Radio frequency superconductivity at CERN: a status report

Up to 1984 the efforts in superconducting (s.c.1 cavity development at CERN were mainly concentrated on 500 MHz cavities [l], leading to the test of a 5-cell, 500 MHz cavity at PETRA [2]. The results confirmed that the achievable accelerating fields do not decrease at lower frequencies as strongly as previously suspected. Therefore, it was decided in 1984 to concentrate efforts on 352 MHz cavities [3,4]. This frequency choice is suggested by the fact that LEP will be equipped at the beginning with 128 Cu cavities at 352 MHz which will bring up energies to 55 GeV/beam [51. There is an obvious interest to install at a later stage S.C. cavities with the same frequency and to use at maximum the existing installation of radio frequency (r.f.1 power sources. With the installed r.f. power of 16 MW, LEP could be upgraded to 90 GeV by using S.C. cavities [6]. This will require the construction, testing and installation of several hundred of s.c. cavities, therefore arguments of economy and reliability are of outstanding importance.