In addition to the four original Cavities, a smaller fifth cavity was added in 1979. It is operated at 150 megahertz as a flat-top cavity, and has enabled a significant increase in the number of extracted particles. Since 2008 all the old aluminium cavities of the Ring Cyclotron have been replaced with new copper cavities. These allow higher voltage amplitudes and thus a greater acceleration of the protons per revolution. The number of revolutions of the protons in the cyclotron could thus be reduced from approx. 200 to 186, and the distance travelled by the protons in the cyclotron decreased from 6 km to 4 km. With a beam current of 2.2 mA, this proton facility at PSI is currently the most powerful continuous particle accelerator in the world. The 1.3 MW strong proton beam is directed towards the muon source (SμS) and the spallation neutron source (SINQ).