Long term behavior and high MIITs test in the LARP program GianLuca Sabbi – LBNL WP3 Technical Meeting – May 23, 2019

LARP Model Magnet Reference Chart Technology Development Large aperture quadrupoles HQ and LQ Mirrors Long quadrupoles HQM WP3 Technical Meeting, May 23, 2019

Fabrication and Test Database Test facilities: LBNL (11 tests); BNL (2 tests); FNAL (28 tests); CERN (8 tests, funded by CERN) (#): includes coil exchanges with previously used coils, full reassembly with same coils, or pre-load adjustments (*): includes contributions from FNAL GARD program; (**): includes contributions from LBNL GARD program For this presentation: Long term reliability assessment is based on TQS03 models (where focused studies were performed) and additional data from SQ, LR, HQ and mirror tests Quench temperature limits assessment is based on HQ02a/a2/b and TQS01c studies WP3 Technical Meeting, May 23, 2019

Long term reliability: TQS03 studies A series of tests was performed on TQS03 (coil 30 to 33) to investigate robustness and long term reliability in several key areas: Performance after multiple pre-load and thermal cycles Performance under/after high coil stress (pre-load and operation) Average cold preload: 120 MPa (TQS03a & d); 160 MPa (TQS03b); 200 MPa (TQS03c) Performance after a large number of powering cycles (1000) Overview of TQS03 load cycles: After cool-down (0 kA) 12 kA (91% SSL) 200 MPa 200 MPa Ref: H. Felice et al., IEEE Trans. Appl. Supercond., vol. 21, no. 3, June 2011. WP3 Technical Meeting, May 23, 2019

Validation of TQS03 Mechanical Analysis Comparison with strain gauge measurements: shell, axial rods and coil poles Ref: H. Felice et al., IEEE Trans. Appl. Supercond., vol. 21, no. 3, June 2011. WP3 Technical Meeting, May 23, 2019

TQS03 Quench Performance Four tests performed at CERN in TQS03 models with different pre-load Balance speed of training and consistent plateau after thermal cycle vs. degradation Increasing pre-load in a/b/c gives more stable but slightly lower plateau (93/91/88%) Degradation is permanent: TQS03d with lower pre-load does not recover initial level Good performance in a broad range of azimuthal stress with peak (calculated) up to 260 MPa 91% 93% WP3 Technical Meeting, May 23, 2019

TQS03 cycling test at CERN Performed 1000 cycles from 6 kA to 11 kA with 50 A/s ramp rate Control quenches every ~150 cycles No change was observed in mechanical parameters or quench levels Cycling test was performed after four pre-load/thermal cycles, including studies of performance under high stress, and more than 70 quenches Control quenches are stable within ±25 A H. Bajas, M. Bajko, G. DeRijk, H. Felice, A. Milanese et. al WP3 Technical Meeting, May 23, 2019

LARP Magnets reliably above 88% Notes for “Quenches” column: tests performed with the same coils are grouped in dotted boxes; sums show thermal cycles. WP3 Technical Meeting, May 23, 2019

Degradation and Memory after Thermal Cycles LARP data on performance changes after a thermal cycle is limited Few tests included two thermal cycles: priority on exploring variants and improving performance Each thermal cycle included training at different temperatures, protection studies etc. Available data mostly at 4.5K due to test infrastructure limitations until the later phase of LARP No indication of performance degradation after a thermal cycle from the available data: Data from thermal cycles that included re-assembly or pre-load changes with same coils also shows no indication of performance degradation (except in cases where high stress or high MIITs studies were performed between cycles) In previous slide: SQ02a  SQ02b; LRS01  LRS02; TQS03e  TQC03E; HQ02a  HQ02b No indication of detraining after a thermal cycle, but relevant data is even more limited since only cos2q quads in shell structure are applicable (in addition to the above issues) WP3 Technical Meeting, May 23, 2019

LARP “Technology Development” Tests Long term reliability studies need to be decoupled from performance limitations due to design or fabrication flaws WP3 Technical Meeting, May 23, 2019

Protection limits studies Goal: characterize how the quench temperature affects subsequent magnet performance Approach: Correlate with key physical quantities affecting magnet performance (hot spot temperature, stress etc.) Adjust protection system parameters to achieve a controlled increase of the Quench Integral  I2(t) dt Correlate with subsequent magnet quench levels (detraining or permanent degradation)   * I(t) Delay (var.) Decay (~const.) WP3 Technical Meeting, May 23, 2019

General procedure for High MIITs testing Performance characterization before and after high MIITs is the key challenge Desired conditions: Reproducible quenches at the highest field location (inner layer pole turn) as close as possible to SSL High detraining threshold (and fast training/retraining) A PERFECT MAGNET! WP3 Technical Meeting, May 23, 2019

Quench Limits Studies: HQ02 Models HQ02 = second-generation high field quadrupole incorporating critical improvements in the coil design, fabrication and QA processes Coil fabrication by LBNL and BNL, assembly at LBNL First assembly was tested twice at FNAL with different setups HQ02a: 15 kA current limit, 1.9K-4.5K temperature HQ02a2: No current limit but 2.2K-4.5K temperature Based on the HQ02a2 feedback, the coil pre-load was increased in the HQ02b assembly by ~20 MPa, and tested at CERN HQ02b: No current limit and 1.9K-4.5K temperature The combined tests provided a comprehensive performance characterization including extensive quench protection studies WP3 Technical Meeting, May 23, 2019

HQ02 (a, a2, b) Quench Performance HQ02a: At 4.5 K, above 80% in two quenches, but slow training beyond that HQ02a2: training rate: 30 A/quench; 98% SSL at 4.5K after training at 2.2K HQ02b: training rate: 230 A/quench; 95% SSL at 1.9 K with 200 MPa pre-load HQ02b HQ02a-2 HQ02a WP3 Technical Meeting, May 23, 2019

HQ02 Quench Integral vs. Temperature Quench integral vs. temperature calculation by QMIITs & QLASA (T. Salmi, V. Marinozzi) Material properties from MATPRO (G. Manfreda et al.) using individual coil parameters Estimates based on HQ test data are 20-50 K above adiabatic heat balance (TASC#4003306) WP3 Technical Meeting, May 23, 2019

HQ02a2 Quench Integral Study 98% SSL 10.7 MIITs 96% SSL -120A 12.4 MIITs ~9 MIITs -430A ~9 MIITs HQ02a2 reached 98% SSL @ 4.5K with limiting quenches at high field (pole turn) Slow training above 15 kA and detraining at the 11-12 MIITs level, ~150K Detraining and slow retraining deemed incompatible with degradation studies WP3 Technical Meeting, May 23, 2019

HQ02b Quench Integral study Increased pre-load resulted in less detraining and faster retraining after High MIITs quenches After multiple quenches in the range of 11-24 MIITs (150-380 K) degradation of the quench plateau was less than 2% (from 95% to 93% at 4.3K, without full retraining due to schedule constraints) WP3 Technical Meeting, May 23, 2019

Analysis of 24 MIITs Quench Comparison between 24 MIITs spot heater quench #18 and verification #20 at 4.3K HQ02b-18 Value Current 6.0 Coil 17 Segment A9A10 Field [T] 5.1 Q.I. [MIITs] 24 Tmax [K] 383 HQ02b-20a Value Current (kA) 15.38 Coil 17 Quench segment A9A10 Field A9A10 [T] 12.1 Iq/Iss (4.3K) 0.93 XS Ic meas. Additional retraining and 4.3K verification would have been needed to demonstrate permanent degradation or provide a lower constraint WP3 Technical Meeting, May 23, 2019

Summary of HQ02 High MIITs Studies Detraining vs. MIITs (from HQ02a & HQ02b): Not a fundamental issue or a focus of the high MIITs study, but it negatively affects the high MIITs study due to time required for retraining (in order to recover baseline quench level or assess permanent degradation) Higher preload in HQ02b resulted in better training performance with less detraining due to high MIITs and faster retraining compared to HQ02a Degradation vs. MIITs (from HQ02b): Relative degradation: Less than 2% after multiple high MIITs quenches up to 24 MIITs (380 K) From 95% SSL at the start of the study to 93% at the end (4.3K) Absolute degradation A9A10 segment performs above 93% following 24 MIITs (380 K) quench Hot spot temperature from experimental current/voltage data was ~50K higher WP3 Technical Meeting, May 23, 2019

TQS01 Models TQS01a TQS01b TQS01c Coils 5,6,7,8 7,8,14,15 5,7,8,15 Test 4.5K (LBNL) 4.5K (LBNL) 4.5K & 1.9K (FNAL) Max. current (A) 10602 (4.4K) 11019 (3.2K) 9932 (4.4K) 9600 (4.4K) 10521(1.9K) Iss (%) 87% (4.4K) 82% (4.4K) 80% (4.4K) 80% (1.9K) TQS01a quenches near gaps in bronze pole Limited by degradation due to high axial strain Pole gaps Spikes in coil axial strain (cool-down & excitation) Bronze pole (TQS01/b/c) Ref: S. Caspi et al., IEEE TASC 17, no.2, p. 1222-1225, June 2007 WP3 Technical Meeting, May 23, 2019

TQS01c Training and Quench Studies Training at 4.5K and 1.9K High MIITs study All limiting quenches in coil 15 A6-A8 (pole turn) Temp. dep. 6 - 6.5 7.8 - 8.2 8.7 9.5 Quench limits study conditions and main results: Quench integral was increased from 6 to 9 MIITs by increasing heater and extraction delays At the ~8 MIITs level: initial ±3% variation, then a +3% plateau and then some degradation Stronger and irreversible degradation of 7.4% (25%) after the 8.7 (9.5) MIITs quenches Ref: G. Ambrosio et al., TQS01c Test Report, Fermilab TD-07-007, May 2007 WP3 Technical Meeting, May 23, 2019

TQS01c Degradation vs. Temperature The hot spot temperatures are calculated from the quench integral in the adiabatic approximation using QuenchPro (P. Bauer, TD-00-027) using the relevant material fractions, RRR, and coil field Main results and conclusions: No significant changes below 340K; reversible variations of a few percent in the 370K-400K range; large irreversible degradation above 400K-450K Results are consistent with HQ study and support selecting a 350 K maximum temperature Ref: G. Ambrosio, WAMSDO Workshop Proceedings, CERN-2013-006 WP3 Technical Meeting, May 23, 2019

Summary Long term reliability: LARP optimized models demonstrated very robust behavior with respect to high pre-load, multiple assemblies, quench training and powering cycles However, any design or fabrication flaws -- conductor, coil fabrication, mechanical assembly etc. -- can easily lead to degradation in magnet performance and these effects can exhibit a progressive behavior Quench Limits: Test performed in HQ and TQ did not show performance degradation below 350 K (including some margin to account for uncertainties in performance characterization and hot spot temperature estimate) HQ tests indicate that the magnet can perform above 90% SSL after experiencing hot spot temperatures approaching 400 K Quench limit studies are very demanding on facilities and resources, however, a more complete characterization program would be a worthwhile investment to reduce the present uncertainties WP3 Technical Meeting, May 23, 2019