Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
FERMI is a users facility based on a seeded Free Electron Laser (FEL). A unique feature of FERMI in this new class of light sources is the tunability of the emitted photon beam both in terms of wavelength and polarization. Tuning is obtained by choosing the appropriate gap and phasing of the undulators in the chain and by opportunely setting the seed laser wavelength. A series of adjustments are then necessary in order to keep constant the machine parameters and optimize the radiation characteristics. We have developed a software application, named SuperGap, which does all the calculations and coordinates the operations required to set the desired wavelength and polarization. SuperGap allows operators to perform this procedure in seconds. The speed and accuracy of the wavelength change have been largely exploited during user dedicated shifts to perform various types of scans in the experimental stations. The paper describes the algorithms and numerical techniques used by SuperGap and its architecture based on the Tango control system.
