Status of the Lifetime Monitoring for the HCAL HPD's

The multi-pixel DEP hybrid photodiodes for HCAL are being monitored for changes in response under constant illumination corresponding to 10 years of CMS running at high eta. Currently, a pixel exposed to the equivalent of 3.3 CMS years at this location has experienced a reduction in response of less than 5%, where most of the change is due to an increase in the threshold voltage required to penetrate the dead layer on the silicon surface. The conclusion is that no changes will occur in most of the tubes in the barrel and endcap hadronic calorimeter, and that the tubes in the worst locations may experience a change of approximately 1.5% per year in a well-defined manner. It therefore seems reasonable to proceed with placing the first large-scale order of tubes on schedule this August 1999. Lifetime monitoring will continue throughout the next several years for a subset of all tubes received.