FEL2015 - Table of Session: WEB (FEL Oscillator)

Paper

Title

Page

A Two-Color Storage Ring FEL

571

J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu
FEL/Duke University, Durham, North Carolina, USA
S. Huang
PKU, Beijing, People's Republic of China
J.Y. Li
USTC/NSRL, Hefei, Anhui, People's Republic of China
N. Vinokurov
BINP SB RAS, Novosibirsk, Russia
J. Wu
SLAC, Menlo Park, California, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Using different undulator configurations on the Duke storage ring, we have successfully achieved lasing with a novel two-color storage ring FEL. Using a pair of dual-band FEL mirrors, simultaneous lasing was realized in IR (around 720 nm) and in UV (around 360 nm). With this two-color FEL, we have demonstrated independent wavelength tuning of either IR or UV lasing. With careful tuning, we have also realized harmonic lasing with the UV lasing tuned to the second harmonic of the IR lasing. The tuning of harmonic two-color lasing has also been demonstrated with the locked wavelengths. Furthermore, we have demonstrated good control of the FEL power sharing between the two colors. The two-color FEL has created new opportunities to drive a two-color Compton gamma-ray beam at the High Intensity gamma-ray Source at Duke.

Slides WEB01 [18.975 MB]

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WEB02

Waveguide THz FEL Oscillators

576

S.V. Miginsky, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, J. Mun, S. H. Park, G.I. Shim, N. Vinokurov
KAERI, Daejon, Republic of Korea
S.V. Miginsky, N. Vinokurov
BINP SB RAS, Novosibirsk, Russia

In today's world there is a significant demand for FEL-based THz radiation sources. They have a wide tuning range, a narrow band of radiation, and comparably high peak and average emission power. There are a significant number of these machines in the world, operating or in the development. The main difference between a long-wave FEL, of THz or a millimeter band, and a conventional one is a too big transverse size of the fundamental mode of an open optical resonator. It claims a large gap in an undulator that dramatically decreases its strength. Both factors sorely decrease the amplification and the efficiency, and often make lasing impossible. The main way to solve this problem is to use a waveguide optical resonator. It decreases and controls the transverse size of the fundamental mode. However, the waveguide causes a number of problems: power absorption in its walls; higher modes generation by inhomogeneities, as it is not ideal; electron beam injection into a FEL is more sophisticated; also outcoupling is more complicated; finally, the resonator detuning control claims some special solutions. The waveguide dispersion relation differs from one in the free space. It shifts up the wavelength of the FEL, changes the optimal detuning, and creates a parasitic mode near the critical wavelength of the waveguide. These problems and possible solutions to them are considered.

Slides WEB02 [20.394 MB]

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WEB03

Progress Towards an X-ray FEL Oscillator

K.-J. Kim, T. Kolodziej, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin
ANL, Argonne, Ilinois, USA
J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell
SLAC, Menlo Park, California, USA

Funding: Work at ANL supported under US Department of Energy contract DE-AC02-76SF00515 and at SLAC by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357
Issues and progress in R&D toward realizing an X-ray FEL oscillator will be discussed, including electron injector optimization, X-ray power density evolution on Bragg crystals throughout the lasing process, experimental efforts for testing radiation damage, evaluating the performance of compound refractive lenses (CRLs) as the focusing elements, and the basic considerations for mechanical layout. These will be discussed in the context of a concrete implementation scheme [*] using the 4 GeV superconducting linac to be constructed at the LCLS-II. Time-dependent simulations of harmonic XFELO performance is discussed in another contribution to this conference by Zemella, et al.
[*] T. J. Maxwell et al., Feasibility study for an X-ray free electron laser oscillator, IPAC 2015, Richmond, Virginia, USA

Slides WEB03 [6.452 MB]

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WEB04

Saturation Dynamics, Fine Spectrum, and Chirp Control in a CW FEL Oscillator

580

H. S. Marks, A. Gover, H. Kleinman
University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
D. Borodin, A. Damti, A. Friedman, Y. Vashdi
Ariel University, Ariel, Israel
M. Einat, M. Kanter, Y. Lasser, Yu. Lurie, A. Yahalom
Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel

As in conventional laser physics, the saturation dynamics of a long-pulse Electrostatic Accelerator FEL (EA-FEL) oscillator consists of oscillations build-up, resonator modes competition, and establishment of narrow linewidth single mode lasing. In EA-FEL the gain curve drifts to lower frequencies during the long laser pulse due to inevitable droop in the acceleration voltage. This post-saturation drift renders fine chirp of the single mode laser frequency due to the oscillator frequency pulling effect. We have integrated a voltage-ramping element into the electrostatic accelerator terminal that makes it possible to control the acceleration voltage throughout the lasing pulse. This allows us to keep the voltage constant throughout the e-beam pulse, and so increase the single mode lasing time, avoiding mode-hopping during the pulse due to the drift of the gain curve. Furthermore, by adjusting the voltage ramp rate and polarity we obtained controllable positive/negative laser frequency chirp that can be used in a single pulse sweep for fine spectral line (10^-6) gas-spectroscopy. The study was conducted on the Israeli EA-FEL that operates at tunable frequencies between 95-110 GHz.

Slides WEB04 [2.310 MB]

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Paper	Title	Page
WEB01	A Two-Color Storage Ring FEL	571
	J. Yan, H. Hao, S.F. Mikhailov, V. Popov, Y.K. Wu FEL/Duke University, Durham, North Carolina, USA S. Huang PKU, Beijing, People's Republic of China J.Y. Li USTC/NSRL, Hefei, Anhui, People's Republic of China N. Vinokurov BINP SB RAS, Novosibirsk, Russia J. Wu SLAC, Menlo Park, California, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. Using different undulator configurations on the Duke storage ring, we have successfully achieved lasing with a novel two-color storage ring FEL. Using a pair of dual-band FEL mirrors, simultaneous lasing was realized in IR (around 720 nm) and in UV (around 360 nm). With this two-color FEL, we have demonstrated independent wavelength tuning of either IR or UV lasing. With careful tuning, we have also realized harmonic lasing with the UV lasing tuned to the second harmonic of the IR lasing. The tuning of harmonic two-color lasing has also been demonstrated with the locked wavelengths. Furthermore, we have demonstrated good control of the FEL power sharing between the two colors. The two-color FEL has created new opportunities to drive a two-color Compton gamma-ray beam at the High Intensity gamma-ray Source at Duke.
	Slides WEB01 [18.975 MB]
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WEB02	Waveguide THz FEL Oscillators	576
	S.V. Miginsky, S. Bae, B.A. Gudkov, K.H. Jang, Y.U. Jeong, H.W. Kim, K. Lee, J. Mun, S. H. Park, G.I. Shim, N. Vinokurov KAERI, Daejon, Republic of Korea S.V. Miginsky, N. Vinokurov BINP SB RAS, Novosibirsk, Russia
	In today's world there is a significant demand for FEL-based THz radiation sources. They have a wide tuning range, a narrow band of radiation, and comparably high peak and average emission power. There are a significant number of these machines in the world, operating or in the development. The main difference between a long-wave FEL, of THz or a millimeter band, and a conventional one is a too big transverse size of the fundamental mode of an open optical resonator. It claims a large gap in an undulator that dramatically decreases its strength. Both factors sorely decrease the amplification and the efficiency, and often make lasing impossible. The main way to solve this problem is to use a waveguide optical resonator. It decreases and controls the transverse size of the fundamental mode. However, the waveguide causes a number of problems: power absorption in its walls; higher modes generation by inhomogeneities, as it is not ideal; electron beam injection into a FEL is more sophisticated; also outcoupling is more complicated; finally, the resonator detuning control claims some special solutions. The waveguide dispersion relation differs from one in the free space. It shifts up the wavelength of the FEL, changes the optimal detuning, and creates a parasitic mode near the critical wavelength of the waveguide. These problems and possible solutions to them are considered.
	Slides WEB02 [20.394 MB]
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WEB03	Progress Towards an X-ray FEL Oscillator
	K.-J. Kim, T. Kolodziej, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin ANL, Argonne, Ilinois, USA J. Arthur, Y. Ding, W.M. Fawley, J.C. Frisch, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell SLAC, Menlo Park, California, USA
	Funding: Work at ANL supported under US Department of Energy contract DE-AC02-76SF00515 and at SLAC by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357 Issues and progress in R&D toward realizing an X-ray FEL oscillator will be discussed, including electron injector optimization, X-ray power density evolution on Bragg crystals throughout the lasing process, experimental efforts for testing radiation damage, evaluating the performance of compound refractive lenses (CRLs) as the focusing elements, and the basic considerations for mechanical layout. These will be discussed in the context of a concrete implementation scheme [] using the 4 GeV superconducting linac to be constructed at the LCLS-II. Time-dependent simulations of harmonic XFELO performance is discussed in another contribution to this conference by Zemella, et al. [] T. J. Maxwell et al., Feasibility study for an X-ray free electron laser oscillator, IPAC 2015, Richmond, Virginia, USA
	Slides WEB03 [6.452 MB]
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WEB04	Saturation Dynamics, Fine Spectrum, and Chirp Control in a CW FEL Oscillator	580
	H. S. Marks, A. Gover, H. Kleinman University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel D. Borodin, A. Damti, A. Friedman, Y. Vashdi Ariel University, Ariel, Israel M. Einat, M. Kanter, Y. Lasser, Yu. Lurie, A. Yahalom Ariel University Center of Samaria, Faculty of Engineering, Ariel, Israel
	As in conventional laser physics, the saturation dynamics of a long-pulse Electrostatic Accelerator FEL (EA-FEL) oscillator consists of oscillations build-up, resonator modes competition, and establishment of narrow linewidth single mode lasing. In EA-FEL the gain curve drifts to lower frequencies during the long laser pulse due to inevitable droop in the acceleration voltage. This post-saturation drift renders fine chirp of the single mode laser frequency due to the oscillator frequency pulling effect. We have integrated a voltage-ramping element into the electrostatic accelerator terminal that makes it possible to control the acceleration voltage throughout the lasing pulse. This allows us to keep the voltage constant throughout the e-beam pulse, and so increase the single mode lasing time, avoiding mode-hopping during the pulse due to the drift of the gain curve. Furthermore, by adjusting the voltage ramp rate and polarity we obtained controllable positive/negative laser frequency chirp that can be used in a single pulse sweep for fine spectral line (10^-6) gas-spectroscopy. The study was conducted on the Israeli EA-FEL that operates at tunable frequencies between 95-110 GHz.
	Slides WEB04 [2.310 MB]
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