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The design of future circular colliders will push beam currents and luminosities to unprecedented levels. Beam halo surrounding the main beam can deposit enough energy to melt conventional metal collimators and damage downstream components within a short time. Such damage was already observed during SuperKEKB commissioning [1]. A possible solution is to use Compton scattering to deflect halo electrons, effectively using a laser as a non-material collimator [2].
Previous studies have explored laser-Compton scattering for beam-intensity control in FCC-ee and laboratory tests at FACET-II [3,4]. In this work, we focus on laser-based halo collimation, aiming to selectively scatter halo electrons while leaving the beam core largely unaffected. Using SLAC FACET-II laser parameters, we estimate the single-electron scattering probability and outline the planned E344 proof-of-concept experiment, where an annular laser focus is used to target the beam halo. Beyond this near-term test, we discuss the feasibility of reusing laser pulses in an optical cavity, which is essential for improving energy efficiency and scaling the concept toward high-repetition-rate future electron storage rings.
[1] S. Terui et al., “Collimator challenges at SuperKEKB and their countermeasures using nonlinear collimator,” Phys. Rev. Accel. Beams 27, 081001 (2024). https://doi.org/10.1103/PhysRevAccelBeams.27.081001
[2] F. Zimmermann, “New final focus concepts at 5 TeV and beyond,” AIP Conf. Proc. 472, 103–117 (1999). https://doi.org/10.1063/1.58898
[3] F. Zimmermann and T. O. Raubenheimer, “Controlling e+/e− circular collider bunch intensity by laser Compton scattering,” in Proc. IPAC’22, Bangkok, Thailand, pp. 1695–1698 (2022). https://doi.org/10.18429/JACoW-IPAC2022-WEPOST010
[4] C. Munting, P. Kicsiny, E. Barbi, N. Gonzalez, S. Gessner, and I. Drebot, “Laboratory Tests of Laser Control of Electron Beams for Future Colliders,” arXiv:2601.19865 [physics.acc-ph] (2026). https://arxiv.org/abs/2601.19865
