Timestamp and Amplitude Measurement Solution for Radiation Detectors

Timing has seen an important growth in modern applications like nuclear measurements, digital imaging for SPECT, photon counting, and energy discriminating detectors, just to cite the most commons. In this seance, high-performance Time–to–Digital Converters (TDCs) play a very important role. However, in many applications is quite important acquiring not only the timestamp relative to the arrival time of particles over a specific detector but also the energy itself, that can bring trace as different amplitude levels on the output analog signal. In this paper, we try to find an easy solution to measure the amplitude of the input signal pulses using a multi-channel mixed-signal system composed by a quite fast analog front-end peak detector in a super diode configuration, design with its own Printed-Circuits-Board (PCB), followed by an Analog-to-Digital Converter (ADC) interfaced by a Serial-Peripheral-Interface (SPI) to an FPGA. Moreover, the FPGA hosts a high-performance TDC that is in charge to extract the timestamp to concatenate at the amplitude information. We will use an approach based on Field-Programmable-Gate-Array (FPGA), that is economically more compatible with the scale of the research environment. This choice allows fast time-to-market, fast-prototyping and low non-recursive engineering cost. The PCB will be subsequently connected through a FPGA Mezzanine Card (FMC) connector to the Diligent Nexys Video board in which is host the Artix 200T FPGA. The channel resolution (LSB) of the TDC is 36.6 fs, the number of bit of the ADC is 10, the LSB is FSR(5 V)/2
¹⁰
= 4.88 mV and the acquisition rate for each channel is 3 M sps.