Commissioning of Pegasus-III CODAC and Power Systems*

Pegasus-III is a new ultralow-A ST providing a dedicated US experiment for comparative solenoid-free startup studies. A distributed communication, data acquisition, and control (CODAC) system has been commissioned alongside upgraded power systems supporting the enhanced B_T, poloidal field sets, and helicity injection systems for its first physics research campaign. Presently comprised of ~50 physical and ~35 logical subsystems, Pegasus-III CODAC provides in-pulse timing, triggering, and feedback control of electromagnets and helicity injectors; intra-pulse shot cycle management, capacitor bank energy management (8.5 MJ), facility health, and safety monitoring; and data archival in high-reliability storage and relational databases. 31 4 MVA (900 V, 4 kA) buck converters in parallel sets drive up to 7 PF coil loads (I_PF ≤ 16 kA/turn) and 4 helicity injector arc systems for 50 ms and the TF (I_TF ≤ 48 kA/turn, 1.15 MA) for 100 ms. Four multi-level buck converters (MLBC) provide up to 40 MVA (1800 ± 900 V, 4 kA) of injector bias power for 50 ms. During commissioning, the power systems were used to: test the construction of new divertor coil assemblies and validate stress modeling employed in their design; drive all PF coils to their rated current and pulse length; validate the new TF magnet construction; drive ~0.3 MA with a temporary internal coil to calibrate magnetics and wall current models; and qualify the MLBC systems for physics operation.