Radiation levels in the CERN Large Electron Positron collider during the LEP 2 phase (68–105 GeV)

The CERN Large Electron Positron (LEP) collider was in operation from 1989 to 2000. At the end of 1995 the LEP 2 phase began, with the progressive upgrade of the collider energy above the W pair production threshold, until the final energy of 105 GeV per beam. During the 11-year operation an extensive radiation survey program monitored the dose levels inside and around the installation. The radiation levels monitored in the underground areas and on the surface during 1989–1995 (LEP 1 phase) were discussed in a previous paper. The aim of this paper is to complete the data reported earlier. This paper first gives an overview of the radiation levels in the LEP tunnel and in other underground areas, and then discusses measurements of the photon radiation performed in the machine tunnel at each energy increase. An estimate of neutron sources, measurements of radiation streaming through ducts and shafts and some results of measurements of synchrotron radiation from the wigglers are given next. Residual dose rates are then briefly addressed. Finally, an overview is provided of the radiation levels recorded on ground surface during operation, both at the LEP access points and at some reference areas in the French and Swiss countryside.