The hadronic calorimeter for the CMS experiment requires
photodetection in a 4 Tesla magnetic field. This, plus high
neutron radiation and a 25 ns bunch-crossing, necessitated the
development of a new type of high-rate multi-channel hybrid
photodiode. As our specifications became tighter, design
changes in the diode structure and surface treatment became
necessary, resulting in a better product with very low
crosstalk in both AC and DC modes. The specifications are
rigorous and are maintained by a set of automated Quality
Assurance stations which will process 570 tubes over 2 years.
Abstract: