THP082 　ポスター②　 8月1日 3Fホワイエ 13:00-15:00

Beam dynamics studies of emittance reduction in the SACLA injector

○Vitaliy Goryashko (SPring-8, RIKEN), Anatoliy Opanasenko, Giovanni Perosa (Uppsala University), Kazuaki Togawa (SPring-8, RIKEN)

The SACLA X-ray Free-Electron-Laser (XFEL) is planned to be upgraded with the aim of increasing its stability, repetition rate and brightness. An optimization of the electron injector is an essential ingredient for the successful SACLA upgrade. We report the results of beam dynamics studies in the SACLA injector and present possible measures for substantially reducing the present beam emittance. The SACLA injector uses a unique approach for the production of high-brightness electron bunches to drive the XFEL. Specifically, it makes use of a pulsed DC gun and a high-voltage chopper to produce nanosecond electron bunches, which are compressed down to the sub-10 femtosecond duration using ballistic bunching and magnetic compression in chicanes. The emittance quality is, however, not completely preserved due to space-charge forces and chromatic effects during the compression. Hence, we present a strategy for reducing total and slice emittance by reducing the thermal emittance and optimizing emittance compensation. By employing a smaller cathode size, increasing the accelerating field on the cathode and employing a new magnetic microlens, the emittance is reduced by a factor of two.