Demonstration of a laser-driven prebuncher staged with a laser accelerator—the STELLA program.

During the Staged Electron Laser Acceleration (STELLA) program we demonstrated for the first time the staging together of laser accelerator modules. We also demonstrated the capture and acceleration of laser-generated microbunches, which are 1-2 µm in length and have < 2% energy spread. The modules consist of an inverse free electron laser (IFEL) prebuncher with an IFEL accelerator. The two IFELs use identical permanent-magnet wiggler arrays (wiggler period = 3.3 cm, wiggler length = 33 cm) and are separated by 2.3 m with a triplet located between them. The first IFEL is used to modulate the e-beam energy so that microbunches are formed at the entrance to the second IFEL. This second IFEL is designed to capture and accelerate the microbunches. These devices are driven by a CO[sub 2] laser beam, which has been split into two beams that are sent to the IFELs. A trombone delay line in the laser beam transport system is located before the second IFEL to allow phase delay adjustment between the microbunches entering the accelerator and the laser beam driving the second IFEL. Typical energy spectra of the staged IFELs as a function of this phase delay will be shown. The data agree well with model simulations. Reliable and reproducible control of the phase delay is demonstrated. [ABSTRACT FROM AUTHOR]