Speaker
Description
The photomultiplier tube (PMT) based on microchannel plates (MCP) is one of the fastest types of the single photon detectors. When coupled with a Cherenkov radiator it allows the time of a charged particle to be measured with an accuracy of order of 10 ps. Such a time resolution may be of interest for future high-energy physics experiments.
One of the main limitations of MCP-PMTs is the short photocathode lifetime resulted from the feedback ions flow. Despite the recent significant reduction of the photocathode ageing in MCP-PMT due to the use of MCPs manufactured using ALD technology, the MCP-PMT lifetime is still an order of magnitude less than that of traditional PMTs with metal dynodes. This limits the application of MCP-PMTs in high rate environments like in future experiments at high luminosity LHC.
We study the possibility of using a new configuration of the photocathode in an MCP-based detector for precise time measurement of charged particle. This configuration is expected to reduce the effect of feedback ions going from MCPs and improve the photocathode lifetime. The idea is tested using ultraviolet CsI photocathodes prepared in the vacuum evaporation setup in Bologna. For testing we use in-house customised prototype equipped with a magnesium fluoride crystal as a Cherenkov radiator and the photocathode, followed by a pair of MCPs. The prototype has been repeatedly tested with particle beam at CERN and LNF (Frascati), routinely obtaining time resolution of 17 ps for single charged particle. The time resolution for semitransparent CsI photocathode deposited on MgF$_2$ Cherenkov radiator has been measured as well.
To check the advantage of the new design in terms of lifetime, we started an ageing test which compares its degradation rate with that of semitransparent photocathode, operating the two devices in the same conditions.
In the present contribution the experimental setup and the results of the various beam tests are presented and discussed, together with the status of the ongoing ageing test.
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