NSTX-U detects disruption-driven electromagnetic loading using diagnostics that measure halo currents and the evolving plasma current during the current quench. Halo currents flow poloidally through the edge plasma and close through plasma-facing components, producing large forces on the divertor and vessel. A key strength of this diagnostic set is its current-path coverage: Rogowski coils track the global current evolution (and, when available, asymmetry proxies), while shunt-tile halo current sensors provide sector-resolved measurements of current flowing through divertor structures.

Together, these measurements quantify halo current fraction, toroidal asymmetry, and timing relative to the disruption sequence (thermal quench, current quench, and vertical displacement events). They support force reconstruction, machine protection studies, and validation of disruption modeling and mitigation performance.

Instrumented divertor tiles with shunt resistors measure current flowing through plasma-facing components during disruptions and VDEs. The array provides sector-resolved halo current and enables inference of toroidal asymmetry and peaking (n=1 side load proxies).

• Measures: tile/sector currents, summed halo current, asymmetry metrics
• Typical use: halo fraction, onset timing, toroidal peaking / imbalance
• Best paired with: global Ip (Rogowski), magnetics, equilibrium timing

Rogowski coils measure the evolving toroidal plasma current and provide high-time-resolution timing of the current quench. Where multiple coils or processed channels are available, the set can also support disruption event identification and comparisons to halo current onset.

• Measures: Ip and related derived signals (e.g., dIp/dt)
• Typical use: CQ timing, quench rate, correlation with halo current
• Best paired with: HALOCUR, magnetics, disruption flags / event lists