Pawel Predki

Prototype real-time ATCA-based LLRF control system

The linear accelerators employed to drive Free Electron Lasers (FELs), such as the X-ray Free Electron Laser (XFEL) currently being built in Hamburg, require sophisticated control systems. The Low Level Radio Frequency (LLRF) control system should stabilize the phase and amplitude of the electromagnetic fields in accelerating modules with tolerances below 0.02% for amplitude and 0.01 degree for phase to produce ultra-stable electron beam that meets the conditions required for Self-Amplified Spontaneous Emission (SASE). The LLRF control system of a 32-cavity accelerating module of the XFEL accelerator requires acquisition of more than 100 analogue signals sampled with frequency around 100 MHz. Data processing in a real-time loop should complete within a few hundred nanoseconds. Moreover, the LLRF control system should be reliable, upgradeable and serviceable. The Advanced Telecommunications Computing Architecture (ATCA) standard, developed for telecommunication applications, can fulfil all of these requirements. The paper presents the architecture of a prototype LLRF control system developed for the XFEL accelerator. The control system composed of ATCA carrier boards with Rear Transition Modules (RTM) is able to supervise 32 cavities. The crucial submodules, like DAQ, Vector Modulator or Timing Module, are designed according to the AMC specification. The paper discusses results of the LLRF control system tests that were performed at the FLASH accelerator (DESY, Hamburg) during machine studies.

Intelligent Platform Management Controller for Low Level RF control system ATCA Carrier Board

High availability and reliability are among the most desirable features of control systems in modern high-energy physics (HEP) and other big-scale scientific experiments. One of the recent developments that has influenced this field has been the emergence of the Advanced Telecommunications Computing Architecture (ATCA). Designed for the telecommunications industry, it has been successfully applied in other domains, such as accelerator control systems. A good example is the application of ATCA standard for the design of the low-level RF (LLRF) control system for the X-Ray Free Electron Laser (XFEL) being developed in Deutsches Elektronen Synchrotron (DESY). Reliability and availability requirements for such a facility play a crucial role among other parameters. Thus, the ATCA standard, with five-nines availability, is considered to be one of the best candidates for this system. This paper focuses on the central-management unit of every ATCA board, namely, the intelligent platform-management controller (IPMC), developed for the LLRF ATCA carrier board. It is also argued that it is possible to create a fully functional IPMC using base specifications which is only a more economical solution than acquiring such products from ATCA vendors. This work supports the concept of an open-source community solution under the xTCA for physics collaboration dealing with IPMC/MMC development and wishes to contribute to it. The IPMC solution presented here is mainly hardware independent as proper code organization allowed to separate low-level device drivers and high-level application logic dealing with the ATCA standard, which makes it portable for new carrier-board designs. It also follows the latest trends in xTCA development introduced by the xTCA for Physics initiative. A firmware upgrade of programmable devices (field-programmable gate arrays and digital signal processors) has been proposed. Currently, this is not included in the standard. However, this functionality is needed in HEP applications by using xTCA and is useful in these cases.

Real-time IPMI protocol analyzer

The Advanced Telecommunications Computing Architecture (ATCA) is a modern platform, which gains popularity, not only in telecommunication applications, but also in others fields like High Energy Physics (HEP) experiments. Computing systems based on ATCA provide high performance and efficiency and are characterized by significant reliability, availability and serviceability. ATCA offers these features because of an integrated management system realized by the Intelligent Platform Management Interface (IPMI) implemented on dedicated Intelligent Platform Management Controller (IPMC). IPMC is required on each ATCA board to fulfill the ATCA standard and is responsible for many vital procedures performed to support proper operation of ATCA system. It covers, among others, activation and deactivations of modules, monitoring of actual parameters or controlling fans. The commercially available IPMI implementations are expensive and often not suited to demands of specific ATCA applications and available hardware. Thus, many research centers and commercial companies decide to develop their own version of IPMC software. Despite precise IPMI specification of communication requests and responses, these implementations are often incompatible with each other, which leads to incorrect in-system behavior of devices equipped with IPMCs from various vendors. ATCA specifies the I2C protocol as a physical layer of IPMI. There are many devices able to monitor the I2C bus such as logic analyzers or specialized oscilloscopes. However, there is no available equipment capable of debugging IPMI as a higher level protocol. The article compares available methods of IPMI debugging and describes a custom made device prepared to monitor in realtime up to eight IPMI lines and analyze the IPMI protocol. Accessibility of this kind of equipment allows to discover errors and find the reasons of faulty behavior of the IPMC under development, greatly reduce the time to market factor and decrease costs of ATCA system development.

Design and Operation of the Integrated 1.3 GHz Optical Reference Module with Femtosecond Precision

In modern Free-Electron Lasers like FLASH or the European XFEL, the short and long-term stability of RF reference signals gains in importance. The requirements are driven by the demand for short FEL pulses and low-jitter FEL operation. In previous publications, a novel, integrated Mach-Zehnder Interferometer based scheme for a phase detector between the optical and the electrical domain was presented and evaluated. This Laser-to-RF phase detector is the key component of the integrated 1.3GHz Optical Reference Module (REFM-OPT) for FLASH and the European XFEL. The REFMOPT will phase-stabilize 1.3GHz RF reference signals to the pulsed optical synchronization systems in these accelerators. Design choices in the final hardware configuration are presented together with measurement results and a performance evaluation from the first operation period in the European XFEL.

GUI application for ATCA-based LLRF Carrier Board management

The Advanced Telecommunications Computing Architecture (ATCA) standard describes an efficient and powerful platform, implementation of which was adopted to be used as a base for control systems in high energy physics. The ATCA platform is considered to be applied for the X-ray Free Electron Laser (X-FEL), being built at Deutsches Electronen-Synchrotron (DESY) in Hamburg, Germany. The Low Level Radio Frequency (LLRF) control system is composed of a few ATCA Carrier Boards. Carrier Board hosts Intelligent Platform Management Controller (IPMC), which is developed in compliance with the PICMG specifications. IPMC is responsible for management and monitoring of sub-modules installed on Carrier Boards and pluggable Advanced Mezzanine Card (AMC) modules.