Simulations of a shortcircuit in HLLHC inner triplet

Simulations of a short-circuit in HL-LHC inner triplet quadrupole E. Ravaioli (CERN) on behalf of the STEAM team 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 1

HL-LHC inner triplet quadrupole magnet MQXF • LARP-CERN collaboration • Nb 3 Sn conductor • 150 mm aperture • Peak field 12 T • Nominal current 16. 5 k. A • High current density • High energy density • Quench protection with heaters and CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 2

MQXFAP 1 internal short circuit simulations Model description • • • STEAM Circuit Short-circuit model STEAM-Co. Sim simulations STEAM-SING simulations 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 3

Model description LEDET SPICE Electro-magnetic and thermal model of the magnet (coupling losses, heat propagation, differential inductance, etc) Electrical network of the circuit including the internal short (power supply, energy -extraction, CLIQ unit) 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 4

Model description – Internal short via heater strip Power supply Energy-extraction system CLIQ unit Magnet O 2 I 5 I 3 O 4 I 4 O 5 O 3 O 4 28 May 2018 O 2 I 3 I 2 I 4 I 5 • Short circuit across 2 turns (internal short) • Turns located as shown in the plot O 5 Short resistance unknown; range Rs=0. 01 -100 Ω Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 5

MQXFAP 1 internal short circuit simulations Model description STEAM-Co. Sim Time-domain simulation results • Simulation of the last training quench • Effect of quench protection system • Effect of short-circuit resistance • Simulation of various short-circuit types STEAM-SING simulations 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 6

Internal short through heater strip, Rshort=1 Ω EE+OLH+ILH 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 7

Internal short through heater strip, Rshort=1 Ω Voltage across the turns and to ground is similar when CLIQ is used → I_short is similar as well EE+OLH+CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 8

Effect of protection system (for Rshort=1 Ω) Magnet current Energy deposited in the short-circuit The severity of the shortcircuit consequences is independent of the quench protection system Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Power deposited in the short-circuit 9

Internal short – Effect of Rshort EE+OLH+CLIQ Magnet current Energy deposited in the short-circuit The severity of the shortcircuit consequences is strongly dependent on the short resistance (unknown) Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Power deposited in the short-circuit 10

Internal short – Simulation result summary The severity of the shortcircuit consequences is strongly dependent on the short resistance (unknown) EE+OLH+CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 11

MQXFAP 1 internal short circuit simulations Model description STEAM-Co. Sim simulations STEAM-SING frequency model of warm MQXFAP 1 • • • 28 May 2018 Model assumptions Validation against MQXFAP 1 pole frequency-measurements in LBL in 2017 Effects of a short Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 12

Model validation – Simple model • Measurements on all four poles performed in March 2017 at LBNL • The four poles were on the table, not inserted in the structure 28 May 2018 Very little difference between the four poles The frequency-domain impedance measured at warm does NOT match the impedance of an ideal inductor Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 13

Model validation – Improved model Model changes • One RL loop coupled with each pole turn (eddy currents in the conductor? ) • Another RL loop coupled with each pole turn (eddy currents in copper wedges? ) • Resistor in parallel to the pole (4 kΩ) 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli The model was adjusted with empirical parameters to match measurements 14

Model results – Example of a short-circuit • Short to ground inserted between turn #28 (out of 50 turns) and ground • Parametric sweep varying its resistance value 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli A short-circuit to ground with resistance lower than a few hundred Ω should be clearly visible 15

Conclusions on the simulations • The STEAM (LEDET+SPICE) model was used to simulate the transient following a quench in the MQXFAP 1 magnet, in presence of various types of short circuits: across a few turns (through an heater strip), between coil and an heater strip, between coil and ground, or combinations of these • The model can be easily adapted to simulate similar events • Previous results of internal short-circuit simulations in LEDET (by Vittorio) are valid, but only for relatively high values of short-circuit resistance • Peak current through the short-circuit, peak deposited power, and total deposited energy depend only slightly on the quench protection system • On the other hand, they strongly depend on the value of the short-circuit resistance (unknown) • [not surprising] A quench at high current in presence of a short circuit across a few turns (internal short) or to ground will very likely cause permanent damage with any protection system • The simulation of these events is particularly challenging due to the (likely) simultaneous presence of multiple types of shorts and the changes in time of their resistances 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 16

Annex 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 17

Effect of a short circuit Courtesy of P. Joshi, J. Muratore (BNL) I_GND 1 and I_GND 2 have the same sign + + 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 18

LEDET model Runs in 3 minutes! The interaction between the superconducting magnet and the local coupling currents is modeled with an array of RL dissipative loops mutually coupled with the magnet self-inductance All simulations presented today are performed with the LEDET 2 D model (Lumped-Element Dynamic Electro-Thermal) Inter-filament coupling currents 28 May 2018 Inter-strand coupling currents Example: HL-LHC 12 T Nb 3 Sn quadrupole magnet (MQXF) • 2 x 16000 IFCL loops • 400 ISCL loops [1] E. Ravaioli, “CLIQ”, Ph. D thesis, 2015 [2] E. Ravaioli et al. , Cryogenics 2016 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 19

LEDET (Lumped-Element Dynamic Electro-Thermal) Validated on cos-θ dipole (MB, 11 T) and quadrupole (MQY, MQXC, HQ, MQXF) magnets 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 20

Short-circuit models 1 1. 2. 3. 4. 2 Internal short circuit across a few magnet turns (through heater strip) One short circuit between coil and heater strip (floating) One short circuit between coil and ground (through heater strip) [1+3] Internal short circuit across a few magnet turns (through heater strip) and one short circuit between coil and ground (through heater strip) 3 28 May 2018 4 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 21

Model description – Internal short via heater strip O 2 I 5 I 3 O 4 I 4 O 5 O 3 O 4 28 May 2018 O 2 I 3 I 2 I 4 I 5 • Short circuit across 2 turns (internal short) • Turns located as shown in the plot O 5 Short resistance unknown; range Rs=0. 01 -100 Ω Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 22

Internal short, Rshort=10 Ω EE+OLH+CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 23

Internal short, Rshort=0. 1 Ω EE+OLH+CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 24

Internal short, Rshort=0. 01 Ω EE+OLH+CLIQ 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 25

Internal short, Rshort=0. 1 Ω EE+OLH+ILH 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 26

Internal short – Effect of Rshort EE+OLH+ILH Magnet current Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Energy deposited in the short-circuit Power deposited in the short-circuit 27

Model description – Single short to heater strip O 2 I 5 I 3 O 4 I 4 O 5 O 3 O 4 28 May 2018 O 2 I 3 I 2 I 4 I 5 O 5 • Single short circuit between coil and heater strip • Short resistance unknown; range Rs=0. 01 -100 Ω • Capacitance Cs=10. 5 n. F, same as capacitance between one heater strip and ground Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 28

Simulation of a single short to H strip, Rshort=50 Ω, Cshort=10. 5 n. F Magnet current Energy deposited in the short-circuit Short between coil and heater strip has little consequence if no additional short is present Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Power deposited in the short-circuit 29

Model description – Single short to ground O 2 I 5 I 3 O 4 I 4 O 5 O 3 O 4 28 May 2018 O 2 I 3 I 2 I 4 I 5 O 5 • Single short circuit between coil and ground • Short resistance unknown; range Rs=0. 01 -100 Ω Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 30

Simulation of a single short to ground, Rshort=1 Ω Magnet current Energy deposited in the short-circuit A short between coil and ground can easily result in permanent damage [unsurprising] Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Power deposited in the short-circuit 31

Simulation of a single short to ground, Rshort=50 Ω Magnet current Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Energy deposited in the short-circuit Power deposited in the short-circuit 32

Model description – Short to ground + short across 2 turns O 2 I 5 I 3 O 4 I 4 O 5 O 3 O 4 28 May 2018 O 2 I 3 I 2 I 4 I 5 O 5 Best guess based on Gerard’s analysis: • Short circuit between coil and ground • Short circuit across a few turns (through the heater strip) • Short resistances unknown; range Rs=0. 01 -100 Ω Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 33

50 Ω short to ground + 1 Ω short across 2 turns Magnet current Energy deposited in the short-circuit This but one example. Many combinations of short resistance to ground across turns possible Short-circuit current 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli Power deposited in the short-circuit 34

Frequency-domain model of warm MQXFAP 1 • Each turn as a separate cell composed of • A resistor with the turn warm resistance • An inductance with the turn selfinductance • Mutual inductance to all other turns • A capacitance to ground (at the moment, same capacitance for each turn; used as a fitting parameter) 28 May 2018 Pic here soon Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 35

Next steps • The STEAM (LEDET+SPICE) model was transferred to Vittorio for further analyses (varying type and position of the short circuit, magnet conditions, short resistance, etc) • The STEAM team will continue working on the analysis of the MQXFAP 1 short circuit(s) • Proposal of tests on the MQXFAP 1 magnet at warm • Proposal of tests on the MQXFS 3 magnet • Slow scan data analysis • The STEAM team will continue working on the simulation of short-circuit events • COMSOL model • SPICE model of the magnet in the frequency domain 28 May 2018 Simulations of a short-circuit in HL-LHC inner triplet quadrupole – E. Ravaioli 36