A recoil mass spectrometer for the XTU tandem at LNL

Abstract A wide acceptance recoil mass spectrometer has been designed to operate at small angles including 0° for use with the XTU tandem accelerator. Two 20° electric dipoles ( ϱ = 4 m, Eϱ = 12 MV) and one −40° magnetic dipole ( ϱ = 1 m, Bϱ = 10 kG m) are combined in a mirror-symmetric configuration similar to a proven design developed at the University of Rochester. Spatial focusing without intermediate cross-overs is achieved using the magnetic dipole plus a magnetic quadrupole doublet lens at the entrance. Weak quadrupole focusing in the dispersion plane avoids large chromatic aberrations. Two magnetic sextupole lenses combined with magnet boundary curvature remove focal plane tilt and minimize other second-order aberrations. Specifications are: solid angle acceptance >10 msr, energy acceptance ±20%, mass acceptance ±7%, mass dispersion 10 mm/% and mass resolution 1/280 at 5 msr and ΔE / E = ± 10%.