Small-Scale Readout System Prototype for the STAR PIXEL Detector

A prototype readout system for the STAR PIXEL detector in the Heavy Flavor Tracker (HFT) vertex detector upgrade is presented. The PIXEL detector is a monolithic active pixel sensor (MAPS) based silicon pixel vertex detector fabricated in a commercial CMOS process that integrates the detector and front-end electronics layers in one silicon die. Two generations of MAPS prototypes designed specifically for the PIXEL are discussed. We have constructed a prototype telescope system consisting of three small MAPS sensors arranged in three parallel and coaxial planes with a readout system based on the readout architecture for PIXEL. This proposed readout architecture is simple and scales to the size required to readout the final detector. The real-time hit finding algorithm necessary for data rate reduction in the 400 million pixel detector is described, and aspects of the PIXEL system integration into the existing STAR framework are addressed. The complete system has been recently tested and shown to be fully functional.