Abstract
We study aging of alkali-antimonide photocathodes in the microchannel platephotomultiplier tubes (MCP PMT) manufactured in Novosibirsk by ``Ekran FEP'' company.Such PMTs are used in the particle identification systems of KEDR, SND and CMD-3 experiments carried out at e+e− colliders VEPP-4M and VEPP-2000 in the Budker Institute of Nuclear Physics.The quantum efficiency (QE) degradation of a PMT equipped with MCP Chevron has been measured at different photon counting rates from 4⋅107 to 6⋅1010 s−1cm−2. It is found that the QE decrease is proportional to the charge extracted from the MCP nearest to the photocathode rather than to the output charge.The comparison of different types of alkali-antimonide photocathodes has shown that the treatment of photocathode with vapors of cesium and antimony can dramatically reduce the photocathode aging rate.The photocathode lifetime of the best MCP PMT sample has been measured at the photon counting rate of 107 cm−2s−1 and the initial gain of 106.The peak quantum efficiency degraded by 20% after accumulation of 3.3 C/cm2 anode charge.
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