X-ray spectroscopy of hot dense plasmas

The research in the field of x-ray spectroscopic diagnosis of hot dense plasma is based primarily on high-resolution spectrometers [1, 2] developed in the Institute of Physics ASCR, v.v.i. Current efforts concentrate to two main areas.

Interaction of high–temperature plasma jets with surfaces of solid materials (generally known as the plasma-wall interaction, PWI) is extensively studied in the context of a material research for development of future fusion reactors. Pilot experiments performed at the PALS laser facility [3, 4] were dedicated to investigation of collisional, interpenetration and stagnation plasma zones close to the surfaces of the plasma-exposed secondary targets. Precisely measured x-ray emission spectra of H- and He-like ions were interpreted by trapping, collision and thermalization of the incident plasma jets with counter–propagating matter ejected from the wall. For the first time, the ion deceleration profiles were measured via Doppler shifts of optically thin satellite transitions [5]. Successful experiments initiated a new research project directed at investigation of transient phenomena occurring near the surface of plasma–exposed materials.

The second area of x-ray spectroscopic studies contributes to identification and quantitative characterization of processes accompanying evolution of the intermediate and strongly coupled plasmas. The fine structure observed in spectral line profiles and their satellites is interpreted in terms of the radiative transfer effects [6], charge–exchange phenomena [7] including charge–exchange–driven cascading of single– and double–excited ionic states [8], presence and distribution of strong electric fields connected with the collective motion of the plasma particles [9, 10] or with the externally introduced single-frequency electromagnetic (laser) fields [11].

The univocal identification of the latter effect opens a broad space for new types of experiments: the mapping of the electric field distribution, the investigation of the laser field penetration into the plasma, and the characterization of local Langmuir oscillations as a result of density fluctuations. In this respect, precise spectroscopic experiments characterizing environmental plasma conditions (ion and electron temperature, density, ion velocity and charge distribution) provide complex new information on strongly correlated plasmas and contribute to their practical applications.

References:
[1] Renner O. et al: Rev. Sci. Instr. 68, 2393 (1997); 70, 3025 (1999); 75, 4569 (2004).
[2] Renner O., Uschmann I., Förster E.: Diagnostic potential of advanced x-ray spectroscopy for investigation of hot dense plasmas. Laser Part. Beams 22 , 25 (2004).
[3] Rosmej F.B., Lisitsa V.S., Schott R., Dalimier E., Riley D., Delserieys A., Renner O., Krousky E.: Charge exchange driven X-ray emission from highly ionized plasma jets. Europhys. Lett. 76, 815 (2006).
[4] Renner O., Adámek P., Dalimier E., Delserieys A., Krousky E., Limpouch J., Liska R., Riley D., Rosmej F.B., Schott R.: Spectroscopic characterization of ion collisions and trapping at laser irradiated double-foil targets. High Energy Density Phys. 3, 211 (2007).
[5] Renner O., Liska R., Rosmej F.B.: Laser–produced plasma–wall interaction. Laser and Particle Beams, 27, 725 (2009).
[6] Renner O., Kerr F.M., Wolfrum E., Hawreliak J., Chambers D.M., Rose S.J., Wark J.S., Scott H.A., Patel P.: Radiation transfer effects on the spectra of laser-generated plasmas. Phys. Rev. Lett. 96, 185002 (2006).
[7] Dalimier E., Oks E., Renner O., Schott R: Experimental determination of rate coefficients of charge exchange from x-dips in laser-produced plasmas. J. Phys. B: At. Mol. Opt. Phys. 40, 909 (2007).
[8] Rosmej F.B., Lisitsa V.S., Schott R., Dalimier E., Riley D., Delserieys A., Renner O., Krousky E.: Charge exchange driven X-ray emission from highly ionized plasma jets. Europhys. Lett. 76, 815 (2006).
[9] Renner O., Peyrusse O., Sondhauss P., Förster E.: Indication of single-frequency electric fields in hydrogenic aluminum emission from laser-produced plasma. J. Phys. B: At. Mol. Opt. Phys. 33, L151 (2000).
[10] Krasniqi F., Renner O., Dalimier E., Dufour E., Schott R., Förster E.: Possibility of plasma density diagnostics using Langmuir-wave-caused dips observed in dense laser plasmas. Eur. Phys. J. D 39, 439 (2006).
[11] Sauvan P., Dalimier E., Oks E., Renner O., Weber S., Riconda C.: Spectroscopic diagnostic of plasma interaction with an external oscillatory field. J. Phys. B: At. Mol. Opt. Phys. 42, 195001 (2009).