Principal Capacitor Engineer

About Helion We are a fusion power company based in Everett, WA, with the mission to build the world's first fusion power plant, enabling a future with unlimited clean electricity. Our vision is a world with clean, reliable, and affordable energy for everyone. Since Helion's founding in 2013, we have raised over $1 billion from long-time investors such as Sam Altman, Mithril, and Capricorn Investment Group as well as new investors SoftBank and Lightspeed to propel us forward. Our last prototype, Trenta, completed 10,000 high-power pulses and reached plasma temperatures of 100 million degrees Celsius (9 keV). We are now operating Polaris, our next prototype on the path to the world's first fusion power plant. This is a pivotal time to join Helion. You will tackle real-world challenges with a team that prizes urgency, rigor, ownership, and a commitment to delivering hard truths – values essential to achieving what no one has before. Together, we will change the future of energy, because the world can't wait. What You Will Be Doing As a Principal Capacitor Design Engineer at Helion, you will lead the design, development, and scaling of custom high-voltage, pulsed-power capacitors that are core to Helion’s fusion generators. You will own capacitor architecture from first principles through high-volume manufacturing, driving breakthroughs in energy density, reliability, and cost. You will provide deep technical leadership to engineering, manufacturing, and production teams as Helion transitions from prototype builds to the world’s first fusion power plant. You will provide technical leadership, organize work, set priorities, and advance Helion’s mission to deliver clean power in a reliable and cost-effective manner. This is an onsite role that reports directly to Senior Manager of Mechanical Engineering at our Everett, WA, office. You Will - Lead the full lifecycle of capacitor development—requirements definition, physics-based modeling, internal design, materials selection, prototyping, testing, and scaling into high-throughput manufacturing - Drive the development of low-inductance, high-reliability pulsed capacitors capable of <1 ms, multi-megampere operation, while optimizing for energy density, manufacturability, cost, and lifetime performance - Define critical material specifications, qualification criteria, manufacturing processes, and high-voltage pulsed-power test methods for Helion’s custom capacitor systems - Provide technical leadership and mentorship to engineers, technicians, and assemblers, guiding architecture decisions, test interpretation, and iterative design improvements - Lead failure analysis, lifetime modeling, thermal analysis, and root-cause investigations to strengthen capacitor reliability and production consistency - Partner closely with pulsed-power electrical engineers to align capacitor design with system-level circuit performance targets - Direct the testing, characterization, and evaluation of internally built and supplier-provided capacitors; analyze data and drive continuous improvement with internal teams and external vendors - Own long-term capacitor technology strategy, identifying opportunities to reduce risk, introduce advanced materials, and integrate emerging capacitor technologies Required Skills - Bachelor’s or Master’s degree in Engineering or Physics - 15+ years of deep experience in pulsed-power capacitor design and manufacturing, including internal construction, low-inductance layout, simulation, materials processing, fabrication, high-voltage testing, and lifetime prediction - Demonstrated expertise in dielectric physics: electrical/thermal aging, breakdown behavior, complex permittivity, frequency and temperature dependence, and high-field effects - Proven ability to lead capacitor design from concept through high-volume production, including scaling throughput and establishing robust manufacturing processes - Hands-on experience with rapid prototyping, iterative testing, and high-e