arXiv subjects

P. P. Rajeev

Publications and source records attributed to P. P. Rajeev.

22 records · Page 2Linked to original sources

arXiv2002

Metal nanoplasmas as bright sources of hard x-ray pulses

We demonstrate a 13-fold increase in hard x-ray bremsstrahlung (10 - 200 keV) emitted by a copper plasma created by 100 fs, 806 nm pulses at $10^{14}-10^{15}$ Wcm$^{-2}$. This enhancement is achieved by roughening the target surface with copper nanoparticles of ~15 nm size. A simple model that invokes local field modifications by surface plasmon excitation and `lightning rod' effects explains the observed enhancement quantitatively and provides pointers to the design of structured surfaces for maximizing the emission.

physics.plasm-ph↗

arXiv2002

Polarization independent hot electron production from modulated solid surfaces

We present measurements of hard x-rays in the 50-300 keV range from copper plasmas produced by 100 fs, 806 nm laser pulses at a peak intensity ~ 1016 W cm-2. Surface roughness, even at the tens of nanometer level, is shown to influence the emission characteristics. The enhanced emission from rough targets is attributed to depolarization of light as well as extra absorption facilitated by the surface irregularities.

physics.plasm-ph↗

arXiv2002

Laser-Generated Ultrashort Multi-Megagauss Magnetic Pulses in Plasmas

We demonstrate ultrashort (6 ps), multi-Megagauss (27 MG) magnetic pulses generated upon interaction of an intense laser pulse (10^{16} Wcm^-2, 100 fs) with a solid target. The temporal evolution of these giant fields generated near the high density critical layer is obtained with the highest resolution reported so far. Particle-in-cell simulations and phenomenological modeling is used to explain the results. The first direct observations of anomalously rapid damping of plasma shielding currents produced in response to the hot electron currents penetrating the bulk plasma are presented.

physics.plasm-ph↗

arXiv2002

Role of surface roughness in hard x-ray emission from femtosecond laser produced copper plasmas

The hard x-ray emission in the energy range of 30-300 keV from copper plasmas produced by 100 fs, 806 nm laser pulses at intensities in the range of 10$^{15}-10^{16}$ W cm$^{-2}$ is investigated. We demonstrate that surface roughness of the targets overrides the role of polarization state in the coupling of light to the plasma. We further show that surface roughness has a significant role in enhancing the x-ray emission in the above mentioned energy range.

physics.plasm-ph↗