An improved method of fission track (FT) sample preparation was developed, in which the detector of fission track and the
layer containing particles are separated, in order to apply the FT-thermal ionization mass spectrometry (TIMS) for particle
analysis of safeguards environmental samples. The developed FT sample enabled us to detect the particle of interest simply
by observing the fission tracks. The process of particle identification was difficult due to the discrepancy between the position
of the particles and fission tracks, which were observed in the conventional FT sample. The proposed method has significantly
resolved this problem.