[en] The CERF facility, set-up at CERN in the early nineties, provides mixed radiation fields representative of those found outside the shielding of high-energy hadron accelerators and sufficiently similar to the cosmic ray field encountered at 10-20 km altitude. This allows instrumentation to be tested, inter-compared and calibrated at CERN and subsequently used for either in-flight measurements on aircraft or radiation protection surveys around particle accelerators. The CERF hadron beam is produced by the primary 450 GeV/c proton beam from the Super Proton Synchrotron (SPS) on the T4 production target. The secondary beam originating from the T4 target is composed of 61% positive pions, 35% protons and 4% positive kaons with a momentum of 120 GeV/c. The beam is delivered to CERF with a typical intensity in the range 10⁶ to 10⁸ particles per SPS beam extraction