IPAC2017 - List of Keywords (brightness)

Paper	Title	Other Keywords	Page
MOPAB059	Energy Chirp Measurements by Means of an RF Deflector: a Case Study the Gamma Beam Source LINAC at ELI-NP	electron, linac, detector, simulation	242
	L. Sabato U. Sannio, Benevento, Italy P. Arpaia, A. Liccardo Naples University Federico II, Science and Technology Pole, Napoli, Italy A. Mostacci, L. Palumbo University of Rome La Sapienza, Rome, Italy A. Variola INFN/LNF, Frascati (Roma), Italy
	RF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB059
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MOPIK011	Electron Beam Generation From InGaN/GaN Superlattice Photocathode	electron, laser, polarization, gun	522
	N. Yamamoto KEK, Ibaraki, Japan M. Hosaka, A. Mano, T. Miyauchi, Y. Takashima Nagoya University, Nagoya, Japan M. Katoh UVSOR, Okazaki, Japan
	GaAs-type photocathode (PC) has been used as electron spin polarization (ESP) sources for various applications. Recently, by using a strain-compensated technique for GaAs/GaAsP, the super lattice (SL) thickness of up to 720 nm could be manufactured and the quantum efficiency (QE) improvements with the thickness increases was observed. In the experiments, the ESP degradation was also observed for the thicker thickness samples than 194nm and we considered that electron spin relaxation during diffusion process in the PC caused the degradation. Therefore, we propose developing fcc-GaN based PCs instead of GaAs because a factor of ten longer spin relaxation time compared with GaAs/GaAsP SL was reported. However an fcc-GaN sample with adequate dimensions for PC applications is not available at present due to manufacturing difficulties. Then at the start of GaN-type PC development, an hcp-GaN sample has been studied. In the study, NEA-activation was made for an InGaN/GaN SL sample and QE, surface lifetime and ESP were measured. The QE and ESP values were 1.3% and 2.1% at the pump laser wavelength of 405nm.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK011
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MOPIK019	Upgrade Options Towards Higher Fields and Beam Energies for Continuous-Wave Room-Temperature VHF RF Guns	gun, electron, cathode, cavity	542
	F. Sannibale, J.M. Byrd, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, J.W. Staples, S.P. Virostek 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 Science demand for MHz-class repetition rate electron beam applications such as free electron lasers (FELs), inverse Compton scattering sources, and ultrafast electron diffraction and microscopy (UED/UEM), pushed the development of new gun schemes that could generate high brightness beams at such high rates. At the Lawrence Berkeley Lab (LBNL), we proposed a new concept room-temperature RF gun resonating in the VHF frequency range (30-300 MHz) capable of operating in continuous wave mode at the fields required for high-brightness performance. A first VHF-Gun was constructed and tested in the APEX facility at LBNL, which successfully demonstrated all design parameters and the generation of high brightness electron beams. A second version of the APEX VHF-Gun is being built at LBNL for the LCLS-II, the new SLAC X-ray FEL. Recent studies showed that a proposed LCLS-II upgrade and UED/UEM applications would greatly benefit from an increased gun brightness obtained by raising the electric field at the cathode and the beam energy at the gun exit. In this paper, we present and discuss possible upgrade options that would allow extension of the VHF-Gun performance towards these new goals.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK019
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MOPVA002	Initial Stage of Self Amplified Radiation Emission From Electron Bunches in Crystal: Linear Response Theory	radiation, electron, polarization, undulator	848
	A.I. Benediktovitch, I. Lobach BSU, Minsk, Belarus, Belarus
	Self amplified spontaneous emission (SASE) is a key process in X-ray free electron lasers' operation. In this case the spontaneous emission is undulator radiation emission, the radiation in X-ray range being possible from electrons in GeV energy range. In the case of interaction of electrons with properly aligned crystal the channeling radiation results in X-rays from electrons with energies in tens MeV energy range. In this situation for high current densities the SASE process may take place that potentially could lead to construction of a compact bright X-ray source. In present contribution the first principle theoretical description is outlined and first order perturbation theory is used to model the initial stage of SASE. The transition from spontaneous to SASE regime is described, the requirements for bunch current and emittance are determined. By means of dispersion equation analysis and boundary condition application the intensity radiated from crystal slab is calculated and it is shown that Bragg diffraction could enhance self amplification. A numerical example for Si (001) illustrates the model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA002
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TUPAB055	Development of compact magnetic field measurement system available for in-vacuum undulators	undulator, vacuum, emittance, photon	1449
	M. Adachi, R. Kato, T. Shioya, K. Tsuchiya KEK, Ibaraki, Japan
	A low-emittance 3-GeV KEK-LS* ring has been designed at KEK. KEK-LS's undulators can produce extremely high brightness light ranging from VUV to X-ray. Brightness of undulator light strongly depends on the phase error of its periodic magnetic field. Then a precise magnetic field adjustment is required in order to prevent the reduction of the brightness performance. Generally, the adjustment is performed by the conventional field measurement system equipped with hole-probes on a huge stone table. But, for the in-vacuum undulator, the measurement must be performed without the vacuum chamber. The additional phase error caused by reattaching the chamber is not negligible for the low emittance rings. Therefore, some groups have developed measurement systems available for the direct field measurement inside the chamber,. We have started to develop a compact measurement system. Our system is compacted and stabilized by utilizing the rigid metal beam of the undulator frame instead of the stone table. In the conference, we will report the detail of the system and the present status of the development. KEK-LS HP, http://kekls.kek.jp/ T. Tanaka, et al., Physical Review ST-AB, vol.12, p.120702 (2009). * M. Musardo, et al., Proceedings of IPAC2015, Richmond, VA, USA, p.1693 (2015).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB055
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TUPAB129	Optimization of Beam Dynamics for an S-Band Ultra-High Gradient Photoinjector	gun, electron, emittance, cathode	1626
	A.D. Cahill, A. Fukasawa, J.B. Rosenzweig UCLA, Los Angeles, California, USA C. Limborg, W. Qin SLAC, Menlo Park, California, USA
	Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship. Travel to IPAC'17 supported by the Div. of Phys. of the US NSF (Accel. Sci. Prog.) and the Div. of Beam Phys. of the APS New electron sources with improved brightness are desired to enhance the capabilities of FELs, making them more compact and fully coherent. Improvements in electron source brightness can be achieved by increasing electric fields on the cathode of photo-emitted electron guns. Recent developments in pulsed RF accelerator structures show that very high gradient fields can be sustained with low breakdown rates by operating at cryo-temperatures, which when applied to photoguns will lead to a large increase in the electron beam brightness. In particular, our simulations show that when operating with a peak gradient field of 240 MV/m on the cathode of an S-band, electron beam brightness of 80~nC/(mm· mrad)²/mm can be achieved with 100~pC bunches. In this paper, we present the design and optimization of an 1.x cell S-Band RF photoinjector, where the x varies from 4-6. The optimization in brightness has been obtained by using a multi-objective genetic algorithm on the solutions calculated with the ASTRA code. We calculate the optimum length of the rf gun, position of accelerating structure, and laser pulse dimensions for a variety of charges.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB129
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TUPIK068	Parameters Calibration and Compensation-Rematch of Failure Cavities in CADS Injector	cavity, simulation, experiment, rfq	1852
	Y.Z. Jia, W.L. Chen, W.P. Dou, P.H. Gao, H. Jia, S.H. Liu, Y.S. Qin, C. Wang, W.S. Wang, Z.J. Wang IMP/CAS, Lanzhou, People's Republic of China
	Now when a failure on the China Accelerator Driven System (CADS) is detected, the beam will be stopped by the machine protection system (MPS) immediately. But because of the demand of the beam trip (more than 5 min) rate which should be less than 50 times per year [1], it is important to avoid cutting beam down or recover the beam in a short time. The compensation and rematch is of great importance. If the failure is on a cavity, the other cavities should retune to compensate the beam energy, position and phase in order to recover the beam in short time depending on the time of online calculation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPIK068
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TUPVA029	Observations of Emittance Growth in the Presence of External Noise in the LHC	emittance, simulation, damping, experiment	2117
	X. Buffat, C. Tambasco, D. Valuch CERN, Geneva, Switzerland J. Barranco García, T. Pieloni, C. Tambasco EPFL, Lausanne, Switzerland
	Dedicated experiments were perfomed in the LHC to study the impact of noise on colliding high brightness beams. The results are compared to theoretical models and multiparticle tracking simulations. The impacts on the LHC operation and the HL-LHC project are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA029
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WEOBB3	Advancement of an Accelerator-Driven High-Brightness Source for Fast Neutron Imaging	neutron, target, dipole, quadrupole	2533
	B. Rusnak, O. Alford, G.G. Anderson, S.G. Anderson, D.L. Bleuel, J.A. Caggiano, M.L. Crank, S.E. Fisher, P. Fitsos, D.J. Gibson, M. Hall, D.J. Jamero, M.S. Johnson, L. Kruse, K.S. Lange, R.A. Marsh, D. P. Nielsen, J.D. Sain, R. Souza, A. Wiedrick LLNL, Livermore, California, USA
	Funding: This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Lab (LLNL) is building an intense, high-brightness fast neutron source to create millimeter-scale neutron radiographs and images. An intense source (10¹¹ n/s/sr at 0 degrees) of fast neutrons (10 MeV) allows for penetrating very thick, dense objects while preserving the ability to create good image contrast in low density features within the object and maintaining high detector response efficiency. Fast neutrons will be produced using a pulsed 7 MeV, 300 microamp average-current commercial ion accelerator that will deliver deuteron bunches to a 3 atmosphere deuterium gas cell target to produce neutrons by the D(d, n)3He reaction. Due to the high power density of such a tightly focused, modest-energy ion beam, the transport, controls, diagnostics, and in particular the neutron production gas target and beam stop approaches present significant engineering challenges. Progress and status on the building and early commissioning of the lab-scale demonstration machine shall be presented.
	Slides WEOBB3 [2.654 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEOBB3
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WEPAB002	Pushing the MAX IV 3 GeV Storage Ring Brightness and Coherence Towards the Limit of its Magnetic Lattice	optics, lattice, storage-ring, emittance	2557
	S.C. Leemann MAX IV Laboratory, Lund University, Lund, Sweden W.A. Wurtz CLS, Saskatoon, Saskatchewan, Canada
	The MAX IV 3 GeV storage ring is presently being commissioned and crucial parameters such as machine functions, emittance, and stored current have either already been reached or are approaching their design specifications. Once the baseline performance has been achieved, a campaign will be launched to further improve the brightness and coherence of this storage ring for typical x-ray users. During recent years, several such improvements have been designed. Common to these approaches is that they attempt to improve the storage ring performance using existing hardware provided for the baseline design. Such improvements therefore present more short-term upgrades. In this paper, however, we investigate medium-term improvements assuming power supplies can be exchanged in an attempt to push the brightness and coherence of the storage ring to the limit of what can be achieved without exchanging the magnetic lattice itself. We outline optics requirements, the optics optimization process, and summarize achievable parameters. WEPAB075 & WEPAB076 at IPAC17 ** MOPHO05 at PAC2013, TUPRI026 at IPAC'4, PRAB 19 060701 (2016)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB002
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WEPAB023	First Operation of a Harmonic Lasing Self-Seeded FEL	FEL, undulator, electron, operation	2621
	E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov DESY, Hamburg, Germany
	Harmonic lasing is a perspective mode of operation of X-ray FEL user facilities that allows to provide brilliant beams of higher energy photons for user experiments. Another useful application of harmonic lasing is so called Harmonic Lasing Self-Seeded Free Electron Laser (HLSS FEL) that allows to improve spectral brightness of these facilities. In the past, harmonic lasing has been demonstrated in the FEL oscillators in infrared and visible wavelength ranges, but not in high-gain FELs and not at short wavelengths. In this paper we report on the first evidence of the harmonic lasing and the first operation of the HLSS FEL at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. Spectral brightness was improved in comparison with Self-Amplified Spontaneous emission (SASE) FEL by a factor of six in the exponential gain regime. A better performance of HLSS FEL with respect to SASE FEL in the post-saturation regime with a tapered undulator was observed as well. The first demonstration of harmonic lasing in a high-gain FEL and at a short wavelength paves the way for a variety of applications of this new operation mode in X-ray FELs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB023
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WEPAB047	Concept of a New Generation Synchrotron Radiation Facility KEK Light Source	lattice, undulator, cavity, emittance	2687
	T. Honda KEK, Ibaraki, Japan
	KEK has proposed a new SR facility: KEK Light Source (KEK-LS) towards the completion of the first half of the 2020s. The energy and the natural horizontal emittance are 3 GeV and 0.13 nm rad, respectively. To mitigate the intra-beam scattering effect, we are planning to install third harmonic RF cavities. The extremely low emittance ring has been designed based on the Hybrid Multi-Bend Achromatic (HMBA) lattice, which was originally developed at the ESRF upgrade project. We have modified it to insert a short straight section at the center of the unit cell. The number of unit cells is 20, and the circumference is about 570 m. Except for an RF section and an injection section, the ring can accommodate 18 undulators in the long straight sections of 5.6 m, and the additional 20 short straight section of 1.2 m will be used for short-period narrow-gap undulators. If we assume an undulator of the magnetic period 20 mm, total length 5.0 m, and the smallest gap 4 mm, the SR brightness approaches 10²² Photons/mrad²/mm²/s/0.1%B.W. at the X-ray range. It has a high coherent fraction of about 20% at the diffraction limit wavelength 0.32 keV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB047
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WEPAB054	Candidate HEPS Lattice Design With Emittances Approaching the Diffraction Limit of Hard X-Rays	lattice, emittance, dipole, storage-ring	2703
	Y. Jiao, S.Y. Chen, G. Xu IHEP, Beijing, People's Republic of China
	Funding: Work supported by NSFC (11475202, 11405187) The High Energy Photon Source is a 6-GeV, kilometre-scale storage ring light source to be built in Beijing. A lattice of the storage ring was proposed, consisting of 48 hybrid 7BAs, and having a natural emittance of 60 pm and a circumference of ~1.3 km. In this paper, we discuss the possibility of further reducing the emittance to approach the diffraction limit of hard X-ray with 'typical' wavelength of 1 Å. We introduce the considerations on the choice of lattice structure and circumference, and concrete lattice designs.
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WEPAB098	Dielectrically-Loaded Waveguide as a Microwave Undulator for High Brillance X-Rays at 45 - 90 Kev	undulator, photon, operation, coupling	2812
	R. Kustom, A. Nassiri, G.J. Waldschmidt ANL, Argonne, Illinois, USA
	The HEM12 mode in a cylindrical, dielectrically-loaded waveguide provides E and H fields on the central axis that are significantly higher than the fields on the conducting walls. This structure, operating near the cutoff frequency of the HEM12 mode, spans a frequency range where the wavelength and phase velocity vary significantly. This property can be exploited to generate undulator action with short periods for the generation of high brightness x-rays. The frequency range of interest would be from 18 to 34.5-GHz. The goal would be to generate x-rays on the fundamental mode over a range of 45 to 90-kev. The tunability would be achieved by changing the source frequency while maintaining a constant on-axis equivalent undulator field strength of 0.5-T.
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WEPIK121	Computation of Synchrotron Radiation on Arbitrary Geometries in 3D with Modern GPU, Multi-Core, and Grid Computing	GPU, undulator, simulation, radiation	3238
	D.A. Hidas BNL, Upton, Long Island, New York, USA
	Funding: Supported by the U.S. Department of Energy under contract DE-SC0012704 Open Source Code for Advanced Radiation Simulation (OSCARS) is an open source project being developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary particle beams in arbitrary magnetic (and electric) fields on arbitrary geometries in 3D. OSCARS was designed with considerations for modern large scale computing infrastructure. These include the ability to use GPUs for computations, multi-threaded computations, and utilities for grid (or cloud) computing. Primary applications include, but are not limited to, the computation of spectra, photon flux densities, and notably, power density distributions on arbitrary geometries in 3D which is of interest in accelerator component study and design. This modern approach and several complex geometries will be highlighted and elaborated on. http://oscars.bnl.gov
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Paper

Title

Other Keywords

Page

MOPAB059

Energy Chirp Measurements by Means of an RF Deflector: a Case Study the Gamma Beam Source LINAC at ELI-NP

electron, linac, detector, simulation

242

L. Sabato
U. Sannio, Benevento, Italy
P. Arpaia, A. Liccardo
Naples University Federico II, Science and Technology Pole, Napoli, Italy
A. Mostacci, L. Palumbo
University of Rome La Sapienza, Rome, Italy
A. Variola
INFN/LNF, Frascati (Roma), Italy

RF Deflector (RFD) based measurements are widely used in high–brightness electron LINAC around the world in order to measure the ultra–short electron bunch length. The RFD provides a vertical kick to the particles of the electron bunch according to their longitudinal positions. In this paper, a measurement technique for the bunch length and other bunch proprieties, based on the usage of an RFD, is proposed. The basic idea is to obtain information about the bunch length, energy chirp, and energy spread from vertical spot size measurements varying the RFD phase, because they add contributions on this quantity. The case study is the Gamma Beam System (GBS), the Compton Source being built in the Extreme Light Infrastructure–Nuclear Physics (ELI–NP) facility. The ELEctron Generation ANd Tracking (ELEGANT) code is used for tracking the particles from RFD to the measurement screen.

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MOPIK011

Electron Beam Generation From InGaN/GaN Superlattice Photocathode

electron, laser, polarization, gun

522

N. Yamamoto
KEK, Ibaraki, Japan
M. Hosaka, A. Mano, T. Miyauchi, Y. Takashima
Nagoya University, Nagoya, Japan
M. Katoh
UVSOR, Okazaki, Japan

GaAs-type photocathode (PC) has been used as electron spin polarization (ESP) sources for various applications. Recently, by using a strain-compensated technique for GaAs/GaAsP, the super lattice (SL) thickness of up to 720 nm could be manufactured and the quantum efficiency (QE) improvements with the thickness increases was observed. In the experiments, the ESP degradation was also observed for the thicker thickness samples than 194nm and we considered that electron spin relaxation during diffusion process in the PC caused the degradation. Therefore, we propose developing fcc-GaN based PCs instead of GaAs because a factor of ten longer spin relaxation time compared with GaAs/GaAsP SL was reported. However an fcc-GaN sample with adequate dimensions for PC applications is not available at present due to manufacturing difficulties. Then at the start of GaN-type PC development, an hcp-GaN sample has been studied. In the study, NEA-activation was made for an InGaN/GaN SL sample and QE, surface lifetime and ESP were measured. The QE and ESP values were 1.3% and 2.1% at the pump laser wavelength of 405nm.

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MOPIK019

Upgrade Options Towards Higher Fields and Beam Energies for Continuous-Wave Room-Temperature VHF RF Guns

gun, electron, cathode, cavity

542

F. Sannibale, J.M. Byrd, D. Filippetto, M.J. Johnson, D. Li, T.H. Luo, C.E. Mitchell, J.W. Staples, S.P. Virostek
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
Science demand for MHz-class repetition rate electron beam applications such as free electron lasers (FELs), inverse Compton scattering sources, and ultrafast electron diffraction and microscopy (UED/UEM), pushed the development of new gun schemes that could generate high brightness beams at such high rates. At the Lawrence Berkeley Lab (LBNL), we proposed a new concept room-temperature RF gun resonating in the VHF frequency range (30-300 MHz) capable of operating in continuous wave mode at the fields required for high-brightness performance. A first VHF-Gun was constructed and tested in the APEX facility at LBNL, which successfully demonstrated all design parameters and the generation of high brightness electron beams. A second version of the APEX VHF-Gun is being built at LBNL for the LCLS-II, the new SLAC X-ray FEL. Recent studies showed that a proposed LCLS-II upgrade and UED/UEM applications would greatly benefit from an increased gun brightness obtained by raising the electric field at the cathode and the beam energy at the gun exit. In this paper, we present and discuss possible upgrade options that would allow extension of the VHF-Gun performance towards these new goals.

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MOPVA002

Initial Stage of Self Amplified Radiation Emission From Electron Bunches in Crystal: Linear Response Theory

radiation, electron, polarization, undulator

848

A.I. Benediktovitch, I. Lobach
BSU, Minsk, Belarus, Belarus

Self amplified spontaneous emission (SASE) is a key process in X-ray free electron lasers' operation. In this case the spontaneous emission is undulator radiation emission, the radiation in X-ray range being possible from electrons in GeV energy range. In the case of interaction of electrons with properly aligned crystal the channeling radiation results in X-rays from electrons with energies in tens MeV energy range. In this situation for high current densities the SASE process may take place that potentially could lead to construction of a compact bright X-ray source. In present contribution the first principle theoretical description is outlined and first order perturbation theory is used to model the initial stage of SASE. The transition from spontaneous to SASE regime is described, the requirements for bunch current and emittance are determined. By means of dispersion equation analysis and boundary condition application the intensity radiated from crystal slab is calculated and it is shown that Bragg diffraction could enhance self amplification. A numerical example for Si (001) illustrates the model.

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TUPAB055

Development of compact magnetic field measurement system available for in-vacuum undulators

undulator, vacuum, emittance, photon

1449

M. Adachi, R. Kato, T. Shioya, K. Tsuchiya
KEK, Ibaraki, Japan

A low-emittance 3-GeV KEK-LS* ring has been designed at KEK. KEK-LS's undulators can produce extremely high brightness light ranging from VUV to X-ray. Brightness of undulator light strongly depends on the phase error of its periodic magnetic field. Then a precise magnetic field adjustment is required in order to prevent the reduction of the brightness performance. Generally, the adjustment is performed by the conventional field measurement system equipped with hole-probes on a huge stone table. But, for the in-vacuum undulator, the measurement must be performed without the vacuum chamber. The additional phase error caused by reattaching the chamber is not negligible for the low emittance rings. Therefore, some groups have developed measurement systems available for the direct field measurement inside the chamber**,***. We have started to develop a compact measurement system. Our system is compacted and stabilized by utilizing the rigid metal beam of the undulator frame instead of the stone table. In the conference, we will report the detail of the system and the present status of the development.
* KEK-LS HP, http://kekls.kek.jp/
** T. Tanaka, et al., Physical Review ST-AB, vol.12, p.120702 (2009).
*** M. Musardo, et al., Proceedings of IPAC2015, Richmond, VA, USA, p.1693 (2015).

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TUPAB129

Optimization of Beam Dynamics for an S-Band Ultra-High Gradient Photoinjector

gun, electron, emittance, cathode

1626

A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
C. Limborg, W. Qin
SLAC, Menlo Park, California, USA

Funding: Work Supported by DOE/SU Contract DE-AC02-76-SF00515, US NSF Award PHY-1549132, the Center for Bright Beams, and DOE SCGSR Fellowship. Travel to IPAC'17 supported by the Div. of Phys. of the US NSF (Accel. Sci. Prog.) and the Div. of Beam Phys. of the APS
New electron sources with improved brightness are desired to enhance the capabilities of FELs, making them more compact and fully coherent. Improvements in electron source brightness can be achieved by increasing electric fields on the cathode of photo-emitted electron guns. Recent developments in pulsed RF accelerator structures show that very high gradient fields can be sustained with low breakdown rates by operating at cryo-temperatures, which when applied to photoguns will lead to a large increase in the electron beam brightness. In particular, our simulations show that when operating with a peak gradient field of 240 MV/m on the cathode of an S-band, electron beam brightness of 80~nC/(mm· mrad)²/mm can be achieved with 100~pC bunches. In this paper, we present the design and optimization of an 1.x cell S-Band RF photoinjector, where the x varies from 4-6. The optimization in brightness has been obtained by using a multi-objective genetic algorithm on the solutions calculated with the ASTRA code. We calculate the optimum length of the rf gun, position of accelerating structure, and laser pulse dimensions for a variety of charges.

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TUPIK068

Parameters Calibration and Compensation-Rematch of Failure Cavities in CADS Injector

cavity, simulation, experiment, rfq

1852

Y.Z. Jia, W.L. Chen, W.P. Dou, P.H. Gao, H. Jia, S.H. Liu, Y.S. Qin, C. Wang, W.S. Wang, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

Now when a failure on the China Accelerator Driven System (CADS) is detected, the beam will be stopped by the machine protection system (MPS) immediately. But because of the demand of the beam trip (more than 5 min) rate which should be less than 50 times per year [1], it is important to avoid cutting beam down or recover the beam in a short time. The compensation and rematch is of great importance. If the failure is on a cavity, the other cavities should retune to compensate the beam energy, position and phase in order to recover the beam in short time depending on the time of online calculation.

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TUPVA029

Observations of Emittance Growth in the Presence of External Noise in the LHC

emittance, simulation, damping, experiment

2117

X. Buffat, C. Tambasco, D. Valuch
CERN, Geneva, Switzerland
J. Barranco García, T. Pieloni, C. Tambasco
EPFL, Lausanne, Switzerland

Dedicated experiments were perfomed in the LHC to study the impact of noise on colliding high brightness beams. The results are compared to theoretical models and multiparticle tracking simulations. The impacts on the LHC operation and the HL-LHC project are discussed.

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WEOBB3

Advancement of an Accelerator-Driven High-Brightness Source for Fast Neutron Imaging

neutron, target, dipole, quadrupole

2533

B. Rusnak, O. Alford, G.G. Anderson, S.G. Anderson, D.L. Bleuel, J.A. Caggiano, M.L. Crank, S.E. Fisher, P. Fitsos, D.J. Gibson, M. Hall, D.J. Jamero, M.S. Johnson, L. Kruse, K.S. Lange, R.A. Marsh, D. P. Nielsen, J.D. Sain, R. Souza, A. Wiedrick
LLNL, Livermore, California, USA

Funding: This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
Lawrence Livermore National Lab (LLNL) is building an intense, high-brightness fast neutron source to create millimeter-scale neutron radiographs and images. An intense source (10¹¹ n/s/sr at 0 degrees) of fast neutrons (10 MeV) allows for penetrating very thick, dense objects while preserving the ability to create good image contrast in low density features within the object and maintaining high detector response efficiency. Fast neutrons will be produced using a pulsed 7 MeV, 300 microamp average-current commercial ion accelerator that will deliver deuteron bunches to a 3 atmosphere deuterium gas cell target to produce neutrons by the D(d, n)3He reaction. Due to the high power density of such a tightly focused, modest-energy ion beam, the transport, controls, diagnostics, and in particular the neutron production gas target and beam stop approaches present significant engineering challenges. Progress and status on the building and early commissioning of the lab-scale demonstration machine shall be presented.

Slides WEOBB3 [2.654 MB]

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WEPAB002

Pushing the MAX IV 3 GeV Storage Ring Brightness and Coherence Towards the Limit of its Magnetic Lattice

optics, lattice, storage-ring, emittance

2557

S.C. Leemann
MAX IV Laboratory, Lund University, Lund, Sweden
W.A. Wurtz
CLS, Saskatoon, Saskatchewan, Canada

The MAX IV 3 GeV storage ring is presently being commissioned and crucial parameters such as machine functions, emittance, and stored current have either already been reached or are approaching their design specifications*. Once the baseline performance has been achieved, a campaign will be launched to further improve the brightness and coherence of this storage ring for typical x-ray users. During recent years, several such improvements have been designed**. Common to these approaches is that they attempt to improve the storage ring performance using existing hardware provided for the baseline design. Such improvements therefore present more short-term upgrades. In this paper, however, we investigate medium-term improvements assuming power supplies can be exchanged in an attempt to push the brightness and coherence of the storage ring to the limit of what can be achieved without exchanging the magnetic lattice itself. We outline optics requirements, the optics optimization process, and summarize achievable parameters.
* WEPAB075 & WEPAB076 at IPAC17
** MOPHO05 at PAC2013, TUPRI026 at IPAC'4, PRAB 19 060701 (2016)

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WEPAB023

First Operation of a Harmonic Lasing Self-Seeded FEL

FEL, undulator, electron, operation

2621

E. Schneidmiller, B. Faatz, M. Kuhlmann, J. Rönsch-Schulenburg, S. Schreiber, M. Tischer, M.V. Yurkov
DESY, Hamburg, Germany

Harmonic lasing is a perspective mode of operation of X-ray FEL user facilities that allows to provide brilliant beams of higher energy photons for user experiments. Another useful application of harmonic lasing is so called Harmonic Lasing Self-Seeded Free Electron Laser (HLSS FEL) that allows to improve spectral brightness of these facilities. In the past, harmonic lasing has been demonstrated in the FEL oscillators in infrared and visible wavelength ranges, but not in high-gain FELs and not at short wavelengths. In this paper we report on the first evidence of the harmonic lasing and the first operation of the HLSS FEL at the soft X-ray FEL user facility FLASH in the wavelength range between 4.5 nm and 15 nm. Spectral brightness was improved in comparison with Self-Amplified Spontaneous emission (SASE) FEL by a factor of six in the exponential gain regime. A better performance of HLSS FEL with respect to SASE FEL in the post-saturation regime with a tapered undulator was observed as well. The first demonstration of harmonic lasing in a high-gain FEL and at a short wavelength paves the way for a variety of applications of this new operation mode in X-ray FELs.

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WEPAB047

Concept of a New Generation Synchrotron Radiation Facility KEK Light Source

lattice, undulator, cavity, emittance

2687

T. Honda
KEK, Ibaraki, Japan

KEK has proposed a new SR facility: KEK Light Source (KEK-LS) towards the completion of the first half of the 2020s. The energy and the natural horizontal emittance are 3 GeV and 0.13 nm rad, respectively. To mitigate the intra-beam scattering effect, we are planning to install third harmonic RF cavities. The extremely low emittance ring has been designed based on the Hybrid Multi-Bend Achromatic (HMBA) lattice, which was originally developed at the ESRF upgrade project. We have modified it to insert a short straight section at the center of the unit cell. The number of unit cells is 20, and the circumference is about 570 m. Except for an RF section and an injection section, the ring can accommodate 18 undulators in the long straight sections of 5.6 m, and the additional 20 short straight section of 1.2 m will be used for short-period narrow-gap undulators. If we assume an undulator of the magnetic period 20 mm, total length 5.0 m, and the smallest gap 4 mm, the SR brightness approaches 10²² Photons/mrad²/mm²/s/0.1%B.W. at the X-ray range. It has a high coherent fraction of about 20% at the diffraction limit wavelength 0.32 keV.

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WEPAB054

Candidate HEPS Lattice Design With Emittances Approaching the Diffraction Limit of Hard X-Rays

lattice, emittance, dipole, storage-ring

2703

Y. Jiao, S.Y. Chen, G. Xu
IHEP, Beijing, People's Republic of China

Funding: Work supported by NSFC (11475202, 11405187)
The High Energy Photon Source is a 6-GeV, kilometre-scale storage ring light source to be built in Beijing. A lattice of the storage ring was proposed, consisting of 48 hybrid 7BAs, and having a natural emittance of 60 pm and a circumference of ~1.3 km. In this paper, we discuss the possibility of further reducing the emittance to approach the diffraction limit of hard X-ray with 'typical' wavelength of 1 Å. We introduce the considerations on the choice of lattice structure and circumference, and concrete lattice designs.

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WEPAB098

Dielectrically-Loaded Waveguide as a Microwave Undulator for High Brillance X-Rays at 45 - 90 Kev

undulator, photon, operation, coupling

2812

R. Kustom, A. Nassiri, G.J. Waldschmidt
ANL, Argonne, Illinois, USA

The HEM12 mode in a cylindrical, dielectrically-loaded waveguide provides E and H fields on the central axis that are significantly higher than the fields on the conducting walls. This structure, operating near the cutoff frequency of the HEM12 mode, spans a frequency range where the wavelength and phase velocity vary significantly. This property can be exploited to generate undulator action with short periods for the generation of high brightness x-rays. The frequency range of interest would be from 18 to 34.5-GHz. The goal would be to generate x-rays on the fundamental mode over a range of 45 to 90-kev. The tunability would be achieved by changing the source frequency while maintaining a constant on-axis equivalent undulator field strength of 0.5-T.

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WEPIK121

Computation of Synchrotron Radiation on Arbitrary Geometries in 3D with Modern GPU, Multi-Core, and Grid Computing

GPU, undulator, simulation, radiation

3238

D.A. Hidas
BNL, Upton, Long Island, New York, USA

Funding: Supported by the U.S. Department of Energy under contract DE-SC0012704
Open Source Code for Advanced Radiation Simulation (OSCARS*) is an open source project being developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary particle beams in arbitrary magnetic (and electric) fields on arbitrary geometries in 3D. OSCARS was designed with considerations for modern large scale computing infrastructure. These include the ability to use GPUs for computations, multi-threaded computations, and utilities for grid (or cloud) computing. Primary applications include, but are not limited to, the computation of spectra, photon flux densities, and notably, power density distributions on arbitrary geometries in 3D which is of interest in accelerator component study and design. This modern approach and several complex geometries will be highlighted and elaborated on.
* http://oscars.bnl.gov

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