Cryogenic Cooling Model
The cryogenic system keeps the REBCO magnets cold enough to stay superconducting despite nuclear and ambient heat loads.
Keeping the magnets cold
REBCO only superconducts below a critical temperature that depends on the field it carries. The cryogenic cooling system's job is to hold the magnets safely below that limit at all times, removing every watt of heat that leaks in or is generated within. If the temperature rises too far, the magnet quenches.
Where the heat comes from
- Radiant and conducted heat leaking in from the warm surroundings.
- Nuclear heating from neutrons that reach the magnets despite shielding.
- Heat from joints and current leads carrying power into the cold mass.
- Any resistive heating from imperfect superconductivity.
The higher-temperature advantage
One reason REBCO is attractive is that it superconducts at higher temperatures than older conductors, so it can be cooled with less demanding refrigeration. Higher operating temperature also means more margin: the magnet can absorb a little more heat before reaching its critical temperature. This margin is part of what makes high-field REBCO magnets practical rather than merely possible.
The cryostat and cooling loop
The cryostat provides the insulating vacuum around the cold mass, and the cooling loop, coolant circulated through the coils and thermal shields, carries heat out to the refrigeration plant. The two work together: the cryostat minimizes the heat that gets in, and the cooling loop removes what remains. On Hyperion the neutron shield further reduces the nuclear heat load on the magnets.
In the model
Cooling is shown through the cryostat boundary and the cooling connections to the coils. See the cryostat that insulates the cold mass and the quench protection that acts if cooling margin is lost.