Transmission Of Hundred KeV Protons Through Insulating Nanocapillary

In this work, a MCP two dimensional position sensitive detector based on carbon anode is set up. By using this detector, we measured the time evolution of the transmission features, such as the charge states and position distributions, and the relative transmission rate of 10–100 keV protons transmitted through nanocapillaries in a PC membrane at a tilt angle of + 1°. The experimental data clearly show that the transmission mechanism of 30-100 keV protons is distinct from that of 10-20 ke V protons. After a sufficient charge-up period, 10 and 20 keV projectiles are guided through the capillaries, and the transmitted particles are located around the guiding direction of the capillary axis. However, for 30-100 keV projectiles, the centroid outgoing angle of the transmitted particles gradually shifts from the guiding direction to the direction of the incident beam during the later measurement stage; the centroid outgoing angle of the transmitted particles remains in this direction. Regardless of the projectile’s energy, three different types of forces will be exerted on the projectile when it is inside the capillary. The first type of force is the long-range Coulomb force from the deposited surface charges on the inner capillary wall. The second is the short-range collective scattering force from the topmost surface layer atoms. The third is the binary encounter force between the projectile and target atoms below the internal surface. When the projectile is above the surface, the Coulomb force and the collective surface scattering force work simultaneously. And the stochastic binary encounter force does not exist because the projectile does not penetrate into the inner capillary surface yet. But when the projectile penetrates into the surface, the binary encounter force is considered. That is, all of these three kinds of forces are taken into account when the projectile is under the surface. The importance of these three types of forces will be reversed with charge-up. After equilibrium, the greatest force will determine the ions’ transmission features in different energy ranges. The simulation results indicated that charge patch-assisted collective scatterings on the surface are the main transport mechanism for the hundred-keV ions in nanocapillaries. For low energies of several keV, the guiding force from the deposited surface charge patches is dominant. For high energies of Me V, the binary encounter force below surface is the most important. For intermediate energies of hundreds of ke V, the charge–patch-assisted collective scattering force on the surface is crucial. This scenario fills in the gap in the previous understanding of ion transmission in nanocapillaries from keV to MeV energies.