Borisenko, L.

Borisenko, N.

Klir, D.

Malikova, A.

Rezak, K.

Rienecker, T.

Rosmej, O. N.

Schächinger, M.

Vergunova, G.

GSI Repository

GSITemplate2007 Supersonic radiation driven heat waves in foam target heated by X-rays O. N. Rosmej1, D. Klir2, K. Rezak2, M. Schächinger3, T. Rienecker3, G. Vergunova4, N. Borisenko4, L. Borisenko5,  A. Malikova5  1GSI, Darmstadt, Germany; 2 Czech Technical University in Prague; 3University of Frankfurt, Germany,  4 Lebedev Physical Institute, Moscow, Russia; 5Moscow State University, RussiaA combined hohlraum-target concept have been investi-gated in order to gain a high degree of plasma homogene-ity in experiment on the energy loss of heavy ions in ion-ized matter and approach plasma with a coupling parame-ter Γ~0.5-1. In this scheme, low density mm-thick foam layers were heated by means of X-rays generated in the gold hohlraum. The application of low density CHO-foam layers for plasma production has demonstrated a very high hydrodynamic stability of the created plasma and its uniformity [1]. A wide verity of diagnostic methods has been applied for measurements on the thermal wave propagation, plasma opacities and plasma self-radiation.           In Hydrodynamic 1-D calculations, 2 mg/cc cellu-lose triacetate C12H16O8  of 2 mm thickness was heated from the right side by an  X-ray flux with the Planckian spectral distribution at temperature of 30 eV and 10 ns duration (experimental conditions), see Fig.1. For radia-tion transport in the diffusion approximation C12H16O8 -opacities calculated in [,2] have been used.   Figure 1: Propagation of the heating front through a  2 mm thick CHO-foam in time window from 1 to 10 ns..  Depending on the hohlraum spectra and foam density two different scenarios of a foam target heating by X-rays can be realized. If the mean photon pass in plasma is shorter than a plasma size, optically thick case, target heating occurs step by step (Fig.1) via propagation of the radia-tion driven supersonic thermal waves. If created plasma is optically thin (low target density or more energetic spec-tra of photons due to higher hohlraum temperature) volu-metric heating takes place. Propagation of the radiation driven supersonic thermal waves has been obsurved experimentally using a pin-hole camera coupled to the 4-frame gated MCP (microchannel plate) [3] and imaging the CHO-foam at different times of the heating process. An exposition time for every frame, in experiment 3-5 ns, and time delay between two subsequent frames can be variied. Frig. 2 shows the geometry of the combined target (picture left), the MCP-cheep with four imaging areas (right) and a measured time  history of the heat-front propagating from the cylindrical hohlraum into the foam (center).    Figure 2: 2-D image of the foam region heated to plasma by hohlraum x-rays in the regime of supersonic radiation-driven heat waves, measured at different times.   The supersonic heat wave velocity  constTVm~~4ρ+ (1)  is a strong function of the plasma temperature T ( in our case m~3) and doesn’t depend on plasma density for hy-drodynamic stable plasmas (ρ=const). After analyses of the radiation front position at different times one comes up with the averaged over the exposition time heat wave velocities and corresponding plasma temperatures.  eVTscmxnsVeVTscmxnsVeVTscmxnsVeVTscmxnsV15~/6104.1)10(20~/6100.4)7(23~/6103.8)4(25~/7102.1)1(→=→=→=→=  In coming experiments this method will be applied for measurements of the plasma temperature in the time win-dow of ion-plasma interaction.  References  [1] G. Vergunova et a,lJournal of Russian Laser Re-search, Volume 31, Number 5, 2010  [2] N. Orlov et al, LPB 29 (2011), 69–80.   [3] D. Klir, PhD 2005, Czech Technical University in Prague GSI SCIENTIFIC REPORT 2012 PNI-IONS-EXP-29337

Supersonic radiation driven heat waves in foam target heated by X-rays

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Supersonic radiation driven heat waves in foam target heated by X-rays

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