Engineering Physics Intern - Neutron Diagnostics

About Marathon Fusion

Marathon Fusion is building the technologies needed to make fusion practical. Our work spans high-flux fusion neutron sources for radioisotope production, fuel cycle technologies, and plant-level systems that will enable fusion power at climate-relevant scale.

We are developing compact, beam-driven fusion systems to produce radioisotopes for targeted cancer therapies and to test materials for future fusion power plants. Alongside this work, we develop stable isotope enrichment, tritium processing and recycling, and advanced blanket technologies to close the fusion fuel cycle and enable both energy generation and high-value co-products.

Founded in 2023, Marathon Fusion is advancing near-term applications of fusion in medicine and materials development while building the foundation for abundant, reliable energy in the 21st century.

Culture at Marathon Fusion

We are a startup environment characterized by a need for focus, adaptability and prioritization in a shifting landscape. Thriving in this environment requires excellent proactive communication across roles and backgrounds, the ability to build and maintain trust between team members, and the willingness to learn and develop new skills on the job. We place particularly high weight on each team member's ability to be self-directed.

Please review these points carefully before applying:

• This application is exclusively for the Engineering Physics - Neutron Diagnostics role.

• We provide both Internship and Co-op placements through this single posting.

• Application Deadline: December 2nd, 2026

The engineering physics intern position is a hands-on, in person role working directly with our research and development team. Projects and mentors will be matched to your interests and our needs. These projects fall under several categories including neutron diagnostics, target design, and test stand development.

Example responsibilities include:

• Assemble and characterize plastic scintillation detectors for real-time neutron monitoring

• Perform gamma spectroscopy calibrations and measurements for activation foil counting

• Research and prototype novel manufacturing methods for critical components

• Commission and operate a test stand

• Operate and troubleshoot diagnostic instruments

• Analyze diagnostic data to track experiment performance and inform system upgrades

• Document systems and workflows so others can maintain them

Technical Roles at Marathon Fusion

We are primarily interested in interns who are:

• Studying physics, but have meaningful hands-on experience in areas such as fabrication, mechanical engineering, test engineering, vacuum systems operation, or similar.

• Studying mechanical engineering, but have had meaningful exposure to physics through coursework, internships, projects or personal study.

• Studying a combination of both in an engineering physics program, double major or similar.

• Studying an engineering field or other technical field and have exceptional work-ethic, eagerness to learn, and autonomy.

We don't expect, but would be particularly excited about any candidates with experience in the following: plasma physics, plasma diagnostics, vacuum systems, radioactive materials handling, fabrication for scientific applications, and Monte Carlo transport codes.

For all roles, important soft skills include:

• Excellent written and oral communication

• Ability to think holistically about systems

• Capacity to learn new technical subjects quickly, collaborate cross-functionally, and consider problems from inter-disciplinary perspectives

• Organization and project management

• A high degree of conscientiousness and integrity

• Long-term vision while executing short-term goals

• Comfort with the inherent uncertainty of breakthrough technology

• Experimental mindset, ability to form and test hypotheses

Compensation

Undergraduate interns are paid $27.88/hour. More experienced interns can earn up to $40.87/hour depending on qualifications.

Marathon Fusion considers all qualified applicants equally for employment. We do not discriminate on the basis 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, ordinance, or regulation.