Inductive pickup loops are one of the primary magnetic diagnostics in modern fusion concepts. To convert the voltage measurement from the inductive pickup loop to a measurement of magnetic field, the loop voltage must be integrated. While simple in principle, in practice several factors make the integration difficult, especially when there are large scale differences between the fast and slow magnetic signals or high-gain integrators are used for relatively long integration periods. The challenges can broadly be grouped into a few general areas: dynamic bandwidth resolution, input offset errors, droop, and long-term drift stability. Prior to this SBIR work, there were no integrators in the world that could meet the ITER integrator requirements for integration error and pulse duration.

Eagle Harbor Technologies (EHT) has developed a long-pulse integrator that exceeds the ITER specification for integration error and pulse duration. EHT is continuing the technology development originally started at Redmond Plasma Physics Laboratories (RPPL) and commercializing a final product that is suitable for long-pulse experiments, thus fulfilling a goal of the validation platform experiments.

During the Phase I program, EHT improved the RPPL short-pulse integrators, added a fast digital reset, and demonstrated that the new integrators exceed the ITER integration error and pulse duration requirements. In Phase II, EHT developed Field Programmable Gate Array (FPGA) software that allows for integrator control and real-time signal digitization and processing. In the second year of Phase II, the EHT integrator will be tested at a validation platform experiment (HIT-SI) and tokamak (DIII-D).

In the Phase IIB program, EHT will to continue development of the EHT integrator to reduce overall cost per channel. EHT will test lower cost components, move to surface mount components, and add an onboard Field Programmable Gate Array and data acquisition to produce a stand-alone system with lower cost per channel and increased the channel density. EHT will test the Phase IIB integrator at a validation platform experiment (HIT-SI) and tokamak (DIII-D).

The EHT integrator strongly supports validation platform experiments, whose programmatic goals critically rely on magnetic data to validate simulation results and extrapolate to burning plasma conditions. Additionally, the EHT integrator supports burning plasma experiments like ITER. The EHT integrator is currently the only integrator that meets or exceeds the ITER specifications over these long timescales. In addition, tokamaks from around the world have expressed great interest in the EHT integrator as they move toward longer-pulse operation to address scientific and engineering issues relevant to ITER. Beyond the fusion science community, integrators are used in high energy physics experiments, medical imaging instrumentation, and ion beam implantation.

Videos of long pulse integrator test for 1000 s and 7200 s.