Research Scientist - Plasma Diagnostics

Marathon Fusion•San Francisco, CA

About The Position

Marathon Fusion is building the engineering technologies needed to scale fusion from breakeven experiments into real power plants. While much of the industry is focused on proving new fusion devices, our focus is on the practical systems that will make fusion deployable at climate-relevant scale. We develop core fuel cycle and plant-level technologies for stable isotope production, fuel cycle closure, and advanced blanket systems that enable both energy generation and high-value co-products. Founded in 2023, Marathon Fusion is building the components and systems that will help fusion become a practical, abundant, and reliable energy source for the 21st century. As a research scientist, you’ll work closely with plasma physicists, engineers, and technicians to design, deploy, and operate optical diagnostics that are central to advancing stable isotope production and fusion fuel cycle technologies. This role requires deep hands-on experience with experimental plasma diagnostics, combined with systems-level thinking and the ability to lead diagnostics from concept through commissioning and operation. You will play a pivotal role in validating plasma performance and informing design decisions for a first-of-a-kind isotope separation system.

Requirements

M.S. or higher Plasma Physics, Applied Physics, or a closely related field
5+ years of hands-on experience developing and fielding experimental plasma diagnostics
Demonstrated experience owning diagnostics from concept through commissioning and operation
Strong background in optical diagnostics, such as spectroscopy, interferometry, or laser-based techniques
Proven experimental skills including instrument calibration, signal processing, and data analysis
Experience working in complex experimental environments such as high voltage, vacuum, strong magnetic fields
Ability to collaborate effectively across disciplines and translate diagnostic data into actionable insights
Comfort working in ambiguity, taking ownership of critical technical problems, and focusing effort on what moves the program forward
Excellent written and oral communication skills

Nice To Haves

PhD in Plasma Physics, Applied Physics, or a closely related field
Prior experience mentoring or technically leading other scientists or engineers
Experience in a startup or similarly fast-paced experimental R&D environment

Responsibilities

Lead the design, deployment, and iteration of optical plasma diagnostics and/or physical diagnostics for lithium plasmas and isotope separation experiments
Develop and field diagnostics such as high-resolution spectroscopy, interferometry, or Langmuir probes, to measure plasma velocity, temperature, and density
Design and execute experimental campaigns, including diagnostic calibration, validation, and uncertainty analysis
Analyze and interpret experimental data, developing robust and well-documented data processing pipelines
Work closely with plasma physicists, mechanical engineers, and controls engineers to integrate diagnostics with experimental systems
Document experimental results and technical decisions to inform design iterations and program direction
Mentor and support junior scientists and engineers on the diagnostics team, raising overall execution quality and scientific rigor