Gaurav Mishra

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 × 1015 W/cm2 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.

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 μm) H-rich target is p ...

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 (∼1014−1016W/cm2). 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.

Effect of laser pulse time profile on its absorption by argon clusters

The interaction of medium sized Argon clusters (30 angstrom) with high-intensity femtosecond laser pulses (806 nm, 8 x 10(16) W/cm(2)) of durations ranging from 10 fs to 120 fs have been studied us ...

Laser induced neutron production by explosion of the deuterium clusters

The high energy deuterium ions serve as compact source of neutrons when fused with either deuterium or tritium atoms. In view of this, the explosion of the deuterium clusters under the influence of the laser pulse with intensity ranging from 1015 to 1019 W/cm2 is being studied along with the effect of the cluster radius and inter-cluster distance. The objective of this article is to study the efficiency of the deuterium cluster as a compact source of neutrons under various laser and cluster parameters. It is being observed that the cluster density (number of clusters per unit volume) is quite important to gain high neutron yield.

Dynamics of Atomic Clusters Under Intense Femtosecond Laser Pulses

This chapter presents a review of theoretical modelling of intense ultrashort laser interaction with atomic clusters. We start with a brief description of interaction of laser with gas atoms and solid targets. This is followed by a general introduction of the non-linear, non-perturbative interaction of strong laser fields with atomic clusters. Various theoretical models are presented to explain the rich features observed in laser irradiated clusters. A molecular dynamic model developed by us to study laser-cluster interaction is briefly described.Various problems of contemporary interest like anisotropic emission of ions from argon and xenon clusters, effect of carrier-envelope phase on ionization dynamic of xenon clusters, neutron emission from deuterium clusters etc. are investigated and main results of these studies are presented.

Carrier?envelope phase effects on ionization dynamics of atomic clusters irradiated by intense laser pulses of a few cycles

A three-dimensional molecular dynamic approach is employed to investigate the ionization dynamics of small Xe400 clusters irradiated by intense lasers (I = 1016W cm−2) in the near infrared wavelength region (λ = 800 nm). The pulse duration of the incident laser is varied from a few cycles (τ = 2T0 with T0 as one laser time cycle) to many cycles (τ = 8T0). In the case of pulse durations of a few cycles, the carrier–envelope (CE) phase of the incident laser electric field is found to be an important parameter that affects the ionization dynamics of Xe clusters. The fractions of various ionized Xe species are observed to be different for the two values of the CE phases (ϕ = 0 and ϕ = π/2) in the case of the shorter laser pulse duration of τ = 2T0. The nature of the instantaneous electric field (the rising or falling edge of the field) at the time of birth of the electron due to ionization decides the extent of ionization. The difference in time-evolution of the electric field for the two values of the CE phase leads to an observable disparity in the yield of various ionic species. For the case of a pulse duration of many cycles (τ = 8T0), these differences average out and we do not observe any change in the yield of various ionic species for the two values of the CE phase.