Yin Yong-Zhi

Guiding of 150 keV O6+ ions through nanocapillaries in an uncoated Al2O3 membrane: special time dependence of the transmission profile width

This paper reports that the transmission of O6+ ions with energy of 150keV through capillaries in an uncoated Al2O3 membrane was measured, and agreements with previously reported results in general angular distribution of the transmitted ions and the transmission fractions as a function of the tilt angle well fitted to Gaussian-like functions were observed. Due to using an uncoated capillary membrane, our c is larger than that using a gold-coated one with a smaller value of E-p/q, which suggests a larger equilibrium charge Q(infinity) in our experiment. The observed special width variation with time and a larger width than that using a smaller E-p/q were qualitatively explained by using mean-field classical transport theory based on a classical-trajectory Monte Carlo simulation.

A comparative study of neutron stimulated emission computed tomography based on D-D/D-T neutron source

In this paper, we investigated the applications of D-D and D-T neutron sources in Neutron Stimulated Emission Computed Tomography (NSECT). Four NSECT models were established, including the TiT/TiD targets to generate neutron sources and the presence/absence of iron balls in water phantom to mimic tumors. NSECT system was simulated by using MCNP software, in which the D-D and D-T neutron sources were generated, collimated, transported, and recorded. We studied flux distributions and typical spectrum of both outgoing neutrons and the characteristic gamma-rays for D-D and D-T NSECT. Results show that the optimized NSECT gamma-ray detector locations will be in the direction from 43.6° to 50.9° along the neutron beam propagation direction. The best NSECT gamma-ray detector locations for D-D and D-T NSECT are slightly different, but in both cases the detectors should be aligned in the direction from 43.6° to 50.9°. We found the characteristic peaks of 56Fe and 16O from the energy spectrum of characteristic gamma-ray. This demonstrates that NSECT has the ability to identify elements, which would be very useful in tracking the treatment process and in studying the molecular process of living body (including human-beings). This study gives a comprehensive understanding on the selection of neutron sources and the placement of gamma-ray detectors in NSECT applications.

MCNP simulation study of neutron stimulated emission computed tomography system based on D-T neutron source

In this paper, Neutron Stimulated Emission Computed Tomography (NSECT) system was simulated using MCNP software, including the selection of Neutron source, the design of collimating shielding system, the setting of shielding wall and target body, and the arrangement of detector. The 14 MeV D-T Neutron source created by the Neutron generator located at Lanzhou University, was delivered, collimated and hit a cylindrical water phantom. We recorded and won the flux distribution and typical spectrum of characteristic gamma-ray and outgoing Neutron. This study has a guiding role for the detector layout during NSECT imaging experiment. From the flux distribution and typical spectrum of characteristic gamma-ray and outgoing Neutron, it is clearly shown that the position of NSECT imaging detector should be placed from 43.6° to 50.9° along the Neutron beam propagation direction. The optimized direction would be in 48.5°. From the characteristic gamma-ray spectrum, we found the characteristic peaks of 16O. This result suggests that NSECT has the ability to identify elements and to determine the element concentrations. This work also proved that NSECT could be applied for the early diagnosis of cancer and the checking of hiding explosives and drugs.

Interaction of 18-keV O{sup -} ions with Al{sub 2}O{sub 3} nanocapillaries

The transmission of 18-keV O- ions through Al2O3 nanocapillaries with 50 nm in diameter and 12 mu m in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV O-) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (O-, O-0, and O+) decreased when the tilt angle increased. In transmitted particles, the fraction of O- declined but that of O-0 and O+ ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.The transmission of 18-keV O{sup -} ions through Al{sub 2}O{sub 3} nanocapillaries with 50 nm in diameter and 12 {mu}m in length is studied in this work. By measuring angular distribution of transmitted particles when capillaries were tilted with respect to incident ion beam, two peaks were observed. It is distinguished that one of them is composed by direct transmitted ions and another one is composed by scattered ions. A phenomenon referred to as guiding effect, as found for highly charged ions and low-energy electrons, was observed. When negative ions (18-keV O{sup -}) are transmitted through nanocapillaries, most of them were ionized to neutral atoms and even positive ions. The intensity of transmitted particles (O{sup -}, O{sup 0}, and O{sup +}) decreased when the tilt angle increased. In transmitted particles, the fraction of O{sup -} declined but that of O{sup 0} and O{sup +} ions grew when the tilt angle grew. Both elastic collision and electrostatic scattering were found in scattered ions.

Guiding of 60 keV O6+ Ions through Nanocapillaries in an Uncoated Al2O3 Membrane

We measure the transmission of O6+ ions with a higher energy of 60keV (in turn a higher value of Ep/q) through capillaries in an uncoated Al2O3 membrane, and obtain agreements with previously reported results in general angular distribution of the transmitted ions and the transmission profile width variation with capillary tilt angle. The transmission fractions as a function of the tilt angle can be fitted to the semi-empirical Gaussian-like function well. Due to using uncoated capillary membrane, our Ψc is larger than that using gold-coated one, in spite of our larger value of Ep/q, which suggests a larger equilibrium charge Q∞ in our experiment.

Single-and-double electron loss of O2+ in collisions with argon and helium

This paper reports that the ratios of double to single electron loss cross-section (R) of O2+ in collision with Ar and He at the velocity of 1–4ν0 (ν0 is the Bohr velocity) have been obtained by the coincidence technique. The trend of R – V in the experiment indicates that the effective charge varies with injected velocity. The effective charge can be obtained by the n-body classical trajectory Monte Carlo method, which is interpreted by the molecular Coulomb over barrier model.