Accelerator Physics
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Jun 2013
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Accelerator Physics
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Jun 2013
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Abstract: There are over forty synchrotrons and fourth generation light sources around the world, which generate synchrotron radiation for academic and industry research by bending electrons that are accelerated to relativistic speeds. To preserve the quality of the photon beam used for experiments, a feedback control system is used to reduce variations in the position of the electron beam. This paper describes the design and robust stability analysis of a beam stabilisation controller, which is considered as a cross-directional control system. Fourier series analysis is used to identify the spatially controllable components of the system and develop a realistic uncertainty model that is used in robust stability tests. The robust stability of the controller is determined by considering both the unbounded sector nonlinearity associated with the actuators and the unmodeled spatial plant response within an Integral Quadratic Constraint (IQC) framework, leading to a robust stability condition that is expressed as a linear matrix inequality (LMI). The paper presents results from the implementation of the controller at Diamond Light Source.
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Dec 2012
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Controls
Data acquisition
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Oct 2011
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Abstract: At Diamond Light Source the Experimental Physics and Industrial Control System (EPICS) is used with a variety of motion controllers. The use of EPICS ensures a common interface over a range of motorized applications. We have developed a system to enable the use of the same interface for synchronized motion over multiple axes using the Delta Tau Programmable Multi Axis Controller (PMAC). Details of this work will be presented, along with an example and possible future developments.
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Oct 2011
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Abstract: The commissioning of the Diamond Light Source accelerators began in 2005, with routine operation of the storage ring commencing in 2006, and photon beamline operation in January 2007. The Diamond Control System uses the EPICS tool-kit and provides a high degree of integration of the underlying technical systems. These include all power converters, most diagnostics, vacuum systems, the machine protection system, insertion devices, RF amplifiers, girder alignment, front-ends, photon beamlines, experiment stations, instrumentation and detectors. Most of this equipment is interfaced through a range of generic VME I/O based on VME IP carriers, IP modules, transition cards and plant interface modules. It now supports the three accelerators and a suite of twenty photon beamlines and experiment stations. This paper presents an analysis of the operation of the control system and reviews the major developments that have taken place since the first operations
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Oct 2011
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Abstract: A transverse multibunch feedback (TMBF) system is in operation at Diamond Light Source to damp coupled-bunch instabilities up to 250 MHz in both the vertical and horizontal planes. It comprises an in-house designed and built analogue front end combined with a Libera Bunch-by-Bunch feedback processor and output stripline kickers. FPGA-based feedback electronics is used to implement several diagnostic features in addition to the basic feedback functionality. This paper reports on the current operational status of the TMBF system along with its characteristics. Also discussed are operational diagnostic functionalities including continuous measurement of the betatron tune and chromaticity
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Oct 2011
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Accelerator Physics
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Diagnostics
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Abstract: Synchrotron light sources can produce very intense beams of X-rays and ultra violet light for a range of applications, including protein crystallography, materials characterization and high resolution imaging. The Diamond Light Source is a 3rd generation synchrotron that has recently been constructed near Oxford, United Kingdom, which produces a 3 GeV electron beam in a ring of circumference of over 560 m. A key requirement of the process is that the vertical and horizontal location of the beam should be controlled to within 10% of the beam size, which corresponds to the RMS variation being less than 12.3 μm in the horizontal direction and 0.6 μm in the vertical direction. The beam location is subjected to disturbances caused by the effects of Insertion Devices and the effect of ground motion, particularly between 16 Hz and 30 Hz, where the ground motion is amplified by the resonances of the girders supporting the ring magnets. To achieve the specification, a fast beam stabilization feedback system is used to regulate the horizontal and vertical position of the beam in the presence of disturbances in the range 1 Hz to 100 Hz, using 170 sensors and actuators in both planes, positioned around the ring at a sampling rate of 10 kHz. This paper describes the design of the controller for this system and the results from the implementation are shown.
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Sep 2011
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Accelerator Physics
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Abstract: Single shot transverse emittance measurement is essential to assess the beam quality and performance of new generation light sources such as linac based X-ray Free Electron Lasers (FELs) or laser plasma wakefield accelerators (LPWA). To this end, we have developed a single shot transverse emittance measurement using at least 3 screens inserted in the beam at the same time, measuring the beam size at different positions in a drift space in one single shot. In this paper, we firstly present the theoretical aspects to perform the measurement. We secondly show experimental results obtained at Diamond for a 3 GeV electron beam in the transfer line from the Booster to the Storage Ring, using this thin OTR screens method. Finally, we discuss the results showing the strength of the measurement in comparison with more standard and established emittance measurement, like the quadrupole scan method.
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Jul 2011
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Accelerator Physics
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Open Access
Abstract: We study the possibility to produce a 1.6 pC electron beam (107 electrons) with a bunch length of less than 10 fs and a beam energy of a few MeV. Such a short, relativistic beam will be useful for an electron diffraction experiment with a 10 fs time resolution. An electron beam with 107 electrons will allow a single-shot experiment with a laser pulse pump and an electron beam probe. In this design, an S-band photocathode gun is used for generating and accelerating a beam and a buncher consisting of two S-band four-cell cavities is used for temporally compressing the beam. Focusing solenoids control the beam transverse divergence and size at the sample. Numerical optimization is carried out to achieve a beam with a 4 fs full-width-at-half-maximum length, a 26 microradian root-mean-square divergence, and a 2 nm transverse coherence length at a 3.24 MeV beam energy. When state-of-the-art rf stability is considered, beam arrival time jitter at the sample is calculated to be about 10 fs
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May 2011
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