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Study of laser-beam arrival time synchronization towards sub-picosecond stability level

Konstantin Popov, Hiroshi Kaji, Tetsuya Kobayashi, Aurelien Martens, Daniel Charlet, Cedric Esnault, Antoine Back, Paul-Eric Pottie, Fabian Zomer, Alexander Aryshev

TL;DR

This paper tackles the challenge of achieving sub-picosecond synchronization between laser pulses and electron beams in large accelerators by implementing a White Rabbit–disciplined IDROGEN carrier board to distribute RF sub-harmonic references over optical fiber. The approach combines a WR timing node, an in-FPGA phase comparator, and SkyWorks SI5362 synthesizers to deliver 178.5, 357, and 508.9 MHz references with ps-level phase stability, validated through tests at CNRS/IJClab, KEK ATF, and SuperKEKB. The results show sub-picosecond to a few-picosecond RMS jitter and long-term phase drift of a few tens of picoseconds, indicating the scheme’s viability for laser diagnostics and LLRF systems in large facilities. This work supports scalable, low-maintenance timing delivery for remote laser-based diagnostics and paves the way for km-scale links and closed-loop laser-to-beam stabilization in modern accelerators.

Abstract

A precise synchronization between laser pulse and electron beam arrival time is essential for achieving sub-picosecond stability in modern accelerator facilities. In this work, a Low-Level RF system architecture combined with White Rabbit based timing system has been tested through a collaboration between KEK (Japan) and CNRS/IN2P3, IJClab (France). The setup combines a frequency standard generator, an IDROGEN carrier board with an embedded White Rabbit node, and SkyWorks synthesizers of different form factors to distribute phase-locked clock signals over telecommunication fiber. Phase noise power spectral density measurements were performed at several RF sub-harmonics to confirm synchronization performance. These results demonstrate the feasibility of implementing the White Rabbit-IDROGEN synchronization scheme for large-scale accelerators, including applications to laser-based diagnostics.

Study of laser-beam arrival time synchronization towards sub-picosecond stability level

TL;DR

This paper tackles the challenge of achieving sub-picosecond synchronization between laser pulses and electron beams in large accelerators by implementing a White Rabbit–disciplined IDROGEN carrier board to distribute RF sub-harmonic references over optical fiber. The approach combines a WR timing node, an in-FPGA phase comparator, and SkyWorks SI5362 synthesizers to deliver 178.5, 357, and 508.9 MHz references with ps-level phase stability, validated through tests at CNRS/IJClab, KEK ATF, and SuperKEKB. The results show sub-picosecond to a few-picosecond RMS jitter and long-term phase drift of a few tens of picoseconds, indicating the scheme’s viability for laser diagnostics and LLRF systems in large facilities. This work supports scalable, low-maintenance timing delivery for remote laser-based diagnostics and paves the way for km-scale links and closed-loop laser-to-beam stabilization in modern accelerators.

Abstract

A precise synchronization between laser pulse and electron beam arrival time is essential for achieving sub-picosecond stability in modern accelerator facilities. In this work, a Low-Level RF system architecture combined with White Rabbit based timing system has been tested through a collaboration between KEK (Japan) and CNRS/IN2P3, IJClab (France). The setup combines a frequency standard generator, an IDROGEN carrier board with an embedded White Rabbit node, and SkyWorks synthesizers of different form factors to distribute phase-locked clock signals over telecommunication fiber. Phase noise power spectral density measurements were performed at several RF sub-harmonics to confirm synchronization performance. These results demonstrate the feasibility of implementing the White Rabbit-IDROGEN synchronization scheme for large-scale accelerators, including applications to laser-based diagnostics.
Paper Structure (7 sections, 5 figures, 3 tables)

This paper contains 7 sections, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. IDROGEN carrier board and its synthesizer
  3. Low-level test at CNRS/IN2P3, IJClab
  4. Low-level test at KEK ATF
  5. Low-level test at SuperKEKB
  6. Conclusion
  7. Acknowledgement

Figures (5)

  • Figure 1: The synchronization performance measurement setup: (a) is the block diagram, (b) is the signals PN-PSDs
  • Figure 2: The phase stability measurement results: (a) is the SkyWorks SI 5362-A-EVB synthesizer relative Rohde&Schwarz SML03 SG phase drift vs time, (b) is the SkyWorks SI 5362 FMC synthesizer relative Rohde&Schwarz SML03 SG phase drift vs time, (c) is the SkyWorks SI 5362-A-EVB synthesizer relative the SkyWorks SI 5362 FMC synthesizer phase drift vs time
  • Figure 3: The synchronization performance measurement setup: (a) is the block diagram, (b) is the signals PN-PSDs
  • Figure 4: The synchronization performance measurement setup: (a) is the block diagram, (b) is the signals PN-PSDs
  • Figure 5: The phase stability measurement results