Engineering topics

Gupta, N K

Publications and source records attributed to Gupta, N K.

3 records

DOE OSTI2012

Molecular dynamic studies on anisotropic explosion of laser irradiated Xe cluster

A three dimensional molecular dynamic model is used to investigate the dynamics of Xe clusters of various radii irradiated by laser of moderate intensities ({approx}10{sup 14}-10{sup 16}W/cm{sup 2}). The FWHM pulse duration of the laser is varied from few laser cycles to hundreds of femtosecond. For cluster of radius 50 A irradiated by a laser of 170 fs pulse duration, it is observed that ion yield is more along the direction of laser polarization than perpendicular to it. This trend reverses (more ions are emitted along the direction perpendicular to laser polarization than parallel to it) when laser pulses of few cycles are used. This reversal of anisotropy is explained on the basis of spatial shielding of ions due to the oscillating inner electron cloud along direction of laser electric field. The nature of anisotropy remains same with variations in laser intensity and cluster size.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Molecular dynamic simulation for laser-cluster interaction

A three dimensional relativistic molecular dynamic model for studying the laser interaction with atomic clusters is presented. The model is used to simulate the interaction dynamics of deuterium, argon, and xenon clusters when irradiated by the short and high intensity laser pulses. The interaction of 82 A argon cluster by 100 fs, 806 nm laser pulse with the peak intensity of 8 x 10{sup 15} W/cm{sup 2} is studied and compared with the experimental results. The maximum ion energy in this case is found to be about 200 keV. Ion energies along and perpendicular to laser polarization direction is calculated and asymmetry along laser polarization direction is detected which is further explained on the basis of charge flipping model. The effect of cluster density on the energetics of the laser-cluster interaction is also being studied, which provides a qualitative understanding of the presence of optimum cluster size for maximum ion energies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2011

Generation of ultraintense proton beams by multi-ps circularly polarized laser pulses for fast ignition-related applications

A scheme of generation of ultraintense proton beams relevant for proton fast ignition (PFI) which employs multi-ps, circularly polarized laser pulse irradiating a thick ({>=} 10 {mu}m) H-rich target is proposed and examined using one-dimensional particle-in cell-simulations. It is shown that a 5-ps laser pulse of intensity {approx} (2-5) x 10{sup 20}W/cm{sup 2} irradiating the target of the areal proton density {approx} 2 x 10{sup 20}cm{sup -2} can produce - with a high energetic efficiency - a proton beam (plasma block) of parameters (intensity, energy fluence, pulse duration, proton energy spectrum) close to those required for PFI. At a fixed total laser energy, the proton beam parameters can be controlled and fitted to the PFI requirements by changing the laser intensity (energy fluence) and/or the target thickness as well as by using a shaped (curved) target inserted into a guiding cone.

43 PARTICLE ACCELERATORS↗