Laser Plasma Section

High energy x-ray generation and fast electron transport in thin foils and wires

X-ray Spectroscopic Studies of Plasma Produced by Intense Laser Beams

The spectral and temporal features of x-ray emission from high temperature plasma of moderate–Z material produced at intensities > 1015 W cm-2 using sub-ps duration laser pulses depend on the plasma parameters viz. electron temperature, plasma density, average ionization stage, and radiative opacity of the plasma at high temperature. The x-ray spectroscopic study of plasma produced by intense laser beams is the most suitable method to study the various processes occurring in the plasma.

High resolution x-ray spectrum of Mg plasma
Figure 1: High resolution x-ray spectrum of Mg plasma produced by 45 fs duration laser pulses focused at an intensity of 4x1017 W-cm-2.

Figure 1 shows a typical K–shell x-ray spectrum of Mg plasma produced by high contrast ultra-short high intensity laser pulses. The x-ray spectrum has a strong He-α line, with the satellites of the different ions from O-like to Li- like, limited by the K-α line from un-ionized Mg atoms. The plasma conditions prevalent during the emission of x-ray spectrum were identified by comparing the experimental spectra with the synthetic spectra generated using the spectroscopic analysis code PrismSPECT. The experimental result was compared with the best fit spectrum. It shows that the plasma under consideration has sharp density and temperature gradients. The spectral region around the He-α line mainly comes from the hot under dense plasma and that around K-α arises from the bulk dense region. Ionic line emission arises from the plasma with a spatially and temporally averaged value of the electron temperature of ~100 -200 eV and electron density of ~ 5.4 ×1020 cm-3

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