The microchannel plate-photomultiplier tube (MCP-PMT), a kind of compact high-sensitive photo device consisting of photocathode, MCPs, anode and tube shell, has attracted much attention in the field of modern high-energy physics detection.

However, the damage caused by the ions feedback in the channel to the photocathode limits the lifetime of the MCP-PMT. To solve the problem, the atomic layer deposition (ALD) technique is used to deposit the novel separate resistive and emissive layers onto the inner surface of the channel.

A research team led by Prof. Dr. TIAN Jinshou from Xi'an Institute of Optics and Precision Mechanics (XIOPM) of the Chinese Academy of Sciences (CAS) revealed how the secondary electron emission (SEE) yield properties of the emissive materials affect the behavior of the ALD-coated MCP.

Their findings were published in Nuclear Instruments and Methods in Physics Research.

Fig. 1 Schematic structure and principle of the MCP (Image by XIOPM)   

The researchers investigated the situation about three important secondary electron emissions - the backscattered, rediffused and true SEE, respectively.

They made all settings the same as the conventional MCP, and then changed the key parameters with other parameters unchanged to derive the main characteristics of the ALD-coated MCP, gain and timing performance, and dependency, etc.

The simulation results indicated the opportunities for improving the gain of the ALD-coated MCP by improving the SEE yields corresponding to the incident energies of 0eV-100eV.

"We found that the backscattered and rediffused electrons have strong effects on the gain and timing performance of the MCP. Although the higher the SEE yield the higher the MCP gain, the extremely high SEE yield will make the MCP saturated prematurely and degrade the time resolution," said Dr. TIAN.

This work may provide inspiration to the study and selection of material of emissive layer and provide references for developing the next generation ALD-coated MCP-PMT.

Fig. 2 Cross section of the 3D model of the MCP single channel (Image by XIOPM)