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Near-infrared noise in intense electron bunches

Sergei Kladov1,*, Sergei Nagaitsev2, Young-Kee Kim1, Daniel R. Broemmelsiek3, Zhirong Huang4, Jonathan Jarvis3, Alex H. Lumpkin3, Jinhao Ruan3, Andrea Saewert3 et al.

Randy M. Thurman-Keup3

  • *Contact author: kladov@uchicago.edu
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Phys. Rev. Accel. Beams 29, 012801 – Published 23 January, 2026

DOI: https://doi.org/10.1103/c3fd-g5mn

Abstract

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 compare the shot-noise model with experimental observations using bandwidth-filtered near-infrared optical transition radiation (OTR) photodiode signals, where the transverse bunch size is much larger than the OTR wavelength of interest. The relativistic electron bunch (γ≈50) parameters are close to those proposed for the coherent electron cooler in the electron-ion collider (EIC) project. Preliminary feasibility experiments were conducted, and the noise factors are presented, supported by particle tracking. No major density fluctuations or effective cooling rate decrease were revealed for EIC CEC design parameters. Additionally, longitudinal-space-charge-induced microbunching for the chicane-compressed bunch was observed with coherent OTR enhancements up to 100 times, providing further calibration of the measurement method.

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Phys. Rev. Accel. Beams 29, 012801– Published 23 January, 2026
  • Received 10 February 2025
  • Accepted 18 December 2025
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