Enhancement in x-ray emission from laser plasmas produced from an alloy of gold and copper (Au 0.43+Cu 0.57 atomic composition) has been observed in a narrow spectral region of 1.5–3.9Å. X-ray emission is observed to be as high as six to nine times as compared to pure copper and 1.5 to 1.8 times as compared to pure gold targets. In these experiments, a single pulse from a Nd:glass laser (λ=1.06μm) having an energy up to 2J and 500ps pulse duration was used to obtain a focused intensity of 1013–1014W∕cm2 on the targets. The results are explained on the basis of enhanced group Rosseland opacity (Rosseland mean over the spectral range under consideration) for the Au–Cu alloy target as compared to either of the pure targets.
The damage mechanism induced by laser pulse of different duration in borosilicate glass widely used for making confinement geometry targets which are important for laser driven shock multiplication and elongation of pressure pulse, is studied. We measured the front and rear surface damage threshold of borosilicate glass and their dependency on laser parameters. In this paper, we also study the thermal effects on the damage diameters, generated at the time of plasma formation. These induced damage width, geometries and microstructure changes are measured and analyzed with optical microscope, scanning electron microscope and Raman spectroscopy. The results show that at low energies symmetrical damages are found and these damage width increases nonlinearly with laser intensity. The emitted optical spectrum during the process of breakdown is also investigated and is used for the characterization of emitted plasma such as plasma temperature and free electron density. Optical emission lines from Si I at 500 nm, Si II at 385nm and Si III at 455 nm are taken for the temperature calculations.
Optimization of a laser produced plasma (LPP) X-ray source has been performed by analyzing K-shell emission spectra of Al plasma at a laser intensity of 10 13-10 14 W/cm 2. The effect of varying the laser intensity on the emissivity of the K-shell resonance lines is studied and found to follow a power law, E α I α with α=2.2, 2.3, 2.4 for He β , He γ , He δ respectively. The emission of these resonance lines has been found to be heavily anisotropic. A Python language based code has been developed to generate an intensity profile of K-shell spectral lines from the raw data. In theoretical calculations, the temperature is estimated by taking the ratio of the Li-like satellite (1s 2 2p-1s2p3p) and the He β (1s 2-1s3p) resonance line and the ratio of the He-like satellite (1s2p-2p 2) and the Ly α (1s-2p) resonance line. To determine the plasma density, stark broadening of the Ly β spectral line is used. Simulation was carried out using the FLYCHK code to generate a synthetic emission spectrum. The results obtained by FLYCHK are T e =160 eV, T h =1 keV, f=0.008, n e =5 x 10 20 cm-3 and the analytical model resulted T e =260-419 eV and n e =3x10 20 cm-3 .
Abstract. The idea of direct-indirect target is experimentally tested with planar targets from LPI made of low-density metal foam (nanosnow) or of nanoparticles (30%) in plastic aerogels. The laser experiments in BARC have shown that compared to plain targets the foams of/with nanoparticles demonstrate: 1) better x-ray emissivity ; 2) smoother energy distribution over the target surface; 3) material flow from low-density wall being slower and more uniform; 4) active transverse energy transport over the target plane. These properties could be useful for hohlraums and direct-indirect concept. DIRECT-INDIRECT TARGETS SCHEMESPlasma from foams has been studied for decades [1 and ref.], but Au and Bi are not studied enough. The design of direct-indirect target using a 0.25 m-thick outer gold shell was suggested in [2]. The advantage of this design was in the easy process of laser focusing. Disadvantages, such as low x-ray efficiency, necessity of short laser pulse duration and high velocity of Au-plasma were consequent.Another design shown in Fig. 1 was proposed by Yu.A. Merkul'ev [3]. This is a target with Au-lowdensity converter which allows easy laser focusing and long laser pulse. As the result, the Au-plasma motion is slower, but the x-ray efficiency is still low. One more design, shown in Fig. 2, was proposed in [4]. The target with low-density absorber-converter was invented for 2 MJ 5 ns laser pulses. Easy laser focusing, possibility of long laser pulse and high efficiency for 0.53 m wavelength are among its advantages. However with mixed interaction (both x-ray and thermal) taking place in this case, the cryogenic DT layer is difficult to keep.M.D. Rosen and J.H. Hammer proved [5], and observed experimentally [6], that x-ray temperature in gold low-density converter is higher than in ordinary Au-converter of indirect-drive targets.Au low-density converters of heavy ions energy to x-rays should have their density varying from 10 mg/cm 3 to 400 mg/cm 3 [7]. Unlike polymers, metal foams are heat conductive and allow cryo-layer formation in fuel capsule of the target by rapid cooling (quench).Low-density Au is being developed in LLNL and GA, USA, as well as in LPI (Russia). METAL FOAMS PRODUCTION FOR DIFFERENT DENSITIESNo universal fabrication methods exist for high-Z low-density metals in a wide density range. Various technology routes of metal low-density layers are realized for
Experiments were performed with a 15 J/500 ps Nd:glass laser (λ = 1064 nm) focussed to an intensity >10 14 W/cm 2 . X-ray emissions from carbon foam and 5% Pt-doped carbon foam of density 150-300 mg/cc were compared with that of the solid carbon targets. The thickness of the carbon foam was 15 μm on a graphite substrate. X-ray emission was measured using semiconductor X-ray diodes covered with various filters having transmissions in different X-ray spectral ranges. It covered X-ray spectrum of 0.8-8.5 keV range. The X-ray emission in the soft X-ray region was observed to increase to about 1.8 times and 2.3 times in carbon foam and Pt-doped foam, respectively with respect to solid carbon. In hard X-rays, there was no measurable difference amongst the carbon foam, Pt-doped carbon foam and solid carbon. Scanning electron microscope (SEM) analysis demonstrates that foam targets smoothens the crater formed by the laser irradiation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.