Study on FPGA-based multi-channel digitizing method for nuclear pulse amplitude

The basic principle of nuclear radiation detection is converting the incident ray to the measurable electrical signal by a detector. Reading and digitizing signals from detectors is the first step of nuclear signal processing, and often the most important step. We present a novel method for nuclear pulse amplitude digitizing which possibly realizes high integration multiple channels with an FPGA. The method first transfers the amplitudes into time intervals by modifying the shape of decay edge linearly, and then the time intervals are measured by TDC realized inside of FPGA. Since FPGA based multi-channel TDC techniques can be integrated inside of an FPGA, our method is quite promising to realize multi-channel digitization for nuclear pulses which is very crucial to detectors for nuclear imaging. In the paper, we concentrate the designs of key circuits, including pulse width modulation, TDC, constant fraction discrimination timing. Through a prototype implementation, we verified our design, investigate the factors which could influence the performance of this new method, and exploit a number of possibilities to use resources of the FPGA to enhance the integration for multi-channel design.