S.W. Tang

7Be, 8B+208Pb Elastic Scattering at Above-Barrier Energies

Angular distributions for the elastic scattering of 7Be and 8B by an enriched 208Pb target were measured at the Radioactive Ion Beam Line at Lanzhou (RIBLL). The incident energies of the radioactive beams were about three times the respective Coulomb barriers. A suppressed Coulomb-nuclear Interference Peak (CNIP) is not observed for 8B, a pronounced proton halo nucleus. Optical model fits were performed using Woods-Saxon potentials and the total reaction cross sections deduced. The results are discussed.

Mass Measurements of Proton‐rich Nuclides at the Cooler Storage Ring at IMP

Recent results and progress of mass measurements of proton‐rich nuclei using isochronous mass spectrometry (IMS) are reported. The nuclei under investigation were produced via fragmentation of relativistic energy heavy ions of 78Kr and 58Ni. After in‐flight separation by the fragment separator RIBLL‐2, the nuclei were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of the revolution times. The impact of these measurements on the stellar nucleosynthesis in the rp‐process is discussed.

A large area plastic scintillation detector with 4-corner-readout

A 760 mm × 760 mm × 30 mm plastic scintillation detector viewed by photomultiplier tubes(PMTs)from four corners has been developed, and the detector has been tested with cosmic rays and γ rays. A positionindependent effective time Teff has been found, indicating this detector can be used as a TOF detector. The hit position can also be reconstructed by the time from the four corners. A TOF resolution of 236 ps and a position resolution of 48 mm have been achieved, and the detection efficiency has also been investigated.A 760 mm × 760 mm × 30 mm plastic scintillation detector viewed by photomultiplier tubes(PMTs)from four corners has been developed, and the detector has been tested with cosmic rays and γ rays. A positionindependent effective time Teff has been found, indicating this detector can be used as a TOF detector. The hit position can also be reconstructed by the time from the four corners. A TOF resolution of 236 ps and a position resolution of 48 mm have been achieved, and the detection efficiency has also been investigated.

Direct Mass Measurements of Short-Lived A=2Z-1 Nuclides {sup 63}Ge, {sup 65}As, {sup 67}Se, and {sup 71}Kr and Their Impact on Nucleosynthesis in the rp Process

Mass excesses of short-lived A=2Z-1 nuclei (63)Ge, (65)As, (67)Se, and (71)Kr have been directly measured to be -46,921(37), -46,937(85), -46,580(67), and -46,320(141)  keV, respectively. The deduced proton separation energy of -90(85)  keV for (65)As shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of (65)As suggest that the majority of the reaction flow passes through (64)Ge via proton capture, indicating that (64)Ge is not a significant rp-process waiting point.