Speaker
Description
We report measurements of coherent optical transition radiation extending into the visible spectrum produced by ultrashort relativistic electron bunches at a dielectric boundary. The measured optical spectra exhibit quadratic charge scaling consistent with optical-frequency coherence arising from single-digit femtosecond longitudinal structure within the electron bunch. The measured spectral envelope is reproduced by a coherent transition radiation model, yielding a characteristic longitudinal feature scale of τFWHM ≈ 1.2 fs. In contrast to prior visible COTR observations associated with FEL interactions or optically modulated microbunching, the emission observed here is generated through strong longitudinal compression in an RF linac without undulators or external optical modulation. These results demonstrate optical-frequency superradiant boundary emission generated through RF bunch compression and provide a pathway toward coherent optical sources and phase-sensitive measurements.
| Working group | WG6 |
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