  Nowadays, Microchannel Plate (MCP), as a kind of electron multipliers based
on the secondary electron emission, is widely used in many high-sensitive
experiments, such as neutrino detection, which require the noise to be as low
as possible, while the conventional straight-channel MCP will inevitably have
ion feedback, resulting in the sequential after-pulses being the major source
of noise. Normally, the problem can be effectively avoided by coupling two
straight-channel MCPs in cascade and combining the channels into a `V` shape
known as chevron MCPs, but this method is limited by the manufacturing
techniques due to the unavoidable gap between the two pieces that will worsen
the resolution and peak-to-valley ratio. However, the ion feedback can be
inhibited significantly for MCPs with curved channels. Based on Geant4, we
investigate how the geometrical parameters of curved-channel MCP influence the
gain and get the optimum pore diameter for an MCP to reach the maximum gain
with fixed thickness and applied voltage. Additionally, the track-by-track
simulation reveals that the average acceleration distance of a secondary
electron inside the curved-channel is approximately 20 um when the applied
voltage, length-to-diameter ratio and pore diameter are 950 V, 50:1 and 20 um,
respectively.
