DELTA, Dortmund
The beam orbit of the 1.5GeV electron storage ring DELTA showed a variety of beam distortions with a pronounced frequency spectrum mostly caused by girder movements and ripples of the magnet power supplies. In order to enhance the orbit stability at least up to 300 Hz bandwidth a global fast orbit feedback is under consideration. As a prototype an FPGA based local fast orbit feedback at a 10 kHz data acquisition rate has been developed. The digitized orbit data are distributed from I-Tech Libera and Bergoz MX-BPMs to an FPGA board via a fibre interconnected network based on the Diamond Communication Controller [*]. The correction algorithm is written in VHDL and the corrections are applied with digital power supplies connected to the FPGA board through RS485 links. The first operational tests of the system achieved an effective damping of orbit distortions up to 350 Hz. The paper will give an overview on the layout of the FPGA based local orbit feedback system, will report on the results of the measured uncorrected orbit distortions at DELTA and the stability enhancements that could be achieved by the local feedback system.
* I. S. Uzun et al., "Initial Design of the Fast Orbit Feedback System for
Diamond Light Source", Proc. 10th ICALEPCS
ISA, Aarhus
This paper presents an overview of the proposed beam diagnostic for Astrid2, which is the new 580 MeV 3rd generation synchrotron light source to be build in Aarhus, Denmark. Astrid2 will use the present Astrid1 as booster, allowing for full energy injection and thereby top-up-operation. The diagnostics will include viewers, beam current monitors, electronic beam position monitors, striplines, etc. The description will include both the storage ring and the transfer beam line.
NSRRC, Hsinchu
A new high brilliant 3 GeV storage-ring-based light source - Taiwan Photon Source (TPS) - is planned to be built at the National Synchrotron Radiation Research Center. Various diagnostics will be deployed to satisfy stringent requirements for commissioning, operation, and top-off injection of the TPS. Specifications and an overview of the planned beam instrumentation system for the TPS will be summarized in this report. Efforts in diagnostic devices and subsystems will also be addressed.
BESSY GmbH, Berlin
Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
BunchView is a system for the direct measurement of the current from each bunch circulating in a storage ring based on the analysis of the RF-signals delivered by a set of striplines. This paper describes the development, achievements, operation, and results of this fast and accurate bunch current monitor built for the BESSY and MLS storage rings. Using a combination of a 14/16Bit ADC, a high-speed FIFO, ECL technique, and FPGAs, a real-time measurement of the fill-pattern with high accuracy and bunch-by-bunch resolution was achieved. The results are identical to the fill-pattern determined by time correlated single photon counting based on synchrotron radiation detected with an avalanche photo diode. BunchView is fully integrated into the EPICS control system. The data provided by the BunchView monitor give accurate bucket position in the ring and bunch current over a wide range of currents. The smallest measured single bunch current is less than 100nA. In the future the system will be used in the top-up mode of operation in order to inject beam into the emptiest buckets and thus keep the fill-pattern stable over longer periods of time.
Diamond, Oxfordshire
During normal operation of synchrotron third generation light source like Diamond, the measurement of the electron bunch profile, of the order of 10~ps, is perfectly done with a streak camera. However, in 'low alpha' operation, where the momentum compaction factor is reduced in order to shorten the bunch length, the measurement becomes extremely close to the resolution of the camera. In such a case, performing a good measurement and extracting the real information requires a good knowledge of the impulse response of the streak camera. We present analysis and measurement of the contributions to the point spread function of the streak camera: the static point obtained by measuring a focussed beam without any sweep, which can be achieved at best around 5.5 pixels (0.7~ps with the fastest sweep), but also the chirp introduced by refractive optics and a large spectral beam, measured with a spectrograph at 26~fs/nm. Then we discuss short bunch measured in 'low alpha' operation and the agreement between measurements and expectation from theory.
MPI-K, Heidelberg
At the Max-Planck-Institute for Nuclear Physics in Heidelberg a cryogenic electrostatic storage ring (CSR) is under construction, which will be a unique facility for low velocity and in many cases also phase-space cooled ion beams. Among others the cooling and storage of molecular ions in their rotational ground state is planned. To meet this demand the ring must provide a very low level of blackbody radiation and a vacuum in the XHV range (10-15 mbar) which is achieved by cryogenic cooling of the ion beam vacuum enclosure to 2-10K. The beam current will be in the range of 1 nA -1 μA. The resulting low signal strengths together with the cold environment put strong demands on the amplifier electronics. We plan to make use of a resonant amplifying system. Using coils made from high purity copper, we expect quality factors of ~1000. The mechanical design has to provide stability of the alignment against thermal shrinking when switching from room temperature operation to cryogenic operation. A prototype pickup has been built in order to test resonant amplification and the mechanical design with a wire. The amplification principle will be tested in the MPI-K’s Test Storage Ring.
ESRF, Grenoble
Until 2008, the suppression of the closed orbit distortion on the storage ring of the ESRF was obtained using two separate systems: A slow system using 224 BPM and 96 correctors performing a correction every 30 seconds, and a fast system, using only 32 BPMs and 32 correctors but working at 4.4KHz, damping the orbit distortion from 50mHz up to 150Hz; the 15mHz to 50mHz frequency span was left uncorrected. This separation of the frequency ranges of the two systems avoided cross talks between them, but prevented the efficient cancellation of the very low frequency orbit distortions caused by the frequent modification of the insertion device settings during the beamlines operation. We now coordinate the operation of the slow and fast systems and suppress this dead frequency span. This paper describes the principle and the beneficial effect of this new scheme, and its limitations. To overcome these limitations, we are now developing a single new orbit correction system which will damp the orbit distortion from DC to 150Hz; this system will use the Libera Brillance BPM electronics recently implemented at ESRF, and new fast correctors. This new scheme is also briefly presented.
ASCo, Clayton, Victoria
The Australian Synchrotron (AS) timing system is based on a hybrid design: an Event Generator-Event Receiver (EVG-EVR) system creates the injection trigger and various clocks, while a network of digital delay generators adjusts pulse delays and widths. This architecture, combined with a storage ring fill pattern monitor, allows the targeting of injection into specific buckets in the storage ring. Nevertheless, more demanding needs from the machine and the beamlines require an upgrade of the system. Delay generators will be removed and replaced by EVRs. This will allow fixed or variable frequency clocks to be made available to beamlines or to trigger diagnostic hardware, orbit interlock distribution, etc., while reducing jitters to below 100 ps. This paper presents the architecture of the new timing system at AS and emphasizes its benefits for diagnostic tools.
Diamond, Oxfordshire
JAI, Oxford
The operation of the Diamond storage ring with short electron bunches using ‘low alpha’ optics for generation of Coherent THz radiation and short X-ray pulses for time-resolved experiments is limited by the onset of microbunch instabilities. We have installed two ultra-fast (time response is about 250 ps) Schottky Barrier Diode Detectors sensitive to radiation within the 3.33-5 mm and 6-9 mm wavelength ranges. Bursts of synchrotron radiation at these wavelengths have been observed to appear periodically above certain thresholds of stored current per bunch. The fast response allows a bunch-by-bunch and turn-by-turn detection of the burst signal, which facilitates study of the bursts’ structure and evolution. In this paper we present our first results for various settings of alpha and also discuss future plans for the modification of a beam port to improve sensitivity of the system.
GSI, Darmstadt
The FAIR (Facility for Antiprotons and Ions Research) accelerator complex is currently designed and projected at GSI. The unique features of the central machine SIS100, like e.g. the acceleration of high intensity beams of 2.5·1013 protons and 5·1011 Uranium ions, the operation close to the space charge limit leading to a large tune spread and the extreme UHV conditions of the cryogenic system for fast ramped superconducting magnets, make challenging demands on the beam diagnostic components. This contribution describes the general concept of beam diagnostics for FAIR and reports on the present status of prototype studies. Exemplarily the achievements for a novel type of dc transformer, beam position monitors and the ionization profile monitor are discussed and first measurements with prototype setups are presented.
