FEL2011 - Table of Session: TUOC (FEL Technology I)

Paper

Title

Page

Latest Developments for Photoinjector, Seeding and THz Laser Systems

173

C.P. Hauri, A. Trisorio, C. Vicario
Paul Scherrer Institut, Villigen, Switzerland
C. Ruchert
PSI, Villigen PSI, Switzerland

For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.

Slides TUOCI1 [5.159 MB]

TUOCI2

High Frequency High Repetition Rate Linacs as Drivers for FEL

S.G. Tantawi
SLAC, Menlo Park, California, USA

The development of high gradient linacs necessitates the optimization of the structure efficiency. An effort on optimizing cavity shapes and RF sources results also in a very efficient system suitable for high repetition rate operation at moderate gradients. The overall system design becomes more efficient as one operates at higher frequencies. Naively, for a single bunch operation, one would expect that the average power required is inversely proportional to the square of the frequency. In this paper we will discuss the optimization and scaling of room temperature linacs as drivers for high repetition rate FELs. We will also discuss suitable electron gun designs and overall system considerations.

Slides TUOCI2 [3.677 MB]

TUOC3

High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb

179

H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan
LBNL, Berkeley, California, USA
I. Ben-Zvi
Stony Brook University, Stony Brook, USA
T. Rao, J. Smedley
BNL, Upton, Long Island, New York, USA

Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713.
We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required.
[1] Applied Physics Letters (submitted)

Slides TUOC3 [4.825 MB]

TUOC4

Design and First Experience with the FERMI Seed Laser

183

M.B. Danailov, P. Cinquegrana, A.A. Demidovich, R. Ivanov, I. Nikolov, P. Sigalotti
ELETTRA, Basovizza, Italy

Fermi@Elettra is the first fully seeding-based FEL. Laser operation was first demonstrated in December 2010 and later consistently studied during the runs in 2011. It is known that seeded operation puts heavy demands on the seed laser performance. This paper describes the design of the FERMI seed laser system, including the main laser as well as the most important subsystems and the issues that were solved to easily reach seeded operation. The main requirements to the seed were set by the use of High Gain Harmonic Generation FEL scheme and can be found in details in the FERMI CDR. Here we only recall that the seed needs to be broadly tunable in UV (down to 200 nm) with a peak power above 100 MW all over the tunability range. Obviously, such a tunability imposed the use of a parametric amplifier. For the first seeding comissioning, a fixed wavelength scheme was used, allowing much higher peak power. Here we present both solutions, showing the obtained performance and the limitations. The synchronization of the laser to the timing signals was of crucial importance for the successful seeded operation so the last part of the paper to the laser synchronization setup developed for FERMI.

Slides TUOC4 [1.360 MB]

Paper	Title	Page
TUOCI1	Latest Developments for Photoinjector, Seeding and THz Laser Systems	173
	C.P. Hauri, A. Trisorio, C. Vicario Paul Scherrer Institut, Villigen, Switzerland C. Ruchert PSI, Villigen PSI, Switzerland
	For driving compact FEL facilities cutting edge laser technology is required. We present the latest laser developments and concepts for ultrastable and versatile electron gun lasers, seed lasers and high-power laser-based THz sources taking place at the Paul Scherrer Institute and at other Free Electron Laser facilities. Such developments are of fundamental interest for next generation FEL pump-probe experiments requiring a temporal resolution beyond state of the art.
	Slides TUOCI1 [5.159 MB]

TUOCI2	High Frequency High Repetition Rate Linacs as Drivers for FEL
	S.G. Tantawi SLAC, Menlo Park, California, USA
	The development of high gradient linacs necessitates the optimization of the structure efficiency. An effort on optimizing cavity shapes and RF sources results also in a very efficient system suitable for high repetition rate operation at moderate gradients. The overall system design becomes more efficient as one operates at higher frequencies. Naively, for a single bunch operation, one would expect that the average power required is inversely proportional to the square of the frequency. In this paper we will discuss the optimization and scaling of room temperature linacs as drivers for high repetition rate FELs. We will also discuss suitable electron gun designs and overall system considerations.
	Slides TUOCI2 [3.677 MB]

TUOC3	High QE, Low Emittance, Green Sensitive FEL Photocathodes Using K₂CsSb	179
	H.A. Padmore, D. Dowell, J. Feng, T. Vecchione, W. Wan LBNL, Berkeley, California, USA I. Ben-Zvi Stony Brook University, Stony Brook, USA T. Rao, J. Smedley BNL, Upton, Long Island, New York, USA
	Funding: Work was supported by the Director, Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, KC0407-ALSJNT-I0013, and DE-SC0005713. We describe the development of photocathodes based on Potassium-Cesium-Antimonide that satisfy many of the key requirements of future light sources, such as robustness, high quantum efficiency when excited with visible light and low transverse emittance. We have demonstrated QE of 7% at 532 nm, a normalized transverse emittance of 0.36 μm at 543 nm and 3 MV/m field gradient[1]. We have also shown that the material can be relatively robust to residual water contamination and we have extracted current densities of 1 mA/mm² with very long lifetime. We believe that this work is an important step forward in FEL development where high repetition rate is required. [1] Applied Physics Letters (submitted)
	Slides TUOC3 [4.825 MB]

TUOC4	Design and First Experience with the FERMI Seed Laser	183
	M.B. Danailov, P. Cinquegrana, A.A. Demidovich, R. Ivanov, I. Nikolov, P. Sigalotti ELETTRA, Basovizza, Italy
	Fermi@Elettra is the first fully seeding-based FEL. Laser operation was first demonstrated in December 2010 and later consistently studied during the runs in 2011. It is known that seeded operation puts heavy demands on the seed laser performance. This paper describes the design of the FERMI seed laser system, including the main laser as well as the most important subsystems and the issues that were solved to easily reach seeded operation. The main requirements to the seed were set by the use of High Gain Harmonic Generation FEL scheme and can be found in details in the FERMI CDR. Here we only recall that the seed needs to be broadly tunable in UV (down to 200 nm) with a peak power above 100 MW all over the tunability range. Obviously, such a tunability imposed the use of a parametric amplifier. For the first seeding comissioning, a fixed wavelength scheme was used, allowing much higher peak power. Here we present both solutions, showing the obtained performance and the limitations. The synchronization of the laser to the timing signals was of crucial importance for the successful seeded operation so the last part of the paper to the laser synchronization setup developed for FERMI.
	Slides TUOC4 [1.360 MB]