• J. Strait
  Fermilab, Batavia
• R. Bailey, M. Bednarek, B. Bellesia, N. Catalan-Lasheras, K. Dahlerup-Petersen, R. Denz, C. Fernandez-Robles, R.H. Flora, E. Gornicki, M. Koratzinos, M. Pojer, L. Ponce, R.I. Saban, R. Schmidt, A.P. Siemko, M. Solfaroli Camillocci, H. Thiesen, A. Vergara-Fernández
  CERN, Geneva
• Z. Charifoulline
  RAS/INR, Moscow
• P. Jurkiewicz, P.J. Kapusta
  HNINP, Kraków

The incident of 19 September 2008 at the LHC was apparently caused by a faulty inter-magnet splice of about 200 nOhm resistance. Cryogenic and electrical techniques have been developed to detect other abnormal splices, either between or inside the magnets. The quench protection system is used in a special mode to measure the voltage across each magnet with an accuracy better than 0.1 mV, allowing internal splices with R > 10 nOhm to be detected. Since this system does not cover the bus between magnets, the cryogenic system is used in a special configuration* to measure the rate of temperature rise due to ohmic heating. Accuracy of a few mK/h, corresponding to a few Watts, has been achieved. This allows detection of excess resistance of more than a few tens of nOhms in a cryogenic sub-sector (2 optical cells). Follow-up measurements, using an ad-hoc system of high-accuracy voltmeters, are made in regions identified by the cryogenic system. These techniques have detected two abnormal internal magnet splices of 100 nOhms and 50 nOhms respectively. In 2009, this ad-hoc system will be replaced with a permanent one which will monitor all splices at the nOhm level.

*L. Tavian, Helium II Calorimetry for the Detection of Abnormal Resistive Zones in LHC Sectors, this conference.

• B. Bellesia, M.P. Casas Lino, R. Denz, C. Fernandez-Robles, M. Pojer, R.I. Saban, R. Schmidt, M. Solfaroli Camillocci, H. Thiesen, A. Vergara-Fernández
  CERN, Geneva

The Large Hadron Collider has 1572 superconducting circuits which are distributed along the eight 3.5 km LHC sectors. Time and resources during the commissioning of the LHC technical systems were mostly consumed by tests of each circuit of the collider: the powering tests. The tests consisted in carrying out several powering cycles at different current levels for each superconducting circuit. The Hardware Commissioning Coordination was in charge of planning, following up and piloting the execution of the test program. The first powering test campaign was carried out in summer 2007 for sector 7-8 with an expected duration of 12 weeks. The experience gained during these tests was used by the commissioning team for minimising the duration of the following powering campaigns to comply with the stringent LHC Project deadlines. Improvements concerned several areas: strategy, procedures, control tools, automatisation, resource allocation led to an average daily test rate increase from 25 to 200 tests per day. This paper describes these improvements and details their impact on the operation during the last months of LHC Hardware Commissioning.