| Speaker: | Stefan Ritt (Paul Scherrer Institute) |
|---|---|
| Title: | Picosecond Timing for Particle Physics: Design Principles and Lessons Learned from the MEG II Experiment |
| Date (JST): | Mon, Jul 27, 2026, 13:30 - 15:00 |
| Place: | Seminar Room A |
| Abstract: |
Modern particle physics experiments increasingly rely on timing measurements with resolutions at the level of a few picoseconds to identify rare events and suppress background. Achieving such precision in detector systems with thousands of channels requires careful attention to every stage of the signal chain, from the detector front-end to system-wide clock distribution and calibration. This presentation reviews the fundamental principles of precision timing and discusses practical techniques for building large-scale timing systems with picosecond accuracy. Sources of timing uncertainty, including sensor noise, voltage fluctuations, clock skew, phase-locked loop (PLL) jitter, time-walk effects, and power-supply noise, are analyzed. Design approaches such as end-to-end differential clock distribution, low-noise power filtering with low-ESR capacitors, EMI mitigation, and optimized PLL architectures are presented. Special emphasis is placed on the practical design of SiPM-based timing detectors. Topics include front-end amplifier design, waveform sampling ASICs, discriminator architectures and FPGA-based timing extraction. The concepts are illustrated using the WaveDAQ readout system developed for the MEG II experiment at the Paul Scherrer Institute. The system provides low-jitter clock distribution and synchronized waveform digitization for more than 9,000 detector channels operating at up to 5 GSPS. Particular attention is given to the synchronization of multiple detector subsystems, including the Timing Counter, Liquid Xenon calorimeter, and drift chamber, and to the techniques used to maintain stable timing alignment over long periods of operation. The system has demonstrated clock-distribution jitter below 5 ps, with measurements as low as 1.9 ps between channels. Calibration strategies based on embedded clock sampling, laser systems, and physics events are presented, together with lessons learned from the six-year development and operation of the MEG II timing infrastructure. These experiences highlight the importance of treating timing as a complete system problem involving detectors, electronics, firmware, clock distribution, synchronization, calibration, and environmental stability. The presentation concludes with a practical recipe for achieving sub-5 ps timing performance in large-scale detector systems and discusses how these methods can be applied to future particle physics experiments as well as scientific and industrial applications requiring extreme timing precision. |
| Remarks: | Passcode 747197 |
