The cabling of the LHC detectors moves up a gear thanks to the automation of testing
Cables are omnipresent in the four large LHC detectors. During the second Long Shutdown (LS2), the cabling team led by Gianluca Canale installed 3700 signal cables (81 km in total!) and 6000 connectors to the ALICE detector. More than 800 connectors have been installed in ATLAS, where they will power the detector’s new small wheels. These achievements, which are helping to keep the LS2 moving forward, are the results of the efficiency of the cabling team within the Experimental Area group (EN-EA) in charge of the testing and installation of the cables. The team’s efficiency has been boosted by the development of an automated cable testing system in collaboration with the Measurement, Test and Analysis section of the Survey, Mechatronics and Measurements group (EN-SMM-MTA).
Testing the cables in the experiments is crucial as the smallest error can take on unexpected proportions. As Gianluca Canale explains, cables are normally replaced only as a last resort, after the breakdown of a machine - whether a detector or an aeroplane - as the replacement process is painstaking. Consequently, there is no room for error in the tests that are carried out before their installation. Until recently, the tests were carried out manually, by measuring the leakage current between the many filaments of an individual cable subjected to a voltage of up to 5000 V. A single cable test thus involved a hazardous two-hours long handwork for two technicians, around 80% more than the time it takes for a “HiPotCT” automated test. In the case of the ATLAS and ALICE cabling campaigns, automation has reduced the testing time by a total of 350 hours, which equates to a saving of 16,000 CHF.
The “HiPotCT” is a compact box that can be transported deep into the heart of the detectors. It analyses with great precision the internal electrical characteristics of the cables such as their leakage current. The software, developed by Stian Juberg, who was a technical student in the EN-SMM-MTA section at the time, allows all the cable filaments to be programmed for testing, thanks to a relay system coupled with a laptop. The process simply requires the cable to be connected and the software to be launched; after half an hour or so of humming, the device delivers its diagnosis to Maria Papamichali, leader of the “HiPotCT” project. In her role as a member of the VIA (“volontariat international en administration”) programme and then as a fellow, Maria was behind the specifications of the system and was in charge of all the electronic aspects and their final integration into a portable system.
“Working in close collaboration with Stian on the development process led to something that industry does not offer by targeting the specific requirements of HiPotCT, without excluding the possibility of adapting the device to work with other cables and connectors in the future”, says Maria. The project, financed by LETEM (LHC Experiments Technical and Engineering Meeting) has benefitted from bringing together the expertise acquired by the MTA team in the context of projects to automate high-voltage measurements, such as the LHC magnet tests in SM18, and the expertise of the cabling team, which is the result of a desire to create a centre of excellence in this field at CERN.
Thanks to “HiPotCT”, cabling campaigns are faster and the risk of breakdowns during machine operation is reduced. Over and above this technical aspect, however, Gianluca underlines that his team’s commitment is the key to the success of the major LS2 cabling campaigns: a professional and enthusiastic team consisting of fellows and members of the VIA programme, who have been given the opportunity to take on responsibility and to innovate. The result: as far as detector cabling is concerned, the LS2 work is almost complete.
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