This article investigates electron bunch density fluctuations in the 1 - 10 μm wavelength range, focusing on their impact on coherent electron cooling (CEC) in hadron storage rings. In this study, we thoroughly compare the shot-noise model with experimental observations of optical transition radiation (OTR) generated by a relativistic electron bunch (γ≈ 50), transiting an Aluminium metal surface. The bunch parameters are close to those proposed for a stage in an Electron-Ion Collider (EIC), where the bunch size is much larger than the OTR wavelength being measured. Here we present measurements and particle tracking results of both the low-level noise for the EIC bunch parameters and longitudinal space-charge-induced microbunching for the chicane-compressed bunch with coherent OTR enhancements up to 100 times in the various bandwidth-filtered near-infrared (NIR) OTR photodiode signals. We also discuss the corresponding limitations of the OTR method.
@article{arxiv.2412.13482,
title = {Near-Infrared noise in intense electron bunches},
author = {Sergei Kladov and Sergei Nagaitsev and Alex H. Lumpkin and Jinhao Ruan and Randy M. Thurman-Keup and Andrea Saewert and Zhirong Huang and Young-Kee Kim and Daniel R. Broemmelsiek and Jonathan Jarvis},
journal= {arXiv preprint arXiv:2412.13482},
year = {2026}
}