Cable tests at FRESCA

1
Cable tests at FRESCA

• Designed to fit FRESCA collars
• Two cables protected by two dummy cables

FRESCA Features
G. Ambrosio, et al., Critical Current and
Instability Threshold Measurement of Nb3Sn Cables
for High Field Accelerator Magnets IEEE Trans.
on Applied Superconductivity, Vol. 15, No. 2, pp.
1545-1549, June 2005.
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Different cable layouts

• PIT-Sample (PIT strands)
• HT 99h _at_ 675 ºC
• RRR 110
• Short sample Ic _at_ 12 T 597 A (Extracted)
• Signs of tin contamination of Cu matrix close to
  cable edges, after HT
• MJR-Sample (MJR confined in field region,
  PIT elsewhere)
• HT 100h _at_ 210C, 48h _at_ 340C,
• 180h _at_ 650C
• RRR 9
• Short sample Ic _at_ 12 T 705 A (Virgin)

FIELD
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Very good correlation between cables and magnets

• Iq (4.3K ,10.5T)
• Iss (5.6K, 10.5T)
• ?heat from the splices
• return splice had
• R 0.85 nW

• Iq of B-ramps lt Iq of I-ramps
• Minimum of unstable region ( 12 kA) in the range
  1.5 3 T
• Comparison with HFDB02 (same cable, same HT)

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Cable characteristics

• All samples were made of cables with the same
  characteristics of the cables used for FNAL
  cos-theta short model magnets
• 28 strands
• Strand diameter 1 mm
• Cable width 14.2 mm
• Cable average thickness 1.82 mm
• Keystone angle 0.9 deg
• Cable transposition pitch 110 mm
• Strand type (vendor) MJR (OST) PIT (SMI)
• Insulation ceramic or S2-glass tape ceramic
  binder

Deff 110 mm
Deff 54 mm
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Tests also at 1.9 K

• Same Instability threshold !

6
Excellent acquisition
B 1 T , RR 150 A/s T 4.3 K, I lt 17000 A

• 1st segment
• 500 mm
• 2.4 ms
• ? V 208 m/s

Spike propagation and coupling
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Veryyy fast spike

• T 4.3 K
• I 12.5 kA
• B 1.8 T
• B-ramp-up (1T/min)
• V 875 m/s !
• Strong coupling also in this case !

22 mV
0.6 ms
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Sample preparation

• Reaction
• Splices and Voltage Taps (on cable edges)
• Impregnation in situ
• Pre-stress by adding a Kapton layer after
  impregnation