TEST OF THE GEM FRONT TRACKER FOR THE SBS SPECTROMETER AT JEFFERSON LAB

A new Large-Acceptance Forward Angle Spectrometer (Super BigBite) is under development at JLab/Hall A to optimally exploit the exciting opportunities offered by the 12 GeV upgrade of the electron beam. The tracking of this new apparatus is based on the gas electron multiplier technology, which has been chosen to optimize cost/performance, position resolution and meet the high hits rate (>1 MHz/cm2). The first gas electron multiplier detector prototypes were designed, built and tested at the DESY test beam facility in Hamburg, by using an electron beam with energy from 2.0 to 6.0 GeV. In particular, two gas electron multiplier chambers (10 x 10 cm2 and 40 x 50 cm2, respectively) were equipped with a new implementation of the APV25 readout chip. Measurements were performed at different impact points and angles between the electron beam and the plane of the gas electron multiplier chambers. In this report we present the technical characteristics of the detector and comment on the presently achieved performance.