Laser Control and Collimation of Particle Beams for Higgs Factories

August 4, 2026

Laser Control of Particle Beams

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Zimmerman, F. New final focus concepts at 5 TeV and beyond. Eighth Advanced Accelerator Concepts Workshop. 1998.

F. Zimmermann, T. Raubenheimer IPAC 2022 https://accelconf.web.cern.ch/ipac2022/papers/wepost010.pdf

I. Drebot, et. al IPAC 2023 https://doi.org/10.18429/JACoW-IPAC2023-MOPA074

Laser collimation of Particle Beams for Multi-TeV Linear Collider

Shot-by-shot control of electron bunch intensity in FCC.

“A Ti:sapphire J-class kHz laser system is ready to be built today [7–9]. Specifically, we consider a laser system operating with 1 J pulses at 3 kHz (the revolution frequency), with an average power of 3 kW, which translates to the same average laser power as for LBNL’s k-BELLA initiative (3 J at 1 kHz) [10].”

E320 provides the experimental infrastructure

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We utilize the E320 infrastructure at FACET-II to provide an R&D platform for:

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• Bunch-to-bunch laser intensity control.
• Halo collimation.
• Diagnostics to demonstrate collimation and control of high energy beams.

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FACET-II is the only User Facility in the world that combines 10 GeV beams with high-power lasers to accommodate this type of R&D.

Linear Compton Scattering

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Much of this R&D assumes Linear Compton Scattering.

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We prefer long electron beams and stretched laser pulses (σ_z = 200 μm, σ_t = 0.66 ps)

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Assume 100 mJ laser pulse energy.

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The expected cross-section is 550 millibarn.

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There are approximately 4 ✕ 10¹⁷ photons per pulse.

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The interaction probability is 10^-3 - 10^-2 depending on geometry.

Phase 1: Demonstration of a fast feed-forward system

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Goals:

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• Mimic feedback mechanism for FCC-ee by demonstrating shot-to-shot feed forward control.
• Deploy halo characterization diagnostic.

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Hardware:

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• No change to E320 setup.
• Electronics for fast Pockels cell control.
• AWAKE-style Halo Monitor.

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Expected signal:

• 5✕ 10⁷ scattering events per pulse.

I. Drebot, et. al IPAC 2023 https://doi.org/10.18429/JACoW-IPAC2023-MOPA074

M. Turner, et. al Phys. Rev. Lett. 122, 054801 (2019)

Phase 1: Demonstration of a fast feed-forward system

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Goals:

​

• Mimic feedback mechanism for FCC-ee by demonstrating shot-to-shot feed forward control.
• Deploy halo characterization diagnostic.

​

Hardware:

​

• No change to E320 setup.
• Electronics for fast Pockels cell control.
• AWAKE-style Halo Monitor.

​

Expected signal:

• 5✕ 10⁷ scattering events per pulse.

I. Drebot, et. al IPAC 2023 https://doi.org/10.18429/JACoW-IPAC2023-MOPA074

M. Turner, et. al Phys. Rev. Lett. 122, 054801 (2019)

AWAKE-style halo monitor implemented at FACET-II.

Phase 1: Demonstration of a fast feed-forward system

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Approach:

• Is it possible to extract data relevant to this experiment from results already obtained by E320?
• For example, focus on subsets of the data with low laser intensity and linear compton scattering.

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Challenges:

• We don’t have a shot-to-shot energy measurement for the laser, but can we calibrate the laser pulse energy variations from camera data.

Phase 2: Halo Collimation

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Goals:

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• Interact beam halo particles with an annular laser pulse.
• Measure jitter tolerances and effects.

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Hardware:

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• Laguerre-Gauss or High-Order Bessel Optics.
• Head-on laser interaction.
• LBG_LFOV or other sensitive detector.

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Expected signal:

• 7✕ 10³ scattering events per pulse.

Gessner, S. et al. Demonstration of a positron beam-driven hollow channel plasma wakefield accelerator. Nat. Comm. 2016.

LBG_LFOV upgrade (Knetsch)

Phase 3: Alternative Schemes

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Goals:

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• Reduce required laser pulse energy needed for collimation and control by utilizing nonlinear compton scattering and/or alternate geometries.

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• Explore cavity geometry

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Tilted Phase Front

Cylindrical Lens

Nonlinear Quenched Regime

Operate in a nonlinear regime but still induce a binary interaction.

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“Quantum Quenching of Radiation Losses in Short Laser Pulses.” C. N. Harvey, et al. Phys. Rev. Lett. 118, 105004 (2017)

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Timeline

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Phase 1 Experiment (Linear Compton scattering for bunch intensity control)

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• On-going with E320 data
• No dedicated beamtime anticipated
• Might request specific datasets during future E320 beam times

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Phase 2 Experiment (Laser collimation with annular laser pulse)

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• 06/2026: Bench testing optical setup in laser room.
• 08/2026: Installation of axicon optic in tunnel. Place orders for diffractive optics.
• 09/2026: Optimization of optics in the tunnel for experiments.
• 10-11/2026: First beam time TBD. Will coordinate with E320.
• . . .
• 2027: Follow-on experiments with diffractive optics.

Collaborators welcome to join for experiments at FACET!

Conclusions

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The R&D topics have the potential to improve the performance and reduce the cost of future Higgs Factories.

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The E320 experiment enables rapid implementation and a clear path to results.

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The new Halo Monitor Diagnostic has been implemented: https://doi.org/10.1140/epjp/s13360-026-07754-x