High Energy electron and proton acceleration by circularly polarized laser pulse from near critical density hydrogen gas target

We demonstrate in this research the quasi-monoenergetic electron and proton acceleration through three dimensional particle-in-cell simulations of short petawatt circular polarized laser pulse interactions with near critical density hydrogen target. We numerically show that under controlled choice of laser and target parameters, the high energy electrons and protons can be illustrated in experiment at advanced high power laser facilities eg ELI - ALPS. We detailed the microphysics involved in the acceleration mechanism, which required investigating the role of plasma density gradients, plasma density, and target thickness. The role of selfgenerated plasma electric and magnetic fields is depicted on proton energy and density distribution. We numerically investigate here the laser driven proton acceleration where energetic protons with energies more than 200 MeV and charge in excess of 10 nC and conversion efficiency more than 6 percent (which implies 2.4 J proton beam out of the 40 J incident laser energy). Additionally and interestingly, we show from simulation study first time the quasi-monoenergetic ring shaped electron beam driven by circularly polarised laser which may prove useful for plasma based-based X-ray source and collimation of positron beam

Self-organized structures in soft confined thin films

We present a mini-review of our recent work on spontaneous, self-organized creation of mesostructures in soft materials like thin films of polymeric liquids and elastic solids. These very small scale, highly confined systems are inherently unstable and thus self-organize into ordered structures which can be exploited for MEMS, sensors, opto-electronic devices and a host of other nanotechnology applications. In particular, mesomechanics requires incorporation of intermolecular interactions and surface tension forces, which are usually inconsequential in classical macroscale mechanics. We point to some experiments and quasi-continuum simulations of self-organized structures in thin soft films which are germane not only to nanotechnology, but also to a spectrum of classical issues such as adhesion/debonding, wetting, coatings, tribology and membranes

High-Entropy Alloys for Micro- and Nanojoining Applications

The aim of this chapter is to provide a basic understanding of the metal-ceramic joints and high-entropy alloy (HEA) research in microjoining applications. We will first overview the issues in metal-ceramic brazing and solutions to overcome those issues using various fillers. Various approaches are available for joining ceramic to metallic materials. One approach will be to look for brazing alloys with the so-called high-entropy characteristics which exhibit a solid solution phase. The conventional alloy design and arc melting, Bridgman solidification, and advanced powder metallurgy techniques will be studied, including high-energy ball milling (HEBM) for the mechanical alloying process, and hot-press and spark plasma sintering (SPS) techniques are utilized for improved densification and phase transformation. We also summarize the various thermodynamic relations to obtain the high-entropy phase and present future possibilities of high-entropy alloys in microjoining research at the later stage of this chapter

SUPER ORTHOGONAL SPACE TIME TRELLIS CODES OVER NAKAGAMI FADING MODEL

Performance evaluation of super orthogonal space-time trellis codes for non-frequency selective fading channels & frequency selective fading channels. The analysis is done in presence of fast fading, block fading and quasi-static fading in Rayleigh, and Nakhagami fast fading channels along with comparison. While providing full diversity and full rate, the structure of our new codes allows an increase in the coding gain. Not only does our new SOSTTC outperform the space-time trellis codes in the literature, but it also provides a systematic method for designing space time trellis codes at different rates and for different trellises. Since we have used orthogonal designs as the building blocks in our new SOSTTCs, the complexity of the decoding remains low while full diversity is guaranteed. Codes operating at different rates, up to the highest theoretically possible rate, for different number of states, can be designed by using our optimal set partitioning. In general, new SOSTTCs can provide a tradeoff between rate and coding gain while achieving full diversity