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Currently 26 RF stations are in operation at the European X-ray Free Electron Laser (XFEL) and all RF stations can deliver sufficient power to reach maximum gradients in the accelerating modules, limited only by cavity and coupler properties. It was demonstrated that by activating a dynamic frequency shift (DFS) of the RF drive signal, the requested klystron power can be reduced by up to 20%, keeping the gradient levels unchanged. Currently the high voltage (HV) pulse has a length of 1.7ms and the RF pulse a length of 1.42ms, out of which only 0.6ms can be used for beam acceleration. Currently, the RF pulse starts when the level of klystron HV reaches 99% of the nominal voltage. If one allows the RF pulse to start at the 80% level of the nominal voltage, then the RF pulse length can be increased. In this article we will present a proposal for increasing the XFEL RF pulse flattop length using phase and amplitude compensation during the rise and fall of the HV, as well as applying DFS when filling the cavities of the accelerator. The first demonstration of the proposed procedure with the 10MW multi-beam klystrons (MBK) at the klystron test stand and at the XFEL RF station A10.L3 will be presented as well. The described procedure can be used both to increase the duration of the RF flat top as well as to shorten the duration of the HV, which could lead to energy savings.

Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil 12th International Particle Accelerator Conference, IPAC'21, Campinas, Brazil, 24 May 2021 - 28 May 2021; JACoW Publishing, Geneva, Switzerland 3 pp. (2021). doi:10.18429/JACOW-IPAC2021-TUPAB302, For pump-probe and seeding experiments at free electron lasers, a femtosecond precise bunch arrival time stability is mandatory. To stabilize the arrival times a fast longitudinal intra bunch-train feedback (L-IBFB) using bunch arrival time monitors is applied. The electron bunch energy prior to a bunch compression chicane is modulated by superconducting radio frequency (SRF) cavities to compensate fast arrival time fluctuations of the subsequent bunches. A broadband normal conducting RF cavity was installed in front of the first bunch compression chicane at FLASH. The L-IBFB uses the normal conducting cavity for small but fast energy corrections together with the SRF cavities for larger and slower corrections. Current measurements show arrival time stabilities of the electron bunches towards 5 fs (rms) at the end of the linac, if the normal conducting cavity acts together with the SRF cavities in the L-IBFB system., Published by JACoW Publishing, Geneva, Switzerland

39th International Free-Electron Laser Conference, FEL19, Hamburg, Germany, 26 Aug 2019 - 30 Aug 2019; JACoW Publishing, Geneva, Switzerland 346-349 (2019). doi:10.18429/JACOW-FEL2019-WEP011, The longitudinal intra-train beam-based feedback has been recommissioned after major upgrades on the synchronization system of the FLASH facility. Those upgrades include: new bunch arrival time monitors (BAMs), the optical synchronization system accommodating the latest European XFEL design based on PM fibers, and installation of a small broadband normal conducting RF cavity. The cavity is located prior to the first bunch compressor at FLASH and allows energy modulation bunch-by-bunch (1 us spacing) on the per mille range. Through the energy dependent path length of the succeeding magnetic chicane the cavity is used for ultimate bunch arrival time corrections. Recently the RF cavity operated 1 kW pulsed solid-state amplifier was successfully commissioned. First tests have been carried out incorporating the fast cavity as actuator together with SRF stations for larger corrections in our intra-train beam-based feedback pushing now arrival time stabilities towards 5 fs (rms). The latest results and observed residual instabilities are presented., Published by JACoW Publishing, Geneva, Switzerland

This paper presents the solution, which helps in the simulation and verification of the implementation of the Digital Signal Processing (DSP) algorithms written in hardware description language (HDL). Many vendor tools such as Xilinx ISE/Vivado or Mentor Graphics ModelSim are using Tcl as an application programming interface. The main idea of the co-simulation is to use the Tcl TCP/IP socket, which is Tcl build in feature, as the interface to the simulation tool. Over this interface the simulation is driven by the external tool. The stimulus vectors as well as the model and verification are implemented in Python or MATLAB and the data with simulator is exchanged over dedicated protocol. The tool, which was called cosimtcp, was developed in Deutsches Elektronen-Synchrotron (DESY). The tool is a set of scripts that provide a set of functions. This tool has been successfully used to verify many DSP algorithms implemented in the FPGA chips of the Low Level Radio Frequency (LLRF) and synchronization systems of the European X-Ray Free Electron Laser (E-XFEL) accelerator. Cosimtcp is an open source available tool., Proceedings of the 17th International Conference on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2019, New York, NY, USA

The European X-Ray Free Electron Laser (E-XFEL) accelerator is a pulse machine. The typical time duration of a radio frequency (RF) pulse is about 1.3 ms. The RF power transmitted to the superconducting RF (SCRF) cavity as a set of successive pulses (10 Hz repetition rate), causes strong mechanical stresses inside the cavity. The mechanical deformations of the RF cavity are typically caused by the Lorentz force detuning (LFD). The cavity can be tuned to a 1.3 GHz resonance frequency during the RF pulse using fast piezo tuners. Since the E-XFEL will use around 800 cavities (each cavity with double piezos), a distributed architecture with multi-channel digital and analog control circuits seems to be essential. The most sought-after issue is high-voltage, high-current piezo driving circuit dedicated to multi-channel configuration. The driving electronics should allow a maximum piezo protection against any kind of failure. The careful automation of the piezo tuners control and its demonstration for the high gradient conditions a real challenge. The first demonstration of piezo controls applied for chosen RF stations of the E-XFEL linear accelerator (linac) are presented and obtained results are briefly discussed within this paper., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

In the paper we would like to present a new Micro Telecommunication Computing Architecture (MicroTCA) piezo driver (PZT4). The piezo driver module is capable of driving of 4 piezo actuators with high voltages up to 160 Vpp. It is also possible to measure cavity mechanical vibrations using 4 analog to digital converters (ADC) ported to the driver electronics. The new piezo driver can be supplied using internal 12 V payload power provided by the MicroTCA standard. For the applications that need more than 30 W of the input power, the external power supply module can be provided. In order to protect the piezo driver electronics against output short condition a dedicated supervision circuit is designed. The piezo driver module has been setup at Cryo Module Test Bench (CMTB) facility in Deutsches-Elektronen Synchrotron (DESY) as a part of the single cavity low-level radio frequency (LLRF) controls. The LLRF control system has been used to demonstrate the radio frequency (RF) field stabilization and cavity tuning capabilities for continuous (CW) and pulse modes of operation of 1.3 GHz superconducting resonant RF (SCRF) cavity. The preliminary results are demonstrated and briefly discussed., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

To perform experiments on the nanometer scale at high brilliant x-ray light sources, it is highly recommended to have the mechanical components of the experiment, like lenses, mirrors and samples, as stable as possible. Since these components need to move from nanometer up to millimeter range they cannot be stabilized by only using rigid structures. For that reason an active stabilization system with fast and precise sensors needs to be developed. Here a Laserinterferometer is used, which provides picometer resolution at several MHz sample rate. In this paper we will present a laboratory setup which consists of a 6-slot Micro Telecommunication Computing Architecture generation 4 (MTCA.4) crate with standard components such MicroTCA carrier hub (MCH), central processing unit (CPU), power supply (PS) and cooling unit (CU). The Interferometer application has been setup with Deutsches Elektronen-Synchrotron (DESY) advanced mezzanine card (DAMC-FMC20) data processing unit, DESY Field Programmable Gate Array (FPGA) mezzanine card (DFMC-UNIO) universal input and output extension and DESY rear transition module (DRTM-PZT4) piezo driver. The encoder signals given by the interferometer controller are processed within the FPGA and then forwarded to the piezo amplifier RTM-board. The signal processing application includes decoding the digital feedback signal, calculating the coordinate transform for specific experimental setups and closed-loop operation based on a proportional integral derivative (PID) controller. The first results of the laboratory setup are demonstrated and briefly discussed., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

In the past two decades, RF controls have improved by two orders in magnitude achieving meanwhile sub-10 fs phase stabilities and 10⁻⁴ amplitude precision. Advances are through improved field detection methods and massive usage of digital signal procession on very powerful field programmable gate arrays (FPGAs). The question rise, what can be achieved in the next 10 years? In this talk, a review is given of existing systems and strategies, current stability limitations of RF control system and new technologies with the potential to achieve attosecond resolutions., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

In the paper we would like to present Tesla SCRF 9-Cell cavity operated at CW regime with extremely high QL at gradients above 23 MV/m. The design hardware and firmware components as well as developed high level software procedures allows automatic procedure of cavity trip from low to high gradient operation. The microphonics as well as a pendoromotive effects are sensed, identify and applied for cavity detuning correction. The RF and piezo feedbacks performance are demonstrated and preliminary results are briefly discussed., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

9th International Particle Accelerator Conference, IPAC'18, Vancouver, Canada, 29 Apr 2018 - 4 May 2018, The European X-ray Free-Electron Laser (XFEL) at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany is a user facility providing ultrashort hard and soft X-ray flashes with a high brilliance. All LLRF stations of the injector, covering the normal conducting RF gun, A1 (8 1.3 GHz superconducting cavities (SCs)) and AH1 (8 3.9 GHz SCs), were successfully commissioned by the end of 2015. The commissioning of LLRF stations A2 to A23 (32 1.3 GHz SCs each) in the XFEL accelerator tunnel (XTL) was concluded in June 2017. SASE light was produced in SASE undulator section SA1 and delivered to the first users in September 2017, marking the beginning of regular user operation. The current state of the LLRF systems, the experience gained during operation and the performance achieved in terms of stability and energy reach are presented.

29th Linear Accelerator Conference, Beijing, China, 11 Sep 2018 - 21 Sep 2018; JACoW 3 pp. (2018)., Linear accelerator facilities driving a free-electron laser require femtosecond precision synchronization between external laser systems and the electron beam. Such high precision is required for pump-probe experiments and also for example for the electron bunch injection into a plasma bubble for laser plasma acceleration. An upgrade of the fast intra-train beam-based feedback system is planned at the Free-Electron Laser FLASH in Hamburg, Germany. This linear accelerator is based on superconducting (SRF) technology operating with pulse trains of maximum 1 MHz bunch repetition rate. Arrival time fluctuations of the electron beam are correctable by introducing small energy modulations prior to the magnetic bunch compressor. This contribution focuses on the design and the characterization of a normal-conducting RF (NRF) cavity with large bandwidth, mandatory to correct fast arrival time fluctuations. The cavity has recently been installed in the FLASH beamline. First measurements with the new cavity will be presented., Published by JACoW

29th Linear Accelerator Conference, LINAC18, Beijing, China, 17 Sep 2018 - 21 Sep 2018; JACoW 3 pp. (2018)., After its successful commissioning which took place during the first half of 2017, the European X-ray free electron laser is in now in regular operation delivering photons to users since September 2017. This paper presents an overview on the experience gathered during the first couple of years of operation. In particular, the focus is set on RF operation, maintenance activities, availability and typical failures. A first look on machine performance in terms of RF and beam stability, energy reach, radiation related investigations and microphonics studies will also be presented., Published by JACoW

The superconducting linear accelerator ELBE is operated in continuous wave operation (CW). The analogue LLRF system, used since 2001, is going to be replaced by a digital solution based on MTCA.4. The new system enables a higher flexibility, better performance and more advanced diagnostics. The contribution will show the performance of the system at ELBE, the hardware and the software structure. Further it will summarize the last steps to bring it into full user operation and give an outlook to the envisioned beam-based feedback system that will take advantage of the capabilities of the digital LLRF system., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

29th Linear Accelerator Conference, LINAC18, Beiing, China, 17 Sep 2018 - 21 Sep 2018; Geneva : JACoW 109-111 (2018)., At present 26 RF stations for European XFEL are inoperation. Each RF station consists of a HV modulatorlocated in a separate building on the DESY campus, up to1600 m long 10 kV HV cables that connect the modulatorand the HV pulse transformer located in the undergroundtunnel, 120kV, 3 m long HV cable connecting the HVpulse transformer and the connection module (CM) of thehorizontal multi-beam klystron (MBK). The klystron canproduce RF power up to 10 MW, at a RF frequency of 1.3GHz, 1.5 ms pulse length and 10 Hz repetition rate. TwoRF stations of the injector have already got about 24000hours of operation, RF stations of the XFEL bunchcompressor area have operated up to 13000 hours and theklystrons in the XFEL main linac already have about11000 hours of operation (Status August 2018). Toincrease the lifetime of the klystrons, we use a fastprotection system (KLM) that is based on the comparisonof the actual RF shape and the expected RF shape. In thecase of a difference exceeding a certain margin, forexample, in the case of RF breakdown in a klystron or RFbreakdown in a waveguide system (WGS), the KLMquickly, shorter than 800 ns, switches off the input RFsignal. Thus, it does prevent the vacuum level in theklystron worsen too much or it minimizes the RFovervoltage time at the output windows of the klystron incase of breakdown in WGS. In this article we will give asummary of the present klystron status including thenumbers of HV klystron gun and RF arcs in the klystrons., Published by JACoW, Geneva

29th Linear Accelerator Conference, LINAC 18, Beijing, China, 17 Sep 2018 - 21 Sep 2018; Geneva, Switzerland : JACoW 4 pp. (2018)., In the European XFEL, a maximum number of 2700 electron bunches per RF pulse with beam currents up to 4.5mA can be accelerated. Such large beam currents can cause a significant drop of the accelerating gradients, which results in large energy changes across the macro-pulse. But, the electron bunch energies should not deviate from the nominal energy to guarantee stable and reproducible generation of photon pulses for the European XFEL users. To overcome this issue, the Low Level RF system (LLRF) compensates in real-time the beam perturbation using a Beam Loading Compensation algorithm (BLC) minimizing the transient gradient variations. The algorithm takes the charge information obtained from beam diagnostic systems e.g. Beam Position Monitors (BPM) and information from the timing system. The BLC is a part of the LLRF controller implemented in the FPGA. The article presents the implementation of the algorithm in the FPGA and shows the results achieved with the BLC in the European XFEL., Published by JACoW, Geneva, Switzerland

8th International Particle Accelerator Conference, IPAC17, Copenhagen, Denmark, 15 May 2017 - 19 May 2017 ; Geneva : JACoW, 3963-3965(2017). doi:10.18429/JACoW-IPAC2017-THPAB105, 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 1.3 GHz Optical Reference Module (REFM-OPT) for FLASH and the European XFEL. The REFM-OPT will phase-stabilize 1.3 GHz 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., Published by JACoW, Geneva

The European X-ray Free-Electron Laser (XFEL) at Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany is a user facility under commissioning, providing ultrashort X-ray flashes with a high brilliance in the near future. All LLRF stations of the injector, covering the normal conducting RF gun, A1 (8 1.3 GHz superconducting cavities (SCs) and AH1 (8 3.9 GHz SCs), were successfully commissioned by the end of 2015. The injector was operated with beam transmission to the injector dump since then. After the conclusion of the construction work in the XFEL accelerator tunnel (XTL), the commissioning of 22 LLRF stations (A2 to A23) started with the beginning of 2017. Every station consists of a semi-distributed LLRF system controlling 32 1.3 GHz SCs. Stable operation with beam transport to the main dump (TLD) was achieved. The commissioning procedure applied, experience gained and performance reached are described., Proceedings of the 18th Int. Conf. on RF Superconductivity, SRF2017, Lanzhou, China

8th International Particle Accelerator Conference, IPAC´17, Copenhagen, Denmark, 14 May 2017 - 19 May 2017 ; 3638-3641(2017)., The installation of the European X-ray Free Electron Laser (XFEL) is finished, leaving place for its commissioning phase. This contribution summarizes the low-level radiofrequency (LLRF) commissioning with a special emphasis on the development of automation tools to support the commissioning of such a large scale accelerator. First results ofthe LLRF commissioning in the main linac are also given.

Optical synchronization systems are already in regular operation in many FELs, or they will eventually be implemented in the future. In FLASH and the European XFEL, phase-stable optical reference signals are provided by a pulsed optical synchronization system in order to achieve low timing jitter FEL performance. The generation of phase-stable RF signals from a pulsed optical synchronization system is still a field of active research. The optical reference module (REFM-OPT), designed at DESY for operation in both FELs, employs a laser-to-RF phase detector, based on an integrated Mach-Zehnder interferometer. The phase drift of the 1.3 GHz RF reference signals with respect to the optical pulses is measured and actively corrected within the REFM-OPT at multiple locations in the accelerator. Therefore the REFM-OPT provides phase stable 1.3 GHz RF reference signals at these locations. The short-term and long-term performance in the accelerator tunnel of the European XFEL is presented and carefully reviewed., Proceedings of the 38th Int. Free Electron Laser Conf., FEL2017, Santa Fe, NM, USA

In the paper the MicroTCA.4 based optical frontend readout (OFR) electronics and its applications for beam arrival time monitor (BAM) and fast beam based feed-back (BBF) is presented. The idea is to have a possibility to monitor the modulation density of the optical laser pulses by the electron bunches and apply this information for the BBF. The OFR composed of double width fast mezzanine card (FMC) and advanced mezzanine card (AMC) based FMC carrier. The FMC module consists of three optical channel inputs (data and clock), two optical channel outputs (beam arrival time), 250 MSPS ADCs, clock generator module (CGM) with integrated 2.8 GHz voltage control oscillator (VCO). The optical signals are detected with 800 MHz InGaAs photodiodes, conditioned using 2 GHz current-feedback amplifiers, filtered by 3.3 GHz differential amplifiers and next direct sampled with 16-bit 900 MHz of analog bandwidth ADCs. The CGM is used to provide clock outputs for the ADCs and for the FMC carrier with additive output jitter of less than 300 fs rms. The BAM application has been implemented using Virtex 5 FPGA and measured with its performance at Free Electron LASer in Hamburg (FLASH) facility., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

The 20th IEEE-NPSS Real Time Conference, RT2016, Padua, Italy, 5 Jun 2016 - 10 Jun 2016 ; (2016)., The driving engine of the superconducting accelerator of the European X-ray Free-Electron Laser (XFEL) are 27 Radio Frequency (RF) stations. Each of an underground RF station consists from multi-beam horizontal klystron which can provide up to 10MW of power at 1.3GHz. Klystrons are sensitive devices with limited lifetime and high mean time between failures. In the real operation the lifetime of the tube can be thoroughly reduced by failures. To minimize the influence of service conditions to the klystrons lifetime the special fast protection system named as Klystron Lifetime Management System (KLM) has been developed. The main task of this system is to detect all events which can destroy the tube as quickly as possible and switch off driving signal. Detection of events is based on comparison of model of high power RF amplifier with real signals. All algorithms are implemented in Field Programmable Gate Array (FPGA). For the XFEL implementation of KLM is based on the standard Low Level RF (LLRF) Mi-cro TCA technology (MTCA.4 or xTCA).This article focus on the klystron model estimation for protection system and implementation of KLM in FPGA on MTCA.4 architecture.

For the European XFEL project, horizontal multi-beam klystrons (MBK) which produce RF power up to 10 MW, at an RF frequency of 1.3 GHz, 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. All MBKs have been manufactured by two companies, 22 tubes from Thales Electron Devices and 7 tubes from Toshiba Electron Tubes & Devices. In this article we will give a summary of the tube testing, conditioning and installation in the underground linear accelerator tunnel., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

6th International Particle Accelerator Conference, IPAC 2015, Richmond, VA, USA, 3 May 2015 - 8 May 2015 ; 200-202(2015)., The European X-ray free electron laser requires a high-precision control of accelerating fields to ensure a stable photon generation. Its low level radio frequency system, based on the MicroTCA.4 standard, detects the probe, forward and reflected signals for each cavity. While the probe signal is used to control the accelerating fields, a combination of the forward and reflected signals can be used to compute a virtual probe, whose accuracy is comparable to the directly sampled probe. This requires the removal of cross-coupling effects between the forward and reflected signals. This paper presents the precise generation of a virtual probe using an extended method of least squares. The virtual probe can then be used for precise field control in case the probe signal is missing or corrupted. It can also be used to detect any deviation from the nominal probe profile.

During the last half year, the MicroTCA.4 based single cavity LLRF control system was installed and commissioned at several normal conducting facilities at DESY (FLASH RF gun, REGAE, PITZ RF gun, and XFEL RF gun). First tests during the last year show promising results in optimizing the system for high speed digital LLRF feedbacks, i.e. reducing system latency, increasing the internal controller processing speed, testing new control schemes, and optimizing controller parameters. In this contribution we will present results and gained experience from the commissioning phase and the first time period of real operation., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

Many of the modules in specific hardware architectures use the same or similar communication interfaces and IO connectors. MicroTCA (MTCA.4) is one example of such a case. All boards: communicate with the central processing unit (CPU) over PCI Express (PCIe), send data to each other using Multi-Gigabit Transceivers (MGT), use the same backplane resources and have the same Zone3 IO or FPGA mezzanine card (FMC) connectors. All those interfaces are connected and implemented in Field Programmable Gate Array (FPGA) chips. It makes possible to separate the interface logic from the application logic. This structure allows to reuse already done firmware for one application and to create new application on the same module. Also, already developed code can be reused in new boards as a library. Proper structure allows the code to be reused and makes it easy to create new firmware. This paper will present structures of firmware framework and scripting ideas to speed up firmware development for MTCA.4 architecture. European XFEL control systems firmware, which uses the described framework, will be presented as example., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia

In order to validate the cavity package concept before the module preparation for the European XFEL Injector, one 3.9 GHz cavity, complete with magnetic shielding, power coupler and frequency tuner was tested in a specially designed single cavity cryomodule in one of the caves of the DESY Accelerator Module Test Facility (AMTF). The cavity was tested in high power pulsed operation up to the quench limit of 24 MV/m, above the vertical test qualifications and all subsystems under test (coupler, tuner, waveguide tuners, LLRF system) were qualified to design performances.

Stable and reproducible generation of a photon beam at Free Electron Lasers (FELs) necessitates a low energy spread of the electron beam. A low level radio frequency (LLRF) control system stabilizes the RF field inside accelerating modules. An electron beam passing through the cavity induces a drop in the actual stored field proportional to the charge, the cavity shunt impedance, and the bunch repetition rate. The feedback loop compensates for the perturbation after the accelerating gradient drops. Due to the digital loop delay and limited bandwidth of the closed loop system, this disturbance induces control errors which can increase beam energy spread. An open-loop controller uses information obtained from the beam diagnostic systems accounting in real-time for fluctuations of the beam current. This paper describes the bunch charge detection scheme, its implementation, as well as results of the tests performed on the ELBE (Electron Linac for beams with high Brilliance and low Emittance) radiation source at the HZDR (Helmholtz-Zentrum Dresden-Rossendorf) facility., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia

The Free-Electron Laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron (DESY), Hamburg Germany is a user facility providing ultra-short, femtosecond laser pulses up to the soft X-ray wavelength range. For the precise regulation of the radio frequency (RF) fields within the 60 superconducting cavities, which are organized in 5 RF stations, digital low level RF (LLRF) control systems based on the MTCA.4 standard were implemented in 2013. Until now experiences with failures potentially due to radiation, overheating, and ageing as well as with the general operation of the control systems have been gained. These have a direct impact on the operation and on the performance of FLASH and will allow future improvements. The lessons learned are not only important for FLASH but also in the scope of European X-ray Free-Electron Laser (X-FEL), which will be operated with the same LLRF control system., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Accelerators are affected by the cavities detuning variation caused by external mechanical disturbances (microphonics). The paper presents microphonics estimation and prediction methods applicable for superconducting accelerators operating in pulsed mode. A mathematical model is built using the estimates of detuning during previous RF pulses. The model can be used for predictions of disturbances for the future time step and setup of the fast tuners accordingly. The proposed method was successfully verified with measurements conducted at the FLASH linac., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

The Low level RF system for the European XFEL is controlling the accelerating RF fields in order to meet the specifications of the electron bunch parameters. A hardware platform based on the MicroTCA.4 standard has been chosen, to realize a reliable, remotely maintainable and high performing integrated system. Fast data transfer and processing is done by field programmable gate arrays (FPGA) within the crate, controlled by a CPU via PCIe communication. In addition to the MTCA system, the LLRF comprises external supporting modules also requiring control and monitoring software. In this paper the LLRF system high level software used in E-XFEL is presented. It is implemented as a semi-distributed architecture of front end server instances in combination with direct FPGA communication using fast optical links. Miscellaneous server tasks have to be executed, e.g. fast data acquisition and distribution, adaptation algorithms and updating controller parameters. Furthermore the inter-server data communication and integration within the control system environment as well as the interface to other subsystems are described., Proceedings of the 15th Int. Conf. on Accelerator and Large Experimental Physics Control Systems, ICALEPCS2015, Melbourne, Australia

The 3.9 GHz cryomodule and RF system for the XFEL Injector is being assembled and delivered to the underground building in summer 2015, for the injector commissioning in Fall 2015. This contribution outlines the status of the activity and reports the preparation stages of the technical commissioning of the system., Proceedings of the 17th International Conference on RF Superconductivity, SRF2015, Whistler, BC, Canada

The 3.9 GHz cryomodule and RF system for the XFEL Injector is being assembled and delivered to the underground building in summer 2015, for the injector commissioning in Fall 2015. This contribution outlines the status of the activity and reports the preparation stages of the technical commissioning of the system.

The European x-ray free electron laser (XFEL) is based on a 17.5 GeV super conducting pulsed linac and is scheduled to deliver its first beam in 2016. The first component of its accelerator chain, the RF gun, was installed in fall of 2013 and its commissioning is underway. This contribution gives an update on the low level radio frequency (LLRF) system development and installation for the XFEL. In particular, the installation, performance and conditioning results of the RF gun are presented. The subsequent steps toward LLRF components mass-production, testing and installation for the XFEL linac are also explained., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

At present more than half of 27 of 10 MW horizontal multi-beam klystrons (MBK) manufactured by two companies for the European XFEL project have been delivered to DESY. After delivery each klystron is connected to the connection module (CM), a HV oil tank with integrated HV connector, voltage and current monitors and a coaxial filament transformer, tested on the test stand and, if necessary conditioned. After this the klystrons are ready for installation in the underground linear accelerator tunnel. Two MBKs are already installed at the injector area of the XFEL. For the European XFEL project MBKs which can produce RF power of 10 MW, at RF frequency of 1.3 GHz, 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. During the incoming test the most important parameters of the MBK such as bandwidth, filament power, perveance, gain at different cathode voltage, phase stability and sensitivity to the solenoids current setting are measured and documented. In this paper we will give an overview of the test procedure, summarize the current test results and give a comparison of the most important parameters for several tubes.

The Free Electron Laser in Hamburg (FLASH) is the first linac which is equipped with a MTCA.4 based low level RF control system. Precise regulation of RF fields is essential for stable and and reproducible photon generation. Flash benefits from the performance increase using the new developments like, accurate and precise field detection devices. Further enourmous increase of processing capabilities allow for more sophisticated controller applications which better the overall performance of the regulation., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

At present more than half of 27 of 10 MW horizontal multi-beam klystrons (MBK) manufactured by two companies for the European XFEL project have been delivered to DESY. After delivery each klystron is connected to the connection module (CM), a HV oil tank with integrated HV connector, voltage and current monitors and a coaxial filament transformer, tested on the test stand and, if necessary conditioned. After this theklystrons are ready for installation in the underground linear accelerator tunnel. Two MBKs are already installed at the injector area of the XFEL. For the European XFEL project MBKs which can produce RF power of 10 MW, at RF frequency of 1.3 GHz, 1.5 ms pulse length and 10 Hz repetition rate, were chosen as RF power sources. During the incoming test the most important parameters of the MBK such as bandwidth, filament power, perveance, gain at different cathode voltage, phase stability and sensitivity to the solenoids current setting are measured and documented. In this paper we will give an overview of the test procedure, summarize the current test results and give a comparison of the most important parameters for several tubes.

Optical laser have become an integral part of free-electron laser facilities for the purposes of electron bunch generation, external seeding, diagnostics and pump-probe experiments. The ultra-short electron bunches demand a high timing stability and precision synchronization of the optical lasers. In this paper, we present the proof-of-principle for a laser locking application implemented on a MTCA.4 platform. The system design relies on existing MTCA.4 compliant off-the-shelf modules that are available on the market or have been developed for other applications within the particle accelerator community. Besides performance and cost, we also tried to minimize the number of out-of-crate components. Preliminary measurements of laser locking at the FLASH and REGAE particle accelerators are presented, and an outlook for further system development in the area of laser-to-RF synchronization is given.