3. Monte-Carlo simulation
We investigated the trajectories of protons in the tapered glass
capillaries by a Monte-Carlo code, which was originally developed
for this purpose. The code takes into account only elastic collisions
between protons and nuclei in the capillary wall, so the classical
Rutherford formula is used to calculate the scattering cross sections.
On the other hand, the energy loss of protons is evaluated
from the electronic stopping power given in SRIM2008. We performed
Monte-Carlo simulations by using the wall shape data of
the tapered capillary used in experiments. The number of incident
particles was typically 106
.