The Transmission Of Low-to-intermediate Energy Ions Through Tapered Capillaries

The micro-beams of low-to-intermediate energy ions have wide applications.The physical mechanism of this kind of ions transmitted through the tapered capillaries is still ambiguous.In this thesis,the transmission properties of low-to-intermediate energy ions through tapered glass capillaries are studied.Based on autonomous programming and Monte-Carlo method,the time evolution processes of low-to-intermediate protons and low energy highly charged ions being transmitted through tapered capillaries are simulated.Three different processes are considered in the model.The first is the long-range Coulomb force from the surface charge deposited on the inner wall of the capillary.The second is the short-range collective scattering force from the topmost surface layer of atoms.The third is the binary encounter force between a projectile and target atoms below the inner surface of the capillary.In order to carefully analyze the transmission mechanism,the trajectories of each ions are marked.For the transmission of intermediate protons,the dynamic evolution of the trajectories,angular distributions and 2D images of transmitted protons is simulated and analyzed.The simulation results indicate that the charge deposited in the capillary significantly enhances the probability of surface specular scattering and thus greatly enhances the transmission rate.The results show that for 100 keV protons,a focusing effect is obtained with a density enhancement factor of 5⁶.Furthermore,this deposited-charge-assisted specular reflection causes the transmission rate to exhibit an energy dependence proportional to E_p^-1,which is well consistent with the experimental data.Such a dynamic evolution analysis helps to provide clear images for intermediate energy ions transmitted in tapered glass capillaries.Moreover,the transmission properties for protons through different capillaries are compared.The results show that the conical capillary is conducive to the formation of strong intermediate energy microbeam.For the transmission of low energy ions,the main mechanism is the guiding effect.The dynamic behavior of the charge patches governs the oscillations of angular distribution and is responsible for the width broadening.Our results show that the scaling laws for highly charged ion through in a conical capillary are extent same as that in nano-capillaries.The transmission rate and HWHM of transmitted ions are approximately linear with1/2?q/E_P?.At last,the calculations suggest that the conical capillary can provide stable transmission.