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Dressing Coil Prototype

Riccardo Schmid Dressing Coil prototype construction and mapping. Dressing Coil Prototype. nEDM Meeting Nov. 2 nd , 2007 M.I.T./Bates. Dressing Coil Issues. Current density distribution on FM shield (Unshielded). Oscillatory B field induces eddy currents on FM Shield

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Dressing Coil Prototype

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  1. Riccardo Schmid Dressing Coil prototype construction and mapping Dressing Coil Prototype nEDM Meeting Nov. 2nd, 2007 M.I.T./Bates

  2. Dressing Coil Issues Current density distribution on FM shield (Unshielded) Oscillatory B field induces eddy currents on FM Shield Necessary to limit the dissipative heating to < 1W It is possible to shield the B field using additional Active Shield Coils. Important to keep B field uniformity high in the measurement cells. Cryoperm 1 mm N=34 Cosθ saddle coils FM Shield Active Shield Finite element analysis using ELEKTRA (Vector Fields) from ASU (R. Alarcon, S. Balascuta ) Demonstrate Active Shield efficiency by building a prototype. Dressing Coil

  3. Active Shield 3D Model Shown: 5 Active Shield contour pairs

  4. UPDATED Power Dissipation Power dissipated on the FM shield can be estimated to be The effectiveness of the Active Shield increases as more windings are added to the shield. NOTE: the data shown are from calculations for the new nEDM coils geometry R1 = 50cm L1 = 300cm (N=34 Cosθ) R2 = 55.9 cm L2 ~ 400 cm

  5. Prototype Construction Al Cylinder Inner Dressing Coil: 8-turn Cosθ coil R1 = 8.75 cm L1 = 49.6 cm Outer Active Shield: Contour coil R2 = 9.69 cm L2 ~ 64 cm Active Shield outline printed on poster paper and wrapped around Al cylinder. Cu wires glued on paper. Posterprintout Active Shieldwith 5 contour coil pairs Cu wires glued on paper

  6. INSIDE FIELDPrototype Mapping Mapping field inside coils (Z axis) Inner Dressing Coil (Cos coil) with a 1.5A current (fixed) Outer Active Shield (Contour Coil) variable current B field mapping inside cylinders for comparison with calculations. Only x component of the field measured inside the coils (By << Bx inside) z y Nominal B field in x direction x

  7. Inner Field mapping INSIDE FIELDPrototype Mapping Inner Dressing Coil: 8-turn Cosθ coil R1 = 8.75 cm L1 = 49.6 cm Outer Active Shield: Contour coil R2 = 9.69 cm L2 < 64 cm Note: Mapping of x component of B field

  8. OUTSIDE FIELDPrototype Mapping Inner Dressing Coil (Cos coil) with a 1.5A current (fixed) Outer Active Shield (Contour Coil) variable current Field mapping outside to measure shielding effectiveness at the FM shield radius. Measurements on 1/8 of the area of FM surface: R3 = 13cm L3 = 60 cm ( Inner: R1 = 8.75 cm and L1 = 49.6 cm) ( Outer: R2 = 9.69 cm and L2 < 64 cm) Measure Bx and By separately Interested in <|B|> at FM shield radius

  9. Normalization Current in inner dressing coil fixed at 1.5A Current in outer Active Shield varied from 0A to -1.4A Field at center of coils changes with Active Shield current – Linear Dependence Need to normalize (scale) outside field measurements so that field at center is the same for all currents.

  10. Outside Field Mapping Average Magnitude of Bx outside Dressing Coils at a radius of 13cm Normalized to the value of Bx for I2=0

  11. Outside Field Mapping Average Magnitude of By outside Dressing Coils at a radius of 13cm Normalized to the value of Bx for I2=0

  12. Conclusions • Mapping of prototype shielding agrees with calculations • Demonstrated one approach to the construction of Active Shields on printed paper • Field Uniformity • Test Dressing Fields with AC currents

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