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Title: Topological cathodes: Controlling the space charge limit of electron emission using metamaterials

Abstract

The space charge limit (SCL) of emission from photocathodes sets an upper limit on the performance of both high- and low-field electron guns. Generally, one is forced to strike a compromise between the space charge limit and the cathode’s intrinsic emittance [I. Bazarov et al., Phys. Rev. Lett. 102, 104801 (2009)]. However, it is possible to nearly eliminate the SCL due to the image charge by engineering the topography of the cathode’s surface. A cathode with a surface plasma frequency below the frequency spectrum of the accelerating electrons will greatly reduce the polarization of the cathode and its image-charge field, thereby mitigating the cathode’s space charge limit for photoelectric, thermionic, and field emission. In the work presented here, a theory for the image-charge field of a disk of charge being accelerated from the cathode surface is developed which includes the frequency-dependent effects of the cathode’s dielectric function. This theory verifies the concept of SCL mitigation with a wire array metamaterial to design a metacathode with greatly reduced image-charge fields. The details of the holistic metacathode design spanning 6 orders of magnitude in scale are described.

Authors:
ORCiD logo [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1562492
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review Accelerators and Beams
Additional Journal Information:
Journal Volume: 22; Journal Issue: 8; Journal ID: ISSN 2469-9888
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Dowell, David H. Topological cathodes: Controlling the space charge limit of electron emission using metamaterials. United States: N. p., 2019. Web. doi:10.1103/physrevaccelbeams.22.084201.
Dowell, David H. Topological cathodes: Controlling the space charge limit of electron emission using metamaterials. United States. doi:10.1103/physrevaccelbeams.22.084201.
Dowell, David H. Fri . "Topological cathodes: Controlling the space charge limit of electron emission using metamaterials". United States. doi:10.1103/physrevaccelbeams.22.084201. https://www.osti.gov/servlets/purl/1562492.
@article{osti_1562492,
title = {Topological cathodes: Controlling the space charge limit of electron emission using metamaterials},
author = {Dowell, David H.},
abstractNote = {The space charge limit (SCL) of emission from photocathodes sets an upper limit on the performance of both high- and low-field electron guns. Generally, one is forced to strike a compromise between the space charge limit and the cathode’s intrinsic emittance [I. Bazarov et al., Phys. Rev. Lett. 102, 104801 (2009)]. However, it is possible to nearly eliminate the SCL due to the image charge by engineering the topography of the cathode’s surface. A cathode with a surface plasma frequency below the frequency spectrum of the accelerating electrons will greatly reduce the polarization of the cathode and its image-charge field, thereby mitigating the cathode’s space charge limit for photoelectric, thermionic, and field emission. In the work presented here, a theory for the image-charge field of a disk of charge being accelerated from the cathode surface is developed which includes the frequency-dependent effects of the cathode’s dielectric function. This theory verifies the concept of SCL mitigation with a wire array metamaterial to design a metacathode with greatly reduced image-charge fields. The details of the holistic metacathode design spanning 6 orders of magnitude in scale are described.},
doi = {10.1103/physrevaccelbeams.22.084201},
journal = {Physical Review Accelerators and Beams},
number = 8,
volume = 22,
place = {United States},
year = {2019},
month = {8}
}

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