A multi-channel constant fraction discriminator for atom probe tomography

Abstract This work presents the development and performance evaluation of a multi-channel constant-fraction discriminator (CFD) designed for delay-line position-sensitive microchannel plate detectors in atom probe tomography systems. The proposed architecture incorporates a zero-crossing level adjustment circuit to mitigate timing errors caused by signal variations. Additionally, a dedicated zero-crossing level monitor enables real-time evaluation of walk compensation effectiveness, ensuring optimal timing accuracy. This architecture achieves a time walk of ±57 ps across the full dynamic range (100–2000 mV). Quantitative analysis identifies an optimal input range of 500–1400 mV, which minimized overall temporal uncertainties, resulting in a total timing error of 20 ps (root-sum-square, RSS) accounting for both time walk and jitter. Experimental validation demonstrates that the discriminator sustains sub-20 ps timing resolution across a range of detection event amplitudes. These results meet the critical requirements of high-precision time-of-flight mass spectrometry and ion projection imaging applications.