A vertical Au-coated silicon mirror (80 cm x 10 cm) is used for deflecting, in the horizontal plane and at a grazing angle of about 2.2 degrees, half of the synchrotron radiation photon beam produced by the same wiggler of the soft x-ray beamline, into the UV DXR2 branch line. After a sapphire window and some optics in air, a reflection grating monochromator (Jobin-Yvon) selects the photons in the spectral range between 2 and 6 eV by a bandwidth better than 0.3 %.
With this configuration this branch line has been used up to now for single experiments.
Between 2003 and 2004 it was dedicated to the Solar Ultraviolet Experiment (SUE),involving systematic investigations on the biological effects induced by the B band of the UV (280–320 nm) radiation on cultures of human cells and on their progenies. This experiment has had a large impact on evaluating the incidence of skin cancer in humans due to an increase of UVB radiation reaching the earth surface after the stratospheric ozone layer reduction.
In 2005 the UV branch line was dedicated to the experimental proposal named SOURCE (Synchrotron Optical Ultraviolet Radiation for Calibration Experiments). The main objective of the SOURCE experiment was setting up an apparatus addressing the simulation of UV tracks in the atmosphere, induced by Ultra High Energy Cosmic Rays (UHECR). This experiment was motivated by the large experiments already existing as AUGER and mainly by the future space experiments. The UV tracks can be obtained using a specific apparatus producing these transient phenomena starting from the UV synchrotron radiation (SR) available at the DXR2 branch line.
In 2007 it was decided to let the DXR2 branch line become a general purpose facility since the UV synchrotron radiation can be used for several applications in physics, astronomy, astro-particle, biology, and geology as well as in the medical and technological fields. In any case the calibration and characterization measurements for space experiments will still remain one of the top priorities of the DXR2 facility.