Higher-order-mode damping coupler for beam instability suppression

• Published in: Japanese Journal of Applied Physics Vol. 26; no. 10; pp. 1733 - 1739
• Main Authors: IZAWA, M, KOBAYAKAWA, H, SAKANAKA, S, TOKUMOTO, S
• Format: Journal Article
• Language: English
• Published: Tokyo Japanese journal of applied physics 01-10-1987
• Subjects: Electromagnetism; electron and ion optics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Physics; Radiation by moving charges; Storage ring; Synchrotron radiation
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/jjap.26.1733

The effects of a higher-order-mode damping coupler on coupled-bunch instabilities were studied in the Photon Factory storage ring. It was inserted in the RF accelerating cavity in order to suppress higher-order modes, especially the TM011-like mode excitation which causes a longitudinal coupled-bunch instability. Threshold currents of this beam instability were measured before and after insertion. The results showed the obvious damping effects: instability thresholds were largely improved. No practical problems, such as discharge or vacuum trouble were observed during operation with a high-current beam and a single-bunched beam.