1. Study of a Superconducting Shield for a Transverse Polarized Target for PANDA 2012 Paris Helmholtz Institut Mainz Bertalan Feher, PANDA EMP Session Status Report

2. Outline 1.Motivation 2.Integration into PANDA 3.Simulation 4.Results 5.Further Steps 2

3. 3 Transverse Polarization of the Target We are interested in the reaction Form Factors in the time like region are complex The single spin polarization observable Transverse target polarization as high as possible Allows the access to the relative phase with the scattering angle Θ

4. 4 The PANDA Detector at FAIR Darmstadt (GSI) Transverse polarized target needed Detector at HESR (High Energy Storage Ring) 1.5 to 15 GeV/c High luminosity Fixed Target experiment 4π-Acceptance Energy, momentum measurement 1 T - 2 T Solenoid

5. 5 The PANDA Detector at FAIR Darmstadt (GSI) Detector at HESR (High Energy Storage Ring) 1.5 to 15 GeV/c High luminosity Fixed Target experiment 4π-Acceptance Energy, momentum measurement 1 T - 2 T Solenoid B

6. 6 The PANDA Detector at FAIR Darmstadt (GSI) Transverse Field Detector at HESR (High Energy Storage Ring) 1.5 to 15 GeV/c High luminosity Fixed Target experiment 4π-Acceptance Energy, momentum measurement 1 T - 2 T Solenoid B

7. 7 Fieldmap of the PANDA Solenoid B Ext = 1 T = 10000 Gauß Longitudinal field z-Component is homogeneous to the order of 10 -4

8. 8 Advantage of a Superconducting Shield Meißner-Ochsenfeld Effect in a Superconductor Passive shield Compensation of the longitudinal flux Small material budget No power supply: –No contact (no heat) –No wire from power supply No static forces, self adjusting (no torque)

9. 9 Solenoid Model current goes into slide current comes out of slide One layer of a current carrying wire: Create more layers to reach wall thickness:

10. 10 We need: 1.Determine geometry 2.Use parametrization in Biot-Savart 3.Substract result from extern field 4.B=B Ext -B Ind Calculation of Residual Magnetic Field (critical) current density of a superconductor

11. 11 Model Used for Simulation Simulation with Mathematica (Biot-Savart Law) using Bean- Model critical current density * Fagnard, Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow Cylinders in axial magnetic fields Bi-22212 Critical temperature T C 92 K Operational temperature T10 K Wall thickness5 mm Length80 mm Radius8 mm Compensated flux10 000 Gauß Experimentally Achieved:

12. 12 Aspect ratio L/R10 Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Length L80 mm Radius R8 mm Wall thickness d5 mm Induction at centre 9990 Gauß Induced Flux

13. 13 Numerical Stability Comparison of 6x6 field points ( ) and Winding/mm = 2 to –11x11 field points –Winding/mm = 10/mm Aspect ratio L/R10 Windings / mm2/mm Current I (density J C ) 41.116 A (16446 A/cm 2 ) Length L80 mm Radius R8 mm Wall thickness d5 mm Induction at centre 9990 Gauß

14. 14 Numerical Stability Windings/mm = 10/mm 11x11 Points

15. 15 Geometry of the Shielding Material Budget Influence by inhomogeneity: –Depolarization, Tracking Beam pipe + Target Pipe

16. 16 Geometry Used for Simulation a) Cylinder without the holes in the wall b) Cylinder with gap for the target pipe 1. L = 120 mm, R = 60 mm 2. L = 100 mm, R = 10 mm 3. Variable L, R, gap

17. 17 1. a) Tube without gap Aspect ratio L/R2 Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Length L120 mm Radius R60 mm Wall thickness d5 mm

18. 18 1. a) Tube without gap: Residual Flux At target region: B=B Ext -B Ind Tube and surrounding area:

19. 19 1. b) Tube with gap = 8 mm Aspect ratio L/R2 Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Length L128 mm Radius R60 mm Wall thickness d5 mm

20. 20 1. b) Tube with gap: Residual Flux At target region: B=B Ext -B Ind Tube and surrounding area:

21. 21 2. a) Small tube without gap Aspect ratio L/R10 Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Length L100 mm Radius R10 mm Wall thickness d5 mm

22. 22 2. a) Small tube without gap: Residual Flux At target region: B=B Ext -B Ind Tube and surrounding area:

23. 23 2. b) Small tube with gap = 8 mm Aspect ratio L/R10 Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Length L108 mm Radius R10 mm Wall thickness d5 mm

24. 24 2. b) Small tube with gap: Residual Flux At target region: B=B Ext -B Ind Tube and surrounding area:

25. 25 Variation of Length and Radius, Gap Aspect ratio L/RVariable Gap0, 4, 8, 12 mm Windings / mm2/mm Current I (density J C ) ca. 41 A (16446 A/cm 2 ) Wall thickness d5 mm

26. 26 Variation of Length and Radius No Gap Residual Flux at Target (x =0, z = 0) 1.B < 0 is not physical 2.Absolut offset 3.3% Overcompenstation due to deficiency of model 4.Numerical calculation is correct 5.Best compensation L/R = 10

27. 27 Variation of Length and Radius, 4 mm Gap Residual Flux at Target (x =0, z = 0)

28. 28 Variation of Length and Radius, 8 and 12 mm Gap Residual Flux at Target (x =0, z = 0)

29. 29 Conclusion and Outlook First idea is a shielding of the PANDA solenoid with a superconducting tube Feasibility depends on: residual magnetic field, inhomogeneity, material budget Simulation with Bean-Model Compenstated flux depends on radius, length and the gap Direct calculation of induced current in the superconductor Include field into PANDA simulations to verify momentum resolution Experimental verification of the superconducting tube Simulation and measurement of a tube with a transverse holding field