GEM magnet options: preliminary report

A strawman muon detector geometry is used in the evaluation of various designs for the GEM magnet. The muon track resolution for the EoI baseline magnet (superconducting solenoid with thick iron end poles) is compared with an option with modified end poles (the LoI baseline), and with a uniform field. Design magnet options to improve muon resolution at small angles (1.5 {le} {eta} {le} 2.5) include the replacement of the iron poles with a superconducting ``bottle`` solenoid and/or the addition of conical shells (wedges) of iron for field shaping. Because of concern about the far (surface) field, shielded variants which use either a superconducting outer solenoid or an iron flux return are also presented.