A High Precision Time Measurement Method Based on Frequency-Domain Phase-Fitting for Nuclear Pulse Detection

This article proposes a high-precision time measurement method based on digital frequency-domain phase-fitting (DFPF) by using digitized nuclear pulses. The averaging effect inherent in the frequency-domain cross correlation and phase-fitting processes effectively minimizes measurement errors, thereby ensuring high precision and resolution in time interval measurements. In this article, the theory of this DFPF-based time measurement method is analyzed, and an electronics prototype is designed to validate the feasibility of the proposed method by utilizing analog-to-digital converters (ADCs) for pulse digitization and a field-progammable gate array for phase fitting implementation. The test results indicate that under ideal conditions with a signal-to-noise ratio (SNR) of 64 dB, this method achieves time measurement precisions of 50-, 18-, and 2.9-ps rms, corresponding to different Gaussian pulse widths and sampling rates of 118 ns at 40 MSPS, 10 ns at 100 MSPS, and 3 ns at 500 MSPS, respectively. The precision improves with increasing pulse bandwidth. Furthermore, in practical cosmic ray tests, the method achieved favorable timing performance with a precision of 1.7-ns rms. These results demonstrate that this proposed method has the potential to be a high-precision time measurement for particle detection and is equally applicable to other advanced time measurement scenarios.