Free-electron laser temporal diagnostic beamline FL21 at FLASH.

A beamline for temporal diagnostics of extreme ultraviolet (XUV) femtosecond pulses at the free-electron laser in Hamburg (FLASH) at DESY was designed, built and put into operation. The intense ultra-short XUV pulses of FLASH fluctuate from pulse to pulse due to the underlying FEL operating principle and demand single-shot diagnostics. To cope with this, the new beamline is equipped with a terahertz field-driven streaking setup that enables the determination of single pulse duration and arrival time. The parameters of the beamline and the diagnostic setup as well as some first experimental results will be presented. In addition, concepts for parasitic operation are investigated.

An X-ray gas monitor for free-electron lasers.

A novel X-ray gas monitor (XGM) has been developed which allows the measurement of absolute photon pulse energy and photon beam position at all existing and upcoming free-electron lasers (FELs) over a broad spectral range covering vacuum ultraviolet (VUV), extreme ultraviolet (EUV) and soft and hard X-rays. The XGM covers a wide dynamic range from spontaneous undulator radiation to FEL radiation and provides a temporal resolution of better than 200 ns. The XGM consists of two X-ray gas-monitor detectors (XGMDs) and two huge-aperture open electron multipliers (HAMPs). The HAMP enhances the detection efficiency of the XGM for low-intensity radiation down to 105 photons per pulse and for FEL radiation in the hard X-ray spectral range, while the XGMD operates in higher-intensity regimes. The relative standard uncertainty for measurements of the absolute photon pulse energy is well below 10%, and down to 1% for measurements of relative pulse-to-pulse intensity on pulses with more than 1010 photons per pulse. The accuracy of beam-position monitoring in the vertical and horizontal directions is of the order of 10 µm.