Taper angle dependence of the dynamical transmission of several-hundred-keV protons through PC conical capillary

The dynamical transmission of intermediate-energy protons through a polycarbonate (PC) conical capillary with taper angle from 0.48° to 2° are simulated. The results show that for small taper angle of 0.48°, the transmission of 100 keV protons is dominated by the deposited-charge-assisted specular reflection. This reflection effect decreases with the increase of the taper angle. When the taper angle is increased to 2°, the transmission of the protons is mainly influenced by small angle scattering, which is consistent with the experimental data. The asymptotic transmission rate decreases with the increase of the capillary taper angle. These results suggest that the deposited-charge-assisted specular reflection is significant in focusing several-hundred-keV protons.