The Trigger detector consists of 2 plastic scintillators read by PMTs Hamamatsu. The first plane S1 (20 x 18 x 0.5 cm3), placed just below the silicon detector, is segmented along the y direction in 6 counters (20 x 3 x 0.5 cm3), each read by 2 PMTs, one on each side. The second plane S2 (15 x 15 x 1 cm3) is located on the top of the calorimeter. It is read by 2 PMTs, one on each side.
View of trigger counters (1st Trigger plane S1) and support structure