CNGS Muon Monitors

The CERN Neutrinos to Gran Sasso (CNGS) beam facility uses two muon detector stations as on-line feed back for the quality control of the neutrino beam. The muon detector stations are assembled in a cross-shaped array to provide the muon intensity and the vertical and horizontal muon profiles. Each station is equipped with 42 ionisation chambers, which are originally designed as Beam Loss Monitors (BLMs) for the Large Hadron Collider(LHC). The response of the muon detectors during the CNGS run 2007 and possible reasons for a non-linear behaviour with respect to the beam intensity are discussed. Results of the CNGS run 2008 are shown: The modifications done during the shutdown 2007/08 were successful and resulted in the expected linear behaviour of the muon detector response.