A Study of the Gain of Microchannel Plates in the Ionization Profile Monitors at Fermilab

TL;DR

This paper investigates the decrease in gain of microchannel plates in Fermilab's ionization profile monitors, exploring whether aging or initial scrubbing effects are responsible for the observed gain reduction.

Contribution

It presents experimental studies on MCP gain loss, comparing aging effects with initial scrubbing phenomena in Fermilab's IPMs.

Findings

Gain decreases over time in MCPs used in Fermilab IPMs.

Initial scrubbing may contribute to gain stabilization.

Aging effects are a significant factor in gain reduction.

Abstract

One of the on-going issues with the use of microchannel plates (MCP) in the ionization profile monitors (IPM) at Fermilab is the significant decrease in gain over time. There are several possible issues that can cause this. Historically, the assumption has been that this is aging, where the secondary emission yield (SEY) of the pore surface changes after some amount of extracted charge. Recent literature searches have brought to light the possibility that this is an initial 'scrubbing' effect whereby adsorbed gasses are removed from the MCP pores by the removal of charge from the MCP. This paper discusses the results of studies conducted on the IPMs in the Main Injector at Fermilab.