Generation and application of femtosecond X-rays from a synchrotron

We demonstrate a novel scheme for generating ultrashort pulses of synchrotron radiation. Our approach is to create femtosecond time-structure on a long electron bunch by using a femtosecond laser pulse to modulate the energy of an ultrashort slice of the bunch Femtosecond synchrotron pulses are directly measured from a bend-magnet beamline at the Advanced Light Source (ALS). The measured pulse duration is determined by the storage ring dispersion integrated from the wiggler to the radiation bend-magnet. A new beamline, dedicated to ultrafast X-ray spectroscopy is currently under construction at the ALS and will provide X-ray pulses of <100 fs duration. The femtosecond time structure is invariant over the entire spectral range of bend-magnet emission from the near infrared to the X-ray regime, making this a powerful tool for femtosecond X-ray spectroscopy.