• 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.

• T.T. Boehlen, R.W. Assmann, C. Bracco, B. Dehning, S. Redaelli, Th. Weiler, C. Zamantzas
  CERN, Geneva

The LHC collimators are protected against beam caused damages by measuring the secondary particle showers with beam loss monitors. Downstream of every collimator an ionisation chamber and a secondary emission monitor are installed to determine the energy deposition in the collimator. The relation between the energy deposition in the beam loss monitor and the collimator jaw is based on secondary shower simulations. To verify the FLUKA simulations the prototype LHC collimator installed in the SPS was equipped with beam loss monitors. The results of the measurements of the direct impact of the 26 GeV proton beam injected in the SPS onto the collimator are compared with the predictions of the FLUKA simulations. In addition simulation results from parameter scans and for mean and peak energy deposition with its dependencies are shown.