Velocity distribution of RIKEN IGISOL ion beams

The RIKEN GARIS/IGISOL is an isotope formation and separation device which does not use a thermionic ion source. The feature of this system is that the formation and separation of short life nuclei have become feasible regardless of the chemical properties of nuclides. The objective is to install a laser nuclear spectroscope to this GARIS/IGISOL and to do the systematic research on nuclear structure. Especially in high melting point elements, the isotope separation using thermionic ion sources is difficult, and the research on unstable nuclei is delayed. Accordingly, to carry out the research on the unstable nuclei in high melting point region using the GARIS/IGISOL is significant for examining nuclear structure. However, IGISOLs are inferior in their mass resolving power to other isotope separators, and unsuitable to laser nuclear spectroscopy, as the resolution of laser nuclear spectroscopy is determined by the velocity distribution of ion beam. In order to directly measure the velocity distribution, the measurement of the velocity distribution in the IGISOL using a laser was carried out, and the results are reported in this paper. The principle of velocity distribution measurement by Doppler broadening, the experimental setup, the measurement and the introduction of squeezer are described. (K.I.)