Training in the Main LHC Dipoles Episode I: Evolution during Production, Quench Location, and Storage Time

In 2008, hardware commissioning of the LHC showed larger than expected loss of training retention for the magnets manufactured in Firm3. In this report we review the training data during surface test at SM18 along the production to point out difference between Firms. In particular, we study (i) the evolution during the production, (ii) the quench location, and (iii) the behaviour after thermal cycle. Some specificity of the behaviour of Firm3 magnets are singled out, namely a slower training at lower field, and some differences in the location of the second and third virgin quenches. Moreover, the Firm3 magnets also showed a larger loss of training retention after thermal cycle. The correlations between training in virgin conditions and after a thermal cycle are used to work out an estimate of the training in each sector. This partially explains the behaviour observed in sector 5-6 in 2008. Finally, we study the correlation between retraining during hardware commissioning and two features of the production: the storage time of the cold masses with or without cryostat. In both cases there is no evidence of any correlation.