NAPAC2022 - Table of Session: THYD (Photon Sources and Electron Accelerators)

Paper	Title	Page
THYD1	XFEL as a Low-Emittance Injector for a 4th-Generation Synchrotron Radiation Source	850
	T. Hara RIKEN SPring-8 Center, Hyogo, Japan
	Low-emittance beam injection is required for the future SPring-8-II due to its small injection beam aperture. To meet this requirement, the SACLA linac has been used as a low-emittance injector since 2020 [1]. In order to perform the beam injection in parallel with XFEL operation, three accelerators are virtually constructed in a control system for the two XFEL beamlines and the beam injection, and thus the accelerator parameters can be independently tuned. Since the reference clock frequencies of the two accelerators are not related by an integer multiple, a new timing system was developed that achieves 3.8 ps (rms) synchronization. To maintain bunch purity better than 1e-8, which is routinely requested at SPring-8, an electron sweeper and an RF knock-out system are introduced for the SACLA injector and the SPring-8 storage ring. Although 0.1 nm-rad emittance of SACLA is increased by an order of magnitude at a transport line mainly due to quantum excitation of synchrotron radiation, it is still small enough for SPring-8-II. By shutting down an old dedicated injector complex, energy consumption has been significantly reduced, and it contributes to create a low-carbon society. The speaker present this work on behalf of RIKEN-JASRI project team. [1] Toru Hara et al., Phys. Rev. Accel. Beams 24, 110702 (2021).
	Slides THYD1 [10.103 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD1
About •	Received ※ 29 July 2022 — Revised ※ 05 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 23 September 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYD2	The Challenging Physics Regimes of High Current Electron Beams
	J.E. Coleman LANL, Los Alamos, New Mexico, USA
	Electrons with intense space charge produce truly challenging physics regimes every step of the way. Hollow electron beams produced in the injector with thin enhanced edges are subject to the diocotron instability or a velocity shear, which is related to the Kelvin Helmholtz instability. Misaligned focusing elements and non-uniform current densities lead to non-linear transport effects in accelerator transport. Electrons focused to intensities >10⁵ J/cm² or ne ~ 10¹⁹ m^-3 can produce hot, Te > 1 eV, solid density plasmas that expand slowly over several hundred nanoseconds. The subsequent temperature and density gradients that are produced can generate magnetic fields. Example measurements and calculations of each of these phenomena are presented.
	Slides THYD2 [7.608 MB]
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYD3	Update on the Status of C-Band Research and Facilities at LANL	855
	E.I. Simakov, A.M. Alexander, D.V. Gorelov, T.W. Hall, M.E. Middendorf, D. Rai, T. Tajima, M.R.A. Zuboraj LANL, Los Alamos, New Mexico, USA
	Funding: Los Alamos National Laboratory LDRD Program We will report on the status of two C-band test facilities at Los Alamos National Laboratory (LANL): C-band Engineering Research Facility in New Mexico (CERF-NM), and Cathodes and Rf Interactions in Extremes (CARIE). Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a high gradient test stand powered by a 50 MW, 5.712 GHz Canon klystron. CERF-NM is the first high gradient C-band test facility in the United States. It was fully commissioned in 2021. In the last year, multiple C-band high gradient cavities and components were tested at CERF-NM. Currently we work to implement several updates to the test stand including the ability to remotedly operate at high gradient for the round-the-clock high gradient conditioning. Adding capability to operate at cryogenic temperatures is considered. The construction of CARIE will begin in October of 2022. CARIE will house a cryo-cooled copper RF photoinjector with a high quantum-efficiency cathode and a high gradient accelerator section.
	Slides THYD3 [3.331 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD3
About •	Received ※ 31 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 04 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYD4	Progress on the APS-U Injector Upgrade	859
	J.R. Calvey, T. Fors, K.C. Harkay, U. Wienands ANL, Lemont, Illinois, USA
	Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. For the APS-Upgrade, it was decided to leave the present APS injector chain in place and make individual improvements where needed. The main challenges faced by the injectors are delivering a high charge bunch (up to 16 nC in a single shot) to the storage ring, operating the booster synchrotron and storage ring at different rf frequencies, and maintaining good charge stability during APS-U operations. This paper will summarize recent progress on the injector upgrade. Topics include bucket targeting with the new injection/extraction timing system (IETS), modeling of high charge longitudinal instability in the PAR, and measurements of charge stability for different modes of operation.
	Slides THYD4 [2.015 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD4
About •	Received ※ 19 July 2022 — Accepted ※ 11 August 2022 — Issue date ※ 22 August 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYD5	Development of Nanopatterned Strong Field Emission Cathodes	863
	G.E. Lawler, N. Majernik, J.I. Mann, N. Montanez, J.B. Rosenzweig UCLA, Los Angeles, California, USA
	Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914. Increasing brightness at the cathode is highly desirable for a diverse suite of applications in the electron accelerator community. These applications range from free electron lasers to ultrafast electron diffraction. Many options for higher brightness cathodes are under investigation notably semiconductor cathodes. We consider here the possibility for an alternative paradigm whereby the cathode surface is controlled to reduce the effective area of illumination and emission. We fabricated nanoblade metallic coated cathodes using common nanofabrication techniques. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. As a result of our particular geometry, our beam possesses a notably high aspect ratio in its transverse plane. We can now begin to consider modifications for the production of intentionally patterned beams such as higher aspect ratios and hollow beams.
	Slides THYD5 [4.652 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD5
About •	Received ※ 02 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 05 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THYD6	Arrival Time and Energy Jitter Effects on the Performance of X-Ray Free Electron Laser Oscillator	866
	G. Tiwari BNL, Upton, New York, USA K.-J. Kim, R.R. Lindberg ANL, Lemont, Illinois, USA K.-J. Kim University of Chicago, Chicago, Illinois, USA
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357. We report on the effects of electron beam arrival time and energy jitter on the power level and the fluctuations of the output of an X-ray FEL oscillator (XFELO). For this study, we apply the FEL driven paraxial resonator model of XFELO along with an analytical reflectivity profile to mimic the phase shift and spectral filtering effects of Bragg-crystals. The thresholds for acceptable timing jitters and energy jitters are determined in terms of the fluctuations of the steady-state power output. We explore potential ways to mitigate the power output fluctuations in the presence of unavoidable electron beam jitters.
	Slides THYD6 [1.935 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD6
About •	Received ※ 01 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 03 October 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

XFEL as a Low-Emittance Injector for a 4th-Generation Synchrotron Radiation Source

850

T. Hara
RIKEN SPring-8 Center, Hyogo, Japan

Low-emittance beam injection is required for the future SPring-8-II due to its small injection beam aperture. To meet this requirement, the SACLA linac has been used as a low-emittance injector since 2020 [1]. In order to perform the beam injection in parallel with XFEL operation, three accelerators are virtually constructed in a control system for the two XFEL beamlines and the beam injection, and thus the accelerator parameters can be independently tuned. Since the reference clock frequencies of the two accelerators are not related by an integer multiple, a new timing system was developed that achieves 3.8 ps (rms) synchronization. To maintain bunch purity better than 1e-8, which is routinely requested at SPring-8, an electron sweeper and an RF knock-out system are introduced for the SACLA injector and the SPring-8 storage ring. Although 0.1 nm-rad emittance of SACLA is increased by an order of magnitude at a transport line mainly due to quantum excitation of synchrotron radiation, it is still small enough for SPring-8-II. By shutting down an old dedicated injector complex, energy consumption has been significantly reduced, and it contributes to create a low-carbon society.
The speaker present this work on behalf of RIKEN-JASRI project team.
[1] Toru Hara et al., Phys. Rev. Accel. Beams 24, 110702 (2021).

Slides THYD1 [10.103 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD1

About •

Received ※ 29 July 2022 — Revised ※ 05 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 23 September 2022

Cite •

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

THYD2

The Challenging Physics Regimes of High Current Electron Beams

J.E. Coleman
LANL, Los Alamos, New Mexico, USA

Electrons with intense space charge produce truly challenging physics regimes every step of the way. Hollow electron beams produced in the injector with thin enhanced edges are subject to the diocotron instability or a velocity shear, which is related to the Kelvin Helmholtz instability. Misaligned focusing elements and non-uniform current densities lead to non-linear transport effects in accelerator transport. Electrons focused to intensities >10⁵ J/cm² or ne ~ 10¹⁹ m^-3 can produce hot, Te > 1 eV, solid density plasmas that expand slowly over several hundred nanoseconds. The subsequent temperature and density gradients that are produced can generate magnetic fields. Example measurements and calculations of each of these phenomena are presented.

Slides THYD2 [7.608 MB]

Cite •

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

THYD3

Update on the Status of C-Band Research and Facilities at LANL

855

E.I. Simakov, A.M. Alexander, D.V. Gorelov, T.W. Hall, M.E. Middendorf, D. Rai, T. Tajima, M.R.A. Zuboraj
LANL, Los Alamos, New Mexico, USA

Funding: Los Alamos National Laboratory LDRD Program
We will report on the status of two C-band test facilities at Los Alamos National Laboratory (LANL): C-band Engineering Research Facility in New Mexico (CERF-NM), and Cathodes and Rf Interactions in Extremes (CARIE). Modern applications such as X-ray sources require accelerators with optimized cost of construction and operation, naturally calling for high-gradient acceleration. At LANL we commissioned a high gradient test stand powered by a 50 MW, 5.712 GHz Canon klystron. CERF-NM is the first high gradient C-band test facility in the United States. It was fully commissioned in 2021. In the last year, multiple C-band high gradient cavities and components were tested at CERF-NM. Currently we work to implement several updates to the test stand including the ability to remotedly operate at high gradient for the round-the-clock high gradient conditioning. Adding capability to operate at cryogenic temperatures is considered. The construction of CARIE will begin in October of 2022. CARIE will house a cryo-cooled copper RF photoinjector with a high quantum-efficiency cathode and a high gradient accelerator section.

Slides THYD3 [3.331 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD3

About •

Received ※ 31 July 2022 — Revised ※ 08 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 04 October 2022

Cite •

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

THYD4

Progress on the APS-U Injector Upgrade

859

J.R. Calvey, T. Fors, K.C. Harkay, U. Wienands
ANL, Lemont, Illinois, USA

Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
For the APS-Upgrade, it was decided to leave the present APS injector chain in place and make individual improvements where needed. The main challenges faced by the injectors are delivering a high charge bunch (up to 16 nC in a single shot) to the storage ring, operating the booster synchrotron and storage ring at different rf frequencies, and maintaining good charge stability during APS-U operations. This paper will summarize recent progress on the injector upgrade. Topics include bucket targeting with the new injection/extraction timing system (IETS), modeling of high charge longitudinal instability in the PAR, and measurements of charge stability for different modes of operation.

Slides THYD4 [2.015 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD4

About •

Received ※ 19 July 2022 — Accepted ※ 11 August 2022 — Issue date ※ 22 August 2022

Cite •

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

THYD5

Development of Nanopatterned Strong Field Emission Cathodes

863

G.E. Lawler, N. Majernik, J.I. Mann, N. Montanez, J.B. Rosenzweig
UCLA, Los Angeles, California, USA

Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE HEP Grant DE-SC0009914.
Increasing brightness at the cathode is highly desirable for a diverse suite of applications in the electron accelerator community. These applications range from free electron lasers to ultrafast electron diffraction. Many options for higher brightness cathodes are under investigation notably semiconductor cathodes. We consider here the possibility for an alternative paradigm whereby the cathode surface is controlled to reduce the effective area of illumination and emission. We fabricated nanoblade metallic coated cathodes using common nanofabrication techniques. We have demonstrated that a beam can be successfully extracted with a low emittance and we have reconstructed a portion of the energy spectrum. As a result of our particular geometry, our beam possesses a notably high aspect ratio in its transverse plane. We can now begin to consider modifications for the production of intentionally patterned beams such as higher aspect ratios and hollow beams.

Slides THYD5 [4.652 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD5

About •

Received ※ 02 August 2022 — Accepted ※ 08 August 2022 — Issue date ※ 05 October 2022

Cite •

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

THYD6

Arrival Time and Energy Jitter Effects on the Performance of X-Ray Free Electron Laser Oscillator

866

G. Tiwari
BNL, Upton, New York, USA
K.-J. Kim, R.R. Lindberg
ANL, Lemont, Illinois, USA
K.-J. Kim
University of Chicago, Chicago, Illinois, USA

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357.
We report on the effects of electron beam arrival time and energy jitter on the power level and the fluctuations of the output of an X-ray FEL oscillator (XFELO). For this study, we apply the FEL driven paraxial resonator model of XFELO along with an analytical reflectivity profile to mimic the phase shift and spectral filtering effects of Bragg-crystals. The thresholds for acceptable timing jitters and energy jitters are determined in terms of the fluctuations of the steady-state power output. We explore potential ways to mitigate the power output fluctuations in the presence of unavoidable electron beam jitters.

Slides THYD6 [1.935 MB]

DOI •

reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-THYD6

About •

Received ※ 01 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 06 August 2022 — Issue date ※ 03 October 2022

Cite •

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