Design and Performance of the CNGS Secondary Beam Line

An intense muon-neutrino beam (10¹⁷<font face="Symbol">n_m</font> /day) is generated at CERN and directed towards the Gran Sasso National Laboratory, LNGS, in Italy, 732 km away from CERN. <br> In the presently approved physics programme, it is foreseen to run the CNGS facility with 4.5.10¹⁹ protons per year for five years. During a nominal CNGS cycle, i.e. every 6s, two nominal SPS extractions of 2.4.10¹³ protons each at 400GeV/c are sent down the proton beam line to the target.<br> The CNGS secondary beam line, starting with the target, has to cope with this situation, which pushes the beam line equipment and instrumentation to the limits of radiation hardness and mechanical stresses during the CNGS operation.<br> An overview of the CNGS secondary beam line is given. Emphasis is on the target, the magnetic focusing lenses (horn and reflector) and the muon monitors. The performance of the secondary beam line during beam commissioning and physics operation is discussed and measurements are compared with simulations.