Accelerator Physics
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Open Access
Abstract: To satisfy user demands for a high-brightness, high-capacity synchrotron light source, a novel multibend achromat (MBA) lattice structure has been developed for the Diamond-II storage ring upgrade. This lattice combines the high-dispersion locations characteristic of hybrid MBA lattices with newly introduced midcell straight sections to allow extra insertion devices to be installed. The resulting structure is named the modified hybrid six bend achromat (MH6BA) lattice. When adapted to fit in the existing 560.6 m Diamond storage ring tunnel, it reaches a natural emittance of 162 pm rad at 3.5 GeV. The characteristics of the MH6BA lattice, the methodology used to optimize the linear and nonlinear beam dynamics, and the lattice performance in a range of conditions are discussed.
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Nov 2024
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Accelerator Physics
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Abstract: Beam position studies have been performed using a Cherenkov Diffraction Radiation (ChDR) based Beam Posi- tion Monitor (BPM) at Diamond Light Source (DLS). This work presents the characterisation of the BPM using the 3 GeV electron beam and comparing the effectiveness of this prototype to an existing Inductive Beam Position Monitor (IBPM) in use in the DLS Booster To Storage (BTS) transfer line. The functionality of the BPM is explored, utilising both wideband and narrowband ChDR emission with the application of filters to the ChDR detection system.
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Sep 2024
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Accelerator Physics
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Open Access
Abstract: The Linac for Diamond Light Source has been running with two 3 GHz klystrons, powering two 5.2m-long accelerating structures to deliver 100 MeV electron beam since the start of operation. By introducing a SLED pulse compressor system to generate a pulse capable to power both structures from one klystron, redundancy and reliability will be improved. With a 5 µs total pulse, it is possible to charge the SLED cavities for 4 µs and generate a high peak pulse for the last 1 µs able to power both structures. An arbitrary waveform generator function was implemented in digital low-level RF to generate a flat top pulse, which can be utilized for both single bunch and multi bunch operation. Details of the waveguide network, low-level RF design and high-power operation will be described. Results from full energy operation will also be shown.
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Aug 2024
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Accelerator Physics
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Open Access
Abstract: Challenges associated with the design are, firstly, the heat loads of I05 beamline upgrade involving the installation of a powerful and highly divergent APPLE-II Knot Insertion Device. Secondly, it is not easy to produce the required homogeneous NEG (non-evaporable getter) coating on the complex internal geometry of the vessel. Synchrotron light raytracing and thermal analysis has shown that an aluminium vessel with discrete copper absorbers was not capable of handling the high heat loads and it was decided to change to a copper vessel with large integrated absorbing surfaces. FEA analysis of the copper vessel shows the peak temperature is reduced from 446°C to 95°C for the copper vessel as compared to the aluminium vessel. NEG coating trials are currently in progress and will be followed by a full prototype. The minimum vertical aperture is 6 mm and the trials will show whether it can be reduced to 5 mm. The change from an aluminium vessel to a copper vessel will not only reduce the peak temperature of the vessel thereby making it a workable solution, but has the added benefits of improved vacuum performance, reduced beam impedance and reduced capital and operating cost.
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Jun 2024
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Accelerator Physics
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Abstract: Impedance is a significant concern in modern storage rings like Diamond-II, due to instabilities limiting maximum bunch charge and other potential effects such as emittance dilution. Significant changes have been made to the Diamond-II impedance database, partly driven by progress in engineering design work, and partly by the requirements of particle tracking simulations and increase in available computing resources. We present an overview of the current state of the Diamond-II impedance database, focusing on the most significant updates and additions.
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May 2024
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Accelerator Physics
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Open Access
Abstract: To reduce filling times and enable advanced injection schemes, it is desirable for the Diamond-II booster to provide high charge in both single and multi-bunch modes. The single bunch charge will be limited by short range wakefields in the booster, and long-range wakefields limit the charge for the multi-bunch trains. Due to the relatively low 100 MeV injection energy into the booster, the injected beam is susceptible to instabilities due to the very weak synchrotron radiation damping. In this paper, we present the simulation results carried out to estimate the single and multi-bunch charge thresholds in the Diamond-II booster including short and long range wakefields, RF cavity HOMs, and with physical apertures applied. Simulations results will also be presented that demonstrate the extracted multi-bunch charge could be increased by installing a transverse multi-bunch feedback (TMBF).
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May 2024
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Accelerator Physics
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Open Access
Abstract: The design performance of the 3.5 GeV Diamond-II low-emittance electron storage ring has been studied as a function of the linear and nonlinear lattice tuning parameters. An alternative working point has been iden- tified which optimizes the beam lifetime and the injection efficiency for off-axis injection. The simulations include misalignment and field strength errors, with the number of machine seeds tuned to achieve converg- ing results whilst minimizing computational time. The optimization takes care to preserve the design beam emittance, energy spread, Twiss parameters and cell tunes. The results are presented for 2D parameter scans and exploring the null space of the chromaticity response matrix.
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May 2024
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Accelerator Physics
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Abstract: As part of the Diamond-II upgrade project, the Dia- mond storage ring will be replaced with a new modified hybrid 6 bend achromat (M-H6BA) lattice, in which each existing arc section will be split in two to provide addi- tional mid-straights and thereby increase the ring capacity. Most insertion devices (IDs) currently in operation will be either retained or upgraded, and the new mid-straights al- low the total number of ID beamlines to be increased from 28 to 36. Therefore, it is important to investigate how the IDs will affect the equilibrium emittance and energy spread, along with their impact on the linear and nonlinear beam dynamics. Methods to compensate for their effects have been established, including a re-optimization of the octupole settings and identification of alternative working points. The impact of IDs on a lattice with high βx in the injection cell for better injection efficiency has also been studied. A kickmap approach has been used to model all IDs, including the APPLE-II IDs and APPLE-Knot with active shim wires. In this paper, the outcome of these in- vestigations will be presented.
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May 2024
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Accelerator Physics
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Open Access
Abstract: The Diamond-II storage ring upgrade will provide users with 1-2 orders of magnitude brightness increase over the existing Diamond facility, for which a quasi-transparent top-up injection scheme will be a key performance requirement [1]. The ring was originally designed to use a single-bunch aperture sharing injection scheme [2], in which short stripline kickers are used to kick the injected bunch into the storage ring's dynamic aperture but remaining weak enough to avoid kicking the stored bunch outside the acceptance. A modification to this scheme which implements a kick-and-cancel method [3] shows promise for the stored bunch. The kicker power supplies are thus required to provide a double-pulse with few-microsecond pulse spacing. This new method is expected to significantly improve the transparency and reduce the recovery time for the targeted bunch, along with minimizing transverse wakefield effects and any interactions with the transverse multibunch feedback.
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May 2024
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Accelerator Physics
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Abstract: Horizontal and vertical collimators will be installed in the Diamond-II storage ring to protect the ring components against undesired losses and radiation showers. Different loss mechanisms have been studied, including lifetime effects, RF trips, injection losses and kicker misfire. In this paper, we present the latest collimator layout and collimation efficiency. In addition, the risk of damage to the collimator blades has been studied for different materials using BDSIM.
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May 2024
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