The increasing demand for high laser powers is placing huge demands on current laser technology. This is now reaching a limit, and to realise the existing new areas of research promised at high intensities, new cost-effective and technically feasible ways of scaling up the laser power will be required. Plasma-based laser amplifiers may represent the required breakthrough to reach powers of tens of petawatts to exawatts, because of the fundamental advantage that amplification and compression can be realised simultaneously in a plasma medium, which is also robust and resistant to damage, unlike conventional amplifying media. Raman amplification is a promising method, where a long pump pulse transfers energy to a lower frequency, short duration counter-propagating seed pulse through resonant excitation of a plasma wave that creates a transient plasma echelon, which backscatters the pump into the probe. While very efficient, this comes at the cost of noise amplification (from plasma density fluctuations) that needs to be controlled. Here we present the results of an experimental campaign where we have demonstrated chirped pulse Raman amplification (CPRA) at high intensities. We have used a frequency chirped pump pulse to limit the growth of noise amplification, while trying to maintain the amplification of the seed. In non-optimised conditions we show that indeed noise amplification can be controlled but reducing noise scattering also limits the seed amplification factor. Finally, we show that the gross efficiency is a few percent, consistent with previous measurements of CPRA obtained in capillaries with pump pulses of duration of a few hundred picoseconds.
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
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.
The dependence of the yield of high-order harmonic generation (HHG) on several important experimental parameters
has been successfully modeled in the last 20 years by taking into account the single atom response and propagation
effects. We extended this description by adding a stimulated emission process and named it x-ray parametric
amplification (XPA). Beyond the super-quadratic increase of the XUV signal, which can be explained only in a limited
pressure range by HHG theory, other observed characteristics like exponential growth, gain narrowing, strong blue-shift,
beam divergence, etc. and their dependence on laser intensity and gas pressure can be explained accurately only by the
new XPA model. We experimentally demonstrated XPA in Argon in the spectral range of 40-50 eV in excellent
agreement with the theory. XPA holds the promise to realize a new class of bright x-ray sources for spectroscopy.
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.
Taking advantage of the non-adiabatic blue-shift of high-order harmonics generated by a fixed frequency Nd:Glass laser
system, we are able to report more than 50 % coverage of the XUV spectral range between 18 nm and 35 nm. The
generated harmonic lines are capable of seeding Ni-like Y, Zr and Mo soft x-ray lasers and others.
The PHELIX laser at the GSI Helmholtz center for heavy-ion research is dedicated to provide high energy, ultra-intense laser pulses for experiments in combination with energetic ion beams. Development of x-ray lasers is targeting a number of applications in this context, including x-ray laser spectroscopy of highly-charged ions, and Thomson scattering diagnostics of heavy-ion driven plasmas. Recent developments centered on the application of a novel double-pulse
pumping scheme under GRIP-like, non-normal incidence geometry for both the pre- and the main pulse for transient pumped Ni-like lasers. This scheme considerably simplifies the set-up, and provides a very stable pumping situation even at low pump energies close to the lasing threshold. The technique was scaled to pulse energies above 100 J for the pumping of shorter wavelength x-ray lasers. In addition, a slightly tunable high-harmonic source using a split-off beam from the Nd:Glass pre-amplifier of PHELIX was developed as a seeding source.
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).
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.
With PHELIX (Petawatt High Energy Laser for heavy Ion EXperiments) a high energy/ultra-high intensity
laser system is currently under construction at the GSI (Gesellschaft für SchwerIonenforschung, Germany). In
combination with the high current high energy ion accelerator facility this will provide worldwide unique experimental
opportunities in the field of dense plasma physics and inertial fusion research. In the long pulse mode the laser system
will provide laser pulses of up to 5 kJ in 1-10 ns pulses. In the high intensity mode pulse powers in excess of 1 PW will
be achieved. For this the well known technique of chirped pulse amplification (CPA) will be implemented. A new CPA
stretcher-compressor setup for the PHELIX laser was calculated and designed. A 4-pass single-grating stretcher and
a 4-pass single-grating test compressor, both with a full transmission bandwidth of 16 nm, as well as the compact
single-pass compressor for the final pulse compression will be presented. Spatial chirp and spectral phase aberrations of
the stretcher were optimized. We discuss the dependence of critical alignment tolerances on the angle of incidence and
show the effects on the temporal pulse shape.
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.
The Gesellschaft fuer Schwerionenforschung (GSI, Society for Heavy Ion Research) is currently the leading facility in the production of radioactive isotopes. Nuclear properties like charge radii, spin, and magnetic moments of exotic nuclei provide important data for testing of nuclear models. These properties are usually accessed by laser spectroscopy, which requires photon energies of around 100 eV in the case of lithium-like ions. We propose to use a transient gain X-ray laser (XRL) at the experimental storage ring (ESR) to perform this kind of spectroscopy. In this article we describe the planned experiments and give an overview of the current construction at GSI.
The unique combination of an intense heavy ion beam accelerator and a high energy laser opens the possibility of exploring new physics taking advantage of the synergy of both facilities. A variety of new fields can be addressed with this combination in plasma physics, atomic physics, nuclear- and astro-physics as well as material research. In addition, using CPA-technology, laser pulses with a pulse power of up to a petawatt opens the door to explore the regime of fully relativistic plasmas. Therefore the Gesellschaft fuer Schwerionenforschung is augmenting the current high intensity upgrade of the heavy ion accelerator facility with the construction of PHELIX. Designed with two pulse-generating front ends and send to multiple experimental areas PHELIX will serve as a highly versatile laser system for various applications. In this report, we present the design of the laser system and some key experiments that can be performed with this combination for the first time.
For the development of a heavy ion driven inertial confinement fusion scenario a detailed knowledge of the interaction processes of the ions with the converter material is crucial. As this converter will be predominantly in the plasma state one of the main topics of the plasma physics group at Gesellschaft fuer Schwerionenforschung (GSI) is the interaction of heavy ions with dense hot plasma. Based on the latest result on interaction experiments with laser generated plasma targets presented here and concerning the high current upgrade of GSI a new high energy laser system is proposed. It will serve as a driver for interaction experiments with heavy ions as well as a diagnostic tool for heavy ion generated plasmas. In addition, with the combination of high current heavy ion beams and intense lasers innovative, fundamental research in the field of high energy density physics will be accessible for the first time.