FEL2019 - List of Keywords (emittance)

Paper	Title	Other Keywords	Page
TUP037	Optimization of the Transverse Gradient Undulator (TGU) for Application in a Storage Ring Based XFELO	electron, radiation, storage-ring, undulator	131
	Y.S. Li University of Chicago, Chicago, Illinois, USA K. Kim, R.R. Lindberg ANL, Lemont, Illinois, USA
	Funding: U.S. Dept. of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The stringent energy spread requirement of the XFELO poses a challenge for its application in storage rings. One way to overcome this is by using a transverse gradient undulator (TGU) [1]. The TGU gain formula was discussed previously [2]. In this paper, we begin by reviewing the analytical 3D gain formula derived from the gain convolution formula. Following that, we apply numerical optimization to investigate the optimal beam and field parameters for maximal TGU gain. We found that a small emittance ratio (i.e. "flat beam" configuration) has a strong positive impact on TGU gain, as well as other patterns in the optimal parameters. [1] T. I. Smith et al., J. Appl. Phys. 50 (1979) 4580 [2] R. R. Lindberg et al., in Proceedings FEL’13, New York, USA, 2013, pp. 740-748, paper THOBNO02
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP037
About •	paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEB02	Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements	FEL, experiment, electron, operation	307
	G.L. Orlandi, S. Borrelli, Ch. David, E. Ferrari, V. Guzenko, B. Hermann, O. Huerzeler, R. Ischebeck, C. Lombosi, C. Ozkan Loch, E. Prat PSI, Villigen PSI, Switzerland N. Cefarin, S. Dal Zilio, M. Lazzarino IOM-CNR, Trieste, Italy M. Ferianis, G. Penco, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented. [1] M. Veronese et al., NIM-A, 891, 32-36, (2018). [2] S. Borrelli et al., Comm. Phys.-Nature, 1, 52 (2018).
	Slides WEB02 [11.196 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB02
About •	paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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WEP006	A PolariX TDS for the FLASH2 Beamline	electron, photon, FEL, optics	328
	F. Christie, J. Rönsch-Schulenburg, M. Vogt DESY, Hamburg, Germany
	Transverse Deflecting RF-Structures (TDS) are successfully used for longitudinal diagnostic purposes at many Free-Electron Lasers (FEL) (LCLS, FLASH, EU-XFEL, FERMI). Moreover, by installing a TDS downstream of the FEL undulators and placing the measurement screen in a dispersive section, the temporal photon pulse structure can be estimated, as was demonstrated at LCLS and sFLASH. Here we describe the installation of a variable polarization X-band structure (PolariX TDS [1]) downstream of the FLASH2 undulators. The installation of such a TDS enables longitudinal phase space measurements and photon pulse reconstructions, as well as slice emittance measurements in both planes using the same cavity due to the unique variable polarization of the PolariX TDS. [1] P. Craievich et al., "Status of the PolariX-TDS Project", in Proc. IPAC’18, Vancouver, Canada (2018)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP006
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP026	Preliminary Geometry Optimization of a 3.5-Cell SRF Gun Cavity at ELBE Based on Beam Dynamics	SRF, gun, cavity, electron	374
	K. Zhou, P. Li CAEP/IAE, Mianyang, Sichuan, People’s Republic of China A. Arnold, S. Ma, J. Schaber, J. Teichert, R. Xiang HZDR, Dresden, Germany
	At present, ELBE radiation source at HZDR is optimizing the SRF cavity for the next generation ELBE SRF GUN. This paper presents a preliminary study on the geometry optimization of a 3.5-cell SRF gun cavity based on beam dynamics. By changing the lengths of the half cell and the first TESLA like cell, two new cavity models with higher electric field in the half cell are built and their RF fields are compared with SRF GUN I and SRF GUN II. Through the scanning of the RF phases and the electric fields, the simulation results indicate that new models have smaller transverse emittance at relatively lower electric field gradients and better performance on longitudinal emittance than SRF GUN I and SRF GUN II.
	Poster WEP026 [1.345 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP026
About •	paper received ※ 19 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019
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WEP051	PITZ Experimental Optimization for the Aimed Cathode Gradient of a Superconducting CW RF Gun	gun, laser, cathode, SRF	440
	M. Krasilnikov, P. Boonpornprasert, Y. Chen, G.Z. Georgiev, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, S. Lal, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko DESY Zeuthen, Zeuthen, Germany M. Dohlus, E. Vogel DESY, Hamburg, Germany
	A continuous wave (CW) mode operation of the European X-ray Free-Electron Laser (XFEL) is under considerations for a future upgrade. Therefore, a superconducting radio frequency (SRF) CW gun is under experimental development at DESY in Hamburg. Beam dynamics simulations for this setup have been done assuming 100 pC bunch charge and a maximum electric field at the photocathode of 40 MV/m. Experimental studies for these parameters using a normal conducting RF photogun have been performed at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The beam transverse emittance was minimized by optimizing the main photo injector parameters in order to demonstrate the feasibility of generating electron beams with a beam quality required for successful CW operation of the European XFEL for conditions similar to the SRF gun setup.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP051
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP057	Performance Optimization of Low-Emittance DC-SRF Injector Using Cs2Te Photocathode	cavity, electron, SRF, solenoid	463
	S. Zhao Peking University, Beijing, People’s Republic of China S. Huang, K.X. Liu, Y.Q. Liu, D.M. Ouyang PKU, Beijing, People’s Republic of China
	A low-emittance DC-SRF injector (DC-SRF-II) is under construction at Peking University, in the earlier design of which K2CsSb photocathode was chosen. Recently we changed the cathode to Cs2Te, which is more widely used nowadays, and carried out a detailed performance optimization. In this paper, we present our latest simulation results, which show that an emittance under 0.5 mm-mrad can be achieved at the bunch charge of 100 pC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP057
About •	paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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WEP059	Characterizing a Coherent Electron Source Extracted From a Cold Atom Trap	electron, cavity, controls, laser	469
	H. Luo, P.X. Chu, J. Guo, T. Liu, Y.X. Xu, X. Zhao SWUST, Mianyang City, Sichuan Province, People’s Republic of China X.H. Li, Q.H. Zhou Southwest University of Science and Technology, Mianyang, Sichuan, People’s Republic of China K. Wang USTC, Hefei, Anhui, People’s Republic of China
	Funding: The National Natural Science Foundation of China under Grant No. 11875227. In order to generate a fully coherent free electron laser (FEL) within a compact system, one approach is to interact a coherent electron bunch with a high power laser operating in the quantum FEL regime. The coherent electron source is obtained by ionizing the Rydberg atoms in a magneto-optical trap (MOT). The qualities of the electron source will have direct effects on the brightness, coherence, and line width of the free electron laser. A high quality ultra-cold electron source is obtained by carefully optimizing the extraction electrode structure, the acceleration and focusing system as well as the MOT. Through parameter optimization, a coherent electron source with a temperature lower than 10 K is obtained. Details of the optimization and the characteristics of the coherent electron source are reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP059
About •	paper received ※ 24 August 2019 paper accepted ※ 10 September 2019 issue date ※ 05 November 2019
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WEP062	Test of Cs2Te Thickness on Cathode Performance at PITZ	cathode, gun, laser, FEL	473
	P.W. Huang TUB, Beijing, People’s Republic of China Y. Chen, M. Groß, I.I. Isaev, P. Kitisri, C. Koschitzki, M. Krasilnikov, S. Lal, X. Li, O. Lishilin, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach DESY Zeuthen, Zeuthen, Germany A. Grigoryan CANDLE, Yerevan, Armenia S. Lederer DESY, Hamburg, Germany P. Michelato, L. Monaco, D. Sertore INFN/LASA, Segrate (MI), Italy
	Cesium telluride is a widely used cathode in photo injectors, and its performance is one of the keys for not only emittance but also reliable operation. Over the years lots of experiences with Cs2Te photocathodes produced with the same recipe and thickness were gained at the DESY photo injectors, but cathode performance dependence on the cathode layer thickness were not investigated. In this paper, we test fresh Cs2Te cathodes with different thickness at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The QE and thermal emittance of these cathodes inside the high gradient RF gun will be compared. Besides, the injector emittance under the operation conditions of the XFEL will also be measured with these cathodes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP062
About •	paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THB02	Understanding 1D to 3D Coherent Synchrotron Radiation Effects	simulation, radiation, electron, experiment	578
	A.D. Brynes STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch with respect to the quality of the FEL light that it produces. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.
	Slides THB02 [3.591 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB02
About •	paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP020	Microbunching Enhancement by Adiabatic Trapping	bunching, laser, storage-ring, injection	635
	X.J. Deng, W.-H. Huang, C.-X. Tang TUB, Beijing, People’s Republic of China A. Chao SLAC, Menlo Park, California, USA
	Storage ring based concept called steady-state microbunching was proposed years ago for high average power narrowband coherent radiation generation. There are now active efforts on-going by the SSMB collaboration established among Tsinghua University and several other institutes. In this paper we study the particle trap and filamentation process of beam in RF or Micro Bucket which is useful for understanding the injection beam dynamics of SSMB. One remarkable result is the steady-state current distribution after full filamentation has little dependence on the bucket height as long as it is several times larger than the energy spread. A discrete increase of bucket height can boost the bunching, with the sacrifice of emittance growth. An adiabatic change of bucket height from a smaller value to the final desired value is then proposed to boost the bunching while preserving the longitudinal emittance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP020
About •	paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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THP027	Simulation and Optimization of the Transport Beamline for the NovoFEL RF Gun	gun, simulation, electron, solenoid	647
	A.S. Matveev, I.V. Davidyuk, O.A. Shevchenko, V.G. Tcheskidov, N.A. Vinokurov, V. Volkov BINP SB RAS, Novosibirsk, Russia I.V. Davidyuk, A.S. Matveev, N.A. Vinokurov NSU, Novosibirsk, Russia
	A new low-frequency CW RF gun was developed and tested at Budker Institute of Nuclear Physics recently. We plan to use it to upgrade the ERL of the Novosibirsk FEL facility. It will allow increasing the average beam current (due to higher beam repetition rate) and thus increasing the average radiation power. The transport beamline for the RF gun uses the ninety-degree achromatic bend. It is designed in a way that keeps an option to operate with the old electrostatic gun as well. Due to the low beam energy (290 keV) the beam dynamics is strongly influenced by space-charge forces. The paper describes results of simulation and optimization of the RF gun transport beamline. Space-charge forces were taken into account with the code ASTRA. Main sources of emittance degradation were considered in order to decrease their influence during the optimization. In addition, the RF gun output beam parameters were measured for various RF gun emission phases. These experiments were simulated and the results were compared. The resulting beam parameters meets requirements of the Novosibirsk FEL facility ERL.
	Poster THP027 [3.158 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP027
About •	paper received ※ 16 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
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THP035	Beam Shaping for High-Repetition-Rate X-Ray FELs	octupole, electron, FEL, linac	661
	Y. Ding, K.L.F. Bane, Y.M. Nosochkov SLAC, Menlo Park, California, USA
	Beam shaping at normal-conducting, accelerator-based FELs, such as LCLS, plays an important role for improving lasing performance and for supporting special operating modes, such as the self-seeding scheme. Beam shaping methods include horn-collimation and dechirper manipulation. Applying the beam shaping concept to high-repetition-rate FELs driven by a superconducting linac, such as LCLS-II, beam invasive methods are not preferred due to concerns about high power deposition. We have recently studied a few shaping options for LCLS-II, such as manipulating the beam chirp before compression using corrugated devices, and modifying higher order optics terms in a chicane using octupoles. In this report we will discuss the results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP035
About •	paper received ※ 23 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019
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Paper

Title

Other Keywords

Page

TUP037

Optimization of the Transverse Gradient Undulator (TGU) for Application in a Storage Ring Based XFELO

electron, radiation, storage-ring, undulator

131

Y.S. Li
University of Chicago, Chicago, Illinois, USA
K. Kim, R.R. Lindberg
ANL, Lemont, Illinois, USA

Funding: U.S. Dept. of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The stringent energy spread requirement of the XFELO poses a challenge for its application in storage rings. One way to overcome this is by using a transverse gradient undulator (TGU) [1]. The TGU gain formula was discussed previously [2]. In this paper, we begin by reviewing the analytical 3D gain formula derived from the gain convolution formula. Following that, we apply numerical optimization to investigate the optimal beam and field parameters for maximal TGU gain. We found that a small emittance ratio (i.e. "flat beam" configuration) has a strong positive impact on TGU gain, as well as other patterns in the optimal parameters.
[1] T. I. Smith et al., J. Appl. Phys. 50 (1979) 4580
[2] R. R. Lindberg et al., in Proceedings FEL’13, New York, USA, 2013, pp. 740-748, paper THOBNO02

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP037

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paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEB02

Wire-Scanners with Sub-Micrometer Resolution: Developments and Measurements

FEL, experiment, electron, operation

307

G.L. Orlandi, S. Borrelli, Ch. David, E. Ferrari, V. Guzenko, B. Hermann, O. Huerzeler, R. Ischebeck, C. Lombosi, C. Ozkan Loch, E. Prat
PSI, Villigen PSI, Switzerland
N. Cefarin, S. Dal Zilio, M. Lazzarino
IOM-CNR, Trieste, Italy
M. Ferianis, G. Penco, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Monitors of the beam transverse profile with ever more demanding spatial resolution and minimal invasivity are required by the FEL community. In order to improve the spatial resolution towards the sub-micrometer limit as well as to decrease the impact on the lasing process, nano-fabricated wire-scanners have been manufactured independently at PSI and FERMI by means of a lithographic technique [1,2]. Experimental tests carried out at SwissFEL at a low emittance demonstrated the capability of such innovative wire-scanner solutions to resolve beam transverse profiles with a size of 400-500 nm without being affected by any resolution limit. Status and outlook of nano-fabricated wire-scanners will be presented.
[1] M. Veronese et al., NIM-A, 891, 32-36, (2018).
[2] S. Borrelli et al., Comm. Phys.-Nature, 1, 52 (2018).

Slides WEB02 [11.196 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEB02

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paper received ※ 24 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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WEP006

A PolariX TDS for the FLASH2 Beamline

electron, photon, FEL, optics

328

F. Christie, J. Rönsch-Schulenburg, M. Vogt
DESY, Hamburg, Germany

Transverse Deflecting RF-Structures (TDS) are successfully used for longitudinal diagnostic purposes at many Free-Electron Lasers (FEL) (LCLS, FLASH, EU-XFEL, FERMI). Moreover, by installing a TDS downstream of the FEL undulators and placing the measurement screen in a dispersive section, the temporal photon pulse structure can be estimated, as was demonstrated at LCLS and sFLASH. Here we describe the installation of a variable polarization X-band structure (PolariX TDS [1]) downstream of the FLASH2 undulators. The installation of such a TDS enables longitudinal phase space measurements and photon pulse reconstructions, as well as slice emittance measurements in both planes using the same cavity due to the unique variable polarization of the PolariX TDS.
[1] P. Craievich et al., "Status of the PolariX-TDS Project", in Proc. IPAC’18, Vancouver, Canada (2018)

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP006

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP026

Preliminary Geometry Optimization of a 3.5-Cell SRF Gun Cavity at ELBE Based on Beam Dynamics

SRF, gun, cavity, electron

374

K. Zhou, P. Li
CAEP/IAE, Mianyang, Sichuan, People’s Republic of China
A. Arnold, S. Ma, J. Schaber, J. Teichert, R. Xiang
HZDR, Dresden, Germany

At present, ELBE radiation source at HZDR is optimizing the SRF cavity for the next generation ELBE SRF GUN. This paper presents a preliminary study on the geometry optimization of a 3.5-cell SRF gun cavity based on beam dynamics. By changing the lengths of the half cell and the first TESLA like cell, two new cavity models with higher electric field in the half cell are built and their RF fields are compared with SRF GUN I and SRF GUN II. Through the scanning of the RF phases and the electric fields, the simulation results indicate that new models have smaller transverse emittance at relatively lower electric field gradients and better performance on longitudinal emittance than SRF GUN I and SRF GUN II.

Poster WEP026 [1.345 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP026

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paper received ※ 19 August 2019 paper accepted ※ 29 August 2019 issue date ※ 05 November 2019

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WEP051

PITZ Experimental Optimization for the Aimed Cathode Gradient of a Superconducting CW RF Gun

gun, laser, cathode, SRF

440

M. Krasilnikov, P. Boonpornprasert, Y. Chen, G.Z. Georgiev, J.D. Good, M. Groß, P.W. Huang, I.I. Isaev, C. Koschitzki, S. Lal, X. Li, O. Lishilin, G. Loisch, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko
DESY Zeuthen, Zeuthen, Germany
M. Dohlus, E. Vogel
DESY, Hamburg, Germany

A continuous wave (CW) mode operation of the European X-ray Free-Electron Laser (XFEL) is under considerations for a future upgrade. Therefore, a superconducting radio frequency (SRF) CW gun is under experimental development at DESY in Hamburg. Beam dynamics simulations for this setup have been done assuming 100 pC bunch charge and a maximum electric field at the photocathode of 40 MV/m. Experimental studies for these parameters using a normal conducting RF photogun have been performed at the Photo Injector Test facility at DESY in Zeuthen (PITZ). The beam transverse emittance was minimized by optimizing the main photo injector parameters in order to demonstrate the feasibility of generating electron beams with a beam quality required for successful CW operation of the European XFEL for conditions similar to the SRF gun setup.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP051

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP057

Performance Optimization of Low-Emittance DC-SRF Injector Using Cs2Te Photocathode

cavity, electron, SRF, solenoid

463

S. Zhao
Peking University, Beijing, People’s Republic of China
S. Huang, K.X. Liu, Y.Q. Liu, D.M. Ouyang
PKU, Beijing, People’s Republic of China

A low-emittance DC-SRF injector (DC-SRF-II) is under construction at Peking University, in the earlier design of which K2CsSb photocathode was chosen. Recently we changed the cathode to Cs2Te, which is more widely used nowadays, and carried out a detailed performance optimization. In this paper, we present our latest simulation results, which show that an emittance under 0.5 mm-mrad can be achieved at the bunch charge of 100 pC.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP057

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paper received ※ 14 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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WEP059

Characterizing a Coherent Electron Source Extracted From a Cold Atom Trap

electron, cavity, controls, laser

469

H. Luo, P.X. Chu, J. Guo, T. Liu, Y.X. Xu, X. Zhao
SWUST, Mianyang City, Sichuan Province, People’s Republic of China
X.H. Li, Q.H. Zhou
Southwest University of Science and Technology, Mianyang, Sichuan, People’s Republic of China
K. Wang
USTC, Hefei, Anhui, People’s Republic of China

Funding: The National Natural Science Foundation of China under Grant No. 11875227.
In order to generate a fully coherent free electron laser (FEL) within a compact system, one approach is to interact a coherent electron bunch with a high power laser operating in the quantum FEL regime. The coherent electron source is obtained by ionizing the Rydberg atoms in a magneto-optical trap (MOT). The qualities of the electron source will have direct effects on the brightness, coherence, and line width of the free electron laser. A high quality ultra-cold electron source is obtained by carefully optimizing the extraction electrode structure, the acceleration and focusing system as well as the MOT. Through parameter optimization, a coherent electron source with a temperature lower than 10 K is obtained. Details of the optimization and the characteristics of the coherent electron source are reported in this paper.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP059

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paper received ※ 24 August 2019 paper accepted ※ 10 September 2019 issue date ※ 05 November 2019

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WEP062

Test of Cs2Te Thickness on Cathode Performance at PITZ

cathode, gun, laser, FEL

473

P.W. Huang
TUB, Beijing, People’s Republic of China
Y. Chen, M. Groß, I.I. Isaev, P. Kitisri, C. Koschitzki, M. Krasilnikov, S. Lal, X. Li, O. Lishilin, D. Melkumyan, R. Niemczyk, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, G. Vashchenko, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
A. Grigoryan
CANDLE, Yerevan, Armenia
S. Lederer
DESY, Hamburg, Germany
P. Michelato, L. Monaco, D. Sertore
INFN/LASA, Segrate (MI), Italy

Cesium telluride is a widely used cathode in photo injectors, and its performance is one of the keys for not only emittance but also reliable operation. Over the years lots of experiences with Cs2Te photocathodes produced with the same recipe and thickness were gained at the DESY photo injectors, but cathode performance dependence on the cathode layer thickness were not investigated. In this paper, we test fresh Cs2Te cathodes with different thickness at the Photo Injector Test Facility at DESY in Zeuthen (PITZ). The QE and thermal emittance of these cathodes inside the high gradient RF gun will be compared. Besides, the injector emittance under the operation conditions of the XFEL will also be measured with these cathodes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WEP062

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paper received ※ 20 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THB02

Understanding 1D to 3D Coherent Synchrotron Radiation Effects

simulation, radiation, electron, experiment

578

A.D. Brynes
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Collective effects such as coherent synchrotron radiation (CSR) can have a strong influence of the properties of an electron bunch with respect to the quality of the FEL light that it produces. In particular, CSR experienced by a bunch on a curved trajectory can increase the transverse emittance of a beam. In this contribution, we present an extension to the well-established 1D theory of CSR by accounting fully for the forces experienced in the entrance and exit transients of a bending magnet. A new module of the General Particle Tracer (GPT) tracking code was developed for this study, showing good agreement with theory. In addition to this analysis, we present experimental measurements of the emittance growth experienced in the FERMI bunch compressor chicane as a function of bunch length. When the bunch undergoes extreme compression, the 1D theory breaks down and is no longer valid. A comparison between the 1D theory, experimental measurements and a number of codes which simulate CSR differently are presented, showing better agreement when the transverse properties of the bunch are taken into account.

Slides THB02 [3.591 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THB02

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paper received ※ 19 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THP020

Microbunching Enhancement by Adiabatic Trapping

bunching, laser, storage-ring, injection

635

X.J. Deng, W.-H. Huang, C.-X. Tang
TUB, Beijing, People’s Republic of China
A. Chao
SLAC, Menlo Park, California, USA

Storage ring based concept called steady-state microbunching was proposed years ago for high average power narrowband coherent radiation generation. There are now active efforts on-going by the SSMB collaboration established among Tsinghua University and several other institutes. In this paper we study the particle trap and filamentation process of beam in RF or Micro Bucket which is useful for understanding the injection beam dynamics of SSMB. One remarkable result is the steady-state current distribution after full filamentation has little dependence on the bucket height as long as it is several times larger than the energy spread. A discrete increase of bucket height can boost the bunching, with the sacrifice of emittance growth. An adiabatic change of bucket height from a smaller value to the final desired value is then proposed to boost the bunching while preserving the longitudinal emittance.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP020

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paper received ※ 20 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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THP027

Simulation and Optimization of the Transport Beamline for the NovoFEL RF Gun

gun, simulation, electron, solenoid

647

A.S. Matveev, I.V. Davidyuk, O.A. Shevchenko, V.G. Tcheskidov, N.A. Vinokurov, V. Volkov
BINP SB RAS, Novosibirsk, Russia
I.V. Davidyuk, A.S. Matveev, N.A. Vinokurov
NSU, Novosibirsk, Russia

A new low-frequency CW RF gun was developed and tested at Budker Institute of Nuclear Physics recently. We plan to use it to upgrade the ERL of the Novosibirsk FEL facility. It will allow increasing the average beam current (due to higher beam repetition rate) and thus increasing the average radiation power. The transport beamline for the RF gun uses the ninety-degree achromatic bend. It is designed in a way that keeps an option to operate with the old electrostatic gun as well. Due to the low beam energy (290 keV) the beam dynamics is strongly influenced by space-charge forces. The paper describes results of simulation and optimization of the RF gun transport beamline. Space-charge forces were taken into account with the code ASTRA. Main sources of emittance degradation were considered in order to decrease their influence during the optimization. In addition, the RF gun output beam parameters were measured for various RF gun emission phases. These experiments were simulated and the results were compared. The resulting beam parameters meets requirements of the Novosibirsk FEL facility ERL.

Poster THP027 [3.158 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP027

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paper received ※ 16 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

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THP035

Beam Shaping for High-Repetition-Rate X-Ray FELs

octupole, electron, FEL, linac

661

Y. Ding, K.L.F. Bane, Y.M. Nosochkov
SLAC, Menlo Park, California, USA

Beam shaping at normal-conducting, accelerator-based FELs, such as LCLS, plays an important role for improving lasing performance and for supporting special operating modes, such as the self-seeding scheme. Beam shaping methods include horn-collimation and dechirper manipulation. Applying the beam shaping concept to high-repetition-rate FELs driven by a superconducting linac, such as LCLS-II, beam invasive methods are not preferred due to concerns about high power deposition. We have recently studied a few shaping options for LCLS-II, such as manipulating the beam chirp before compression using corrugated devices, and modifying higher order optics terms in a chicane using octupoles. In this report we will discuss the results.

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reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP035

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paper received ※ 23 August 2019 paper accepted ※ 28 August 2019 issue date ※ 05 November 2019

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