Anode current saturation of ALD-coated Planacon® MCP-PMTs

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.

ATLAS Forward Proton Time-of-Flight Detector: LHC Run2 performance and experiences

“…A new, surprising, effect was observed: all tested tubes lost their gain for quite a long time after being exposed to the high signal rates. This observation was made also by ALICE group [10] and the effect was confirmed also for an ALD coated tube produced by Photek Ltd. A small study Relative signal value of the tested MCP-PMTs normalized to that of the reference PMT versus integrated number of counts (digitized pulse waveforms) [11]. [11] comparing tubes, with properties summarized in Figure 14, was made.…”

“…A new, surprising, effect was observed: all tested tubes lost their gain for quite a long time after being exposed to the high signal rates. This observation was made also by ALICE group [10] and the effect was confirmed also for an ALD coated tube produced by Photek Ltd. A small study comparing tubes, with properties summarized in table 2, was made [11]. The measurements of the recoverability time for each MCP-PMT is shown in figure 14.…”

Status of the Fast Interaction Trigger for ALICE Collaboration

“…The design details and results of tests of several FIT detector prototypes have already been published before (see [2][3][4][5][6]), as well as the simulated detector performance (see [7,8]). The focus of this paper is on the final FEE and its response to signals from real detectors.…”

Characteristic properties of Planacon MCP-PMTs

“…Laser light intensity was set constant throughout the measurement for each set of MCP-PMTs and monitored independently by the reference PMT, which was biased to a fixed voltage. The repetition rate was set to 1 kHz to mitigate the influence of the average anode current saturation [17,18]. The gain scan was performed by increasing the bias voltage in 25 or 50 V steps.…”