Cryogenic Thermal Loads

The refrigeration plant is sized to the sum of nuclear heating, current-lead heat, joint losses, and cryostat leak — each fighting for the same capacity.

Adding up the load

The cryogenic plant must remove every watt that reaches the cold mass. Those watts come from several sources at once: nuclear heating from radiation that penetrates the shield, resistive heat from joints and current leads, and residual heat leak through the cryostat and its supports. The plant is sized to their sum with margin.

Why low temperature magnifies everything

Removing heat at cryogenic temperature is thermodynamically expensive: each watt at the cold mass costs many watts of room-temperature input to reject. This is why shield performance, lead design, joint quality, and cryostat insulation all matter so much — a watt saved at the cold mass is a large multiple saved at the wall plug.

• Nuclear heating couples cryogenics to the shield.
• Lead and joint heat couple it to the magnet design.
• Cryostat leak couples it to the insulation and supports.
• Every source competes for the same refrigeration capacity.

The thermal-load budget is what ties the magnet, shield, and cryogenics into one coupled system, and it is computed and reproducible like the rest of the design.

Steady versus pulsed

The budget separates steady loads, such as nuclear heating and cryostat leak, from pulsed loads, such as ramp-induced AC losses, because they stress the plant differently. Steady load sets baseline capacity while pulsed load sets the transient response, and both must be covered by the same refrigeration system with margin.

This page documents a design and simulation study, not a built machine. Construction begins Q2 2027; first-of-a-kind first tritium is targeted near 2030. Figures are computed, reproducible targets, not measurements.