MCP: How Does Bias Angle Affecting Gain

What is Bias Angle?

The bias angle refers to the angle at which the channels in the microchannel plate are tilted relative to the plate's surface.

The Relationship Between Bias Angle and Gain

Gain, measures the MCP's ability to amplify the number of electrons. This relationship can be described by a simplified equation:
Gain Equation: Gain = base × (1 + k × BiasAngle)
Here’s what each component represents:
  • base: The baseline gain when the bias angle is 0° (no tilt).
  • k: A constant that depends on the MCP material and design, representing the sensitivity of gain to changes in bias angle.
  • BiasAngle: The tilt angle of the channels (in degrees).

A Pseudo-Case Example

To better understand the equation, consider this practical scenario:
If the base gain is 1000, k is 0.12, and the bias angle is 10°, then:

Gain = 1000 × (1 + 0.12 × 10) = 1000 × 2.2 = 2200
This example shows that increasing the bias angle leads to a higher gain, which aligns with the underlying physics of electron multiplication in MCPs.

Why More Bouncing Means Higher Gain

Each time an electron hits the wall of a microchannel, it can will generate more electron with secondary emission. A larger bias angle lengthens the electron’s path through the channel, increasing the number of times it bounces off the walls. More bounces mean more opportunities for secondary emission, resulting in a greater total number of electrons and thus a higher gain.

Explore Interactively

To visualize how changes in bias angle affect gain in real time, you can interact with the web app embedded below:

By adjusting the bias angle in the app, you can observe firsthand how the electron path length and, consequently, the gain change—reinforcing the principles we’ve discussed.