Magnet Structure and Preload
Steel case and mechanical preload hold REBCO in a controlled strain state so electromagnetic loads never reach the brittle conductor unmanaged.
Structure does the load-bearing
REBCO tolerates tension along its length but is fragile in transverse tension and shear. The magnet structure — coil case, wedged center column, and preload — is designed so the conductor sees a controlled, mostly-tensile strain and the metal carries everything else. Preload keeps joints and turns in compression during cooldown and operation so gaps do not open.
Preload and cooldown
The magnet is assembled warm and operated near cryogenic temperature. Differential thermal contraction between conductor, insulation, and steel must be designed so that at operating temperature the intended preload is present. Get it wrong and either the structure over-compresses the conductor or turns go slack and move under load, both of which threaten the REBCO.
- Coil case: reacts hoop and overturning loads.
- Wedged/bucked center column: reacts centering force.
- Preload: maintains compression through cooldown and pulsing.
- Insulation: transmits load while surviving radiation.
Why it is a system problem
Structure, preload, cooldown, and radiation-driven property changes are coupled over the machine's life. Insulation that stiffens or embrittles under neutron dose changes the load path years into operation. The breeder's structural design is validated against the full life, not just first cooldown, which is why the magnet and center-post lifetime pages reference each other.
Life-cycle validation
Preload and structural adequacy are validated not just at first cooldown but across the machine's operating life, because insulation stiffness and material properties drift under accumulated dose. A load path that is sound when new can shift years later, so the structural case is checked against end-of-life properties as well as start-of-life ones.
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.