Cryophysicist

Xcimer Energy

200

Denver, CO

Posted on: 2026-09-29

Category: energy

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Employment type:

Full time

Experience required:

Intermediate

Salary

$140,000.00 - $165,000.00

About the company:

Xcimer Energy is a fusion energy company focused on commercializing laser-driven inertial confinement fusion, which it describes as the only scientifically validated form of fusion energy. The company is developing high-energy excimer laser systems designed to ignite fusion reactions using fuel derived from seawater and lithium, with the goal of delivering safe, clean, and affordable electricity that is cost-competitive with fossil fuels and renewables. Its mission centers on decarbonizing energy-intensive sectors such as artificial intelligence infrastructure, desalination, and industrial processes that require firm, always-on, carbon-free power. Xcimer's technical approach relies on electron-beam-pumped excimer lasers combined with a pulse compression technique called Stimulated Brillouin Scattering (SBS), which compresses microsecond laser pulses to nanosecond durations without damaging optics. In 2024 the company broke ground on Phoenix, its first prototype high-energy laser system, located in Denver, Colorado, and announced the start of its operations in June 2026. Phoenix is the first electron-beam-pumped excimer laser built in the private sector in more than two decades and validates key elements of the company's low-cost laser fusion architecture. Xcimer's longer-term target is Athena, which it describes as the world's first laser fusion power plant, expected to deliver 400 megawatts of continuous clean energy by 2035. The company has received a U.S. Department of Energy approval of its fusion power plant preconceptual design and technology roadmap milestone, and collaborates with industrial partners such as TRUMPF Laser SE. With a team of nearly 200 engineers, physicists, and business professionals, Xcimer positions itself as the most technically mature private laser fusion company.

Xcimer Energy leverages decades of research on Inertial Fusion Energy (IFE) combined with groundbreaking new laser architecture. Our mission is to deploy fusion power plants to meet global decarbonization goals as fast as possible. Xcimer has assembled a team of leaders in tough tech, fusion science, and manufacturing with a track record of rapid execution. Supported by leading investors, Xcimer is uniquely positioned to deliver limitless, clean, fusion power to combat climate change. Join us in powering a better world with inertial fusion!

This is a full-time, onsite role based at our headquarters in Denver, CO.

We are welcoming applicants for a Cryophysicist position on Xcimer’s Fill and Injection Station Team. The successful candidate will join a growing group of engineers and scientists aimed at developing the processes and technologies to build a first of its kind Inertial Fusion Energy fueling station for Xcimer’s fusion reactor plant. In this role, you will lead the experimental and theoretical design, characterization, and optimization of physical systems operating at ultra-low temperatures. You will manage relations and work closely with collaborators from national labs and universities to drive research objectives that will critically impact future system design and architecture. This is an entry- to mid-level role focused on experimental and theoretical R&D.

Equal Employment Opportunity

Xcimer Energy is proud to be an Equal Opportunity/Affirmative Action Employer and is committed to attracting, retaining, and developing a highly qualified, diverse, and dedicated work force. Xcimer Energy hires and promotes people on the basis of their qualifications, performance, and abilities. We support the establishment and maintenance of a workplace that fosters trust, equality, and teamwork, in which all employees recognize and appreciate the diversity of individual team members. We provide all qualified applicants for employment and employees with equal opportunities for hire, promotion, and other terms and conditions of employment, regardless of their race, color, religion, gender, sexual orientation, gender identity, national origin/ethnicity, age, physical or mental disability, genetic factors, military/veteran status, or any other status or characteristic protected by federal, state, and/or local law. Xcimer Energy will consider for employment qualified applicants with criminal histories in a manner consistent with applicable federal, state, and local laws. For more information on “EEO Is the Law,” please see here and here.

Benefits

Xcimer offers a comprehensive benefits package designed to support employee health, well-being, and long-term success. Benefits include medical, dental, and vision coverage; basic and supplemental life insurance; short- and long-term disability; paid parental leave for employees at the time of birth or adoption; and a 401(k) with a company match of up to 6%. Eligible employees also receive equity, allowing them to share in the company’s long-term success.

Xcimer operates under a flexible Paid Time Off (ATO) approach. Rather than a fixed number of vacation days, employees are trusted to take the time they need to rest and recharge while meeting the expectations of their role and team. In addition, employees receive paid sick time, 13 company-paid holidays, and an annual paid company shutdown. Benefits are available to regular employees, including part-time and fixed-term roles, as well as interns, with eligibility varying by benefit.

Responsibilities

Experimental Research

Design, build, and iterate on experiments aimed at advancing target filling processes and technologies.
Evaluate, analyze, and improve system designs aimed at streamlining rapid target throughput.
Own the documentation and management of internal test stands and their experiments.
Partner with a varied team of scientists, engineers, and designers to translate experience into realizable products.

Modeling and Simulation

Advance the team’s predictive capabilities utilizing COMSOL Multiphysics to model physical systems.
Leverage Python to develop in-house simulations for thermal transport, fluid flow, and materials interactions.
Provide insight into results from collaborators and internal experiments using analysis and modeling methods.
Own documentation and artifacts for developed models and simulations.

Work Share Rotation

Split your time between the Xcimer Fill and Injection Station team and our external collaborators.
Serve as the primary contact for the knowledge transfer between our collaborators and Xcimer.
Balance the role of being both mentor and mentee to both teams.

Research and Development

Provide fresh perspectives on challenging engineering problems concerning high pressure, high vacuum, and cryogenic environments.
Own research tasks which will help push the team’s understanding of system capabilities and risks.
Integrate into an agile team focused on advancing technologies through rapid prototyping and reliance on the build-test-fail-repeat methodology.

Qualification

Education: Master’s + 3 years experience or PhD in applied physics, engineering physics, mechanical engineering, aerospace engineering, vacuum engineering, or related field
Experience: 0 - 3+ years of experience in the fields of cryophysics, thermodynamics, superconducting magnetics, or similar background
Expertise in ultra low temperature engineering and design with a focus on thermal transport, mechanical compatibility, or liquefaction
Demonstrated experience on system design and integration teams.
Demonstrated experience working in laboratory environments and hands-on experience with ultra-low temperature installations.
Demonstrated experience building thermal, fluid flow, and materials models.
Experience with both wet and dry cryogenic systems.
Experience collaborating with a multidisciplinary team of engineers, scientists, and non-domain experts supporting system design.
Highly self-motivated, with the ability to work independently without guidance.
Advanced verbal and written communications skills.
Must be a U.S. citizen or national, U.S. permanent resident (current Green Card holder), or lawfully admitted into the E.S. as a refugee or granted asylum.

Desired

Familiarity with instrumentation controls and scripts, specifically PyVISA and SCPI commands.
Familiarity with project life-cycle management and the AGILE structure.
Cryogenics handling safety training.
Experience with vendor interactions and supply management.
Experience working in a start-up or quick paced environment.
Background supporting team expansion and providing mentoring to junior contributors.
Experience working on R&D teams or developing low TRL products.