NAPAC2022 - List of Authors (Denham, P.E.)

Paper	Title	Page
TUXD6	Dual Radiofrequency Cavity Based Monochromatization for High Resolution Electron Energy Loss Spectroscopy	278
	A.V. Kulkarni, P.E. Denham, A. Kogar, P. Musumeci UCLA, Los Angeles, USA
	Reducing the energy spread of electron beams can enable breakthrough advances in electron energy loss spectroscopic investigations of solid state samples where characteristic excitations typically have energy scales on the order of meV. In conventional electron sources the energy spread is limited by the emission process and typically on the order of a fraction of an eV. State-of-the-art energy resolution can only be achieved after significant losses in the monochromatization process. Here we propose to take advantage of photoemission from ultrashort laser pulses (~40 fs) so that after a longitudinal phase space manipulation that trades pulse duration for energy spread, the energy spread can be reduced by more than one order of magnitude. The scheme uses two RF cavities to accomplish this goal and can be implemented on a relatively short (~ 1m) beamline. Analytical predictions and results of 3D self consistent beam dynamics simulations are presented to support the findings.
	Slides TUXD6 [1.461 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUXD6
About •	Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 18 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPA77	X-Band Harmonic Longitudinal Phase Space Linearization at the PEGASUS Photoinjector	508
	P.E. Denham, P. Musumeci, A. Ody UCLA, Los Angeles, USA
	Due to the finite bunch length, photoemitted electron beams sample RF-nonlinearities that lead to energy-time correlations along the bunch temporal profile. This is an important effect for all applications where the projected energy spread is important. In particular, for time-resolved single shot electron microscopy, it is critical to keep the beam energy spread below 1·10^-4 to avoid chromatic aberrations in the lenses. Higher harmonic RF cavities can be used to compensate for the RF-induced longitudinal phase space nonlinearities. Start-to-end simulations suggest that this type of compensation can reduce energy spread to the 1·10^-5 level. This work is an experimental study of x-band harmonic linearization of a beam longitudinal phase space at the PEGASUS facility, including developing high-resolution spectrometer diagnostics to verify the scheme.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA77
About •	Received ※ 25 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 10 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPA44	Compact Inter-Undulator Diagnostic Assembly for TESSA-515	732
	T.J. Hodgetts, R.B. Agustsson, Y.C. Chen, A.Y. Murokh, M. Ruelas RadiaBeam, Santa Monica, California, USA P.E. Denham, A.C. Fisher, J. Jin, P. Musumeci, Y. Park UCLA, Los Angeles, USA
	Funding: DOE grant DE-SC0009914, DE-SC0018559, and DE-SC0017102. Beamline space is a very expensive and highly sought-after commodity, which makes the creation of compact integrated optics and diagnostics extremely valuable. The FAST- GREENS experimental program aims at demonstrating 10 % extraction efficiency from a relativistic electron beam using four helical undulators operating in the high gain TESSA regime. The inter-undulator gap needs to be as short as possible (17 cm in the current plans) to maximize the output power. Within this short distance, we needed to fit two focusing quadrupoles, a variable strength phase shifter, a transverse profile monitor consisting of a YAG-OTR combination for co-aligning the electron beam and laser, and an ion pump. By making the quadrupoles tunable with a variable gradient, in combination with vertical displacement, we can meet the optics requirements of matching the beam transversely to the natural focusing of the undulators. The two quadrupoles in conjunction with the electromagnetic dipole also serve as a phase shifter to realign the radiation and the bunching before each undulator section. This paper will discuss the mechanical design of this inter-undulator break section and its components.
	Poster WEPA44 [0.752 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA44
About •	Received ※ 27 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THZE4	Experimental Characterization of Gas Sheet Transverse Profile Diagnostic	907
	N. Burger, G. Andonian, D.I. Gavryushkin, T.J. Hodgetts, A.-L.M.S. Lamure, M. Ruelas RadiaBeam, Santa Monica, California, USA N.M. Cook, A. Diaw RadiaSoft LLC, Boulder, Colorado, USA P.E. Denham, P. Musumeci, A. Ody UCLA, Los Angeles, USA N.P. Norvell UCSC, Santa Cruz, California, USA C.P. Welsch, M. Yadav The University of Liverpool, Liverpool, United Kingdom C.P. Welsch Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Transverse profile diagnostics for high-intensity beams require solutions that are non-intercepting and single-shot. In this paper, we describe a gas-sheet ionization diagnostic that employs a precision-shaped, neutral gas jet. As the high-intensity beam passes through the gas sheet, neutral particles are ionized. The ionization products are transported and imaged on a detector. A neural-network based reconstruction algorithm, trained on simulation data, then outputs the initial transverse conditions of the beam prior to ionization. The diagnostic is also adaptable to image the photons from recombination. Preliminary tests at low energy are presented to characterize the working principle of the instrument, including comparisons to existing diagnostics. The results are parametrized as a function of beam charge, spot size, and bunch length.
	Slides THZE4 [2.051 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZE4
About •	Received ※ 02 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 09 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Dual Radiofrequency Cavity Based Monochromatization for High Resolution Electron Energy Loss Spectroscopy

278

A.V. Kulkarni, P.E. Denham, A. Kogar, P. Musumeci
UCLA, Los Angeles, USA

Reducing the energy spread of electron beams can enable breakthrough advances in electron energy loss spectroscopic investigations of solid state samples where characteristic excitations typically have energy scales on the order of meV. In conventional electron sources the energy spread is limited by the emission process and typically on the order of a fraction of an eV. State-of-the-art energy resolution can only be achieved after significant losses in the monochromatization process. Here we propose to take advantage of photoemission from ultrashort laser pulses (~40 fs) so that after a longitudinal phase space manipulation that trades pulse duration for energy spread, the energy spread can be reduced by more than one order of magnitude. The scheme uses two RF cavities to accomplish this goal and can be implemented on a relatively short (~ 1m) beamline. Analytical predictions and results of 3D self consistent beam dynamics simulations are presented to support the findings.

Slides TUXD6 [1.461 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUXD6

About •

Received ※ 03 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 18 August 2022

Cite •

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

TUPA77

X-Band Harmonic Longitudinal Phase Space Linearization at the PEGASUS Photoinjector

508

P.E. Denham, P. Musumeci, A. Ody
UCLA, Los Angeles, USA

Due to the finite bunch length, photoemitted electron beams sample RF-nonlinearities that lead to energy-time correlations along the bunch temporal profile. This is an important effect for all applications where the projected energy spread is important. In particular, for time-resolved single shot electron microscopy, it is critical to keep the beam energy spread below 1·10^-4 to avoid chromatic aberrations in the lenses. Higher harmonic RF cavities can be used to compensate for the RF-induced longitudinal phase space nonlinearities. Start-to-end simulations suggest that this type of compensation can reduce energy spread to the 1·10^-5 level. This work is an experimental study of x-band harmonic linearization of a beam longitudinal phase space at the PEGASUS facility, including developing high-resolution spectrometer diagnostics to verify the scheme.

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA77

About •

Received ※ 25 July 2022 — Revised ※ 04 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 10 August 2022

Cite •

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

WEPA44

Compact Inter-Undulator Diagnostic Assembly for TESSA-515

732

T.J. Hodgetts, R.B. Agustsson, Y.C. Chen, A.Y. Murokh, M. Ruelas
RadiaBeam, Santa Monica, California, USA
P.E. Denham, A.C. Fisher, J. Jin, P. Musumeci, Y. Park
UCLA, Los Angeles, USA

Funding: DOE grant DE-SC0009914, DE-SC0018559, and DE-SC0017102.
Beamline space is a very expensive and highly sought-after commodity, which makes the creation of compact integrated optics and diagnostics extremely valuable. The FAST- GREENS experimental program aims at demonstrating 10 % extraction efficiency from a relativistic electron beam using four helical undulators operating in the high gain TESSA regime. The inter-undulator gap needs to be as short as possible (17 cm in the current plans) to maximize the output power. Within this short distance, we needed to fit two focusing quadrupoles, a variable strength phase shifter, a transverse profile monitor consisting of a YAG-OTR combination for co-aligning the electron beam and laser, and an ion pump. By making the quadrupoles tunable with a variable gradient, in combination with vertical displacement, we can meet the optics requirements of matching the beam transversely to the natural focusing of the undulators. The two quadrupoles in conjunction with the electromagnetic dipole also serve as a phase shifter to realign the radiation and the bunching before each undulator section. This paper will discuss the mechanical design of this inter-undulator break section and its components.

Poster WEPA44 [0.752 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEPA44

About •

Received ※ 27 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 11 August 2022

Cite •

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

THZE4

Experimental Characterization of Gas Sheet Transverse Profile Diagnostic

907

N. Burger, G. Andonian, D.I. Gavryushkin, T.J. Hodgetts, A.-L.M.S. Lamure, M. Ruelas
RadiaBeam, Santa Monica, California, USA
N.M. Cook, A. Diaw
RadiaSoft LLC, Boulder, Colorado, USA
P.E. Denham, P. Musumeci, A. Ody
UCLA, Los Angeles, USA
N.P. Norvell
UCSC, Santa Cruz, California, USA
C.P. Welsch, M. Yadav
The University of Liverpool, Liverpool, United Kingdom
C.P. Welsch
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Transverse profile diagnostics for high-intensity beams require solutions that are non-intercepting and single-shot. In this paper, we describe a gas-sheet ionization diagnostic that employs a precision-shaped, neutral gas jet. As the high-intensity beam passes through the gas sheet, neutral particles are ionized. The ionization products are transported and imaged on a detector. A neural-network based reconstruction algorithm, trained on simulation data, then outputs the initial transverse conditions of the beam prior to ionization. The diagnostic is also adaptable to image the photons from recombination. Preliminary tests at low energy are presented to characterize the working principle of the instrument, including comparisons to existing diagnostics. The results are parametrized as a function of beam charge, spot size, and bunch length.

Slides THZE4 [2.051 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THZE4

About •

Received ※ 02 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 09 October 2022

Cite •

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