The ongoing work to upgrade ALS to ALS-U demands strict RF requirements such
as low jitter and low spurs frequency reference to meet its accelerator and
science goals. A low phase noise dual frequency Master Oscillator (MO), where
the two frequencies are related by a fractional ratio of 608/609 and flexible
divide by four frequency outputs has been consolidated into a single chassis.
Optical fiber clock distribution system has been selected over the old coax
system used in ALS to distribute these signals to various clients across the
facility, providing high electrical isolation between outputs and therefore
lower phase errors. A Xilinx FPGA ties the MO chassis together by providing a
RS-485 interface to monitor and control the system. The new system aims to
deliver phase-continuous frequencies with a phase noise (integrated RMS jitter)
from 1 Hz to 1 MHz of less than 200 femtosecond per output. This paper will
discuss the design, implementation, performance and installation of the new MO
generation and distribution system.Comment: Poster presented at LLRF Workshop 2023 (LLRF2023, arXiv: 2310.03199