Anode current saturation of ALD-coated Planacon MCP-PMTs

TL;DR

This study compares ALD-coated and non-ALD Planacon MCP-PMTs, revealing unexpectedly low current saturation and high gain recovery times in ALD-coated sensors, indicating potential technological challenges for ALD coating processes.

Contribution

The paper provides the first comparative analysis highlighting significant performance issues in ALD-coated MCP-PMTs, suggesting possible side-effects of the ALD process affecting device performance.

Findings

ALD-coated MCP-PMTs have ~100x lower current saturation than expected.

ALD-coated sensors exhibit gain recovery times over 10^7 times longer than expected.

Non-ALD MCP-PMTs show excellent performance, contrasting with ALD-coated counterparts.

Abstract

We have measured and compared the characteristics of ALD-coated Planacon MCP-PMTs (XP85112/A1-Q-L) with their non-ALD counterparts (XP85012/A1-Q). While the later show excellent performance, the ALD-coated sensors have surprisingly low current saturation levels (~two orders of magnitude lower than expected) and extremely high gain recovery time (more than 7 orders of magnitude higher than expected). We suspect that these problems might be caused by the unexpected side-effects of the ALD process. To make a definite conclusion, more samples need to be tested, preferably from different production runs. If our observation were confirmed, it would mean a serious technological setback for ALD-coated MCP-PMTs.