The free electron laser FEL operates to generate coherent EUV radiation, receive an upstream electron beam EB2, and emit a downstream electron beam EB4, and upstream electron beams EB1, EB2 including electron bunches. And at least one possible electron source 21a, 21b. The beam path is configured to direct an upstream electron beam through a linear accelerator system (LINAC) including at least first and second linear accelerators 22a, 22b, a bunch compressor 28b, and the undulator 24. The downstream electron beams EB3, EB4 leaving the undulator 24 are recirculated through the second linear accelerator 22b in parallel with the upstream electron beam by a phase such that the downstream beam is decelerated by the second linear accelerator 22b. The downstream beam is then recirculated through the first linear accelerator 22a in parallel with the upstream electron beam with a phase such that the downstream beam is decelerated by the first linear accelerator 22a, and the downstream beam is directed to the beam dump 100. Is done. At least one first energy spreader 50a, 50b, 50c imparts a reversible change in the energy distribution of the electron bunch and is in a position in the beam path in front of the bunch compressor 28b so that it is only passed by the upstream electron beam EB1. To position. The second energy spreader 50d reverses the change to the energy distribution of the electron bunches imparted by the first energy spreaders 50a, 50b, 50c and is placed in front of the undulator 24 so that it is only passed by the upstream electron beam EB2. Located at a position in the beam path. [Selection] Figure 3
展开▼
