Cryogenic and Vacuum Feedthrough Interface
Every sensor and actuator wire crossing the cryostat or vacuum boundary passes a feedthrough; the interface owns integrity, isolation, and interlocks.
Crossing the boundary
Signals and power must cross two hostile boundaries: the vacuum wall and the cryostat that keeps the REBCO magnets cold. Every diagnostic wire, coil lead, coolant line, and gas line passes a feedthrough. This interface owns the integrity of those crossings — leak-tightness, thermal isolation, and electrical continuity — on both machines.
What it monitors and enforces
- Vacuum integrity: pressure, leak rate, feedthrough seal status.
- Cryogenic: feedthrough temperature and heat-leak budget.
- Electrical: continuity and isolation of instrument and power leads.
- Interlock: vacuum-boundary faults gate fueling and beam actuation.
| Vac ok | Cryo ok | Fueling/beam enable |
|---|---|---|
| 0 | 0 | 0 |
| 0 | 1 | 0 |
| 1 | 0 | 0 |
| 1 | 1 | 1 |
The feedthrough interface is an interlock source more than an actuator: a vacuum-boundary fault immediately gates the fueling and beam interfaces closed, and a cryostat heat-leak excursion raises the magnet-protection posture. These interlocks are enforced at L1 so no supervisory layer can override a breached boundary.
# feedthrough interlock (L1)
if vac_leak > leak_max or seal_fault:
close_all_fueling(); notch_beams() # fail-safe
if cryo_heatleak > budget:
raise_magnet_protection_posture()The feedthrough count is large on both machines because every one of the 60+ diagnostic channels and every coil lead, coolant line, and gas line needs its own crossing. Each crossing is a potential leak path and a potential heat leak, so the interface tracks them individually rather than as a lumped boundary; a single degrading seal is localized to its feedthrough and scheduled for service before it forces a shutdown.
Owner: L1 for the interlock; L2 for monitoring transport. Calibration covers leak-rate reference and thermometry, both traced to reference standards and drift-tracked. This is a shared interface across breeder and burner. Design-and-simulation specification, validated before hardware commissioning; no operational claim is implied ahead of FOAK first tritium (~2030).