FEL2013 - List of Authors (Divall, M.C.)

Paper	Title	Page
MOPSO77	Timing Jitter Measurements of the SwissFEL Test Injector	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.

TUPSO86	Photocathode Laser Wavelength-tuning for Thermal Emittance and Quantum Efficiency Studies	434
	C. Vicario, S. Bettoni, B. Beutner, M.C. Divall, C.P. Hauri, E. Prat, T. Schietinger, A. Trisorio PSI, Villigen PSI, Switzerland
	SwissFEL compact design is based on extremely low emittance electron beam from an RF photoinjector. Proper temporal and spatial shaping of the photocathode drive laser is employed to reduce the space charge emittance contribution. However, the ultimate limit for the beam emittance is the thermal emittance, which depends on the excess energy of the emitted photoelectrons. By varying the photocathode laser wavelength it is possible to reduce the thermal emittance. For this purpose, we developed a tunable Ti:sapphire laser and an optical parametric amplifier which allow to scan the wavelength between 250 and 305 nm. The system permits to study the thermal emittance and the quantum efficiency evolution as function of the laser wavelength for the copper photocathode in the RF gun of the SwissFEL injector test facility. The results are presented and discussed.

TUPSO88	New Concept for the SwissFEL Gun Laser	442
	A. Trisorio, M.C. Divall, C.P. Hauri, C. Vicario PSI, Villigen PSI, Switzerland A. Courjaud Amplitude Systemes, Pessac, France
	The operation of Swiss FEL put very stringent constrains on the gun laser system. First the parameters, such as energy stability, timing jitter, double pulse operation, temporal and spatial pulse shape of the ultra-violet laser pulses used to generate the photo-electrons are challenging even for the state of the art laser technologies. Second, the laser system must be extremely stable, reliable and its maintenance cost as low as possible. In this perspective, we prospected for alternative technologies to the well known, commonly used but costly Ti:sapphire laser systems. We show that a hybrid Yb fiber and solid state Yb:CaF2 amplifier system can be a very interesting approach. This gain medium allows the production of sub-500 fs, high fidelity, high stability, high energy pulses in the ultra-violet with low timing jitter. The system profits of the mature, stable direct diode pumping technology and optimized design. It delivers the two high-energy, shaped UV pulses separated by 28 ns to produce the photo-electrons, a short IR probe (<100 fs FWHM) to temporally characterize those pulses and the two stretched IR pulses ( 50 ps FWHM) necessary for the laser heater.

Paper

Title

Page

Timing Jitter Measurements of the SwissFEL Test Injector

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.

TUPSO86

Photocathode Laser Wavelength-tuning for Thermal Emittance and Quantum Efficiency Studies

434

C. Vicario, S. Bettoni, B. Beutner, M.C. Divall, C.P. Hauri, E. Prat, T. Schietinger, A. Trisorio
PSI, Villigen PSI, Switzerland

SwissFEL compact design is based on extremely low emittance electron beam from an RF photoinjector. Proper temporal and spatial shaping of the photocathode drive laser is employed to reduce the space charge emittance contribution. However, the ultimate limit for the beam emittance is the thermal emittance, which depends on the excess energy of the emitted photoelectrons. By varying the photocathode laser wavelength it is possible to reduce the thermal emittance. For this purpose, we developed a tunable Ti:sapphire laser and an optical parametric amplifier which allow to scan the wavelength between 250 and 305 nm. The system permits to study the thermal emittance and the quantum efficiency evolution as function of the laser wavelength for the copper photocathode in the RF gun of the SwissFEL injector test facility. The results are presented and discussed.

TUPSO88

New Concept for the SwissFEL Gun Laser

442

A. Trisorio, M.C. Divall, C.P. Hauri, C. Vicario
PSI, Villigen PSI, Switzerland
A. Courjaud
Amplitude Systemes, Pessac, France

The operation of Swiss FEL put very stringent constrains on the gun laser system. First the parameters, such as energy stability, timing jitter, double pulse operation, temporal and spatial pulse shape of the ultra-violet laser pulses used to generate the photo-electrons are challenging even for the state of the art laser technologies. Second, the laser system must be extremely stable, reliable and its maintenance cost as low as possible. In this perspective, we prospected for alternative technologies to the well known, commonly used but costly Ti:sapphire laser systems. We show that a hybrid Yb fiber and solid state Yb:CaF2 amplifier system can be a very interesting approach. This gain medium allows the production of sub-500 fs, high fidelity, high stability, high energy pulses in the ultra-violet with low timing jitter. The system profits of the mature, stable direct diode pumping technology and optimized design. It delivers the two high-energy, shaped UV pulses separated by 28 ns to produce the photo-electrons, a short IR probe (<100 fs FWHM) to temporally characterize those pulses and the two stretched IR pulses ( 50 ps FWHM) necessary for the laser heater.