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Bertold Fröhlich (PhD), Frank Maas, Luigi Capozza, Cristina Morales HIM/JGU

Development of a superconducting shield for a transversely polarized target for the PANDA-Experiment. Bertold Fröhlich (PhD), Frank Maas, Luigi Capozza, Cristina Morales HIM/JGU HPH2020 brainstorming meeting: „Dedicated Magnet Systems for polarized Targets “ .

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Bertold Fröhlich (PhD), Frank Maas, Luigi Capozza, Cristina Morales HIM/JGU

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  1. Development of a superconducting shield for a transversely polarized target for the PANDA-Experiment Bertold Fröhlich (PhD), Frank Maas, Luigi Capozza, Cristina Morales HIM/JGU HPH2020 brainstorming meeting: „Dedicated Magnet Systems for polarized Targets“. U. Bonn, 2014, January 21

  2. time time Timelike Electromagnetic Form Factors q2 < 0 (GeV/c)2 q2 > 0 (GeV/c)2 Spacelike: real Timelike: complex Polarisation q2 = 0 /GeV/c)2 q2 Sapcelike and timelike region intimately connected PANDA unprecedented luminosity Antiproton annihilation opens a new window to Precision electromagnetic (EM) probe hadron structure observables

  3. WP3: transversely polarised Target in PANDA

  4. WP3: transversely polarised Target in PANDA

  5. transversely polarised Target in PANDA • PANDA Solenoid: 2T longitudinal field

  6. transversely polarised Target in PANDA • PANDA transversely polarized target: shield 2T longitudinal field

  7. Requirements • Possible solutions: • Superconducting shielding solenoid (active) • Superconducting shielding tube (passive) • Material requirements: • High critical current density • Highest Temperature • Low material budget (for charged particles: 0.1 X0) • Manufacturer • Adaptable to geometry

  8. Principle: Superconducting Shield (passive) Superconductor with current at critical current density • Inducedcurrent in superconductingtube • Surface current • Expellation of magnetic flux Superconductor with no current Thickness Of Supcerconductor

  9. Advantage: Superconducting Shield (passive) • Induction in an external magnetic field • High critical current throughout the whole material • Compensation of the longitudinal flux • 10 000 Gauß (1 Tesla) • Small material budget • Passive shield • No power supply: • No wire from power supply • No contact (no heat) • Self adjusting • no torque due to misalignment • maximal shielding • Quench behaviour ? • Material choice critical: • high critical current density • Operating point (temperature)

  10. Material choice: Bulk Properties

  11. Material choice: Our limit for 1T

  12. Advantage: Superconducting Shield YBCO Characteristics (melt-textured) Sintered 85 -90 % Sintered ca. 1 order of magn. lower (no data at 4.2 K) Radiation Length: X0 = 1.9 cm at 6.38 g/cm3 Radiation Length: X0 = 1.9 cm at 6.38 g/cm3 Radiation Length: X0 = 2.2 cm at 6.38 g/cm3: 10% X0 = 2.2mm

  13. Advantage: Superconducting Shield BSCCO Characteristics (melt-textured) Fagnard, Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow Cylinders in axial magnetic fields Radiation Length: X0 = 1.5 cm at 6 g/cm3 10% X0 = 1.5 mm

  14. Induced field calculation: Solenoid, Biot-Savard

  15. Induced field calculation: Solenoid, Biot-Savard 4 mm Gap

  16. Induced field calculation: Solenoid, Biot-Savard 50 mm Gap, (One Segment left out)

  17. Transversely polarised Target in PANDA Finite Element Analysis with OPERA Model in OPERA: solid tube Current Distribution in SC-tube Model in OPERA: solid tube with bore

  18. Transversely polarised Target in PANDA Test in cryostat in Bonn With (very) friendly support from H. Dutz and S. Runkel from U. Bonn, Phys. Inst.

  19. Transversely polarised Target in PANDA Test in cryostat in Bonn Shielding tests at 1.4 K and 77 K I. without bore (Jan. 2013) II. with bores (Nov. 2013)

  20. Measurements at 1.4 K Test results: Shield outer field down to below 0.4% January 2013 Superconductor with current at critical current density 5 mm thickness for 4 T 2.5 mm thickness for 2T Superconductor with no current Thickness Of Supcerconductor

  21. Measurement in Liquid Nitrogen (77K) Test results: Shield about 20% of the outer field Measurement in Liquid Nitrogen January 2013

  22. Measurements at 1.4 K Test results: (Almost) no shielding observed November 2013

  23. Conclusion: • January 2013: Almost complete Shielding of outer field observed. • November 2013: No shielding observed. • Tube damaged due to hole drilling? Hall-probe damaged? • 10% minimum shielding expected (with values from 92K) • New measurements with a simple setup in Mainz (A. Thomas): • YBCO (sintered) is under Test • Tube with hole • Tube (thinner) no hole • SC-Solenoid for external field • Next Step: BSCCO. • Horizon 2020: • 1 PhD-Student • (Travel money)

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