Speaker
Description
High-luminosity electron–positron colliders such as SuperKEKB operate with high bunch currents and a large number of bunches in collision. Under these conditions, various beam instabilities can arise and limit beam performance. Investigating such phenomena requires diagnostic instruments capable of resolving beam properties on a bunch-by-bunch timescale. In particular, identifying bunch-dependent behavior associated with collective effects requires direct beam size measurements with nanosecond-level temporal resolution. We have developed a new ultra-fast X-ray beam size monitor for SuperKEKB based on synchrotron radiation from a bending magnet combined with coded-aperture optics and a silicon strip detector. The detector signals are digitized at 2.7 Gsps, providing vertical beam size information for each bunch in the main ring with a minimum time separation of approximately 4 ns. The system has been installed in the SuperKEKB main ring and used for beam observations during the 2025 and 2026 operation periods. Bunch-by-bunch beam size data have been successfully acquired under a variety of accelerator conditions, enabling detailed studies of beam size variations along bunch trains. This presentation reports the development and commissioning of this new monitor, together with beam observation results and their analysis, demonstrating the capability of this diagnostic system for studying bunch-dependent beam behavior at SuperKEKB.
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| Supervisor's name | Tadashi Koseki |
| Supervisor's email | tadashi.koseki@kek.jp |
| Paper submission software | MSWord |