| Paper | Title | Other Keywords | Page |
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| SUPCAV011 | Third Harmonic Superconductive Cavity for Bunch Lengthening and Beam Lifetime Increase of Sirius Synchrotron Light Source | cavity, electron, synchrotron, beam-loading | 37 |
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| A passive third harmonic superconducting cavity is to be installed at Sirius’ 4th generation synchrotron light source in order to lengthen the bunches and improve beam lifetime, which is dominated by Touschek scattering. A study of optimal bunch lengthening is carried on by enforcing a flat potential well around the synchronous electron and the results are compared to the passive operation case for several shunt impedances and unloaded quality factors based on known operating cavities. To determine the new bunch shape due to beam loading and its length, a full consistent approach is followed by setting the harmonic voltage amplitude equal to the optimum value and calculating the required detune, harmonic phase and synchronous phase for an initial complex form factor, allowing the new distribution to be obtained by an iterative process. For each case analyzed, energy acceptance is obtained through the separatrix in the phase plane and the corresponding lifetime increase ratio is calculated. Input power required after the addition of the harmonic cavity is then estimated. | |||
| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-SUPCAV011 | ||
| About • | Received ※ 20 June 2021 — Accepted ※ 15 November 2021 — Issue date ※ 21 March 2022 | ||
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| MOPCAV010 | Design of a HOM-Damped 166.6 MHz Compact Quarter-Wave β=1 Superconducting Cavity for High Energy Photon Source | cavity, HOM, superconducting-cavity, photon | 278 |
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Funding: This work was supported by High Energy Photon Source, a major national science and technology infrastructure in China. Superconducting cavities with low RF frequencies and heavy damping of higher order modes (HOM) are desired for the main accelerator of High Energy Photon Source (HEPS), a 6 GeV synchrotron light source promising ultralow emittance currently under construction in Beijing. A compact 166.6 MHz superconducting cavity was proposed adopting a quarter-wave β=1 geometry. Based on the successful development of a proof-of-principle cavity, a HOM-damped 166.6 MHz compact superconducting cavity was subsequently designed. Ferrite damper was installed on the beam pipe to reduce HOM impedance below stringent threshold of coupled-bunch instabilities. Being compact, RF field heating on the cavity vacuum seal was carefully examined against quenching the NbTi flange. The cavity was later dressed with helium vessel and the tuning mechanism was also realized. Excellent RF and mechanical properties were eventually achieved. Finally, the two-cavity string was designed to ensure smooth transitions among components and proper shielding of synchrotron light. This paper presents a complete design of a fully dressed HOM-damped low-frequency β=1 superconducting cavity for HEPS. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-MOPCAV010 | ||
| About • | Received ※ 20 June 2021 — Accepted ※ 21 August 2021 — Issue date ※ 14 April 2022 | ||
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| TUPFDV007 | Surface Impedance of Nb3Sn and YBa2Cu3O7-δ in High Magnetic Fields | cavity, radio-frequency, framework, collider | 416 |
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Funding: This work has been partially carried out within the framework of the EUROfusion consortium, funding from the Euratom research and training programme 2014-18 and 2019-20 under grant agreement No 633053 New potential rf applications of superconductors emerged with the need to operate in high dc magnetic fields (up to 16 T) where vortex motion dictates the response: the beam screen coating of the Future Circular Collider (FCC) [1] and haloscopes, i.e. rf cavities for the axions detection [2]. However, very few data are available in the required regimes. We present in this work measurements of the surface impedance Z up to 12 T on bulk Nb3Sn and YBCO thin films grown by different techniques. The measurements are performed with a dielectric loaded resonator operating at 15 GHz. We obtained the vortex motion resistivity and extracted the high frequency vortex motion parameters [3]: the depinning frequency, the flux-flow resistivity and the pinning constant, as well as their temperature and field dependences. Substantial differences are highlighted in the high frequency pinning properties of the studied materials, providing useful information on possible improvements in view of applications. A comparison with the results obtained in the microwave frequency range at lower fields (up to 1 T) is given. [1] S. Calatroni, IEEE Trans. Appl. Supercond., vol. 26 p. 3500204, 2016. [2] D. Alesini et al., Phys. Rev. D, vol. 99, p. 101101, 2019. [3] J.I. Gittleman and B. Rosenblum, Phys. Rev. Lett., vol. 16, p.734, 1966. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-TUPFDV007 | ||
| About • | Received ※ 21 June 2021 — Accepted ※ 21 August 2021 — Issue date ※ 02 January 2022 | ||
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| WEPCAV014 | HOM Damper Design for BNL EIC 197 MHz Crab Cavity | cavity, HOM, GUI, cryomodule | 624 |
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Funding: The work is supported by by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. The interaction region (IR) crab cavity system is a special RF system to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point (IP) for BNL EIC. There will be six crab cavities, with four 197 MHz crab cavities and two 394 MHz crab cavities, installed on each side of the IP in the proton/ion ring, and one 394 MHz crab cavity on each side of the IP in the electron ring. Both rings share identical 394 MHz crab cavity design to minimize the cost and risk in designing a new RF system, and it will be scaled from 197 MHz crab cavity. In this paper, the HOM damper design for 197 MHz crab cavity is introduced. |
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| DOI • | reference for this paper ※ doi:10.18429/JACoW-SRF2021-WEPCAV014 | ||
| About • | Received ※ 22 June 2021 — Revised ※ 17 October 2021 — Accepted ※ 17 December 2021 — Issue date ※ 07 April 2022 | ||
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