Recoil separator ERNA: ion beam specifications

D Rogalla, M Aliotta, C A Barnes, L Campajola, A D'Onofrio, E Fritz, L Gialanella, U Greife, G Imbriani, A Ordine, J Ossmann, V Roca, C Rolfs, M Romano, C Sabbarese, D Schurmann, F Schumann, F Strieder, S Theis, F TerrasiH P Trautvetter

Research output: Contribution to journalArticlepeer-review


For improved measurements of the key astrophysical reaction C-12(alpha, gamma)O-16 in inverted kinematics, a recoil separator ERNA is being developed at the 4 MV Dynamitron tandem accelerator in Bochum to detect directly the O-16 recoils with about 50% efficiency. Calculations of the ion beam optics including all filtering and focusing elements of ERNA are presented. Since the C-12 projectiles and the O-16 recoils have essentially the same momentum, and since the C-12 ion beam emerging from the accelerator passes through a momentum filter (analysing magnet), the C-12 ion beam must be as free as possible from O-16 contamination for ERNA to succeed. In the present work, the O-16 contamination was reduced from a level of 1 x 10(-11) to a level below 2 x 10(-29) 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 60 degrees dipole magnet, another Wien filter, and a Delta E-E telescope. The setup led to a measured suppression factor of 5 x 10(-18) for the C-12 ion beam. The experiments also indicate that an almost free choice of the charge state for the O-16 recoils is possible in the separator.

Original languageEnglish
Pages (from-to)471-477
Number of pages7
JournalEuropean Physical Journal A: Hadrons and Nuclei
Issue number4
Publication statusPublished - Dec 1999




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