RF Analyst – SRF Cavities

Subcritical Systems Inc; Austin (TX); On-site; USD 120,000 - 170,000; Full time

Benefits offered by this job

Health insurance

Dental insurance

Vision insurance

Job summary

Subcritical Systems, Inc. in Austin, TX seeks an experienced RF designer to lead the electromagnetic design of superconducting RF cavities within AI-driven SRF cryomodules.

You will define cavity shapes, optimize performance metrics, and collaborate across SRF, mechanical, cryogenic, electrical, and manufacturing teams from concept through fabrication and cold testing. You will run iterations with ATLAS, validate outputs with physics data, and ensure design integrity prior to shop-floor

Qualifications

• Master's degree in Physics, Electrical Engineering, or related field; PhD preferred.
• 3+ years RF cavity, high Q filter, or accelerator design experience, or 7+ years broader RF/electromagnetics experience.
• Experience in 3D EM design of resonant cavities using CST/HFSS/COMSOL.
• Working knowledge of RF superconductivity and cavity figures of merit.
• Understanding beam-cavity interactions including beam loading and higher-order modes.
• Ability to produce clear design reports and presentations.

Responsibilities

• Own electromagnetic design of SRF cavities from requirements to cryomodule integration.
• Optimize cavity geometry for gradient, Q0, R/Q, and geometric factor.
• Analyze beam-cavity interactions and design input/HOM couplers.
• Evaluate multipacting, field emission, RF heat loads; collaborate on RF-structural analysis.
• Set RF acceptance criteria and support tuning measurements.
• Develop scripts to automate parametric simulations and optimization.
• Iterate designs with ATLAS and the team and promote safety culture.

Skills

RF engineering

Cross-disciplinary collaboration

Technical report writing

Python/MATLAB scripting

Beam-cavity interactions

Education

Master's degree in Physics or Electrical Engineering

PhD preferred

Tools

CST

HFSS

COMSOL

Python

MATLAB

Job description

Subcritical Systems, Inc. is a venture-backed startup in Austin, Texas building the accelerator driven systems and the only US commercial manufacturer of accelerator cavities. What Space X did for rockets, we plan to do for accelerator cavities and commercialize across applications of power production, medical isotopes, semiconductors and waste transmutation.

We are in the process of building the Energy Amplifier — a novel nuclear fission system in which a particle accelerator drives a subcritical core, making melt physically impossible for clean power production. Due to its inherent safety, our system has a more streamlined licensing process. Our founding team includes successful entrepreneurs with a track record of building several multibillion dollar companies in deep-tech, and scientists who were leading U.S. national labs with deep experience in accelerator & nuclear technologies.

We are actively hiring to expand our team as we work toward licensing, regulatory submissions, and construction of our first energy amplifier. More information is available at subcritical.com.

ROLE SUMMARY

This role leads the electromagnetic design of the superconducting RF cavities inside Subcritical Systems' AI-driven SRF cryomodules. You will set cavity shape, and optimize the figures of merit that drive accelerator performance and subsystem cost – accelerating gradient, peak surface fields, geometric factor, shunt impedance; while accounting for beam-cavity interactions: beam loading, input coupling, beam stability, multipacting, and field emission. You will be the technical authority for SRF cavity RF design, working closely with SRF, mechanical, cryogenic, electrical, and manufacturing engineers to carry cavities from concept through fabrication, cold testing, and commissioning.

You’ll run design iterations with ATLAS, our internal AI-assisted engineering platform, feeding it validated models, physical constraints, and test data, and verifying its outputs against physics and measurement before they reach detailed design or the shop floor.

KEY RESPONSIBILITIES

• Own the electromagnetic design of SSI's SRF cavities, from requirements and frequency choice through fabrication drawings and cryomodule integration.
• Optimize cavity geometry for gradient, intrinsic quality factor, R/Q, geometric factor, and peak surface fields using CST, HFSS, COMSOL, or equivalent solvers.
• Analyze beam-cavity interactions: beam loading, HOM spectra, impedance, and wakefields. Design input and HOM couplers for the required external quality factors and damping.
• Evaluate multipacting, field emission, and RF heat loads, and work with mechanical engineers on coupled RF-structural analysis (Lorentz force detuning, df/dP, tuning sensitivity).
• Set RF acceptance criteria and support frequency and field-flatness tuning, bead-pull, and cold-test measurements, correlating results with simulation.
• Develop scripts and computational tools to automate parametric simulation and optimization, and present results in design reviews.
• Iterate designs with ATLAS and the broader team, review its outputs before they proceed to fabrication or testing, and promote a proactive safety culture.

QUALIFICATIONS

Required

• Master's degree in Physics, Electrical Engineering, or a related discipline; PhD preferred.
• 3+ years of RF cavity, high Q filter, or accelerator design experience, or 7+ years of broader professional experience in RF or electromagnetics.
• Background in 3D electromagnetic design of resonant cavities using CST, HFSS, or equivalent eigenmode and frequency-domain solvers.
• Working knowledge of RF superconductivity and cavity figures of merit: quality factors, surface resistance, geometry factor, R/Q, shunt impedance, and surface-field optimizations.
• Understanding of beam-cavity interactions, including beam loading, coupling, and higher-order modes.
• Ability to work across disciplines and produce clear design reports, specifications, and presentations.

Preferred

• Experience designing SRF cavities (elliptical, spoke, half- or quarter-wave) for proton or electron linacs, including couplers.
• Experience with multipacting and wakefield codes and coupled RF-structural simulation.
• Experience with RF measurement and tuning (network analyzers, bead-pull, field flatness) and cold testing of SRF cavities.
• Experience with Python or MATLAB scripting, parametric optimization, or AI-assisted engineering workflows, including physics-based validation of computational outputs.

BENEFITS

We offer health, dental, and vision insurance.

LOCATION & WORK POLICY

This role is fully in person in Austin, Texas. Our facility is located next to Austin Airport.