beams in 1978. It kept the same beam energy of 50 MeV, but allowed for more intense beams with beam currents of up to 150 mA and a longer pulse duration of 200 μs. Originally, it had been discussed to further upgrade the first Linac instead of building a completely new linear accelerator. However, it quickly became clear that the costs of such an update would almost be as expensive as the new Linac. Another fact in favor of this new construction was the possibility to ensure a smooth transition from one Linac to the other without any downtime in between. Also this two linac approach meant that the old Linac could provide a back-up for the new Linac for the first years of operation. Construction of Linac 2 started in December 1973, with an estimated budget of 21.3 million CHF, and was completed in 1978. Linac 2 was 36 meters long and was based at ground level at the main CERN site. It was located in a building parallel to the old Linac tunnel. Throughout its lifetime, Linac 2 went through several updates to keep up with the advances of CERN's accelerator system. The most important upgrade was the replacement of the old 750 kV Cockcroft-Walton generator with a Radio-frequency quadrupole in 1993. This raised the output current to 180 mA. In the late 2000s, it was considered whether to upgrade Linac 2 or build a new linac for injecting particles into HL-LHC. The decision was in the end made to build a new accelerator, the Linac4 to succeed Linac 2 in 2020. Linac 2 was switched off 12 November 2018 at 15:00 by CERN's Director of Accelerators, and was subsequently decommissioned as part of the LHC Injector Upgrade project. In the decommissioning process, Linac 2 was disconnected from the other accelerators of CERN, so it can no longer used to inject particles into CERN accelerators or experiments. However, much of the Linac 2 accelerator hardware is left (as of October 2019) in place untouched, with the hope of making it into an exhibition about the history of CERN. Linac 3 Linac 3, also referred to as the Lead Linac was constructed inside the former tunnel of Linac 1 and got commissioned in the summer of 1994 (construction started October 1992). It had been specially constructed to accelerate heavy ions, after tests with Linac 1 and an increasing demand