MQXF protection – comparison between 1 or 2 power supplies Vittorio Marinozzi 06/08/2015 1

2 Summary: 1.Assumptions made in the simulations 2.Hot spot temperature considering 1 or 2 PS (QLASA)  Nominal cases  Failure scenarios 3.Voltages considering 1 or 2 PS (ROXIE)  Nominal cases  Failure scenarios (work in progress)

3 1.1 Assumptions in simulations - PH  Quench assumed to be induced on all the turn covered by heaters  Average delay times used for high-field and low-field zone  Delay times computed by CoHDA (Tiina Salmi)  Heating stations are simulated, but not pre-heat (conservative)  Transversal and longitudinal propagation computed by QLASA

4 1.1 Assumptions in simulations - PH

5 Protection parameters Current [A]16470 Inductance [mH/m]8.21 Lenght [m]31.1/16.8 Dump resistor [mΩ]50 (820V) Dump resistor delay [ms]5 Validation time [ms]10 Cu/Non-Cu1.2 Bare cable width (mm)18.15 Bare cable average thickness (mm)1.525 Cable insulation thickness (mm)0.145 RRR Assumptions in simulations – nominal protection parameters Q1Q2aQ2bQ3 Q1Q m / 1 PS 16.8 m / 2 PS No quench back Dynamic effects on the inductance (iron & IFCC) Dynamic effects on the inductance (iron & IFCC)

6 2.1 Hot spot temperature - nominal 31.1 m (1 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch) m (2 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch) Just < 5 K gain using 2 PS instead 1 PS !  Magnets can be considered safe

7 2.1 Hot spot temperature - nominal τ 1PS ~ 4 s τ 2PS ~ 2 s Power dissipated on Rd: 1.26 MJ with 1 PS (4 % of the stored energy) 1.25 MJ with 2 PS (7 % of the stored energy) Power dissipated on Rd: 1.26 MJ with 1 PS (4 % of the stored energy) 1.25 MJ with 2 PS (7 % of the stored energy)

8 2.2 Hot spot temperature – no IL-PH 31.1 m (1 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch) m (2 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch)  With only outer-layer protection heaters, protection is not ensured

9 2.3 Hot spot temperature – OL-PH failure in the high-field block 31.1 m (1 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch) m (2 PS)Hot spot temperature [K]MIITs [MA 2 s] No dynamic effects Dynamic effects (14 mm pitch) Dynamic effects (19 mm pitch)  Failure is assumed in all the strips of the outer-layer high-field zone Very pessimistic case  A good redundancy is ensured

Hot spot temperature – conclusions  Magnets can be considered safe, if the whole protection system work  Protection heaters on the inner layer are indispensable in order to ensure safety. Alternatively, protection using CLIQ has to be investigated (Emmanuele)  There is not a relevant difference between using one or two power supplies (Q1/Q2a/Q2b/Q3 series or Q1/Q3 and Q2a/Q2b series), on the hot spot temperature point of view  Redundancy is ensured

11 MQXF voltage analysis (work in progress)

MQXF voltages Rd=50 m Ω ~820 V between current leads To ground [V]Turn-turn [V]Layer-Layer [V]Midp-Midp [V] Q1/Q3 (1 Power Supply) Nominal Coil 1 PH failure Q2a/Q2b (1 Power Supply) Nominal Coil 1 PH failure Q1/Q3 (2 Power Supplies) Nominal Coil 1 PH failure Q2a/Q2b (2 Power Supplies) Nominal Coil 1 PH failure “To ground” column to be checked! Ground positioned on the “in” current lead

MQXF voltages-conclusions  To ground voltage is almost independent on the number of power supplies It is about ~1 kV (to be checked) in the nominal case for both Q1/Q3 and Q2a/Q2b It doubles if all the coil1 inner-layer protection heaters fail  Turn-turn voltage too is independent on the number of PS ~27 V for Q1/Q3, ~45 V for Q2a/Q2b in the nominal case ~50 % bigger if all the coil1 inner-layer protection heaters fail  Layer-layer voltage too is independent on the number of PS ~270 V for Q1/Q3, ~450 V for Q2a/Q2b in the nominal case ~4 times bigger if all the coil1 inner-layer protection heaters fail  Midplane-midplane voltage doubles choosing 2 PS instead of 1 PS ~85/150 V for Q1/Q3, ~150/310 V for Q2a/Q2b in the nominal case ~11 times bigger if all the coil1 inner-layer protection heaters fail  Other scenarios are going to be analyzed (only outer layer PH, failure of few PH strips…)