Engineering topics

Wang, J S

Publications and source records attributed to Wang, J S.

8 records

DOE OSTI2012

Structural phase transitions of SrF{sub 2} at high pressure

The high-pressure behavior of SrF{sub 2} has been investigated by angle-dispersive synchrotron X-ray powder diffraction measurement up to 50.3 GPa at room temperature. Two phase transformations were observed at 6.8 and 29.5 GPa, and the two high pressure phases were identified as orthorhombic (Pnma) phase and hexagonal (P6{sub 3}/mmc) phase by Rietveld refinement. Upon decompression, retransformation was observed and the sample recovered under ambient conditions consisted of a mixture of cubic phase and orthorhombic phase. The compressing characteristics of SrF{sub 2} as the pressure increases were discussed, indicating higher incompressibility of SrF{sub 2} under high pressure. - Graphical abstract: The high-pressure behavior of SrF{sub 2} has been investigated by angle-dispersive synchrotron X-ray powder diffraction measurement up to 50.3 GPa at room temperature. Highlights: Black-Right-Pointing-Pointer The high-pressure study on SrF{sub 2} up to 50.3 GPa at room temperature. Black-Right-Pointing-Pointer Two first-order phase transformations were observed at 6.8 and 29.5 GPa. Black-Right-Pointing-Pointer The three stable structures are confirmed by Rietveld refinements. Black-Right-Pointing-Pointer The cubic and orthorhombic phase co-exist at pressures down to ambient pressure. Black-Right-Pointing-Pointer The bulk modulus indicates higher incompressibility of SrF{sub 2} under high pressure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2011

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 {sup 78}Kr and {sup 58}Ni. 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.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

Recent experimental results of two-proton correlated emission from the excited states of {sup 17,18}Ne and {sup 28,29}S

Two-proton emissions from the excited states of {sup 17,18}Ne and {sup 28,29}S were investigated by the radioactive beams bombarding on the {sup 197}Au 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 were reconstructed under the framework of relativistic kinematics. The mechanisms of two-proton emission were analyzed in a simple schematic model. With the help of Monte-Carlo simulations, the two protons emitted from the 6.15 MeV excited state of {sup 18}Ne and the excited states around 10 MeV of {sup 29}S, respectively, exhibit prominent features of {sup 2}He decay. While for the other states, no obvious diproton emissions were observed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm{sup 2} has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 deg. C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

36 MATERIALS SCIENCE↗

DOE OSTI2010

Observation of two-{alpha} emission from high-lying excited states of {sup 18}Ne by complete-kinematics measurements

Two-{alpha} emission from high-lying excited states of {sup 18}Ne was studied by complete-kinematics measurements. The {sup 18}Ne beam at the energy of 51.8 MeV/u was bombarding a {sup 197}Au target to populate the excited states via Coulomb excitation. Products of two-{alpha} emission, {sup 10}C-{alpha}-{alpha}, were measured by an array of silicon strip detectors and a CsI + PIN telescope. With the help of Monte Carlo simulations, the experimental results show the characteristics of sequential two-{alpha} emission via {sup 14}O excited states. Sequential two-{alpha} and two-proton emissions from {sup 18}Ne via one-particle daughter states are compared and the distinction of the opening angles of these two modes originates from the difference of the mass ratio of emitted particles to daughter nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2010

Investigation of two-proton emission from excited states of the odd-Z nucleus {sup 28}P by complete-kinematics measurements

An experiment to study exotic two-proton emission from excited levels of the odd-Z nucleus {sup 28}P was performed at the National Laboratory of Heavy Ion Research-Radioactive Ion Beam Line (HIRFL-RIBLL) facility. The projectile {sup 28}P at the energy of 46.5 MeV/u was bombarding a {sup 197}Au target to populate the excited states via Coulomb excitation. Complete-kinematics measurements were realized by the array of silicon strip detectors and the CsI+PIN telescope. Two-proton events were selected and the relativistic-kinematics reconstruction was carried out. The spectrum of relative momentum and opening angle between two protons was deduced from Monte Carlo simulations. Experimental results show that two-proton emission from {sup 28}P excited states less than 17.0 MeV is mainly two-body sequential emission or three-body simultaneous decay in phase space. The present simulations cannot distinguish these two decay modes. No obvious diproton emission was found.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2010

Nuclear physics program at HIRFL

With the commissioning of HIRFL-CSR, HIRFL can provide heavy ion beams with energy covering the range of several MeV/u to 1 GeV/u. In this talk, the experiments on nuclear physics at different energies to be carried out with different experimental setups at HIRFL will be introduced.

43 PARTICLE ACCELERATORS↗

DOE OSTI2010

Measurement on proton-proton correlation of the excited {sup 23}Al

We have measured two-proton momentum and angular correlations for the {sup 23}Al excited states from the {sup 23}Al radioactive beam on a {sup 12}C target at an energy of 60approx70 A MeV at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The decay products, namely {sup 21}Na+p+p from {sup 23}Al are clean identified. The relative momentum and opening angle between two protons in the rest frame of three body decay channels demonstrate that there are some diproton emission components from {sup 2}He cluster for the excited {sup 23}Al.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗