MCP: Ion-Feedback

Ion feedback is an issue of MCP that occurs when the electron avalanche in the microchannels ionizes some atoms from the residual gas or the channel wall. These ions are then accelerated by the electric field towards the input side of the MCP, where they can cause damage, noise, and false signals.
Ion feedback can be reduced by using shorter and tilted channels, stacking MCPs with a chevron or a Z-shape configuration, using an ion barrier film on the photocathode, and using a pulsed or a gated voltage.