| Paper | Title | Page |
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| MO3B2 | Beam Dynamics Using Superconducting Passive Harmonic Cavities with High Current per Bunch | 14 |
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| In 4th generation synchrotron light sources, harmonic cavities (HCs) are critical components needed to achieve the required performance. They provide longer bunches, which helps to reduce statistical effects (intra-beam scattering and Touschek effect). In "timing" modes, where the bunch spacing is larger than in conventional modes and the number of particles per bunch is higher, this need is even greater. In this article, we present the beam dynamics in the high current per bunch regime and how it interacts with the single bunch collective effects. In particular, a dipole-quadrupole instability is observed above the microwave threshold and a coupling between the dipole and cavity modes is shown to limit bunch lengthening at low current. The effective gain from the use of HCs in terms of lifetime, emittance, and energy spread is also discussed. | ||
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Slides MO3B2 [1.529 MB] | |
| DOI • | reference for this paper ※ doi:10.18429/JACoW-FLS2023-MO3B2 | |
| About • | Received ※ 13 August 2023 — Revised ※ 15 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023 | |
| Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |
| MO3B3 | Bunch-lengthening RF System Using Active Normal-conducting Cavities | 18 |
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Bunch lengthening using a double RF system (fundamental + harmonic cavities) is essential in preserving the extremely low emittance in fourth and future generation synchrotron light rings. Recent studies have revealed that, in many cases, unstable beam motions, as so-called "mode-0" and "periodic transient beam loading" instabilities, prevent from reaching the optimum bunch lengthening condition with low and high beam current, respectively, even in symmetric filling patterns. While reducing the R/Q is beneficial for the latter, it will worsen the former. To achieve an efficient bunch lengthening system, we proposed a promising solution based on a powered TM020-type harmonic cavity with RF feedbacks (RF-FBs)*, as reported at FLS2018. Based on this concept, we are developing both fundamental and harmonic cavities using the TM020 resonant mode**, a kicker cavity having a bandwidth >5MHz***, bunch-phase monitor (BPhM) and RF-FBs. In this presentation, we describe our overall bunch lengthening system including cavity and BPhM designs. We also present particle tracking simulation results demonstrating that the bunch lengthening limitations can be alleviated by means of direct RF-FBs****.
* N. Yamamoto et al., PRAB 21, 012001, 2018. ** T. Yamaguchi et al., accepted in NIM A. *** D. Naito et al, IPAC2021, MOPSB331, 2021. **** N. Yamamoto et al., IPAC23, WEPL161, 2023. |
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Slides MO3B3 [2.655 MB] | |
| DOI • | reference for this paper ※ doi:10.18429/JACoW-FLS2023-MO3B3 | |
| About • | Received ※ 22 August 2023 — Revised ※ 23 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023 | |
| Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |