Hybrid silicon μstrip and GEM tracker for JLab hall-a high luminosity experiments

A new hybrid silicon μstrip and large area GEM (Gas Electron Multiplier) tracker is under development for the upcoming high luminosity (up to 10³⁹ /s/cm²) experiments at the Hall-A of the JLab 12 GeV electron beam facility. The system consists of 2 small 10×20 cm² silicon planes placed near the scattering chamber and 18 40×50 cm² GEM modules that form larger chambers with variable active area depending on the experimental needs. Rather general purpose readout electronics has been designed for both detectors and can be adopted in other equipment. It consists of two active components: front-end cards, directly connected to the detector channels and a multi-purpose digitizer board (MPD). The front-end is based on existing 128 channels APV25-S1 chip developed in the framework of LHC experiments. The MPD handles 16 front-end cards (for a total of 2048 channels) and can be used in VME environments (also VME64x or VXS). It also provides: optical, Ethernet, USB. These resources permit to use MPD cards in different frameworks, ranging from small bench-top to large on-detector distributed systems. The GEM project is part of the CERN/RD51 collaboration activities. The system has been beam tested in late 2010 and 2011, some results are presented here.