Xin-Xing Xu

Direct Breakup Rections Of 8B At Fermi Energy

The longitudinal momentum distributions of the core-like fragment 7Be from the breakup of 8B on 12C target have measured at the energy of 36MeV/u at the Radioactive Ion Beam Line in Lanzhou (RIBLL). In order to distinguish the stripping and diffraction mechanisms involving in breakup reaction of 8B, both fragments of 7Be and proton are measured coincidently. With this coincident measurement, the widths of longitudinal momentum distribution are deduced with the values of 124±17MeV and 92±7 MeV for stripping and diffraction mechanism respectively. It is found that the longitudinal momentum width of stripping component is larger than that of diffraction component, which is different from the breakup reaction at high energy as around GeV/u. The theoretical calculations are compared with these experimental results.

Self-consistent analysis of sub-barrier fusion enhancement effect in Ca+Ca and Ni+Ni

The fusion dynamic mechanism of heavy-ions at energies near the Coulomb barrier is complicated and still not very clear up to now. Accordingly, a self-consistent method based on the CCFULL calculations has been developed and applied for an ingoing study of the effect of the positive Q-value neutron transfer (PQNT) channels in this work. The typical experimental fusion data of Ca + Ca and Ni + Ni is analyzed within the unified calculation scheme. The PQNT effect in near-barrier fusion is further confirmed based on the self-consistent analysis and extracted quantitatively.

A multilayer Δ E - E R telescope for breakup reactions at energies around the Coulomb barrier

The breakup reactions of weakly-bound nuclei at energies around the Coulomb barrier and the corresponding coupling effect on the other reaction channels are hot topics nowadays. To overcome the difficulty in identifying both heavier and lighter fragments simultaneously, a new kind of ionization-chamber based detector telescope has been designed and manufactured. It consists of a PCB ionization chamber and three different thickness silicon detectors installed inside the chamber, which form a multilayer ΔE-E R telescope. The working conditions were surveyed by using an α source. An in-beam test experiment shows that the detector has good particle identification for heavy particles like 17F and 16O as well as light particles like protons and alpha particles. The measured quasi-elastic scattering angular distribution and the related discussions for 17F+208Pb are presented.

Experimental Study of Two-alpha Emission from High-lying Excited States of 17,18 Ne

The experiments of two-alpha emission from Ne-17,Ne-18 excited levels were performed at the HIRFL-RIBLL facility of the Institute of Modern Physics, Lanzhou. The beams of Ne-17 at the energy of 49.9 MeV/u and Ne-18 at 51.8 MeV/u bombarded a Au-197 target to populate excited states of Ne-17,Ne-18 via Coulomb excitation. Complete kinematics measurements were achieved by the detectors of a silicon strip and CsI+PIN array. The experimental results combined with simple MC simulations show the characteristic of sequential two-alpha emission via O-14 excited states for Ne-18. The results of two-alpha emission from Ne-17 are preliminary and need further analyses.

Dressing modification in the laser-assisted proton-helium charge exchange collision

Abstract:A first Born approach to intense laser modified proton-helium electron capture collision is given. Theoretical results show that the angular distribution peaks forward sharply. For a geometry of laser polarization vector parallel to the incident direction, the dressing effect on the differential cross section covers a relatively wide angular range; while for a perpendicular geometry, the result is modified only in a very small angular region. The integral cross sections get highly promoted by laser with the impact energy increasing. The modified cross sections are increasing functions of field strength, but decreasing functions of field frequency. Comparisons with the laser assisted electron capture from atomic hydrogen are made.