My memories of an early accelerator operation at the KEK-PS main ring. Struggles of young researches, who belong to the main ring magnet group

His memories at the main ring group from 1972 to 2006 are talked. A regular member of KEK-PS main ring group was seven in 1972. Measurement of the magnetic field of electromagnet, from beam incident to acceleration of main ring, and remolding of main ring in 1979 are described. Operating conditions of PS accelerator in 1970's, arrangement of magnets of PS-main ring, main electromagnets in main ring tunnel, measurement method of magnetic field of beam bending magnet, k-distribution of core, measurement of inductance of beam bending magnet, record at the first incident of main ring, change of vertical alarm of quadrupole magnet of main ring, effects of vacuum chamber on the magnetic field, and changes of magnetic field distribution by vacuum chambers are illustrated. (S.Y.)