A TDC-based system for X-ray imaging detectors

This work presents an image acquisition system to be used with Position Sensitive Detectors (PSD). The system is based on a high-resolution Time-to-Digital Converter (TDC) and a Field Programmable Gate Array (FPGA). The detectors use gas as absorbing medium and make use of two delay lines to identify the coordinates of each detected particle. Reading the position information provided by the delay lines, the system is able to encode the position of incidence for an event in the detector window. The TDC translates the time information coming from the delay lines, while the FPGA is responsible for processing each event, controlling the whole system and communicating with a personal computer. 256 times 256 pixels images are stored into an on-board memory. This resolution is increased to 512 times 512 pixels by using a time multiplexing technique. The maximum data acquisition rate is 1.2 million events per second.