For scanning transmission proton microscopy tomography,to compare cell images of the proton stopping power and relative electron density,two cell phantoms are designed and simulated by code FLUKA.The cell images are reconstructed by the filtered back projection algorithm,and compared with their tomography imaging.The images of stopping power and relative electron density slightly vary with proton energies,but the internal images are of clear with high resolution.The organic glass image of relative electron density reveals the resolution power of proton tomography.Also,the simulation results reflect effects of the boundary enhancement,the weak artifacts,and the internal structure border extension by multiple scattering.So using proton tomography to analyze internal structure of a cell is a superior.
In this paper,the proton image quality of three designed phantoms is studied by the Monte Carlo simulation tool FLUKA,and is compared with that of the photon,and electron imaging.The passages of parallel beams were simulated by the phantoms for protons,electrons and X-rays,and the fluence and energy spectra of exiting particles are recorded.The proton energy loss imaging has a high quality under low transmission proton fluence,and its quality is superior to that of electron and photon fluence.The results demonstrate that proton energy loss imaging is especially suitable for the samples of hundreds of nano-thicknesses.
Behaviors and properties of helium in titanium were explored by molecular dynamics(MD) simulation in this study.The influence of He number,vacancy number and He density(ratio of helium to vacancy) on the thermal stability of HenVm clusters(where n and m denote the number of He atoms and vacancies) were investigated.Meanwhile,interactions among He atoms,SIA atoms and vacancies were discussed.The results demonstrate that the binding energies of an interstitial helium atom primarily depend on He and vacancy numbers rather than the helium-to-vacancy ratio(n/m).It is different from the previous report of other researchers.The binding energies of an isolated vacancy and a self-interstitial titanium atom depend on both the number of helium atoms and the helium-to-vacancy ratio(n/m) of clusters.The thermal stability of clusters is decided by the competitive processes among thermal emissions of vacancy,SIA and helium atom.
