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33 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3, 4 [Next/Last]

Instruments / Technical Area	Publication Details	Published
Insertion Devices	Impact of insertion devices on Diamond-II lattice B. Singh , H. Ghasem , J. Kallestrup , T. Olsson , R. Fielder , I. Martin IPAC2022 DOI: 10.18429/JACoW-IPAC2022-MOPOTK037 Open Access Show Abstract ▼ Abstract: The DIAMOND-II lattice is based on the ESRF-EBS cell, with the centre dipole replaced by a (chromatic) mid-straight, and a -I transformer, higher order achromat (HOA) & dispersion bumps to control the nonlinear dynamics. The majority of insertion devices currently on operation in Diamond will be either retained or upgraded as part of the Diamond-II program, and the new mid straights allow the total number of ID beamlines to be increased from 28 to 36.Therefore, it is important to investigate how IDs will affect the emittance, energy spread and linear and nonlinear beam dynamics. The kickmap approach has been used to model all IDs, including APPLE-II and APPLE-II Knot with active shim wires. In this paper, the outcome of these investigations will be presented and discussed.	Jul 2022
Accelerator Physics	Studies of transverse coupled-bunch instabilities from resistive-wall and cavity higher order modes for Diamond-II S. Wang , H.-C. Chao , R. Fielder , I. P. S. Martin , T. Olsson IPAC2022 DOI: 10.18429/JACoW-IPAC2022-WEPOMS010 Open Access Show Abstract ▼ Abstract: The transverse coupled-bunch instabilities from resistive-wall impedance and main cavity higher order modes (HOMs) are studied for the Diamond-II storage ring. The growth rates of all the coupled-bunch modes are calculated using both the results from tracking simulations and analytic formula, which show a good consistency. The instability threshold from the resistive-wall impedance is estimated and verified by simulation. The impact of the main cavity HOMs is studied in a similar way, and the results show instabilities from HOMs are much smaller than that from resistive-wall impedance.	Jul 2022
Insertion Devices	Impact of IDS on the Diamond storage ring and application to Diamond-II R. Fielder , B. Singh IPAC2022 DOI: 10.18429/JACoW-IPAC2022-THPOPT048 Open Access Show Abstract ▼ Abstract: When investigating the effect of insertion devices (IDs) on storage ring operations, it is not possible to simulate all of the large number of gap, phase and field settings that are available. This can be of particular concern for transient effects in IDs that are moved frequently, or APPLE-II devices which may use many different polarisation states. We therefore present measurements of the impact of selected IDs on various parameters in the current Diamond storage ring including orbit distortion, tunes, chromaticity and emittance, and assess the expected impact when applied to the Diamond-II lattice.	Jun 2022
Accelerator Physics	Commissioning simulations for the Diamond-II upgrade H.-C. Chao , R. Fielder , J. Kallestrup , B. Singh , I. Martin IPAC2022 DOI: 10.18429/JACoW-IPAC2022-THPOPT016 Open Access Show Abstract ▼ Abstract: The Diamond-II storage ring, compared to Diamond, improves the natural beam emittance from 2.7 nm to 160 pm and the beam energy from 3 to 3.5 GeV. The number of straight sections is also doubled from 24 to 48 thanks to the modified hybrid six-bend-achromat lattice. To reduce the impact on the existing science program, the dark time period must be minimised. To assist in this aim, storage ring commissioning simulations have been carried out to predict and resolve possible issues. These studies include beam commissioning starting from on-axis first-turn beam threading up to beam based alignment and full linear optics correction with stored beam. The linear optics corrections with insertion devices are also included. The machine characterisations at different stages are compared. Considerations on realistic chamber limitations, error definitions and some commissioning strategies are also discussed.	Jun 2022
Accelerator Physics	Single bunch instability studies with a new impedance database for Diamond-II Richard Fielder , Hung-Chun Chao , Siwei Wang IPAC2022 DOI: 10.18429/JACoW-IPAC2022-WEPOMS011 Open Access Show Abstract ▼ Abstract: We present an updated impedance database for the Diamond-II storage ring, along with an analysis of single bunch instabilities and thresholds based on particle tracking simulations using Elegant. Various cases with different chromaticity, insertion device parameters and harmonic cavity settings are studied, and the effects on the microwave instability, bunch lengthening and phase shifts are simulated and compared with analytic formulae. Preliminary results show that the single-bunch instability thresholds are above requirements for a uniform fill, and with inclusion of a harmonic cavity the longitudinal and transverse instability thresholds can also satisfy requirements for a hybrid fill.	Jun 2022
Magnets	Operational use of pinger magnets to counter stored beam oscillations during injection at Diamond Light Source R. Fielder , I. P. S. Martin , M. Apollonio IPAC2021 DOI: 10.18429/JACoW-IPAC2021-MOPAB128 Open Access Show Abstract ▼ Abstract: Diamond uses a four kicker bump injection scheme. Due to a variety of factors it has become more difficult to perfectly match the four kicks while maintaining injection efficiency, resulting in some disturbance to the stored beam during top-up. This has consequences for beamlines which may see degraded beam quality during injections. A gating signal is provided, but this is not appropriate for all experiments, and in any case ideally would not be required. The disturbance to the stored beam can be partly controlled using the existing diagnostic pinger magnets installed in the storage ring. We present here a comparison of different compensation schemes and tests with beamlines, along with initial experiences operating during user beam time. Use of these magnet also provides proof of principle for any future, purpose-built compensation kickers.	Sep 2021
Mechanical Engineering	Construction of an impedance model for Diamond-II R. T. Fielder , T. Olsson IPAC2021 DOI: 10.18429/JACoW-IPAC2021-MOPAB127 Open Access Show Abstract ▼ Abstract: Impedance models for accelerators have traditionally been presented in a static form, usually as tables or spreadsheets which must be read manually. As part of the Diamond-II upgrade work, we have developed an impedance model using a lattice structure. This allows more direct integration with simulation codes while keeping important information easily human readable. We present here a description of this implementation method, along with an overview of the Diamond-II impedance model derived from the latest engineering design.	Aug 2021
Magnets	Reduction of stored beam oscillations during injection at Diamond Light Source R. T. Fielder , M. Apollonio , R. Bartolini , C. Bloomer , I. P. S. Martin IPAC2019 DOI: 10.18429/JACoW-IPAC2019-WEPMP042 Open Access Show Abstract ▼ Abstract: At Diamond injection is performed by means a of a four kicker off-axis system, relying on a perfect timing and amplitude setting to produce a closed bump. Ageing of some of the kicker vessel components has progressively spoiled the performance of the system, causing oscillations in the stored beam. Various schemes to control these oscillations have been considered including introducing an additional compensating kicker, and installing a non-linear injection kicker. Results of simulations analysing these schemes are presented, along with measurements taken in the storage ring using an existing pinger magnet. The effects of the reduction on the quality of beam seen by beamlines is also considered.	Jun 2019
Magnets Optics	Characterization of the double-double bend achromat lattice modification to the Diamond Light Source storage ring I. P. S. Martin , M. Apollonio , R. T. Fielder , Ei. Koukovini-Platia , B. Singh , R. Bartolini Physical Review Accelerators And Beams 21 DOI: 10.1103/PhysRevAccelBeams.21.060701 Open Access Show Abstract ▼ Abstract: The Diamond storage ring has recently been modified by replacing one of the original double bend achromat (DBA) cells with a double-DBA (DDBA) cell. The new cell marks a fundamental break to the machine symmetry, and the final engineered solution shares many design features in common with modern multi-bend achromat cells. In this paper we review the impact that the modification has had on the linear and nonlinear optics, collective effects, and overall performance. Where appropriate, comparison to model predictions are also made.	Jun 2018
Controls	Online multi objective optimisation at diamond light source M. Apollonio , R. Bartolini , R. T. Fielder , I. P. S. Martin , G. Henderson , J. Rogers 9th International Particle Accelerator Conference DOI: 10.18429/JACoW-IPAC2018-WEPAF054 Open Access Show Abstract ▼ Abstract: At Diamond Light Source we have developed an Optimization Package currently used online to improve the performance of the machine, usually measured in terms of lifetime, injection efficiency or beam disturbance at injection. The tool is flexible in that control variables in order to optimise objectives (or their functions) can be easily specified by means of EPICS process variables (PV), making it suitable for virtually any sort of optimization. At present three different algorithms can be used to perform optimizations in a multi-objective fashion: Multi-Objective Genetic Algorithm (MOGA), Particle Swarm Optimizer (MOPSO) and Simulated Annealing (MOSA). We present a series of tests aimed at characterizing the algorithm as well as improving the performance of the machine itself.	Jun 2018

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