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
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
WP3: transversely polarised Target in PANDA
WP3: transversely polarised Target in PANDA
transversely polarised Target in PANDA
•PANDA Solenoid: 2T longitudinal field
transversely polarised Target in PANDA
•PANDA transversely polarized target: shield 2T longitudinal field
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
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
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
Material choice:
Bulk Properties
Material choice:
Our limitfor 1T
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
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
Induced field calculation: Solenoid, Biot-Savard
Induced field calculation: Solenoid, Biot-Savard
4 mm Gap
Induced field calculation: Solenoid, Biot-Savard
50 mm Gap, (One Segment left out)
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
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.
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
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
Measurement in Liquid Nitrogen (77K)Test results: Shield about 20% of the outer field
January 2013 Measurement in Liquid Nitrogen
November 2013
Measurements at 1.4 KTest results: (Almost) no shielding observed
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)