Recoil separator ERNA: ion beam specifications
D. Rogalla1 - M. Aliotta1 - C.A. Barnes2 - L. Campajola3 - A. D'Onofrio4 - E. Fritz1 - L. Gialanella1 - U. Greife1 - G. Imbriani3 - A. Ordine3 - J. Ossmann1 - V. Roca3 - C. Rolfs1 - M. Romano3 - C. Sabbarese4 - D. Schürmann1 - F. Schümann1 - F. Strieder1 - S. Theis1 - F. Terrasi4 - H.P. Trautvetter1
1 Institut für Physik mit Ionenstrahlen, Ruhr-Universität Bochum, Bochum, Germany
2 California Institute of Technology, Pasadena, USA
3 Dipartimento di Scienze Fisiche, Universita Federico II, Napoli and INFN, Napoli, Italy
4 Dipartimento di Scienze Ambientali, Seconda Universita di Napoli, Caserta and INFN, Napoli, Italy
Received: 25 October 1999 Communicated by B. Povh
Abstract
For improved measurements of the key astrophysical reaction 12C(
)16O
in inverted kinematics, a recoil separator ERNA is being developed at the 4 MV Dynamitron tandem
accelerator in Bochum to detect directly the 16O recoils with about 50% efficiency. Calculations
of the ion beam optics including all filtering and focusing elements of ERNA are presented. Since the
12C projectiles and the 16O recoils have essentially the same momentum, and since the
12C ion beam emerging from the accelerator passes through a momentum filter (analysing magnet), the
12C ion beam must be as free as possible from 16O contamination for ERNA to succeed. In the
present work, the 16O contamination was reduced from a level of
to a level
below
by the installation of Wien filters both before and after the analysing magnet.
The measurement of these and other beam specifications involved other parts of the final ERNA layout -
sequentially a Wien filter, a
dipole magnet, another Wien filter, and a 
E-E
telescope. The setup led to a measured suppression factor of
for the 12C ion
beam. The experiments also indicate that an almost free choice of the charge state for the 16O
recoils is possible in the separator.
Copyright Springer-Verlag
