In order to develop a long-lifetime MCP-PMT under high rates of circumstance, we investigated the degradation of the quantum efficiency (QE) of PMT's with a multialkali photocathode. We found that not only positive ions, but also neutral residual gases would damage the photocathode resulting in an enhancement of the work function; their countermeasures were established in newly manufactured square-shaped MCP-PMT's with 4 or 4x4 multi-anodes. The performances of the PMT's were measured: QE was stable up to an integrated amount of anode output charge of 2-3 C/cm^2, while keeping other basic performances steady, such as the time resolution for single photons of ~40 ps, a photoelectron collection efficiency (CE) of 60%, a multiplication gain (G) of a few x 10^6, and dark counts of 20-300 Hz. The causes of QE degradation are discussed.
@article{arxiv.1010.1057,
title = {Lifetime-Extended MCP-PMT},
author = {T. Jinno and T. Mori and T. Ohshima and Y. Arita and K. Inami and T. Ihara and H. Nishizawa and T. Sasaki},
journal= {arXiv preprint arXiv:1010.1057},
year = {2011}
}