• V Arora

      Articles written in Pramana – Journal of Physics

    • Study of $2\omega$ and $3/2\omega$ harmonics in ultrashort high-intensity laser plasma interaction

      V Arora P A Naik J A Chakera R A Khan P D Gupta

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      An experimental study is presented on measurements of optical spectrum of the laser light scattered from solid surface irradiated by Ti:sapphire laser pulses up to an intensity of $1.2 \times 10^{18}$ W cm-2. The spectrum has well-defined peaks at wavelengths corresponding to $2\omega$ and $3/2\omega$ radiations. The spectral features vary with the laser intensity and show blue-shift with increasing laser intensity. At a constant laser fluence, the spectrum is red-shifted with increasing laser pulse duration. The observed results are explained in terms of the density scale length variation of the plasma and laser chirp.

    • A comparative study of the ionic keV X-ray line emission from plasma produced by the femtosecond, picosecond and nanosecond duration laser pulses

      V Arora P A Naik B S Rao P D Gupta

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      We report here an experimental study of the ionic keV X-ray line emission from magnesium plasma produced by laser pulses of three widely different pulse durations (FWHM) of 45 fs, 25 ps and 3 ns, at a constant laser fluence of $\sim 1.5 \times 10^4$ J cm-2. It is observed that the X-ray yield of the resonance lines from the higher ionization states such as H- and He-like ions decreases on decreasing the laser pulse duration, even though the peak laser intensities of $3.5 \times 10^{17}$ W cm-2 for the 45 fs pulses and $6.2 \times 10^{14}$ W cm-2 for the 25 ps pulses are much higher than $5 \times 10^{12}$ W cm-2 for the 3 ns laser pulse. The results were explained in terms of the ionization equilibrium time for different ionization states in the heated plasma. The study can be useful to make optimum choice of the laser pulse duration to produce short pulse intense X-ray line emission from the plasma and to get the knowledge of the degree of ionization in the plasma.

    • Spectral analysis of K-shell X-ray emission of magnesium plasma produced by ultrashort high-intensity laser pulse irradiation

      V Arora U Chakravarty Manoranjan P Singh J A Chakera P A Naik P D Gupta

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      Spectral analysis of K-shell X-ray emission of magnesium plasma, produced by laser pulses of 45 fs duration, focussed up to an intensity of ∼1018 W cm-2, is carried out. 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 code Prism-SPECT. It is observed that He-like resonance line emission occurs from the plasma region having sub-critical density, whereas K-𝛼 emission arises from the bulk solid heated to a temperature of 10 eV by the impact of hot electrons. K-𝛼 line from Be-like ions was used to estimate the hot electron temperature. A power law fit to the electron temperature showed a scaling of $I^{0.47}$ with laser intensity.

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