Optimized Packing Fraction Determination in Solid Polarized Targets

The accurate determination of the packing fraction, the fraction of polarized material within the target cell, is critical for reducing systematic uncertainties in polarized scattering experiments. The packing fraction directly affects the normalization of polarized observables and the extraction of spin-dependent asymmetries. To address the current limitations in target composition uncertainty, the University of Virginia Spin Physics Group is developing optimized, high-precision techniques for both pre-beam and in-beam measurement of the packing fraction. This work is a critical step toward achieving the next generation of precision in spin physics. Our approach is two-fold: First, we are refining calibration and measurement procedures at our home facility using representative target materials to establish optimal density characterization prior to installation. Second, we are implementing novel in-situ diagnostic methods suitable for experimental conditions, which monitor changes in material compaction caused by environmental and cryogenic factors after target loading. These combined developments aim to minimize uncertainty propagation from the target composition to the extracted observables, thereby ensuring greater reliability and higher precision in upcoming polarized target experiments at Fermilab and Jefferson Lab.