The Transmission Of Negatively Charged Particles Through The Insulating Nanocapillaries

This thesis focuses on the transmission of negatively charged particles through the insulating nanocapillaries.It is found that the guiding is not established during the negatively charged particles transmitting through the insulating nanocapillaries,the scattering process dominates the transmission of negatively charged particles instead.The main work as follows:1.A monte carlo simulation is developed in the frame of the GANT 4（Geometry and Tracking 4）to study the transmission of low-energy Cl^-ions through Al₂O₃insulating nanocapillaries.The force of the deposited charges and the image charges,the scattering process and the charge exchange are considered in the simulation.In the case of tilt angle larger than the geometrical allowed angle,the transmitted angular distributions and the charge state distributions are simulated for various quantities of deposited charge.It is found the deposited negative charge lead to the transmitted Cl^-ions dominate the transmitted particles exiting to the direction of the axis of the capillary,and the double-peak structure disappears.While the simulated transmitted angular distribution and the charge state distribution of the case without the deposited charges,agree well with the experimental results:the transmitted Cl^-ion exit to the direction of the primary beam directly,the transmitted Cl⁰ and Cl⁺exit to the direction of axes the capillaries.Then the simulation is performed at various tilt angle without considering the deposited charges,it is also agreed well with the experiment.It suggested that the characteristics of the transmission of low-energy Cl^-ions through the insulating nanocapillaries are caused by the scattering process and the charge exchange,while the negatively deposited charges do not facilitate the transmission.The scattering process is analyzed in details.It is found the Cl⁺exit by single scattering,the Cl⁰ exit by single and double scattering.The portion of Cl⁰ exiting by double scattering increases with the increase of the tilt angle.2.The transmission of electrons with incident energies of 2000 eV and 2500 eV through PET（Polyethylene terephthalate）was studied by experiments.It is found the transmission mainly occurs in the geometrical allowed angle（the largest angle for particles through the nanocapillaries without touching the inner wall of the capillaries）,the transmitted electrons are centered around the direction of the primary electron beam.The transmission rate at tilt angle 0^o is higher for higher incident energy,and the transmission rate is two orders of magnitude lower than the geometrical transparency of the nanocapillaries.The transmission rate drops faster for the higher incident energy as the tilt angle moves away from 0^o.The time evolution of Transmitted electrons at the initial charge angle shows that the transmitted beam broadens,the transmission rate drops as the accumulation of incident charge,but the peak position of the transmitted angular distribution does not change much.A simulation is performed to understand the time evolution of the transmitted electrons,it is found the majority of incident electrons experience scattering with the capillaries and settle down in the bulk of the capillary membrane.The directly transmitted electrons distribute near the direction of the primary beam,and the transmitted electrons undergoing scattering spread much wider around the direction larger than the tilt angle of the capillary.The deposited charge does not form a guiding electric field to support the transmission of electrons,in contrary to the highly charged ions,the deposited charge forms a Coulomb field blocking the transmission of electrons instead.