems of next-generation fusion machines. The magnet system of the HFTF comprises six superconducting solenoids, a quench detection system and energy dump circuitry. The superconducting coil set in HFTF has been operated successfully; the magnet system was designed to be fully cryostable and has never quenched. A new cryostat for the coil set allows the magnet system to remain cold indefinitely so that the system is available on short notice to provide high fields (about 11 T) inside a reasonably large test volume (0.3-m diam). The test volume is isolated physically and thermally from the coil volume allowing test articles to be inserted and removed without disturbing the coil cryogenic volume. The separate test volume also allows reduced-temperature operation without the expense and complication of subcooling the entire coil set (about 20-t cold mass).