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Xcimer Energy

Develops inertial fusion power using laser

Director of Fusion Nuclear Science

Full-TimeUpdated on 10/23/2026
$220k - $260k/yr+ Equity
Expert
PhD
Denver, CO, USA
In PersonFull-time, onsite at headquarters in Denver, Colorado.
Academic & Institutional Research
No H1B Sponsorship

About the job

Requirements
  • A PhD in Nuclear Science, Nuclear Engineering, Nuclear Physics, or a closely related field is required.
  • At least 12 years of experience in analysis, simulation, experimental research and development, or technology development for complex nuclear or fusion systems under extreme thermal and radiation environments is required.
  • At least 6 years of leadership experience in multidisciplinary scientific or research and development organizations is required.
  • Deep experience with nuclear analysis tools such as MCNP, multiphysics simulation software such as COMSOL and ANSYS, and reactor thermal-hydraulic codes such as RELAP and MELCOR is required.
  • Experience designing and executing experiments that raise component or system technology readiness is required.
  • A proven record of mentoring and growing high-performing technical teams is required.
  • A strong publication and scientific leadership record is required.
  • Ability to operate effectively within a rapidly evolving organization transitioning from startup to industrial scale is required.
  • Ability to balance hands-on scientific leadership with high-level strategic direction and organizational oversight is required.
  • Applicants must be U.S. citizens or nationals, U.S. permanent residents who currently hold a Green Card, or lawfully admitted to the United States as refugees or granted asylum.
Responsibilities
  • Build, lead, and grow the Fusion Nuclear Science department, including hiring, onboarding, mentoring, and professional development of scientific staff.
  • Define and own the scientific roadmap for fusion chamber dynamics, blanket multiphysics, tritium science, and supporting fusion nuclear science domains.
  • Develop the strategy for scientific tools, modeling frameworks, experimental capabilities, and validation infrastructure.
  • Oversee scientific analysis, modeling, code development, and experimental programs, emphasizing reproducibility, uncertainty quantification, and model credibility.
  • Translate scientific insights, experimental data, and validated models into design guidance for engineering teams responsible for fusion system architecture.
  • Collaborate with engineering and operations divisions and other science departments to ensure communication and alignment.
  • Evaluate emerging scientific opportunities and integrate advances from academia, national laboratories, and international fusion programs.
  • Manage relationships with external laboratories, university collaborators, and vendors providing modeling tools, experimental facilities, or other fusion nuclear science scope.
  • Establish department-wide scientific best practices, documentation standards, review processes, and quality expectations appropriate for industrial fusion systems.
  • Identify key scientific risks across fusion nuclear science programs and drive mitigation strategies supporting execution and long-term scalability.
  • Support system troubleshooting, root-cause investigations, and scientific review of failures or anomalies encountered in development or experimental operations.
  • Align fusion nuclear science priorities with company strategy, program schedules, resource constraints, and commercialization goals in partnership with executive leadership.
Desired Qualifications
  • Experience in fusion chamber research, blanket multiphysics, and tritium fuel cycle analysis.
  • Familiarity with fusion safety and regulatory requirements.
  • Experience in the commercial nuclear industry or at fusion experimental facilities.
  • Knowledge of tritium handling systems and molten salt technologies.
  • Familiarity with fusion plant design and commercialization efforts.

About the company

Xcimer Energy develops inertial fusion energy technology aiming to generate fusion-powered electricity. Its system uses a 10+ megajoule KrF laser to ignite a hydrogen fusion target inside a HYLIFE-style liquid-wall chamber, which absorbs fusion energy and shields reactor walls for long life. The approach combines a high-energy laser, a consumable fusion target, and a liquid-wall chamber to pursue scalable, laser-driven inertial confinement fusion for power generation. The company’s goal is to make commercial fusion power a reality for utilities within the next decade.

Company Size

51-200

Company Stage

Grant

Total Funding

$148.3M

Headquarters

Denver, Colorado

Founded

2021

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Simplify's Take

What believers are saying

  • Xcimer raised $100 million in June 2024 and nearly $200 million total.
  • The company expanded Denver in May 2026 and planned to double headcount.
  • DOE funding, June 2026 approval, and RTX backing improve financing and recruiting access.

What critics are saying

  • Vulcan site selection slipped past 2025; further delays push commercialization beyond 2035.
  • Athena needs multi-megajoule lasers, tritium breeding, and grid integration before any revenue.
  • Any Phoenix-to-Anvil performance miss would strand Xcimer’s capital-intensive laser platform.

What makes Xcimer Energy unique

  • Xcimer’s June 2026 DOE-approved Athena roadmap validates its KrF inertial-fusion architecture.
  • Phoenix started operations June 3, 2026, proving 1-kJ excimer amplification and 38-meter SBS compression.
  • RTX partnered September 9, 2026, giving Xcimer defense-market validation beyond fusion alone.

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Benefits

  • Health Insurance
  • Dental Insurance
  • Vision Insurance
  • Life Insurance
  • Disability Insurance
  • 401(k) Company Match
  • Paid Vacation
  • Paid Sick Leave
  • Paid Holidays
  • Company Equity

Growth & Insights and Company News

6 month growth

-3%

1 year growth

-3%

2 year growth

-3%
StreetInsider
Oct 6th, 2026
Xcimer Energy secures $30.5M DOE funding for laser fusion development, bringing total federal support to $43.5M

Denver-based Xcimer Energy has secured an additional $30.5 million from the US Department of Energy's Milestone-Based Fusion Development Program. This brings the company's total potential DOE milestone funding to $39.5 million, with an additional $4 million previously received from ARPA-E in 2024. The laser fusion company is developing excimer laser technology designed for commercial fusion power plants. Unlike conventional solid-state approaches, Xcimer's architecture uses cost-effective gas lasers and a two-beamline configuration. In June, Xcimer launched Phoenix, the world's largest privately owned laser system. The company recently partnered with RTX to develop directed-energy air defence systems, with RTX also making an investment in Xcimer. Xcimer targets putting electricity on the grid by the mid-2030s. The company has raised approximately $200 million from investors including Breakthrough Energy Ventures and Lowercarbon Capital.

Associated Press
Sep 10th, 2026
RTX invests in Xcimer Energy to develop laser fusion technology for air defense systems

RTX Ventures has made a minority investment in Xcimer Energy Corporation to support development of scalable pulsed-laser technologies. Xcimer has raised nearly $200 million from investors including Hedosophia and Breakthrough Energy Ventures. The companies signed a teaming agreement to explore integrating Xcimer's laser technology into RTX's defence systems for defeating airborne threats. Xcimer's fusion pilot power plant design was approved by the US Department of Energy in June as part of the Milestone-based Fusion Development Program. The excimer laser system aims to deliver longer-range performance at lower cost than current directed energy systems. Xcimer expects to deliver fusion energy to the grid by the mid-2030s. RTX's chief technology officer Juan de Bedout said the partnership will explore integrating Xcimer's technology with RTX's expertise in advanced sensing and air defence.

Business Wire
Jun 10th, 2026
DOE approves Xcimer's fusion power plant design, clears path to commercial laser fusion

Xcimer Energy has secured US Department of Energy approval for its preconceptual design and technology roadmap for Athena, its fusion power plant architecture. The milestone, part of the DOE's Fusion Milestone Development Program, positions the Denver-based startup amongst frontrunners to commercialise fusion energy. Xcimer's 724-page submission detailed plant performance targets, economics, engineering requirements, safety analyses and development pathways. Athena integrates the company's proprietary excimer laser platform with target delivery, fusion chamber, tritium breeding and power generation systems designed for industrial scale. The approval follows Xcimer's launch of Phoenix, the world's largest privately owned laser system, at its 74,000-square-foot Denver facility. Founded in 2022, Xcimer is developing laser fusion technology targeting costs under $100 per joule with a chamber design requiring no first-wall replacement.

TechCrunch
Jun 3rd, 2026
World's largest privately owned laser switched on by fusion startup Xcimer Energy

Fusion startup Xcimer Energy has activated its Phoenix laser system, which the company claims is the world's largest privately owned laser. The system uses excimer amplification to generate over one kilojoule of energy through a 38-metre-long krypton-fluoride laser core. Xcimer's approach mirrors the National Ignition Facility, which in December 2022 demonstrated a controlled fusion reaction producing more power than required to ignite it. The company aims to improve upon this concept using more powerful, less complex lasers that compress fuel targets in nanoseconds rather than microseconds. Phoenix represents an early step towards a commercial fusion power plant, which Xcimer estimates would require lasers exceeding 12 megajoules. The company plans to complete a prototype by 2028 and build its first commercial-scale power plant in the mid-2030s.

Business Wire
May 12th, 2026
Xcimer Energy hires defence VP as fusion startup scales team to 400 amid $90M facility build

Xcimer Energy has hired Doug Kunzman as Vice President of Defence as the Denver-based fusion startup scales towards commercial operations. Kunzman brings extensive military and aerospace experience, including commanding US Navy warships and leading operations at Blue Origin and Astra. The company, which now employs nearly 200 people, plans to double its workforce over the next year to advance Vulcan, its next-generation laser fusion facility. Xcimer is developing excimer-laser architecture for scalable inertial fusion energy with applications in energy resilience and national security. Recent leadership additions include Brad Appel as Chief Engineer for Vulcan, previously CTO at Ursa Major and SpaceX; Justin Brynestad as Senior Vice President overseeing Vulcan programme execution; and Rachel Konrad as Senior Vice President of Strategic Communications. Founded in 2022, Xcimer has secured Department of Energy funding.