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
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. - PowerPoint PPT Presentation
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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
Splice Problem for Ansaldo MBs (and others ?)
2 March 2006 MTM-MAS Meeting P. Pugnat 3/16
Analysis of Quenches around 4.4 K 1D Model as a 1st approximation
• For x Lkx Sx xxT - H p (T – Tbath) + R I2 / L = 0
For x Lkx Sx xxT - H p (T - Tbath) = 0 (1)kx is the Cu thermal conductivity, H the heat transfer coefficient to liquid helium (H 500-5000 W/m2 K, for normal liquid He) & p is the wetted perimeter of the cable.
• The solutions of the system (1) is : T(x) = Tbath + (1 - e-L/2 cosh(x/)) R I2 / H p L for x LT(x) = Tbath + e-x/ sinh(L/2) R I2 / H p L for x L
where the thermal length = (kx Sx / H p )1/2.
• The maximum of the temperature increase in the splice is given by :T = T(0) - Tbath = (1 - e-L/2) R I2 / H p L
From Pre-Review January 2003, EDMS 369824
2 March 2006 MTM-MAS Meeting P. Pugnat 4/16
Analysis of Quenches around 4.4 K1D Model –
Interpretation
2 109
4 109
6 109
8 109
0.1
0.2
0.3
0.4
0.5
0.01
T R 250( )
T R 500( )
T R 750( )
T R 1000( )
108
109 R
• From the simple 1-D model with He cooling, T = T(0) - Tbath
= (1 - e-L/2) R IQ2 / H p L
• Problem to determine – The cooling term H– If heating or lack of cooling ?
• If the quench did not occurred in the splice an upper estimate of R of internal splices can be given from Tsharing(splice) 0.4 KFrom Roxie Bsplice/Bc 88.8%
From Pre-Review January 2003, EDMS 369824
2 March 2006 MTM-MAS Meeting P. Pugnat 5/16
Analysis of Quenches around 4.4 K Upper Limit of splices R that can be deduced
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,…
2 March 2006 MTM-MAS Meeting P. Pugnat 10/16
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…
Part II
Development of HF voltage signals during quenches for Ansaldo MBs
2 March 2006 MTM-MAS Meeting P. Pugnat 12/16
Electrical integrity of MBs during quenches: High Frequency V-signals
and the MB seems Ok,…
For other cases, an interturn short develops,…
2 March 2006 MTM-MAS Meeting P. Pugnat 13/16
Electrical integrity of MBs: larger amplitudes observed for Ansaldo MBs
Part III
Development of voltage signals during quenches with exponential
decay for Alstom MBs
2 March 2006 MTM-MAS Meeting P. Pugnat 15/16
Electrical integrity of MBs during quenches: V-jumps with exponential decay
Detected only on Alstom MBs, in particular: 1074, 1188, 1237, 1249, 1261, 1263, 1264, 1266, 1270, 1286, 1289
Looks like capacitor discharge in a gap with ms, where ?
2 March 2006 MTM-MAS Meeting P. Pugnat 16/16
Electrical integrity of MBs during quenches: Actions Taken
• 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