IPAC2021 - List of Authors (Knill, C.J.)

Paper	Title	Page
WEPAB099	Near-Threshold Nonlinear Photoemission From Cu(100)	2822
	C.J. Knill, S.S. Karkare Arizona State University, Tempe, USA H.A. Padmore LBNL, Berkeley, California, USA
	Funding: National Science Foundation Grant No. PHY-1549132 Photocathodes that have a low mean transverse energy (MTE) are crucial to the development of compact X-ray Free Electron Lasers (XFEL) and ultrafast electron diffraction (UED) experiments. For FELs, low MTE cathodes result in a lower requirement for electron energy when lasing at a defined energy, and for a defined electron energy result in lasing at higher energy. For UED experiments, low MTE cathodes give a longer coherence length, allowing measurements on larger unit cell materials. A record low MTE of 5 meV has been recently demonstrated from a Cu (100) surface when measured near the photoemission threshold and cooled down to 30 K with liquid Helium []. For UED and XFEL applications that require a high charge density, the low quantum efficiency of Cu (100) near threshold necessitates the use of a high laser fluence to achieve the desired charge density []. At high laser fluences the MTE is limited by nonlinear effects, and therefore it is necessary to investigate near photoemission threshold at these high laser fluences. In this paper we report on nonlinear, near-threshold photoemission from a Cu (100) cathode, and its effect on the MTE. S. Karkare et al, Phys. Rev. Lett. 125, 054801 (2020) ** J. Bae et al, J. Appl. Phys., 124, 244903 (2018)
	Poster WEPAB099 [0.829 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB099
About •	paper received ※ 19 May 2021 paper accepted ※ 21 July 2021 issue date ※ 29 August 2021
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THPAB142	Optical and Surface Characterization of Alkali-Antimonide Photocathodes	4037
	P. Saha, O. Chubenko, G.S. Gevorkyan, A.H. Kachwala, S.S. Karkare, C.J. Knill Arizona State University, Tempe, USA E.J. Montgomery, S. Poddar Euclid Beamlabs, Bolingbrook, USA H.A. Padmore LBNL, Berkeley, California, USA
	Alkali-antimonides, characterized by high quantum efficiency and low mean transverse energy in visible light, are excellent electron sources to drive x-ray free electron lasers, electron cooling and ultrafast electron diffraction applications etc. Existing studies of alkali-antimonides have focused on quantum efficiency and emittance, but information is lacking on the fundamental aspects of the electronic structure, such as the energy gap of the semiconductor and the density of defects as well as the overall nano-structure of the materials. We are, therefore, conducting photoconductivity measurements to measure fundamental semiconductor properties as well as using atomic force microscope (AFM) and kelvin probe force microscope (KPFM) to measure the nanostructure variations in structure and surface potential.
	Poster THPAB142 [1.211 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB142
About •	paper received ※ 16 May 2021 paper accepted ※ 14 July 2021 issue date ※ 13 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Near-Threshold Nonlinear Photoemission From Cu(100)

2822

C.J. Knill, S.S. Karkare
Arizona State University, Tempe, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Funding: National Science Foundation Grant No. PHY-1549132
Photocathodes that have a low mean transverse energy (MTE) are crucial to the development of compact X-ray Free Electron Lasers (XFEL) and ultrafast electron diffraction (UED) experiments. For FELs, low MTE cathodes result in a lower requirement for electron energy when lasing at a defined energy, and for a defined electron energy result in lasing at higher energy. For UED experiments, low MTE cathodes give a longer coherence length, allowing measurements on larger unit cell materials. A record low MTE of 5 meV has been recently demonstrated from a Cu (100) surface when measured near the photoemission threshold and cooled down to 30 K with liquid Helium [*]. For UED and XFEL applications that require a high charge density, the low quantum efficiency of Cu (100) near threshold necessitates the use of a high laser fluence to achieve the desired charge density [**]. At high laser fluences the MTE is limited by nonlinear effects, and therefore it is necessary to investigate near photoemission threshold at these high laser fluences. In this paper we report on nonlinear, near-threshold photoemission from a Cu (100) cathode, and its effect on the MTE.
* S. Karkare et al, Phys. Rev. Lett. 125, 054801 (2020)
** J. Bae et al, J. Appl. Phys., 124, 244903 (2018)

Poster WEPAB099 [0.829 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB099

About •

paper received ※ 19 May 2021 paper accepted ※ 21 July 2021 issue date ※ 29 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB142

Optical and Surface Characterization of Alkali-Antimonide Photocathodes

4037

P. Saha, O. Chubenko, G.S. Gevorkyan, A.H. Kachwala, S.S. Karkare, C.J. Knill
Arizona State University, Tempe, USA
E.J. Montgomery, S. Poddar
Euclid Beamlabs, Bolingbrook, USA
H.A. Padmore
LBNL, Berkeley, California, USA

Alkali-antimonides, characterized by high quantum efficiency and low mean transverse energy in visible light, are excellent electron sources to drive x-ray free electron lasers, electron cooling and ultrafast electron diffraction applications etc. Existing studies of alkali-antimonides have focused on quantum efficiency and emittance, but information is lacking on the fundamental aspects of the electronic structure, such as the energy gap of the semiconductor and the density of defects as well as the overall nano-structure of the materials. We are, therefore, conducting photoconductivity measurements to measure fundamental semiconductor properties as well as using atomic force microscope (AFM) and kelvin probe force microscope (KPFM) to measure the nanostructure variations in structure and surface potential.

Poster THPAB142 [1.211 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB142

About •

paper received ※ 16 May 2021 paper accepted ※ 14 July 2021 issue date ※ 13 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)