Principal RF Systems Engineer

Commonwealth Fusion Systems LLC; Massachusetts; On-site; USD 150,000 - 225,000; Full time

Benefits offered by this job

Equity

Holidays

Flexible vacation

Sick days

Parental leave

Health insurance

Dental insurance

Vision insurance

401(k) matching

Growth opportunities

Team building

Job summary

Commonwealth Fusion Systems LLC is seeking a Principal RF Systems Engineer to architect and hands-on develop the SPARC RF plant, integrating high-power RF sources, amplifiers, and transmission networks to heat plasma and achieve net energy. You will lead system-level decisions, collaborate with senior teams, and drive robust electronics ecosystems for scalable fusion power hardware.

The role requires 15+ years in high-power RF, radar, accelerators, or related power electronics, with expertise in

Qualifications

• 15+ years of hands-on experience in high-power RF systems, radar, accelerators, or heavy industrial power electronics.
• Proven intuition for high-power RF environments, including measuring forward/reflected power and diagnosing RF arcs.
• Expertise in RF circuit design and EMI/EMC mitigation for extreme high-noise environments.
• Strong proficiency in RF/Microwave simulation tools (CST, HFSS) to validate architectural decisions.

Responsibilities

• Shape end-to-end RF plant architecture for tokamaks, coordinating with senior engineers to ensure seamless interaction between RF sources, matching networks, and plasma load.
• Guide the electronics integration, emphasizing solid-state amplifier technology and reliable power supplies.
• Spearhead instrumentation and control design for RF signal detection, measurement circuits, and embedded controllers interfacing with data systems.
• Tame high-power delivery by designing and optimizing large-diameter coax lines and impedance-matching networks.
• Mentor junior engineers on the floor, lead commissioning, and troubleshoot complex hardware discrepancies.

Skills

RF systems engineering

High-power RF

EMI/EMC mitigation

RF circuit design (Altium)

RF/Microwave simulation (CST/HFSS)

Embedded controllers

Power electronics

Education

Bachelor's degree in Electrical Engineering or Physics

Master's or Ph.D. preferred

Tools

Altium

CST

HFSS

Job description

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, suppliers, and many others to build the energy industry of the future.

We’re in the best position to make it happen. Since 2018, we’ve raised $4 billion of capital, making us the largest and leading 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 Principal RF Systems Engineer

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 Principal RF Systems Engineer to play a pivotal role in building the most powerful RF plant in the world.

At this level, you are a highly influential architect of the system. You will help drive the high-level technical direction while remaining deeply hands‑on, taking a central role in the integration of high-power electronics, solid‑state amplification, and complex transmission networks to ensure SPARC achieves net energy.

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

• Overview of the SPARC tokamak
• Physics basis for the ICRF system of the SPARC tokamak

What you'll do:

• Shape System Architecture: Play a critical role in the end-to-end design and integration strategy for RF plants for tokamaks, collaborating with other senior engineers to ensure seamless interaction between RF sources, matching networks, and the dynamic plasma load
• Guide Solid-State & Electronics Integration: Act as a key driver in the architecture and design of the electronics ecosystems required to integrate massive, distributed RF systems, with a heavy emphasis on solid‑state amplifier technology and associated power supplies
• Spearhead Instrumentation & Control (I&C): Take the initiative in designing and integrating advanced RF signal detection, measurement circuits, and embedded digital controllers that interface seamlessly with SPARC’s central data collection systems
• Tame High-Power Delivery: Serve as a central figure in the hands‑on design, integration, and optimization of critical high-power transmission components, specifically large-diameter coax lines and dynamic impedance matching networks
• Hands‑on Technical Mentorship: Act as a senior technical authority on the floor. You will be actively involved in commissioning equipment, troubleshooting the most complex system‑level hardware discrepancies, and organically mentoring junior engineers to elevate the entire RF team’s capabilities

What we’re looking for:

• Education: Bachelor’s degree in Electrical Engineering, Physics, or a related field (Master’s or Ph.D. strongly preferred for this level)
• Experience: 15+ years of hands‑on experience in high‑power RF systems, radar, particle accelerators, or heavy industrial power electronics
• RF Fundamentals Expertise: Proven intuition for high‑power RF environments, specifically hands‑on experience measuring forward and reflected RF power, diagnosing RF arcs, and designing the timing and electronics to mitigate them
• Electronics & Design: Exceptional skills in RF circuit and electronics design (Altium or similar) specifically geared toward instrumentation, sensing, control, and system integration. Experience in EMI/EMC mitigation to ensure sensitive timing and RF detection circuits operate reliably within extreme high‑power, high‑noise environments
• Advanced Simulation: High proficiency in RF/Microwave simulation software (CST, HFSS, etc.) to validate architectural decisions before physical integration
• Cross-Disciplinary Fluency: A strong systems‑level understanding of modern high-performance embedded digital controllers, high speed communications, and fundamentals of mechanical/thermal design to interface effectively with cross‑functional teams

Must-have Requirements:

• Perform activities such as stooping, 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

$150,000 - $225,000 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.