| Paper | Title | Page |
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MOPB006 |
Narrowband Impedance Studies in the HEPS Storage Ring | |
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| The High Energy Photon Source (HEPS) is a fourth-generation synchrotron radiation facility with design beam emittance of less than 60 pm. Impedance modeling is an important subject due to the adopted small beam pipe as well as the tight requirements from beam collective effects. Narrowband impedances can be generated by the discontinuity of the vacuum chamber or the finite conductivity of the beam pipe. The coupled bunch instabilities caused by the narrowband impedances could restrict the beam current or perturb the synchrotron radiations. In this paper, the narrowband impedances in the HEPS storage ring are investigated element by element. Their influence on the beam instability and heat load are discussed. | ||
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| MOPB014 | Development of a Vlasov Solver for Arbitrary Sub-optimal Lengthening Conditions in Double-RF System | 34 |
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| Solving Vlasov equation is a classic method for analyzing collective beam instabilities. Considering longitudinal impedance and the nonlinear longitudinal potential well, we developed a new Vlasov solver which can be used to study the transverse mode-coupling instability under the arbitrary sub-optimal lengthening and the optimal lengthening conditions in a double-RF system. Several different techniques to deal with the radial direction of longitudinal phase space have been tested. Numerical discretization method is selected in this paper. The development of the solver is presented in details here. Benchmarks and crosscheck of the solver have been made and presented as well. | ||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB014 | |
| About • | Received ※ 30 June 2023 — Revised ※ 08 July 2023 — Accepted ※ 11 July 2023 — Issued ※ 21 August 2024 | |
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| MOPB028 | Investigation on the Trapped Modes of CPMU at HEPS | 62 |
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| The Cryogenic Permanent Magnet Undulator (CPMU) is a crucial component in synchrotron radiation sources. Due to the small magnet gap of CPMU, the interaction between the beam and its surroundings is strong, which can result in a significant contribution to coupling impedance. In this work, the influence of CPMU on coupling impedance was investigated using wakefield and eigenmode solvers. The results indicated that some of the transverse impedance resonances in CPMU were much stronger than the impedance threshold determined by synchrotron radiation damping, which could cause vertical beam instability. To address this issue, different types of damping materials were investigated through simulations to suppress the resonances. | ||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SAP2023-MOPB028 | |
| About • | Received ※ 10 July 2023 — Revised ※ 11 July 2023 — Accepted ※ 12 July 2023 — Issued ※ 01 October 2023 | |
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TUPB028 |
Studies of Ion Effects in the Heps Storage Ring | |
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| In the fourth generation synchrotron radiation light source, the accelerator design aims to deliver low-emittance electron beams¿to maximize the brightness of the photon beams. This brings new challenges to maintain low emittance with potential collective instabilities. One particular source of concern is the ion-driven instability, which can be induced by ionization of the residual gas by the circulating electron beam. The ion effects in the HEPS storage ring are estimated by both analytical formula and macro-particle simulations. More detailed simulations considering actual filling patterns and vacuum conditions are performed. The results indicate that at the design beam current, the ions will be over-focused due to the very high beam densities, and the beam will not be perturbed by the ions. This is somewhat different from widely accepted understanding that the coupled motion between the beam and the ions is inversely proportional to the beam size and is typically proportional to the average beam current and residual gas pressure. In this paper the results of the instability amplitude and beam emittance growth, the variation process of trapped ion density is presented. | ||
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