Materials Test Engineer

About Commonwealth Fusion Systems: 

Commonwealth Fusion Systems is on a mission to deliver the urgent transition to fusion energy.

Combining decades of research, top talent, and new technologies, we’re designing and building commercially viable fusion power plants. And we're working with policymakers and suppliers to build the energy industry of the future. 

We’re in the best position to make it happen. Since 2018, we’ve raised nearly $3 billion in capital, making us the largest and leading private fusion company in the world.

Now we’re looking for more thinkers, doers, builders, and makers to join us. People who’ll bring new perspectives, solve tough problems, and thrive as part of a team. 

If that’s you and this role fits, we want to hear from you.

Join the power movement as a Materials Test Engineer

The Materials Department at CFS supports design engineers, supply chain, and manufacturing by guiding the selection of materials that meet design intent, executing testing, validation, and creation of design curves for materials, and conducting R&D to develop new materials and processes to enable fusion power deployment. The work is undertaken in support of delivering SPARC, the net energy tokamak under construction in Devens, MA, and ultimately in designing the ARC fusion power plant. These devices pose unique materials challenges including neutron fluxes produced by deuterium-tritium fusion, high heat and mechanical loads driven by high magnetic fields and cryogenic environment, molten salt coolant systems, and manufacturing challenges driven by components’ sizing and processes such as welding and other joining methods. To support this mission, the CFS Materials Department is seeking a Materials Test Engineer with experience in electrical characterization of insulating materials and sub-assemblies.

The ideal candidate has a background in materials engineering and experience with electrical characterization and testing. This role combines material design with functional testing, specifically focusing on the intersection of structural composites and their behavior under high voltage in extreme environments. They will actively engage in the entire lifecycle of a composite system, from identifying materials, selecting architectures and processes, to designing the custom high-voltage test stands required to validate them for fusion applications.

What you'll do:

• Evaluate, test and qualify materials and components for structural and functional applications within SPARC and ARC


• Own the execution and interpretation of electrical testing across coupon, sub-assembly, and component-level hardware, including dielectric, impulse, and Paschen testing


• Author and maintain materials test specifications, SOPs, and calibration practices for testing equipment and test stands.


• Review, interpret, and report materials property data into version-controlled databases, ensuring high quality and actionable recommendations for design teams


• Design, develop, and support custom electrical characterization test setups, instrumentation, and other custom test stands and test methods to meet evolving company needs


• Participate in the product design-build-test-learn cycles and retire technical risks by translating performance requirements into test plans and specifications


• Support the selection, development, and qualification of composite materials, and translate performance requirements into material property specifications


• Work closely with other CFS teams including:
  
  
  
  • Safety team to manage hazards in existing and new experiments
  
  
  • Adjacent R&D teams to optimally share pooled resources including equipment and personnel
  
  
  • Supply chain team to procure new equipment and materials
  
  
  • Test validation and analysis for data generated by materials test operators and R&D technicians
  
  

What we’re looking for:

• BS in Materials science engineering, mechanical engineering, applied physics or related field


• 5+ years of relevant experience


• Hands-on experience with process-structure-properties fundamentals of engineering composites (e.g., fiber-reinforced polymers)


• Experience in high-voltage and insulation-related testing, including the ability to troubleshoot test setups, instrumentation, and unexpected test behavior


• Experience with with Paschen curves, dielectric breakdown mechanisms, and the fundamentals of electricity


• Proficiency in CAD (e.g., NX, Solidworks) for the design of specialized electrical test fixtures and custom test stand components


• Experience managing multiple test requests and priorities independently, including resource estimation and schedule communication


• Strong ability to analyze complex datasets to identify trends and performance risks in material insulation systems


• Experience mentoring junior engineers or technicians on electrical testing methods and laboratory safety protocols


• Understanding process-structure-properties-performance principles for composites


• Able to think creatively and possess strong troubleshooting and problem solving skills


• Demonstrated ability to work effectively cross-functionally


• Excellent organizational skills including prioritization of multiple concurrent projects


• Ability to break down complex problems into smaller deliverables that add value

Bonus points for:

• Experience with electrical testing in extreme environments (high temperature, cryogenic, vacuum)


• Prior experience authoring internal material specifications or working with international materials standards (ASTM, ISO etc)


• Familiarity with the effects of radiation and plasma on the electrical performance of composite materials

Must-have Requirements:

• Extended activities such as typing, standing, and sitting


• Dedication to safety to mitigate hazards that may include heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, metallographic etchants and cryogenics


• Willingness to travel or work required nights/weekends/on-call occasionally

$90,000 - $145,000 a year

Salary range for this full-time position + equity + benefits . The actual salary will depend on level, location, qualifications, and experience. The range displayed on each job posting reflects new hire salaries for the position across all US locations. Benefits include:

• Competitive compensation with equity

• 13 Company-wide Holidays

• Flexible vacation days

• 10 sick days

• Generous parental leave policy

• Health, dental, and vision insurance

• 401(k) with employer matching

• Professional growth opportunities

• Team-building activities

#LI-Onsite

At CFS, we excel in fast-paced environments, driven by our values of integrity, execution, impact, and self-critique. As we grow, we’re eager to bring on mission-driven folks who offer diverse perspectives and fresh ways to tackle challenges.

We value diversity deeply and are proud to be an equal opportunity employer by choice. We consider all qualified applicants equally, regardless of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law.

This role requires compliance with U.S. laws concerning the export of controlled or protected technologies or information (collectively, “Export Control Laws"). Any offer of employment will be contingent on the need for compliance with such Export Control Laws.