Physics Letters B 707 (2012) 46–51
6He +n relative energy spectra
Experimental setup

In our experiment induced by intense 8He beam at 82.3 MeV/u, the recoil protons were measured in coincidence with the forward moving core fragments and neutrons. The 6He core fragment knockout mechanism is identified by the polar angle correlation and further checked by other kinematics conditions. This process can be used to extract the spectroscopic information of the cluster structure of unstable nuclei in their ground state. On the other hand the valence nucleon knockout mechanism may also be selected and applied to extract single-particle structure information. In the case of 7He ground state, a narrower peak was obtained with the proton tagging, resulting in a relatively smaller neutron SF of 0.512(18). This narrowing effect encourages more investigations of possible complex processes eventually being involved in knockout reactions, especially at incident energies below 100 MeV/u, and to identify certain tagging methods to discriminate these processes. It is also shown that CH2 target may be used in place of “pure” hydrogen target as long as the recoil proton tagging is applied and the core fragment knockout process is concerned. In order to further explore the recoil proton tagging technique, high efficiency proton detection system with large solid angle coverage should be implemented.