MCP:Gain of Microchannel Plate
The gain of a Microchannel Plate (MCP) is determined by several core physical and operational factors.
- The supply voltage applied between the input and output sides of the MCP is critical, as the resulting potential gradient accelerates electrons, causing exponential multiplication. The gain characteristic is shown to depend directly on the supply voltage.
- The number of MCP stages or configuration chosen determines the overall amplification. A single plate typically yields a gain of 10^3 to 10^4. A Chevron configuration (two plates) provides 10^6 to 10^7 gain, and a Z-stack (three plates) can reach 10^7 to 10^8.
- The Aspect Ratio (α), defined as the ratio of channel length (L) to channel diameter (d), is fundamental in determining the gain. Gain is approximately related exponentially to this ratio. Advanced Performance MCPs often utilise a 60:1 aspect ratio to achieve higher gain compared to standard 40:1 ratios.
- The secondary emission factor inherent to the channel wall material determines the gain. Specialized coatings, such as Magnesium Oxide (MgO) or those applied using Atomic Layer Deposition (ALD) technology, can increase the secondary electron yield, leading to higher gain or allowing the same gain to be achieved at a lower operating voltage.
- Other factors include the channel diameter (pore diameter, d), as the maximum gain of saturation (for fixed voltage and aspect ratio) is proportional to the pore diameter. Output End-spoiling is also listed as a gain parameter, and the presence of a magnetic field can affect amplification, sometimes requiring increased high voltage to maintain the set gain.