MQXFS1 Protection heater delays vs. Simulations 9 May 2016 Tiina Salmi, Tampere university of technology Acknowledgement: Guram Chlachidze (FNAL), Emmanuele Ravaioli (LBL)

Magnet and cable parameters Parameter (unit)Value Cable width (bare) (mm)18.15 Cable mid-thickness (bare) (mm)1.524 RRR135 Voids fraction of bare cable (epoxy)0.2 Number of strands40 Strand diameter0.85 Strand Cu/SC1.15 Cable insulation (mm) (G10)0.145 Inter-layer insulation (mm)0.5 Insul. btw OL heater and collar (mm)0.8 Insul. btw IL heater and He (mm)0.125 Field map from Roxie, Current sharing temperature from Summer’s fit 9 May 2016T. Salmi, Tampere University of Technology2 Simulated MQXF coil 103

Heater delay simulation 2-D thermal simulation using CoHDA: Crieterion for quench onset: Cable maximum temperature reaches Tcs -> Current redistribution starts, visible in test set-ups 9 May 2016T. Salmi, Tampere University of Technology3

Assumed quench locations 9 May 2016T. Salmi, Tampere University of Technology4 CERN Heaters IL: 3rd turn from pole, B/Bpeak = 0.89 OL HF: 2nd turn from pole, B/Bpeak = 0.75 OL LF: 1st turn after the wedge, B/Bpeak = 0.57

Heater delay simulated OL 9 May 2016T. Salmi, Tampere University of Technology5 CERN design: 4 cm HS, 16 cm period Heater photos are from Guram’s slides. OL HF: 148 W/cm2, tau = 22 ms OL LF: 145 W/cm2, tau = 23 ms 12 ms 18 ms

Heater delay simulated OL, high current 9 May 2016T. Salmi, Tampere University of Technology6 12 ms 18 ms

Heater delay simulated IL, CERN design HFU RC time constant = 18 ms 9 May 2016T. Salmi, Tampere University of Technology7 CERN design: 2.5 cm HS, 13 cm period

Summary First comparison of measured heater delays with CERN heaters and CoHDA model Outer layer: Good agreement at high current for both LF and HF heaters kA, shortest quench delays 12 ms (HF) and 18 ms (LF), model within +/- 1 ms kA, shortest delays 23 ms (HF) and 40 ms (LF), model predicts up to 12 ms longer delay – Model does not predict the long (> 100 ms) delays at low current (below 5 kA) Inner layer: The model is not accurate kA measured delay was 21 ms. Model predicted 14 ms -At lower currents even larger differences 9 May 2016T. Salmi, Tampere University of Technology8