Laser Produced Plasma of Volume Structured Media
High Intensity Laser-Produced Plasma of the Volume Structured Media
Tech Area / Field
- PHY-PLS/Plasma Physics/Physics
3 Approved without Funding
FIAN Lebedev, Russia, Moscow
- VNIIEF, Russia, N. Novgorod reg., Sarov
- Los-Alamos National Laboratory, USA, NM, Los-Alamos\nRochester University, USA, NY, Rochester\nScience and Technology Facilities Council, UK, Didcot\nENEA, Italy, Frascati\nLawrence Livermore National Laboratory, USA, CA, Livermore
Project summaryThe object of the Project is to study the physics of interaction of a high power laser pulse with the volume-structured media, and to investigate the properties of the plasma produced in the process of such an interaction. The volume-structured media represents a substance whose physical properties (density, the type of structure and atom composition) change in volume either stochastically (for a foam-like structure) or according to the regular law (honeycomb or layered structure). Of particular interest is the interaction of laser radiation with a volume-structured media, whose macrodensity is close to the density 10-1 to 10-3 g/cm3 corresponding to the plasma resonance for the wavelength of short-wavelength-lasers.
The theoretical predictions and first experiments on interaction power laser pulse with low dense foam media /1,2,3/ have shown that the energy transfer in a laser-produced plasma of foam target has a complex hydro-kinetic character and the parametric processes are quite important for the laser radiation absorption in these conditions.
Within the framework of the Project there were studied both theoretically and experimentally such fundamental physical phenomena in the laser-produced plasma of the volume structured media such as the volume inverse Bremsstrahlung absorption of the laser radiation, the behavior of the parametric instabilities and their influence on the laser radiation absorption and energy transfer, the direct plasma heating by a laser radiation up to temperatures of several keV, initiation of supersonic waves of the electron and radiation heat conductivity, dependence of thermophysical plasma properties and transfer coefficients on the initial parameters of a structured media.
The expected results on the Project are the following. For the stochastically and regularly structured media, depending on the macrodensity of the matter, the composition of the latter elements, and on the ratio of a size of an elementary matter cell and a focal size of the laser radiation, there will be determined experimentally the following parameters:
- energy balance at an interaction of a laser radiation pulse with plane and spherical targets, including a part of the energy absorbed in the target, energy of the thermal self-radiation of the plasma, energy of the scattered emission at the basic frequency, including SBS scattering;
- absorbed energy balance within a laser pulse action, including a part of the absorbed energy contained in the thermal component, and a hydrodynamic motion of the plasma matter (plane and spherical targets);
- spatial and time temperature distributions of the plane target plasma;
- velocities of the longitudinal and transversal (in respect of the laser incidence onto a target) transfer of the absorbed laser energy in the plasma of plane targets;
- spectrum of X-ray plasma emission of the plane targets;
- laser intensity thresholds of the plasma instabilities.
On the basis of the experimental data and the results of numerical simulation of the above processes there will be elaborated a model of the physical processes occurring in the formation of laser plasma of the volume structured media, and the plasma thermophysical and optical properties will be determined.
Methodology of the proposed Project will be based on studying the influence of the medium initial structure on the processes of laser-target interaction, and on the properties of the produced plasma. Such an approach includes a comparison of the results obtained from the experiments on laser interaction with the regularly structured matter, stochastically structured matter and the solid matter of the same element composition.
The experiments will be performed on high-power laser facilities of VNIIEF iodine laser "Iskra-4"/ 4 / (400 J energy, the wavelength l @ 0.657 mm, and the pulse duration t0.5 = (0.3-1.0) ns), and FIAN Nd-laser facility "Mishen" / 5 / (200 J energy, l = 1.06 mrn, t0.5 @ 2.5 ns. The X-ray and optical methods of the plasma diagnostics are to be used, including the ones with the temporal resolution of @ 20-40 ps and space resolution of @ 50-100 mm. The theoretical studies and the analysis of experimental results will be based on the numerical calculations of two- and three-dimensional computer programs developed at VNIIEF and FIAN. The technique of preparation of low-density stochastically and regularly structured media is further developed.
The Project results will be important for the solution of some applied problems such as elaboration of the methods of a control of uniformity of the absorbed laser energy distribution in matter, as well as an elaboration of the laboratory sources of hard X-ray emission of high brightness, and a laboratory simulation of the astrophysical phenomena.
The Potential Role of the Foreign Collaborators
The collaboration with Rutherford Appleton laboratory (Great Britain) and ENEA Inertial Fusion Physics and Technology Group (Frascati, Italy) will include the performance of joint experimental and theoretical investigations on laser interaction with volume-structured matter, the exchanging and discussion of scientific results and the preparation of joint publications. Both laboratory are especially interested in investigation of the physics of energy transfer in laser-produced plasma of volume-structured media and a laboratory simulation of astrophysical phenomena by using such a plasma.
1. S.Yu.Gus'kov, N.V.Zmitrenko, V.B.Rozanov. ZhETF, 108, 2 (8), 548 (1995) (in Russian); JETP 81 (2), 296 (1995) (in English).
2. J.A.Koch, K.G.Estabrook, G.D. Buur et al. Phys. Plasmas 2 (10), 3820 (1995). 3.1.N.Burdonsky, A.E. Bugrov, V.V. Gavrilov et al. Specific features of absorption and energy transfer processes in low density porous targets irradiated with powerful laser pulses.. Book of abstracts of 24th European Conf. on Laser Interaction with Matter, Madrid (Spain), June 3-7, 1996.
4. 1.N.Voronitch, A.I.Zaretski, G.G.Kochemasov et al. Czechoslovak J.of Phys, 42 (10), 963 (1992).
5. V.A.Bolotin, I.N.Burdonsky, V.V.Gavrilov et al. Rev. Sci. Instrum. 61, 3259 (1991).
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