1. Recent Magnetic Field Results Results from our automated field-mapper system Mappings of N = 8 and N = 40 coil –Coil field profile –Coil + Magnetic Shield field profile First successful (symmetric !) results using a new approach for mounting of the shield relative to the coil –Measurements at 300K and 77K October 2006 Collaboration Meeting B. Plaster z: coil axis y: vertical x: horizontal; field direction

2. N = 8 Coil (No Shield) 300 K

3. N = 8 Coil + Cryoperm Shield 300 K Reproduced same BAD (asymmetric) results from past ~2 years

4. TOSCA modeling indicated two possible sources of asymmetries: Welds on shield cylinders Mis-alignment of axis of coil relative to shield Cryoperm shield coil Sample TOSCA result Importance of co-axial alignment !! (see R. Alarcon TOSCA talk) welds

5. New idea “Wind” Metglas strips directly onto surface of cos  coil support frame Monolithic design guarantees co-axial alignment Also desirable as comes in 0.8-mil thick strips, few layers sufficient; thin shield desirable for Eddy current heating Metglas winding cos  coil support frame

6. N = 8 Coil + Metglas Shield Winding (3 layers) 300 K Periodicity ~5 cm (width of Metglas strips !)

7. N = 8 Coil + Metglas Shield Winding (3 layers) 77 K

8. N = 40 Coil (No Shield) 300 K

9. N = 40 Coil + Metglas Shield Winding (2 layers) 300 K If scale B 0 to 10 mGauss …  B x /  x ~ 2  10 -6 Gauss/cm

10. Summary Still to do: 77 K mapping of N = 40 coil + Metglas After this, first-round of Magnets and Magnetic Shielding R&D essentially complete Next round of R&D → Brad F. R&D talk

11. Office of Nuclear Physics  Pre-proposal: Cylindrical superconducting shield surrounding cos θ coil Mirror currents in superconductor result in worsening of field uniformity  Now: Ferromagnetic shield surrounding cos θ coil Mirror currents in ferromagnetic material result in improved field uniformity Impact of inner ferromagnetic shield  Results of initial TOSCA calculations confirmed improvement in field uniformity for cos θ coil + ferromagnetic shield prototype-sized coil dimensions cos θ coil only cos θ coil + shield