Magnet Radiation Tolerance

Neutrons that reach the coils degrade insulation and superconductor over time, setting a dose budget the shield must protect.

The dose the magnet can take

REBCO magnets sit behind shielding, but no shield is perfect. Neutron and gamma dose accumulating in the coil degrades two things: the organic insulation, which embrittles and loses strength, and the superconductor itself, whose critical current falls with fast-neutron fluence. Both set an end-of-life dose budget.

Insulation is usually the limit

In most fusion magnets the organic turn insulation reaches its dose limit before the superconductor does. This makes the shield's job partly a magnet-life job: the shield thickness is sized to keep integrated insulation dose within limits over the planned operating life, trading against the scarce center-stack radius.

The compact-machine tension

• Thin center stack leaves little room for inboard shielding.
• Less shielding means higher magnet dose and shorter insulation life.
• More shielding pushes the machine larger, against the compact rationale.
• The center-post accepts scheduled replacement partly to relieve this tension.

Radiation tolerance ties the magnet, shield, and center-post into one coupled design. It is a central reason the breeder plans for component replacement rather than a sealed lifetime machine.

Monitoring dose over life

Because insulation typically reaches its limit before the superconductor does, the breeder tracks accumulated dose to the coil against its budget over operation, so end-of-life is a planned, monitored event rather than a surprise. This monitoring couples directly to the shield's performance and to the center-post replacement schedule that relieves inboard dose.

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.