Quality control of LHC electrical interconnections to be produced during the 2009 shutdown

Since the functional properties of the LHC electrical interconnections can not be measured in-situ, Quality control (QC) must rely on visual and geometrical inspections, the analysis of production data, and in the case of 13 kA splices on ultrasonic tests. New are:An ultrasonic test will be performed for 100 % of the produced 13 kA

splices.Temperature cycle data, recorded with an independent system (in

addition to the temperature recording by inductive soldering machines) will be regularly analysed.

Key process data (e.g. ultrasonic weld duration) will be analysed on-line for US weld process control.

Thickness of all 13 kA splices will be measured and analysed with control charts.

Photos of all 600 A and 13 kA splices will be taken. Whenever possible give operators tools in hand that they can

control their work themselves. Quality assurance of the LHC electrical interconnections includes

preparation work, e.g. electrical connection and disconnection before and after cold test and 13 kA cable stabilisation, in SMI2 and SMA18. C. Scheuerlein – LHC risk review,

5.3.2009

Ultrasonic testing of main bus bar splices All main bus bar splices to be produced during the

2009 shutdown will be US tested [i] by a member of the electrical connections QC team. A good US test result indicates that some Sn-Ag alloy has melted during the splice production process.Cryodipoles 2334 and 2440 with defective inter-pole splices are a treasure for testing QC tools.

4 out of 4 US measurements performed on the two splices with very high contact resistance show bad US transmission, indicating lack of Sn-Ag solder between Cu U-piece and Cu-wedge. For all other splices tested so far during the 2009 shutdown, the US test gave 4 out of 4 good US signals.

C. Scheuerlein – LHC risk review, 5.3.2009

[i] F. Caspers, T. Kroyer, J. Kulka, J.-P. Tock, L.R. Williams, LHC-PROJECT-Report-1032

US test of defective interpole splice in cryodipole 2334

Cryodipole 2334 left splice

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Cryodipole 2334 right splice

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US test clearly detects very bad splices as those found in dipoles 2334 and 2440.

C. Scheuerlein – LHC risk review, 5.3.2009

Analysis of production data recorded during inductive soldering

An independent temperature recording system has been implemented in the inductive soldering process in order to record and analyse temperature cycle data for all 13 kA splices.

Both teams performing inductive soldering of 13 kA splices have been equipped with a data logger that records the temperature cycles, measured with a K-type thermocouple that is clamped onto the upper Cu profile of the splice to be soldered.

Analysis of temperature cycles is done to detect deviations from standard heating cycle, to make sure that the Sn-Ag melting temperature was exceeded and that no splice overheating occurred.

C. Scheuerlein – LHC risk review, 5.3.2009

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Use of control charts for US welding process

Monitor key process data (e.g. US weld duration) over time in order to observe changes in the US welding process (e.g. sonotrode usage or misalignment).

A software for fast analysis of production data has been written by L. Deniau and will be implemented in the production process in order to stop the process in case of strong variations of process parameters.

C. Scheuerlein – LHC risk review, 5.3.2009

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Lower control limit

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Qualification of processes, equipment and operators before production, and audits during production All operators performing the electrical interconnections, as

well as the equipment used, are qualified through the production of test samples, which are characterised by contact resistance measurements (TE-CRG-Cryolab), tensile strength measurements and metallographic analysis (EN-MME-Metallurgy lab.) .

During production regular audits will be performed for testing the equipment and processes used to produce splices.

Contact resistance vs. compression of ultrasonic welds of spool line M wires with US3 and US7

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C. Scheuerlein – LHC risk review, 5.3.2009