MQXFS1 Test Results G. Chlachidze, J. DiMarco, S. Izquierdo-Bermudez, E. Ravaioli, S. Stoynev, T. Strauss et al. Joint LARP CM26/Hi-Lumi Meeting SLAC May 18-20, 2016

Introduction The very first test of a 150-mm diameter Nb 3 Sn quadrupole MQXFS1 Short model with 1.5-m long coils Coils fabricated both at CERN (#103 and #104) and LARP (#3 and #5) Previously LARP coil #2 successfully tested in a “mirror” configuration After the first cool down in November 2015 the magnet leads were damaged during the low current tests Investigating committee performed a thorough cause analysis of the incident Recommendations were made to increase safety of the test process The incident and findings of the investigating committee were discussed at meetings with the LARP and CERN colleagues The magnet and top plate power leads were replaced in a very short time Shorted-bus test was done to check new power leads of the top plate at currents up to 25 kA Thanks to coordinated and efficient efforts of the team the problem was well identified and fixed 2

Cable properties & SSL Estimates Coils made of Nb 3 Sn strand RRP 108/127 (#3 and #5) RRP 132/169 (#103 and #104) SSL at 1.9 K: 21.5 kA (coil #103) 3 Cable width, mm Cable mid. thickness, mm1.529 Keystone angle, degree0.518 Twistpitch, mm109 Number of strands40 Core 316 SS Short-sample CurrentFieldGradienCurrentFieldGradienNom. CurrentNom. GradientNom. Field% Iss 4.3 K 1.9 K kATT/mkATT/mkAT/mT% Coil Coil Coil Coil Magnet

Magnet Instrumentation LARP magnet instrumentation: Voltage taps on the IL and OL CERN and LARP SG systems (train gauges on the coils, rods and shell) Quench antenna Magnet is protected with the IL/OL PH 4 IL Heaters OL Heaters CERN coils LARP coils

Cool down and checkouts Controlled cool down: Temperature gradient less than 100 K between the magnet top and bottom 4 Days of cool down (a week of warm up) 120 m Ω dump resistor for initial checkouts, and 30 m Ω for the quench training 5

Quench Training Training at 1.9 K in TC1 with ramp rate of 20 A/s Highest quench current 18.1 kA or 84.2% of SSL at 1.9 K T/m, 12.5 T

Quench Training (cont’d) Coil azimuthal gauges exhibited unloading (coil separation from the pole) starting from the very first training quench Low pre-load during the magnet assembly Test plans changed: Avoid further training and proceed with the re-prioritized test plan, including quench at 4.5 K and TC2 for quench memory study Check magnet performance for increased pre-load (MQXFS1b) 7

Quench memory Same quench current reached in the first and one only ramp at 4.5 K ~ 93% of SSL In TC2 the magnet continued training from exactly the same place 8

Ramp rate dependence Only few quenches at different ramp rates to avoid further magnet training Quench at 400 A/s developed in the mid-plane, all others - in the pole area 9

Quench Locations Most quenches developed in coil #103 Coil #103 is a limiting coil from the SSL estimates 14 different segments participated in 19 quenches Still in training, low pre-load 10

Quench Locations (cont’d) Most of training quenches developed in the IL pole turn segments 2 quenches could be motion related 2 quenches in the ramp between the coil layers

Quench Locations (cont’d) Most of quenches originated from the pole turns, few – from the IL Pole block Quench antenna signals found very noisy. QA will be repaired and tested in MQXFS1b 12 Pole turns IL Pole block

RRR measurements 13 Coil #3 Coil #103Coil #104 Average measured RRR (witness sample RRR range) LARP coils #3: 250 ( ), and #5: 255 ( ) CERN coils #103: 135 ( ), and #104: 105 ( ) Coil #5

“Holding current” Tests Goal of the test is to demonstrate stable operation at the nominal (ultimate) current for an extended time period 8-hour “Holding current” tests were done at 1.9 K: No quench at I nom =16480 A No quench at I ultimate =17760 A 14

Quench Protection Study Quench protection plans also re-prioritized: Minimum heater power density to start a quench PH delay - Delay between heater firing and quench development Fast Extraction study Only CERN style PH were tested Reference heater test parameters were selected according to the expected values in the full-length MQXF magnet LARP heaters previously tested with the coil #2 in a “mirror” configuration MQXFSM1 LARP heater tests and other QP studies will be completed in MQXFS1b magnet test 15

Minimum power density Expected power density in long models (CERN style PH): 2-strips of OL in series per HFU – W/cm2 1 only IL strip per HFU W/cm2, 2-strips of IL in series – 59 W/cm2 16

Minimum energy density 17 Expected deposited energy density in long models (CERN style PH): 2-strips of OL in series per HFU – 2.7 J/cm2 1 only IL strip per HFU – 3.3 J/cm2, 2-strips of IL in series – 1.7 J/cm2 S. Izquierdo-Bermudez & E. Ravaioli

Heater delay study 18 S. Izquierdo-Bermudez, E. Ravaioli et al.

PH delay study (cont’d) 19 First comparison of the CERN and LARP heaters Coil #103 in MQXFS1 Coil #2 in MQXFSM1 Time constant of the Heater circuit (RC): 40ms/100ms in MQXFSM1 ~ 20ms in MQXFS1 2 IL strips fired in the “mirror” magnet, while only one - in MQXFS1 Comprehensive study of the LARP and CERN style heaters in MQXFS1b test

Splice Resistance Nb 3 Sn-NbTi splices measured in all coils: average resistance of 0.3 n Ω in LARP coils and 0.12 n Ω in CERN coils 20

Brief Summary The very first 150-mm diameter Nb3Sn magnet test was a success In some areas improvements are necessary to meet the design requirements The magnet exceeded the ultimate current of 17.8 kA which is 108% of the operating current, and demonstrated excellent quench memory in the 2 nd thermal cycle The magnet demonstrated stable operation at the nominal (16.5 kA) and ultimate (17.8 kA) currents - “holding current” tests for more than 8 hours Most of training quenches developed in the high field area – the IL pole turn segments The highest quench current was achieved in the very first ramp at 4.5 K, corresponding to about 93% of SSL 21

MQXFS1b Plans Due to possible coil separation, MQXFS1 test was interrupted Analysis of the SG data, and pre-load plans for MQXFS1b will be presented today Further study with increased pre-load will be done in MQXFS1b Effect of increased pre-load on quench training, especially above 18.2 kA Comprehensive quench protection study, including fast extraction tests Both the CERN and LARP SG systems will be utilized again SG system in long magnet will be selected based on test results in short models More exciting results are expected in July - MQXFS1b test There are even plans for MQXFS1c 22

Backup Slides 23

MQXFS1 vs. the “mirror magnet” 24