Sn at 280 MeV/u

We have produced very neutron-rich Pd isotopes around N = 82 by projectile fragmentation of a radioactive isotope (RI) beam of ¹³²Sn using the BigRIPS separator and the ZeroDegree spectrometer at RIKEN RI Beam Factory.

A two-step reaction scheme [1], a projectile fragmentation of RI beams, has been proposed for production of mid-heavy very-neutron-rich RIs around N = 82. In this scheme, a long-lived RI (e.g. ¹³²Sn) is produced by ISOL and post-accelerated, then more exotic nuclei (^125-128Pd) are produced by fragmentation. This scheme may have an advantage for obtaining yields of such RIs compared to in-flight fission of ²³⁸U or direct production by ISOL. The in-flight fission of ²³⁸U is useful for production of mid-heavy nuclei, whereas the production cross-sections decrease drastically in such exotic region. On the other hand, much yields are obtained in target by ISOL, whereas exotic nuclei with half-lives < ~1 ms cannot be supplied because of bad extraction efficiency.

To evaluate the usefulness of the two-step reaction scheme, we have measured the cross sections of the neutron-rich RIs produced from the ¹³²Sn beam and compared their production yields by this scheme and the in-flight fission of ²³⁸U.

Reference

[1] K. Helariutta et al., Eur. Phys. J. A 17 (2003) 181.