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Description
Non-destructive beam diagnostics based on coherent radiation phenomena are essential for monitoring high-energy electron beams. Among these phenomena, Smith-Purcell radiation, emitted when a charged particle passes near a periodic metallic structure [1, 2]. It offers particular promise for beam parameter reconstruction, including bunch length and transverse profile. However, the practical implementation of Smith-Purcell radiation for beam diagnostics has traditionally been limited by the fabricating precision periodic targets.
In this work, we experimentally demonstrate the generation of Smith-Purcell radiation from high-energy electrons using two types of targets. First, measurements were performed with a freestanding metallic grating (the air-backed geometry) to establish a baseline for Smith-Purcell radiation. Second, we employed a 3D-printed dielectric lens equipped with the metallic strips to provide the necessary periodic boundary conditions (the dielectric-backed geometry). The measurements were carried out using a high-energy electron beam of the MT‑25 microtron (Dubna, Russia), and the emitted radiation from both configurations was characterized in terms of its spectral and angular properties.
A study of the effect's properties revealed that the Smith‑Purcell radiation peaks of the first order are detected at angles that shift toward larger values with increasing frequency. As the Smith‑Purcell radiation frequency increases, a narrowing of the amplitude distributions at half‑maximum is observed, while a decrease in the area and amplitude of the detected peaks is observed. The measured Smith-Purcell radiation observation angles agree with theoretical predictions within an 1°accuracy.