In the nineties the new method for investigation of rare muon decays has been developed in PNPI, and the apparatus for this experiment was constructed. The method is based upon registration of high energy electrons of muon decay with a wide-aperture magnet spectrometer. In 1992-1995 this apparatus has been used in the experiment on muonium-antimuonium conversion, performed by JINR-PNPI collaboration on the beam of surface muons of JINR phasotron. In that experiment the new estimates of upper experimental limits for conversion probability had been obtained and also of the weak interaction constant in this process (See Historical overview of main activities).

    In 1999 the program of research in rare and exotic muon decays has been maintained in PNPI and JINR. As the task number one, the search for neutrinoless decay of muon into electron and massless Goldstone boson (familon) has been adopted, and the experimental setup is to be prepared for this experiment.
(For more detail review see article:
     1) http://www.jinr.ru/~muspin/familon,
     2) preprint PNPI № #2380, 2000 ,
    3) The FAMILON experiment: conception and simulation.

    The technical project of this experiment has been developed in PNPI, methodical studies had been carried out, making use of the existent apparatus. A test run for the "Familon" project has been carried out on the beam of the JINR phasotron. The setup parameters and the background conditions had been studied. The first 105 events have been triggered and stored for analysis. The volume of research and development required for fulfillment of the experimental program has been estimated. In 2002-2003 the studies were performed on the muon beams of PNPI and JINR in order to improve the energy resolution of the spectrometer to the level 10^-3 (See activ_target.pdf).

    The project "Familon" is being carried out by joint efforts of four Russion institutes: PNPI, JINR, ITEP and Kurchatov Institute (See Current Projects).