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The LLRF (Low-Level Radio Frequency) system optimizes energy transfer from the superconducting resonator to the accelerating beam. At ESS, one LLRF system regulates a single cavity. This digital system’s HW platform is the MTCA.4 standard. The system has been co-designed by ESS, Lund University, and the PEG (Polish Electronic Group) consortium. The PEG is also responsible for the system components design, evaluation, and production (like Local Oscillator Rear transition module, piezo tuner driver RTM, RTM carrier board, and others). The PEG delivers a HW/SW cavity simulator, an LLRF system test-stand, and provides necessary integration and installation services required for complete system preparation for the linac commissioning and operation phase. The paper summarizes the PEG work on the development and preparation of the LLRF systems for the ESS elliptical structures. The efforts concerning hardware and software components prototyping and evaluation are discussed. Moreover, we present the current status of the project, including components mass production, integration, and installation work., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The Proton Improvement Plan-II (PIP-II) is a planned proton facility at Fermilab. The short- and long-term beam energy stabilization requirements necessitate using a high-quality Master Oscillator (MO). The consecutive sections of the Linac will operate at 162.5, 325, and 650 MHz. The phase relations between reference signals of harmonic frequencies should be kept constant, and the phase noise should be correlated in a wide bandwidth. The possibility of simultaneously meeting both requirements using popular frequency synthesis schemes is discussed. The ultra-low noise floor of the fundamental source is challenging for other devices in the phase reference distribution system. Therefore, the sensitivity to operating conditions, including impedance matching, input power level, and power supply voltage, must be considered. This paper presents a preliminary performance test of critical components selected for the PIP-II Master Oscillator system performed using a state-of-the-art phase noise analyzer., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

This paper describes the specifications, architecture, and measurements’ results of the MTCA-compliant Local Oscillator (LO) Rear Transition Module (RTM) board providing low phase noise clock and heterodyne signals for the 704.42 MHz Low Level Radio Frequency (LLRF) control system at the European Spallation Source (ESS). The clock generation and LO synthesis circuits are based on the module presented at ICALEPCS 2017. The conditioning circuits for the input and output signals must simultaneously achieve the desired impedance matching, spectral purity, output power as well as the phase noise requirements. The reference conditioning circuit presents an additional challenge due to input power range being significantly wider than the output range. The circuits monitoring the power levels of critical signals and voltages of supply rails for remote diagnostics as well as the programmable logic devices used to set the operating parameters via Zone3 connector are described., Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA

Institute of Electronic Systems (ISE) at Warsaw University of Technology designs, builds and installs control and synchronization systems for several accelerator facilities. In recent years ISE together with the Deutsches Elektronen-Synchrotron (DESY) team created the RF synchronization system for the European XFEL in Hamburg. ISE is a key partner in several other projects for DESY flagship facilities. The group participated in development of the MTCA.4 standard and designed a family of components for the MTCA.4-based LLRF control system. Currently, ISE contributes to the development of the Master Oscillators for XFEL and FLASH, and phase reference distribution system for SINBAD. Since 2016 ISE is an in-kind partner for the European Spallation Source (ESS), working on the phase reference line for the ESS linac, components for 704.42 MHz LLRF control system, including a MTCA.4-based LO signal generation module and the Cavity Simulator. In 2019 ISE became one of the co-founders of the Polish Free-Electron Laser (PolFel) located in the National Centre for Nuclear Research in Świerk. The overview of the recent projects for large physics experiments ongoing at ISE is presented., Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA

The particle longitudinal dynamics is affected by errors on the phase and amplitude of the electro-magnetic field in each cavity that cause emittance growth, beam degradation and losses. One of the causes of the phase error is the change of the ambient temperature in the LINAC tunnel, in the stub and in the klystron gallery that induces a phase drift of the signal travelling through the cables and radio frequency components. The field flatness error of each multiple cell cavity is caused by volume perturbation, cell to cell coupling, tuner penetration, etc.. In this paper it is studied the influences of these two types of errors on the beam dynamics and it is determined their tolerances such that the beam quality is kept within acceptable limits., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

This paper describes the requirements, architecture, and measurements results of the local oscillator (LO) board prototype. The design will provide low phase noise clock and heterodyne signals for the 704.42 MHz Cavity Simulator for the European Spallation Source. A field detection has critical influence on the simulation's performance and its quality depends on the quality of the two aforementioned signals. The clock frequency is a subharmonic of the reference frequency and choice of the frequency divider generating the clock signals is discussed. The performance of selected dividers was compared. The LO frequency must be synthesized and frequency synthesis schemes are investigated. Critical components used in the direct analog scheme are identified and their selection criteria were given., Proceedings of the 16th Int. Conf. on Accelerator and Large Experimental Control Systems, ICALEPCS2017, Barcelona, Spain

Hardware access often brings implementation details into a control application, which are subsequently published to the control system. Experience at DESY has shown that it is beneficial for the software quality to use a high level of abstraction from the beginning of a project. Some hardware registers for instance can immediately be treated as process variables if an appropriate library is taking care of most of the error handling. Other parts of the hardware need an additional layer to match the abstraction level of the application. Like this development cycles can be shortened and the code is easier to read and maintain because the logic focuses on what is done, not how it is done. We present the abstraction concept we are using, which is not only unifying the access to hardware but also how process variables are published via the control system middleware., Proceedings of the 16th Int. Conf. on Accelerator and Large Experimental Control Systems, ICALEPCS2017, Barcelona, Spain

At the European Spallation Source it is foreseen to use around 120 superconducting cavities operating at 704.42 MHz. Each cavity will require an individual LLRF control system, that needs to be tested before the installation inside the accelerator. Testing of all systems using the real superconducting cavities would be very expensive and in case of a failure can lead to serious damages. To lower the testing cost and avoid potential risks it is planned to design and build a device that simulates the behavior of a superconducting cavity. The cavity simulator will utilize fast data converters equipped with an RF front-end and a digital signal processing unit based on a high performance FPGA. In this paper conceptual design of hardware and firmware will be presented., Proceedings of the 16th Int. Conf. on Accelerator and Large Experimental Control Systems, ICALEPCS2017, Barcelona, Spain

21st IEEE Real Time Conference, RT2018, Colonial Williamsburg, USA, 9 Jun 2018 - 15 Jun 2018; 18 pp. (2018)., Many modern large-scale facilities, like European X-ray Free Electron Laser (E-XFEL), require precise synchronisation, often down to femtosecond level. Even a very short interruption or an excessive glitch in the reference signal might break the precise time relations between subsystems. In such event, a time-consuming resynchronization process is required that renders the facility not available for the users until it is completed. Therefore, such events are highly undesirable.In this paper, we present an autonomous redundancy solution for the European-XFEL's master oscillator that will guarantee a continuous delivery of the high-quality reference signal even in case of most of the potential failures. The concept and implementation are presented, as well as results from testing in the laboratory environment.