NUCLEAR ASTROPHYSICS STUDIES BY RECOIL MASS SEPARATORS

It has been recently demonstrated that an accelerator mass spectrometr y (AMS) system, used as a recoil separator in conjunction with a windo wless gas target, can yield the high suppression factor needed to disp ersively analyze radiative capture residues, with the aim of measuring cross sections in the sub-microbarn range. An experiment is underway utilizing a radioactive Be-7 beam for the measurement of the cross sec tion of the astrophysically important reaction Be-7(p, gamma)B-8 at a center of mass energy E-CM = 1 MeV. Preliminary results of this experi ment are presented. The extension of the method to another reaction pl aying a key role in stellar evolution, i.e. C-12(alpha, gamma)O-16, re quires an improvement of the angle-and momentum-acceptance of the reco il separator, the use of a jet gas target and of a specially designed low-threshold detector. The solutions proposed by a joint italian-germ an project are discussed.