A large spectrum of plasmas exists naturally or artificially. Their creation processes, their control and the understanding of their underlying physics are tighly bound to facilities and their up-to-date associated technologies and to numerical simulations of the physical processes at any scale from microscopic to macroscopic scales as well. Here below a non comprehensive list of those plasmas found is given in various contexts.
|Development of a method of dose calculation for the radiotherapy: The precise and fast algorithms of the dose deposition are necessary for the improvement of the plans of treatment in the radiotherapy. The deterministic model of transport of particles based on the resolution of the equation of Fokker-Planck proposes a better quality of calculation in the heterogeneous tissues such as bones or lungs compared the commercial software “Pencil Beam”. Figure shows the isodose deposited by electrons (red) propagating through the trunk bones showed in gray.
Credit : B Dubroca – CELIA, 2012
Plasmas for inertial confinement fusion
Development of the numerical methods in hydrodynamics of plasmas: The numerical simulations in the domain of inertial fusion are performed with the Lagrangian method. It requires improvements of robustness in order to describe the flows with large vorticity and shear. The figure shows the performance of a new method of grid regularization ReALE (reconnection based arbitrary Lagrangian Eulerian) which allows to build an evolutionary mesh by using the polygons of Voronoï. It adapts itself naturally to big distortions of the flow that take place for example in the development of Kelvin-Helmholtz instability.
J Breil, S. Galera, P-H Maire, CELIA, Computers & Fluids 46, 161 (2011)
Laser smoothing with an underdense foam: In the direct drive approach to inertial confinement fusion, inhomogeneities in the laser beam intensity may seed pressure perturbations and induce hydrodynamic instabilities that undermine the target performance. The use a low density foam on the target front-side enables laser beam smoothing and reduces the hydrodynamic instability growth. Figure presents an optical streak image providing a direct measurement of the ionization front induced by the laser beam in a foam.
Ph. Nicolaet al., CELIA, Phys. Plasmas 19, 113105 (2012)
Kinetic simulations of stimulated Raman backscattering for shock-ignition: Shock ignition of the inertial fusion operates in the domain of laser intensities where the parametric processes may contribute to the laser energy absorption and hot electron generation. These processes can be described in full kinetic simulations using high performance computers. Figure shows the angular and spectral distribution of the scattered laser light due to the Raman instability.
C. Riconda, S. Weber, V.T. Tikhonchuk, A. Heron, LULI-CELIA-CPHT, Phys. Plasmas 18, 092701 (2011)
Interpretation of shock-ignition experiment on OMEGA laser facility: In experiments conducted on the Omega laser facility we studied the effect of converging shock on the shell compression and the neutron yield. 40 uniformly distributed beams were used to compress a cryogenic Deuterium shell and 20 beams have been focused on a dodecahedron to launch the choc. 2D hydrodynamic simulations show the density and temperature profile of the target stagnation, Rayleigh-Taylor instability modulations seen in the figure were measured experimentally and compared to the code. Agreement on the shape of the modulation is clear however, however the simulations overestimate the shell compression.
W. Theobald et al., Phys, Plasmas 19, 102706 (2012)
Aluminum plasma: Snapshot of expanded aluminum at 1.4 g/cm3 and 10000K computed with a quantum molecular dynamics code.
Crédit : J. Clerouin – CEA – 2012
Magnetized plasmas and magnetic confinement fusion
Instantaneous value of the pressure from numerical simulations of turbulence on tokamak edge: on the picture, the « hole » in the middle shows the plasma center excluded from the simulation. Top: without transport barrier; bottom : with barrier. Microscopic instabilities cannot be ruled out due to gradients of density, temperature and pressure. Those instabilities induce a micro-turbulence in which eddies (convention cells) increase drammatically transport of both matter and heat from the plasma centre towards the edge. This turbulent transport causes the plasma confinement to be spoiled. Nevertheless, Self-organisation of the turbulence can strongly improve the confinement by large scale flow! This self-organization mechanism is systematically use to reach an improved confinement regime by a thin layer located at the plasma edge where turbulence is strongly reduced. This layer is coined transport barrier. But unfortunately this layer is not stable bur relaxes quasi-periodically. In experiments for ITER scale, in order to maintain the heat flux associated to these relaxations within acceptable limits for the wall, control is required. Such a control has been experimentally demonstrated by using a magnetic perturbation brought from outside which create structures called magnetic islands.
Crédit : P. Beyer – Aix-Marseille Université
Heliomagnetism: Numerical simulation of heliomagnetism. (Top) the magnetic field lines in the solar corona, the background representing the radial component of the magnetic field close to the convective area. (Bottom) the longitudinal component of the magnetic field. Stars are big hot fluid spheres, spinning and showing turbulence with numerous convection phenomena and lying within a self-induced magnetic field.
Crédit : A.S.Brun – CEA/DSM/IRFU
Tokamak wall: In tokamaks, such as the Tore Supra facility in Cadarache (France) in the illustration, used to confine and heat plasmas by means of magnetic confinement, a toric chamber is used which is made of metal or carbon fibers able to withstand large surface density of thermal power.
Crit :P.Stroppa – CEA/DSM/Cadarache, 2009
Deuterium ice injector: Injector of ice pellets in Tore Supra tokamak. This injector is aimed at maintaining the plasma density during a few minutes, by throwing deuterium ice pellets in the plasma.
Crédit : P.Stroppa – CEA/DSM/Cadarache
X-ray source: By impinging a laser piulse on a target, a plasma is created and can be transformed into a source of extreme UV Exulite radiation used for photolithography purpose.
Crédit : P.Stroppa – CEA/DSM/Saclay, 10/2005
Superconducting coil: Within the context of magnetic fusion, one plasma confinment scenario is based upon a toric confinement via a magnetic field generated by non planar coils, according to the stellerator concept. On the picture, a superconducting coil of the W7X syterellator before its asssembly on the facility in Greiswald in Germany.
Crédit : CEA/DSM/Saclay/IRFU
Cooling of superconducting magnets: The HELIOS loop (Helium loop for high load smoothing) is developed to study how the variable thermal loads received by the the cryogenic systems of the future fusion reactors JT60-SA and ITER can be smoothed. For the japanese facility JT60-SA, the goal is to absorb around 12 kW peak power with a 6 kW average cooling power. The HELIOS facility runs on forced convection of supercritical Helium at 4.4 K temperature and under 5 bars pressure.
Credit : CEA/DSM/Grenoble/INAC, 2010
1 MeV neutral beam injector for ITER: 1-MeV Neutral Beam Injector (NBI) for Plasmas Heating and Current Drive. The extraction of negative ions from the plasma source dedicated to support the European experimental developments around the ITER-Beutral Beam Injector system has been simulated by the ONIX (Orsay Negative Ion eXtraction) code. ONIX code simulates the transport of the negative ions in the plasma source and their extraction by the external electric field. The plasma efficiently screens the extraction electric field and some negative ions are not extracted (on right), compared to the scenario without plasma (on left).
Crédit : LPGP / CNRS-UniversitParis-Sud
Modeling of laser-induced damage in optical materials by nanosecond pulses: High power laser consist of optical materials which may damage due to intense laser flux. In order to increase the damage resistance, physical processes responsible for laser-induced damage are studied. In particular, a sub-sonic absorption front is shown to be induced due to the coupling between defect formation and heat transfer. The evolution of the position of the absorption front with respect to time is shown in the figure.
G. Duchateau, M.D. Feit, and S.G. Demos, J. Appl. Phys 111, 093106 (2012)