FEL2014 - List of Authors (Khan, S.)

Paper

Title

Page

Demonstration of SASE Suppression Through a Seeded Microbunching Instability

177

C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, E. Hass, K. Honkavaara, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov
DESY, Hamburg, Germany
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school 1355.
Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.

MOP084

Enhancing Coherent Harmonic Generation using Tilted Laser Wavefronts

248

S. Khan
DELTA, Dortmund, Germany

Funding: Work supported by BMBF (contract 05K13PE3)
Coherent Harmonic Generation (CHG) to produce ultrashort pulses of synchrotron radiation is based on the interaction of relativistic electrons in a storage ring with femtosecond laser pulses in an undulator. The resulting periodic energy modulation can be converted to a density modulation by a dispersive chicane, giving rise to coherent emission at harmonics of the laser wavelength in a second undulator. If the first undulator is in a section with non-zero dispersion, the density modulation can be enhanced using tilted laser wavefronts, thus delaying the phase-space distributions of electrons with different energy with respect to each other. The most simple way to realize the wavefront tilt would be to introduce a small crossing angle between the electron and laser beam. Details are discussed for the case of the CHG short-pulse facility at DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, but HGHG and EEHG seeding of free-electron lasers could also be performed this way.

MOP087

Upgrade Plans for the Short-pulse Facility at DELTA

255

S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
DELTA is a 1.5-GeV synchrotron light source operated by the TU Dortmund University with a short-pulse facility based on Coherent Harmonic Generation (CHG) * to produce radiation with wavelengths in the VUV regime. Even shorter wavelengths can be generated by an upgrade based on the Echo-Enabled Harmonic Generation (EEHG) technique ** which requires additional magnetic chicanes and undulators. A new storage ring lattice provides enough free space for an EEHG setup and additionally for a femtoslicing undulator. Besides the new optics, first simulation results of EEHG will be presented.
* S. Khan et al., Sync. Rad. News 26, 3 (2013).
** G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).

MOP089

Overview of FEL Seeding Activities at FLASH

J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Mueller, T. Tanikawa
DESY, Hamburg, Germany
S. Ackermann, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach
Uni HH, Hamburg, Germany
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany

The free-electron laser facility FLASH at DESY operates since several years in SASE mode, delivering high-intensity FEL pulses in the extreme ultra violet and soft x-ray wavelength range for users. In order to get more control of the characteristics of the FEL pulses external FEL seeding has proven to be a reliable method to do so. At FLASH, an experimental setup to test several different external seeding methods has been installed since 2010. After successful demonstration of direct seeding at 38 nm, the setup is now being commissioned to operate in HGHG and EEHG mode. Furthermore, other studies on laser induced effects on the electron beam dynamics will be performed. Beside the experimental activities, a design for the seeding option for the FLASH2 beamline is currently under investigation. The goal for that is to develop a concept which is compatible with the operation of FLASH1 and which satisfies the high demands of the future user community. In this contribution, we give an overview of the activities on FEL seeding at FLASH.

TUP082

Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation

556

A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk
DELTA, Dortmund, Germany

Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW.
At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

THP076

Measurements of the Timing Stability at the FLASH1 Seeding Experiment

913

C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland
Uni HH, Hamburg, Germany
S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz
DESY, Hamburg, Germany
G. Angelova Hamberg
Uppsala University, Uppsala, Sweden
K.E. Hacker, S. Khan, R. Molo
DELTA, Dortmund, Germany
P.M. Salen, P. van der Meulen
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden

Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355.
For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.

Paper	Title	Page
MOP060	Demonstration of SASE Suppression Through a Seeded Microbunching Instability	177
	C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach Uni HH, Hamburg, Germany S. Ackermann, J. Bödewadt, G. Brenner, M. Dohlus, N. Ekanayake, T. Golz, E. Hass, K. Honkavaara, T. Laarmann, T. Limberg, E. Schneidmiller, N. Stojanovic, M.V. Yurkov DESY, Hamburg, Germany K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4, and 05K13PE3 and the German Research Foundation programme graduate school 1355. Collective effects and instabilities due to longitudinal space charge and coherent synchrotron radiation can degrade the quality of the ultra-relativistic, high-brilliance electron bunches needed for the operation of free-electron lasers. In this contribution, we demonstrate the application of a laser-induced microbunching instability to selectively suppress the SASE process. A significant decrease of photon pulse energies was observed at the free-electron laser FLASH in coincidence with overlap of 800 nm laser pulses and electron bunches within a modulator located approximately 40 meters upstream of the undulators. We discuss the underlying mechanisms based on longitudinal space charge amplification [E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 110701 (2010)] and present measurements.

MOP084	Enhancing Coherent Harmonic Generation using Tilted Laser Wavefronts	248
	S. Khan DELTA, Dortmund, Germany
	Funding: Work supported by BMBF (contract 05K13PE3) Coherent Harmonic Generation (CHG) to produce ultrashort pulses of synchrotron radiation is based on the interaction of relativistic electrons in a storage ring with femtosecond laser pulses in an undulator. The resulting periodic energy modulation can be converted to a density modulation by a dispersive chicane, giving rise to coherent emission at harmonics of the laser wavelength in a second undulator. If the first undulator is in a section with non-zero dispersion, the density modulation can be enhanced using tilted laser wavefronts, thus delaying the phase-space distributions of electrons with different energy with respect to each other. The most simple way to realize the wavefront tilt would be to introduce a small crossing angle between the electron and laser beam. Details are discussed for the case of the CHG short-pulse facility at DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, but HGHG and EEHG seeding of free-electron lasers could also be performed this way.

MOP087	Upgrade Plans for the Short-pulse Facility at DELTA	255
	S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, A. Meyer auf der Heide, R. Molo, H. Rast, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW. DELTA is a 1.5-GeV synchrotron light source operated by the TU Dortmund University with a short-pulse facility based on Coherent Harmonic Generation (CHG) * to produce radiation with wavelengths in the VUV regime. Even shorter wavelengths can be generated by an upgrade based on the Echo-Enabled Harmonic Generation (EEHG) technique ** which requires additional magnetic chicanes and undulators. A new storage ring lattice provides enough free space for an EEHG setup and additionally for a femtoslicing undulator. Besides the new optics, first simulation results of EEHG will be presented. * S. Khan et al., Sync. Rad. News 26, 3 (2013). ** G. Stupakov, Phys. Rev. Lett. 102, 074801 (2009).

MOP089	Overview of FEL Seeding Activities at FLASH
	J. Bödewadt, S. Ackermann, R.W. Aßmann, N. Ekanayake, B. Faatz, G. Feng, I. Hartl, R. Ivanov, T. Laarmann, J.M. Mueller, T. Tanikawa DESY, Hamburg, Germany S. Ackermann, A. Azima, M. Drescher, L.L. Lazzarino, C. Lechner, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Roßbach Uni HH, Hamburg, Germany K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany
	The free-electron laser facility FLASH at DESY operates since several years in SASE mode, delivering high-intensity FEL pulses in the extreme ultra violet and soft x-ray wavelength range for users. In order to get more control of the characteristics of the FEL pulses external FEL seeding has proven to be a reliable method to do so. At FLASH, an experimental setup to test several different external seeding methods has been installed since 2010. After successful demonstration of direct seeding at 38 nm, the setup is now being commissioned to operate in HGHG and EEHG mode. Furthermore, other studies on laser induced effects on the electron beam dynamics will be performed. Beside the experimental activities, a design for the seeding option for the FLASH2 beamline is currently under investigation. The goal for that is to develop a concept which is compatible with the operation of FLASH1 and which satisfies the high demands of the future user community. In this contribution, we give an overview of the activities on FEL seeding at FLASH.

TUP082	Coherent Harmonic Generation at the DELTA Storage Ring: Towards User Operation	556
	A. Meyer auf der Heide, S. Hilbrich, H. Huck, M. Huck, M. Höner, S. Khan, C. Mai, R. Molo, H. Rast, A. Schick, P. Ungelenk DELTA, Dortmund, Germany
	Funding: Work supported by DFG, BMBF, FZ Jülich, and by the Land NRW. At DELTA, a 1.5-GeV synchrotron light source at the TU Dortmund University, a short-pulse facility based on Coherent Harmonic Generation (CHG) is in operation and shall soon be used for pump-probe experiments. Due to the interaction of ultrashort laser pulses with electron bunches in an undulator, CHG provides short and coherent pulses at harmonics of the laser wavelength. In this paper, recent progress towards user operation, pulse characterization studies such as transverse and longitudinal coherence measurements as well as CHG in the presence of an RF phase modulation are presented.

THP076	Measurements of the Timing Stability at the FLASH1 Seeding Experiment	913
	C. Lechner, A. Azima, M. Drescher, L.L. Lazzarino, Th. Maltezopoulos, V. Miltchev, T. Plath, J. Rönsch-Schulenburg, J. Roßbach, M. Wieland Uni HH, Hamburg, Germany S. Ackermann, J. Bödewadt, H. Dachraoui, N. Ekanayake, B. Faatz, M. Felber, K. Honkavaara, T. Laarmann, J.M. Mueller, H. Schlarb, S. Schreiber, S. Schulz DESY, Hamburg, Germany G. Angelova Hamberg Uppsala University, Uppsala, Sweden K.E. Hacker, S. Khan, R. Molo DELTA, Dortmund, Germany P.M. Salen, P. van der Meulen FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
	Funding: Supported by Federal Ministry of Education and Research of Germany under contract No. 05K10PE1, 05K10PE3, 05K13GU4 and 05K13PE3 and the German Research Foundation programme graduate school 1355. For seeding of a free-electron laser, the spatial and temporal overlap of the seed laser pulse and the electron bunch in the modulator is critical. To establish the temporal overlap, the time difference between pulses from the seed laser and spontaneous undulator radiation is reduced to a few pico-seconds with a combination of a photomultiplier tube and a streak camera. Finally, for the precise overlap the impact of the seed laser pulses on the electron bunches is observed. In this contribution, we describe the current experimental setup, discuss the techniques applied to establish the temporal overlap and analyze its stability.