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Zinour Charifoulline, TE-MPE-PE

Update on Splice Resistance Measurements at 1.9K (LHC Main Magnet Circuits). # Splice protection & monitoring – short intro # R ecent general statistics (IPAC’12) # 2012 versus 2011: one suspicious case detected # Comparisons with ELQA measurements (preliminary).

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Zinour Charifoulline, TE-MPE-PE

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  1. Update on Splice Resistance Measurements at 1.9K • (LHC Main Magnet Circuits) # Splice protection & monitoring – short intro # Recent general statistics (IPAC’12) # 2012 versus 2011: one suspicious case detected # Comparisons with ELQA measurements (preliminary) Zinour Charifoulline, TE-MPE-PE TE-MPE-TM

  2. Data Source and Current Statistics I nQPS BS: Cold Splice Protection and Measurement Magnet Logging DB U_RES(t), U_MAG(t) I_MEAS(t) nQPS BS (A&B) 2 3 1 U_MAG: LSB=1.9µV, Range=±15.9V PtP≈500µV(noise) U_RES: LSB=1.5nV, Range=±12.8mV PtP≈50µV-100µV (noise) 5Hz, 50points moving average (10s) 2048 channels (x2) Bus Bar 4 Magnet TE-MPE-TM

  3. Data Source and Current Statistics II Measurements: 3.5-4TeV Ramps with 1 hour on injection and 1 hour on the top Current Statistics: about 610 (2010-2012) resistance tables for the bus bars (interconnects) about 200 tables for the internal splices (magnets) • Splice Protection: • 2048 LHC Main Magnet interconnections; • about 10300 superconducting joints or splices; • 2x2048 nQPS DQQBS boards (A&B); • U_RES > 500µV (83nΩ@6kA) => EE triggered; • measured voltages are stored to Logging DB (5Hz); • Splice Resistance Monitoring: • long enough 3.5-4TeV ramps are detected and • analyzed (in automatic way); • resistances are calculated taking into account only • plateaus points and saved to csv-files; • warning message (e-mail and sms) are generated • if any bus resistance is more than 20nΩ; • - second level of warning if resistance is out • of 10 sigma range of last saved statistics • (noisy boards detection so far); Injection ~2h20 hours 3.5-4TeV nQPS DQQBS: URES = UBUS – CCOMP * UMAG U_RES: LSB= 1.5nV, Range= ±12.8mV, PtP≈ 50µV U_MAG: LSB= 1.9µV, Range= ±15.9V, PtP≈ 300µV TE-MPE-TM

  4. LHC Main Magnet Bus Bar Segments Resistances RB: 2010 RB: 2010 + 2011 RB: 2010 + 2011 + 2012 918±97pΩ 3 splices 618±61pΩ 2 splices RQ: 2010 RQ: 2010 + 2011 RQ: 2010 + 2011 + 2012 2.81±0.31nΩ 8 splices TE-MPE-TM

  5. Bus Bar Segments B34L4_1 versus Time 2011 2010 2012 <R> = ΣRi·(1/σi)2/ Σ(1/σi)2 Var= Σ(<R> -Ri)2·(1/σi)2/ Σ(1/σi)2 TE-MPE-TM

  6. Maximum and Average Splice Resistances RB Bus Bar Segments RQ Bus Bar Segments Since each bus-bar segment containsnsplices it is not possible to measure the resistance of an individual splice. However, one can estimate the maximum splice resistance in a segment assuming that the excess is localized in one splice only, so Rspl,max = Rsegment – (n-1) * Rspl,avg, where Rspl,avg is the average splice resistance. Rspl,avg RB Bus Bars 308±30pΩ Rspl,avg RQ Bus Bars* 301±33pΩ * In case of quads the number of splices per segment is corrected due to the specific design of the protection voltage taps . The correction estimated by comparing the resistances of 6 and 8 splice segments is about 2x0.20 nΩ. TE-MPE-TM

  7. Main Magnet Bus Bar Segments Resistances, 2010-2011 LHC Main Magnet bus-bars maximum splice resistances T = 1.9 K 1nΩ Rspl,max = Rsegment – (n-1) * Rspl,avg MB 0.30 ± 0.09nΩ MQ 0.30 ± 0.31nΩ 2048 total ~30 bus bars > 1.2nΩ 10σ for MB 3σ for MQ 2011: Rspl,max LHC Main Magnet bus-bars segment resistances T = 1.9 K ±100pΩ 2010: Rspl,max The 30 highest bus-bar splice resistances at the end of 2011 versus the end of 2010. Distribution of maximum splice resistances in RB and RQ bus-bar segments Presented in IPAC’12 https://edms.cern.ch/document/1176353/1 TE-MPE-TM

  8. LS1 Quality Assurance open questions RB: 305±77pΩ 3σ=0.5nΩ(53) 10σ=1.1nΩ(3) • What will be the criterion to remake a cold splice? • If it is a simple threshold like 1.2nΩ, which is 3Ω for • quads, what about dipole distribution tale? They are safe? • What is a nature of the left part of distributions? • Is it measurement error or there is a “platinum” • category of joints? • Thanks to Higgs we have additional 2-3 months to answer. • Any ideas welcome. RQ*: 303±307pΩ 3σ=1.2nΩ (24) TE-MPE-TM

  9. LHC Main Magnet Bus Bar Segments Resistances, 2012 2012 RB ±200pΩ Dipole Bus Bars: No any significant changes of 1248 segment resistances are observed. 2011 2012 2011 2012 Quad Bus Bars: No significant changes of 800 segment resistances are observed, but except one! B18R2_4: 2.7nΩ -> 4.2nΩ (+1.5nΩ!) B18R2_3: 4.2nΩsince 2010?! Is it “artificial” or “real degradation”? See in the next slides recent ELQA results. RQ ±200pΩ 2011 TE-MPE-TM

  10. Bus Bar Segments: ELQA measurements in sector 23 Thanks to ELQA-team for the RQ bus bar resistance measurements in sector 23 during last TS#2, which was additional to the planned magnet resistance measurements. The detailed results will be presented by them later. Degradation? 3.3±0.1nΩ TE-MPE-TM

  11. Bus Bar Segments RQ.B34R2_3&4: nQPS versus ELQA 2011 2010 2012 3.8±0.3nΩ 6.2±0.3nΩ 3.4±0.1nΩ 5.8±0.1nΩ 2011 2010 2012 TE-MPE-TM

  12. Bus Bar Segments RQ.B18R2_3&4: nQPS versus ELQA 2011 2010 2012 4.4±0.3nΩ 4.1±0.3nΩ 2011 2010 2012 TE-MPE-TM

  13. Bus Bar Segments RQ.B18R2_3&4 2011 5340A • Compensation was not changed; • Board A and B behave the same; • What else? • Something inside of Cold Mass? • If so, why only in one aperture? 6100A 2012 TE-MPE-TM

  14. Internal Splices: nQPS versus ELQA nQPS Preliminary! ELQA Error bars: ELQA - about 1nΩ from linear fit; nQPS – distribution width divided by SQR(N), which is about (5-9)nΩ / 15; TE-MPE-TM

  15. Thanks! TE-MPE-TM

  16. Additional slides TE-MPE-TM

  17. Giorgio D’Angelo Mateusz Bednarek TE-MPE-TM

  18. Giorgio D’Angelo Mateusz Bednarek TE-MPE-TM

  19. RB: 98±22pΩ RQ: 113±26pΩ TE-MPE-TM

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