Improved Rise Approximation Method for Pulse Arrival Timing

This paper describes the deduction of pulse arrival times from digital waveforms recorded with a multichannel data-acquisition (DAQ) system. A linear rise approximation (LRA) arrival timing method provides restricted timing resolution for pulses with nonlinear rise. It reaches 1/20th of the sampling period, if the relation between signal shaping and sampling rate is optimized. We introduce a nonlinear rise approximation (nLRA), which reduces the sampling phase error (SPE) down to less than 1/100th of the sampling period. The proposed timing algorithm uses a single free parameter that can easily be adjusted for various radiation detectors. The technique permits using a rather slow pulse shaping and low sampling rates, thus strongly reducing power consumption and the costs of the system. A high-density DAQ system integrating over 2000 channels inside an OpenVPX crate is presented. A prototype has been tested in the proton beam at cooler synchrotron (COSY) at Jülich Research Center (Germany).