Aging tests of MCP PMTs and MAPMTs Peter Križan University of Ljubljana and J. Stefan Institute SuperB meeting Perugia, June 17, 2009

Contents Aging tests of Photonis/Burle MCP PMT Aging tests of Hamamatsu MAPMTs

Aging of MCP-PMTs BURLE 85011 microchannel plate (MCP) PMT: multi-anode PMT with two MCP stages degradation of the photocathode  lower QE degradation of the MCP pore surface (secondary emission) lower amplification Potential problem: residual molecules in the tube vacuum are ionized by secondary electrons  travel to the photocathode

MCP PMT aging test Idea: Uniformly illuminate MCP by LED Monitor illumination by a reference PMT Rate ~1 Mhz per channel Record counting rate for 14 channels (out of 64) and total anode current Regularly check: the single photon pulse height distribution (by using pulsed laser) every hour  quantum efficiency (by using a monochromator, normalize relative to a calibated PMT)

MCP PMT aging test status Last week: measure QE across the surface Illumination started last week with initial 50k per channel (~0.2 microA per tube) Illumination increased this Monday (June 15) such that rate ~1 Mhz per channel (~3 microA per tube) Total charge now: 20mC per cm2, no change in peformance Plan: continue for the next three weeks, accumulate 0.2C per cm2

MCP PMT ageing – data from Burle/Photonis Several discussions with Emile Schyns, Group Product Manager, Micro Channel Plates Standard tube performance (without no Al protection layer):  50% drop of efficiency after 10-15C/tube = 350-540mC/cm2 Photonis: expect to improve the ageing by a factor >5 (use a different scrubbbing technique, deep UV  electrons) Testing of new tube samples are underway right now, very encouraging, by mid July expect 0.5C/cm2

Multianode PMT aging test Idea: Use tubes that were used in the HERA-B experiment (Hamamatsu R5900 16 channel PMTs with bialkali photocathode) Compare the performance of tubes that were in a highly illuminated area (few MHz per channel) with tubes at the periphery (5-10x less). Compare to the original QA measurements before the installation

Multianode PMT aging test- status Measured the tubes from the periphery, in agreement with the initial response (before installation) MA PMTs from the highly exposed region are waiting for the other aging test (MC PMT) to finish (they share the same set-up)  probably late July or even later