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RRR Measurements in S23 during LS1 Emmanuele Ravaioli Daniel Rasmussen Scott Rowan Thanks to Z. Charifoulline, R. Denz, J. Steckert, H. Thiesen, A. Verweij

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RRR Measurements in S23 during LS1 Brief Intro and Motivation Test Proposal and Resources Measurement Method Method Limitations Status of Proposal/Conclusion

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Brief Introduction What is RRR? – Residual Resistivity Ratio – Practically defined as the ratio between a material’s resistivity at room temperature to and just above a superconducting state. – There are known relations of resistivity of copper and RRR What is the importance of RRR accuracy? – Crucial parameter in the prediction of Ohmic losses of in the case of quench – Increases accuracy of hot-spot calculations – Regularly used parameter in magnet/circuit quench simulations (PSpice/ROXIE/QP3) – Greatly improves understanding of circuit behaviour – Used in determining QPS threshold S. Rowan – 05/12/2012

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Motivation for Measurements Main motivation is the uncertainty of current RRR values – Usually just defined as a minimum value; e.g. RRR > 100 – Value could vary at extremes from 50-300 and this potential error of >100% can drastically effect simulation results and inherent understanding of circuit behaviour S. Rowan – 05/12/2012 Simply varying RRR from 50-300 produces significant differences in time constant

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Test Proposal To measure as accurately as possible the RRR of the magnets and busbars of all circuits (except RB/RQ) in S23 during the unique cryogenic conditions planned for the CSCM type test (20K) – Aim to only use currently available operation processes – Aim to use only automated measurements via Logging system – Aim to not have to enter the tunnel, measurements carried out entirely via CCC – Aim to run as many tests in parallel as possible – Aim to run test in parallel with CSCM, i.e. do not interfere with proceedings What is intended? – Simply send low current pulse(s) through each circuit and later calculate the RRR via measurements stored in the logging database Amount of pulses/length of plateau to be determined but not of paramount priority Likely to be just be a <5mins plateau – Current values are to be circuit dependant to stay within QPS thresholds S. Rowan – 05/12/2012

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Measurement Method Ideal case for measurement Circuits in S23 intended for measurements – RQX, IPDs, IPQs, 600 A (w&w/o R//), 80-120 A, 60 A S. Rowan – 05/12/2012

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Measurement Method Specific case for measurement of 600A w R// S. Rowan – 05/12/2012 Example: RCS.A23B1 154 magnets QPS thresholds U_tot<2 V if current < 50 A QPS resolution U_tot 4.89 mV I_res 10 mA I_measU_totU_magnetsU_busbarsI_mag 0.2 A0.49 V0.42 V0.07 V0.17 A 0.4 A0.98 V0.84 V0.14 V0.33 A 0.8 A1.95 V1.68 V0.28 V0.66 A

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Measurement Method Specific case for measurement of IPDs S. Rowan – 05/12/2012 Example: RQ10.R2 I_measU_1_B1U_2_B1 U_1_B1 +U_2_B1 U_1_B1 -U_2_B1 5 A201 mV193 mV394 mV8.4 mV 10 A402 mV385 mV788 mV16.9 mV 20 A805 mV771 mV1.576 V33.7 mV QPS thresholds U_1_B1+U_2_B1<2 V if current < 50 A U_1_B1-U_2_B1<100 mV QPS resolution U_sum 4.89 mV U_diff 0.24 mV I_res 10 mA

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Method Limitations The devised method aims to maximise amount of measurements/data acquisition while minimising resources, but at a cost of accuracy – Chose quantity of measurements of accuracy Known Method Limitations (to be taken into account in final RRR calculation) – Temperature (Cryo temp may vary during test) – Measured Voltage (accuracy of logging database) – Measured Current (accuracy of logging database) – Length of the busbar (calculated via mechanical drawings) – Cross-section of the busbar – Magnet Parallel Resistances R// Preliminary sensitivity analysis estimates method errors of 5-10% – At the moment uncertainty can exceed 100% S. Rowan – 05/12/2012

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Conclusion/Status of Proposal Each circuit type has been individually analysed to determine safe measurement currents (i.e. no QPS triggering) Method of RRR calculation has been established for each circuit type Aim to have official test proposal drafted before Christmas break and validated in January Brief Conclusion – Aim to measure RRR in all circuits (except 13kA) of S23 during CSCM type test – Estimated time of all tests: An evening? Solely depends on what can be tested in parallel – Will not interfere with CSCM proceedings in anyway – Low power tests, minimal damage risk – No requirement for alterations of program/operations – No Specialists required – No foreseen delays or setbacks S. Rowan – 05/12/2012

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