David Cesar
Staff Scientist SLAC National Accelerator Laboratory

My research focuses on intense beam-matter interactions and the application of accelerator physics to ultrafast science. I develop techniques to create and control high intensity electron beams and attosecond x-ray free electron lasers. A deep understanding of how these beams interact with each other and with matter work is important both for applications to energy science, and for understanding and controlling the collective effects that limit linear collider and FEL performance.

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News

Welcome Federico!

[Apr 2026] Federico Vismarra joins us to research the interesection of attosecond physics and FEL science.

Research directions

Attosecond FEL Pulses (XLEAP)

Attosecond FEL Pulses (XLEAP)

A SASE x-ray free electron laser (xFEL) like LCLS can produce single-spike attosecond soft x-rays by using the chirp-taper mechanism to suppress resonance outside an FEL coherence length. During single-spike operation, the FEL develops a stable, seed-like structure (relative to the electron beam), which can be used to shape the x-ray pulse in downstream amplification stages. In principle, this enables attosecond pulses with higher peak power, two colors, improved stability, and shorter pulse lengths.

Attosecond Metrology for Electron and X-ray beams

Existing diagnostics are incapable of resolving single-spike FEL physics. To bridge this gap, we are building a streaking diagnostic in which the x-ray pulse and electron beam are spatio-temporally overlapped in a target such that photoelectrons created by the x-rays are accelerated by the space-charge field of the beam. Photoelectrons which are born early will be accelerated to higher energies than those born late, so that a TOF spectrometer can be used to map energy to time. Because the same electron beam is used both to generate and to streak the x-rays, the diagnostic will be intrinsically synchronous and able to reconstruct the first-order coherence properties of the x-ray beam.

Attosecond Metrology for Electron and X-ray beams
Photoconductive sampling of space-charge fields

Photoconductive sampling of space-charge fields

Directly measuring the electric field of a relativistic electron beam as it compresses and bends is a crucial step in understanding the collective effects which limit the performance of state-of-the-art linear accelerators. We are developing photo-conductive antennas in which charge is injected into a medium by an x-ray “gate” and then accelerated across our device by the electron beam’s space-charge field. By reading the voltage induced in nearby antennas as function of antenna position and orientation, we can infer the strength of the beam field and produce 3D spatio-temporal maps of the vectorial electric field.

Beam - matter interactions

A relativistic electron beam interacts with matter both through energetic billiard-ball like collisions, and through distant electromagnetic interactions. Nearby the beam, the distant interactions sum into a powerful space-charge impulse which looks like a 'half-cycle' laser field. I study how this space charge field can be used to drive novel quantum dynamics.

Beam - matter interactions

Education

2019 -
SLAC National Accelerator Laboratory
Accelerator research directorate
2013-2019
University of California Los Angeles
PhD, Physics - Probing ultrafast dynamics with relativistic electrons
2009-2013
University of California Los Angeles
B.A. Physics

References

Google Scholar

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Email

dcesar@slac.stanford.edu