Fusion has always been the holy grail of energy - limitless, clean power that could transform civilization. Commonwealth Fusion Systems (CFS) is taking a uniquely pragmatic approach - use provem tokamak physics but make it practical in size with more powerful high-temperature supercondocting magnets (HTS) to achieve Q>1. There's only one problem: high-temperature supercondoctors are notoriously difficucult to work with. Also the operating temperature is over 300 degrees below freezing, there are 15+ kV potential differences between parts, and the magnets generate forces large enough to crush most materials (did I say there was only only one problem?).

In order to achieve commercial fusion, we need to build components that can operate in one of the harshest environments on planet Earth. During the summer, I worked on as many projects as I could get my hands on as part of the Magnet R&D team for the SPARC Central Solenoid Model Coil (CSMC). I detailed some of my work below:

CSMC Cooling Tube & Fiber Optic Cable Breakouts

I led design for the breakouts for supercritical helium cooling lines and fiber optic sensor cables in the Central Solenoid Model Coil (CSMC). This was a tightly constrained problem as most of the existing infrastructure was already finalized. The routes had to maintain voltage isolation, fit through existing structures, and leave space for insulation layup. I built everything in NX using expressions to control key dimensions - when manufacturing hit an issue, I could update the whole routing scheme quickly. We caught several integration problems this way before they became expensive fixes.

Cyclic Material Testing using Thermal Contraction

While waiting for parts, I tackled a mission-critical challenge the team was facing. We needed to cyclically test our superconducting cables under enormous compressive stress at cryogenic temperatures in order to ensure that they would remain functional during operation. The idea was to use thermal contraction itself to create the test forces, but modeling these interactions was causing delays.

I developed an analytical model that calculated forces from differential contraction and predicted material behavior at 77K. Going beyond standard analysis, I identified non-obvious failure modes around uneven cooling and local yielding that weren't part of typical checks. These potential failures needed explicit monitoring and design changes to prevent them. After modifying the design to account for these modes and validating safety margins, we got the green light to begin the experiment.

Testing Parts Under High Voltages, Cryogenic Temperatures, and Vacuum Conditions

I tested magnet components under combined cryogenic, high-voltage, and vacuum conditions. The core challenge was Paschen breakdown. When a free electron gets accelerated by the electric field between conductors, it collides with gas molecules in the way. If the electron has gained enough energy between collisions, it ionizes the molecule, releasing more electrons. This cascade of ionization creates a conducting path, leading to electrical breakdown.

The tricky part is that breakdown voltage depends on the product of pressure and distance (pd). At high vacuum, electrons don't hit enough molecules. At high pressure, electrons don't gain enough energy between collisions. But there's a sweet spot - a specific pd value where breakdown happens most easily. Our hardware had to operate safely across this entire range. However, the distance an electron needs to travel depends on the part geometry and insulation scheme, so everything needs to be rigorously tested. I designed test setups and insulation schemes for helium tubes, fiber cables, and helped developed a new insulation scheme for the electrical leads.

Component Integration

I created complex surface models in NX using 3D scan data from the as-built magnet components. The challenging part was ensuring my models could handle both the manufacturing variations we were seeing and the thermal contraction at operating temperatures. This meant carefully defining surfaces and transitions while maintaining precise tolerances. After completing the CAD work, I created detailed GD&T drawings and managed around $20k in purchase orders for precision machining.

What I Learned

Building magnets for fusion taught me three key engineering lessons. First, build flexibility into your designs early. It's impossible to predict all the manufacturing and integration challenges you'll hit. Second, test critical assumptions immediately. Physics simulations aren't enough when you're working with complex materials at extreme conditions. Third, document everything clearly. When you're working on projects of this scale, every design decision needs to be traceable and justified.

Most importantly, I learned that good engineering isn't just solving the physics problem. It's making sure your solution works in the real world under all conditions. At CFS, this meant designing parts that could be manufactured, assembled, and operated reliably in one of the most demanding environments we've ever created.