Cryogenic Systems Engineer

ABOUT FUSE We are building one of the most potentially consequential companies of the century. Our mission is to accelerate the world's transition to fusion energy while safeguarding humankind. This is not a normal company. This is not a normal job. We are committed for the long term to win. ABOUT THE ROLE Fuse is constructing Z-Star, a next-generation pulsed-power facility. Z-Star requires two deeply integrated cryogenic systems: a high-vacuum cryopumping system and a 4 K target/liner cryogenic cooling system. As the Cryogenic Systems Engineer, you'll design, commission, operate, and maintain both systems and serve as the facility's resident expert in cryogenic and vacuum science. CORE RESPONSIBILITIES Cryopump System Design & Operations - Design, procure, install, and commission the multi-stage vacuum system for the Z-Star chamber, including turbomolecular roughing pumps, cryopump arrays, and associated gate valves, interlocks, and controls. - Define cryopump sizing, placement, and regeneration schedules to meet target base pressure and shot-repetition-rate requirements. - Develop and maintain vacuum protocols including chamber venting, backfilling with inert gas, and controlled pump-down procedures compatible with shot operations. - Monitor and trend vacuum performance; diagnose and resolve outgassing sources, virtual leaks, and pump degradation. 4 K Target Cryogenic System - Design and commission the liquid helium cryostat and cryogenic delivery system for liner/target cooling, including vacuum-jacketed transfer lines, LHe reservoir management, and temperature-control instrumentation. - Develop procedures for target loading, cool-down, hold time at 4 K, and rapid warm-up following a shot. - Characterize and minimize cryogenic heat loads from radiation, conduction, and parasitic pathways to maintain stable 4 K conditions through the target preparation window. Cryogenic Infrastructure Management - Manage liquid helium and liquid nitrogen supply, storage dewars, an