The goal of the proposed three-stage cylotron complex is to deliver a continuous external high energy (in the 1 GeV range) proton beam of the order 10 mA for driving the Energy Amplifier, a hybrid sub-critical nuclear system, which is being deveoped at CERN and whose principles have been successfully tested during the first experimental programme [1]. This accelerator consists of two 10 MeV injectors feeding a four separated sector magnet iscochronous ring from which a 120 MeV beam is injected into a large ring cylotron with ten separated spiral sector magnets. In this final booster six cavities operating at 42 MHz will provide an egenrgy gain per turn of 6 MeV in order to get a sufficient turn separation on the extraction radius. The maximum available current depends mainly on the beam quality on the extraction radius of the various cylotrons. This report summarizes the main fields of work carried out during these preliminary studies.