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We report on vacuum testing of an optical‑fibre scanner for measuring transverse profiles and divergence of low‑intensity electron beams at the microtron TPU (5.7 MeV). The measurements were performed with a beam charge of 100 pC using two fibre materials of identical thickness (1 mm): PMMA (polymethyl methacrylate, also known as Plexiglas or organic glass) and a scintillating optical fibre. Unlike traditional methods, where light trapped in the fibre is recorded at its end, we detect emission from the fibre region intersected by the beam, perpendicular to the fibre axis. This radiation is attributed to luminescence of the fibre material.
Transverse beam profiles and divergence angles obtained with the fibre scanner are compared against optical transition radiation data, which serves as an independent reference method. The divergence is determined by analysing beam size variations at three measurement points separated by a known drift distance – a standard technique in beam diagnostics.
The optical‑fibre scanner demonstrates high potential for diagnostics of low‑intensity beams in accelerators with high electromagnetic or radiation interference. Its ability to provide both transverse profile and divergence data makes it particularly valuable for beam tuning and optimization in modern accelerator facilities, especially in environments where conventional methods (wire scanners, luminescent screens) face significant limitations.
This research was supported by the Russian Ministry of Science and Higher Education, project No. FSWW-2026-0046.