Tsakanian, A.; Velez, A.; Sharples-Milne, E.; Knobloch, J.: Design of HOM Damped Multi-Cell SRF Cavities for CW Operation in High Current Storage Rings. IEEE Transactions on Applied Superconductivity 35 (2025), p. 3501116/1-16
10.1109/tasc.2025.3554959
Open Access Version
Abstract:
Presently, SRF systems for high-current storage rings are generally limited to low-frequency, moderate voltage, single-cell cavities. For a new class of cavities to be used in longitudinal beam phase-space manipulation, high-voltage third harmonic multi-cell cavities are required, resulting in very challenging impedance considerations and higher-order mode powers of the order of several kW per cavity. Thus, the cavity design requires far more attention on the HOM spectrum to be off-resonance with circulating beam harmonics. Special techniques are developed to analyze the HOM spectrum and damping beyond the standard frequency range laying typically at a few GHz as required by the VSR Demo project. Within the presented work, a 4-cell 1.5 GHz cavity is designed including end-groups with multi-waveguide damping for a space-saving design capable of handling over 2.5 kW of HOM power per cavity. These cavities are designed for high-voltage operation with beam currents of at least 300 mA. Prototype systems are now in production. This paper provides an overview on the advanced techniques for SRF cavity design and their application to tailoring the HOM spectrum and its application for the VSR Demo project.