| Paper | Title | Page |
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| WEPB01 | Design of an Electron Beam Energy Control Loop Using Transverse Dispersion | 229 |
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| Stability in mean electron beam energy is of highest interest for a number of experiments performed at the ELBE accelerator. Energy drifts affect parameters of the generated Bremsstrahlung spectra, X-rays or infrared light, as well as the beam trajectory at the production targets or through the FEL waveguide, respectively. In practise, we observe a slow drifting of the effective accelerating field during the first hours after a machine power-up or after switching to different nominal beam energies. Initially, this effect was compensated manually. A first order automation solution has been developed that corrects the resulting energy drift continuously, using a non-intrusive beam position monitor placed in a transversely dispersive part of the beam guide. This paper describes the beam line setup and the simplified dynamic model of the control loop derived from it. Calculation of controller parameters using standard a standard method is shown. The user interface of the control system and working conditions for the loop are explained. Operational performance and conclusions towards improvements close this contribution. | ||
| WEPB02 | Design of an Intra-Bunch-Train Feedback System for the European X-Ray FEL | 232 |
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| After joining the preparatory phase of the European X-ray FEL project, the Paul Scherrer Institute agreed in taking over responsibility for electron beam stabilization by developing a fast intra-bunch-train feedback (IBFB) system, which will be tested in its prototype version at the FLASH linac of the collaboration partner DESY. The proposed IBFB topology consists of two beam position monitors ("upstream BPMs") followed by two kicker magnets for each transverse plane and two more BPMs ("downstream BPMs"). By measuring the position of each bunch at the upstream BPMs and applying suitable transverse kicks individually to the following bunches, the architecture of the FPGA-based digital IBFB electronics (with a latency preferably below the bunch spacing of 200 ns and 1000 ns for the XFEL and FLASH) allows to damp beam motions up to hundreds of kHz. In addition to the FPGA-based feedback, DSPs enable adaptive feed-forward correction of repetitive beam motions as well as feedback parameter optimisation using the downstream BPMs. This paper gives an overview of the architecture and status of the IBFB subsystems being developed, like stripline BPMs, digital electronics and kicker magnets. | ||
| WEPB21 | Kicker Based Tune Measurement for DELTA | 277 |
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| We have set up a tune measurement for the electron storage ring Delta based on broadband beam excitation with a kicker magnet and measurement of the relaxation betatron oscillations turn-by-turn. By averaging over several kicks the kick amplitude may be as low as 600 nrad in standard user runs at nominal current, leading to negligible beam distortion. Signal to noise ratios in excess of 10 are reliably achieved down to 200 uA beam current using a maximum kicker amplitude of 10 urad. A simple tune feedback algorithm compensates for tune shifts due to vacuum chamber movement and orbit movement in sextupoles. | ||
| WEPB24 | Machine Protection and Interlock Systems at Synchrotron SOLEIL | 286 |
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| SOLEIL is a third generation Synchrotron radiation source located in France near Paris, having the classical accelerator structure consisting of a Linac pre-accelerator, a Booster accelerator and a Storage Ring, which are connected by two transfer lines[1]. Since January, the Storage Ring delivers photon beam to 9 beamlines. In order to protect the very sensitive and essential equipment during machine operation, (vacuum chambers, vacuum valves, mirrors, etc.) an interlock system has been implemented. This system is based on industrial and autonomous PLC (Programmable Logic Controller). This paper describes each level of the interlock chain from the diagnostics and vacuum sensors and processes, up to the backbone of the interlock system which stops the RF system. | ||
| WEPB28 | First Tests of the Transverse Multibunch Feedback at Diamond | 295 |
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| This paper describes the design and initial tests of the transverse multibunch feedback system under development at Diamond. The system is designed to damp instabilities up to 250MHz in both the vertical and horizontal plane. This will lead to an increase of instability thresholds which will permit a reduction of chromaticity and thus should improve dynamic aperture and life time. | ||
| WEPC01 | Beam Based Measurements of RF Phase and Amplitude Stability at FLASH | 307 |
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| Beam based techniques to determine the phase and amplitude stability of the photo-cathode laser, the RF gun and superconducting acceleration modules become key tools for the understanding and quality control for FEL operation critical acceleration sub-system. The measurements are used to identify the sources of instabilities, to determine response functions and to optimize RF feedback parameters and algorithm. In this paper, an overview on the measurement techniques and their limitation is given, together with some important results on the currently achieved RF and laser stability. | ||
| WEPC04 | Transverse Feedback Development at SOLEIL | 316 |
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The SOLEIL ring is planned to operate in both multibunch and high current per bunch modes. However, the small vertical chamber aperture around the SOLEIL ring enhances the transverse impedance both in its resistive-wall and broadband content, resulting in instabilities that appear at relatively low current compared to the desired values. A decision was therefore taken to install a digital bunch-by-bunch feedback system, with an aim to make it operational from the beginning of the user operation. The system implemented comprises components developed elsewhere, particularly the FPGA processor of Spring-8, chosen among different possible solutions. Using a BPM and a stripline in the diagonal mode, a single unit of the FPGA processor board has shown to successfully suppress resistive-wall and ion induced instabilities in either one or both transverse planes up to 300 mA. The paper discusses the system characteristics including striplines whose shunt impedance was maximised by keeping the coupling impedance small*, the obtained performance as well as future extensions to overcome the encountered limitations.
* C. Mariette ID1209 |
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| WEPC17 | Fast Orbit Feeback System Upgrade with New Digital Bpm and Power Supply in the Tls | 346 |
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| The BPMs of orbit feedback loop use analogy type in the TLS that is more than 10 years. The analogy type BPM provides high resolution position detection after signal processing. The new generation digital beam position monitor (DBPM) was performed recently. The BPM electronics are commercial available by using direct RF sampling technology, FPGA, and embedded control environment running GNU/Linux. The programmable nature of DBPM system is beneficial for multi-mode high precision beam diagnostics purposes. Sub-micron resolution is achieved for averaged beam position measurement with high update rate. The DBPM are seamless integrated with existed control system and is compatible with old BPM in the orbit feedback loop. In the same time, the corrector power-supply is also upgraded for wide bandwidth control. The integration of old and new BPM, power-supply control for fast orbit feedback will be discussed in this report. | ||
| WEPC19 | Toroid Protection System for FLASH | 349 |
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| The FLASH fast machine protection includes a beam loss interlock using toroids to measure the beam charge. This system monitors the beam losses across the whole linac while other protection systems are specifically dedicated to critical components. Four protection modes are used to handle different scenarios of losses: charge validation, single bunch, slice and integration modes. This system is based on 4 ADC’s to sample the top and bottom of upstream and downstream toroid signals. A microcontroller drives 2 programmable delay generators to adjust the top and bottom ADC trigger during the calibration phase. The samples are then collected by a 200Kgates FPGA to process the various protection modes. At first, a VHDL testbench was developed to generate test vectors at the FPGA design inputs. Then, an electronic testbench simulates the linac signals to validate the global hardware functions. Finally, the toroid protection was tested on FLASH with long bunch train at 1 MHz repetition rate. | ||
| WEPC26 | Transverse Bunch-by-Bunch Feedback for the VEPP-4M Electron-Positron Collider | 367 |
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| Transverse mode coupling instability (TMCI or fast head-tail) is the principal beam current limitation of the VEPP-4M electron-positron collider. For the high-energy physics experiments at the 5.5 GeV energy, the VEPP-4M bunch current should exceed much the TMCI threshold. To suppress transverse beam instabilities, a broadband bunch-by-bunch digital feedback system is developed. The feedback concept is described, the system layout and first beam measurements are presented. |