Figure 1
From: Coherent THz Emission Enhanced by Coherent Synchrotron Radiation Wakefield
Top: sketch, not to scale, of the FERMI FEL1 beam delivery system. Only the first magnetic bunch length compressor (BC1) is routinely active for lasing. Start-to-end simulations of the electron beam dynamics were carried out, for diverse linac settings, from the Gun (G) through the linac sections (L0–L4) until the Main Beam Dump (MBD), where the Al target for CTR emission is installed. Bottom: 3-D rendering of the MBD, from the FEL post-undulator region to the dump. The active dipole magnets, named “Dipole 1” and “Dipole 2” in the figure, are long 1.12 m and 2.44 m, with bending angles of 15.7 deg and 31.4 deg respectively. Three quadrupoles between “Dipole 1” and “Dipole 2” tune the momentum compaction (R56) of the beam line. CTR is emitted at the 1 µm-thick Al target. Four quadrupoles installed upstream of the first dipole control the beam envelope along the line without affecting the R56 value. The transverse RMS beam sizes at the CTR target are kept smaller than 0.5 mm. Steering magnets and beam position monitors (not shown) allow control of beam trajectory. While electrons are bent and eventually dumped, FEL propagates straight to the downstream experimental hall (EH).
