FLASH
FLASH upgrade will boost the beam energy to 1.2 GeV
Since 21-Sep-2009 the ambitious FLASH upgrade has been started.
The main goal is to increase the beam energy from 1 to 1.2 GeV by adding a new XFEL type accelerating module and to use so called 3rd harmonic cavities to linearize the longitudinal phase space of the electron beam.
Many other improvements are schedules, like the replacement of 3 outdated modulators
with modern types, the installation of a new rf gun and a new accelerating module in the injector.
FLASH will house the seeding experiment sFLASH. An external laser will overlap with the electron beam to seed the SASE process in special undulators installed between the accelerator and the FLASH undulators.
First beam with the upgraded facility is expected in spring 2010.
 "Zoom (20KB)")
FLASH, DESY's free-electron laser is a world-wide unique facility delivering intense ultra-short femtosecond coherent radiation in the wavelength range between 47 and 6.8 nm.
With a successful upgrade, wavelengths below 5 nm are expected. Since 2005, FLASH is a user facility serving a large variety of experiments.
Typical user operation parameters during the 2nd user period from Nov 26, 2007 to Aug 16, 2009:
Wavelength range (fundamental) 6.8 – 47 nm
Average single pulse energy 10 – 100 µJ
Pulse duration (FWHM) 10 – 70 fs
Peak power (from av.) 1 – 5 GW
Average power (example for 500 pulses/sec) ~ 15 mW
Spectral width (FWHM) ~ 1 %
Peak Brilliance 10^29 - 10^30 photons/s/mrad2/mm2/0.1%bw
Many scientific disciplines ranging from physics, chemistry and biology to material sciences, geophysics and medical diagnostics use
the powerful soft X-ray source FLASH.
The ultra-short X-ray pulses in the femtosecond range allow experiments which are not possible otherwise. For example, time-resolved observation of chemical reactions with atomic resolution, single shot diffraction imaging, and many others.
More than 60 publications on photon science have been published already, many in high ranked journals.
FLASH is a high-gain free-electron laser (FEL) which achieves laser amplification and saturation within a single pass of the electron
bunch through an undulator and does not require a set of mirrors which is needed in conventional lasers.
The lasing process is initiated by the spontaneous undulator radiation, and the FEL works then in the so-called Self-Amplified Spontaneous Emission (SASE) mode without needing an external input signal.The electron bunches are produced in a laser-driven photoinjector and accelerated by a superconducting linear accelerator. The RF-gun based photoinjector allows the generation of electron bunches with tiny emittances - mandatory for an efficient SASE process.The superconducting techniques allows to accelerate thousands of bunches per second, which is not possible with other technologies.
At intermediate energies of 130 and 470 MeV the electron bunches are longitudinally compressed, thereby increasing the peak current from
initially 50-80 A to 1-2 kA - as required for the lasing process in the undulator. The 30 m long undulator consists of permanent NdFeB magnets
with a fixed gap of 12 mm, a period length of 27.3 mm and peak magnetic field of 0.47 T. The electrons interact with the undulator field
in such a way, that so called micro bunches are developed. These micro bunches radiate coherently and produce intense X-ray pulses.
Finally, a dipole magnet deflects the electron beam safely into a dump, while the FEL radiation propagates to the experimental hall.
Picture gallery of the FLASH linac
updated in May 2008
