Mission Support and Test Services, LLC (MSTS) manages and operates the Nevada National Security Site (NNSS) for the U.S. National Nuclear Security Administration (NNSA). Our MISSION is to help ensure the security of the United States and its allies by providing high-hazard experimentation and incident response capabilities through operations, engineering, education, field, and integration services and by acting as environmental stewards to the Site’s Cold War legacy. Our VISION is to be the user site of choice for large-scale, high-hazard, national security experimentation, with premier facilities and capabilities below ground, on the ground, and in the air. (See NNSS.gov for our unique capabilities.) Our 2,750+ professional, craft, and support employees are called upon to innovate, collaborate, and deliver on some of the more difficult nuclear security challenges facing the world today.
The NNSS Science & Technology Directorate invites exceptional early‑career scientists to apply for the Bruno Rossi Distinguished Postdoctoral Fellowship. The Rossi Fellow will drive advances in the theory, computational modeling, and/or machine‑learning applications to the Scorpius linear induction accelerator (LIA) - one of the Nation’s flagship capabilities supporting NNSA missions. This is a high‑impact, publication‑friendly role embedded with a senior NNSS mentor and collaborating laboratories.
Fellowship Focus Areas (Theory/Computation/ML)
We are seeking exceptional early-career PhD scientists or engineers with expertise in accelerator physics and a passion for applying data science, artificial intelligence (AI), and machine learning (ML) to model, control, and optimize complex systems. We also welcome applicants with a strong background in computational science who are eager to apply their skills to challenges in accelerator science. In particular, fellows will be fully supported to lead a research program focused on one or more of the following areas.
A. Accelerator & Beam Physics (Theory/Computation)
·Relativistic Beam–Target Interaction Physics: Investigating beam interactions with complex bremsstrahlung converters, including X-ray source modeling, dose and fluence optimization, and converter survivability under advanced material responses.
·Beam Transport in Complex Environments: Studying beam transport in solenoidal and induction systems, with emphasis on emittance preservation, halo formation and mitigation, and energy spread control under realistic operating conditions.
·Collective Effects and Instabilities: Developing models and mitigation strategies for phenomena such as Beam Breakup (BBU), corkscrew motion, and transverse/longitudinal impedance-driven instabilities.
Pulsed-Power and Accelerator Coupling: Exploring circuit-beam co-simulation, magnet and induction module dynamics, and timing and waveform shaping to enhance stability and brightness.
Diagnostics by Design: Creating inference methods and synthetic diagnostics to extract critical machine parameters—such as emittance, current, energy, spot size, and centroid motion—from limited data, while incorporating uncertainty quantification and error budgets for machine studies.
·Multiphysics Target Response: Modeling the Magneto-Hydrodynamics (MHD) and thermomechanics of converter materials under intense pulsed loading, including shock and thermal fatigue, to evaluate lifetime and performance trade-offs.
Representative tools and methods: Particle-In-Cell (PIC) and Vlasov–Fokker–Planck simulations, hybrid PIC–fluid models, envelope and moment techniques, Monte Carlo radiation transport, surrogate modeling, adjoint and gradient‑based optimization, as well as rigorous uncertainty quantification (UQ) and sensitivity analysis.
B. Machine Learning, Artificial Intelligence, and Digital Twin Foundations for the Scorpius Accelerator
·Data-Driven Machine Tuning: Optimizing accelerator performance by leveraging cutting-edge methods to rapidly identify optimal set points and compensate for beam drifting across multiple shots and variable thermal states.
Predictive Maintenance and Anomaly Detection: Applying time-series modeling to pulsed-power components and beam diagnostics for fault prediction, remaining useful life estimation, and automated alert systems.
Physics-Constrained Machine Learning: Implementing novel neural network architectures and reduced-order modeling techniques, constrained by first-principles physics, to deliver fast and explainable predictions.
Uncertainty-Aware Control: Developing decision-making frameworks with calibrated posteriors to ensure safe operation, while building digital twin architectures and data pipelines that integrate simulation, controls, and diagnostics in near-real time.
Successful applicants will be expected to demonstrate a sophisticated understanding of these methodologies. This includes a meticulous selection of appropriate techniques, awareness of their inherent limitations.
This fellowship offers a distinguished opportunity to drive transformative innovation at the forefront of accelerator science. The Rossi Fellow will be instrumental in developing and demonstrating next-generation capabilities for the Scorpius accelerator and allied radiographic systems. This foundational work is critical for achieving enhanced brightness, stability, system responsiveness, and long-term reliability, directly reinforcing the strategic imperatives of NNSA’s stockpile stewardship mission. The Fellow's research will provide a definitive basis for optimizing machine studies, informing strategic hardware development, and accelerating the realization of the full Scorpius digital twin
Application Materials
Please combine materials into a single PDF when possible:
Interviews: Finalists will be invited for a two‑day on‑site interview, including a technical seminar on current work and proposed research.
About the Fellowship & Namesake
The fellowship honors Bruno Benedetto Rossi (1905–1993), a trailblazing experimental and theoretical physicist whose career helped shape modern particle physics, space plasma physics, and x-ray astronomy. Trained at the University of Bologna, and having collaborated with Niels Bohr in Denmark, Patrick Blackett at the University of Manchester, and Enrico Fermi at the University of Chicago, Rossi later became a professor at MIT. There, he pioneered the electronic coincidence method, which enabled unambiguous detection of rare, fast events and opened the door to modern high-energy instrumentation.
His early work established the charged nature of cosmic rays , mapped their latitude/altitude effects, and revealed extensive air showersproduced by ultra-high-energy primaries.
During the Manhattan Project, Rossi led diagnostic development at Los Alamos, including fast ionization chambers and timing methods crucial to understanding implosion dynamics. After the war, he founded the renowned MIT Cosmic Ray Group, which evolved into the Center for Space Research. Rossi’s group instrumented early space missions that characterized the solar wind, and he championed the first detections that launched x-ray astronomy, demonstrating that the universe is bright in high-energy photons.
The Rossi Fellow carries forward this legacy: rigorous physics, elegant instrumentation by model and algorithm, and science in service to national missions.
For More Information
Learn more about the fellowship and its namesake at the NNSS page: https://nnss.gov/mission/sdrd/bruno-rossi-distinguished-postdoctoral-fellowship-in-science-and-technology/
Primary duty location is the NNSS’ North Las Vegas facility with occasional travel to the NNSS site, LANL, LLNL, and SNL.
A 4/10 work schedule (Mon–Thu) is typical and subject to change. Limited hybrid arrangements may be considered depending on program needs and security requirements.
MSTS is required by DOE directive to conduct a pre-employment drug test and background review that includes checks of personal references, credit, law enforcement records, and employment/education verifications. Applicants offered employment with MSTS are also subject to a federal background investigation to meet the requirements for access to classified information or matter if the duties of the position require a DOE security clearance. Substance abuse or illegal drug use, falsification of information, criminal activity, serious misconduct or other indicators of untrustworthiness can cause a clearance to be denied or terminated by DOE, resulting in the inability to perform the duties assigned and subsequent termination of employment. In addition, Applicants for employment must be able to obtain and maintain a DOE Q-level security clearance, which requires U.S. citizenship, at least 18 years of age. Reference DOE Order 472.2, “Personnel Security”. If you hold more than one citizenship (i.e., of the U.S. and another country), your ability to obtain a security clearance may be impacted.
Department of Energy Q Clearance (position will be cleared to this level). Reviews and tests for the absence of any illegal drug as defined in 10 CFR Part 707.4, “Workplace Substance Abuse Programs at DOE Sites,” will be conducted. Applicant selected will be subject to a Federal background investigation, required to participate in subsequent reinvestigations, and must meet the eligibility requirements for access to classified matter. Successful completion of a counterintelligence evaluation, which may include a counterintelligence-scope polygraph examination, may also be required. Reference 10 CFR Part 709, “Counterintelligence Evaluation Program.”
MSTS is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, national origin, disability, veteran status or other characteristics protected by law. MSTS is a background screening, drug-free workplace.
The Nevada National Security Sites help ensure the security of the United States and its allies by: supporting the stewardship of the nation’s nuclear deterrent; providing nuclear and radiological emergency response capabilities and training; contributing to key nonproliferation and arms control initiatives; executing national-level experiments in support of the National Laboratories; working with national security customers and other federal agencies on important national security activities; and providing long-term environmental stewardship of the NNSS’s Cold War legacy.
