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MO3B1 |
Obtaining Picosecond X-ray Pulses on 4th Generation Synchrotron Light Sources | |
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| Through the 2-frequency crab cavity scheme, fourth generation storage ring light sources offer a unique opportunity to produce intense short X-ray pulses that are ideal for time-resolved user experiments. The short pulses and the high brightness photon beams are simultaneously available at all beamlines in a fully compatible operation mode. Owing to the small momentum compaction factor characteristic in fourth generation storage rings, the vertical emittance contribution due to the coupling between the longitudinal and transverse planes by the crab cavities is greatly reduced, which allows reaching short pulse duration with little constraint on the betatron tunes. We propose to use half-integer aharmonic cavity to simultaneously produce bunch lengthening and shortening in the bunch train to facilitate compatible operation of the normal and short-pulse beams. A concrete case study based on the Advanced Photon Source Upgrade (APS-U) lattice is used to demonstrate the system configuration, requirements, and beam performances. | ||
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Slides MO3B1 [1.817 MB] | |
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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 | |
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| 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 | |
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| MO3B4 | Generating High Repetition Rate X-ray Attosecond Pulses in SAPS | 22 |
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| Attosecond, which refers to 10-18 seconds, is the timescale of electron motion within an atom. Accurate observation of electron motion helps deepen the understanding of microscopic quantum processes such as charge transfer in molecules, wave packet dynamics, and charge transfer in organic photovoltaic materials. To meet the needs of relevant research, the South Advanced Photon Source (SAPS), currently in the design phase, is considering the construction of an attosecond beamline. This paper presents relevant research on achieving high-repetition-rate coherent attosecond pulses on the fourth-generation storage ring at SAPS. Realizing attosecond pulses in a storage ring requires femtosecond to sub-femtosecond-level longitudinal modulation of the beam, and the modulation scheme needs to consider multiple factors to avoid a significant impact on other users. The study shows that with high-power, few-cycle lasers, and advanced beam modulation techniques, the photon flux of attosecond pulses can be significantly enhanced with a minimal impact on the brightness of synchrotron radiation. Adopting high-repetition-rate lasers and precise time delay control, the repetition rate of attosecond pulses at SAPS can reach the megahertz level. Currently, the design wavelength range for attosecond pulses covers the water window (2.3-4.4 nm), which is "transparent" to water but strongly absorbed by elements constituting living organisms. This wavelength range has significant application value in fields such as biology and chemistry. | ||
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Slides MO3B4 [3.400 MB] | |
| DOI • | reference for this paper ※ doi:10.18429/JACoW-FLS2023-MO3B4 | |
| About • | Received ※ 23 August 2023 — Revised ※ 24 August 2023 — Accepted ※ 31 August 2023 — Issued ※ 02 December 2023 | |
| Cite • | reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml) | |