Abstract
Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by a laser pulse at an intensity in the ...order of
$$10^{16}$$
10
16
W/cm
$$^2$$
2
. In this report we describe the results of an experiment carried out at PALS laser facility designed to investigate the origin of hot electrons in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering and Two Plasmon Decay instabilities, as well as of the generated hot electrons, suggest that Stimulated Raman Scattering is the dominant source of hot electrons via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that Two Plasmon Decay is damped at earlier times for higher plasma temperatures, accompanied by an earlier ignition of SRS. The identification of the predominant hot electron source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of hot electrons on the fuel ignition.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
Laser-driven shock waves in matter propagate with multiple kilometers per second and therefore require sources like a laser-driven backlighter, which emit the X-rays within picoseconds, to ...be able to capture sharp images. The small spatial extent of shocks in low-density materials pose challenges on the imaging setup. In this work, we present a design process for a single-shot X-ray phase-contrast imaging system geared towards these objects, consisting of a two-grating Talbot interferometer and a digital X-ray detector. This imaging system is optimized with respect to the detectable refraction angle of the X-rays induced by an object, which implies a high phase sensitivity. Therefore, an optimization parameter is defined that considers experimental constraints such as the limited number of photons, the required magnification, the size and spectrum of the X-ray source, and the visibility of the moiré fringes. In this way, a large parameter space is sampled and a suitable imaging system is chosen.
During a campaign at the PHELIX high-power laser facility a static test sample was imaged which is used to benchmark the optimization process and the imaging system under real conditions. The results show good agreement with the predicted performance, which demonstrates the reliability of the presented design process. Likewise, the process can be adapted to other types of laser experiments or X-ray sources and is not limited to the application presented here.
We present detailed characterization of graphene-like material obtained through microwave stimulated exfoliation of graphite oxide (GO). Properties of this material were studied by multiple ...techniques including, among others, X-ray photoelectron spectroscopy, mass-spectroscopy, infrared and Raman spectroscopy, scanning electron microscopy and broadband dielectric spectroscopy. Specific surface area and volume of microwave exfoliated graphite oxide reached 600 m super(2) g super(-1) and 6 cm super(3) g super(-1), respectively. It is shown that during such an explosive reduction process the sample emits CO sub(2), CO and H sub(2)O and, in some cases, SO sub(2) gases. The resulting reduced material exhibits IR spectra similar to that of graphite and a dc-conductivity of 0.12 S cm super(-1).
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IJS, KILJ, NUK, UL, UM, UPUK
In a recent experimental campaign, we used laser-accelerated relativistic hot electrons to ensure heating of thin titanium wire targets up to a warm dense matter (WDM) state EPL114, 45002 ...(2016)10.1209/0295-5075/114/45002. The WDM temperature profiles along several hundred microns of the wire were inferred by using spatially resolved X-ray emission spectroscopy looking at the Ti K
characteristic lines. A maximum temperature of ∼30 eV was reached. Our study extends this work by discussing the influence of the laser parameters on temperature profiles and the optimisation of WDM wire-based generation. The depth of wire heating may reach several hundreds of microns and it is proven to be strictly dependent on the laser intensity. At the same time, it is quantitatively demonstrated that the maximum WDM temperature doesn't appear to be sensitive to the laser intensity and mainly depends on the deposited laser energy considering ranges of 6×10
-6×10
W/cm
and 50-200 J.
Abstract
Both K-shell x-ray emission spectroscopy and fluorescence spectroscopy are well-accepted diagnostics for experimental studies of warm dense matter and hot dense matter (HDM). Until now, ...however, this diagnosis has been used for the study of dense matter with temperatures lower than 100 eV or with temperatures above 1 keV. In this work, we have demonstrated the possibility of using K-shell emission spectroscopy for an intermediate temperature range of 100s eV to study dense plasma. Here, we discuss an analysis of the HDM emission spectra of a solid-state copper with temperatures up to a few hundreds of electronvolts heated by laser-accelerated charged particles.
The light-by-light contribution from the axial-vector (AV) mesons exchanges to the muon anomalous magnetic moment is estimated in the framework of the nonlocal chiral quark model. The preliminary ...answer for contributions from
a
1
and
f
1
mesons to (g − 2)
µ
is 0.34 · 10
−11
and does not support the Melnikov-Vainshtein estimate 2.2 · 10
−11
.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We address an issue of measuring the parameters of an envolving laser-produced plasma commonly observable in high-energy density physics experiments. Available diagnostic equipment does not provide ...enough temporal, and often spatial, resolution to distinguish the signal coming from the region and timeframe of outmost interest, where deposited energy density reaches its maximum. In this paper, we propose and describe an approach that makes it possible to estimate the plasma parameters existing at the time of the main laser pulse arrival, as well as on later stages of plasma expansion. It is based on the analysis of X-ray spectral line profiles in multicharged ion spectra registered in simple time and spatially integrated mode. As an example, specific calculations were made for Ly
β
line of Al XIII and He
β
line of Al XII and can be used to diagnose aluminum plasmas with an electron temperature of 400–1000 eV, assuming that expanding plasma was homogeneous at every moment.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
At first, a granulated aerogel of graphene oxide was obtained, which was later reduced by hydrazine vapour. The reduced aerogel was characterized through elemental analysis, infrared (IR) and Raman ...spectroscopy, electron paramagnetic resonance (EPR), thermogravimetric analyses (TGA), voltammetry, and X-ray photoelectron spectroscopy (XPS). Furthermore, the reduced sample was found to contain approximately 3 wt.% of nitrogen, which was present in the aerogel in three states corresponding to the photoelectron peaks N1s with binding energies of 399.5, 401.3, and 403.6 eV. In the electroreduction of oxygen, an appreciable catalytic effect was observed for the sample under study, which resulted from reducing the overvoltage of the reaction by ~90 mV and changing the mechanism of reduction.
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•Graphene oxide aerogel was obtained in the form of granules at first time.•The granulated aerogel was reduced by hydrazine vapour.•The aerogel was investigated by elemental analysis, IR, EPR, TGA, voltammetry and XPS.•The reduced aerogel was tested in the reaction of electro-reduction of oxygen.•An appreciable catalytic effect is observed for the sample under study.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Studies of samples of graphite heat-shielding facing of the T-15MD tokamak chamber with stationary plasma loads in the PLM plasma device and high-power electron beams simulating loads during ELMs and ...transient processes were carried out. When the graphite facing samples were tested with plasma loads up to 2 MW/m
2
, their surface temperature reached more than 1200°C, the surface heating did not lead to cracking, a change in the relief, or significant erosion of the graphite surface. The plasma action led to the growth of a layer of highly porous carbon structures on the surface in the zone of contact with the plasma column. Irradiation of graphite with electron beams with a load of less than 12 MW/m
2
did not lead to changes in the surface structure; at a load exceeding 24 MW/m
2
, the processes of erosion and cracking of the surface along the grain boundaries began. At thermal cyclic loads exceeding 380 MW/m
2
, effects of significant erosion were observed with a rate of material removal from the graphite surface up to 175 μm/s. The conducted experimental studies and tests are considered as the basis for using the investigated type of graphite as the facing of heat-shielding components of the divertor and the first wall for operation in the T-15MD tokamak.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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