ORNL High Flux Isotope Reactor GP-SANS Polarizer The High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) is a high-flux research reactor that, in addition to isotope production, serves as a steady-state neutron source for a suite of neutron scattering instruments. Among these, the General-Purpose Small-Angle Neutron Scattering (GP-SANS) instrument is being upgraded to incorporate incident beam polarization capabilities. This enhancement will enable spin-resolved SANS measurements, allowing for the separation of nuclear and magnetic scattering components and facilitating studies of magnetic order, spin textures, and correlated spin structures. A critical component of this upgrade is the integration of a polarizing cavity, which utilizes magnetized supermirrors or transmission-based polarizers to produce a beam of neutrons in a well-defined spin state prior to their interaction with the sample. This capability is essential for conducting polarization analysis and advanced techniques such as polarization contrast measurements and vector-magnetic SANS. This specification defines requirements for materials of construction, fabrication, inspection, and delivery to the Company of a complete polarizing cavity and magnetic housing assembly. The polarizing cavity and magnetic housing assembly shall be installed at the GP-SANS instrument.