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CERN Fast Cycled Magnet demonstrator: test station, instrumentation and measurement campaign

CERN Fast Cycled Magnet demonstrator: test station, instrumentation and measurement campaign. G. Willering 1 , M. Bajko 1 , F. Borgnolutti 2 , L. Bottura 1 , V. Datskov 1 , G. Deferne 1 , J. Feuvrier 1 , L. Fiscarelli 1 , C. Giloux 1 , M. Guinchard 1 , V. Roger 1

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CERN Fast Cycled Magnet demonstrator: test station, instrumentation and measurement campaign

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  1. CERN Fast Cycled Magnet demonstrator:test station, instrumentation and measurement campaign G. Willering1, M. Bajko1, F. Borgnolutti2, L. Bottura1, V. Datskov1, G. Deferne1, J. Feuvrier1, L. Fiscarelli1, C. Giloux1, M. Guinchard1, V. Roger1 1CERN, 2LBL 18-07-2013 MT-23, Boston, MA 4OrCB-05

  2. Contents • Introduction • FCM magnet project • Test station • Instrumentation • Test conditions • Measurements • Magnet powering • Current Cycling • Training quenches • Quenches at Short Sample limit • Temperature and losses • Mechanical measurements

  3. FCM magnet project The PS at CERN, operating since 1959 • Injector upgrade scenario includes a new PS2 (Proton-Synchrotron) • Ramp time 1.1 s, flattop 0.1 s. • Required dipole field 1.8 T • Energy consumption can be reduce by a factor of 2 compared to a normal conducting option • The FCM project aims to demonstrate the feasibility of reliable, low-loss superconducting technology.

  4. Magnet concept Cryostat 2 coils of 10 windings Central gap 70 mm gap Warm iron yoke Yoke length 0.821 m Magnetic length 0.710 m Cross-section

  5. Conductor Demountable joints Conductor specifications Type Nuclotron cable ID 4 mm OD 7.7 strands 32 Nb-Ti Matrix mixed Cu/Cu-Mn Mechanics Ni-Cr wrap Magnetic field Central magnetic field 1.8 T Maximum conductor field 0.7 T Cable soldered in Cu shoe Two Cu parts clamped with In-foil Cryogenics Forced flow cooling though central tube by supercritical helium at 3 B, 3 g/s at 4.5 K.

  6. New test station at CERN FCM – Summer 2012 • Supercritical helium at 4.5 K, 3 Bar, mixed with warm He-gas • Temperature reach between 4.5 and 80 K forced flow • Designed for FCM and SC Link The superconducting link aims at connecting the LHC magnet circuits to the power converters over a distance of 600 meter, cooled by He gas

  7. Magnet cooling schematics 4.5 K, 2-3 B Mixing Chamber 300K • Cooling control: • Mixing supercritical Lhe of 4.5 K with Ghe of 300 K • For each coil a heater can increase the temperature

  8. Temperature probes 12 CCS (Carbon Ceramic) temperature sensors. Good contact with the cable & temperature stabilized In hind-sight the main error in enthalpy determination came from high uncertainty in pressure measurements (±0.1 Bar) CCS temperature sensor on the cable (V. Datskov, session 1PoAP-01)

  9. Cryogenics • Long (~ 18 m) small diameter (4 mm) tube • Large pressure drop over the magnet resulting in a big change in density at 3 bar at a point where the heat capacity is at its maximum. Calorimetric measurement has a very low resolution at this condition. • Temperature control for low flow-rate of GHe was stable to 0.2 K

  10. Calorimetric measurements • Stepwise increase of heating power resulted in: • Stepwise increase in temperature • Decrease in helium flow due to density change. • Major issues: • Stable supply of helium temperature, flow and pressure. • Operation in the phase transition region of Helium: Large expansion in a long thin tube.

  11. Powering summary 1 quench to Inominal= 6 kA First powering to 6 kA, August 10th, 2012 Possible detraining (6.6 K) from Imax= 7.5 kA 3 quenches to Imax= 7.5 kA

  12. Cycling • Onequadrant power supply: • Ramp down speed limitedbyL/R of the circuit at 3 kA/s • Ramp up at nominal 6 kA/s • Cycling tests were performed in trains of 10 minutes at about 4.8 K, 3 g/s, 3 Bar supercritical helium cooled • Test cycle duration 3.5 s versus a nominal cycle duration of 2.4 s First test cycle trains, August 16th, 2012 Longest series: 5h - 4650 cycles (3.9 s/cycle aver.) In total 20000 cycles performed

  13. Measurement of Tcs Set stable temperature at the inlet (e.g. 7 K) Current ramp (e.g. 1 kA/s) Quench (e.g. 6 kA) Hot helium expulsion ≈ 0.2 K Dump (t ≈ 0.2 s, Vmax ≈ 60 V)

  14. Quench propagation velocity • Rough estimates from measurements of vnzp • Length of normal zone at detection 0.1 to 0.2 m • Quench position unknown during these training quenches Magnetic field profile along the conductor Quench propagation velocity well in between adiabatic calculations and cable test in FReSCa.

  15. Tcs results Data from FRESCA cable tests Quenches outside the magnet coils • Error in temperature 0.2 K • The behavior of the two coils is very similar ! Overall excellent agreement to short sample !

  16. Ramp-rate dependence Data from Tcs measurement at different ramp-rate was reduced to a reference temperature of 7 K (Iq~ 6200 A) applying an average temperature correction of 2300 A/K No ramp-rate dependence can be observed in the resulting data-set ! ±0.2 K 6200 Most of the scatter can be explained by the uncertainty on temperature (±0.2 K in Tcsequals± 500 A in Iquench) ±0.2 K

  17. Pushing the limit Working point Stable cycling at 0.5 K from the expected cable critical current! (2600 cycles) T inlet T outlet coil 1 T outlet coil 2

  18. AC loss estimate Low density (10 kg/m3), high speed (13 m/s) flow The large JT expansion causes temperature drop System oscillations (cryoplant) do not allow a precise evaluation of the loss by calorimetry. Error bound ± 1 W/coil The measured AC loss for the magnet is smaller than 2 ± 2 W Expected AC loss (based on cable measurements and field map) is 0.15 W/coil, compatible with above estimate

  19. Pick-up coils efficiency Challenge Measure resistive voltage of a coil Solution Co-wind the voltage tap wire with the coil to eliminate Vinductive Result Max 25 mV at 6 kA/s Pickup coil voltage only 0.2 % of coil voltage Saturation effect above 3 kA visible Non-uniform field on magnet coil and pick-up coil results in a different response

  20. Magnetic performance Measured field corresponds with calculations. Multipole b3 is specifically high -> Magnet is not yet optimized for field quality. Magnetic field profile along the conductor Measured field (700 mm probe) Reconstructed field MSC/MM Measurement Note 2012-02, by Lucio Fiscarelli

  21. Mechanics 8 Tie rods, equipped with strain gauges 8 strain gauges measuring the bending

  22. Mechanical measurements Magnet supported by 8 tie-rods. Strain between 20 and 150 μm/m. Stable over the 20k cycles.

  23. Mechanical measurements Calculated strain 75 – 105 μm/m • Calculated deflection up to 0.8 mm at 6 kA • Measured strain on bending parts 70 μm/m • Strain about linear to I2 • Mechanics well-understood and far from its limits. Courtesy: Sergio dos Santos, Michael Guinchard, Giuseppe Foffano EDMS 1173289

  24. Conclusions and perspectives (1) • To the extent that we could probe the FCM magnet performance, the concept is suitable for a fast cycled injector magnet ! • No issue of performance (we had 1 quench to nominal field, and we think we understand why) • Very stable operation beyond the performance envelope (in 3 quenches, up to 50 % Lorentz force in excess of the design value, estimated > 0.5 mm coil movement) • 20 kCycles close to nominal operation conditions, no spurious quenches, no observed degradation • Losses in the coil below measurable level of 4 W/m of magnet

  25. Conclusions and perspectives (2) • The magnet is not yet optimized for magnetic field quality and the multipole b3 error is still too high. • The mechanics of the magnet are as designed. ReBCO CORC Nb-Ti Nuclotron HTS may be feasible? Invited talk 2OrBB-01by D.C. van der Laan, High-temperature superconducting Conductor on Round Core magnet cables operated at high current ramp rates in background fields of up to 19 T

  26. Thank you! • Project follow-up • F. Borgnolutti (LBNL), L. Bottura • Concept and design • B. Auchmann, G. Foffano, M. Karppinen, G. Kirby, R. Maccaferri, C. Maglioni, V. Maire, V. Parma, T. Renaglia, G. de Rijk, L. Rossi, T. Salmi (LBNL), W. Scandale, D. Tommasini • Procurement and manufacturing • A. Bonasia, M. Bruyas, S. Clement, W. Gaertner (BNG), R. Gauthier, J.M Gomes de Faria, C. Lopez, L. Oberli, G. Sikler (BNG), the CERN Central Workshop • Instrumentation and tests • M. Bajko, V. Datskov, G. Deferne, L. Fiscarelli, M. Gateau, M. Guinchard, S. le Naour, G. Peiro, V. Roger, D. Richter, G. Willering

  27. Backup slides

  28. Strand and cable mixed matrix Cu/CuMn/NbTi wire (ALSTOM) CACC: Cable-around-conduit conductor (BNG-Zeitz) Supercritical helium force-flow cooling Cu-Ni pipe Nb-Ti strands Ni-Cr wrap Glass-tape

  29. Magnet parameters

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