Physicist/Scientist- X-Ray Source Modeling - Benicia, CA, United States

Originally posted 18 September 2026 by the employer.

This role focuses on physics modeling for X-ray sources, including electron optics, thermal behavior, and X-ray generation and transport.

About the role

This role involves owning the physics modeling that sets the performance limits of X-ray sources, encompassing electron optics, thermal behavior of components, and X-ray generation and transport.

What you'll do

• Simulate electron optics end to end, including thermionic emission, space-charge-limited transport, focusing, aberration, deflection, and spot formation.
• Build coupled electrothermal models of beam power deposition on targets, apertures, and grids.
• Model X-ray generation and transport, including bremsstrahlung and characteristic emission yield, self-absorption, and spectral shaping.
• Quantify and communicate uncertainty through convergence and mesh studies, sensitivity analysis, and explicit model prediction statements.
• Design experiments to test models and identify measurable discriminators between hypotheses.
• Translate sensitivity results into design and manufacturing decisions, such as drawing tolerances, alignment budgets, and process windows.
• Script and version simulation workflows for reproducibility and re-running of parametric studies.
• Contribute to technical customer engagements.
• Mentor junior physicists and engineers in modeling practice.

What you'll need

• MS or PhD in physics, applied physics, EE, ME, nuclear engineering, or a related field, plus 5+ years applying simulation to physical hardware.
• Demonstrated ownership of at least two of: charged particle optics, thermal and structural analysis materials under high thermal load, X-ray generation and optics.
• Fluency in finite element methods and working knowledge of at least one other relevant numerical approach: boundary element, particle-in-cell, Monte Carlo radiation transport, or ray tracing.
• Experience with multiphysics tools (COMSOL, Opera, CST, ANSYS, Lorentz, FEniCS, or comparable) driven through scripting interfaces.
• Proficiency in Python, C, or C++ for pre- and post-processing, data reduction, and optimization loops.
• Habit of using version control.
• Track record of comparing model to measurement, identifying disagreements, and diagnosing causes.

Nice to have

• Experience with Monte Carlo radiation transport (Geant4/TOPAS, PENELOPE, EGSnrc) for electron-target interaction, spectrum, and dose.
• Experience with X-ray optics simulation (SHADOW/OASYS, XRT, McXtrace, SRW) and dynamical diffraction calculation for crystal optics.
• Knowledge of cathode and emission physics: dispenser cathodes, LaB₆ or CeB₆, field emission, lifetime, and poisoning mechanisms.
• Experience with high-vacuum practice: outgassing, thermal management across brazed and welded joints, contact conductance, high-voltage holdoff, and breakdown.
• Background in adjacent fields: accelerator or beamline physics, electron microscopy, vacuum electronics (TWT, klystron, magnetron), medical or industrial X-ray tubes, e-beam lithography, semiconductor metrology.
• Experience with design of experiments, numerical optimization, surrogate or reduced-order modeling.
• Comfort working from mechanical CAD, including defeaturing and model prep.

Skills: physics modeling, X-ray sources, electron optics, thermal behavior, multiphysics tools, finite element methods