Song Yu-Shou

Knockout reaction induced by 6He at 61.2 MeV/u

A knockout reaction induced by 6He at 61.2 MeV/u was carried out at the HIRFL-RIBLL radioactive beam line. The α core fragments at forward angles were detected in coincidence with the recoiled protons at large angles. From this coincident measurement the valence nucleon knockout mechanism and the core knockout mechanism can be separated according to the polar angle correlation between the core fragments and the recoiled protons. It is demonstrated that, when reconstructing the resonant state of a weakly bound nucleus, the contamination resulting from the core knockout mechanism should be eliminated in order to obtain the correct structure information.

Quasi-Elastic Scattering of 16C from 12C at 47.5 MeV/Nucleon

Differential cross sections for the quasi-elastic scattering of C-16 at 47.5 MeV/nucleon from C-12 target are measured. Coupled-channels calculations are carried out and the optical potential parameters are obtained by fitting the experimental angular distribution.

New test and analysis of position-sensitive-silicon-detector

We have tested and analyzed the properties of two-dimensional Position-Sensitive-silicon-Detector (PSD) with new integrated preamplifiers. The test demonstrates that the best position resolution for 5.5 MeV α particles is 1.7 mm (FWHM), and the best energy resolution is 2.1%, which are notably better than the previously reported results. A scaling formula is introduced to make the absolute position calibration.

Monte Carlo simulation of the property of a scintillation bar in the multi-neutron correlation spectrometer

To perform a kinematically complete measurement of the dissociation reaction for neutron-rich nuclei, a multi-neutron correlation spectrometer is proposed at Peking University. A Monte Carlo simulation code based on GEANT4 is developed for a single scintillation bar which processes not only the energy deposition but also the light propagation in the scintillator and the light collection and conversion to signal at the end of the bar in a realistic way. The simulating method is described in detail in this paper, and the timing and position resolutions and detector efficiency are studied based on the simulation and compared with the experimental results. A new method of crosstalk rejection has been demonstrated to be important for the design of the whole spectrometer.

Study of the structure of borromean nucleus17Ne

The 17Ne nucleus is a possible candidate with a two-proton borromean halo structure. Since the theoretical model is difficult to handle the three-body system, it is difficult to determine the two-proton halo structure in 17Ne. In the present research, we try to study the breakup reaction of 17Ne. For the Borromean nuclei, one-proton knockout results in an unstable nucleus which is decaying further by proton emission. This process will result in an angular correlation between the direction of the aligned recoiling unstable nucleus and its decay products. The angular correlations can give us information about the configuration of the valence proton in the 17Ne. Furthermore, theoretical calculations indicate that the momentum distributions of 16F c.m are sensitive to the structure of the halo in 17Ne. Thus the measurement of momentum distributions of 16F c.m may also give us conclusive information on the structure of 17Ne. The present experiment has been done at IMP in Lanzhou using the radioactive beam 17Ne at 30.8 MeV/u on a 43mg/cm2 12C target. The data analysis is under procedure and the primary results are provided.

Study of the Structure of Borromean Nucleus 17Ne

In the present research, we used the 17Ne beam at 30.8 MeV/u to bombard the 43 mg/cm2 12C target and measured the angular correlations between the fragments and emitted proton. In the break-up reaction of 17Ne, one-proton knockout would result in an unstable nucleus 16F, which would further decay by the proton emission. The measured angular correlation between the 16F momentum and the relative momentum of its decay products was compared with theoretical calculations and indicated that the valence proton in 17Ne has the most probability to be situated in the s1/2 orbital with a small admixture of the d5/2 orbital. The present results suggest that 17Ne has a halo structure.