SHORT SASE-FEL PULSES AT FLASH ¤

FLASH is a high-gain free-electron laser (FEL) in the soft x-ray range. This paper discusses the generation of very short FEL pulses in the Self-Amplified Spontaneous Emission (SASE) - mode without an external seeding signal. In the optimal case a SASE-FEL can be operated in the so-called single-spike mode. At FLASH a new photoinjector laser has been commissioned, which allows the generation of shorter bunches with low bunch charge directly at the photo-cathode. This shorter injector laser reduces the required bunch compression for short pulses and thus allows a stable SASE performance with shorter pulses. First SASE performance using the new injector laser has been demonstrated and electron bunch and FEL radiation properties have been measured. These measurements are presented and next steps towards single spike operation are discussed.