FEL2013 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOPSO77	Timing Jitter Measurements of the SwissFEL Test Injector	laser, gun, electron, cathode	140
	C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger PSI, Villigen PSI, Switzerland C.P. Hauri EPFL, Lausanne, Switzerland
	To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

TUOANO02	Long-term Stable, Large-scale, Optical Timing Distribution Systems With Sub-femtosecond Timing Stability	laser, polarization, optics, electron	156
	M.Y. Peng, P.T. Callahan, F.X. Kaertner, A.H. Nejadmalayeri MIT, Cambridge, Massachusetts, USA K. Ahmed, S. Valente, M. Xin DESY, Hamburg, Germany P. Battle, T.D. Roberts AdvR, Inc., Montana, USA J.M. Fini, L. Grüner-Nielsen, E. Monberg, M. Yan OFS Laboratories, New Jersey, USA F.X. Kaertner CFEL, Hamburg, Germany
	Funding: US Department of Energy Contract DE-SC0005262 and Center for Free-Electron Laser Science, DESY, Hamburg Sub-fs X-ray pulse generation in kilometer-scale FEL facilities will require sub-fs long-term timing stability between optical sources over kilometer distances. We present here key developments towards a completely fiber-coupled, sub-fs optical timing distribution system. Our approach [] is to lock a femtosecond pulsed laser to a microwave reference and distribute its pulse train through fiber links stabilized by balanced optical cross-correlators (BOCs) []. First, we verified that low-noise optical master oscillators for sub-fs timing distribution are available today; the measured jitter for two commercial femtosecond lasers is less than 70 as for frequencies above 1 kHz. Second, we developed a novel 1.2 km dispersion-compensated, polarization-maintaining fiber link to eliminate drifts induced by polarization mode dispersion. Link stabilization for 16 days showed 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Lastly, we fabricated a hybrid-integrated BOC using PPKTP waveguides [*] to eliminate alignment drifts and to reduce the link operation power by a factor of 10-100, which will reduce timing errors induced by fiber nonlinearities. J. Kim et al., Nat. Photon., 2, 12, 733–736, 2008. J. Kim et al., Opt. Lett., 32, 9, 1044–1046, 2007. * A. H. Nejadmalayeri et al., Opt. Lett., 34, 16, 2522–2524, 2009.
	Slides TUOANO02 [1.387 MB]

TUPSO15	Beam Diagnostic Requirements for the Next Generation Light Source	diagnostics, linac, emittance, FEL	242
	S. De Santis, J.M. Byrd, J.N. Corlett, P. Emma, D. Filippetto, M. Placidi, H.J. Qian, F. Sannibale LBNL, Berkeley, California, USA
	Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The NGLS project consists in a 2.4 GeV superconducting linac accelerating sub-1 μm normalized emittance bunches used to produce high intensity soft X-ray short pulses from multiple FEL beamlines. The 1 MHz bunch repetition rate, and the consequent high beam power, present special challenges, but also opportunities, in the design of the various electron beam diagnostic devices. The wide range of beam characteristics, from the photoinjector to the undulators, require the adoption of different diagnostics optimized to each machine section and to the specific application of each individual measurement. In this paper we present our plans for the NGLS beam diagnostics, discussing the special requirements and challenges.

TUPSO19	The Photocathode Laser System for the APEX High Repetition Rate Photoinjector	laser, cathode, electron, controls	255
	D. Filippetto, L.R. Doolittle, G. Huang, G. Marcus, H.J. Qian, F. Sannibale LBNL, Berkeley, California, USA
	Funding: DOE grants No. DE-AC02-05CH11231. The APEX injector has been built and commissioned at LBNL. A CW-RF Gun accelerates electron bunches to up 750 keV at MHz repetition rate. Different high efficiency photocathodes with different work functions are being tested with the help of a load lock system. The photocathode drive laser is thus conceived to provide up to 40 nJ per pulse in the UV and 200 nJ per pulse in the green at 1 MHz, with transverse and longitudinal shaping (flat top, up to 60 ps) for electron beam creation. A transfer line of about 15 meters has been designed and optimized for minimal jitters. Remote control of repetition rate, energy and position have been implemented on the system, together with offline and online diagnostic for beam monitoring. Here we present the laser system setup as well as the first measurements on longitudinal pulse shaping and jitter characterization.

WEPSO46	Study on the fluctuation of electron beam position in KU-FEL	gun, FEL, electron, cavity	602
	K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen Kyoto University, Institute for Advanced Energy, Kyoto, Japan
	Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power. [1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

THOANO01	Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator	FEL, electron, laser, undulator	728
	H. Tomizawa, T. Hara, T. Ishikawa, K. Ogawa, H. Tanaka, T. Tanaka, T. Togashi, K. Togawa, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama, K. Yamakawa JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada, T. Sato, K. Yamanouchi The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Watanabe JASRI/SPring-8, Hyogo, Japan K. Midorikawa, E. Takahashi RIKEN, Saitama, Japan
	We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed.
	Slides THOANO01 [11.493 MB]

Paper

Title

Other Keywords

Page

MOPSO77

Timing Jitter Measurements of the SwissFEL Test Injector

laser, gun, electron, cathode

140

C. Vicario, B. Beutner, M.C. Divall, C.P. Hauri, S. Hunziker, M.G. Kaiser, M. Luethi, M. Pedrozzi, T. Schietinger
PSI, Villigen PSI, Switzerland
C.P. Hauri
EPFL, Lausanne, Switzerland

To reach nominal bunch compression and FEL performance of SwissFEL with stable beam conditions for the users, less than 40fs relative rms jitter is required from the injector. Phase noise measurement of the gun laser oscillator shows an exceptional 30fs integrated rms jitter. We present these measurements and analyze the contribution to the timing jitter and drift from the rest of the laser chain. These studies were performed at the SwissFEL injector test facility, using the rising edge of the Schottky-scan curve and on the laser system using fast digital signal analyzer and photodiode, revealing a residual jitter of 150fs at the cathode from the pulsed laser amplifier and beam transport, measured at 10Hz. Spectrally resolved cross-correlation technique will also be reviewed here as a future solution of measuring timing jitter at 100Hz directly against the pulsed optical timing link with an expected resolution in the order of 50fs. This device will provide the signal for feedback systems compensating for long term timing drift of the laser for the gun as well as for the pulsed lasers at the experimental stations.

TUOANO02

Long-term Stable, Large-scale, Optical Timing Distribution Systems With Sub-femtosecond Timing Stability

laser, polarization, optics, electron

156

M.Y. Peng, P.T. Callahan, F.X. Kaertner, A.H. Nejadmalayeri
MIT, Cambridge, Massachusetts, USA
K. Ahmed, S. Valente, M. Xin
DESY, Hamburg, Germany
P. Battle, T.D. Roberts
AdvR, Inc., Montana, USA
J.M. Fini, L. Grüner-Nielsen, E. Monberg, M. Yan
OFS Laboratories, New Jersey, USA
F.X. Kaertner
CFEL, Hamburg, Germany

Funding: US Department of Energy Contract DE-SC0005262 and Center for Free-Electron Laser Science, DESY, Hamburg
Sub-fs X-ray pulse generation in kilometer-scale FEL facilities will require sub-fs long-term timing stability between optical sources over kilometer distances. We present here key developments towards a completely fiber-coupled, sub-fs optical timing distribution system. Our approach [*] is to lock a femtosecond pulsed laser to a microwave reference and distribute its pulse train through fiber links stabilized by balanced optical cross-correlators (BOCs) [**]. First, we verified that low-noise optical master oscillators for sub-fs timing distribution are available today; the measured jitter for two commercial femtosecond lasers is less than 70 as for frequencies above 1 kHz. Second, we developed a novel 1.2 km dispersion-compensated, polarization-maintaining fiber link to eliminate drifts induced by polarization mode dispersion. Link stabilization for 16 days showed 0.6 fs RMS timing drift and during a 3-day interval only 0.13 fs drift. Lastly, we fabricated a hybrid-integrated BOC using PPKTP waveguides [***] to eliminate alignment drifts and to reduce the link operation power by a factor of 10-100, which will reduce timing errors induced by fiber nonlinearities.
* J. Kim et al., Nat. Photon., 2, 12, 733–736, 2008.
** J. Kim et al., Opt. Lett., 32, 9, 1044–1046, 2007.
*** A. H. Nejadmalayeri et al., Opt. Lett., 34, 16, 2522–2524, 2009.

Slides TUOANO02 [1.387 MB]

TUPSO15

Beam Diagnostic Requirements for the Next Generation Light Source

diagnostics, linac, emittance, FEL

242

S. De Santis, J.M. Byrd, J.N. Corlett, P. Emma, D. Filippetto, M. Placidi, H.J. Qian, F. Sannibale
LBNL, Berkeley, California, USA

Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
The NGLS project consists in a 2.4 GeV superconducting linac accelerating sub-1 μm normalized emittance bunches used to produce high intensity soft X-ray short pulses from multiple FEL beamlines. The 1 MHz bunch repetition rate, and the consequent high beam power, present special challenges, but also opportunities, in the design of the various electron beam diagnostic devices. The wide range of beam characteristics, from the photoinjector to the undulators, require the adoption of different diagnostics optimized to each machine section and to the specific application of each individual measurement. In this paper we present our plans for the NGLS beam diagnostics, discussing the special requirements and challenges.

TUPSO19

The Photocathode Laser System for the APEX High Repetition Rate Photoinjector

laser, cathode, electron, controls

255

D. Filippetto, L.R. Doolittle, G. Huang, G. Marcus, H.J. Qian, F. Sannibale
LBNL, Berkeley, California, USA

Funding: DOE grants No. DE-AC02-05CH11231.
The APEX injector has been built and commissioned at LBNL. A CW-RF Gun accelerates electron bunches to up 750 keV at MHz repetition rate. Different high efficiency photocathodes with different work functions are being tested with the help of a load lock system. The photocathode drive laser is thus conceived to provide up to 40 nJ per pulse in the UV and 200 nJ per pulse in the green at 1 MHz, with transverse and longitudinal shaping (flat top, up to 60 ps) for electron beam creation. A transfer line of about 15 meters has been designed and optimized for minimal jitters. Remote control of repetition rate, energy and position have been implemented on the system, together with offline and online diagnostic for beam monitoring. Here we present the laser system setup as well as the first measurements on longitudinal pulse shaping and jitter characterization.

WEPSO46

Study on the fluctuation of electron beam position in KU-FEL

gun, FEL, electron, cavity

602

K. Okumura, M. Inukai, T. Kii, T. Konstantin, K. Masuda, K. Mishima, H. Negm, H. Ohgaki, M. Omer, Y. Tsugamura, K. Yoshida, H. Zen
Kyoto University, Institute for Advanced Energy, Kyoto, Japan

Stability of electron beam is important for stable FEL operation. In Kyoto University MIR-FEL facility (KU-FEL), a BPM (Beam Position Monitor) system consisting of six 4-button electrode type BPMs was installed for monitoring of the electron beam position. The fluctuation of the electron beam position has been observed in horizontal and vertical directions. The origin of the beam position fluctuation is not clarified. In horizontal direction, the main fluctuation source is expected to be the energy fluctuation. As the one of candidate of the energy fluctuation, the cavity temperature of the RF gun has been suspected because the gun is operated in detuned condition [1] which enhances beam energy dependence on the cavity temperature. Another candidate is considered to be the fluctuation of the RF power fed to the gun. Therefore, we start to study the effect of the cavity temperature and the RF power on the position of electron beam. In this conference, we will present the measured result and numerical evaluation of the beam position dependence on temperature and RF power.
[1] H. Zen, et al, “Beam Energy Compensation in a Thermionic RF Gun by Cavity Detuning,” IEEE transaction on nuclear science, Vol.56, No. 3, Pages 1487-1491 (2009)

THOANO01

Stable Operation of HHG-Seeded EUV-FEL at the SCSS Test Accelerator

FEL, electron, laser, undulator

728

H. Tomizawa, T. Hara, T. Ishikawa, K. Ogawa, H. Tanaka, T. Tanaka, T. Togashi, K. Togawa, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama, K. Yamakawa
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada, T. Sato, K. Yamanouchi
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Watanabe
JASRI/SPring-8, Hyogo, Japan
K. Midorikawa, E. Takahashi
RIKEN, Saitama, Japan

We performed the higher-order harmonic (HH) seeded FEL operation at a 61.2 nm fundamental wavelength, using a seeding source of HH pulses from a Ti:sapphire laser at the SCSS (EUV-FEL) accelerator. It is important for the HH seeded FEL scheme to synchronize the seeding laser pulses to the electron bunches. We constructed the relative arrival timing monitor based on Electro-Optic sampling (EOS). Since the EOS-probe laser pulses were optically split from HH-driving laser pulses, the arrival time difference of the seeding laser pulses, with respect to the electron bunches, were measured bunch-by-bunch. This non-invasive EOS monitor made uninterrupted, real-time monitoring possible even during the seeded FEL operation. The EOS system was used for the arrival timing feedback with a few-hundred-femtosecond adjustability for continual operation of the HH-seeded FEL. By using the EOS-locking system, the HH seeded FEL was operated over half a day with a 20-30% hit rate. The output pulse energy reached 20uJ at the 61.2 nm wavelength. A user experiment was performed by using the seeded EUV-EL and a clear difference between the SASE-FEL and the seeded FEL was observed.

Slides THOANO01 [11.493 MB]