Electrical Engineering
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Open Access
Abstract: A low beam emittance lattice has been designed for up-grade of the Diamond storage ring. Due to the use of strong focusing elements and rather small vacuum chamber and considering the required short dark time, commissioning of the designed storage ring becomes very challenging. This paper briefly explains the progress of early commissioning simulations of the storage ring, gives the required engineering tolerances, presents the first simulation results and discusses the non-linear beam dynamics (NLBD) issues after successful commissioning with and without insertion devices (IDs).
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Jun 2019
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Electrical Engineering
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Open Access
Abstract: The ongoing trend towards synchrotron light storage rings with ultralow emittance leads to a requirement for strong magnet gradients, which reduce the dynamic aperture and thus the Touschek lifetime of the machine. This is also the case for the planned upgrade of the Diamond Light Source. One option to increase the Touschek lifetime is to lengthen the electron bunches with a harmonic cavity operated close to a harmonic of the fundamental RF frequency. This paper presents studies of a harmonic cavity for Diamond-II with the focus on maximising the lifetime increase. It is foreseen that the ring will have to operate with a gap in the fill pattern to avoid instabilities and therefore multiparticle tracking was used to determine the effect on stability and lifetime for various cavity parameters taking into account transient beam loading.
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Jun 2019
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Electrical Engineering
Mechanical Engineering
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Open Access
Abstract: I12 is a high-energy imaging, diffraction and scattering beamline at Diamond. Its source is a superconducting wiggler with a power of approximately 9kW at 500 mA after the fixed front-end aperture; two permanent filters aim at reducing the power in photons below the operating range of the beamline of 50-150 keV, which accounts for about two-thirds of the total*. This paper focuses on the design and simulation process of the secondary permanent filter, a 4mm thick SiC disk. The first version of the filter was vulnerable to cracking due to thermally induced stress, so a new filter based on an innovative concept was proposed: a water-cooled shaft rotates, via a ceramic interface, the SiC disk; the disk operates up to 900 degrees C, and a copper absorber surrounding the filter dissipates the heat through radiation. We utilised analysis data following failure of an initial prototype to successfully model the heat flow using FEA. This model informed different iterations of the re-design of the assembly, addressing the issues identified. The operational temperature of the final product matches within a few degrees C the one predicted by the simulation.
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Dec 2018
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Electrical Engineering
Magnets
Mechanical Engineering
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Open Access
Abstract: Now that all of the original straight sections in the Diamond storage ring are occupied, novel ways of converting bending magnet beamline locations into insertion device beamlines have been considered. Recently one cell of the 24 cells was reconfigured in to a Double-Double Bend Achromat (DDBA) to provide a new location for an Undulator and enable a formerly designated bending magnet beamline to become an Insertion Device Beamline*. Extending this concept for the new Dual Imaging and Diffraction (DIAD) Beamline proved to have a strong impact on lifetime and injection efficiency, so instead it was decided to remove a Sextupole magnet in one cell and substitute it with a short fixed gap Wiggler. The accelerator physics, mechanical and electrical design aspects associated with the change are described.
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Dec 2018
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Electrical Engineering
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Abstract: This paper investigates the possibility for suppression of the head-tail instability in an electron storage ring using a bunch-by-bunch transverse feedback system. General conditions are found whereby the Gaussian bunch profile may be modeled by a two-particle system which interacts with the vacuum chamber broadband impedance. We choose the kick factor received by a Gaussian bunch with the rms bunch length
σt
, from a broadband impedance with the resonance frequency
ωr
and quality factor
Qr
, as the relevant parameter and explain why the kick factor depends on
ωrσt∕Qr
. Finally, we demonstrate that a Gaussian bunch can be modeled by a two-particle system when the parameter
ωrσt∕Qr
is sufficiently small.
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Dec 2018
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Electrical Engineering
Mechanical Engineering
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Open Access
Abstract: Diamond Light Source is in the process of reviewing several lattice options for a potential storage ring upgrade. As part of these studies, it has become clear that a substantial reduction in emittance can be achieved by adopting an on-axis injection scheme, thereby relaxing the constraints on the dynamic aperture. In order to achieve the necessary injected bunch properties for this to be viable, a new accumulator ring would be needed. In this paper we review the requirements placed on the accumulator ring design, describe the lattice development process and analyse the performance of the initial, conceptual design.
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Sep 2018
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Electrical Engineering
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Open Access
Abstract: Diamond Light Source is in the process of reviewing several lattice options for a potential storage ring upgrade. As part of these studies, it has become clear that a substantial reduction in emittance can be achieved by adopting an on-axis injection scheme, thereby relaxing the constraints on the dynamic aperture. In order to achieve the necessary injected bunch properties for this to be viable, a new accumulator ring would be needed. In this paper we review the requirements placed on the accumulator ring design, describe the lattice development process and analyse the performance of the initial, conceptual design.
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Jun 2018
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Electrical Engineering
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Open Access
Abstract: Diamond SCRF cavities are pulse conditioned every week in order to keep them operating reliably. During conditioning, the cavities are detuned in order to sweep the standing wave through the waveguide. To match these cavities at lower voltage (typically < 1.4 MV) and at higher power, 3 stub tuners are used in the waveguide feed. Simulations with CST studio show that a strong SW field exists between the RF window and the matching posts. As the cavity is detuned the electric field maximum passes through the window causing heating of the ceramic. Temperature measurements with thermal camera reveal that the temperature of the window increases to maximum when the cavity is detuned towards higher frequency. Based on the simulation results and the measurements, it was decided to reduce the conditioning voltage. These results are summarised.
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Jun 2018
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Electrical Engineering
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Abstract: Single bunch instability studies have been carried out at
Diamond with and without the transverse multi-bunch feedback
(TMBF) system. Single bunch instability thresholds
were measured for zero, positive and negative chromaticity
values by increasing the current till the instability onset. The
bunch-by-bunch feedback system was then used to suppress
the motion of the bunch centroid and the new thresholds were
measured in all chromaticity regimes. The feedback loop
phase of the TMBF was changed from resistive to reactive
as well as intermediate to find the optimal feedback settings
that maximize the single bunch instability thresholds.
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Jun 2017
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Electrical Engineering
Insertion Devices
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Open Access
Abstract: In planning the upgrade of one cell of the Diamond Storage Ring, the DDBA upgrade, it was evident that the electrical installation and commissioning would contribute a significant component of the overall installation time. Given the pressures to minimise the shutdown length, the electrical and instrumentation design was optimised for time effective installation and commissioning. This paper outlines the electrical and instrumentation design for DDBA; explores the installation time determining issues and how these were addressed; and reports on the lessons learnt from the actual installation and commissioning process.
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May 2017
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