MOP006
DESY, Hamburg, Germany
HZDR, Dresden, Germany
BINP SB RAS, Novosibirsk, Russia
Linear accelerator based light sources with their tunable broad spectral range (THz to hard X-rays regime) and their ability to generate ultra-short pulses with peak intensities many orders of magnitude higher then synchrotron sources, gave rise to a new field of ultrafast physics. In the THz range, the ability of 4th gen. light sources to generate pulses with e-field strengths up to 1 GV/m opened the door to the field of non-linear THz spectroscopy and THz-controlled material science. The main advantage of accelerator-based THz is its scaleability. As the process is not bound to a particular medium, but occurs in the accelerator vacuum, it bypasses the limitation of table top sources. In addition, it has been demonstrated that coherent THz radiation can be generated along femtosecond X-ray pulses in 4th Generation X-ray Light sources such as FLASH [1,2,3] and LCLS [4]. This opens up the opportunity for naturally synchronized THz pump X-ray probe experiments on a few femtosecond time scale [1,2,4]. Here we present the design for the THz source at FLASH2, which takes new findings [5] and challenges into account that we face during the radiation transport to the experimental hall.
Uni HH, Hamburg, Germany
DESY, Hamburg, Germany
DELTA, Dortmund, Germany
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.
Uni HH, Hamburg, Germany
DESY, Hamburg, Germany
This paper describes the experimental activity on the generation of very short FEL pulses in the soft x-ray range in the SASE-mode at the high-gain free-electron laser FLASH [1, 2]. The key element, a photo-injector laser which is able to generate laser pulses of about 2 ps FWHM has been optimized and commissioned. It allows the generation of shorter bunches with low bunch charge (of up to 200 pC) directly at the photo-cathode. Initially shorter injector laser pulses and thus shorter bunches eases the required bunch compression factor for short pulses below 10 fs duration which makes operation of the electron beam formation system to be more robust with respect to jitters and collective effects. As a result, overall stability of SASE FEL performance is improved. In the optimal case single-spike operation can be achieved. In this paper the experimental results on production of short electron bunches and the SASE performance using the new injector laser will be shown and the measured electron bunch and FEL radiation properties are discussed. In addition, optimizations of bunch diagnostics for low charge and short bunches are discussed.
THA04
DESY, Hamburg, Germany
CFEL, Hamburg, Germany
HZDR, Dresden, Germany
HIJ, Jena, Germany
We employ so- called Optical Afterburner [*,**] principle to generate optical replica pulses of X-ray pulse at FLASH (Free Electron LASer in Hamburg). These pulses are naturally synchronized to the FEL pulses and share the same envelope and arrival time, with accuracy down to few femtoseconds. Because of this, Optical Afterburner pulses can be used for complete temporal diagnostics for FEL pulses. Because we shift diagnostics challenge from X-ray to visible range, this significantly simplifies detection. During pulse- duration measurement campaigns at FLASH, Optical Afterburner has been demonstrated as versatile and accurate tool to measure pulse duration of X-ray FEL pulses. In the most recent development we have amplified, Optical Afterburner pulses by three orders of magnitude and will used it in the X-ray/Visible pump-probe experiments for ultimate temporal resolution. We have demonstrated amplification concept at FLASH, where we reach pulse energies above 1uJ at 1MHz repetition rate.
References:
* E.L. Saldin, E.A. Schneidmiller and M.V. Yurkov, Phys. Rev. ST Accel. Beams 13, 030701 (2010)
* Proceedings of IPAC2011, San Sebastián, Spain. THPC084
THP065
HZDR, Dresden, Germany
SLAC, Menlo Park, California, USA
DESY, Hamburg, Germany
TU Dresden, Dresden, Germany
