Isotopic production cross sections of residual nuclei in the spallation reaction ${}^{136}\mathrm{Xe}\left(200A\text{MeV}\right)+p$

The residual nuclei produced in the spallation reaction of ${}^{136}\mathrm{Xe}$ nuclei at $200A$ MeV on protons have been studied by measuring the isotopic distributions for the elements from cadmium ($Z=48$) to cesium ($Z=55$) by using the fragment separator (FRS) spectrometer at GSI and the inverse kinematics technique. This is one of the few measurements performed at such a low projectile energy, close to the validity limit for intranuclear cascade models such as incl or isabel. The experimental results have been compared to these intranuclear cascade codes coupled to the evaporation code abla. Both code combinations reproduce qualitatively the measured isotopic distributions; however, both underestimate the production of residues with mass numbers between 126 and 134. The measured cross sections are of interest for the planning of future radioactive beam or neutron source facilities.

Figure 1

Schematic drawing of the fragment separator with the detector equipment.

Figure 2

Energy loss for the fragments transmitted in the FRS in the magnetic setting centered on ${}^{131}\mathrm{I}$ obtained with one MUSIC detector (black line) and combining the signals from the three MUSICs (red line).

Figure 3

Charge distribution of the reaction residues including all the measured FRS settings.

Figure 4

Plot showing the improvement achieved in nuclear mass identification by using the second stage of the FRS (a) and the first stage (b). Data correspond to the iodine residues measured with the FRS magnetic setting centered on ${}^{125}\mathrm{I}$.

Figure 5

Cluster plot showing the correlation between the atomic number ($Z$) and the mass-over-charge ratio ($A/Z,Z$) obtained from the 13 different FRS magnetic settings used in the experiment. It provides an unambiguous identification in atomic and mass number for the residues of the reaction ${}^{136}\mathrm{Xe}+p$ at $200A$ MeV.

Figure 6

Identification plot showing the particular shape of the beam spot, in which part of the beam particles are identified as $Z=55$ because of the lower velocity through the MUSICs.

Figure 7

Plot showing the correlation between the mass identification obtained in the two FRS sections. It allows the rejection of the background due to secondary reactions before the MUSICs (beyond the solid lines).

Figure 8

Charge state probabilities predicted by the global code for fragments produced in the reaction Xe+$p$ at $200A$ MeV when traversing each FRS stage. The solid (black) curve refers to the probability of having fully stripped fragments in both stages ($q_1=q_2=Z$); dashed (blue) curve: $q_1=Z,q_2=Z-1$; dashed-dotted (red) curve: $q_1=Z-1,q_2=Z$; and dotted (green) curve: $q_1=q_2=Z-1$.

Figure 9

The figure shows the background due to secondary reactions in S4 before the MUSICs for the FRS setting centered on ${}^{131}\mathrm{I}$. Solid lines show the selection applied to reject the fragments that interact just before reaching the MUSICs.

Figure 10

Reconstruction of momentum distribution of the ${}^{125}\mathrm{Xe}$ fragments using three different FRS magnet settings.

Figure 11

Isobaric production yields obtained with the liquid-hydrogen target in the titanium container (open circles) and with the empty titanium container (solid circles).

Figure 12

Isotopic distributions of the production cross sections measured in this work compared to the predictions of the codes incl4.6 (solid lines) and isabel (dashed lines) coupled to the deexcitation code abla07. Solid circles represent measured data while empty circles are the extrapolated ones.

Figure 13

Isobaric cross section distribution obtained for the reaction ${}^{136}\mathrm{Xe}+p$ at $200A$ MeV, compared to the results provided by the simulation codes incl4.6 (solid line) and isabel (dashed line), both coupled to the deexcitation code abla07.

Figure 14

Isobaric distributions of the measured cross sections for the ${}^{136}\mathrm{Xe}+p$ reactions at $1000A$ MeV (solid triangles), $500A$ MeV (open squares), and $200A$ MeV (solid circles)

Figure 15

Isobaric cross sections of the residual nuclei produced in the reactions ${}^{136}\mathrm{Xe}+p$ at $1000A$ MeV (solid triangles) [18], $500A$ MeV (open squares) [19], and $200A$ MeV (solid circles).

Figure 16

Average neutron excess of the isotopic distributions of the production cross sections for the residual nuclei measured in the reactions ${}^{136}\mathrm{Xe}+p$ at $1000A$ MeV (triangles), $500A$ MeV (squares), and $200A$ MeV (solid circles) as a function of the atomic number of the residue. The data are compared with the predictions obtained with incl4.6 coupled to abla07.