[Show abstract][Hide abstract] ABSTRACT: The Free-Electron Laser in Hamburg (FLASH) is now equipped with a microTCA-based (MTCA.4) low-level ra-dio frequency (LLRF) system, to replace the previous VME system and to serve as a test bench for the European X-ray Free Electron Laser (XFEL) LLRF system. This paper presents details on the new FLASH LLRF system setup, in-cluding installations inside the radiation prone tunnel envi-ronment. The benefits and preliminary results of the newly installed system are also given.
[Show abstract][Hide abstract] ABSTRACT: Due to its scale and tight specifications, the European XFEL poses real challenges in the field of low-level radio-frequency (LLRF) control. The implementation of this semi-distributed control system on the microTCA for physics (MTCA.4) platform triggered numerous designs of electronic boards and helped refine the usage of MTCA.4 technology for physics and control systems. This paper presents an overview of the MTCA.4-based LLRF system for the European XFEL with an emphasis on the system architecture decisions. The multiple functionalities of this highly modular design will be explained as well as the opportunities of the MTCA.4 technology for other applications.
Mixed Design of Integrated Circuits and Systems (MIXDES), Gdynia; 06/2013
[Show abstract][Hide abstract] ABSTRACT: FLUTE is a linac-based accelerator test facility and a THz source currently being constructed at KIT with an electron beam energy of � 41MeV. It is designed to cover a large charge range from a few pC to � 3 nC. FLUTE is
optimized to provide ultra-short electron bunches with an RMS length down to a few fs. In this contribution, we focus on the layout of the machine from the RF gun & gun laser over the linac and the compressor to the THz beamline for the generation of coherent synchrotron, transition and edge radiation (CSR, CTR, CER).
[Show abstract][Hide abstract] ABSTRACT: High brightness electron sources for linac based free-electron lasers (FELs) are being developed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). Production of electron bunches with extremely small transverse emittance is the focus of the PITZ scientific program. The photoinjector optimization in 2008–2009 for a bunch charge of 1, 0.5, 0.25, and 0.1 nC resulted in measured emittance values which are beyond the requirements of the European XFEL [S. Rimjaem et al., Nucl. Instrum. Methods Phys. Res., Sect. A 671, 62 (2012)]. Several essential modifications were commissioned in 2010–2011 at PITZ, resulting in further improvement of the photoinjector performance. Significant improvement of the rf gun phase stability is a major contribution in the reduction of the measured transverse emittance. The old TESLA prototype booster was replaced by a new cut disk structure cavity. This allows acceleration of the electron beam to higher energies and supports much higher flexibility for stable booster operation as well as for longer rf pulses which is of vital importance especially for the emittance optimization of low charge bunches. The transverse phase space of the electron beam was optimized at PITZ for bunch charges in the range between 0.02 and 2 nC, where the quality of the beam measurements was preserved by utilizing long pulse train operation. The experimental optimization yielded worldwide unprecedented low normalized emittance beams in the whole charge range studied.
Physical Review Special Topics - Accelerators and Beams 10/2012; 15(10). · 1.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The European X-Ray free electron laser accelerator consists
of 808 superconducting cavities grouped in 25 RF stations.
The challenges associated with the size and complexity
of this accelerator require a high-precision, modular
and scalable low level RF (LLRF) system. The Micro
TCA technology (MTCA.4) was chosen to support this
system and adapted for RF standards. State-of-the-art hardware
development in close collaboration with the industry
allowed for the system continuity and maintainability. The
complete LLRF system design is now in its final phase and
the designed hardware was installed and commissioned at
FLASH. The MTCA.4 LLRF architecture and system performance
results will be shown. Operation strategies and
future automation algorithms for performance optimization
will also be presented in this paper.
International Particle Accelerator Conference, IPAC 2012, New Orleans, Louisiana, USA; 05/2012
[Show abstract][Hide abstract] ABSTRACT: The European X-Ray free electron laser accelerator consists of 808 superconducting cavities grouped in 25 RF stations. The challenges associated with the size and complexity of this accelerator require a high-precision, modular and scalable low level RF (LLRF) system. The Micro TCA technology (MTCA.4) was chosen to support this system and adapted for RF standards. State-of-the-art hard-ware development in close collaboration with the industry allowed for the system continuity and maintainability. The complete LLRF system design is now in its final phase and the designed hardware was installed and commissioned at FLASH. The MTCA.4 LLRF architecture and system performance results will be shown. Operation strategies and future automation algorithms for performance optimization will also be presented in this paper.
[Show abstract][Hide abstract] ABSTRACT: Transverse Deflecting Systems are designated for longitudinal beam diagnostics of ultra-short electron bunches in modern FEL projects. At the European XFEL, Transverse Deflecting Systems are foreseen at three locations. A prototype of the TDS in the injector of the European XFEL will be installed at PITZ, which is identical in terms of deflecting structure, low-level RF system and powerful RF hardware. This PITZ TDS has the aim to prove the required performance for all TDS subsystems as well as serve as a diagnostics tool for PITZ. Results of the test cells measurements of a S-band traveling wave structure are presented, showing very good agreement with calculated parameters. RF power supply system, including a 3 MW klystron and other RF hardware, is described. Solid state 130 kV Marx modulator has been developed for the klystron feeding. 10 kV module of the modulator has been built and tested. The modulator allows for high voltage shutdown within pulse.
[Show abstract][Hide abstract] ABSTRACT: The paper describes the hardware and software architecture of a control and measurement system for electromagnetic field stabilization inside the radio frequency electron gun, in FLASH experiment. A complete measurement path has been presented, including I and Q detectors and FPGA based, low latency digital controller. Algorithms used to stabilize the electromagnetic field have been presented as well as the software environment used to provide remote access to the control device. An input signal calibration procedure has been described as a crucial element of measurement process.
[Show abstract][Hide abstract] ABSTRACT: The master oscillator (MO) and phase reference system at FLASH must provide several RF reference frequencies to widely spread locations with low phase noise and small long term phase drifts. The phase noise requirement of the 1300 MHz reference is of the order of 0.1 deg. while the short and medium term phase stability are of of the order of 0.1 deg. and 1 deg. respectively. The frequency distribution system employs a temperature stabilized coaxial line for RF power distribution and a fiber optic system for the monitoring of phase drifts. Presented are the the concept, design and performance measured in the accelerator environment.
[Show abstract][Hide abstract] ABSTRACT: For pump-probe experiments at VUV- and X-ray free- electron lasers, in the injector and bunch compression section the electron beam and timing reference must be in phase within 0.01 degree (rms) and have an amplitude stability within 10<sup>-4</sup> (rms). The performance of the field detection and regulation of the acceleration RF critically influences the phase and amplitude stability. For the RF field control, a multichannel RF downconverter is used to detect the field vectors and control the vector sum of 32 cavities. In this paper a new design of an 8 channel downconverter is presented. The downconverter front-end consists of a passive RF double balanced mixer input stage, intermediate filters, and an integrated 16 Bit analog-to-digital converter (ADC). The design includes a digital motherboard for data pre-processing and communication with the controller. In addition, we characterize the downconverter performance in amplitude and phase jitter, temperature drifts, and channel cross-talk in a laboratory environment.
[Show abstract][Hide abstract] ABSTRACT: A longitudinal broadband damper system to control coupled bunch instabilities (LMBF) has been installed in the 920 GeV proton accelerator HERA-p at the Deutsches Elektronen-Synchrotron DESY in Q4/2005. This was one of the attempts to increase the specific luminosity at HERA by reducing the bunch length. The feedback system is based on a single board FPGA (field programmable gate array) with two ADCs and 2 DACs (each 14 bits resolution) at 52 MHz sampling rate. It was fully automated, in order to relief the operator from manual control during system operation. During commissioning in Q1/2006 it turned out that the performance goals were reached and the noise introduced due to the feedback corrections and the 1 kW power amplifier was not as much a problem as expected. The proton bunch length is significantly reduced as well as the lengthening of the bunches over runtime since all formally occurring coupled bunch instabilities could sufficiently be suppressed during the enegergy ramp and the following luminosity run. System optimization points were found in automatic gain adjustment during acceleration ramp, oscillation level triggering and timing of kicker pulse to bunch.
[Show abstract][Hide abstract] ABSTRACT: This paper includes a description of a prototype DAC plus Vector Modulator board and process of starting the system up. The idea of vector modulation and its limitations are also discussed below. The board is a part of the LLRF system, which provides the control of a superconductive accelerator and free electron laser. The article describes the hardware project implementation of the system. The PCB structure of the designed board is presented. New ideas of improvements for the next version of high power klystron driver are discussed.
Proceedings of SPIE: Photonics Applications in Astronomy, Communications, Industry, and High-Energy Physics Experiments. 01/2007;
[Show abstract][Hide abstract] ABSTRACT: A longitudinal broadband damper system to control cou- pled bunch instabilities has recently been constructed and installed in the 920 GeV proton accelereator HERA-p at the Deutsches Elektronen-Synchrotron (DESY). The goal of this system is to reduce the bunch length and thus in- crease specific luminosity at HERA-p. Within the con- trol system a kicker cavity is used as an actuator. The original aspect of this cavity lies in the simple geometry with no need for vacuum inside the cavity and high shunt impedance despite an internal ferrite load. The ferrite load is successfully used to dampen higher order modes down to Q