Yan-Yun Yang

Monte Carlo simulations of the performance of a Compton camera consisting of position-sensitive germanium detectors

A high energy resolution Compton camera consisting of position-sensitive germanium detectors is proposed for multitracer imaging. The distributions of the number of gamma-ray interaction points in both detectors are calculated by the Monte Carlo simulations. The effects of multiple scattering on the performance of the Compton camera are discussed. A gamma-ray tracking algorithm is used to determine the first interaction point in the second detector. The efficiency and spatial resolution of a Compton camera for gamma rays of different energies, emitted from different positions are also simulated.

Influence of breakup on elastic and α-production channels in the 6Li+ 116Sn reaction*

The effects of breakup reactions on elastic and α-production channels for the 6Li+116Sn system have been investigated at energies below and near the Coulomb barrier. The angular distributions of α-particle production differential cross sections have been obtained at several projectile energies between 22 and 40 MeV. The measured breakup α-particle differential cross sections and elastic scattering angular distributions have been compared with the predictions of continuum-discretized coupled channels (CDCC) calculations. The influence of breakup coupling has also been investigated by extracting dynamic polarization potentials (DPP) from the CDCC calculations. From the predictions of CDCC calculations the relative importance of the nuclear, Coulomb, and total breakup contributions have also been investigated. The nuclear breakup couplings are observed to play an important role in comparison to the Coulomb breakup for the direct breakup mechanisms associated in the reaction of 6Li projectile with 116Sn target nuclei. The influence of strong nuclear breakup coupling exhibits suppression in the Coulomb-nuclear interference peak. The direct breakup cross sections from the CDCC calculations under-predict the measured α-particle differential cross sections at all energies. This suggests that the measured α particles may also have contributions from other possible breakup reaction channels.

Investigation of the near-threshold cluster resonance in 14 C

An experiment for m p(14C},14C*→10Be+α)p inelastic excitation and decay was performed in inverse kinematics at a beam energy of 25.3 MeV/u. A series of 14C excited states, including a new one at 18.3(1) MeV, were observed which decay to various states of the final nucleus of 10Be. A specially designed telescope system, installed around zero degrees, played an essential role in detecting the resonant states near the α-separation threshold. A state at 14.1(1) MeV is clearly identified, being consistent with the predicted band-head of the molecular rotational band characterized by the π-bond linear chain configuration. Further clarification of the properties of this exotic state is suggested by using appropriate reaction tools.

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.

Correlation between quarter-point angle and nuclear radius

The correlation between quarter-point angle of elastic scattering and nuclear matter radius is studied systematically. Various phenomenological formulae with parameters for nuclear radius are adopted and compared by fitting the experimental data of quarter point angle extracted from nuclear elastic scattering reaction systems. A parameterized formula related to binding energy is recommended, which gives a good reproduction of nuclear matter radii of halo nuclei. It indicates that the quarter-point angle of elastic scattering is quite sensitive to the nuclear matter radius and can be used to extract the nuclear matter radius.

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.