MCP: Saturation Effects

Saturation effects in MCP are the phenomena that limit the performance and the reliability of the MCP detector when the input signal or the output voltage is too high.
Some of the saturation effects in MCP are:
  • Charge depletion: This is the effect of exhausting the available charge in the microchannels due to a high input signal or a high output voltage. Charge depletion reduces the gain and the output current of the MCP, and causes a nonlinear response and a distortion of the output signal.
  • Space-charge field limitation: This is the effect of creating a negative electric field inside the microchannels due to the accumulation of electrons. Space-charge field limitation opposes the applied electric field and reduces the acceleration and the energy of the electrons. This also reduces the gain and the output current of the MCP, and causes a nonlinear response and a distortion of the output signal.
  • Secondary emission surface effects: This is the effect of changing the secondary emission coefficient of the channel wall due to a high input signal or a high output voltage. Secondary emission surface effects alter the electron multiplication and the gain of the MCP, and cause a nonlinear response and a distortion of the output signal.
Saturation effects in MCP can be avoided or minimized by using appropriate parameters and techniques, such as:
  • Reducing the input signal or the output voltage to a level that does not exceed the maximum ratings of the MCP.
  • Using a pulsed voltage or a gating circuit to control the duration and the frequency of the voltage applied to the MCP.
  • Using a resistance coating or a bias angle to optimize the electrical and thermal properties of the MCP.
  • Using a superlinearity technique to counteract the gain saturation mechanisms by using a tailored bias string.