FEL2011 - Table of Session: WEOC (FEL Experiments I)

Paper

Title

Page

Beam Line Commissioning of a UV/VUV FEL at Jefferson Lab

326

S.V. Benson, G.H. Biallas, K. Blackburn, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, G.P. Williams, F.G. Wilson, S. Zhang
JLAB, Newport News, Virginia, USA
C. Clavero
The College of William and Mary, Williamsburg, USA

Funding: Work supported by U.S. DOE Contract DE-AC05-84-ER40150, Air Force Office of Scientific Research, DOE Basic Energy Sciences, Office of Naval Research, and the Joint Technology Office.
Many novel applications in photon sciences require very high source brightness and/or short pulses in the vacuum ultra-violet (VUV). Jefferson Lab has commissioned a UV oscillator with high gain and has transported the third harmonic of the UV to a user lab. The experimental performance of the UV FEL is much better than simulated performance in both gain and efficiency. This success is important for efforts to push towards higher gain FELs at short wavelengths where mirrors absorb strongly. We will report on efforts to characterize the UV laser and the VUV coherent harmonics as well as designs to lase directly in the VUV wavelength range.

Slides WEOCI1 [3.331 MB]

WEOCI2

Ultrashort Single Spike Pulse Generation at the SPARC Test Facility

D. Filippetto
LBNL, Berkeley, California, USA
A. Bacci, M. Bellaveglia, M. Castellano, E. Chiadroni, L. Cultrera, G. Di Pirro, M. Ferrario, L. Ficcadenti, A. Gallo, G. Gatti, E. Pace, B. Spataro, C. Vaccarezza, C. Vicario
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
F. Ciocci, G. Dattoli, M. Del Franco, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I.P. Spassovsky, V. Surrenti
ENEA C.R. Frascati, Frascati (Roma), Italy
F. Frassetto, L. P. Poletto
LUXOR, Padova, Italy
M. Moreno, M. Serluca
INFN-Roma, Roma, Italy
A. Mostacci
Rome University La Sapienza, Roma, Italy
V. Petrillo, A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
J.V. Rau, V. Rossi Albertini
ISM-CNR, Rome, Italy

We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a Self Amplified Spontaneous Emission mode Free Electron Laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. Longitudinal phase space rotation via velocity bunching is used to generate the energy chirp, which also increases the peak current and the FEL performances. An increase of more than one order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.

Slides WEOCI2 [16.008 MB]

WEOC3

Experimental Study of FEL Power Scaling in the Storage Ring FEL

Y.K. Wu, B. Jia, J.Y. Li, S.F. Mikhailov, V. Popov, W. Wu
FEL/Duke University, Durham, North Carolina, USA
S. Huang
PKU/IHIP, Beijing, People's Republic of China

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
It is well known that the optical power of a storage ring FEL (SRFEL) is limited by the FEL induced e-beam energy spread (the Renieri's limit). This power limit can be derived using a 1D model under certain assumptions. However, systematic, experimental studies of SRFEL power as a function of operation parameters are lacking. In fact, it is difficulty to directly measure the e-beam energy spread over a wide range. In this work, we report our work on measuring e-beam energy spread in a wide range using optical klystron radiation [1]. A novel numerical method has been developed to treat spectral broadening and modulation on an equal footing. Using this new technique, we have conducted a systematic study of the SRFEL power as a function of various parameters. Our results show for the first time that for in a wide range of operation conditions, the storage ring FEL power only directly depends on the induced electron beam energy spread. Means of tuning of the FEL power, including changing the synchronization between electron and FEL beams, RF voltage, FEL cavity loss, etc, are possible though a change of the induced energy spread.
[1] Phys. Rev. STAB, 13, 080702 (2010)

Slides WEOC3 [1.158 MB]

WEOC4

Intense Coherent THz Synchrotron Radiation Induced by a Storage Ring FEL Seeded with a Femtosecond Laser

M. Hosaka, Y. Taira, Y. Takashima, N. Yamamoto
Nagoya University, Nagoya, Japan
M. Adachi, M. Katoh, T. Tanikawa, H. Zen
UVSOR, Okazaki, Japan
S. Bielawski, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
C. Evain
SOLEIL, Gif-sur-Yvette, France

Very recently, we have succeeded in seeding a resonator FEL by injecting an external femtosecond laser at the UVSOR-II storage ring [1]. Intense coherent synchrotron radiation (CSR) in the THz region from a bending magnet was observed when the seeded FEL was operated in the pulsed Q-switch mode [2]. We have also found that the CSR intensity depends on the pulse duration of the seed laser. The CSR intensity is enhanced with short pulse ~200 fsec and suppressed with longer pulse ~200 psec. Simultaneous measurement of the terahertz radiation and the FEL pulse reveals that the radiation is emitted in the growing phase of the Q-switch FEL pulse. We think that the CSR comes from repetitive interactions between the laser pulse and the electron bunch as the short pulse laser growth in the optical cavity. In the presentation, we will also discuss the production mechanism of the CSR.
[1] C. Szwaj et al., FEL2011, TUPB05, in this conference.
[2] H. Zen et al., FEL2011, TUPA13, in this conference.

Slides WEOC4 [2.715 MB]

Paper	Title	Page
WEOCI1	Beam Line Commissioning of a UV/VUV FEL at Jefferson Lab	326
	S.V. Benson, G.H. Biallas, K. Blackburn, D.B. Bullard, J.L. Coleman, C. Dickover, D. Douglas, F.K. Ellingsworth, P. Evtushenko, C.W. Gould, J.G. Gubeli, D. Hardy, C. Hernandez-Garcia, K. Jordan, J.M. Klopf, J. Kortze, R.A. Legg, M. Marchlik, S.W. Moore, G. Neil, T. Powers, D.W. Sexton, M.D. Shinn, C. Tennant, R.L. Walker, G.P. Williams, F.G. Wilson, S. Zhang JLAB, Newport News, Virginia, USA C. Clavero The College of William and Mary, Williamsburg, USA
	Funding: Work supported by U.S. DOE Contract DE-AC05-84-ER40150, Air Force Office of Scientific Research, DOE Basic Energy Sciences, Office of Naval Research, and the Joint Technology Office. Many novel applications in photon sciences require very high source brightness and/or short pulses in the vacuum ultra-violet (VUV). Jefferson Lab has commissioned a UV oscillator with high gain and has transported the third harmonic of the UV to a user lab. The experimental performance of the UV FEL is much better than simulated performance in both gain and efficiency. This success is important for efforts to push towards higher gain FELs at short wavelengths where mirrors absorb strongly. We will report on efforts to characterize the UV laser and the VUV coherent harmonics as well as designs to lase directly in the VUV wavelength range.
	Slides WEOCI1 [3.331 MB]

WEOCI2	Ultrashort Single Spike Pulse Generation at the SPARC Test Facility
	D. Filippetto LBNL, Berkeley, California, USA A. Bacci, M. Bellaveglia, M. Castellano, E. Chiadroni, L. Cultrera, G. Di Pirro, M. Ferrario, L. Ficcadenti, A. Gallo, G. Gatti, E. Pace, B. Spataro, C. Vaccarezza, C. Vicario INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy F. Ciocci, G. Dattoli, M. Del Franco, L. Giannessi, A. Petralia, M. Quattromini, C. Ronsivalle, E. Sabia, I.P. Spassovsky, V. Surrenti ENEA C.R. Frascati, Frascati (Roma), Italy F. Frassetto, L. P. Poletto LUXOR, Padova, Italy M. Moreno, M. Serluca INFN-Roma, Roma, Italy A. Mostacci Rome University La Sapienza, Roma, Italy V. Petrillo, A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy J.V. Rau, V. Rossi Albertini ISM-CNR, Rome, Italy
	We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a Self Amplified Spontaneous Emission mode Free Electron Laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. Longitudinal phase space rotation via velocity bunching is used to generate the energy chirp, which also increases the peak current and the FEL performances. An increase of more than one order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.
	Slides WEOCI2 [16.008 MB]

WEOC3	Experimental Study of FEL Power Scaling in the Storage Ring FEL
	Y.K. Wu, B. Jia, J.Y. Li, S.F. Mikhailov, V. Popov, W. Wu FEL/Duke University, Durham, North Carolina, USA S. Huang PKU/IHIP, Beijing, People's Republic of China
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. It is well known that the optical power of a storage ring FEL (SRFEL) is limited by the FEL induced e-beam energy spread (the Renieri's limit). This power limit can be derived using a 1D model under certain assumptions. However, systematic, experimental studies of SRFEL power as a function of operation parameters are lacking. In fact, it is difficulty to directly measure the e-beam energy spread over a wide range. In this work, we report our work on measuring e-beam energy spread in a wide range using optical klystron radiation [1]. A novel numerical method has been developed to treat spectral broadening and modulation on an equal footing. Using this new technique, we have conducted a systematic study of the SRFEL power as a function of various parameters. Our results show for the first time that for in a wide range of operation conditions, the storage ring FEL power only directly depends on the induced electron beam energy spread. Means of tuning of the FEL power, including changing the synchronization between electron and FEL beams, RF voltage, FEL cavity loss, etc, are possible though a change of the induced energy spread. [1] Phys. Rev. STAB, 13, 080702 (2010)
	Slides WEOC3 [1.158 MB]

WEOC4	Intense Coherent THz Synchrotron Radiation Induced by a Storage Ring FEL Seeded with a Femtosecond Laser
	M. Hosaka, Y. Taira, Y. Takashima, N. Yamamoto Nagoya University, Nagoya, Japan M. Adachi, M. Katoh, T. Tanikawa, H. Zen UVSOR, Okazaki, Japan S. Bielawski, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France C. Evain SOLEIL, Gif-sur-Yvette, France
	Very recently, we have succeeded in seeding a resonator FEL by injecting an external femtosecond laser at the UVSOR-II storage ring [1]. Intense coherent synchrotron radiation (CSR) in the THz region from a bending magnet was observed when the seeded FEL was operated in the pulsed Q-switch mode [2]. We have also found that the CSR intensity depends on the pulse duration of the seed laser. The CSR intensity is enhanced with short pulse ~200 fsec and suppressed with longer pulse ~200 psec. Simultaneous measurement of the terahertz radiation and the FEL pulse reveals that the radiation is emitted in the growing phase of the Q-switch FEL pulse. We think that the CSR comes from repetitive interactions between the laser pulse and the electron bunch as the short pulse laser growth in the optical cavity. In the presentation, we will also discuss the production mechanism of the CSR. [1] C. Szwaj et al., FEL2011, TUPB05, in this conference. [2] H. Zen et al., FEL2011, TUPA13, in this conference.
	Slides WEOC4 [2.715 MB]