PA20: A new SANS and GISANS project for soft matter, materials and magnetism

This article presents the new Small Angle Neutron Scattering (SANS) instrument PA20 which will replace the PAXE instrument at LLB-Orphee. SANS is well-known to be especially well adapted to research in soft matter, materials and nanosciences and SANS is particularly powerful in the studies of complex systems, with isotopic labeling and contrast variation method, but also for large-scale structures (magnetic or not). PA20 is part of the LLB instrumental upgrade program CAP2015. PA20 will not only maintain LLB's capabilities in SANS, but also considerably extend them in terms of SANS for magnetism with a polarized neutron option and Grazing Incidence SANS (GISANS), with an improved dynamical Q-range. The total length of PA20 will be 40 m, including a 19 m collimation length, a 20 m detector tank containing high-resolution/high-efficiency XY detectors, and a casemate containing a monochromator (velocity selector lambda = 0.3 - 2 nm), a chopper system for Time-of-Flight (TOF) mode, a polarizer and an RF spin flipper. PA20 will allow faster measurements, with single-shot access to a wider range of scattering vectors, on possibly small samples (few mm in size). In addition, polarized neutrons will enable magnetic studies in both SANS and GISANS configurations. Studies of nanostructured surfaces and interfaces (deposited or embedded nano-objects), magnetic domain formation, multilayered materials or magnetic thin films through specular and off-specular signals will be possible through GISANS setups. The versatility of PA20 should contribute to both enlarge the neutron user community, especially in expanding areas like nanosciences, and offer improved services for users in the years to come.