Cables are omnipresent in the four large LHC detectors. During the second Long Shutdown (LS2), 896 SHV connectors have been installed on the small wheels of the ATLAS detector, and 3200 signal cables (70 km in total!) and 6000 connectors have been added to the ALICE detector. These results, which are helping to keep the LS2 moving forward, have been achieved thanks to 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, head of the cabling team, 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 current of 5000 V. A single cable test thus involved four hours of hazardous work, around 80% more than an 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 portable box into which cables are plugged to test their insulation resistance. 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. 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. In her role as a member of the VIA ("volontariat international en administration") programme and then as a fellow working in the cabling team, 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.
"This solution would only have been possible at CERN, where services help and support each other. Working in close collaboration with Stian on the development process allowed us to target 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 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 The good relationship between the services has led to something that industry does not offer: a device that is both portable and able to perform tests at very high voltages.
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 young team consisting of trainees, members of the VIA programme and fellows, 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.
