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, and transfer operations on-site, including logistics, safety, and vendor relationships.

Maintain all cryogenic hardware: cryopumps, compressors, cold heads (Gifford-McMahon or Pulse Tube), transfer lines, pressure-relief systems, and monitoring instrumentation.

Develop and implement a preventive-maintenance program for all cryogenic and vacuum equipment aligned with the facility shot schedule.

Train facility operations staff on cryogenic safety procedures and emergency response.

Diagnostics & Instrumentation

Specify, install, and maintain cryogenic instrumentation: Cernox or PT-100 temperature sensors at multiple stages, capacitance manometers, ionization gauges, residual gas analyzers (RGA), and pressure transducers.

Integrate cryogenic-system monitoring into the facility control and interlock system.

Safety & Compliance

Author and enforce cryogenic safety procedures, including ODH assessments, pressure-vessel requirements, LHe handling, and cold-burn precautions, in compliance with applicable U.S. codes.

Perform pressure-vessel and cryostat inspection and documentation per applicable ASME/CSA standards.

Minimum Qualifications

B.Sc. or M.Sc. in Physics, Mechanical Engineering, Engineering Physics, or Chemical Engineering with demonstrated cryogenics specialization.

2+ years of hands-on experience designing, operating, or maintaining cryogenic systems at liquid-helium temperatures (4 K) in a research or industrial facility.

Proficiency with cryopump systems including sizing, installation, and regeneration cycles.

Strong working knowledge of vacuum science and technology: pumping speed, conductance, outgassing, leak detection using He mass spectrometry, residual gas analysis, and pressure measurement.

Experience designing or operating liquid-helium dewars, cryostats, and VJ transfer lines.

Familiarity with cryogenic instrumentation including thermometry, pressure, flow, and liquid-level measurement from 4 K to 300 K.

Preferred Qualifications

Experience with fusion energy, pulsed power, or particle-accelerator cryogenic systems, particularly high-voltage-isolated cryogenic assemblies.