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.
The potential for coherent extreme ultra-violet (EUV) light in probing laser-produced plasmas is investigated. New
results are presented to demonstrate that EUV radiation can be employed to measure heat penetration into solid targets
from electrons using the signature of a change of opacity due to heating. We examine, in particular, the effects of hot
electron heating of targets. In addition, phase variations after transmission through a laser-irradiated target change the
subsequent propagation of the radiation, suggesting a simple diagnostic measuring the far-field footprint of coherent
EUV radiation can be a useful measurement of the uniformity of target heating.
We present an experimental design to independently pump two soft X-ray laser media suitable for a seed-amplifier
configuration. Both the seed and the amplifier target are operated in the TCE scheme utilizing the DGRIP technique with
its intrinsic travelling wave excitation. Controlled injection of the seed X-ray laser into the amplifier medium is realized
via a spherical XUV mirror. The experimental design is perfectly appropriate for benchmarking combined simulations of
the ARWEN and DeepOne code. A first experiment at the PHELIX laser utilizing this scheme has been conducted,
demonstrating signs of amplification and allowing for the direct measurement of the gain life time of a Ni-like silver
SXRL.
We report recent experimental measurements of the duration of a Ni-like Mo transient XUV laser emitted at 18.9 nm and
generated under GRIP geometry at the LASERIX facility. These measurements have been performed using an ultra-fast
X-ray streak camera (AXIS Photonique). A new trigger line was implemented, yielding a shot-to-shot jitter of less than
10 ps. The KBr photocathode of the streak camera was positioned close to the plane of the magnified near-field image of
the XUV laser emitting aperture. Saturation in the streak camera was avoided by carefully adjusting the signal level of
the focused image. The sweep speed was calibrated in-situ by generating a double-pulse XUV laser. Finally the temporal
resolution of the instrument was measured directly with a femtosecond, high-order harmonic pulse. XUV laser pulse
durations as short as 2.8 ps were measured for a 20° GRIP angle and a 0.75 ps GRIP pulse duration. We present and
discuss our study of the effect of these two parameters on the measured pulse duration.
We measured the linewidth of a λ= 46.9 nm neon-like argon capillary discharge soft x-ray laser. A wavefront division
interferometer based on a pair of dihedrons was used to resolve the laser line measuring the variation in the interference
fringe visibility for different optical path differences. We measured a relative linewidths of Δλ/λ = 3-4 10-5. No
significant re-broadening was observed when the length of the laser medium was increased beyond the saturation length
due to effects that homogenizes the line profile.
We present in this paper some effort and prospects in order to turn a high intensity infrared laser facility into a
installation providing external users with EUV coherent sources. Development of an harmonic beamline based
on quasiphase matching in capillary is presented. Plasma based soft x-ray laser scheme involving a plasma seeder
and an amplifier is revisited with the aim of obtaining a robust fully coherent x-ray laser.
LASERIX is a high-power laser facility leading to High-repetition-rate XUV laser pumped by Titanium:Sapphire laser.
The aim of this laser facility is to offer Soft XRLs in the 30-7 nm range and auxiliary IR beam that could also be used to
produce synchronized XUV sources. This experimental configuration highly enhances the scientific opportunities of the
facility, giving thus the opportunity to realize both X-ray laser experiments and more generally pump/probe experiments,
mixing IR and XUV sources. In this contribution, the main results concerning both the development of XUV sources(X-Ray
lasers and HHG sources) and their use for applications are presented.
We present a comprehensive theoretical analysis of the conditions that lead to absorption limited generation of
high order harmonics in the case of low energy, long pulse duration infrared pump laser beams. With these pump
laser beam parameters, tight focussing is necessary to reach the high laser intensity required for high non linear
response at the atomic level. A limitation of phase-matching is then induced through the so-called Gouy phase
shift. We explain how the positive atomic dispersion can compensate for that effect and derive the conditions for
perfect phase matching. The influence of gas pressure, harmonic order, maximum laser intensity and focussing
conditions are analysed. This work enables a precise separation between pure classical harmonic from possible
XPA effects discussed in a recent experiment. It also constitutes a benchmarking of a code under development
for quasi phase matching scheme investigation.
We report spatial and spectral characterization an optical-field-ionized high-order harmonic-seeded soft-x-ray laser. We
show that it can be controlled between a regular Gaussian shape and a Bessel profile exhibiting several rings via the IR
laser pump intensity. The temporal coherence and spectral linewidth of both the seeded and unseeded soft-x-ray lasers
were experimentally measured using a varying path difference interferometer. It showed that the high-order harmonic is
subject to a strong spectral narrowing during its propagation in the plasma amplifier without rebroadening at saturation.
Also, we present a new method to generate ultra-short x-ray laser pulses by using the laser-driven betatron source to
photo-pump inner-shell transitions.
We describe our recent progress in the investigation of the spectral properties of collisional XUV lasers, including both
experimental measurements and numerical calculations. Using a wavefront-division, variable path-difference
interferometer, we have characterized the temporal coherence and the spectral width of an injection-seeded transient
XUV laser emitted at 18.9 nm from a Ni-like Mo plasma. Our results show that the temporal coherence of the beam is
significantly increased by the injection-seeded operation, compared to the standard ASE mode, in agreement with
detailed numerical simulations. Using the PPP code we have calculated the intrinsic linewidth of the same lasing line
over a range of electron density and at temperatures that are relevant to transient collisional pumping. We discuss the
relative contributions of homogeneous and inhomogeneous broadening to the overall profile.
In this paper we report the perspectives of the development of the XUV laser sources and applications using High-power laser facilities. We focus our paper on the present status of the French LASERIX facility and more especially about its role in the development of the XUV laser sources considering the French "Institut de la Lumière Extrême " (ILE) and the potential European project Extreme Light Infrastructure (ELI).
Finally, we present the scientific perspectives of X-ray laser sources developments using these laser facilities.
The demonstration of a 7.36 nm Ni-like Sm soft x-ray laser pumped by 36 J of a Nd:glass chirped pulse amplification laser is presented. Double-pulse single-beam non-normal incidence pumping was applied for the efficient soft x-ray laser generation. Here the applied technique included a new single optic focusing geometry for large beam diameters, a single-pass grating compressor traveling-wave tuning capability and an optimized high energy laser double-pulse. This scheme has the potential for even shorter wavelength soft x-ray laser pumping.
University Paris XI has developed a facility, which called LASERIX, intended to realize and use for applications transient collisional X-ray laser (XRL) beamlines at various wavelengths. It is based on the effect caused by beamlines of the ultra-intense infrared laser (100TW) rip into the high-density and high-temperature plasma, providing XUV laser pulses at alterable wavelengths of 7-40nm This soft-X laser source is widely used in biology, bio-medical, solid physics, plasma physics and many other domains. In order to make LASERIX a stable XUV laser source, the stable infrared beams are neededThe stability of the beams enhances the energy of X laser pulses. A system of detecting temperatures in different points of the laser chain and monitoring laser beam has been developed. For the second step, a new compressor has been built to produce auxiliary infrared laser beam which helps to improve the XUV pulse's energy. This article elaborates on the design and installation of them with the results discussed.
Stable and reliable operation of a nickel-like molybdenum transient collisional soft x-ray laser at 18.9 nm demonstrated and studied with a 10Hz Ti:sapphire laser system proves the suitability of the double-pulse non-normal incidence pumping geometry for table-top high repetition soft x-ray lasers and broadens the attractiveness of x-ray lasers as sources of coherent radiation for various applications. X-ray laser emission with pulse energies well above 1 μJ is obtained for several hours at 10Hz repetition-rate without
re-alignment under optimized double pumping pulse parameters including energy ratio, time delay, pulse duration and line focus width.
The LASERIX facility provides coherent and short soft x-ray beams for scientific applications. The beams are generated through high intensity laser interaction with matter using two different schemes, plasma based soft x-ray lasers, and high order laser harmonic generation. We describe in this communication the present status
of the facility. The LASERIX beamtime has been recently opened to external users. We present two typical experiments performed in that context with the facility. The first one is dedicated to the fundamental study of the plasma based soft x-ray laser, whereas the second uses the existing beam to study irradiation induced
dammage in DNA samples. We present also the development performed on the soft x-ray laser source to improve its stability and high repetition rate operation.
We present recent calculations performed with the Maxwell-Bloch COLAX code. We investigate several features of
transient X-ray lasers pumped with grazing incidence geometry and operated either with or without seeding by a highorder
harmonics pulse. We show that the spontaneous emission source term included in the code accounts well for the
speckle patterns observed in near-field and far-field images of the amplification of spontaneous emission (ASE) beams.
Our calculations confirm the predictions of a simpler model based on the properties of spatial and temporal coherence of
the source. We study the role of varying the level of the harmonic pulse seeded in the X-ray laser plasma. We show that
the amplification factor and the contrast with respect to the ASE background cannot be maximized simultaneously.
Finally we describe a recent upgrade of the code in which a time-dependent description of the populations of the lasing
states has been implemented. This more rigorous treatment allows us to investigate the small-scale temporal behaviour of
seeded X-ray lasers. The new version of the COLAX code was recently tested and preliminary results will be presented.
In this paper we present the perspectives of the development of the XUV laser sources using High-power laser facilities.
We focus our paper on the present statuts of the LASERIX facility and especially its role in the development of the XUV
laser sources considering the French "Institut de la Lumière Extrême" (ILE) and the potential European project Extreme
Light Infrastructure (ELI).
S. Liehn, C. Le Sech, E. Porcel, B. Zielbauer, J. Habib, S. Kazamias, O. Guilbaud, M. Pittman, D. Ros, M.-A. Hervé du Penhoat, A. Touati, H. Remita, S. Lacombe
Samples of plasmid DNA were irradiated with pulsed 18.9 nm radiation originating from a Mo X-ray laser (XRL)
pumped in GRIP configuration at the LASERIX facility. Up to 21 000 pulses were delivered with a repetition rate of 10
Hz and average pulse energy of 200 nJ. Radiosensitization by two different platinum compounds (platinum terpyridine
chloride (PtTC) and platinum nanoparticles) were investigated. SSB and DSB yields were measured using agarose gel
electrophoresis. The occurrence of single and double strand breaks not present in controls having undergone the same
treatment except for the XRL irradiation can be seen as a clear effect of the XRL irradiation. This confirms the role of
direct effects in DNA damages as previously seen with low energy ions and electrons (1) (2). In addition we demonstrate
a DNA breaks enhancement in the presence of platinum. No difference of enhancement was seen between these two
radiosensitizers.
We present in this paper theoretical and experimental investigations of temporal and spectral properties of seeded
soft x-ray lasers. Bloch-Maxwell simulations of the harmonic pulse propagation in a soft x-ray laser plasma have
been performed. Results show a growing wake of coherent radiation formed after the harmonic pulse.We describe
the first measurement of the spectral bandwidth of a seeded soft
x-ray laser. Using a varying path difference
interferometer the spectral profile of a seeded OFI x-ray laser has been experimentally determined, leading to
a Fourier-transform pulse duration of 5ps. The measured bandwidth is in good agreement with simulations.
Finally we present the progress toward the implementation of a seeded soft x-ray laser at 18.9 nm at the new
LASERIX facility.
LASERIX is a high power laser facility intended to realise and use for applications transient collisional excitation (TCE)
X-ray lasers (XRLs) at various wavelengths, using grazing incidence pumping (GRIP) configuration with 10 Hz
repetition rate. In addition new types of XRL schemes giving rise to emission at short wavelengths will be developed
using the high energy LASERIX driver with 0.1 HZ rep-rate. Thus, this laser facility will both offer Soft X-ray lasers in
the 40-10 nm range and synchronised auxiliary IR beam that could be also used to produce XUV sources. This
experimental configuration highly enhances the scientific opportunities of the facility. Indeed it will be possible to realise
both X-ray laser experiments and more generally pump/probe experiments, mixing IR and XUV sources. Then, this
facility will be useful for the community, opening a large scale of investigations, including imagery and irradiation as
illustrated in the case of laser Interaction with matter investigations using XUV interferometry.
We present a detailed analysis of an experiment carried out recently in which the temporal coherence of the Ni-like silver transient X-laser at 13.9 nm was measured. Two main consequences of this measurement will be discussed and interpreted with numerical calculations. First we show that the high temporal coherence length measured corresponds to an extremely narrow spectral width of the X-ray laser line. Second we show that the high temporal coherence helps to explain the presence of small-scale structures observed in the cross-section of all transient X-ray laser beams.
Future progress of x-ray lasers call for specific facilities intended to x-ray laser studies and development of a large variety of x-ray laser applications. This paper presents LASERIX, a future x-ray laser facility under construction for optimization of transient collisional excitation x-ray lasers, study of new x-ray laser schemes, and development of applications.
We review our recent progress in the development of transient x-ray lasers and of their application to plasma diagnostic. The first observation of C-ray laser emission at the new PHELIX-GSI facility is reported. This TCE X-ray laser will be a promising tool for heavy-ion spectroscopy. We then present the main results obtained at the LULU-CPA facility with a compact high-resolution X-UV imaging device. This device was used to investigate the spatial source structure of the Ni-like silver transient X-ray laser under different pumping conditions. The key-role of the width of the background laser pulse on the shape of the emitting aperture is demonstrated. Finally the imaging device was used as an interference microscope for interferometry probing of a laser-produced plasma. We describe this experiment performed at APRC-JAERI.
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