High Harmonics Generation from Gas and Solid ,
soft X-ray plasma creation based on solid-target ,
x-ray laser pumb-probe experiment ,
High Harmonics seeded Soft X-ray Laser ,
Hartmann wave front sensor ,
development and applications of x-ray attosecond pulse
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X-ray free-electron lasers (FELs) are powerful tools for probing matter properties down to sub-nanometer scales with femtosecond time resolution, allowing a growing number of physical, chemical, biological and medical investigations to be carried out. FELs operating in seeding mode intrinsically present enhanced temporal coherence properties with respect to those relying on the self-amplified spontaneous emission (SASE) process. They are however limited, for the moment, to extreme ultraviolet (XUV) wavelengths, or in some cases to soft X-rays, and durations of tens of femtoseconds. We studied how these limits can be overcome by means of X-ray chirped pulse amplification, inspired by infrared lasers.
As a matter of fact, the use of a seed enables a fine control of the chirp and a spectro-temporal shaping of the FEL emission. Moreover, ultrashort wavelengths can be envisaged through schemes of high-gain harmonic generation and echo-enabled harmonic generation. We will present FEL simulations coupled with the study of a compressor in conical diffraction geometry.
We present in this paper a laser-driven coherent EUV beamline resulting from the combination of a versatile
high-order laser harmonic generator with a robust plasma-based EUV laser amplifier. Both devices can be used
separetely or in synergy. Seeding of the plasma amplifier by a high-order harmonic beam leads to a strong
improvement of the EUV laser beam divergence and uniformity. Moreover the system can be turned easily into
a IR pump-XUV probe setup for plasma opacity probing. The possibility to generate two separate harmonic
sources from the same gas cell offers the opportunity to explore EUV pump-EUV probe experiments.
Ultra-intense X-ray sources have opened new avenues by creating new states of matter or probing and imaging living or inert matter. Free-electron lasers have a strong leadership by delivering pulses combining femtosecond duration and 10s of microJoules to milliJoule energy. However, these sources remain highly expensive limiting their number to a few worldwide. In parallel, laser-pumped soft X-ray lasers hold outstanding promises having demonstrated the most energetic monochromatic soft x-ray pulse and being intrinsically fully synchronized with any secondary source of the pump laser. Since the first successful demonstration of amplification of a high harmonic pulse in a plasma from gas in 2003 and from solid in 2008, we have developed an extensive numerical study. 2D hydrodynamic simulations showed that optimized Transient Collisional Excitation plasma amplifiers, may store up to 0.4 mJ in the population inversion. If carefully seeded, pulses of 80 fs and 20 μJ might be generated with table-top lasers (10J). As the energy extracted is far from the milliJoule requirements of most exciting applications, we studied the seminal experiment of Ditmire et al who seeded a plasma emitting milliJoules in the form of Amplified Spontaneous Emission (ASE).We retrieved and explained for the first time the experimental result (ASE 1,000 times stronger than amplified seed). We thus proposed and fully modeled the transposition of the so-called Chirped Pulse Amplification (CPA) in the soft X-ray range, showing that 6 mJ, 200 fs, fully coherent soft X-ray pulse is accessible with compact pump lasers.
An experiment was set up to measure the wavefront of an injection-seeded soft x-ray laser based on a solid-target plasma amplifier. The 43rd harmonic signal from a Ti:Sa laser was used to seed a molybdenum plasma amplifier operating in the λ=18.9 nm line of Ni-like Mo. A Hartmann wavefront senor with an accuracy of λ/32 rms at this wavelength was employed to measure the wavefront of both the high harmonics seed and the seeded soft x-ray lasers. A significant improvement in wavefront aberration from 0.51±0.04λ rms to 0.25±0.03λ rms was observed as a function of plasma column length. The variation of wavefront characteristic by the time delay between the injection of the seed and the peak of soft x-ray amplifier pump was studied in this paper.