2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49330The physics case for a possible fixed target polarized nucleon-nucleon collision experiment at HERA is described. The experiment named HERA-N could be realized using an internal polarized gas target in the HERA polarized/unpolarized proton beam. A wide spectrum of nucleon spin structure problems could be investigated and the experiment would constitute a fixed target complement to the RHIC spin physics program with competitive statistical accuracy.18 pages, Invited talk presented by W.-D. Nowak at the Workshop `Polarized Protons at High Energies - Accelerator Challenges and Physics Opportunities', DESY Hamburg, 17-20 May, 1999High Energy Physics - Phenomenologytext