Fully FPGA-based 3D (X,Y,t) imaging system with Cross Delay-Lines detectors and Eight-Channels High-Performance Time-to-Digital Converter

Time resolved experiments are among the most powerful tools in physic for exploring photoelectron spectroscopy phenomena over time scales from milliseconds to picoseconds Moreover, acquisition systems with versatility and real-time computing are needed. Cross Delay-Lines detectors (CDL) are extremely suitable for these applications, since arrival time measurement is exploited to perform position detection, allowing to provide both information together. Typical architectures for acquisition systems are based on Aplication Specific Integrated Circuit (ASIC) Time-to-Digital Converters (TDCs) followed by a Field Programmable Logic Array (FPGA); fast parallel computing is combined with time precision, allowing to perform stateof- the-art time resolved experiments. Nevertheless, the limiting factor of this architecture is the absence of reconfigurability of the ASIC that strongly limits the customization respect to the requests of a specific set-up. Especially today, where the state-ofthe- art TDCs implemented in FPGA, is comparable to the ASIC solutions. In 2019 Nuclear Science Symposium, we presented a fully-reconfigurable FPGA-based solution, where the TDC and the image reconstruction algorithm were hosted in two FPGAs. In particular, we focused on the 4-channel TDC that, guarantees high-performance in terms of resolution (1 ps), Full-Scale Range (200 μs), Integral Non Linearity, (4 ps over 500 ns). In this contribution, we give significant improvements in order to satisfy the aforementioned experimental experimental requests. In fact, the “pulse-to-pulse” dead-time of the TDC has been reduced from 20 ns to 7 ns, and the transmission rate between the FPGAs has been incremented from 10 to 100 Msps. Furthermore, we have increased the number of channels of the TDC from 4 to 8. This makes possible to correlate the CDL events with signals coming from other sources that can be as well Time-of-Fight or laser pulses as other CDL signals.