The PMT test system

The photomultipliers (PMT) installed in the cameras of the Fluorescence Detector are XP3062 with photocathode of hexagonal shape, produced by Photonis.  The standard tests on the PMTs are done at the factory.  Afterwards the HE boards (active divider + driver) are soldered to the flying leads of the PMT.  The test system in Roma was designed to test the complete unit PMT+HE.
The system allows simultaneous test of 24 PMTs. For each PMT the high voltage dependence of the gain, the linearity as a function of the incident light intensity, the sensitivity and the uniformity of the photocathode response are measured.   A measurement of the spectral sensitivity using narrow band filters was also done.

The matrix of 24 hexagonal PMTs to be tested

Back view of the matrix of 24 PMTs.

The divider and the driver are mounted on the two small round printed boards.

Front view of the 24 PMT matrix with light mask as mounted inside the test box

The test box with the light sources and filter system

A Xe lamp and a blue emitting LED were used as light sources

Neutral attenuating filters and narrow band filters were used, mounted on automatized wheels

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