Bagnoud, V.

Basko, M. M.

Frank, A.

Grushin, A.

Hannachi, F.

Maruhn, J.

Novikov, V. G.

Tauschwitz, An.

GSI Repository

High-temperature plasma of Ge generated by the PHELIX laser ∗M. M. Basko1,2,3, J. Maruhn1,2, An. Tauschwitz1,2, A. Grushin3, V. G. Novikov3, A. Frank4,V. Bagnoud5, and F. Hannachi61EMMI-GSI, Darmstadt, Germany; 2University of Frankfurt, Germany; 3KIAM, Moscow, Russia ; 4Helmholtz-InstitutJena, Germany; 5GSI, Darmstadt, Germany; 6CENBG, FranceCertain nuclear transitions, accompanied by release oflarge amounts of energy, can be induced by appropriateatomic resonances. One potential candidate is an iso-meric state of 84Rb, whose γ-decay could be initiated byresonant ns → 2s transitions in strongly (zion > 27)ionized Rb atoms [1]. The required degree of ioniza-tion could be achieved by heating the medium, where the84Rb isomers are created, with the PHELIX laser at GSI.Since the Rb isomers are expected to be created in the76Ge(12C,p3n)84Rb reaction, i.e. by irradiating Ge with acarbon beam, it is the Ge plasma where one should demon-strate the ability to achieve the necessary temperatures un-der laser irradiation.Here we present the results of RALEF-2D [2] simula-tions of a 4 μm thick Ge foil, irradiated normally by aλ = 532 nm laser pulse of 150 J over a focal spot of ra-dius rf = 100 μm; the 1.4-ns long pulse was ramped with0.2-ns linear rise and fall intervals. As a preliminary step,spectral opacities and the equation of state of Ge in theapproximation of local thermodynamic equilibrium (LTE)were generated with the THERMOS code [3]. The RALEFruns were performed in the newly developed axial rz modeof the radiation transport, which was treated with 22 spec-tral groups and the S12 angular quadrature.laser beamFigure 1: 2D color contour plot of Ge-plasma temperature(in keV) at t = 0.8 ns.The calculated 2D temperature distribution in the Geplasma shortly after the middle of the laser pulse (t =0.8 ns) is displayed in Fig. 1. The corresponding 1D pro-files along the laser-beam axis are shown in Fig. 2. Thelaser heated plasma consists of two distinct zones: a low-density hot corona behind the critical surface, whose tem-perature reaches Tmax ≈ 1.3 keV, and a radiation-driven∗The project is a collaboration between CENBG, CEA DAM, GSI,University of Frankfurt and KIAM and is supported by the Extreme MatterInstitute EMMI.heat wave before the critical surface with a relatively highdensity of ρ ≈ 0.1–0.2 g/cc, where the matter and radia-tion temperatures are practically equal and lie in the rangeT ≈ Tr ≈ 100–150 eV. The whole structure is dominatedby x-ray energy transport: our simulation indicates thatabout 70% of the absorbed laser energy escapes the targetin the form of keV-range x-rays. The calculated time- andspace-integrated emission spectrum (in the direction oppo-site to the laser beam) is shown in Fig. 3.-0.04 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.120510152025303540ionization degree  zionz (mm) zionzionρ0.010.11 temperature (keV), density (g/cc) density T matter T radiationFigure 2: Profiles along the laser-beam axis at t = 0.8 ns.0.5 1.0 1.5 2.0 2.5 3.0 3.510-710-610-510-410-310-2E ν  [104  J/(ster keV)]hν (keV)Figure 3: Time- and space-integrated emission spectrum.Of principal interest for studying the nuclear transitionsin Rb would be a narrow ablation front, where the mat-ter temperature jumps from T <∼ 0.2 keV to T > 1 keV.It is within this layer that, similar to Ge, the admixtureRb atoms should undergo sharp increase in their ionizationdegree from zion ≈ 15–20 up to a helium-like state withzion = 35 assuming LTE.References[1] F. Gobet et al., Nucl.Instr. and Meth. A 653 (2011) 80.[2] M. M. Basko et al., GSI Report 2010-1 , p. 410.[3] A.F. Nikiforov, V.G. Novikov, V.B. Uvarov, Quantum-statistical models of hot dense matter: methods for compu-tation of opacity and equation of state, Birkha¨user, 2005.PNI-IONS-THEORY-08 GSI SCIENTIFIC REPORT 2012354 FAIR@GSI

High-temperature plasma of Ge generated by the PHELIX laser

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High-temperature plasma of Ge generated by the PHELIX laser

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