MBHSM101 QUENCH PROTECTION STUDIES

1. Susana Izquierdo Bermudez. With many contributions from Juho Rysti, Gerard Willering and all the people involved in the manufacturing and test of the magnet MBHSM101QUENCH PROTECTION STUDIES 25-07-2014

2. General magnet parameters • Identification: MBSMH101 • Coil 101 – Copper coil • Coil 105 – OST RRP 108/127, Ta-Doped • ODS alloy wedges (Oxide Dispersion Strengthening ) • CERN V4 end spacers SLS (Selective Laser Sintering) with springy legs - hinge • Metallic saddles and splice blocks • External trace, glued on coil OD, carrying V-taps and quench heaters Short sample current limits: 4.3 K: 15.15 kA ± 1 % 1.9 K: 16.69 kA ± 1 % More info… http://indico.cern.ch/event/331147/ Peak field is at the ends. The short sample limit is about 1.1-1.2kA higher for the straight section. In all the plots linked to quench heater delay, the 2D short sample limit is considered (because the quench heaters are in the straight section)

3. Overview QH design width Coverage Distance between stations • Main features: • Stainless steel 25 µm thick, partially plated with 5 µm thick layer of copper to reduce their overall resistance (design suitable for 5.5 m length) • Heating stations are 19 mm wide in the mid-plane (LF) and 24 mm wide in pole area (HF) • The distance in between non-plated sections is 90 mm in the LF and 130 mm in the HF where quench propagation is faster in the longitudinal direction. • The heaters are embedded in between two layers of polyimide insulation foils. The thickness of the insulation between the heater and the coil is composed of 0.050 mm of polyimide, about 0.025 mm of Epoxy glue plus the additions S2 glass added to the coil outer radius during impregnation. • The trace is then glued to the coil and compressed radially during collaring to about 40 MPa. 0.2 mm S2 glass 0.025+ mm glue + 0.050 mm kapton QUENCH HEATERS 4x0.5 mm kapton (ground insulation) More details can be found in https://indico.cern.ch/event/311824/

4. Trace manufacturing and characterization • Resistance measurements at RT and 77 K • Stainless steel stations: Measured resistance close to expected values • 3% difference at RT • 8 % difference at 77K • Copper regions: Measured resistance higher • than expected value • 20% difference at RT • 25 % difference at 77K • High current test • No degradation was observed in the bonding • Temperature cycling at 77 K • No degradation Kapton (25 µm) Glue (50 µm) Copper (5 µm) Stainless Steel (25 µm) Glue (<25 µm) Kapton (50 µm) Trace stack for 11T ρss=1.8·10-8Ωm, RRRSS=30 ρss=7.3·10-7Ωm, RRRSS=1.34

5. Trace QA • Before trace installation • Resistance measurements at RT • High voltage test to ground under 20-30 MPa pressure (2kV). • After trace installation, every step of the manufacturing process Expected value: R1=R2=1.65 Ω Measured value ≈ 1.7 Ω • Resistance • QH to ground and QH to coil (1 kV) • Discharge test (pulse). Low thermal load to the heaters (under adiabatic conditions and assuming constant material properties, peak current defined to limit the temperature increase to 50 K) (only in the manufacturing steps after collaring)

6. QH test set up in SM18 Radd Circuit 1 Circuit 2 + RLF C Nb3Sn E - RHF Cu “Standard” LHC Quench Heater Power Supply: V = 450 V, C=7.05 mF Maximum current = 150 A Voltage is fixed to a total of 900 V, additional resistance in series with the circuit is setting the current Three different current levels in the heaters were explored: 80 A, 100 A and 150 A.

7. QH test set up in SM18 13 kA • Quench heater provoked quench performed at different magnet current levels, from 6 kA to 14 kA. • We study: • QH delay • QH efficiency • Transversal heat propagation 10 kA 6.5 kA

8. Quench Heater Delay • What we define as quench heater delay? • 2 times to look at: • Quench heater onset: start of the quench • Quench heater efficient: time where slope of the resistive voltage cross the horizontal axis 21ms 18 ms 28 ms 35 ms Gerard Willering

9. Quench Heater Delay Large difference between “Quench Onset (QO)” and “Quench heater efficient (QE)” at low currents. From now on, if not specified, heater delays plotted correspond to the “Quench Onset” and not “Quench Efficient”

10. Comparison to FNAL 11T dipoles • FNAL MBHSM% insulation between heater and coil: • 0.125 mm of glass on the outer, impregnated with the coil • 0.125 mm of kapton between heater and coil • CERN MBHSM101insulation between heater and coil: • 0.200-0.250 mm of glass on the outer, impregnated with the coil • 0.050 mm of kapton between heater and coil + about 0.025 mm glue MBHSM101 Heater delays are very close to delays measured in FNAL FNAL data from https://indico.cern.ch/event/311824/ Slides from Guram Chlachidze

11. Comparison to HQ Significant longer delays than in HQ. Main difference: in the case of 11T, heaters are glued on top of the coil after impregnation HQ data data from https://indico.cern.ch/event/311824/ Slides from Tiina Slami

12. Comparison to modelled delays • Model by Juho Rysti using the commercial software COMSOL • Basis of the model are the same as Tiina’s model (https://indico.cern.ch/event/311824/) • Quench heater delays modelled for different thickness of S2 glass between coil and heaters. Nominal should be close to 0.3 mm. 0.2 mm S2 glass 0.025+ mm glue + 0.050 mm kapton QUENCH HEATERS 4x0.125 mm kapton (ground insulation) Juho Rysti

13. Comparison to modelled delays QO: Quench Onset QE: Quench Efficient Juho Rysti

14. Transverse heat propagation 6 4 3 5 2 1 Measured propagation consistent with previous FNAL measurements

15. Modelling heat propagation within the coil Two principal directions: 1. Longitudinal Length scale is hundreds of m 2. Transverse Length scale is tenths of mm External heat perturbation Power exchange between adjacent conductors Power exchanged between components in the conductor Joule heating Transverse Longitudinal 2nd order thermal network explicitly coupling with the 1D longitudinal model: The conductor is a continuum solved with accurate (high order) and adaptive (front tracking) methods

16. Modelling heat propagation within the coil Hot spot temperature for different current decays but with the same QI (13 MIITs) • Main simplifications • Constant inductance • Heat transfer from heater to coil is not included in the model. Quench heaters are modelled as a heat source applied directly on the cable • AC loss not included in the model We are focused on the modelling of the thermal transient process, the hot spot temperature for the same MIITs can be very different depending in the time transient

17. Model vs. Experimental Nominal inter-layer thickness: 0.5 mm Block 5  Block 1 Block 6  Block 2 Block 6  Block 3 Points at 14 kA not representative because the quench was starting in the layer jump and not under the heaters

18. Current decay and resistance growth 10 kA 8 kA 12 kA 10 kA 8 kA 12 kA

19. Some comments and remarks • Modelled resistance growth gets closer to experimental values when the thickness of the inter layer is set to 0 mm and only the cable insulation is considered. This can be a combination of different effects: • AC loss is not considered. • Second order thermal network is not “fully catching” the thermal diffusion process in the insulation • Uncertanties in the material properties of the insulation The model does not account for heater stations, it assumes that the entire cable length is covered by the heaters. The relative good agreement with the experimental value is an indication that the heater stations are effective.

20. Longitudinal propagation and Tmax Experimental data from Hugo Bajas Not specific studies on hot spot temperature and longitudinal propagation in MBHSM101, but analysis were performed in SMC using 11T cable. More details: https://indico.cern.ch/event/311824/

21. Conclusions and final remarks • An effort is on going in order to understand the thermodynamic process during quench. Model validation is on going. • Thermal conductivity in the insulation plays a key role and a better knowledge of these properties is important. • We are using G10 material properties for the insulation. Does anyone have measurements/good reference for actual coils, using the same resin, reaction treatment, ceramic binder … ? • Based on the measurements and model, QH delay for the real 11T magnet should be about 20 ms at 80 % of the short sample limit. If we set the MIITs limit to 17 MA2s, this is 25 % of our total budget, it is a lot! • Shorter delay is expected if the heater is impregnated with the coil. • A redundant system with only outer layer heaters seems more than challenging!

22. Additional slides

23. TRAINING

24. Is the long QH delay at low current a killer? • Defining the additional budget as the time we can stay at a certain current to achieve the same MIITs that at 80%Iss one can see that even if the delays are becoming much longer at low current level at lower quench heater current density, the situation is more critical at higher current levels. This is only partially true, because the additional time to detect the quench at lower current level is not included.

25. MB vs. 11T

26. Cable Parameters

27. Protection System LHC Magnets The Protection System for the Superconducting Elements of the Large Hadron Collider at CERN K. Dahlerup-Petersen1, R. Denz1, J.L. Gomez-Costa1, D. Hagedorn1, P. Proudlock1, F. Rodriguez-Mateos1, R. Schmidt1 and F. Sonnemann2

28. STANDARD LHC HEATER POWER SUPPLIES QUENCH HEATER EXPERIMENTS ON THE LHC MAIN SUPERCONDUCTING MAGNETS F. Rodriguez-Mateos, P. Pugnat,S. Sanfilippo, R. Schmidt, A. Siemko, F. Sonnemann Supply based on the thyristor-triggered discharge of aluminium electrolytic capacitors. Each power supply contains a bank with 6 capacitors (4.7 mF/500V) where two sets of 3 parallel capacitors are connected in series  total capacitance 7.05 mF Nominal operating voltage 450 V (90 % of the maximum voltage) OPERATION: Peak current about 85 A, giving a maximum stored energy of 2.86 kJ Actual limitations in terms of current Power supply equipped with two SKT80/18E type thyristors rated for 80 A at 85 ˚C. Maximum current for continuous operation = 135 A Peak current at 25 ˚C for 10 ms=1700 A (it will probably destroy the PCB of the power supply) Can be safely operated up to 300 A (resistive load in LHC from 12Ω in most of the circuits to 3.1 Ω in some systems such as D1 protection )

29. Insulation MP Kapton G10 Thermal conductivity Heat capacity https://espace.cern.ch/roxie/Documentation/Materials.pdf

30. Insulation MP

31. Insulation MP 6 layers mica/glass-6 layers glass NHT 8 cables mica/glass-glass HT 12 layers mica/glass NHT 8 cables mica/glass HT 32 layers mica/glass HT Thermal Conductivity of Mica/glass Insulation for Impregnated Nb3Sn Windings in Accelerator Magnets* Andries den Ouden and Herman H.J. ten Kate Applied Superconductivity Centre, University of Twente, POB 217, 7500 AE Enschede, The Netherlands

32. QH