• M. Solfaroli Camillocci, G. Arduini, B. Bellesia, J. Coupard, K. Dahlerup-Petersen, M. Koratzinos, M. Pojer, R. Schmidt, A.P. Siemko, H. Thiesen, A. Vergara-Fernández, M. Zanetti, M. Zerlauth
  CERN, Geneva

On 19th September 2008 the Large Hadron Collider (LHC) experienced a serious incident, caused by a bad electrical joint, which stopped beam operation just a few days after its beginning. During the following 14 months the damage was repaired, additional protection systems were installed and the measures to avoid a similar incident were taken (i.e. new layer of the Magnet Quench Protection System [nQPS], more efficient He release valves). As a consequence, a large number of powering tests had to be repeated or carried out for the first time. The re-commissioning of the already existing systems as well as the commissioning of the new ones has been carefully studied, then performed taking into account the history of each of the eight LHC sectors (warm-up, left at floating temperature,'). Moreover, a campaign of measurements of the bus-bar splice resistances has been carried out with the nQPS in order to spot out non conformities, thus assessing the risk of the LHC operation for the initial energy level. This paper discusses how the guidelines for the LHC 2009 re-commissioning were defined, providing a general principle to be used for the future re-commissioning.

• K. Foraz, J. Coupard, S. Grillot
  CERN, Geneva

The first LHC shut-down started in fall 2008, just after the incident on the 19th of September 2008. In addition to the typical work of a shut-down, a large number of interventions, related to the 'consolidation after the incident' were performed in the LHC loop. Moreover the amount of work increased during the shut-down, following the recommendations and conclusions of the different working groups in charge of the safety of the personnel and of the machine. This paper will give an overview of the work performed, the organization of the coordination, emphasizing the new safety risks (electrical and cryogenic), and how the interventions were implemented in order to ensure both the safety of personnel and a minimized time window.