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About Worrying Cold Test Results of MBs

About Worrying Cold Test Results of MBs. MTM-MAS Meeting of Thursday 2 March 2006 Outline Ansaldo MBs Splice problems Development of HF voltage signals during quenches Alstom MBs Development of voltage signals during quenches with exponential decay. Part I.

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About Worrying Cold Test Results of MBs

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  1. About Worrying Cold Test Results of MBs MTM-MAS Meeting of Thursday 2 March 2006 Outline Ansaldo MBs Splice problems Development of HF voltage signals during quenches Alstom MBs Development of voltage signals during quenches with exponential decay

  2. Part I Splice Problem for Ansaldo MBs (and others ?)

  3. Analysis of Quenches around 4.4 K 1D Model as a 1st approximation From Pre-Review January 2003, EDMS 369824 MTM-MAS Meeting P. Pugnat 3/16

  4. Analysis of Quenches around 4.4 K 1D Model – Interpretation From Pre-Review January 2003, EDMS 369824 MTM-MAS Meeting P. Pugnat 4/16

  5. Assuming 12.5 % of surface cooled with H = 2 kW/m2 K Specification = 1.2 nW Analysis of Quenches around 4.4 K Upper Limit of splices R that can be deduced From Pre-Review January 2003, EDMS 369824 MTM-MAS Meeting P. Pugnat 5/16

  6. Conductor limited quench around 4.5 KOverview for Ansaldo MBs • “Past” history (EDMS 402365, LHC-Project-Report-807): • 6/9 MBs identified with a problem at 1 splice, only 2008 with a Quench Performance limitation detected around 4.5 K; it was accepted. • Most recent results: • 20/28 MBs identified with a problem at 1 splice, only 2051 with QP limitation detected around 4.5 K & 1.9 K; it was rejected. • MB List: 2043 (D2U), 2047 (D1L), 2051 (D1U), 2054 (D1U), 2092 (D2U), 2097 (D2U), 2123 (D1U), 2140 (D1L), 2164 (D2U), 2171 (D2L), 2179 (D2U), 2187 (D2U), 2192 (D1U), 2193 (D1L), 2200 (D1U), 2201 (D1U), 2202 (D2U), 2224 (D2U), 2247 (D2U), 2241 (D2U). • Splices are the weakest points in the coil. • What about long term stability ? How many cases not detected ? How many critical cases in the machine with beam losses ? MTM-MAS Meeting P. Pugnat 6/16

  7. Summary of Raw Data, need to be filteredPrepared by Janusz Kozak MTM-MAS Meeting P. Pugnat 7/16

  8. Case of 2051 Splice limitation at 1.9 K & 4.5 K 1.89 K, quench @ 12645 A LQA Localisation: Typical for a quench Localised around a splice Results of quenches at 4.54 K : 8978 A & 9026 A 1.89 K, VTaps Signal Results of quenches at 1.89 K : 12643 A - 12657 A MTM-MAS Meeting P. Pugnat 8/16

  9. Visit of September 2005 at Ansaldo; unfortunately only one pole could be visually inspected: Pole #1047 of 2262 Measurements: 4.33 mm 4.37 mm 4.37 mm 4.34 mm 4.35 mm Specification: 4.34  0.02 mm  Add a tolerance on Max-Min ? The larger values measured correspond to the splice zone where the solder is not completely melt,… We will see with the cold tests of 2262,… Possible explanation ? MTM-MAS Meeting P. Pugnat 9/16

  10. Summary on splices • Not a recent concern,… • The main reasons to have a quench around a splice can be: • Too high R  too much heating, • Cooling inefficiency, • Non-uniformity of R  “pathological” current redistribution. • Even if Ansaldo were pushed to increase its production rate, its interest is also to produce MBs with good splices, • Why 2051 tested a 2nd time in July 2005 not yet open ? • 2262 should be tested asap with anticryostats • At least one MB from Noell shows a similar problem; 3331 quenched at 10117 A around 4.5 K in D1L, but very poor statistics for this company… MTM-MAS Meeting P. Pugnat 10/16

  11. Part II Development of HF voltage signals during quenches for Ansaldo MBs

  12. and the MB seems Ok,… For other cases, an interturn short develops,… Electrical integrity of MBs during quenches: High Frequency V-signals MTM-MAS Meeting P. Pugnat 12/16

  13. Electrical integrity of MBs: larger amplitudes observed for Ansaldo MBs MTM-MAS Meeting P. Pugnat 13/16

  14. Part III Development of voltage signals during quenches with exponential decay for Alstom MBs

  15. Detected only on Alstom MBs, in particular: 1074, 1188, 1237, 1249, 1261, 1263, 1264, 1266, 1270, 1286, 1289 Electrical integrity of MBs during quenches: V-jumps with exponential decay Looks like capacitor discharge in a gap with t  1-5 ms, where ? MTM-MAS Meeting P. Pugnat 15/16

  16. Tune the Alarm system in the Automatic Quench Analysis (collaboration with AB/CO) to the “known” level of precursors Training & Daily Support to Test Coordinators and Operators Distribution of written doc. like EDMS Id 546522 to Test Coordinators and Operators i.e. Specification when additional quenches must be performed Special investigations & dedicated analysis Electrical integrity of MBs during quenches: Actions Taken MTM-MAS Meeting P. Pugnat 16/16

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