This detector is a mosaic of fully depleted silicon detectors that cover the aperture of the ATIC instrument and is used to make an accurate charge identification of the incident cosmic ray from H to Fe, in the presence of "backscatter" background. The ATIC matrix is based upon a similar design built for the ZEUS experiment at DESY. Fifty six silicon diode strips, further subdivided into four ~2 cm by 1.5 cm pads, are arranged on two motherboard assemblies, one above the other, to form a ladder. The strips on the top half are offset to cover the gaps between strips on the bottom half. Twenty such ladders are then arranged to cover an active area of about 1 m by 1 m. The full detector includes 4,480 independent pads that are read out by an ASIC designed for this application; the CR-1. The remainder of the  detector readout is similar to that used for the calorimeter and hodoscopes. Details on the silicon matrix detector and the CR-1 ASIC can be found elsewhere at this conference (Adams Jr. et al., 1999a,b)

Silicon Matrix detector components


Individual pixels in the Silicon Matrix