FEL2017 - List of Authors (Qian, H.J.)

Paper	Title	Page
WEP005	Coaxial Coupler RF Kick in the PITZ RF Gun	422
	Y. Chen, P. Boonpornprasert, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan DESY Zeuthen, Zeuthen, Germany W. Ackermann, H. De Gersem TEMF, TU Darmstadt, Darmstadt, Germany M. Dohlus DESY, Hamburg, Germany Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	We investigate a transverse RF kick induced by the transition between rectangular waveguide and coaxial line of the RF coupler in the 1.6-cell L-band normal conducting (NC) RF gun at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). A three-dimensional electromagnetic simulation shows the disturbed RF field distributions in the fundamental accelerating mode. Based on the 3D RF field map, an electron beam based characterization and quantification of the coaxial coupler RF kick in the PITZ gun is simulated. Preliminary results of the investigations are presented.
	Poster WEP005 [1.345 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP005
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP006	Preliminary On-Table and Photoelectron Results from the PITZ Quasi-Ellipsoidal Photocathode Laser System	426
	J.D. Good, G. Asova, P. Boonpornprasert, Y. Chen, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan DESY Zeuthen, Zeuthen, Germany A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky IAP/RAS, Nizhny Novgorod, Russia I. Hartl, S. Schreiber DESY, Hamburg, Germany E. Syresin JINR, Dubna, Moscow Region, Russia
	The optimization of photoinjectors is crucial for the successful operation of linac-based free electron lasers, and beam dynamics simulations have shown that ellipsoidal photocathode laser pulses result in significantly lower electron beam emittance than that of conventional cylindrical pulses. Therefore, in collaboration with the Institute of Applied Physics (Nizhny Novgorod, Russia) and the Joint Institute of Nuclear Research (Dubna, Russia), a laser system capable of generating quasi-ellipsoidal laser pulses has been developed and installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The pulse shaping has been realized using the spatial light modulator technique, characterized by cross-correlation and spectrographic measurements, and is demonstrated with electron beam measurements. In this contribution the overall setup, operating principles, and results of first regular electron beam measurements will be presented together with corresponding beam dynamics simulations. Furthermore, the numerous improvements of the simplified re-design currently under construction shall be detailed.
	Poster WEP006 [1.766 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP006
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP007	Electron Beam Asymmetry Compensation with Gun Quadrupoles at PITZ	429
	M. Krasilnikov, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao DESY Zeuthen, Zeuthen, Germany G.A. Amatuni, B. Grigoryan CANDLE SRI, Yerevan, Armenia G. Asova INRNE, Sofia, Bulgaria Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	The electron beam asymmetry observed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) was traced back to multipole kicks in the gun section, namely around the location of the coaxial power coupler and the main solenoid. Several dedicated studies have been performed to quantify the kick location and strength. Based on these studies, two designs of correction quadrupole coils were proposed. The coils were fabricated and tested with an electron beam. The second updated design implies a two quadrupole setup on a frame installed around the gun coaxial coupler close to the main solenoid centre location. Skew and normal quadrupole magnets are powered independently, enabling flexibility in electron beam manipulations. By means of this setup, a more symmetric beam was obtained at several screens. This led also to more equal measured horizontal and vertical phase spaces and to even smaller overall emittance values. Some details of the gun quadrupole designs, magnetic measurements, and results of electron beam measurements including emittance optimization will be reported.
	Poster WEP007 [1.997 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP007
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP008	Beam Brightness Improvement by Ellipsoidal Laser Shaping for CW Photoinjectors	432
	H.J. Qian, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany
	High-brightness photoinjectors operating in a continuous wave (CW) mode are required for many advanced applications, such as CW X-ray FEL, ERL light source, electron coolers for hadron beams and electron-ion colliders and so on. Now, three types of CW electron guns are available: DC gun, SRF gun and normal conducting RF gun, which are under intense development in different institutes based on local expertise and application demands. Compared to pulsed guns, both beam energy and brightness from CW guns are compromised due to a lower acceleration gradient. Flattop laser shaping has been applied in both pulsed and CW guns to improve beam emittance. In this paper, ellipsoidal laser shaping is applied in CW photoinjectors to improve beam brightness, and preliminary ASTRA simulations are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP009	A Cryocooled Normal-Conducting and Superconducting Hybrid CW Photoinjector	436
	H.J. Qian, M. Krasilnikov, F. Stephan DESY Zeuthen, Zeuthen, Germany
	Continuous wave (CW) photoinjectors have seen great progress in the last decades, such as DC gun, SRF gun and normal conducting VHF-band RF gun. New developments of CW guns are aiming higher acceleration gradient and beam energy for higher-beam brightness. One of the technical challenges for CW SRF guns is the compatibility of normal-conducting high QE cathodes and superconducting cavity. In this paper, a high gradient cryocooled CW normal-conducting gun is proposed to house the high QE cathode, and a SRF cavity nearby gives further energy acceleration. Preliminary ASTRA simulations of such a hybrid photoinjector are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP010	Beam Asymmetry Studies with Quadrupole Field Errors in the PITZ Gun Section	440
	Q.T. Zhao, G. Asova, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, C. Saisa-ard, F. Stephan DESY Zeuthen, Zeuthen, Germany G. Asova INRNE, Sofia, Bulgaria C. Saisa-ard Chiang Mai University, Chiang Mai, Thailand Q.T. Zhao IMP/CAS, Lanzhou, People's Republic of China
	The Photo Injector Test Facility at DESY in Zeuthen (PITZ) was built to test and optimize high-brightness electron sources for free electron lasers (FELs) like FLASH and European XFEL. Although the beam emittance has been optimized and experimentally demonstrated to meet the requirements of FLASH and XFEL, transverse beam asymmetries, such as wing structures and beam tilts, were observed during many years of operation with different generations of guns. These cannot be explained by simulations with the rotationally symmetric gun cavities and symmetric solenoid fields. Based on previous RF coupler kick, solenoid field imperfection studies and coupling beam dynamics, the beam asymmetries most probably stem from rotated quadrupole field error in the gun section. A thin-lens static quadrupole model is applied in the RF gun section simulations to fit the position and intensity of quadrupole field errors by comparing the beam asymmetry directions in experiments and ASTRA simulations. Furthermore, by measuring the laser position movement at the photo cathode and the corresponding beam movement at downstream screens, the integrated quadrupole field strength can also be extracted.
	Poster WEP010 [1.856 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP010
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Coaxial Coupler RF Kick in the PITZ RF Gun

422

Y. Chen, P. Boonpornprasert, J.D. Good, H. Huck, I.I. Isaev, M. Krasilnikov, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan
DESY Zeuthen, Zeuthen, Germany
W. Ackermann, H. De Gersem
TEMF, TU Darmstadt, Darmstadt, Germany
M. Dohlus
DESY, Hamburg, Germany
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

We investigate a transverse RF kick induced by the transition between rectangular waveguide and coaxial line of the RF coupler in the 1.6-cell L-band normal conducting (NC) RF gun at the Photo Injector Test Facility at DESY, Zeuthen site (PITZ). A three-dimensional electromagnetic simulation shows the disturbed RF field distributions in the fundamental accelerating mode. Based on the 3D RF field map, an electron beam based characterization and quantification of the coaxial coupler RF kick in the PITZ gun is simulated. Preliminary results of the investigations are presented.

Poster WEP005 [1.345 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP005

Export •

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

WEP006

Preliminary On-Table and Photoelectron Results from the PITZ Quasi-Ellipsoidal Photocathode Laser System

426

J.D. Good, G. Asova, P. Boonpornprasert, Y. Chen, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, F. Stephan
DESY Zeuthen, Zeuthen, Germany
A.V. Andrianov, E. Gacheva, E. Khazanov, S. Mironov, A. Poteomkin, V. Zelenogorsky
IAP/RAS, Nizhny Novgorod, Russia
I. Hartl, S. Schreiber
DESY, Hamburg, Germany
E. Syresin
JINR, Dubna, Moscow Region, Russia

The optimization of photoinjectors is crucial for the successful operation of linac-based free electron lasers, and beam dynamics simulations have shown that ellipsoidal photocathode laser pulses result in significantly lower electron beam emittance than that of conventional cylindrical pulses. Therefore, in collaboration with the Institute of Applied Physics (Nizhny Novgorod, Russia) and the Joint Institute of Nuclear Research (Dubna, Russia), a laser system capable of generating quasi-ellipsoidal laser pulses has been developed and installed at the Photo Injector Test facility at DESY, Zeuthen site (PITZ). The pulse shaping has been realized using the spatial light modulator technique, characterized by cross-correlation and spectrographic measurements, and is demonstrated with electron beam measurements. In this contribution the overall setup, operating principles, and results of first regular electron beam measurements will be presented together with corresponding beam dynamics simulations. Furthermore, the numerous improvements of the simplified re-design currently under construction shall be detailed.

Poster WEP006 [1.766 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP006

Export •

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

WEP007

Electron Beam Asymmetry Compensation with Gun Quadrupoles at PITZ

429

M. Krasilnikov, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, F. Stephan, Q.T. Zhao
DESY Zeuthen, Zeuthen, Germany
G.A. Amatuni, B. Grigoryan
CANDLE SRI, Yerevan, Armenia
G. Asova
INRNE, Sofia, Bulgaria
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The electron beam asymmetry observed at the Photo Injector Test Facility at DESY in Zeuthen (PITZ) was traced back to multipole kicks in the gun section, namely around the location of the coaxial power coupler and the main solenoid. Several dedicated studies have been performed to quantify the kick location and strength. Based on these studies, two designs of correction quadrupole coils were proposed. The coils were fabricated and tested with an electron beam. The second updated design implies a two quadrupole setup on a frame installed around the gun coaxial coupler close to the main solenoid centre location. Skew and normal quadrupole magnets are powered independently, enabling flexibility in electron beam manipulations. By means of this setup, a more symmetric beam was obtained at several screens. This led also to more equal measured horizontal and vertical phase spaces and to even smaller overall emittance values. Some details of the gun quadrupole designs, magnetic measurements, and results of electron beam measurements including emittance optimization will be reported.

Poster WEP007 [1.997 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP007

Export •

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

WEP008

Beam Brightness Improvement by Ellipsoidal Laser Shaping for CW Photoinjectors

432

H.J. Qian, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany

High-brightness photoinjectors operating in a continuous wave (CW) mode are required for many advanced applications, such as CW X-ray FEL, ERL light source, electron coolers for hadron beams and electron-ion colliders and so on. Now, three types of CW electron guns are available: DC gun, SRF gun and normal conducting RF gun, which are under intense development in different institutes based on local expertise and application demands. Compared to pulsed guns, both beam energy and brightness from CW guns are compromised due to a lower acceleration gradient. Flattop laser shaping has been applied in both pulsed and CW guns to improve beam emittance. In this paper, ellipsoidal laser shaping is applied in CW photoinjectors to improve beam brightness, and preliminary ASTRA simulations are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP008

Export •

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

WEP009

A Cryocooled Normal-Conducting and Superconducting Hybrid CW Photoinjector

436

H.J. Qian, M. Krasilnikov, F. Stephan
DESY Zeuthen, Zeuthen, Germany

Continuous wave (CW) photoinjectors have seen great progress in the last decades, such as DC gun, SRF gun and normal conducting VHF-band RF gun. New developments of CW guns are aiming higher acceleration gradient and beam energy for higher-beam brightness. One of the technical challenges for CW SRF guns is the compatibility of normal-conducting high QE cathodes and superconducting cavity. In this paper, a high gradient cryocooled CW normal-conducting gun is proposed to house the high QE cathode, and a SRF cavity nearby gives further energy acceleration. Preliminary ASTRA simulations of such a hybrid photoinjector are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP009

Export •

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

WEP010

Beam Asymmetry Studies with Quadrupole Field Errors in the PITZ Gun Section

440

Q.T. Zhao, G. Asova, P. Boonpornprasert, Y. Chen, J.D. Good, M. Groß, H. Huck, I.I. Isaev, D.K. Kalantaryan, M. Krasilnikov, X. Li, O. Lishilin, G. Loisch, D.M. Melkumyan, A. Oppelt, H.J. Qian, Y. Renier, T. Rublack, C. Saisa-ard, F. Stephan
DESY Zeuthen, Zeuthen, Germany
G. Asova
INRNE, Sofia, Bulgaria
C. Saisa-ard
Chiang Mai University, Chiang Mai, Thailand
Q.T. Zhao
IMP/CAS, Lanzhou, People's Republic of China

The Photo Injector Test Facility at DESY in Zeuthen (PITZ) was built to test and optimize high-brightness electron sources for free electron lasers (FELs) like FLASH and European XFEL. Although the beam emittance has been optimized and experimentally demonstrated to meet the requirements of FLASH and XFEL, transverse beam asymmetries, such as wing structures and beam tilts, were observed during many years of operation with different generations of guns. These cannot be explained by simulations with the rotationally symmetric gun cavities and symmetric solenoid fields. Based on previous RF coupler kick, solenoid field imperfection studies and coupling beam dynamics, the beam asymmetries most probably stem from rotated quadrupole field error in the gun section. A thin-lens static quadrupole model is applied in the RF gun section simulations to fit the position and intensity of quadrupole field errors by comparing the beam asymmetry directions in experiments and ASTRA simulations. Furthermore, by measuring the laser position movement at the photo cathode and the corresponding beam movement at downstream screens, the integrated quadrupole field strength can also be extracted.

Poster WEP010 [1.856 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP010

Export •

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