APPLIED PHYSICS

Diagnostics of plasma produced by femtosecond laser pulse impact upon targets with internal nanostructure

I. Yu. Skobelev, A. Ya. Faenov, S. V. Gasilov, T. A. Pikuz
Joint Institute for High Temperatures RAS, Moscow, Russia

S. A. Pikuz Jr.
Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia

A. I. Magunov
Prokhorov Institute for General Physics RAS, Moscow, Russia

A. S. Boldarev, V. A. Gasilov
Institute for Mathematical Modeling RAS, Moscow, Russia

   X-ray diagnostics was carried out for the interaction of femtosecond laser pulses (providing the intensity of 10¹⁶—10¹⁸ W/cm²) with CO₂ clusters and nanoscale particles of frozen water. The stage of cluster dissociation and plasma channel formation is studied, which is governing for the parameters of X-ray source and accelerated ion flows have been created in plasma. Spatially resolved X-ray spectra of Rydberg transitions in H- and He-like oxygen ions were used for diagnostics. t provides the measurements of plasma parameters on the timescale of 10 ps after the laser pulse begins to impact. We emphasize the role of trailing edge of laser pulse to keep the plasma temperature at a level of 100 eV during the stage of non-adiabatic cluster recession. The profiles and relative intensities of spectral lines were measured and analyzed by means of numerical simulation. It is allowed to mark out the fractions of “thermal” ions and that one accelerated up to tens of eV. Also electronic density and temperature in plasma were determined. The use of nanoscale water snow targets provides the sufficient increase in energy and quantity of accelerated He-like oxygen ions. The efficiency of H-like ions acceleration is not increased due to the time of its ionization exceeds the time of snow beads dissociation.

PACS: 52.25.-b

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