In situ measurement of "Open Window" electron multipliers\´ gain

In this paper, a simple electronic method for the in situ measurement of the multiplier gain of "open window" electron multipliers is described. The parameter , which is measured for the first time for these devices, is of great relevance because, if the geometrical factor F is known, it allows to determine the total multiplier gain of the detectors. In its turn, the total multiplier gain , together with the quantum efficiency η, provides a complete absolute calibration of the multiplier. The use of a software multichannel analyzer (MCA), as proposed in this implementation of the calibration method, increases not only the good value, but also the versatility of the technique, rendering it a simple routine procedure. For one multiplier, suitably modified, it has also been possible to measure, in addition to the electron gain , the geometrical factor F and the total multiplier gain directly. The agreement between these measurements confirms the validity and the interest of the technique adopted to determine . Moreover, the reported tests prove that with a simple modification of the multiplier, which could be simply implemented by the manufacturers, a complete characterization of the geometrical and electrical properties of the device would be possible in a relatively simple way.