New York City, New York, United States Borealis Fusion is hiring a Senior Experimental Physicist to design our first experimental campaign, with the opportunity to build and lead the company's experimental program. You will work directly with the CTO and founding team to turn our theory and simulations into experimental requirements, diagnostics and a buildable platform.
Why this role exists
Our mission is to make fusion the lowest-cost source of firm electricity. We chose proton-boron-11 (pB11) as our fuel because it promises the simplest and cheapest plant: the primary reaction produces no neutrons, and the fuel cycle needs no tritium. The plasma conditions are the price. pB11 requires ion temperatures roughly twenty times higher than deuterium-tritium, and bremsstrahlung losses leave a narrow margin for power production. In 2025 members of our team showed that accumulated helium ash makes the problem worse: it increases X-ray losses so much that better confinement alone cannot deliver breakeven.
Our confinement architecture, PRISM, derives from the tandem mirror, chosen because open field lines offer ways to expel helium ash while retaining fuel. Ash management, radiation suppression, fuel confinement and plasma heating must all be achieved at once. Our published theory and current modeling suite predict an operating point where these hold together. The first experimental campaign exists to test the physics against a real plasma.
You will design that campaign.
The company
Borealis Fusion was founded in 2026 by five co-founders whose backgrounds span analytic theory, computational modeling, and engineering across a broad range of plasma systems. We have a working suite of in-house simulation tools and no experimental hardware. You will be the first new hire and the first experimentalist.
What you will own
Requirements. With the CTO, you help translate the risk retirement path into firm machine and diagnostic requirements for our first experimental campaign. You own the requirements document.
Design. You will design the experimental platform, within the technical roadmap requirements set with the CTO. You will collaborate closely with the modeling team to establish machine architecture, the major subsystems (vacuum, magnets, power delivery, diagnostics, etc.), and their integration, to test the core physics underlying the PRISM concept.
Vendors. You select and manage vendors for major subsystems and cost the machine with them.
Site. Outlining site requirements (power, footprint, safety, permitting, cost) and helping to select the site for the experimental facility is a first-year deliverable.
Team. You hire and mentor experimentalists and technicians and establish operating procedures for the laboratory.
Technical direction runs through the CTO. Budget runs through the CEO. You have a direct line to both.
What you have done
- Personally built, or led a major extension of, a high-power laboratory experiment: a plasma device (mirror, FRC, tokamak subsystem) or a comparable high-vacuum, high-voltage or pulsed-power system.
- Worked hands-on across several of: high vacuum, pulsed power or high-power RF, magnets, plasma diagnostics, high-voltage safety.
- Taken a system from design through commissioning, including vendor management and schedule ownership.
- Designed an experiment that discriminated between hypotheses: chose the measurements, quantified the uncertainty, and reported the result either way.
What else helps
- PhD in plasma physics or a related field. Build record matters more than publication record.
- Magnetic mirror experience.
- Hired and mentored experimentalists, technicians and scientists.
- Owned safety or permitting for a facility or a major experimental system, or know what that ownership means outside a university EHS umbrella.
Horizon
First plasma is a multi-year outcome. The first year is requirements, design, costing, vendor selection, and site selection. Construction, commissioning, and the first campaign follow. If you are looking for first plasma inside twelve months, this is the wrong company. There is no hardware to run in the first year.
Level and growth
This is an opportunity to build and lead Borealis's experimental program: shape experimental priorities with the CTO, recruit and lead the experimental team, and establish how we design and run experiments. For a candidate with a record of building and leading experimental programs, that scope can begin on joining, with a title to match. Otherwise the role starts as Senior Experimental Physicist and takes on that scope as the program develops. We will agree on initial title and scope during hiring.
Location
Hybrid in New York or remote during the design phase, with travel to vendors and candidate sites. The experimental facility has not been selected; you will help select it. Once it is selected and construction begins, the role is primarily on site.
