| Paper | Title | Page |
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| TUPAB053 | Design Progress of ALS-U 3rd-Harmonic Cavity | 1481 |
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Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 A higher-harmonic rf cavity (HHC) system is required in the ALS-U storage ring to lengthen the bunches, reduce intrabeam-scattering effects, and improve Touschek beam lifetime. A 3rd harmonic, normal conducting, passive-cavity system has been chosen based on beam-dynamics requirements and cost considerations. We have explored two options for ALS-U 3HC system: a high-R/Q re-entrant cavity with waveguide HOM dampers, and a low-R/Q system with two elliptical cavities and HOM beam line absorbers. In this paper, we present the recent progress on the cavity design and related beam dynamics studies. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB053 | |
| About • | paper received ※ 19 May 2021 paper accepted ※ 11 June 2021 issue date ※ 14 August 2021 | |
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| WEPAB081 | The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project | 2779 |
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| Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. Like other 4th-generation light source machines, the ALS-U multiple-bend achromat storage-ring (SR) is potentially sensitive to beam-coupling impedance effects. This paper presents the SR broad-band impedance budget in both the longitudinal and transverse planes. In our modeling we follow the commonly accepted approach of separating the resistive-wall and the geometric parts of the impedance, the former being described by analytical formulas and the latter obtained by numerical electromagnetic codes (primarily CST Studio software) assuming perfectly conducting materials. We discuss the main sources of impedance. Results of our analysis are the basis for the single bunch instability study and would feedback on the design of critical vacuum components. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB081 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 20 August 2021 | |
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| WEPAB082 | Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project | 2783 |
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| As the broad-band impedance modeling and the vacuum chamber design of the new Advanced Light Source storage ring (ALS- U) reach maturity, we report on progress in single-bunch collective effects studies. A pseudo-Green function wake representing the entire ring was earlier obtained by numerical and analytical methods. Macroparticle simulations using the computer code "elegant" and this wake function are used to determine the instability thresholds for longitudinal and transverse motion. We consider various operating conditions, such as without/with higher-harmonic RF cavities, zero/finite linear chromaticity, and without/with a transverse bunch-by-bunch feedback system. Results show enough margin for the broadband impedance budget when the single-bunch instability thresholds are compared with the design bunch charge. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB082 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 12 August 2021 | |
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