SURVEY OF COMMUNICATION LINKS FOR ATCA IN PHYSICS

Modern machines used in high energy physics require sophisticated and complex control systems. The complex systems are usually built as distributed systems. Therefore, the connectivity and communication links between distributed subsystems play a crucial role in the control system. The Advanced TelecommunicationComputingArchitecture (ATCA) and Advanced Mezzanine Card (AMC) standards have attracted the attention of physics community because they offer various types of data communication channels with high bandwidth, redundancy, high reliability and availability. The standards allow using different types of communication interfaces like PCIe, Gigabit Ethernet, RapidIO. In real-time systems the data transmission latency is also important. The acquisition of real-time data from hundreds of analogue channels is required for the Low Level Radio Frequency (LLRF) controller of XFEL (X-ray Free Electron Laser) accelerator. The paper presents survey of the communication interfaces of the LLRF controller for XFEL. The discussion includes the properties of interfaces provided by ATCA and AMC standards and summarizes requirements for the data links and protocols required by LLRF controller

Interfaces and Communication Protocols in ATCA-Based LLRF Control Systems.

Linear accelerators driving Free Electron Lasers (FELs), such as the Free Electron Laser in Hamburg (FLASH) or the X-ray Free Electron Laser (XFEL), require sophisticated Low Level Radio Frequency (LLRF) control systems. The controller of the LLRF system should stabilize the phase and amplitude of the field in accelerating modules below 0.02% of the amplitude and 0.01 degree for phase tolerances to produce an ultra stable electron beam that meets the required conditions for Self-Amplified Spontaneous Emission (SASE). Since the LLRF system for the XFEL must be in operation for the next 20 years, it should be reliable, reproducible and upgradeable. Having in mind all requirements of the LLRF control system, the Advanced Telecommunications Computing Architecture (ATCA) has been chosen to build a prototype of the LLRF system for the FLASH accelerator that is able to supervise 32 cavities of one RF station. The LLRF controller takes advantage of features offered by the ATCA standard. The LLRF system consists of a few ATCA carrier blades, Rear Transition Modules (RTM) and several Advanced Mezzanine Cards (AMCs) that provide all necessary digital and analog hardware components. The distributed hardware of the LLRF system requires a number of communication links that should provide different latencies, bandwidths and protocols. The paper presents the general view of the ATCA-based LLRF system, discusses requirements and proposes an application for various interfaces and protocols in the distributed LLRF control system