development of a superconducting shield for a transversely polarized target for the panda-experiment...
TRANSCRIPT
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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
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Timelike Electromagnetic Form Factors
Sapcelike and timelike region intimately connectedPANDA unprecedented luminosityAntiproton annihilation opens a new window to Precision electromagnetic (EM) probe hadron structure observables
Spacelike: real Timelike: complex Polarisation
q2 < 0 (GeV/c)2 q2 > 0 (GeV/c)2
time time
q2
q2 = 0 /GeV/c)2
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WP3: transversely polarised Target in PANDA
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WP3: transversely polarised Target in PANDA
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transversely polarised Target in PANDA
•PANDA Solenoid: 2T longitudinal field
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transversely polarised Target in PANDA
•PANDA transversely polarized target: shield 2T longitudinal field
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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
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Principle: Superconducting Shield (passive)
• Induced current in superconducting tube• Surface current• Expellation of magnetic flux
ThicknessOf Supcerconductor
Superconductor with no current
Superconductor with current at criticalcurrent density
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Advantage: Superconducting Shield (passive)
• Compensation of the longitudinal flux
10 000 Gauß (1 Tesla)• Small material budget• Passive shield• No power supply:
No wire from power supplyNo contact (no heat)
• Self adjusting •no torque due to misalignment •maximal shielding
• Quench behaviour ?
• Material choice critical:•high critical current density•Operating point (temperature)
• Induction in an external magnetic field• High critical current throughout the whole
material
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Material choice:
Bulk Properties
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Material choice:
Our limitfor 1T
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Advantage: Superconducting Shield
YBCO Characteristics (melt-textured)
Sintered ca. 1 order of magn. lower(no data at 4.2 K)
Sintered 85 -90 %
Radiation Length: X0 = 1.9 cm at 6.38 g/cm3Radiation 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
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Advantage: Superconducting Shield
Fagnard, Shielding efficiency and E(J) characteristics measured on large melt cast Bi-2212 hollow Cylinders in axial magnetic fields
BSCCO Parameter Value
Critical Temperature 92 K
Density 6 g/cm3
Young's Modulus (E-Modul) Longitudinal (approx. transv.)
55 GPa
Critical Current Density Jc (10 K, 1T) 16 kA/cm2
BSCCO Characteristics (melt-textured)
Radiation Length: X0 = 1.5 cm at 6 g/cm3 10% X0 = 1.5 mm
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Induced field calculation: Solenoid, Biot-Savard
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Induced field calculation: Solenoid, Biot-Savard
4 mm Gap
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Induced field calculation: Solenoid, Biot-Savard
50 mm Gap, (One Segment left out)
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Transversely polarised Target in PANDAFinite Element Analysis with OPERA
Current Distribution in SC-tube
Model in OPERA: solid tube
Model in OPERA: solid tube with bore
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Transversely polarised Target in PANDATest in cryostat in Bonn
YBCO-123 Critical temperature TC
92 K
Operational temperature T
1.4 K
Wall thickness 5 mm
Length 150 mm
Radius 50 mm
Compensated flux at least 40 000 Gauß
With (very) friendly support from H. Dutz and S. Runkel from U. Bonn, Phys. Inst.
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Shielding tests at 1.4 K and 77 K
II. with bores(Nov. 2013)
I. without bore(Jan. 2013)
Transversely polarised Target in PANDATest in cryostat in Bonn
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Measurements at 1.4 KTest results: Shield outer field down to below 0.4%
January 2013
ThicknessOf Supcerconductor
Superconductor with no current
Superconductor with current at criticalcurrent density
5 mm thickness for 4 T2.5 mm thickness for 2T
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Measurement in Liquid Nitrogen (77K)Test results: Shield about 20% of the outer field
January 2013 Measurement in Liquid Nitrogen
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November 2013
Measurements at 1.4 KTest results: (Almost) no shielding observed
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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)