Author: Chao, H.C.
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TUPOMS031 Fill Pattern for Reducing Transient Beam Loading and Ion-Trapping in the Diamond-II Storage Ring 1483
 
  • T. Olsson, H.C. Chao
    DLS, Oxfordshire, United Kingdom
 
  The Diamond-II upgrade will replace the existing Diamond storage ring with a multibend achromat lattice providing higher brightness to the users by reducing the emittance and increasing the beam energy. The new storage ring will require a harmonic cavity that lengthens the bunches to increase the Touschek lifetime as well as mitigate instabilities and suppress the emittance blow up from intrabeam scattering. It is expected that the ring will have to operate with gaps in the fill pattern for ion-clearing, but that will lead to transient beam loading resulting in reduced bunch lengthening. The length and occurrence of the gaps therefore have to be determined as a trade-off between the requirements for transient beam loading and ion-trapping. This paper presents simulations of both effects for the Diamond-II storage ring to find an optimal fill pattern.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS031  
About • Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 24 June 2022
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TUPOMS033 Diamond-II Storage Ring Developments and Performance Studies 1491
 
  • I.P.S. Martin, H.C. Chao, R.T. Fielder, H. Ghasem, J. Kallestrup, T. Olsson, B. Singh, S.W. Wang
    DLS, Oxfordshire, United Kingdom
 
  The Diamond-II project includes a replacement of the existing double-bend achromat storage ring with a modified hybrid 6-bend achromat, doubling the number of straight sections and increasing the photon beam brightness by up to two orders of magnitude*. The design and performance characterisation of the new storage ring has continued to progress, including a switch to an aperture-sharing injection scheme, freezing the magnet layout, studying the impact of IDs, developing a commissioning procedure and investigating collective effects. In this paper we present an overview of these studies, including final performance estimates.
*Diamond-II Technical Design Report, Diamond Light Source Ltd.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS033  
About • Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 27 June 2022
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WEPOMS010 Studies of Transverse Coupled-Bunch Instabilities from Resistive-Wall and Cavity Higher Order Modes for Diamond-II 2253
 
  • S.W. Wang, H.C. Chao, R.T. Fielder, I.P.S. Martin, T. Olsson
    DLS, Oxfordshire, United Kingdom
 
  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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS010  
About • Received ※ 06 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 05 July 2022  
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WEPOMS011 Single Bunch Instability Studies with a New Impedance Database for Diamond-II 2257
 
  • R.T. Fielder, H.C. Chao, S.W. Wang
    DLS, Oxfordshire, United Kingdom
 
  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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS011  
About • Received ※ 07 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 22 June 2022
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THPOPT016 Commissioning Simulations for the DIAMOND-II Upgrade 2598
 
  • H.C. Chao, R.T. Fielder, J. Kallestrup, I.P.S. Martin, B. Singh
    DLS, Oxfordshire, United Kingdom
 
  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.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOPT016  
About • Received ※ 19 May 2022 — Accepted ※ 15 June 2022 — Issue date ※ 15 June 2022  
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