US neutrino factory studies

The design and simulated performance of a second feasibility study are presented. The efficiency of producing muons is ≈0.17 μ/p with 24 GeV protons. This study was sponsored by the BNL Director, with BNL site specific driver and layout. It was a follow on to the First Study (http://www.fnal.gov/projects/muon_collider/nu-factory/fermi_study_after_april1st/) sponsored by the Fermilab Director, with Fermilab site specific driver and layout, and was the main US collaboration conceptual effort during the past year. Other studies, and technical work by the collaboration is reported in other papers.