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77DIAGNOSTICS OF WARM DENSE MATTER BY HIGH-RESOLUTION X-RAY SPECTROSCOPY OF HOLLOW IONS.
S.A. Pikuz Jr.1,2, A.Ya. Faenov1,3, I.Yu. Skobelev1,2, T.A. Pikuz1,3, M.A.
Alkhimova1,2, R. Kodama3, V.E. Fortov1.
1 Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow,
Russia
National Research Nuclear University MEPhI, Moscow, Russia
3
Institute for Academic Initiatives, Osaka University, Suita, Osaka, Japan
During the past years many observations have been done on such exotic atomic objects as hollow ions, i.e. ions with empty internal electron shells and populated outer ones. X-ray spectra emitted by hollow ions have been obtained in the interaction of ultrashort high-power laser pulses with condensed targets (solid targets, clusters) and even with dense gases, as well as in experiments with FEL lasers. The excitation of hollow ions is especially efficient in high-density plasmas and permits developing X-ray spectral methods for ultrahigh-density plasma diagnostics, particular, for diagnostic of warm dense matter and non-ideal plasmas. Indeed, hollow ions spectra are not sensitive to the non-ideality effects in plasma because they are emitted in the electron transitions between deep-lying inner shells of ions. Thus, hollow ion X-ray spectra are considered as powerful diagnostic tool to study dense high-temperature plasma created by ultra-intense laser fields and charged particle beams.
The overview of our recent results in application of hollow atom spectroscopy to measure the parameters of various types of plasmas is given. It is shown as hollow ion spectra features are sensitive to the mechanisms of plasma excitation occurs in the interaction of ultra-intense pico- and femto-second laser pulses with bulk solid, foiled solid, gas and gas cluster targets. Particularly, the plasma created by petawatt laser pulses in solids is considered when the radiation kinetics is dominated by extremely intense X-ray radiation source. As well, the cases of the plasma of high pressure gas targets with the enhanced role of charge-exchange processes, and the solid-density plasma under the impact of fast charged particles are discussed.
