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Enhanced coupling of laser energy to the target particles is a fundamental issue in laser-plasma interactions. Here the authors demonstrate increased photon absorption leading into higher laser to electron and proton energy transfer through the interference of multiple coherent beamlets.

In this work we report the successful implementation of plasma mirror (PM) technology on an LFEX laser facility at the Institute of Laser Engineering, Osaka University. The LFEX laser pulse was successfully refocused at the target chamber center (TCC) by means of a spherical plasma mirror, resulting in 5  ×  1018 W cm−2 laser intensity, with 45% reflectivity at a laser flux of about 90 J cm−2 on the PM. Experimental results show stable focusing and pointing of the LFEX pulse after PM refocusing. The contrast improvement was demonstrated by both cooler fast electron slope temperature distribution as well as by the ability to shoot sub-µm plastic foils obtaining proton beams with maximum energy exceeding 20 MeV. Experimental results are qualitatively reproduced by 2D particle in cell simulations. [ABSTRACT FROM AUTHOR]

The study of fast electron spectrum optimization by suppression of preformed plasma in fast ignition targets is presented in this work. Integrated fast-electron spectra for electron energies below 3 MeV—the energy range responsible for core heating—are compared for different preformed plasma conditions. The pulse contrast (the ratio of peak-to-pedestal laser intensities) is compared for 108, 109 and 1011 conditions at constant laser energy (~500 J), pulse duration (2 ps), spot size (30% encircled energy on 50 µm diameter) and laser intensity (around 1  ×  1019 W cm−2). The best electron spectrum optimization, consisting of maximized electron number for energies below 3 MeV was obtained with 14 µm thick cone targets. The energy coupling efficiency from heating laser to core plasma, assuming typical core plasma parameters, was estimated to be 2%, although 0.37% was obtained with previous conditions with poor pulse contrast and a 7 µm thick cone target. [ABSTRACT FROM AUTHOR]

Increasing the laser energy absorption into energetic particle beams represents a longstanding quest in intense laser-plasma physics. During the interaction with matter, part of the laser energy is converted into relativistic electron beams, which are the origin of secondary sources of energetic ions, γ-rays and neutrons. Here we experimentally demonstrate that using multiple coherent laser beamlets spatially and temporally overlapped, thus producing an interference pattern in the laser focus, significantly improves the laser energy conversion efficiency into hot electrons, compared to one beam with the same energy and nominal intensity as the four beamlets combined. Two-dimensional particle-in-cell simulations support the experimental results, suggesting that beamlet interference pattern induces a periodical shaping of the critical density, ultimately playing a key-role in enhancing the laser-to-electron energy conversion efficiency. This method is rather insensitive to laser pulse contrast and duration, making this approach robust and suitable to many existing facilities.

Using one of the world most powerful laser facility, we demonstrate for the first time that high-contrast multi-picosecond pulses are advantageous for proton acceleration. By extending the pulse duration from 1.5 to 6 ps with fixed laser intensity of 10 18  W cm -2 , the maximum proton energy is improved more than twice (from 13 to 33 MeV). At the same time, laser-energy conversion efficiency into the MeV protons is enhanced with an order of magnitude, achieving 5% for protons above 6 MeV with the 6 ps pulse duration. The proton energies observed are discussed using a plasma expansion model newly developed that takes the electron temperature evolution beyond the ponderomotive energy in the over picoseconds interaction into account. The present results are quite encouraging for realizing ion-driven fast ignition and novel ion beamlines.

Structures containing the (R)-3-amino-3-methyl piperidine unit as a new pharmacophore moiety have been shown to possess moderate inhibitory activity for DPP-4 with good pharmacokinetics profile. One of these compounds was found to have good oral bioavailability and PK/PD profile in ZF-rat., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Objectives: This study was to investigate the effect of saliva used as storage liquid and the length of storage effect on surface hardnesses of Fuji IX (GP) (FIX), Dyract (DR), Z-100 and Estio LC (ELC)., Methods: The materials were mixed according to the manufacturers' instructions and immersed in distilled water or human parotid saliva. Vickers hardness number (HVN) was measured 1, 7, 20 and 40 days after the materials were mixed. HVN was calculated from the indentation diameter after 100 or 300g loading on their surface for 15s. The two methods of characterization used in this work were X-ray photoelectron spectroscopy (XPS) for surface chemical composition and electron probe microanalysis (EPMA) for depth profile analysis., Results: Only in FIX, did HVN increase with time at both storage conditions, distilled water and saliva. The increase rate of the value was higher when stored in saliva than distilled water. After 40 days storage in saliva, the HVN value of FIX increased by 39%. The increase for storage in saliva for DR was 22%, ELC 16%, and Z100 3%, compared to 1 day storage in distilled water. Ca and P peaks caused by saliva were detected by XPS and EPMA analysis, but these peaks did not exist in either composite resin or polyacid-modified composite resin by EPMA analysis., Significance: Saliva has the remarkable effect of increasing surface hardness of Fuji IX (GP).