The excitation function of quasi-elastic （QEL） scattering at a backward angle has been measured for 9^Be＋208^Pb. The barrier distribution was extracted by means of the first derivative of the measured excitation function and calculated with the coupled-channel model. The present work shows that the experimental barrier distribution extracted from QEL scattering is shifted to the low energy side by 1.5 MeV as compared with the theoretical one. This energy discrepancy indicates that breakup is important in the colliding processes of the weakly bound nucleus system.
The angular distribution of 1 H（ 6 He,p） 6 He elastic scattering has been measured at E c.m. = 4.3 MeV by using a thick-target inverse kinematic method. The experimental differential cross sections are reproduced by the distorted-wave Born approximation calculation utilizing the CH89 global optical potential parameter set. The real part of CH89 is reduced comparing with other potentials, which may be attributed to the couplings necessary for the weakly bound nuclei.
The ^13 N＋p elastic resonance scattering has been studied at the secondary radioactive beam facility of CIAE in inverse kinematics via a thick-target method. The excitation function for the ^13N（p,p） scattering was obtained in the energy interval of Ecru ≈0.5-3.2 MeV with a ^13 N secondary beam of （47.8±1.5） MeV. Careful analysis of the secondary beam components and extensive Monte-Carlo simulations enable the resolution of the experimental proton spectra. The resonance parameters for five low-lying levels in ^14 O were deduced by Rmatrix fitting calculations with MULTI7 and SAMMY-M6-BETA. The present results show general agreement with those from a recent similar work, and thus confirm the observation of a new 0^- level at 5.7 MeV in 140 with an improved width of 400（45） keV.
The quadrant silicon detector, a kind of passivated implanted planar silicon detector with quadrant structure on the junction side, gained its wide application in charged particle detection. In this paper, the manufacturing procedure, performance test and results of the quadrant silicon detector developed recently at the China Institute of Atomic Energy are presented. The detector is about 300 μm thick with a 48 mm×48 mm active area.The leakage current under the full depletion bias voltage of-16 V is about 2.5 n A, and the rise time is better than160 ns. The energy resolution for a 5.157 Me V α-particle is around the level of 1%. Charge sharing effects between the neighboring quads, leading to complicated correlations between two quads, were observed when α particles illuminated on the junction side. It is explained as a result of distortion of the electric field of the inter-quad region.Such an event is only about 0.6% of all events and can be neglected in an actual application.
The elastic resonance scattering of ^12C＋p has been studied in inverse kinematics via a novel thicktarget method at GIRAFFE facility of HI-13 tandem accelerator laboratory, Beijing. The recoil protons weremeasured by a AE-E counter telescope based on a large area double-sided silicon strip detector at laboratoryangles around θ0 = 15^o. The excitation function for ^12C（p,p） elastic scattering has been obtained over a wideenergy range of Ec.m. =0.31-3.45 MeV, which was explained quite well by the R-matrix calculation with known resonance parameters of the first three levels in ^13N nucleus. Thus it is demonstrated that the present setup can be directly applied to the study of elastic resonance scattering with secondary radioactive beams.
Lithium isotopes have attracted an intense interest because the abundance of both 6Li and 6Li from big bang nucleosynthesis (BBN) is one of the puzzles in nuclear astrophysics. Many investigations of both astrophysical observation and nucleosynthesis calculation have been carried out to solve the puzzle, but it is not solved yet. Several nuclear reactions involving lithium have been indirectly measured at China Institute of Atomic Energy, Beijing. The Standard BBN (SBBN) network calculations are then performed to investigate the primordial Lithium abundance. The result shows that these nuclear reactions have minimal effect on the SBBN abundances of 6Li and 7Li.
LI ZhiHong1, LI ErTao1, SU Jun1, LI YunJu1, BAI XiXiang1, GUO Bing1, WANG YouBao1, CHEN YongShou1, HOU SuQing1, ZENG Sheng1, LIAN Gang1, SHI JianRong2 & LIU WeiPing1 1 China Institute of Atomic Energy, Beijing 102413, China
Two-proton emissions from the excited states of 17,18Ne, 28P and 28,29S were investigated experimentally by the radioactive beams bombarding on the 197Au target via the Coulomb excitation. The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors. The invariant mass of final systems as well as the relative momentum, opening angle, and relative energy of the two emitted protons was reconstructed under the framework of relativ istic kinematics. Visible proton-proton correlations were observed in these systems. The mechanisms of two-proton emission were analyzed in a simple schematic model, in which the extreme decay modes like He cluster emission, three-body 2 phase-space decay, and two-body sequential decay were taken into account. With the help of Monte-Carlo simulations, the two protons emitted from the 6.15 MeV excited state of Ne and the excited states in the energy region of 9.6–10.4 MeV of S, 18 29 respectively, exhibited prominent features of2 He cluster decay while for the other cases, no obvious diproton emissions were observed.
LIN ChengJian1, XU XinXing1, JIA HuiMing1, YANG Feng1, JIA Fei1, WU ZhenDong1, ZHANG ShiTao1, LIU ZuHua1, ZHANG HuanQiao1, XU HuShan2, SUN ZhiYu2, WANG JianSong2, HU ZhengGuo2, WANG Meng2, CHEN RuoFu2, ZHANG XueYing2, LI Chen2, LEI XiangGuo2, XU ZhiGuo2, XIAO GuoQing2 & ZHAN WenLong2 1China Institute of Atomic Energy, P. O. Box 275(10), Beijing 102413, China
