Diagnostician

Commonwealth Fusion Systems

Devens, United States

November 22, 2025

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Diagnostician

Devens, MA
SPARC Tokamak Team – Tokamak Systems /
Full-time /
On-site
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 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 Diagnostician

Commonwealth Fusion Systems is assembling the high-field SPARC tokamak, which aims to be the first magnetic fusion device to achieve net fusion energy, and is predicted to be able to achieve high gain and fusion power up to 140MW.  We are completing the design and beginning the assembly and installation of diagnostic systems that will be used to control the plasma and deliver the scientific data necessary to complete the design of ARC. These include approximately 40 sub-systems covering magnetics, interferometry, neutral pressure, x-ray to visible spectroscopy, camera imaging, bolometry, neutrons, Thomson scattering, electron cyclotron emission, reflectometry, Langmuir probes and structural temperature and strain sensing.  A more detailed overview can be found at: .  
 
CFS is looking to grow the SPARC team in order to complete back-end design and move diagnostics through fabrication, assembly, commissioning and utilization. Presently the diagnostics team has enough expertise to support all major diagnostic systems, but we are looking to add a generalist who has experience in multiple diagnostics to ensure our team can deliver measurements on SPARC’s fast timeline. Candidates will work as part of an integrated diagnostic team along with MIT-PSFC partners and fusion community collaborators from around the world to demonstrate net energy from a tokamak for the first time. CFS encourages applications from both senior and early career fusion scientists and those interested in cross-industry career changers to help us build a diverse team to meet our mission goals.

What you'll do:

    • Shepherd SPARC diagnostic sub-systems through final design, working with a team of scientists, designers, analysts and engineers
    • Integrate technical input from experts in the SPARC team to ensure diagnostic designs will be usable to achieve SPARC’s mission goals
    • Develop the diagnostic’s assembly, installation, calibration and commissioning plans to ensure SPARC is able to achieve first plasma on-schedule
    • Integrate the diagnostic into the plant-level and real-time plasma control systems
    • Participate in the testing and operation of diagnostic systems that balances learning how to operate SPARC with obtaining physics results as quickly as possible
    • Contribute to a strong safety culture
    • Collaborate with CFS designers and analysts as well as provide feedback to academic partners providing input to SPARC diagnostic designs

What we're looking for:

    • Bachelor’s degree in a relevant engineering field (mechanical, aerospace, civil or nuclear)
    • Participated in the design of a new or upgraded scientific instrument of the scale and complexity of those used in magnetically confined fusion
    • Demonstrated examples of using scientific instruments to support an operational and/or research mission
    • Developed software using Python, Matlab, C++ or equivalent for analysis of experimental data and automation of lab equipment
    • Relevant hands-on knowledge/skills specific to diagnostic systems listed in summary (e.g. vacuum systems, lasers, calibration sources, etc.)
    • Ability to understand concepts and tradeoffs that bridge engineering and physics

Bonus points for:

    • Participated in the design and implementation of a plasma diagnostic for a magnetically confined fusion experiment at University-scale or above

Must-have requirements:

    • Ability to occasionally lift up to 50 lbs
    • Perform activities such as climbing, typing, standing, 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

$110,000 - $185,000 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
•  12.5 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.
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