First observation of SASE radiation using the compact wide spectral range XUV spectrometer at FLASH2

The Free electron LASer in Hamburg FLASH hasbeenextendedwithanewundulatorlineFLASH2in 2014. Acompactgrazing incidentwide spectral rangespectrometerbasedonspherical variable line spacing SVLS gratingsintheextremeultraviolet XUV regionwasconstructedtooptimizeandcharacterize thefree electronlaser FEL performanceatFLASH2. Thespectrometerisequippedwiththree different concaveSVLSgratingscoveringaspectralrangefrom1to62nmtoanalyzethespectral characteristicsoftheXUVradiation.Wavelengthcalibrationandevaluationofthespectralresolution wereperformedattheplanegratingmonochromatorbeamlinePG2atFLASH1beforetheinstallationat FLASH2, andcomparedwithanalyticalsimulations.The first lightusingself amplified spontaneous emission fromFLASH2wasobservedbythespectrometerduringasimultaneousoperationofboth undulator lines FLASH1 andFLASH2.Inaddition,thespectralresolutionofthespectrometerwas evaluatedbycomparingthemeasuredspectrumfromFLASH2withFELsimulation

A synchronized VUV beamline for time domain two-color dynamic studies at FLASH2

We present a HHG-based vacuum ultraviolet (VUV) source at the free electron laser FLASH2. The source provides ultrashort pulses from 10 to 40eV, coupled to the REMI end-station (beamline FL26) for VUV-FEL pump-probe experiments. (C) 2020 The Author(s

A synchronized VUV beamline for time domain two-color dynamic studies at FLASH2

We present a HHG-based vacuum ultraviolet (VUV) source at the free electron laser FLASH2. The source provides ultrashort pulses from 10 to 40 eV, coupled to the REMI end-station (beamline FL26) for VUV-FEL pump-probe experiments

Synchronized beamline at FLASH2 based on high-order harmonic generation for two-color dynamics studies

We present the design, integration, and operation of the novel vacuum ultraviolet (VUV) beamline installed at the free-electron laser (FEL) FLASH. The VUV source is based on high-order harmonic generation (HHG) in gas and is driven by an optical laser system synchronized with the timing structure of the FEL. Ultrashort pulses in the spectral range from 10 to 40 eV are coupled with the FEL in the beamline FL26, which features a reaction microscope (REMI) permanent endstation for time-resolved studies of ultrafast dynamics in atomic and molecular targets. The connection of the high-pressure gas HHG source to the ultra-high vacuum FEL beamline requires a compact and reliable system, able to encounter the challenging vacuum requirements and coupling conditions. First commissioning results show the successful operation of the beamline, reaching a VUV focused beam size of about 20 mu m at the REMI endstation. Proof-of-principle photo-electron momentum measurements in argon indicate the source capabilities for future two-color pump-probe experiments.(c) 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/)

A synchronized VUV light source based on high-order harmonic generation at FLASH

Ultrafast measurements in the extreme ultraviolet (XUV) spectral region targeting femtosecond timescales rely until today on two complementary XUV laser sources: free electron lasers (FELs) and high-harmonic generation (HHG) based sources. The combination of these two source types was until recently not realized. The complementary properties of both sources including broad bandwidth, high pulse energy, narrowband tunability and femtosecond timing, open new opportunities for two-color pump-probe studies. Here we show first results from the commissioning of a high-harmonic beamline that is fully synchronized with the free-electron laser FLASH, installed at beamline FL26 with permanent end-station including a reaction microscope (REMI). An optical parametric amplifier synchronized with the FEL burst mode drives the HHG process. First commissioning tests including electron momentum measurements using REMI, demonstrate long-term stability of the HHG source over more than 14 hours. This realization of the combination of these light sources will open new opportunities for time-resolved studies targeting different science cases including core-level ionization dynamics or the electron dynamics during the transformation of a molecule within a chemical reaction probed on femtosecond timescales in the ultraviolet to soft X-ray spectral region

Synchronized HHG based source at FLASH

We present a VUV beamline installed as pump-probe source at the free-electron laser FLASH. The source is based on high-order harmonic generation driven by femtosecond near-infrared laser pulses synchronized with the FEL burst mode

Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator

Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs—dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliverMHzpulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length