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Salary
$90k – $145k per year
Location
In office (Devens)
Seniority
Senior · 5+ years exp
Employment
Full-Time

Confirmed on the employer's own hiring board on Sep 25, 2026. First seen by Alion on Sep 23, 2026. Commonwealth Fusion Systems scores A on the Alion truth index.

Overview
Company
Impact
Profile match
Commonwealth Fusion Systems is a commercial fusion energy company headquartered in Devens, Massachusetts, and founded in 2018. The firm specializes in the development of high-temperature superconducting magnets and compact tokamak devices, specifically the SPARC net-energy machine and the ARC commercial power plant. It operates through a strategic partnership with the Massachusetts Institute of Technology and focuses on scaling fusion technology to provide carbon-free, baseload power to global energy markets.

Join the power movement as an Mechanical Engineer, RF Systems

SPARC sustains fusion reactions by feeding >25MW of 120MHz RF power into the tokamak to heat the plasma to 100 million Kelvin. We need a Mechanical Engineer to design the critical physical infrastructure that routes this massive power, from coax transmission lines that span the entire plant to the intricate cooling plates required for high-power electronics.

At this level, you will own the physical design and integration of robust mechanical systems, translating requirements into manufacturing-ready hardware. You will design everything from large-scale utility interfaces and custom bellows to sheet metal parts and custom heat sinks, taking designs from ideation and CAD modeling through fabrication and direct plant integration.

For more information on the SPARC RF plant, see the SPARC journal papers here:

What you'll do:

    • Design specialized RF Heating plant components working closely with RF Engineers. These include large-diameter coaxial transmission lines and devices such as stub tuners and RF testing loads
    • Decompose high-level system requirements into actionable mechanical specifications, owning the mechanical designs for the RF Heating system
    • Collaborate daily with a dedicated CAD drafting team, providing clear guidance to detail, rigorously reviews, and releases
    • Partner cross-functionally with RF engineers, electronics engineers, process engineers, and other disciplines
    • Architect thermal management solutions by integrating complex water and air cooling loops directly into high-power electronics enclosures and plant systems
    • Develop large sheet metal components, precise mounting hardware for custom printed circuit board assemblies, cold plates, and more
    • Perform structural loads analysis and thermal analyses to ensure design viability

What we’re looking for:

  • Bachelor’s degree in Mechanical Engineering, Physics, or a related field
  • 5+ years of hands-on mechanical design experience in industrial, heavy machinery, high-power electronics, electric vehicle, or aerospace environments
  • Demonstrated experience as the primary creator and owner of mechanical design architectures, operating as a core design engineer
  • Direct experience performing structural loads analysis and thermal analyses to validate mechanical designs
  • High proficiency in 3D CAD software and creating detailed manufacturing drawings utilizing GD&T standards
  • Possess a strong fundamental understanding of heat transfer, structural mechanics, and fluid dynamics

Bonus points for:

  • Experience using Siemens NX for 3D modeling and Teamcenter for product lifecycle management and drawing release workflows
  • Background decomposing complex system requirements into clear mechanical hardware specifications
  • Experience designing large-scale pipe routing, coaxial transmission lines, flanges, bellows, or active water and air cooling systems
  • Experience with complex electronics assemblies and the thermal management of such assemblies
  • Deep familiarity with sheet metal fabrication processes, machining capabilities, and communicating directly with contract manufacturers

Must-have Requirements:

  • Ability to lift up to 50lbs
  • Perform activities such as stooping, climbing, standing, typing or sitting for extended periods of time
  • Willingness to travel or work required nights/weekends/on-call occasionally
  • Work in a facility that contains industrial hazards including heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, high current, pressure systems, and cryogenics
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