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Optica 7(6), 716 - (2020). doi:10.1364/OPTICA.396728, A critical challenge of pump-probe experiments with x-ray free-electron lasers (XFELs) is accurate synchronization of x-ray and optical pulses. At the European XFEL we observed megahertz rate timing jitter of 24.0±12.4fs., Published by OSA, Washington, DC

Optics letters 44(7), 1650 - 1653 (2019). doi:10.1364/OL.44.001650, Intense, ultrashort, and high-repetition-rate X-ray pulses, combined with a femtosecond optical laser, allow pump-probe experiments with fast data acquisition and femtosecond time resolution. However, the relative timing of the X-ray pulses and the optical laser pulses can be controlled only to a level of the intrinsic error of the instrument which, without characterization, limits the time resolution of experiments. This limitation inevitably calls for a precise determination of the relative arrival time, which can be used after measurement for sorting and tagging the experimental data to a much finer resolution than it can be controlled to. The observed root-mean-square timing jitter between the X-ray and the optical laser at the SPB/SFX instrument at European XFEL was 308 fs. This first measurement of timing jitter at the European XFEL provides an important step in realizing ultrafast experiments at this novel X-ray source. A method for determining the change in the complex refractive index of samples is also presented., Published by OSA, Washington, DC

We present the main features of the final prototype of a pulsed optical laser, developed for pump-probe and other experiments in conjunction with the femtosecond x-ray beams at the European X-ray free-electron laser facility. Adapted to the temporal x-ray emission pattern of the facility, the laser provides 10 Hz bursts of up to 600 µs duration with intra-burst pulse frequencies as high as 4.5 MHz. In this mode, we have generated pulses as short as 12 fs at 350 W average power during the burst and with beam qualities close to the diffraction limit. This is, to the best of our knowledge, the highest power to date of a few-cycle laser operating at a center wavelength of 800 nm. Important for experimental flexibility, the laser can be configured in various unique ways, enabling, e.g., energy scaling to >3 mJ per pulse through a frequency change down to 100 kHz and the generation of nearly transform limited pulses between 12 fs and 300 fs. In addition to the 800 nm femtosecond beam line, a synchronized long pulse (0.8 ps or 400 ps) 1030 nm beam can be utilized, offering up to 4 kW burst average power, i.e. up to 40 mJ per pulse at 100 kHz. Efficient nonlinear wavelength conversion and tuning through intrinsic and external means further enhance the capabilities of the laser.

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 field 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 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 real-time loop should complete within a few hundreds of nanoseconds. Moreover, the LLRF control system should be reliable, upgradable and serviceable. The Advanced Telecommunications Computing Architecture (ATCA) standard, developed for telecommunication applications, can fulfil all of the above mentioned 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 AMC specification. The paper discusses results of the LLRF control system tests that were performed at the FLASH accelerator (DESY, Hamburg) during machine studies.

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 ATC A-based LLRF system, discusses requirements and proposes an application for various interfaces and protocols in the distributed LLRF control system.

To transport low-noise Radio Frequency (RF) signals within a MicroTCA.4 Crate a new RTM backplane is invented as an optional extension to the 9U crate standard. The RTM backplane is equipped with links for high precision RF and Clock signals for the µRTM, therefore it is also called an RFBackplane. In combination with this backplane new extended RTMs (eRTM) and RTM Power Modules (RTM-PM) can be operated. Up to four 6 HP wide eRTMs can be installed behind the front Power Modules and the MCH Modules. The RTMPMs deliver managed low-noise separated analog bipolar power (+VV, -VV) for the RTMs and unipolar power for the eRTMs. This paper covers one of the eRTMs which is a Backplane Management module for the rear side (MCH-RTM-BM) designed to manage these new features. The MCH-RTM-BM will manage the RTM backplane connectivity for up to 12 µRTMs, 3 eRTMs and 2 RTM-PMs. For this purpose the MCH-RTM-BM is working together with the already existing NAT-MCH-PHYS. In addition the MCH-RTM-BM is connected to the eRTMs via LVDS links. These links can be user defined and are managed with a User Logic on the Backplane Management Module. This User Logic consists of a microcontroller with an FPGA.

ATCA/μTCA platforms are attractive because of the modern serial link architecture, high availability features and many packaging options. Less-demanding availability applications can be met economically by scaling back speed and redundancy. The ATCA specification was originally targeted for the Telecom industry but has gained recently a much wider user audience. The purpose of this paper is to report on present hardware and software R&D efforts where ATCA and μTCA are planned, already being used or in development using selected examples for accelerator and detectors in the Physics community. It will present also the status of a proposal for physics extensions to ATCA/μTCA specifications to promote inter-operability of laboratory and industry designs for physics.

The Advanced Telecommunications Computing Architecture (ATCA) and Micro Telecommunications Computing Architecture (μTCA) standards, collectively known as xTCA, provide a flexible and scalable infrastructure for designing complex control and data acquisition systems. The xTCA standards are becoming more and more popular in physics applications. Programmable devices, such as Field Programmable Gate Arrays (FPGAs), conventional and Digital Signal Processors (DSPs) are present in Advanced Mezzanine Card (AMC) modules and ATCA blades used in the xTCA crates. Those devices typically boot from non-volatile memories available on the modules. This paper deals with an universal framework and set of tools for upgrading firmware in such devices in xTCA systems. The proposed framework uses a fat pipe region interface of backplane for the firmware data transmission and the Intelligent Platform Management Interface (IPMI) standard for PROM memory management and the control of the upgrade procedure. This is the world's first attempt to implement the firmware upgrade in system not using the JTAG Switch Module (JSM).

The measurements of superconducting cavity parameters before module assembly stage are very important, because they allow to evaluate critical properties (resonant frequency, quality factor of accelerating mods) of individual resonating cavities. Such measurements are performed in Vertical Test Stand facilities. One of such setups is Vertical Test Stand II (VTS II) at DESY. It is used for conditioning and characterization of cavities for FEL (Free Electron Laser) experiments (especially for FLASH and European XFEL). In the previous set-up cavities in VTS II were operated in Continuous Wave mode using analog control system. The core of the system was analog Phase Lock Loop used to lock phases of incident wave and transmitted wave. All measurements were done using external equipment such as oscilloscopes, spectrum network analyzers, etc. The main disadvantage of such system was lack of flexibility - each small modification required precise system tuning, no new functionality could be added and automation of measurements was hard to achieve. The paper presents new solution of the control system for VTS II based on digital hardware. It allows to overcome most of disadvantages of previous analog system. All measurements and control functions are integrated on a single (FPGA based) computation board, which is fully integrated with external control system. The usage of such system offers functionality such as long term data acquisition (due to Continuous Wave operation of the cavity), special modes of operation (like Self Excited Loop or Digital PLL - due to low bandwidth of measured resonator) and possibility of measurement process automation. Additionally developed user interfaces allow remote access to the system parameters and flexible configuration. The paper discusses each sub-system, presents measurement results and overall system performance evaluation together with some views for future functionality development.

The Low Level RF (LLRF) control system of the Free Electron Laser in Hamburg (FLASH) is currently based on the Versa Module EuroCard (VME) standard. However, the application of Advanced Telecommunications Computing Architecture (ATCA) platform, as an alternative to the above mentioned standard, is taken into consideration. ATCA offers most of all improved reliability, because of the integrated management system which controls crucial parameters of the whole platform and provides the operator with control and diagnostics over the system from an external personal computer. Furthermore, implementation of AdvancedTCA architecture results in significant system operability enhancement, due to instant detection of a faulty module and Hot-Swap functionality that enables a swift replacement of the module, without disrupting the whole system. The platform management is under control of the Intelligent Platform Management Interface (IPMI). The paper presents the IPMI software for the Intelligent Platform Management Controller (IPMC) on a prototype Carrier Board. The software covers most of the functionality, defined by AdvancedTCA and IPMI ver. 1.5 standards, including inter alia sensor monitoring, platform event handling, communication with the Shelf Manager and complete activation and deactivation processes not only for the Carrier Board, but also for three attached Advanced Mezzanine Card (AMC) modules. In the future, the software is going to be implemented on the ATCA test boards for LLRF control systems of the FLASH. The application of AdvancedTCA architecture with IPMI functionality in the control system of the X-Ray Free Electron Laser (X-FEL) is considered, as well. Both lasers are situated at Deutsches Elektronen Synchrotron DESY, Hamburg, Germany.

The low-level radio frequency system (LLRF) for the superconducting cavities of the European X-FEL must provide exceptional stability of the accelerating RF field amplitude (0.01%) and phase (0.01 degrees) at a frequency of 1.3 GHz. These requirements must be achieved in pulsed operation mode with one klystron driving 32 cavities. It is thus necessary to design and build a modern LLRF control system, consisting of state of the art hardware and sophisticated control algorithms requiring high gain, low noise, fast and high resolution ADCs (up 16 bits, >100MHz), and high performance data processing using FPGAs and DSPs with low latency. A complete LLRF system must support more than 100 analogue input channels. This paper describes one possible architecture, which will be tested at DESY by the end of 2006

A new version of the SIMCON system is presented in this paper. The SIMCON stands for the microwave, resonant, superconductive accelerator cavity simulator and controller (embracing the hardware and software layers). The current version of the SIMCON is 3.1. which is a considerable step forward from the previous 8-channel version 3.0. which was released at the beginning of 2005 and was made operable in April. Many important upgrades were implemented in SIMCON 3.1. It is a stand-alone VME board (whereas SIMCON 3.0 was modular) based on the Virtex II Pro 30 chip with two embedded Power PCs and DSP blocks. It has Ethernet and multiple gigabit optical I/Os. The Simcon 3.1 board provides 10 ADC channels. The architecture idea and block diagrams of the PCB for SIMCON 3.1. are presented. Some of the applied novel technical solutions, Protel® views and schemes are shown. A number of initial conclusions were drawn from a few month experience with the development of this new board. The tables of predicted system parameters are quoted.

The paper describes design and performance of the DOOCS (distributed, object oriented) based control system for the cavity simulator and controller (SIMCON). A concise description of the DOOCS system is given. Resident data types and data flow throughout the Simcon system are discussed. The basic ideas and implementation issues of the server and client application are described as well as some alternatives to the DOOCS solution (considered as partial) is presented.

The aim of the diagnostic system for the ZEUS Backing Calorimeter (BAC) is to maintain high efficiency and reliability of the detector. The diagnostic system includes hardware tests and a setup configuration tool for the First Level Trigger (FLT) of BAC. This paper describes the test functions of the BAC FLT diagnostic system. Examples of its applications are also presented.

A concise overview of the laboratory solution of the FPGA based TESLA cavity simulator and controller (SIMCON) is presented. The major emphasis is put in this paper on the high level part of the system. There were described the following steps of the system design and realisation: solution choice, design of system components, implementing the solutions, introduction of the application, initial analysis of the working application. The paper is a first description of the working DOOCS server for the FPGA based TESLA cavity SIMCON (which is a part of the LLRF subsystem). The data gathered from the work of the DOOCS server promise for the system optimisation possibilities. The server will be supplemented with the GUI in the next step of this effort. Throughout the work we will refer to the debated system as to the TESLA SIMCON DOOCS server or in short the “simcon server”. The hardware layer of the TESLA cavity SIMCON (to which the designed software refers to) was realized in a single FPGA Virtex chip by Xilinx (XC2V3000 development board by Nallatech).

The idea and realization of data presentation system is described in this paper. Data is received from the diagnostic system of the BAC detector. The presented system is a part of the DQMS (Data Quality Monitoring and Management). The system enables graphical presentation of the location of electronic blocks. It is possible to indicate the links between these blocks, and the actual state of the specified components. The aim to build this system was to assure the proper working of the BAC detector, and in the case of detecting abnormalities to find them out as soon as possible, detect the place of the error and the causes of the failure. The presented software helps to find the errors and is a sort of knowledge compendium about the BAC detector (its equipment, links structure, etc.). The engineering of the visualization system as well as functional tasks were described, and the discussion of the results was made. Some examples, showing the usage of the system, and the received results of its work were presented.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents a FPGA based DSP system for realtime simulation of superconducting accelerator’s cavity. The superconducting linacs require sophisticated control systems for maintaining the constant amplitude and phase of accelerating field in the accelerator’s cavities. The debugging of these systems on real hardware can be both difficult and dangerous. To allow testing of the real LLRF systems in the real time and with different cavity parameters, the FPGA based system has been developed.

New hardware and software developments on the Backing Calorimeter (BAC) for the ZEUS detector are presented. The modernization of the detector was related to the recent luminosity upgrade of the HERA accelerator. The role and place of the BAC detector in the ZEUS experiment is described with special emphasis on the new BAC muon trigger and its diagnostic and monitoring system. This overview introduces a series of detailed articles following in this chapter of the SPIE proceedings.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

One of the most important aims of the BAC diagnostic system is to provide high reliability of the detector. Part of this task is to minimize noises in the position readout and to find optimal thresholds for comparators. Presented paper describes the method of handling this complex problem. In addition collecting a high statistic sample of muon tracks in the clean environment allows to verify the data base describing the mapping of readout channels onto the detector geometry.

This work describes a design and development of the Internet system for the data quality monitoring during the Backing Calorimeter (BAC) operation in the ZEUS experiment and for the archive data analysis. The development includes functional data base system application, data interaction processes and the web interface, built using PHP scripts and JAVA applets. The system implementation process, in ZEUS experiment, was described and its performance results were presented, based on the selected examples.

The paper presents functional structure of database system of data measurement quality for BAC detector in ZEUS experiment. The system collects diagnostic and experimental data. Diagnostic data are: work parameters of the detector and electronics/photonics, tests of electronic/photonic blocks. These data are archived for certain period of time. The quality of current data collection process is estimated using these archived data. The result of such estimation is generated in a form of status map of the detector. Such maps, describing status of the hardware, are fundamental for elementary particle analysis by the calorimeter. The DAQ system, collecting data to the database, estimates data quality on-line during transmission and writing. This mechanism of fast on-line data quality management leads to early discoveries of detector work irregularities and faults.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The paper presents ideas and realization of hardware (photonics and electronics) and software diagnostic layers of TRIDAQ for BAC calorimeter of ZEUS experiment at HERA accelerator. The aim of diagnostic system (DS) is to provide high reliability of the BAC. The diagnostic system localizes, in the fastest possible way, place, time and cause of any breakdown inside the BAC. Functionalities of diagnostic system were discussed. Construction of distributed, diagnostic hardware layer was presented. The software layer of the system was designed using the object-oriented approach. Object oriented virtual classes were defined. These classes control electronics and photonics devices and sub-systems. Application examples were presented. The implementation results of DS for TRIDAQ were discussed.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.