Knockout and fragmentation reactions using a broad range of tin isotopes

Production cross sections of residual nuclei obtained by knockout and fragmentation reactions of different tin isotopes accelerated at $1A$ GeV have been measured with the fragment separator (FRS) at GSI, Darmstadt. The new measurements are used to investigate the neutron-excess dependence of the neutron- and proton-knockout cross sections. These cross sections are compared to Glauber model calculations coupled to a nuclear de-excitation code in order to investigate the role of the remnant excitations. This bench marking shows an overestimation of the cross sections for the removal of deeply bound nucleons. A phenomenological increase in the excitation energy induced in the remnants produced in these cases allows us to reproduce the measured cross sections.

Figure 1

Schematic view of the FRS experimental setups used in the present work. (a) Setup with the reaction target at the entrance of the spectrometer to investigate knockout reactions of stable tin isotopes (${}^{112}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}$). (b) Setup with a fragmentation target at the entrance of the FRS to produce secondary beams of ${}^{110}\mathrm{Sn}$ and ${}^{120}\mathrm{Sn}$ that then impinged on a second carbon target located at the intermediate focal plane F2 in order to induce knockout reactions.

Figure 2

Identification matrix at the final focal plane (F4) of the FRS obtained in reactions induced by ${}^{112}\mathrm{Sn}$ impinging on the carbon target. The figure was obtained by overlapping several magnetic settings of the FRS.

Figure 3

Neutron-removal (upper panel) and proton-removal (lower panel) cross sections measured for different tin isotopes covering a large range in neutron excess: Perez-Loureiro et al. (open squares) [37], Audirac et al. (open triangles and solid stars) [22], Cerizza et al. (open cross) [44], and this work (solid dots). The data uncertainties are shown if they exceed the size of the symbols. This set of data is compared with Glauber model calculations (lines).

Figure 4

Energy cost for the emission of neutrons (binding energy, solid line) and protons (binding and Coulomb energy, dashed line) of the remnants produced in the proton-knockout reactions studied in this work as a function of the tin projectile mass number. Similar results are obtained for the neutron-knockout remnants.

Figure 5

Cross sections of the proton-removal channels produced in the fragmentation of different tin isotopes measured by Perez-Loureiro et al. (open squares) [37], Audirac et al. (open circles and triangles) [22], and this work (solid symbols). The data uncertainties are shown if they exceed the size of the symbols.

Figure 6

Measured isotopic production cross sections of fragment residues produced in the reaction ${}^{112}\mathrm{Sn}$ ($1A$ GeV) + ${}^{12}\mathrm{C}$ (points) compared with different calculations (lines). The data uncertainties are shown if they exceed the size of the symbols.