Generation of coherent soft X-ray radiation at high repetition rate

Summary form only given. The process of high harmonic generation (HHG) enables the generation of laser like radiation with extremely short wavelengths. The generated harmonics typically own a wavelength in the nanometer range and attosecond pulse durations thus allow studying nature on extremely small spatial and temporal scales. Naturally there has been a huge interest in extending the wavelength range of HHG into the soft-X-ray region (>125 eV photon energy), providing table-top coherent light sources as an alternative to large scale facilities such as free electron lasers or synchrotrons. In particular the so-called water window, situated in the wavelength range between the K absorption edges of carbon (283 eV) and oxygen (440 eV), is extremely interesting for imaging of living biological structures. Indeed, there have been successful demonstrations of high harmonic generation in noble gasses into the water window spectral region [1]. However, the low conversion efficiency of high harmonic generation in combination with the low repetition rate (~1 kHz) and average power (<;1 W) of the employed Ti:Sa-based laser systems limits the XUV photon flux and consequently hampers potential applications.