First proton source used at CERN's Proton Synchrotron (PS) which started operation in 1959. The PS was CERN’s first synchrotron. Activated in 1959, it was initially CERN's flagship accelerator, but when the laboratory built new accelerators in the 1970s, the PS’s principal role became to supply particles to the new machines. In the course of its history, it has juggled many different kinds of particles, feeding them directly to experiments or to more powerful accelerators. It is CERN's oldest accelerator still functioning today (2025). It is part of the accelerator chain that supplies proton beams to the Large Hadron Collider. With a circumference of 628 metres, the PS has 277 conventional (room-temperature) electromagnets, including 100 dipoles to bend the beams round the ring. The accelerator operates at up to 26 GeV. In addition to protons, it has accelerated alpha particles (helium nuclei), oxygen, sulphur, argon, xenon and lead nuclei, electrons, positrons and antiprotons. The source is a Thonemann type. In order to extract and accelerate the protons at high energy, a high frequency electrical field is used (140Mhz). The field is transmitted by a coil around a discharge tube in order to maintain the gas hydrogen in a ionised state. An electrical field pulse, in the order of 15kV, is then applied via an impulse transformer between anode and cathode of the discharge tube. The electrons and protons of the plasma formed in the ionised gas in the tube, are then separated. Currents in the order of 200mA during 100 microseconds have been obtained with this type of source.
