The loss of light yield with time in the CDF II scintillation counters

The CDF II Muon System has an important role in the CDF detector (FNAL, USA), particularly with regard to the investigations of processes involving heavy quarks. JINR and INFN physicists ensured the efficient functioning of the scintillation counters of this system.In course of several years we carried out the light yield measurements, at the ends farthest from photomultiplier, of the various types of scintillation counters installed at CDF. On the basis of the results obtained, conclusions about the aging rate of the counters and the long-range projection of their efficiency during physics data taking at CDF RUN II were made.The observation period was up to 10 years.