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The Center for Bright Beams, A National Science Foundation Science and Technology Center

Multileaf Collimator for Real-Time Beam Shaping using Emittance Exchange

N. Majernik, G. Andonian, R. Roussel, S. Doran, G. Ha, J. Power, E. Wisniewski, J. Rosenzweig

image of a rendering of the multilieaf collimator
A render of the multileaf collimator is shown here (the vacuum chamber and some support structures have been made translucent for clarity). In this version, stepper motors drive the external magnets using micro-timing belts in modular, 3D printed housings. These external magnets couple to the internal magnets, driving the tungsten tipped pusher rods, shown here creating a mask for a ramped drive beam and witness beam. Expand image.

In this paper we introduce the concept of using a multileaf collimator (MLC) in conjunction with an emittance exchange beamline to allow for finely resolved, real-time control over a beam's current profile. Prior to this advancement, the beam's profile was defined using laser cut masks which were installed into the UHV beamline, requiring days to change masks. However, by using a MLC, real-time iteration is possible; this new approach is highly synergistic with machine learning and should enable very high transformer ratio wakefield acceleration. We have addressed two major considerations towards the implementation of such a system. First, simulations have shown that a practically realizable MLC with forty, two millimeter wide leaves has sufficient resolution to create beam profiles with the same fidelity as a static, laser cut mask. Further, we have introduced a conceptual design for the MLC that addresses the need for UHV compatibility by using magnetic coupling to external actuators.

The most direct application of this scheme will be the demonstration of higher transformer ratio wakefield acceleration which could reduce the footprint and cost of future accelerators, light sources, and colliders. It may also be useful for other applications which require very fine control over the beam's longitudinal profile, e.g. free electron lasers. This effort, a means of precision phase-space control, is aligned with CBB's Beam Dynamics and Control theme.

N. Majernik et al., “Multileaf Collimator for Real-Time Beam Shaping using Emittance Exchange,” arXiv:2107.00125 [physics], Jun. 2021 [Online]. Available: