IPAC2018 - List of Authors (Musumeci, P.)

Paper	Title	Page
TUPML026	Multi-photon Photoemission and Ultrafast Electron Heating in Cu Photocathodes at Threshold	1593
	J. Bae, L. Cultrera Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA I.V. Bazarov, J.M. Maxson Cornell University, Ithaca, New York, USA S.S. Karkare, H.A. Padmore LBNL, Berkeley, California, USA P. Musumeci, X.L. Shen UCLA, Los Angeles, California, USA
	Funding: U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams. Operating photocathodes near the photoemission threshold holds the promise of yielding small intrinsic emittance, at the cost of significantly reduced quantum efficiency. In modern femtosecond photoemission electron sources, this requires a very high intensity (10s of GW/cm²) to extract a useful quantity of electrons. At this intensity, the electron occupation function is far from equilibrium and evolves rapidly on sub-ps timescales. Thus, ultrafast laser heating and multiphoton photoemission effects may play a significant role in emission, thereby increasing the minimum achievable emittance. In this work, we use a Boltzmann equation approach to calculate the non-equilibrium occupation function evolution in time for a copper photocathode, yielding a prediction of quantum efficiency and mean transverse energy as a function of input intensity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML026
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMK028	Inverse Free Electron Laser Separatrix Crossing for Energy Gain and Stability	4354
SUSPF030	use link to see paper's listing under its alternate paper code
	N.S. Sudar, P. Musumeci UCLA, Los Angeles, California, USA D. Garzella CEA, Gif-sur-Yvette, France
	The laser wakefield accelerator (LWFA) has been proposed as a driver for next generation compact light sources. However, the beams produced by LWFA's typically exhibit correlated energy spread and energy jitter too large to drive the Free Electron Laser instability. We present here a novel scheme whereby using a highly non-linear strongly tapered undulator interaction directly after the LWFA we are able to trap and accelerate a large fraction of charge in the moving Inverse Free Electron Laser ponderomotive bucket. The final correlated energy spread and output energy are determined by the final bucket height and central energy of the ponderomotive bucket which are both determined by the stagnant undulator parameters, resulting in a significant decrease in the normalized energy spread (< 1%) and output energy jitter (< 1%). This interaction is treated both analytically and numerically.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK028
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPML106	Electron Microscopy Inspired Setup for Single-Shot 4-D Trace Space Reconstruction of Bright Electron Beams	4909
	J. Giner Navarro, D.B. Cesar, P. Musumeci UCLA, Los Angeles, California, USA R.W. Aßmann, B. Marchetti, D. Marx DESY, Hamburg, Germany
	Funding: This work has been partially supported by the National Science Foundation under Grant No. 1549132 and Department of Energy under award No. DE-SC0009914. In the development of low charge, single-shot diagnostics for high brightness electron beams, Transmission Electron Microscopy (TEM) grids present certain advantages compared to pepper pot masks due to higher beam transmission. In this paper, we developed a set of criteria to optimize the resolution of a point projection image. However, this configuration of the beam with respect to the grid and detector positions implies the measurement of a strongly correlated phase space which entails a large sensitivity to small measurement errors in retrieving the projected emittance. We discuss the possibility of an alternative scheme by inserting a magnetic focusing system in between the grid and the detector, similar to an electron microscope design, to reconstruct the phase space when the beam is focused on the grid.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML106
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Multi-photon Photoemission and Ultrafast Electron Heating in Cu Photocathodes at Threshold

1593

J. Bae, L. Cultrera
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
I.V. Bazarov, J.M. Maxson
Cornell University, Ithaca, New York, USA
S.S. Karkare, H.A. Padmore
LBNL, Berkeley, California, USA
P. Musumeci, X.L. Shen
UCLA, Los Angeles, California, USA

Funding: U.S. National Science Foundation under award PHY-1549132, the Center for Bright Beams.
Operating photocathodes near the photoemission threshold holds the promise of yielding small intrinsic emittance, at the cost of significantly reduced quantum efficiency. In modern femtosecond photoemission electron sources, this requires a very high intensity (10s of GW/cm²) to extract a useful quantity of electrons. At this intensity, the electron occupation function is far from equilibrium and evolves rapidly on sub-ps timescales. Thus, ultrafast laser heating and multiphoton photoemission effects may play a significant role in emission, thereby increasing the minimum achievable emittance. In this work, we use a Boltzmann equation approach to calculate the non-equilibrium occupation function evolution in time for a copper photocathode, yielding a prediction of quantum efficiency and mean transverse energy as a function of input intensity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-TUPML026

Export •

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

THPMK028

Inverse Free Electron Laser Separatrix Crossing for Energy Gain and Stability

4354

SUSPF030

use link to see paper's listing under its alternate paper code

N.S. Sudar, P. Musumeci
UCLA, Los Angeles, California, USA
D. Garzella
CEA, Gif-sur-Yvette, France

The laser wakefield accelerator (LWFA) has been proposed as a driver for next generation compact light sources. However, the beams produced by LWFA's typically exhibit correlated energy spread and energy jitter too large to drive the Free Electron Laser instability. We present here a novel scheme whereby using a highly non-linear strongly tapered undulator interaction directly after the LWFA we are able to trap and accelerate a large fraction of charge in the moving Inverse Free Electron Laser ponderomotive bucket. The final correlated energy spread and output energy are determined by the final bucket height and central energy of the ponderomotive bucket which are both determined by the stagnant undulator parameters, resulting in a significant decrease in the normalized energy spread (< 1%) and output energy jitter (< 1%). This interaction is treated both analytically and numerically.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK028

Export •

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

THPML106

Electron Microscopy Inspired Setup for Single-Shot 4-D Trace Space Reconstruction of Bright Electron Beams

4909

J. Giner Navarro, D.B. Cesar, P. Musumeci
UCLA, Los Angeles, California, USA
R.W. Aßmann, B. Marchetti, D. Marx
DESY, Hamburg, Germany

Funding: This work has been partially supported by the National Science Foundation under Grant No. 1549132 and Department of Energy under award No. DE-SC0009914.
In the development of low charge, single-shot diagnostics for high brightness electron beams, Transmission Electron Microscopy (TEM) grids present certain advantages compared to pepper pot masks due to higher beam transmission. In this paper, we developed a set of criteria to optimize the resolution of a point projection image. However, this configuration of the beam with respect to the grid and detector positions implies the measurement of a strongly correlated phase space which entails a large sensitivity to small measurement errors in retrieving the projected emittance. We discuss the possibility of an alternative scheme by inserting a magnetic focusing system in between the grid and the detector, similar to an electron microscope design, to reconstruct the phase space when the beam is focused on the grid.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPML106

Export •

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