What are the responsibilities and job description for the Mechanical Engineer – SRF Cryomodule position at Subcritical Systems Inc?
ABOUT SUBCRITICAL SYSTEMS
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 meltdown 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 mechanical design of Subcritical Systems' SRF cryomodules - the structures that hold superconducting cavities at 2 K precisely aligned to the beamline. The scope spans thermal design (heat-load budgets, thermal shields and intercepts, low-conductance mechanical support systems, and vacuum systems), precision alignment from 293 to 2 K, cleanroom and cold-mass assembly, and the mechanics which define operating performance. You will work closely with SRF, cryogenic, RF, vacuum, and manufacturing engineers to carry cryomodules from concept through assembly, cold testing, and operation.
You'll also feed your engineering judgment, physical constraints, and test data into ATLAS, our internal AI-assisted engineering platform, and review its outputs before they reach detailed design or the shop floor.
KEY RESPONSIBILITIES
- Own the cryomodule's mechanical design – vacuum vessel, thermal shields, cold-mass supports, and interconnects – from concept through detailed drawings.
- Perform and review thermal analyses to set static and dynamic heat-load budgets at 2 K, 4 K, and 40–80 K, and design shields, MLI, thermal intercepts, and supports to meet them.
- Participate in the 3D FEA characterizing device performance: modal frequencies, physical couplings, and vacuum systems.
- Define alignment requirements and methods for the cavity string, and verify component positions through assembly, cooldown, and transport.
- Develop cleanroom and cold-mass assembly procedures, tooling, and fixtures.
- Support cryomodule transport, cold testing, and operation while feeding measured heat loads, alignment, and performance data back into future designs.
- Translate validated models and test data into ATLAS, review its design outputs before they proceed to fabrication or testing, and promote a proactive safety culture.
QUALIFICATIONS
Required
- Bachelor's degree in Mechanical Engineering or a related discipline; master's degree preferred.
- 4 years of mechanical engineering experience on cryogenic, vacuum, or precision accelerator hardware, or 10 years of broader engineering experience with substantial relevant exposure.
- Working knowledge of low-temperature heat transfer, thermal contraction, and cryogenic material properties.
- Ability to perform and interpret thermal, structural, and modal analyses (e.g., ANSYS, COMSOL).
- Hands-on experience with precision assembly, alignment, and metrology (laser tracker, CMM).
- Demonstrated ability to produce clear specifications, design reports, and procedures.
Preferred
- Experience designing, assembling, or testing SRF cryomodules or dressed SRF cavities.
- Familiarity with SRF cavity properties and RF measurements and coupled RF-mechanical simulation (CST, HFSS, ANSYS, COMSOL).
- Experience applying ASME BPVC Section VIII and B31.3 to pressure vessels and piping systems, and moving prototype hardware into repeatable production.
- Familiarity with computational design tools, simulation-driven optimization, or AI-assisted engineering workflows, including evaluating their outputs with sound engineering judgment.
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.