A review of low density porous materials used in laser plasma experiments

金沢大学先端科学・社会共創推進機構This review describes and categorizes the synthesis and properties of low density porous materials, which are commonly referred to as foams and are utilized for laser plasma experiments. By focusing a high-power laser on a small target composed of these materials, high energy and density states can be produced. In the past decade or so, various new target fabrication techniques have been developed by many laboratories that use high energy lasers and consequently, many publications and reviews followed these developments. However, the emphasis so far has been on targets that did not utilize low density porous materials. This review therefore, attempts to redress this balance and endeavors to review low density materials used in laser plasma experiments in recent years. The emphasis of this review will be on aspects of low density materials that are of relevance to high energy laser plasma experiments. Aspects of low density materials such as densities, elemental compositions, macroscopic structures, nanostructures, and characterization of these materials will be covered. Also, there will be a brief mention of how these aspects affect the results in laser plasma experiments and the constrictions that these requirements put on the fabrication of low density materials relevant to this field. This review is written from the chemists\u27 point of view to aid physicists and the new comers to this field. © 2018 Author(s).Embargo Period 12 month

Formation and evolution of post-solitons following a high intensity laser-plasma interaction with a low-density foam target

The formation and evolution of post-solitons has been discussed for quite some time both analytically and through the use of particle-in-cell (PIC) codes. It is however only recently that they have been directly observed in laser-plasma experiments. Relativistic electromagnetic (EM) solitons are localised structures that can occur in collisionless plasmas. They consist of a low-frequency EM wave trapped in a low electron number-density cavity surrounded by a shell with a higher electron number-density. Here we describe the results of an experiment in which a 100 TW Ti:sapphire laser (30 fs, 800 nm) irradiates a 0:03 gcm^-3 TMPTA foam target with a focused intensity I_l = 9:5x10^17 Wcm^-2. A third harmonic (lambda_probe ~ 266 nm) probe is employed to diagnose plasma motion for 25 ps after the main pulse interaction via Doppler-Spectroscopy. Both radiation-hydrodynamics and 2-D PIC simulations are performed to aid in the interpretation of the experimental results. We show that the rapid motion of the probe critical-surface observed in the experiment might be a signature of post-soliton wall motion

<strong>Charcterisation of pore size of TMPTA polymer foam by pulsed sputter coating andSEM analysis</strong>

This paper describes the production and characterisation of low density polymeric foams used by the Atomic Weapons Establishment (AWE) Plasma Physics programme. Production and preparation of such foam samples for characterisation by scanning electron microscopy (SEM) are described. Examining non-conductive low density foam specimens by conventional SEM requires sputter coating with a very thin layer of gold to prevent overcharging the sample. This paper describes modifications to this process, which have illustrated the destructive effects of the sputtering process on these foams. Optimum conditions to minimise foam damage during sputtering have been determined. Low-vacuum SEM in conjunction with a charge cascade detector which enables non-conductive samples to be directly imaged has been used to reduce the damage to fragile foams. These results are compared with those taken of samples coated under optimum sputtering conditions. Using sputter coating time trials and an absorbed electron (AE) detector, it was revealed that the pore size of TMPTA foam was in the region of 0.1 mu m, i.e. an order of magnitude lower than reported previously. Some proposed damage mechanisms are also discussed. (c) 2006 Springer Science + Business Media, Inc.</p

Shock dynamics and shock collision in foam layered targets

Abstract We present an experimental study of the dynamics of shocks generated by the interaction of a double-spot laser in different kinds of targets: simple aluminum foils and foam–aluminum layered targets. The experiment was performed using the Prague PALS iodine laser working at 0.44 μm wavelength and irradiance of a few 1015 W/cm2. Shock breakouts for pure Al and for foam-Al targets have been recorded using time-resolved self-emission diagnostics. Experimental results have been compared with numerical simulations. The shocks originating from two spots move forward and expand radially in the targets, finally colliding in the intermediate region and producing a very strong increase in pressure. This is particularly clear for the case of foam layered targets, where we also observed a delay of shock breakout and a spatial redistribution of the pressure. The influence of the foam layer doped with high-Z (Au) nanoparticles on the shock dynamics was also studied