A series of detailed Linac4 end-to-end simulations were conducted using RF-Track and benchmarked against PATH for validation. The simulations were performed from the RFQ entrance to the Linac4 end. In RF-Track, all the accelerating structures are described with calculated 3d field maps while the calculation time remains within minutes for half a million particles. Despite the inherent differences between the two codes, excellent agreement was found, almost particle by particle, in the case without space-charge effects. When space-charge effects were considered, the different algorithms implemented gave results that could not be compared particle-by-particle but were compatible in terms of emittance growth, beam size, bunch length, and energy spread. Particular care was put into handling space-charge effects in the transition between continuous and bunched beams, and the RF-Track's space-charge model was extended accordingly. As a result, we now have two complementary codes that accurately describe the dynamics of LINAC4. The results of this study are presented in this paper.

Since its completion in 2017, Linac4, the new 160 MeV proton injector for the CERN accelerator complex, has undergone some tests to assess and improve reliability, until being connected to the Proton Synchrotron Booster (PSB) during the 2018-2020 Long Shutdown 2 (LS2). The performance requirements for the LHC high-luminosity upgrade have been successfully met, and during its first three complete years of operation the linac has shown high reliability figures. Recent improvements of the H- ion source enable the increase of the beam current from the nominal 35 mA to 50 mA, opening the possibility for increasing the intensity of the Booster beams, for the benefit of the experimental programmes. This paper presents the operational experience and reliability of Linac4 in its first three years of operation.