Electronics and algorithms for HOM based beam diagnostics

The signals from the Higher Order Mode (HOM) ports on superconducting cavities can be used as beam position monitors and to do survey structure alignment. A HOM-based diagnostic system has been installed to instrument both couplers on each of the 40 cryogenic accelerating structures in the DESY TTF2 Linac. The electronics uses a single stage down conversion form the 1.7 GHz HOM spectral line to a 20MHz IF which has been digitized. The electronics is based on low cost surface mount components suitable for large scale production. The analysis of the HOM data is based on Singular Value Decomposition. The response of the OM modes is calibrated using conventional BPMs

RF-Energy Management for the European XFEL

The European XFEL is in its commissioning phase at this time. One of the major tasks is to bring up all the 25 installed RF-stations, which will allow for a beam energy of up to 17.5 GeV. It is expected, that a klystron may fail every 1-2 month. The accelerator is designed at the moment with an energy overhead corresponding to 2-3 RF-station, as the last 4 accelerating modules will be installed in a later stage. This will allow recovering the missing energy with the other functioning RF-stations to keep downtime as short as possible in the order of seconds. The concept and corresponding High-Level software accomplishing this task will be presented in this paper

Fast Automatic Ramping of High Average Power Guns

The electron guns at PITZ, FLASH and European XFEL are standing wave structures which operate at high average power (>40 kW) to produce long trains of high quality beams. This amount of power heats the cavity surface enough to change signicantly the gun resonance frequency. As consequence, to keep the reection low, the RF power ramp must be enough slow to permit the water cooling system to keep the gun temperature close to the set-point. Also, as the temperature probe sits close to the surface of the iris, the required gun temperature set-point to maintain the gun on resonance is a function of the average power. The RF power ramping is a difficult process in which temperature and reection must be monitored to adjust accordingly the temperature set-point and the ramping speed of the RF power. An automatic software to adjust the RF frequency and the temperature set-point of the PITZ gun in parallel to the RF power ramping has been developed. The use of this software has signicantly reduced the time spent to start up the gun or to recover from interlocks, increasing the time spent at nominal parameters which would also be very important for user facilities

Taskomat & Taskolib: A Versatile, Programmable Sequencer for Process Automation

This contribution introduces the Taskolib library, a powerful framework for automating processes. Users can easily assemble sequences out of process steps, execute these sequences, and follow their progress. Individual steps are fully programmable in the lightweight Lua language. If desired, sequences can be enhanced with flow control via well-known constructs such as IF, WHILE, or TRY. The library is written in platform-independent C++17 and carries no dependency on any specific control system or communication framework. Instead, such dependencies are injected by client code; as an example, the integration with a DOOCS server and a graphical user interface is demonstrated

Commissioning of the Electronics for HOM-based Beam Diagnostics at the 3.9 GHz Accelerating Module at FLASH

Transverse Higher Order Modes (HOM) excited by electron beams in the 3.9GHz accelerating cavities at FLASH may damage the beam quality. They can be reduced by extracting their energy through special couplers and by aligning the beam in the cavity. Electronics has been designed at FNAL for monitoring some of the potentially most damaging HOMs. This may be used for beam centering and therefore reducing the HOM effects. Moreover, the signals can be potentially calibrated into beam offset, so that they could be used as beam position monitors (HOM-BPM). The specificationsof the monitors have been defined during an extensive study on the 4-cavity accelerating module installed at FLASH. Signals around 5.46 GHz have been chosen for higher precision measurements. However these signals propagate into the entire 1.2 m long module. Therefore in addition modes at about 9.06 GHz were selected for localized measurements in each cavity. The electronics has been recently installed at FLASH. The initial experience with this electronics is presented in this paper. The signals can already be used for centering. Some instability in the signals has been observed and the cause has to be further investigated

High Level Controls for the European XFEL

The European X-Ray Free-Electron Laser (XFEL) will generate extremely short and intense X-ray flashes from the electron beam of a 2.1 km long superconducting linear accelerator. Due to the complexity of the facility and the sheer number of subsystems and components, special emphasis needs to be placed on the automatization of procedures, on the abstraction of machine parameters, and on the development of user-friendly high-level software for the operation of the accelerator. The paper gives an overview of the ongoing work and highlights several new tools and concepts

The Virtual European XFEL Accelerator

The ambitious commissioning plans for the European XFEL require that many of the high-level controls are ready from the beginning. The idea arose to create a virtual environment to carry out such developments and tests in advance, to test interfaces, software in general and the visualisation of the variety of components. Based on the experiences and on the systems that are already in operation at the FLASH facility for several years, such a virtual environment is being created. The system can already simulate most of the key components of the upcoming accelerator. Core of the system is an event synchronized data acquisition system (DAQ). The interfaces of the DAQ system towards the device level, as well as to the high-level side is utilising the same software stack as the production system does. Thus, the software can be developed and used interchangeably between the virtual and the real machine. This allows to test concepts, interfaces and identify problems and errors at an early stage. In this paper the opportunities arising from the operation of such a virtual machine will be presented. The limits in terms of the resulting complexity and physical relationships will also be shown

European XFEL Linac RF System Conditioning and Operating Test

96 accelerating modules with 768 TESLA / European XFEL type superconducting cavities were installed in the European XFEL LINAC tunnel (XTL) in fall 2016. Warm conditioning of the RF system - High/Low Level RF System and main input couplers - begun even before finishing the accelerator installation works. All modules were conditioned and tested prior to the installation in the tunnel in the AMTF test stand at DESY. Nevertheless, due to some repair activities on warm Input coupler parts, warm conditioning was needed on a few modules/couplers. Cooling down to 2K begun in December 2016 and was finished in January 2017. Since then cold conditioning and tests are running. A few Input couplers did have problems with conditioning and were disconnected, limiting otherwise the system performance. Some cavities in the modules showed multipacting (MP) effects, mostly because the cavity vacuum was vented with dry nitrogen gas because of mentioned repairs on couplers in some modules. Such MP effects did appear in AMTF as well. All MP effects were successfully conditioned until now