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 Staff Mechanical Engineer We’re looking for a Staff Mechanical Engineer to join our R&D and equipment design team to help build the next generation of thin-film deposition technology. Serving as the "Second Chair" within our engineering group, you will be a high-impact technical leader who leads by example, solving highly complex, semi-ambiguous problems that influence the success of multiple teams. You will be responsible for the end-to-end design, integration, and implementation of advanced thermal vacuum deposition systems and complex R&D machinery. Operating with near-complete independence, you will manage long-term assignments with loosely-defined outcomes, balancing expert-level technical execution with the operational discipline required to ship high-performance hardware. WHAT YOU'LL DO: * Own System Execution: * * Drive the design, integration, and validation of advanced R&D equipment for thin-film processing, taking independent ownership of long-term projects and major mechanical sub-systems * Act as technical Lead & Responsible Engineer (RE): * Provide technical leadership on complex, cross-functional projects, leading small project groups and serving as a discipline-specific advisor * Solve Highly Complex Problems: * Address ambiguous technical challenges impacting multiple groups, proactively removing project barriers and generating novel solutions * Plan & Organize Milestones: * Generate detailed work plans and milestones for complex and semi-ambiguous hardware developments * Standardize Best Practices & Policies: * Drive continuous process improvement, tool development, and department policies using semiconductor standards as your guide * Manage Project Risk: * Independently manage medium risks, identify larger system risks, and drive the development of robust mitigation solutions * Collaborate & Influence: * Build strong relationships across departments, effectively communicating highly complex concepts to diverse audiences and resolving cross-functional conflicts to achieve alignment * Mentor Talent: * Actively mentor junior colleagues, taking direct ownership of their technical growth and skill development * Deliver with Speed: * Translate system-level requirements into innovative concepts, driving projects efficiently from initial design through assembly, testing, and implementation WHAT WE’RE LOOKING FOR: * Education: * Master’s degree in Mechanical Engineering or a related field (or equivalent industrial experience) * Experience: * 10+ years of experience in the design and implementation of complex R&D systems or semiconductor manufacturing equipment * Domain Expertise: * Expert-level mastery of core mechanical engineering functions with a deep technical focus on thin-film processing hardware or vacuum systems * Autonomy & Judgment: * Proven ability to operate independently with near-complete autonomy, making sound judgment calls that impact the overall success of major project components * Thermal & Structural Expertise: * Proven capability in high-temperature structural design and complex thermal management within vacuum environments * Vacuum System Proficiency: * Deep understanding of vacuum architecture, including material outgassing, seal integrity, and pump-down optimization * Software Mastery: * Expertise in 3D modeling (SolidWorks and/or NX) and familiarity with leveraging FEA/Thermal simulation tools (COMSOL, ANSYS) to make data-driven decisions * Hands-on Capability: * Ability to bridge the gap between design and the shop floor, including experience with manual/CNC machining, prototyping, and hardware troubleshooting * Vendor Management: * Experience selecting and qualifying global vendors for specialized components or custom sub-systems BONUS POINTS FOR: * Semiconductor Background:  * Prior success building first-of-kind or experimental tools for semiconducto * Standards Knowledge:  * Familiarity with applying SEMI, ASME, ASTM, and other industry-standard mechanical codes to hardware designs * Motion Control: * Experience designing precision motion and motor-controlled systems within challenging environments MUST-HAVE REQUIREMENTS: * Ability to occasionally lift up to 50 lbs * Perform activities such as stooping, climbing, standing, or sitting for extended periods of time * Dedication to safety to mitigate industrial hazards that may include heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, and cryogenics * Willingness to travel or work required nights/weekends/on-call occasionally #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.