Hartmann wavefront sensors and their application at FLASH

Keitel, Barbara; Plönjes, Elke; Kreis, Svea; Kuhlmann, Marion; Tiedtke, K.; Mey, Tobias; Schäfer, Bernd; Mann, Klaus

doi:10.1107/s1600577515020354

Cited by 45 publications

(22 citation statements)

References 15 publications

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“…Gas monitor detectors are able to measure the total photon number in a single, few-femtosecond pulse 9 , but cannot account for the intensity distribution within the focal spot on the sample. This distribution is typically measured separately from the actual experiment using wave-front sensing 10 – 12 , ablative imprints 13 , 14 , or by detecting the transmitted intensity through a small aperture or behind a sharp knife-edge scanned across the beam in the sample plane 2 , 15 . These approaches are highly invasive and cannot be performed in tandem with the majority of FEL experiments.…”

Section: Introductionmentioning

confidence: 99%

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses

Schneider

Günther

Pfau³

et al. 2018

Nat Commun

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Free-electron lasers (FELs) in the extreme ultraviolet (XUV) and X-ray regime opened up the possibility for experiments at high power densities, in particular allowing for fluence-dependent absorption and scattering experiments to reveal non-linear light–matter interactions at ever shorter wavelengths. Findings of such non-linear effects are met with tremendous interest, but prove difficult to understand and model due to the inherent shot-to-shot fluctuations in photon intensity and the often structured, non-Gaussian spatial intensity profile of a focused FEL beam. Presently, the focused beam is characterized and optimized separately from the actual experiment. Here, we present the simultaneous measurement of XUV diffraction signals from solid samples in tandem with the corresponding single-shot spatial fluence distribution on the actual sample. Our in situ characterization scheme enables direct monitoring of the sample illumination, providing a basis to optimize and quantitatively understand FEL experiments.

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Section: Introductionmentioning

confidence: 99%

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses

Schneider

Günther

Pfau³

et al. 2018

Nat Commun

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“…In addition to the photon energy, pulse duration, and spectral characteristics, it is important to have an accurate knowledge of the single pulse x-ray wavefront, which affects focal plane intensity and profile, spot size, and spatial resolution, as well as centroid location within the focal plane. Among techniques currently in use are the following: burn patterns that ablate material as a function of intensity across the focal plane [5,6]; Hartmann masks, which track localized wavefront vectors [7,8]; double grating interferometers, each grating having a two-dimensional checkerboard pattern, where the second grating produces a spatially downshifted Moiré pattern [9,10]; and x-ray speckle tracking techniques [11].…”

Section: Introductionmentioning

confidence: 99%

High-accuracy wavefront sensing for x-ray free electron lasers

Liu

Seaberg

Zhu

et al. 2018

Optica

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Systematic understanding and real-time feedback capability for x-ray free electron laser (FEL) accelerator and optical components are critical for scientific experiments and instrument performance. Single-shot wavefront sensing enables characterization of the intensity and local electric field distribution at the sample plane, something that is important for understanding scientific experiments such as nonlinear studies. It can also provide feedback for alignment and tuning of the FEL beam and instrumentation optics, leading to optimal instrument performance and greater operational efficiency. A robust, sensitive, and accurate single-shot wavefront sensor for x-ray FEL beams using single grating Talbot interferometry has been developed. Experiments performed at the Linac Coherent Light Source (LCLS) demonstrate 3σ sensitivity and accuracy, both better than λ∕100, and retrieval of hard x-ray (λ 0.13 nm, E 9.5 keV) wavefronts in 3D. Exhibiting high performance from both unfocused and focused beams, the same setup can be used to systematically study the wavefront from the FEL output, beam transport optics, and endstation focusing optics. This technique can be extended for use with softer and harder x rays with modified grating configurations.

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“…For direct measurement of the XUV intensity profile, the XUV camera is placed directly after the filters without spectrometer. For wavefront measurement, the XUV camera is replaced by a XUV wavefront sensor with alignment for tip/tilt and the vertical/horizontal axis [24,25] and a 300 nm-thick Al filter without supporting mesh is used. …”

Section: Introductionmentioning

confidence: 99%

Optimization and Characterization of High-Harmonic Generation for Probing Solid Density Plasmas

Koliyadu

Künzel²,

Wodzinski³

et al. 2017

Photonics

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Abstract:The creation of high energy density plasma states produced during laser-solid interaction on a sub-picosecond timescale opens a way to create astrophysical plasmas in the lab to investigate their properties, such as the frequency-dependent refractive index. Available probes to measure absorption and phase-changes given by the complex refractive index of the plasma state are extreme-UV (EUV) and soft X-ray (XUV) ultra-short pulses from high harmonic generation (HHG). For demanding imaging applications such as single-shot measurements of solid density plasmas, the HHG probe has to be optimized in photon number and characterized in intensity and wavefront stability from shot-to-shot. In an experiment, a coherent EUV source based on HHG driven by a compact diode-pumped laser is optimized in photons per pulse for argon and xenon, and the shot-to-shot intensity stability and wavefront changes are characterized. The experimental results are compared to an analytical model estimating the HHG yield, showing good agreement. The obtained values are compared to available data for solid density plasmas to confirm the feasibility of HHG as a probe.

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Hartmann wavefront sensors and their application at FLASH

Cited by 45 publications

References 15 publications

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses

In situ single-shot diffractive fluence mapping for X-ray free-electron laser pulses

High-accuracy wavefront sensing for x-ray free electron lasers

Optimization and Characterization of High-Harmonic Generation for Probing Solid Density Plasmas

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