JAERI RECOIL MASS SEPARATOR

A recoil mass separator has been constructed at the JAERI tandem-boost er facility. It has a symmetric configuration of Q1Q2-ED1-MD-ED2-Q3Q4- O, where two electric dipoles ED1 and ED2, and the magnetic dipole MD are used to disperse reaction products by their mass/charge ratio (m/q ) and focus their energies. Two quadrupole doublets (Q1Q2 and Q3Q4) ar e used for focusing reaction products spread spatially, The octupole m agnet O is used to correct a non-linearity of the m/q dispersion. The m/q and energy acceptances are designed to be +/-4% and +/-12%; respec tively. In order to reduce a background originating from beams scatter ed from the ED1 anode, the anode is split into two parts, so that the primary beam can pass through without hitting the anode. The performan ce of the recoil mass separator has been tested by using the I-127 and Si-28 beams from the JAERI tandem accelerator. The capability of the background suppression at the beam direction is excellent and the obta ined mass resolution A/Delta A congruent to 300.