Multi-PMT optical module

In this paper we discuss the advantages of using many small photomultiplier tubes inside a cylindrical or spherical pressure vessel as an alternative to the “standard” large ( 10 ″ ) photomultiplier. The tube used for the test is the Photonis XP53x2 tube which has a diameter of 3 ″ . We show that in terms of signal to noise the small phototube solution is superior to the large tube. Tests show that the small tubes can be successfully operated feeding 12 tubes from a single high voltage power supply, using individual high resistance bases. The readout using a time over threshold technique has also been investigated and shows very promising results.