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Dressing Coil Double Active Shield

Dressing Coil Double Active Shield. Riccardo Schmid Septimiu Balascuta. Chicago June 6, 2007. EDM Collaboration Meeting. Dressing Coil Issues. Dressing Coil induced currents on the FM shield create heating. Target < 1 W Possible to shield B field using Active Shield coils.

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Dressing Coil Double Active Shield

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  1. Dressing Coil Double Active Shield Riccardo Schmid Septimiu Balascuta Chicago June 6, 2007 EDM Collaboration Meeting

  2. Dressing Coil Issues • Dressing Coil induced currents on the FM shield create heating. Target < 1 W • Possible to shield B field using Active Shield coils. • Important to understand the effects of permeability of FM shield on heat dissipation. In earlier calculations, power dissipation per unit area was estimated calculating the average B field at the FM location and using a simple relation: This estimates use a constant permeability and do not include any saturation effect in the FM shield. (i.e. hysteresis curve not used)

  3. Heat Dissipation for a Dressing Coil I = 4.09 A ω = 2π • 2000Hz B0 = 1047 mG <|B|>=443mG P = 58.83 W Current density distribution on FM shield Agreement with earlier estimates: <|B|> = 429 mG P ~ 52 W Cryoperm 1 mm N=34 Cosθ saddle coils Finite element analysis using ELEKTRA (Vector Fields) from ASU (R. Alarcon, S. Balascuta )

  4. Active Shield • Inner coil produces dressing field (Cosθ) • Outer coil partially shields B field (Active Shield) N.B. An active shield can be built as a cosθ coil or with a more specific design. Multiple shields improve uniformity Field at center ~ 1 Gauss

  5. 34 Cosθ Dressing Coil (I1 const. = 4.09 A) 34 Cosθ Shield (R=50.5cm, L=286cm) Red: Full FM Effect Black: Earlier estimate Active Shield Effect For a field ~ 1Gauss in the center of measurement cell: P = 1.47 W Dissipated Analytic estimate: 7.7 W ( saturation in “hot” spots? ) Power dissipation with full finite element analysis. Comparison with previous estimates shows good agreement in the shielding effect.

  6. Effect on Uniformity Uniformity of B field in measurement cell important for storage time. The Uniformity of the B field improves under the influence of the FM shield. Furthermore, in the presence of the FM shield, an Active shield can improve the uniformity of the B field in the measurement cells.

  7. Contour Active Shields “Contour” Active Shields have been studied to further improve shielding factor. A finite element analysis for these types of Active Shields is necessary to understand the effect of FM shield on power dissipation and uniformity in cells. Analytic estimate of power dissipation using a contour active shield

  8. Conclusion and future work The finite element analysis of the FM shield shows good agreement with earlier estimates of power dissipation. The FM shield can improve the uniformity of the field in the measurement cells. Finite element analysis of FM shield effect for a Contour Active Shield configuration A prototype of the Dressing Coil + “Contour” Active Shield configuration will be built to prove the efficacy of the paired coil system. Upper Cryostat ASU magnet and shield design

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