KEK Accelerator Test Facility Low-Level RF and Timing Systems

TL;DR

This paper discusses the KEK ATF's low-level RF and timing systems, focusing on achieving femtosecond-level synchronization crucial for nanobeam technology in support of the ILC.

Contribution

It provides detailed measurements of the phase-noise power spectral density of the KEK ATF LLRF clock and analyzes its impact on synchronization stability.

Findings

Achieved ~100 fs synchronization stability.

Identified the phase-noise floor set by signal generator stability.

Provided facility-wide phase-noise measurements and analysis.

Abstract

The KEK Accelerator Test Facility (ATF) is a dedicated testbed for nanobeam technologies in support of the International Linear Collider (ILC). Stable pulsed operation requires synchronization of the facility timing system with the Low-Level RF (LLRF) system. The timing system distributes trigger and gate signals to key subsystems, including the DAQ, klystrons, laser systems, pulsed kicker magnets, and interlocks. The LLRF system provides phase-coherent RF references and facility-wide clock distribution for synchronization. Achieving ~100 fs-level synchronization depends critically on the phase-noise power spectral density (PN-PSD) of the distributed clock signals and on preserving this performance throughout the distribution network. We present facility-wide measurements of the KEK ATF LLRF clock PN-PSD and discuss the resulting synchronization floor imposed by the stability of the ATF Linac and Damping Ring signal generators.