IPAC2021 - Table of Session: FRXA (Friday Oral Parallel A)

Paper

Title

Page

Full Energy On-Demand Beam Injection from SACLA into the SPring-8 Storage Ring

4508

H. Maesaka, T. Fukui, T. Hara, T. Hiraiwa, T. Inagaki, E. Iwai, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
H. Dewa, T. Fujita, K. Fukami, N. Hosoda, A. Kiyomichi, M. Masaki, S. Matsubara, T. Ohshima, M. Oishi, K. Soutome, S. Takano, T. Watanabe
JASRI/SPring-8, Hyogo-ken, Japan
C. Kondo
JASRI, Hyogo, Japan

The beam injector for the SPring-8 storage ring (SR) was switched from the booster synchrotron to the SACLA linac, a driver for X-ray free-electron laser (XFEL). The low-emittance beam from SACLA (~100 pm rad, 8 GeV) is delivered to the SR through a 600m-long beam transport line. This low-emittance beam can be applied to the new low-emittance storage ring after the SPring-8 upgrade planed in the coming years. The shutdown of the booster synchrotron and 1-GeV linac saves energy consumption and operation cost. To provide the electron beam injected to the SR on demand for the top-up injection during the XFEL operation, the SACLA linac must be synchronized to the desired bucket of the SR, the beam energy and route must be switched shot-to-shot, and the XFEL performance must not be degraded. We developed a precise synchronization system, on-demand beam route and parameter switching system, a pulsed magnet for the switchyard, isolated bunch purification system, etc. In this presentation, we will show the design and performance of each component for the beam injection and the results from beam commissioning of the accelerator and transport line.

Slides FRXA01 [3.446 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA01

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paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 31 August 2021

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FRXA02

Advances in Beam Stability in Low-Emittance Synchrotron Light Sources

G.M. Wang
BNL, Upton, New York, USA

The evolution and maturation of user applications at low-emittance light sources is driving new, more stringent requirements for electron beam stability in the source points. Long high-spatial-resolution, nano-focus, and high-energy-resolution beamlines demand that the beam orbit and envelope in their insertion devices are stabilized to a small degree of the beam size. At the same time, the capabilities of modern electronics have been advancing rapidly in the past decade, enabling revolutionary developments in broad-bandwidth feedback systems for every dimension of beam dynamics. In addition, synergies between modern beamline and accelerator controls have opened up a pathway to develop and test the first fully integrated feedback system that can counteract drifts and vibrations, allowing us to meet these tight stability requirements. In this presentation we will discuss the stability requirements for premier instruments at NSLS-II and summarize our recent developments in this area.

Slides FRXA02 [2.914 MB]

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FRXA03

Harmonic Rf Cavities and Instabilities in Electron Storage Rings

M. Venturini
LBNL, Berkeley, California, USA

Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231.
Higher-harmonic rf cavities (HHC) are employed in several storage-ring light sources to lengthen the bunches and increase Touschek lifetime; their use is gaining further popularity in the new-generation machines as stronger intra-beam particle scattering is the unavoidable price to pay for higher brightness. Historically, HHCs were first introduced as a way to control certain collective instabilities. While often dubbed as "Landau cavities" (with reference to the damping potentially associated with the HHC-induced synchrotron-oscillation frequency spread), their effect on beam stability is, in fact, not necessarily always beneficial. Whether the HHCs help stabilize a beam, aggravate existing instabilities, or introduce new ones, is a complicated matter that depends on various circumstances. With focus on normal-conducting passive HHCs this talk will present some recent progress and revisit some older results on instability collective-mode theory illustrating aspects of the complex impact that HHCs have on beam dynamics. We will also review some open problems, making the case for the need of further theory development beyond conventional mode analysis.

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FRXA04

Commissioning results of LCLS-II MHz repetition rate electron source

F. Zhou, C. Adolphsen, A.L. Benwell, G.W. Brown, D. Dowell, M.P. Dunning, S. Gilevich, K. Grouev, B.T. Jacobson, X. Liu, A. Miahnahri, J.F. Schmerge, T. Vecchione
SLAC, Menlo Park, California, USA
G. Huang, F. Sannibale
LBNL, Berkeley, California, USA

Funding: work supported by DOE under grant No. DE-AC02-76SF00515
A 4 GeV 1.3 GHz superconducting linac is being constructed at SLAC as part of the X-ray free electron laser project (LCLS-II). The first 3-meter of the electron source that includes a normal conducting 185.7MHz CW RF gun, 2-cell 1.3 GHz CW RF buncher, and a loadlock system for cathode changes was designed and built by LBNL based on their experience with similar one for advanced photo-injector experiment program. The electron beam is designed to operate at a high repetition rate, up to 1 MHz. Since summer of 2018 we started LCLS-II injector source commissioning immediately after the major installation completion. This paper presents major commissioning results including achievements of ultra-high vacuum, RF processing to CW nominal power, dark current characterization and mitigation, and high-brightness electron beam measurements.

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FRXA05

Record High Extraction Efficiency of Free electron Laser Oscillator

H. Zen, H. Ohgaki
Kyoto University, Kyoto, Japan
R. Hajima
QST, Tokai, Japan

Funding: This work was supported by the MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118070271.
The highest extraction efficiency (9.4%) of a free electron laser (FEL) oscillator has been achieved at the mid-infrared FEL facility of Kyoto University*. Because of the interaction between the electron beam and FEL electromagnetic field, a maximum electron energy decrease of 16% was observed. The measured energy decrease was consistent with the measured FEL spectrum. An FEL micro-pulse energy of approximately 100 micro-J with micro-pulse duration of 150 fs was observed. This result is an important milestone for the high-extraction-efficiency FEL oscillator and will contribute to the strong-field physics of atoms and molecules.
*H. Zen et al., Appl. Phys. Express 13, 102007 (2020).

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FRXA06

Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+

4514

F. Pannek, W. Hillert, D. Samoilenko
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper
DESY, Hamburg, Germany
M.A. Pop
MAX IV Laboratory, Lund University, Lund, Sweden

With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06

About •

paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 20 August 2021

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FRXA07

Ringdown Measured in a Four-Bounce, 20 Meter Hard X-Ray Cavity

J.P. MacArthur, Z. Huang, J. Krzywiński, G. Marcus, R.A. Margraf, T. Sato, D. Zhu
SLAC, Menlo Park, California, USA

Funding: This work was supported by the Department of Energy under contract DE-AC02-76SF00515
A cavity-based hard x-ray free-electron laser (CBXFEL) could produce fully coherent pulses with a bandwidth several orders of magnitude below the intrinsic bandwidth of SASE. A cavity-based FEL is not a new concept - the first FEL was an oscillator operating at 3.4 um - but single-pass amplification of spontaneous radiation was the fastest path to gigawatt x-ray powers. One unproven component of a CBXFEL is a stable, high reflectivity cavity. To address this deficit we present ring-down measurements in a 20 m round-trip cold cavity operating at 9.8 keV. The cavity is composed of four strain-relief-cut diamond 400 Bragg mirrors and a transmission grating for in/out-coupling. It is a testbed for alignment protocols and component performance under realistic experimental conditions like source instability, optics imperfections, and thermal drift.

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Paper	Title	Page
FRXA01	Full Energy On-Demand Beam Injection from SACLA into the SPring-8 Storage Ring	4508
	H. Maesaka, T. Fukui, T. Hara, T. Hiraiwa, T. Inagaki, E. Iwai, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan H. Dewa, T. Fujita, K. Fukami, N. Hosoda, A. Kiyomichi, M. Masaki, S. Matsubara, T. Ohshima, M. Oishi, K. Soutome, S. Takano, T. Watanabe JASRI/SPring-8, Hyogo-ken, Japan C. Kondo JASRI, Hyogo, Japan
	The beam injector for the SPring-8 storage ring (SR) was switched from the booster synchrotron to the SACLA linac, a driver for X-ray free-electron laser (XFEL). The low-emittance beam from SACLA (~100 pm rad, 8 GeV) is delivered to the SR through a 600m-long beam transport line. This low-emittance beam can be applied to the new low-emittance storage ring after the SPring-8 upgrade planed in the coming years. The shutdown of the booster synchrotron and 1-GeV linac saves energy consumption and operation cost. To provide the electron beam injected to the SR on demand for the top-up injection during the XFEL operation, the SACLA linac must be synchronized to the desired bucket of the SR, the beam energy and route must be switched shot-to-shot, and the XFEL performance must not be degraded. We developed a precise synchronization system, on-demand beam route and parameter switching system, a pulsed magnet for the switchyard, isolated bunch purification system, etc. In this presentation, we will show the design and performance of each component for the beam injection and the results from beam commissioning of the accelerator and transport line.
	Slides FRXA01 [3.446 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA01
About •	paper received ※ 19 May 2021 paper accepted ※ 01 July 2021 issue date ※ 31 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA02	Advances in Beam Stability in Low-Emittance Synchrotron Light Sources
	G.M. Wang BNL, Upton, New York, USA
	The evolution and maturation of user applications at low-emittance light sources is driving new, more stringent requirements for electron beam stability in the source points. Long high-spatial-resolution, nano-focus, and high-energy-resolution beamlines demand that the beam orbit and envelope in their insertion devices are stabilized to a small degree of the beam size. At the same time, the capabilities of modern electronics have been advancing rapidly in the past decade, enabling revolutionary developments in broad-bandwidth feedback systems for every dimension of beam dynamics. In addition, synergies between modern beamline and accelerator controls have opened up a pathway to develop and test the first fully integrated feedback system that can counteract drifts and vibrations, allowing us to meet these tight stability requirements. In this presentation we will discuss the stability requirements for premier instruments at NSLS-II and summarize our recent developments in this area.
	Slides FRXA02 [2.914 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA03	Harmonic Rf Cavities and Instabilities in Electron Storage Rings
	M. Venturini LBNL, Berkeley, California, USA
	Funding: Work supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231. Higher-harmonic rf cavities (HHC) are employed in several storage-ring light sources to lengthen the bunches and increase Touschek lifetime; their use is gaining further popularity in the new-generation machines as stronger intra-beam particle scattering is the unavoidable price to pay for higher brightness. Historically, HHCs were first introduced as a way to control certain collective instabilities. While often dubbed as "Landau cavities" (with reference to the damping potentially associated with the HHC-induced synchrotron-oscillation frequency spread), their effect on beam stability is, in fact, not necessarily always beneficial. Whether the HHCs help stabilize a beam, aggravate existing instabilities, or introduce new ones, is a complicated matter that depends on various circumstances. With focus on normal-conducting passive HHCs this talk will present some recent progress and revisit some older results on instability collective-mode theory illustrating aspects of the complex impact that HHCs have on beam dynamics. We will also review some open problems, making the case for the need of further theory development beyond conventional mode analysis.
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA04	Commissioning results of LCLS-II MHz repetition rate electron source
	F. Zhou, C. Adolphsen, A.L. Benwell, G.W. Brown, D. Dowell, M.P. Dunning, S. Gilevich, K. Grouev, B.T. Jacobson, X. Liu, A. Miahnahri, J.F. Schmerge, T. Vecchione SLAC, Menlo Park, California, USA G. Huang, F. Sannibale LBNL, Berkeley, California, USA
	Funding: work supported by DOE under grant No. DE-AC02-76SF00515 A 4 GeV 1.3 GHz superconducting linac is being constructed at SLAC as part of the X-ray free electron laser project (LCLS-II). The first 3-meter of the electron source that includes a normal conducting 185.7MHz CW RF gun, 2-cell 1.3 GHz CW RF buncher, and a loadlock system for cathode changes was designed and built by LBNL based on their experience with similar one for advanced photo-injector experiment program. The electron beam is designed to operate at a high repetition rate, up to 1 MHz. Since summer of 2018 we started LCLS-II injector source commissioning immediately after the major installation completion. This paper presents major commissioning results including achievements of ultra-high vacuum, RF processing to CW nominal power, dark current characterization and mitigation, and high-brightness electron beam measurements.
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA05	Record High Extraction Efficiency of Free electron Laser Oscillator
	H. Zen, H. Ohgaki Kyoto University, Kyoto, Japan R. Hajima QST, Tokai, Japan
	Funding: This work was supported by the MEXT Quantum Leap Flagship Program (MEXT Q-LEAP) Grant Number JPMXS0118070271. The highest extraction efficiency (9.4%) of a free electron laser (FEL) oscillator has been achieved at the mid-infrared FEL facility of Kyoto University. Because of the interaction between the electron beam and FEL electromagnetic field, a maximum electron energy decrease of 16% was observed. The measured energy decrease was consistent with the measured FEL spectrum. An FEL micro-pulse energy of approximately 100 micro-J with micro-pulse duration of 150 fs was observed. This result is an important milestone for the high-extraction-efficiency FEL oscillator and will contribute to the strong-field physics of atoms and molecules. H. Zen et al., Appl. Phys. Express 13, 102007 (2020).
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA06	Mitigation of Beam Instabilities in the Echo-Enabled Harmonic Generation Beamline for FLASH2020+	4514
	F. Pannek, W. Hillert, D. Samoilenko University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Ackermann, E. Allaria, P. Niknejadi, G. Paraskaki, L. Schaper DESY, Hamburg, Germany M.A. Pop MAX IV Laboratory, Lund University, Lund, Sweden
	With the FLASH2020+ upgrade, one of the beamlines of the free-electron laser FLASH at DESY will be based on the Echo-Enabled Harmonic Generation (EEHG) seeding scheme and provide high-repetition-rate, coherent radiation down to 4 nm. To reach this wavelength, it is necessary to imprint intricate structures on the longitudinal phase space of the electron bunch at a very high harmonic of the seed laser wavelength, making the scheme potentially vulnerable to beam instabilities. Part of the beamline is a strong chicane, which is necessary to create the dispersion required by EEHG. Resulting effects such as Coherent Synchrotron Radiation (CSR) can be very detrimental for the bunching process and have to be taken into account already in the design of the beamline to ensure optimum FEL performance. We investigate and propose possible mitigation solutions to such instabilities in the FLASH2020+ parameter range.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-FRXA06
About •	paper received ※ 19 May 2021 paper accepted ※ 20 July 2021 issue date ※ 20 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXA07	Ringdown Measured in a Four-Bounce, 20 Meter Hard X-Ray Cavity
	J.P. MacArthur, Z. Huang, J. Krzywiński, G. Marcus, R.A. Margraf, T. Sato, D. Zhu SLAC, Menlo Park, California, USA
	Funding: This work was supported by the Department of Energy under contract DE-AC02-76SF00515 A cavity-based hard x-ray free-electron laser (CBXFEL) could produce fully coherent pulses with a bandwidth several orders of magnitude below the intrinsic bandwidth of SASE. A cavity-based FEL is not a new concept - the first FEL was an oscillator operating at 3.4 um - but single-pass amplification of spontaneous radiation was the fastest path to gigawatt x-ray powers. One unproven component of a CBXFEL is a stable, high reflectivity cavity. To address this deficit we present ring-down measurements in a 20 m round-trip cold cavity operating at 9.8 keV. The cavity is composed of four strain-relief-cut diamond 400 Bragg mirrors and a transmission grating for in/out-coupling. It is a testbed for alignment protocols and component performance under realistic experimental conditions like source instability, optics imperfections, and thermal drift.
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)