Principal Magnet Cryogenics Engineer

About Thea Energy:

Thea Energy is leveraging recent breakthroughs in stellarator physics and engineering to create a faster and simpler approach to commercializing fusion energy. The company is reinventing the stellarator using computer-controlled arrays of planar coils thereby replacing the intricate, complex modular magnets required in all other stellarator architectures. Thea Energy is on a mission to create a limitless source of zero emission energy for a sustainable future.

Position Overview:

We are seeking a Principal Magnet Cryogenics Engineer with over 10-15 years of industry experience to lead the complete program lifecycle—from concept through commissioning—of large-scale cabled High-Temperature Superconducting (HTS) magnet systems for next-generation fusion reactors.

In this role, you will hold end-to-end technical ownership for the cryogenic design, thermal-hydraulic modelling, forced-flow cooling distribution, and cryogenic integration of large-scale CICC (Cable-in-Conduit Conductor) or advanced stacked-tape HTS magnets. You will bridge megawatt scale cryogenic plant engineering with microscopic thermal-hydraulic magnet behaviour, leading multi-disciplinary teams through multi-million-dollar hardware deliverables.

Key Responsibilities:

• Program Lifecycle Ownership: Lead the complete lifecycle (Conceptual, Preliminary, Detailed Design, Qualification, Fabrication, Assembly, Commissioning, and Decommissioning) for large-scale HTS fusion magnet cryogenic systems.


• Cryo-Thermal System Architecture: Design, model, and validategaseous helium (gHe), or sub-cooled liquid nitrogen (sLN2) thermal management systems tailored to high-field HTS cabled conductors (stacked HTS conductors).


• Thermal-Hydraulic Modeling: Perform dynamic thermal-hydraulic analysis, transient load modelling (nuclear heating, AC losses, eddy currents, ramp rates), and margin calculations under operational and fault conditions.


• Quench & Fault Management: Own the cryogenic response strategy during quench events, including rapid helium expansion, overpressure relief sizing, burst disc integration, and thermo-mechanical stress containment.


• Large-Scale Infrastructure & Plant Integration: Define requirements for mega-watt class cryogenic plants, cold compressors, heat exchangers, sub-coolers, helium distribution boxes (valve boxes), and low-heat-leak transfer lines.


• Joints & Current Leads: Oversee cryogenic thermal management for high-current demountable or permanent HTS joints and conduction-cooled hybrid (HTS/LTS) gas-cooled current leads (60+ kA).


• Vendor & Subcontractor Governance: Manage major sub-contracts for large-scale cryogenic infrastructure, conductor fabrication, pressure vessels, and vacuum insulated systems (cryostats).


• V&V and Commissioning: Plan and execute full-scale cryogenic and high-current magnet test campaigns, leading cool-down, steady-state operation, quench mitigation, and warm-up procedures.

Required Experience:

• 10-15+ Years of Direct Experience in cryogenic engineering and thermal-hydraulic design for superconducting magnet systems, with a primary focus on HTS tape/cable architectures (REBCO/BSCCO).


• Large-Scale Fusion/Physics Program Delivery: Proven track record of ownership over large-scale (> $10M+) magnet work packages within fusion energy programs (e.g., W7x, ITER, JT60SA, KSTAR, DEMO) or major scientific facilities (e.g., CERN, FERMILAB).


• Cabled HTS Architecture: Demonstrated expertise in high-current (tens of kA) cabled HTS configurations (e.g., Cable-in-Conduit Conductors, stacked tape conductors) and forced-flow cooling strategies.


• Full Lifecycle Track Record: Experience taking at least one major superconducting magnet or cryogenic system from initial concept through initial cool-down and operational validation.


• Regulatory & Code Compliance: Deep familiarity with pressure vessel standards applied to cryogenic temperatures (ASME BPVC Section VIII, EN 13445, B31.3) and cryogenic safety standards (ISO 21010/CGA).

Technical Knowledge

• HTS Material Physics: Solid understanding of critical surfaces for REBCO coated conductors, strain sensitivity, thermal margin assessment, and current sharing regimes.


• Cryogenic Fluids & Thermophysical Properties: Mastery of low-temperature fluid dynamics (gHe, sLN2) using database tools.


• Transient Thermal Analysis: Deep domain knowledge of AC losses (coupling, hysteresis, flux creep) nuclear volumetric heating, heat-leak budgets, and conduction/radiation thermal shielding (MLI design).


• Instrumentation & Controls: Extensive knowledge of low-temperature thermometry (Cernox, TVO, optical fibers/FBG), cryogenic flow meters, pressure transducers, and cryogenic valve telemetry.

Skills & Competencies

• Computational Tools: Proficiency in finite element analysis (FEA) and thermal-hydraulic system modeling tools (e.g., COMSOL Multiphysics, ANSYS Thermal/CFD, MATLAB/Simulink).


• System Engineering & Requirements Flowdown: Capability to write clear system requirement documents (SRDs), interface control documents (ICDs), and lead major design reviews (CoDR, PDR, CDR).


• Leadership & Team Mentorship: Demonstrated ability to lead cross-functional engineering teams (structural, electrical, vacuum, systems) and mentor junior magnet/cryogenic engineers.


• Strategic Risk Mitigation: Mastery of FMEA, applied to cryogenic system failures, vacuum loss (loss of vacuum/L VAC), and runaway quench scenarios.

Company Benefits:

• Comprehensive health benefits (e.g. medical/dental/vision)


• Employee equity stock options


• 20 days PTO

$190,000 - $215,000 a year

It’s not necessary to meet all of the skillsets outlined above. Please feel free to send us a note and tell us why you would still be a great fit for this role or Thea Energy.

Diversity and Inclusion:

Thea Energy is an equal opportunity employer committed to creating a company of diverse backgrounds. By creating a diverse environment, we will bring new ideas and approaches to solving some of the world’s hardest (and most important) problems. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, gender, sexual orientation, gender identity or expression, national origin, family or marital status, age, disability, veteran’s status, or other characteristic protected by applicable laws and regulations.