Optics simulations of the 5 MeV NPBSE FOX telescope

The far-field optics experiment (FOX) is a proposed design for the neutral particle beam space experiment (NPBSE) program. This 425 MHz straight beam line includes a 4.3 meter large-bore telescope. It is designed to deliver an 8 mA, 5 MeV neutral hydrogen beam with a transverse divergence of approximately 30 micro-radians to a target space vehicle (TSV) located up to 5 km away. We present zero current simulations, made with Grumman´s TOPKARK code, of the telescope optics and the resulting 5 km target footprint. These simulations demonstrate the need for momentum compaction to minimize chromatic aberrations and for the careful use of octupoles to correct geometric aberrations. TOPKARK uses a novel line dipole model for the large-bore, combined function telescope objective lenses, constructed with rods of permanent magnet material, proposed for use in the FOX. We describe this model and its effect on the dynamics