Custom HPD readout for the CMS HCAL

Over 10 000 channels from the CMS tile/fiber hadronic calorimeter (The CMS Hadron Calorimeter TDR, CERN/LHCC 97-31, June 20, 1997) will be read out by custom 19 and 73-channel HPDʹs in a 4 T field. Experimental constraints on the tube design have produced a faster tube with a larger active area and minimum accelerating gap. Quality assurance stations have been developed for fast processing of 600 tubes. Registration to 50 μm is done in situ, providing a custom collar with alignment pins which can be mated to a universal cookie. Lifetime measurements reveal details on aging, but operation is within CMS specifications.