Signal processing to reduce dark noise impact in precision timing

Abstract

We introduce a technique to mitigate the effects of low frequency noise on precision timing.The example of Dark Count Noise Rate (DCR) in Silicon Photomultipliers (SiPMs) is emphasized.This technique exploits the correlation between time shifts onthe leading edge of a signal and the residual slope of the baseline (due to noise) which remainsafter baseline subtraction. In fast timing applications (such as for Time-of-flight particle ID) the signal arrival time is typically captured on the signal leading edge. The signal risetime is often fixed by the physics of the sensor and input circuit. Then accurate pulse timing can be achieved by correcting a leading edge threshold time (depending on a slope proportional to both the Amplitude and the risetime) to a “constant fraction” time. This compensation for time walk due to amplitude fluctuations breaks down once we introduce interference from low frequency noise on the leading edge. In this paper we demonstrate that an additional measurement of the slope at threshold can be used to correct for this noise jitter.