Hadron Polarimetry Systems for the Electron-Ion Collider: Challenges and Solutions

The Electron-Ion Collider (EIC) requires hadron beam polarizations >70% with ≤1% relative uncertainty, demanding significant advances in polarimetry technology. This presentation covers the absolute polarimetry systems being developed to meet these stringent requirements.

We examine absolute hadron beam polarimetry using polarized hydrogen jet targets for proton beams, with the same principles applicable to other ion species. The EIC's enhanced beam conditions - 10× higher bunch frequencies and increased currents - create beam-induced depolarization risks that necessitate operating at higher magnetic holding fields (~400 mT vs current 120 mT) to maintain target stability and achieve sub-percent systematic uncertainties.

For polarized ³He⁺⁺ beams, we present a novel absolute polarimeter based on cryogenic ³He atomic beam sources achieving >95% polarization. The system uses ³He-³He elastic scattering, with engineering challenges including 1K cryogenic operation, quadrupole magnetic focusing, and integration with existing EIC infrastructure.

Advanced spin manipulation techniques are discussed, including novel RF Wien filter designs for continuous spin flipping without orbit distortion, spin-tune monitoring systems for real-time feedback, and selective bunch-by-bunch polarization control enabling sophisticated experimental configurations.

We address integration challenges within EIC interaction regions, and coordination between multiple polarimetry systems to provide comprehensive polarization characterization throughout collision stores.

The methodologies developed provide a framework for optimizing polarized target operation across all planned ion species, establishing the foundation for achieving the EIC's ambitious polarization goals.