IPAC2018 - List of Authors (Galdi, A.)

Paper	Title	Page
TUPML027	Barium Tin Oxide Ordered Photocathodes: First Measurements and Future Perspectives	1597
	A. Galdi, E. B. Lochocki, H. Paik, C.T. Parzyck, D. G. Schlom, K.M. Shen Cornell University, Ithaca, New York, USA G. Adhikari, W.A. Schroeder UIC, Chicago, Illinois, USA I.V. Bazarov, L. Cultrera, W. H. Li, J.M. Maxson, C. M. Pierce Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams. Single crystalline photocathodes with small electron effective mass are supposed to enable ultra-low emittance beams, by taking advantage of the conservation of transverse (crystal) momentum. We present a preliminary study on photoemission from epitaxial films of La-doped BaSnO₃ with (100) orientation. We demonstrate here the possibility of generating and characterizing electron beams by exciting photoelectrons solely from the conduction band. We report quantum efficiency and mean transverse energy meaurements as a function of photon energy from the bare and Cs-activated La-doped BaSnO₃ surface.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML027
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THPMF080	Physical and Chemical Roughness of Alkali-Animonide Cathodes	4259
	S.S. Karkare, S. Emamian, G. Gevorkyan, H.A. Padmore, A.K. Schmid LBNL, Berkeley, California, USA I.V. Bazarov Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA A. Galdi Cornell University, Ithaca, New York, USA
	Over the last decade, alkali-antimonides have been investigated as high QE cathodes in green light and more recently as ultra-low intrinsic emittance cathodes in near-threshold red wavelengths at cryogenic temperatures. Nano-meter scale surface non-uniformities (physical roughness and chemical roughness or work function variations) are thought to limit the smallest possible emittance from these materials at the photoemission threshold under cryogenic conditions. Despite this, the surfaces of alkali-antimonides have not been well characterized in terms of the surface non-uniformities. Here, we present measurements of both the physical and chemical roughness of alkali-antimonide surfaces using several surface characterization techniques like atomic force microscopy, kelvin probe force microscopy, low energy electron microscopy and near-threshold photoemission electron microscopy and show how such non-uniformities limit the intrinsic emittance. L. Cultrera et al Phys. Rev. ST Accel. Beams 18, 113401 (2015) **J. Feng et al, J. of Appl. Phys. 121, 044904 (2017)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF080
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TUPML028	Photocathodes R&D for High Brightness and Highly Polarized Electron Beams at Cornell University	1601
	L. Cultrera, J. Bae, A.C. Bartnik, I.V. Bazarov, R. Doane, A. Galdi, C.M. Gulliford, W. H. Li, J.M. Maxson, S.A. McBride, T.P. Moore, C. M. Pierce, C. Xu Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cornell University is a leader in the development of photocathode materials for the production of high brightness electron beam sources for applications in large scale accelerators and small scale electron scattering experiments. During the last year we have also included Mott polarimetry to investigate long lifetime spin-polarized photocathodes materials. Another thrust of our laboratory is the exploration of ultra low emittance photocathodes at cryogenic temperatures, for which we are building a novel LHe cryogenic electron source. We will review updates from our lab across each of these areas.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML028
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THPML053	Computational Screening for Low Emittance Photocathodes	4755
	J.T. Paul, R.G. Hennig University of Florida, Gainesville, Florida, USA I.V. Bazarov, A. Galdi Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA S.S. Karkare, H.A. Padmore LBNL, Berkeley, California, USA
	The majority of photocathode materials in use in accelerator applications have been discovered empirically through trial and error with little guidance from material science calculations. Alternatively, one can envision a process which is heavily guided by computational search using latest advances in density functional theory (DFT). In this work, the MaterialsProject database is searched for potential single crystal photocathodes that would be suitable for ultralow emittance beam production. The materials in the database are initially screened on the basis of experimental practicality. Following this, the expected emittance is calculated from the DFT computed band structures for the pre-screened materials using the conservation of energy and transverse momentum during photoemission. Based on such computational screening, we provide a list of potential low emittance photocathode materials which can be investigated experimentally as high brightness electron sources.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML053
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Paper

Title

Page

Barium Tin Oxide Ordered Photocathodes: First Measurements and Future Perspectives

1597

A. Galdi, E. B. Lochocki, H. Paik, C.T. Parzyck, D. G. Schlom, K.M. Shen
Cornell University, Ithaca, New York, USA
G. Adhikari, W.A. Schroeder
UIC, Chicago, Illinois, USA
I.V. Bazarov, L. Cultrera, W. H. Li, J.M. Maxson, C. M. Pierce
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This work was supported by the U.S. National Science Foundation under Award PHY-1549132, the Center for Bright Beams.
Single crystalline photocathodes with small electron effective mass are supposed to enable ultra-low emittance beams, by taking advantage of the conservation of transverse (crystal) momentum. We present a preliminary study on photoemission from epitaxial films of La-doped BaSnO₃ with (100) orientation. We demonstrate here the possibility of generating and characterizing electron beams by exciting photoelectrons solely from the conduction band. We report quantum efficiency and mean transverse energy meaurements as a function of photon energy from the bare and Cs-activated La-doped BaSnO₃ surface.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML027

Export •

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

THPMF080

Physical and Chemical Roughness of Alkali-Animonide Cathodes

4259

S.S. Karkare, S. Emamian, G. Gevorkyan, H.A. Padmore, A.K. Schmid
LBNL, Berkeley, California, USA
I.V. Bazarov
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
A. Galdi
Cornell University, Ithaca, New York, USA

Over the last decade, alkali-antimonides have been investigated as high QE cathodes in green light and more recently as ultra-low intrinsic emittance cathodes in near-threshold red wavelengths at cryogenic temperatures*. Nano-meter scale surface non-uniformities (physical roughness and chemical roughness or work function variations) are thought to limit the smallest possible emittance from these materials at the photoemission threshold under cryogenic conditions**. Despite this, the surfaces of alkali-antimonides have not been well characterized in terms of the surface non-uniformities. Here, we present measurements of both the physical and chemical roughness of alkali-antimonide surfaces using several surface characterization techniques like atomic force microscopy, kelvin probe force microscopy, low energy electron microscopy and near-threshold photoemission electron microscopy and show how such non-uniformities limit the intrinsic emittance.
*L. Cultrera et al Phys. Rev. ST Accel. Beams 18, 113401 (2015)
**J. Feng et al, J. of Appl. Phys. 121, 044904 (2017)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMF080

Export •

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

TUPML028

Photocathodes R&D for High Brightness and Highly Polarized Electron Beams at Cornell University

1601

L. Cultrera, J. Bae, A.C. Bartnik, I.V. Bazarov, R. Doane, A. Galdi, C.M. Gulliford, W. H. Li, J.M. Maxson, S.A. McBride, T.P. Moore, C. M. Pierce, C. Xu
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cornell University is a leader in the development of photocathode materials for the production of high brightness electron beam sources for applications in large scale accelerators and small scale electron scattering experiments. During the last year we have also included Mott polarimetry to investigate long lifetime spin-polarized photocathodes materials. Another thrust of our laboratory is the exploration of ultra low emittance photocathodes at cryogenic temperatures, for which we are building a novel LHe cryogenic electron source. We will review updates from our lab across each of these areas.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML028

Export •

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

THPML053

Computational Screening for Low Emittance Photocathodes

4755

J.T. Paul, R.G. Hennig
University of Florida, Gainesville, Florida, USA
I.V. Bazarov, A. Galdi
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
S.S. Karkare, H.A. Padmore
LBNL, Berkeley, California, USA

The majority of photocathode materials in use in accelerator applications have been discovered empirically through trial and error with little guidance from material science calculations. Alternatively, one can envision a process which is heavily guided by computational search using latest advances in density functional theory (DFT). In this work, the MaterialsProject database is searched for potential single crystal photocathodes that would be suitable for ultralow emittance beam production. The materials in the database are initially screened on the basis of experimental practicality. Following this, the expected emittance is calculated from the DFT computed band structures for the pre-screened materials using the conservation of energy and transverse momentum during photoemission. Based on such computational screening, we provide a list of potential low emittance photocathode materials which can be investigated experimentally as high brightness electron sources.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML053

Export •

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