Service Communautaire d'Information sur la Recherche et le Développement - CORDIS


SHARP Résumé de rapport

Project ID: HPRI-CT-2001-50037
Financé au titre de: FP5-HUMAN POTENTIAL
Pays: France

Plasma mirrors

-Early work (2001-2002): detailed experimental and theoretical study of plasma mirror.
- First application (one stage plasma mirror) to harmonic generation on solid target at CEA 2002
- Two stages plasma mirror configuration at LOA 2003-2004
- Early work on a two stages plasma mirror at CEA 2004
- Conclusion.
- Main publications.
- Deliverables.

- Detailed experimental and theoretical study of plasma mirror:
In this work we demonstrate that, using single plasma mirror with anti-reflection coating the pulse contrast increases by more than 102, with efficiency higher than 60%, and a good beam quality. More detail can be obtained from ref(1).

In order to get a good description of the plasma mirror dynamic a hydrodynamic code was build. This code was validated by comparison with our experimental data as an accurate benchmark. We can now assess the performance of PM mirror and determine the optimum operational fluence on the mirror.

The user-friendly version of the hydro-code on Labwiew platform is available on request.

Several plasma mirror regimes have been identified, the most interesting is the �robust regime�: Pulses shorter than 600 fs and fluence between the triggering threshold (5J/cm) up to 500 joules/cm2. At this condition, the reflectivity is mostly insensitive to the fluence, and is around 70 %.

- First application to harmonic generation at CEA with one stage plasma mirror:
The experience has been performed on the UHI laser of the Saclay Laser Interaction Center (SLIC). This Ti.Sapphire laser produces pulses of 600mJ and 60fs duration. The laser beam was focused by an f/6 off-axis parabola (f=500mm). By setting anti-reflection coated plasma mirror 12mm before the focus the fluence on the PM is about 60 J/cm2. The beam was S polarized with respect to PM surface.
Contrast measurement

The first part of experience aimed at measuring the improved temporal contrast and beam quality. After the PM and after focalization, the pulse was attenuated and collected by an image relay system. The observed focal spot shown no degradation compare to configuration without PM. The temporal contrast has been measured using a SEQUOIA3 third order correlator. This measurement show that the contrast has been improved by about two orders of magnitude, as expected. This improvement extent from ASE to coherent pedestal.

Harmonics generation.
The second part of experience aimed at using the PM to study the interaction of the focalized pulse on solid target.. The peak intensity on the target was estimated to be 3 1018 W/cm2.. The light reflected from the target was send to a flat field XUV spectrometer. High contrast pulse allows interaction with a steep electronic density gradient. As expected a well-collimated beam of even and odd harmonics was clearly observed up to the 20th order.

Paper on this work as been published on Appl.Opt.(ref 2)

To extend this study in the truly relativistic regime I >> 1018 W/cm2, the contrast should be increase more and that requires the use of two successive plasma mirrors.

- Double plasma mirror configuration at LOA:
A double plasma mirror has been implemented one the �Laser salle jaune� of the LOA at ENSTA. This Ti.Sa. laser produces 1 Joules, 35 fs, pulses. The main goal was a 104 contrast increasing, using a user-friendly DPM configuration. Of course this DPM should be easily removable. The plasma mirror should be put at the laser front end, before the experimental chamber.

At least on plasma mirror is working in the intermediate field where the amplitude distortions are larger for actual beam. In order to optimize this type of configuration and predict actual performance, we have build a time dependent 2D optical propagation code. This codetake into account local reflectivity on plasma mirrors and propagation between mirrors and to the final target. This open source code has been build with Labview platform and is easily transportable

As conclusion using this new installation, Contrast greater than 1011 is obtain, Output beam can be focused in a very nice focal spot, More than 50% efficiency obtained on target.

- Early work on a two stages plasma mirror at CEA.-2004:
Construction of this double plasma mirror is extrapolated from the LOA configuration in a more compact scheme. The overall length is reduced to 2 meter at the expense of a reduced number of shot (100), before changing the plasma mirror..

- Main publications :
-- Phys. Rev. E 69, 026402 (2004)
-- Optics Letters 15, / 2004 / vol. 29, No. 8

- Deliverables:
Construction of Single plasma mirror at CEA , Construction of double plasma mirror LULI and CEA, 2D simulation code for multiple plasma mirror (Open source on Labview platform).

Informations connexes

Reported by

écolle polytechnique
91128 Palaiseau
See on map