Zhan Wen-Long

Separation and Identification of Isotopes Produced from 20Ne+Be Reaction by Radioactive Ion Beam Line in Lanzhou

The separation and identification of isotopes emitted from the projectile fragmentation reaction of 80 MeV/u 20Ne on 9Be target were carried out by using the radioactive ion beam line in Lanzhou (RIBLL). Many proton rich isotopes are obtained. Their intensity and purity fit the theoretical calculations. Good separation and identification abilities of RIBLL A/ΔA > 300 and Q/ΔQ > 150, are obtained.

A pilot experiment for mass measurement at CSRe

A pilot experiment of mass measurement was performed at CSRe with the method of isochronous mass spectrometry. The secondary fragments produced via RIBLL2 with the primary beam of 400 MeV/u, Ar-36 delivered by CSRm were injected into CSRe. The revolution periods of the stored ions, which depend on the mass-to-charge ratios of the stored ions, were measured with a time-of-flight detector system. The results show that the mass resolution around 8 x 10(-6) for Delta m/m is achieved.

Property measurement of the CsI(Tl) crystal prepared at IMP

Large-sized CsI(Tl) single crystals, ~ 100 mm × 350 mm, have been grown successfully, and this CsI(Tl) coupled with PD has been successfully utilized at RIBLL (the Radioactive Ion Beam Line in Lanzhou) to measure the energy of heavy ions as a stopping detector. The performances of CsI(Tl) detector coupled with PD and APD have been tested and compared, including the temperature dependence of scintillating light yield.

Studies of a scintillator-bar detector for a neutron wall at an external target facility

To achieve a better time resolution of a scintillator-bar detector for a neutron wall at the external target facility of HIRFL-CSR, we have carried out a detailed study of the photomultiplier, the wrapping material and the coupling media. The timing properties of a scintillator-bar detector have been studied in detail with cosmic rays using a high and low level signal coincidence. A time resolution of 80 ps has been achieved in the center of the scintillator-bar detector.

Possible Experimental Evidence of a Moderate Proton Halo in29S

The total reaction cross sections (TRCSs) of 29S+28Si have been measured at intermediate energies. An obvious enhancement in TRCS of 29S is observed as compared with its neighbouring nuclei. The TRCSs of 29S+28Si are calculated with the modified Glauber theory in the optical limit and few-body approaches. The different factor d as a possible measure of halo appearance is deduced from the experimental and theoretical data. It is well accepted that 27P is a proton halo nucleus. Although not as anomalous as 27P, the different factor d of 29S is obviously larger than that of its neighbouring isotones of N = 13. This result indicates that a moderate proton halo may exist in 29S nucleus. We calculate the total reaction cross sections for 29S with the modified Glauber theory as a function of incident energy and compare the results with those for 27Si which is a core nucleus of 29S. The measured TRCSs of 27Si+28Si can be described to be satisfactory by the modified Glauber theory of the optical limit approach. Although a diffused nuclear density distribution is used, the theories still inadequately predict the experimental TRCSs of 29S+28Si, which further indicates the possibility of proton halo in 29S.

Surface Plasmon-Assisted Excitation of Atomic Visible Light Spectral Lines in the Impact of Highly Charged Ions 126Xeq + on Solid Surfaces

We measured the visible light spectral lines of sputtering atoms from solid surfaces of Al, Ti, Ni, Ta and Au which are impacted by 150 keV 126Xeq + (6≤q≤30). It is found that intensities of the light spectral lines are greatly and suddenly enhanced when the charge state of the ion is raised up to a critical value. If assuming that potential energy released from the incident ion due to capturing one electron is enough to excite a surface plasmon, we can estimate the critical charge states and obtain the results very well consistent with the measurements for the above-mentioned target materials. This means that a surface plasmon induced by one electron capture can enhance the excitation of atomic visible light spectral lines in the impact of a highly charged ion on a solid surface.

Measurements of Total Reaction Cross Sections for Exotic Nuclei Close to the Proton Drip-line at Intermediate Energies and Observation of a Proton Halo in 27P

Measurements of the total reaction cross sections (sigma (R)) for some proton-rich nuclei (N = 11 - 15 isotones) on a carbon target at intermediate energies have been performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. A larger enhancement of sigma (R) for P-27 has been observed than for its neighbours. Evidence for a proton halo in P-27 has been revealed in the Glauber analysis of the total reaction cross sections in terms of the difference factor d.

Measurements of total reaction cross section for light nuclei and evidence for the anomalous nuclear structure in C-15

Measurements of the total reaction cross section for C12-16, N14-17 and O16-18 on carbon target at intermediate energies were performed on RIBLL of HIRFL. A larger enhancement of sigma(n) for C-15 was observed than that for its neighbors. The analysis of these data indicates possible existence of an anomalous nuclear structure in C-15. A new quantity was suggested as the criterion to distinguish anomalous structure nuclei from normal nuclei.

Design of the IMP microbeam irradiation system for 100 MeV/u heavy ions

A state-of-the-art high energy heavy ion microbeam irradiation system is constructed at the Institute of Modern Physics of the Chinese Academy of Sciences. This microbeam system operates in both full current intensity mode and single ion mode. It delivers a predefined number of ions to pre-selected targets for research in biology and material science. The characteristic of this microbeam system is high energy and vertical irradiation. A quadrupole focusing system, in combination with a series of slits, has been designed to optimize the spatial resolution. A symmetrically achromatic system leads the beam downwards and serves simultaneously as an energy analyzer. A high gradient quadrupole triplet finally focuses a C6+ ion beam to 1 μm in the vacuum chamber within the energy range from 10 MeV/u to 100 MeV/u. In this paper, the IMP microbeam system is described in detail. A systematic investigation of the ion beam optics of this microbeam system is presented together with the associated aberrations. Comparison is made between the IMP microbeam system and the other existing systems to further discuss the performance of this microbeam. Then the optimized initial beam parameters are given for high resolution and high hitting efficiency. At last, the experiment platform is briefly introduced.

The β Decay of 21N

The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus 21N were measured by using the β–γ and β – n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98MeV and with a total branching ratio of 88.7 ± 4.2% were observed and presented. One γ transition with an energy of 1222keV emitted from the excited state of 21O, and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of 20O were identified in the β decay chain of 21N. The β decay half-life for 21N is determined to be 82.9 ± 1.9 ms. The uncertainty of half-life is much smaller than the previous result.