A Novel Peak Picking Multi-Voltage Threshold Digitizer for Pulse Sampling

The multi-voltage threshold (MVT) method employs comparators and time-to-digital converters to acquire the samples of a scintillation pulse when it crosses voltage thresholds and recovers the pulse using a prior model. It serves as a versatile pulse digitizing method in particle physics applications, including positron emission tomography (PET) and proton therapy verification. In these applications, the performance of the MVT method is sensitive to voltage threshold settings, leading to deteriorating energy resolution (ER) if the voltage thresholds are not selected for optimized pulse recovery. In this article, we propose a peak-picking MVT (PP-MVT) method that acquires the time and voltage of a pulse peak and recovers the pulse with MVT samples and peak information. Based on a dataset acquired from an LYSO/SiPM PET detector, we evaluate the performance of the two methods under four typical voltage threshold settings. The results show that the worst ER achieved by this method is 13.2%@511 keV, while that achieved by the MVT method is 16.3%@511 keV. Moreover, we implement a preliminary 1-channel peak-picking circuit, which has successfully captured the peak voltages of scintillation pulses. Based on this circuit, we are currently developing a 36-channel PP-MVT digitizer, where the readout unit is multiplexed, thus improving the ER of PET systems with little extra hardware complexity.