Abstract
Purpose
The 166.6 MHz superconducting radio frequency cavities have been proposed for High Energy Photon Source (HEPS) storage ring. HEPS is a 6 GeV, 200 mA diffraction-limited synchrotron light source to be built in Beijing. Higher-order modes (HOMs) excited in 166.6 MHz SRF cavities have to be sufficiently damped in order to prevent coupled-bunch instabilities and to limit parasitic mode losses.
Methods
A hybrid HOM damping scheme has been proposed. An enlarged beam pipe allows HOMs above beam pipe cutoff frequencies to propagate and subsequently be absorbed by dampers installed on the downstream beam pipe, while a petal-shaped coaxial structure extracts HOMs below beam pipe cutoff frequencies and subsequently damped by the specially designed coaxial filter.
Results
HOM damping in cavities has been demonstrated by 3D simulations. The impedance of HOMs has been successfully reduced to be lower than the coupled-bunch instability threshold. In addition, no hard barrier multipaction has been observed and acceptable heat loss is obtained.
Conclusions
In this paper, the hybrid HOM damping scheme has been demonstrated. Based on these studies, a prototype petal–loop structure and its associated filter are being fabricated.
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References
G. Xu, X.H. Cui, Z. Duan et al., Progress of lattice design and physics studies on the high energy photon source, in Proceedings of IPAC2018, Vancouver, BC, Canada
G. Xu et al., On-axis beam accumulation enabled by phase adjustment of a double- frequency RF system for diffraction-limited storage rings, in IPAC2016 (Busun, Korea) (2016). WEOAA02
P. Zhang et al., A 166.6 MHz superconducting RF system for the HEPS storage ring, in Proceedings of IPAC2017, MOPVA079, pp. 1049–1051
P. Zhang et al., The 166.6 MHz proof-of-principle SRF cavity for HEPS-TF, in Proceedings of SRF2017, TUPB034
D.M. Pozar, Microwave Engineering, 3rd edn. (Wiley, Hoboken, 2005)
CST Microwave, StudioÂ\(\textregistered \). Ver. 2017, CST AG, Darmstadt, Germany (2017)
H. Padamsee, RF Superconductivity for Accelerators, ch. 9.3, 2nd edn. (Wiley, Hoboken, 2008), p. 174
F. Marhauser et al., HOM damped 500MHz cavity design for 3rd generation SR sources, in Proceedings of PAC2001 (Chicago, USA, 2001), pp. 846–848
X. Hao et al., HOM damping with an enlarged beam tube for HEPS 166.6 MHz SC cavities, in 18th Int. Conf. on RF Superconductivity (SRF’17), Lanzhou, China, July 17–21, 2017, JACOW, Geneva, Switzerland (2018)
ABCI code. Ver. 12.5. http://abci.kek.jp/abci.htm. Accessed July 2017
G.V. Stupakov, Wake and impedance, in AIP Conference Proceedings (AIP, 2001)
L. Palumbo et al., Wake fields and impedance (2003). arXiv preprint arXiv:physics/0309023
T. Khabiboulline et al., Multipacting in the ILC 1.3 GHz HOM Coupler (2015)
Y. Li, Comparative simulation studies of multipacting in higher-order-mode couplers of superconducting rf cavities. Phys. Rev. Spec. Top. Accel. Beams 17(2), 022002 (2014)
M. Mario, Material properties for engineering analyses of SRF Cavities. Fermilab Specification
Ansys Workbench. https://support.ansys.com/portal/site/AnsysCustomerPortal. Accessed July 2017
Acknowledgements
I would like to thank Dr. Zhang Xinying, Dr. Zheng Hongjuan from RF Group of Accelerator Division in IHEP for discussing design options. This work has been supported by the HEPS-TF project funding.
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Hao, X., Li, Z., Meng, F. et al. A higher-order mode coupler design for HEPS 166.6 MHz superconducting accelerating cavities. Radiat Detect Technol Methods 3, 5 (2019). https://doi.org/10.1007/s41605-018-0082-y
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DOI: https://doi.org/10.1007/s41605-018-0082-y