Performance of the 20-inch dynode-photomultiplier tube with high quantum efficiency

A new type of 20-inch photomultiplier tube with high quantum efficiency was developed by Hamamatsu. Three samples of the new model were characterized on both photocathode and dynode performance. High quantum efficiency around 30% and good uniformity of the photocathode were found for all three pieces. Results of charge spectra and signal counts show that the new model has good charge resolution and high collection efficiency. The anode uniformity is evaluated and stability within the effective area is proved. On the other hand, relatively high after pulse rate is found within the new tubes.