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Electrical and calorimetric measurements and related software

Electrical and calorimetric measurements and related software. N. Catalan Lasheras, Z. Charifoulline, M. Koratzinos, A. Rijllart, A. Siemko, J. Strait, L. Tavian, R. Wolf. Outline. What did we see on 19 September 2008? Data from the final ramp

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Electrical and calorimetric measurements and related software

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  1. Electrical and calorimetric measurements and related software N. Catalan Lasheras, Z. Charifoulline, M. Koratzinos, A. Rijllart, A. Siemko, J. Strait, L. Tavian, R. Wolf

  2. Outline • What did we see on 19 September 2008? • Data from the final ramp • Data from the hardware commissioning powering tests • Investigation in other sectors of the machine • Calorimetric method, calibration • Sector 1-2 results • Electrical measurements: across the splices • Electrical measurements: inside the magnets • Verification from SM18 data • Summary for all sectors • Suspected cases • Conclusions

  3. 19 September 2009 Sector 34 • Expected temperature increase around 8mK. • Some sensors show between 10 mK and 13 mk increase • Parabolic dependence with time (hence current). • All of them around cell 24R3

  4. Sector 3-4. Plateau at 7 kA on 15th September. Temperature increase about 30 mK in one hour Valves blocked at 57.5% limit Strong temperature gradient across the cryogenic sub-sector Resistance estimated somewhere between 180 nOhms and 270 nOhms 7kA cycle in sector 3-4 on 15 September

  5. All sectors quick comparison S1-2 S2-3 S3-4 S4-5 +40 mK • All the current plateaux scrutinized for suspect temperature increase • Unstable conditions and dynamic temperature control prevent accurate calculations. 7 kA 7 kA 7 kA 9.3 kA Relative temp -10 mK 1-2 hour flat tops S5-6 S6-7 S7-8 S8-1 +40 mK 7 kA 7 kA 8.5 kA 7 kA Relative temp -10 mK

  6. Powering a group of circuits tests at the end of the sector commissioning Endurance test of 8 hours All circuits powered The cryogenic sub-sector 15R1 shows an excessive heating with current JT valve opens from 41% to 52% and is effective 3 to 5 h into the flat top The sector is overcooled after the powering Sector 1-2 PGC tests at 8.5 kA. Sub-sector 15R1 Temperature JT valve opening

  7. Procedures for repowering sector 1-2 • Dedicated procedure to assess the quality of the bus-bars joints • test sequence • risk analysis • conditions to go ahead with the next step • Two investigation methods • Calorimetric • Electric EDMS Document No. 973396

  8. The JT valve (CV910) is blocked at the right value to compensate the static heat loses before the powering Then, the temperature drift is mainly due to electrical resistive heating dissipated during the powering After powering the temperature shall remain constant Calorimetric measurements principle

  9. Assessment of the baseline slope (valve opening mismatch) Assessment of the temperature increase during powering plateau Assessment of the internal energy variation (J/kg) Assessment of the deposited energy assuming a mass of 26 l/m of He Methodology DU(DT)

  10. Experimental validation with en electrical heater 10 W applied on Q15R1

  11. Calorimetric measurements in sector 1-2

  12. Mobile system with eight channels Measure of all the bus-bar segments in the dipole circuit in one cell Only after analysis of the calorimetric measurements Measuring the dipole bus-bar splice resistance

  13. Bus-bar Splice Resistance Measurements • Measurement of voltage against current across bus-bar segments • Micro Volt accuracy, resolution in nOhms • No anomalous resistance measured in sector 15R1

  14. “Snapshots” using the QPS acquisition 60min @ 7kA • Uses the magnet instrumentation to measure the internal voltage across the dipole/quadrupole through the QPS acquisition 10min @ 6kA,5kA,4kA,…,0kA “Snapshots”: triggering PM-data collection of individual QPS for the dipoles A15R1 – C19R1 (15 magnets)

  15. Results from cells A15R1 to C19R1 • Found 100 nOhms in magnet B16R1 • Confirmed by snapshot during powering at 8500 A B16R1 => 2334 0.7mV/7kA=100nOhm 0.7mV*7kA=4.9W Snapshot on 03.09.08 : 0.85mV*8.4kA=7.1W

  16. Verification from SM18 data on magnet 2334 • Data from SM18 acquired during the cold tests confirms an inter-pole splice of 105 nOhm in magnet 2334 (B16R1)

  17. Calorimetric measurements in other sectors Sector 56: RB Sector 56: RQD + RQF Not reproducible Sector 67: RB Sector 67: RQD + RQF Confirmed electrically B32R6 Local bus-bar elec. measurements missing

  18. Snapshot for sector 6-7 on 03-Nov-08 • Snapshot on all subsector found a resistance of 49 nOhms in magnet B32R6 • Signals noisier than in other sectors

  19. Verification from SM18 data on magnet 2303 • Inter-pole resistance of 53nOhms in magnet 2303 confirmed by SM18 data.

  20. Sector 78: RB Sector 78: RQD + RQF Excluded after electrical measurements Local bus-bar elec. measurements missing Sector 81: RB Sector 81: RQD + RQF Excluded after electrical measurements

  21. Calorimetric measurements for dipole circuits 200 nW S3-4 100 nW 15R1 75 nW 50 nW 31R6 31R1 ? 25 nW S1-2 S5-6 S6-7 S7-8 S8-1

  22. Calorimetric measurements for quadrupole circuits 50 nW 25 nW S6-7 S5-6 S7-8 S8-1

  23. Summary of the findings in 2008 • Two more cases suspected at the limit of 2W in the quadrupole powering ~ 2 W @ 7 kA

  24. Summary of electrical measurements • Local bus-bar segment measurements done on demand. Not high resistances detected. • Snapshots both inside the magnets and in the bus-bar segments will be implemented from the new QPS system. (See R. Denz talk)

  25. Summary of measurements (1) suspected cases from calorimetric measurements 1 confirmed cases by electrical measurement. It may change with current!

  26. Conclusions • An abnormal temperature rise was seen as a precursor of the incident in sector 3-4. • Accurate/controlled measurements of temperature using the existing equipment can /have spot other potential risks. • Electrical measurements are needed to confirm and quantify the resistive splice but required special equipment and were only local. • Check of internal splices in the magnet is now done during cold tests in SM18. • The main circuits in four sectors have been fully investigated plus the dipole circuit in sector 1-2. Seven suspected cases have been found. Two were excluded, two confirmed and three are pending electrical measurements. • New QPS system will be able to measure the resistance of individual magnets and bus-bar segments in the LHC during dedicated tests. See R. Denz presentation in session 4. • Improved calorimetric measurements in preparation • The new powering procedures will demand mandatory calorimetric and electrical tests in ALL sectors at the beginning of the next LHC powering campaign

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