Sr3Ru2O7 is an unusual layered oxide metamagnetic metal. It has been known for some time that the application of a large magnetic field (~8 T) perpendicular to the RuO2 planes induces a new "A" phase at low temperatures (T<1.5K). The A phase has thermodynamic and electronic transport anomalies which define its boundaries. It also has anisotropic electronic properties. We have recently used WISH to identify the A phase as spin density wave (SDW) order and discover a neighbouring "B" phase at slightly higher field. Here we propose to: (i) map out the temperature/field phase boundaries of the A & B phases in detail and measure the T-dependence of the order parameters as a function of field (both are difficult by other techniques); (ii) determine whether electronic anomalies for magnetic fields applied within the RuO2 planes also correspond to SDW order.