Nonlinear Photoemission for Bright Beams in X-Band Photoinjectors
Abstract
The ongoing development of low-cost and compact x-ray light sources is vital for increasing the number of experiments that can be performed at the atomic scale. One option for a compact and simple photoinjector is to operate in blow-out mode, in which a high-charge, short-bunch length electron beam self-expands by space-charge forces into a uniformly ellipsoidal shape. This mode necessitates a photoinjector whose initial electron pulse has a pulse duration on the order of $100$ fs. A photoinjector utilizing linear photoemission with an ultraviolet laser in this regime presents significant technical challenges, as many optical substrates degrade at these wavelengths. In this paper, we present an alternative design that uses nonlinear photoemission to produce electron beams with high charge and short bunch length in an X-band (9300 MHz) photoinjector. This photoinjector design produces an electron beam with a bunch charge of up to $200$ pC, an RMS bunch length of $291$ fs, a normalized transverse emittance of $1$ to $1.4$ mm·mrad, and an energy spread of 10−4. This results in a beam brightness of 1018 A/m2, which is bright enough for our beamline's purposes. We also present ongoing efforts are aimed at further increasing the electron beam brightness by using a spatial light modulator to shape the laser profile at the cathode.
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BibTeX
@misc{timms2026nonlinear,
title = {{Nonlinear Photoemission for Bright Beams in X-Band Photoinjectors}},
author = {Casey Timms and Lucas Malin and Kevin Eckrosh and Sean E. Tilton and Lidia C. Santander and Hyung Seo Lee and Rejul Jaswal and Alex Gardeck and Eric Everett and Alan Dupre and Mukhtar Hussain and Sami Tantawi and William Graves and Henrik Loos and Mark Holl and Arvinder Sandhu and Robert Kaindl and Samuel Teitelbaum},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.04571},
eprint = {2609.04571},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04571},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Nonlinear Photoemission for Bright Beams in X-Band Photoinjectors
AU - Casey Timms
AU - Lucas Malin
AU - Kevin Eckrosh
AU - Sean E. Tilton
AU - Lidia C. Santander
AU - Hyung Seo Lee
AU - Rejul Jaswal
AU - Alex Gardeck
AU - Eric Everett
AU - Alan Dupre
AU - Mukhtar Hussain
AU - Sami Tantawi
AU - William Graves
AU - Henrik Loos
AU - Mark Holl
AU - Arvinder Sandhu
AU - Robert Kaindl
AU - Samuel Teitelbaum
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2609.04571
UR - https://arxiv.org/abs/2609.04571
AB - The ongoing development of low-cost and compact x-ray light sources is vital for increasing the number of experiments that can be performed at the atomic scale. One option for a compact and simple photoinjector is to operate in blow-out mode, in which a high-charge, short-bunch length electron beam self-expands by space-charge forces into a uniformly ellipsoidal shape. This mode necessitates a photoinjector whose initial electron pulse has a pulse duration on the order of $100$ fs. A photoinjector utilizing linear photoemission with an ultraviolet laser in this regime presents significant technical challenges, as many optical substrates degrade at these wavelengths. In this paper, we present an alternative design that uses nonlinear photoemission to produce electron beams with high charge and short bunch length in an X-band (9300 MHz) photoinjector. This photoinjector design produces an electron beam with a bunch charge of up to $200$ pC, an RMS bunch length of $291$ fs, a normalized transverse emittance of $1$ to $1.4$ mm·mrad, and an energy spread of 10^−4. This results in a beam brightness of 10^18 A/m^2, which is bright enough for our beamline's purposes. We also present ongoing efforts are aimed at further increasing the electron beam brightness by using a spatial light modulator to shape the laser profile at the cathode.
ER -