Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Plenarvortrag Fr., 13:35–14:00 F-PV8
Current research at FLASH
Josef Feldhaus 1
1 DESY, Notkestraße 85, D-22607 Hamburg
The free-electron laser at DESY in Hamburg (FLASH) is the first free-electron laser
(FEL) built for the vacuum-ultraviolet (VUV) and soft X-ray region. In the present
configuration the FEL can be tuned to any wavelength between approximately 50 nm
and 13 nm by changing the electron beam energy from approximately 350 MeV to
700 MeV. The FEL has been operated at various wavelengths, the radiation pulses
were characterised in terms of pulse energy, spectral distribution and coherence, and
they have been used for a variety of experiments. Saturated intensities in the 10 -
100 µJ range have been reached with pulse durations of 10 - 50 fs. At these intensities
strong second and third harmonic radiation with some 0.5 % of the main peak has been
observed.
FLASH has started regular user operation in summer 2005. Currently 16 science
projects involving approximately 200 scientists from 11 countries are sharing 20 weeks
of beamtime per year. The remaining time is used for work on the accelerator to improve
and extend the operation of the FEL. In order to make efficient use of the FEL
beam, it can be switched between four experimental stations by movable mirrors. A
synchronised optical laser system is available for pump-probe experiments. Diagnostics
has been implemented to monitor the pulse energy and its timing with respect to the
optical laser. The science projects focus currently on four different areas:
(i) interaction of the ultra-intense FEL pulses with matter, including multiphoton excitation
of atoms, molecules and clusters, creation and characterisaton of dense plasmas,
and imaging of small objects;
(ii) femtosecond time-resolved experiments;
(iii) investigation of extremely dilute samples such as mass selected clusters and highly
charged ions;
(iv) investigation of solids and surfaces.
The current status of the facility is reviewed and examples of first user experiments
are presented.