Bocoum, Maïmouna (2012) Diffraction X du fer à haute résolution temporelle PFE - Project Graduation, ENSTA.



Iron’s equation of states is still subject to controversy today. However, models developed by astrophysicists and planetary physicists directly rely on a good comprehension of iron’s behavior under high conditions when describing earth-like planetes. High energy laser installations have been very helpful during the last decades because experiments on iron at high pressure (> 100GPa ) were possible. Indeed, it is possible using lasers to reach high pressure and probe compressed matter on time scales that have never been achieved before. Compression is also pos- sible using standard diamon static compression, but in that case, researchers are confronted with thermodynamical instabilities inherent to the much longer time scales (few seconds) required for observation. With its two high intensity beams, LULI2000 is the appropriate installation to bring matter into extreme conditions using a nanosecond north beam and simultaneously probe it using a south picosecond impulsion. The aim of the experimental campaign presented here is to detect fusion of iron at high pressure by X-ray diffraction. In order to reach high pressures, we shock an iron target using an intense nanosecond laser beam. In particular, we expect to see the disparition of Bragg diffraction pics and the appearance of a diffusion signal, which is the signature of the crystalline phase transformation into a liquid phase. We will also present important diagnostics such as Visar, which enables a measure of the shock velocity into the target. The algorithm used to process the Visar image and therefore derive the velocity will be exposed. Moreover, we will present some of the results given by the SOP diag- nostics, which allows a time resolved measure of the temperature. The interpretation deriving from the SOP will be mainly qualitative since the proper calibration of the streak could not be done before the beginning of the campaign. All these diagnostics are important to have an independant characterization of our system’s thermodynamic state.

Item Type:Thesis (PFE - Project Graduation)
Subjects:Mathematics and Applications
ID Code:6461
Deposited By:Sophie Chouaf
Deposited On:03 déc. 2013 17:59
Dernière modification:03 déc. 2013 17:59

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