Speaker
Description
Accurate characterization of 3D space-charge fields in ultrashort electron beams is crucial for next-generation accelerators. The complex, transient 3D space-charge and CSR fields that ultimately shape and limit high-brightness beams have yet to be directly measured, leaving critical dynamics unobserved. A compact diagnostic for the direct measurement of the field itself thus remains a key challenge.
We present a compact Photoconductive Antenna (PCA) diagnostic for direct field measurement at the LCLS. The PCA operates by using a soft X-ray (SXR) pulse, collimated by a laser-drilled aperture, to generate localized free charge carriers in a diamond sensor. The transverse space-charge field of a passing electron bunch then drives these carriers, inducing a measurable current in a nearby antenna via the Ramo-Shockley theorem.
A full 3D spatiotemporal field map is reconstructed by mechanically scanning the device for transverse (x-y) resolution and varying the X-ray arrival time using an SXR delay line for femtosecond-scale longitudinal (z) resolution. This presentation will cover the PCA's operational principle and design for LCLS. By providing a direct, femtosecond-micron measurement of the beam's vector field, rather than its scalar charge density, the PCA offers a unique capability for optimizing beam performance in advanced accelerators.
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