Untangling the contributions of image charge and laser profile for optimal photoemission of high-brightness electron beams

Using our model for the simulation of photoemission of high brightness electron beams, we investigate the virtual cathode physics and the limits to spatio-temporal and spectroscopic resolution originating from the image charge on the surface and from the profile of the exciting laser pulse. By contr...

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Bibliographic Details
Published in:Journal of applied physics 2014-11, Vol.116 (17), p.174302
Main Authors: Portman, J., Zhang, H., Makino, K., Ruan, C. Y., Berz, M., Duxbury, P. M.
Format: Article
Language:English
Subjects:
Applied physics
Aspect ratio
BRIGHTNESS
COHERENCE LENGTH
Computer simulation
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
ELECTRON BEAMS
ELECTRON MICROSCOPES
ELECTRONS
Emittance
EXTRACTION
Image charge
Laser beams
LASER RADIATION
Lasers
LIMITING VALUES
Photoelectric emission
PHOTOEMISSION
SIMULATION
SURFACE PROPERTIES
SURFACES
TIME RESOLUTION
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Summary:Using our model for the simulation of photoemission of high brightness electron beams, we investigate the virtual cathode physics and the limits to spatio-temporal and spectroscopic resolution originating from the image charge on the surface and from the profile of the exciting laser pulse. By contrasting the effect of varying surface properties (leading to expanding or pinned image charge), laser profiles (Gaussian, uniform, and elliptical), and aspect ratios (pancake- and cigar-like) under different extraction field strengths and numbers of generated electrons, we quantify the effect of these experimental parameters on macroscopic pulse properties such as emittance, brightness (4D and 6D), coherence length, and energy spread. Based on our results, we outline optimal conditions of pulse generation for ultrafast electron microscope systems that take into account constraints on the number of generated electrons and on the required time resolution.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4900582