FERMI@ELETTRA bunch compressor chicane mechanical design

Abstract

The FERMI@ELETTRA Free-Electron-Laser (FEL) project at the ELETTRA Laboratory of Sincrotrone Trieste, currently under construction and commissioning, will comprise a linear accelerator and two FEL beamlines. Two identical magnetic chicanes for bunch length compression will be installed in the linear accelerator (LINAC) tunnel. The first bunch compressor, at 300 MeV, has been recently installed and commissioned while the production and installation plan of the second one (at 600 MeV) is being defined. The chicane mechanical design has been achieved in collaboration with the supplier, Rial Vacuum srl. In this paper, the chicane mechanical design and the movable vacuum chambers are presented. IntroductionThe FERMI machine consists of three main sections: the linear accelerator, the undulator hall and the experimental area. The accelerator, schematically shown in figure 1, comprises the gun, the laser heater, four accelerating sections groups (L1-L4), two bunch compressors (BC1 and BC2) and the spreader (Various Authors, 2007).The linear accelerator, except for the X-bend section and the BC2, is already installed and now under conditioning and commissioning.The BC1 purpose is to reduce the electron bunch length, thus increasing the peak current, taking advantage of the beam correlated energy spread. Due to the accelerating process, there is an inherent longitudinal energy spread in the electron bunch. The tail energy ratio (ΔE/E) is higher than the head one. Passing through four bending magnets chicane, the path length is energy dependent and the electron bunch is compressed. At each bend, the electron bunch head delays with respect to the tail.Mounting high homogeneity magnetic field dipoles and having diagnostic devices centred on the beam at each chicane position are the main advantages of the movable chicane.The nominal BC1 energy is in the range of 230-300 MeV.