Status of the Phase Reference Line for the European Spallation Source

K. Czuba, J. Berliński, Ł. Czuba, E. Fistek, M. Kalisiak, T. Leśniak, K. Oliwa, R. Papis, D. Sikora, W. Wierba, M. Żukociński (Warsaw Univ. of Techn., Poland), A. Sunesson, R. Zeng (European Spallation Source, Sweden)

The 600 m long accelerator and beam transport of the European Spallation Source requires precise phase synchronization of LLRF and Beam Diagnostics systems. Accelerator subsystems are operating at frequencies of 352 MHz and 704 MHz. The required phase accuracy at both frequencies is 0.1° for short term (during 3.5 ms pulse), 0.1° for long term between adjacent outputs and 2.0° for long term (hours to days) between any two points. The main part of the phase reference distribution system is Phase Reference Line (PRL), which is a fully passive system based on a single 1-5/8” coaxial rigid line placed along the tunnel. The PRL was designed to distribute both reference frequencies from a Master Oscillator to 56 tap points in the tunnel. Each tap point has several (3 or 6) signal outputs. The total length of the PRL is around 580 meters and the total number of signal outputs provided equals almost 300. The entire PRL will be temperature stabilized (+/-0.1 deg C) and an inner-line gas pressure stabilization will be applied in order to assure synchronization accuracy. This contribution covers the concept of the PRL, technical assumptions, status of the design, status of installations and commissioning plans.