• S. Redaelli, O. Aberle, R.W. Assmann, C. Bracco, B. Dehning, M. Jonker, R. Losito, A. Masi, M. Sapinski, Th. Weiler, C. Zamantzas
  CERN, Geneva

A full scale prototype of the Large Hadron Collider (LHC) collimator was installed in 2004 in the CERN Super Proton synchrotron (SPS). During three years of operation the prototype has been used extensively for beam tests, for control tests and also to benchmark LHC simulation tools. This operational experience has been extremely valuable in view of the final LHC implementation as well as for estimating the LHC operational scenarios, most notably to establish procedures for the beam-based alignment of the collimators with respect to the circulating beam. This was made possible by installing in the SPS a first prototype of the LHC beam loss monitoring system. The operational experience gained at the SPS, lessons learnt for the LHC operation and various accelerator physics effects that could limit the efficiency of the collimator alignment procedures are presented.

• B. Dehning, D. Bocian, T.T. Boehlen, E. Effinger, J. Emery, F. Follin, V. Grishin, E.B. Holzer, H. Ikeda, S. Jackson, D.K. Kramer, G. Kruk, P. Le Roux, J. Mariethoz, M. Misiowiec, L. Ponce, C. Roderick, M. Sapinski, M. Stockner, C. Zamantzas
  CERN, Geneva
• A. Priebe
  Poznań University of Technology, Poznań

The LHC beam loss monitoring system (BLM) consists of about 4000 monitors observing losses at all quadrupole magnets and many other likely loss locations. At the first LHC operation in August and September 2008 all monitors were active and used to observe the losses during the initial beam steerings, at collimators, at the LHC dump and during aperture scans. The different loss patterns will be discussed and compared with the expectations originating from simulations. The observed signals of the BLM system will be analysed in terms of response time, sensitivity cross talk between channels and noise performance.