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| 2. |
- Pirozhkov, A. S., et al.
(författare)
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Diagnostic of laser contrast using target reflectivity
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:24
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Tidskriftsartikel (refereegranskat)abstract
- Using three different laser systems, we demonstrate a convenient and simple plasma based diagnostic of the contrast of high-power short-pulse lasers. The technique is based on measuring the specular reflectivity from a solid target. The reflectivity remains high even at relativistic intensities above 10(19) W/cm(2) in the case of a high-contrast prepulse-free laser. On the contrary, the specular reflectivity drops with increasing intensities in the case of systems with insufficient contrast due to beam breakup and increased absorption caused by preplasma.
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| 3. |
- Kerzenmacher, T., et al.
(författare)
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Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:19, s. 5801--5841-
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Tidskriftsartikel (refereegranskat)abstract
- Vertical profiles of NO2 and NO have been obtained from solar occultation measurements by the Atmospheric Chemistry Experiment (ACE), using an infrared Fourier Transform Spectrometer (ACE-FTS) and (for NO2) an ultraviolet-visible-near-infrared spectrometer, MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). In this paper, the quality of the ACE-FTS version 2.2 NO2 and NO and the MAESTRO version 1.2 NO2 data are assessed using other solar occultation measurements (HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY), stellar occultation measurements (GOMOS), limb measurements (MIPAS, OSIRIS), nadir measurements (SCIAMACHY), balloon-borne measurements (SPIRALE, SAOZ) and ground-based measurements (UV-VIS, FTIR). Time differences between the comparison measurements were reduced using either a tight coincidence criterion, or where possible, chemical box models. ACE-FTS NO2 and NO and the MAESTRO NO2 are generally consistent with the correlative data. The ACE-FTS and MAESTRO NO2 volume mixing ratio (VMR) profiles agree with the profiles from other satellite data sets to within about 20% between 25 and 40 km, with the exception of MIPAS ESA (for ACE-FTS) and SAGE II (for ACE-FTS (sunrise) and MAESTRO) and suggest a negative bias between 23 and 40 km of about 10%. MAESTRO reports larger VMR values than the ACE-FTS. In comparisons with HALOE, ACE-FTS NO VMRs typically (on average) agree to ±8% from 22 to 64 km and to +10% from 93 to 105 km, with maxima of 21% and 36%, respectively. Partial column comparisons for NO2 show that there is quite good agreement between the ACE instruments and the FTIRs, with a mean difference of +7.3% for ACE-FTS and +12.8% for MAESTRO.
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| 4. |
- Carroll, DC, et al.
(författare)
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Active manipulation of the spatial energy distribution of laser-accelerated proton beams
- 2007
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Ingår i: Physical Review E (Statistical, Nonlinear, and Soft Matter Physics). - 1539-3755. ; 76:065401(R), s. 1-065401
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Tidskriftsartikel (refereegranskat)abstract
- The spatial energy distributions of beams of protons accelerated by ultrahigh intensity (>10^19 W/cm2) picosecond laser pulse interactions with thin foil targets are investigated. Using separate, low intensity (<10^13 W/cm2) nanosecond laser pulses, focused onto the front surface of the target foil prior to the arrival of the high intensity pulse, it is demonstrated that the proton beam profile can be actively manipulated. In particular, results obtained with an annular intensity distribution at the focus of the low intensity beam are presented, showing smooth proton beams with a sharp circular boundary at all energies, which represents a significant improvement in the beam quality compared to irradiation with the picosecond beam alone.
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| 5. |
- McKenna, P., et al.
(författare)
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Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets
- 2008
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 26:4, s. 591-596
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Tidskriftsartikel (refereegranskat)abstract
- The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients due, to self-focusing Of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.
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| 6. |
- Ray, A. K., et al.
(författare)
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Mechanical property and characterization of a NiCoCrAlY type metallic bond coat used in turbine blade
- 2009
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Ingår i: Materials Science and Engineering A. - : Elsevier BV. - 0921-5093. ; 505:1-2, s. 96-104
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Tidskriftsartikel (refereegranskat)abstract
- This paper highlights some of the results obtained while studying Ni20Co18Cr12.5Al0.6Y (NiCoCrAlY) type metallic bond-coat properties of a thermal-barrier coated (TBC), AE-437A Ni base superalloy mostly employed for manufacturing compressor and stationary stator blades in aero turbines. Experiments were mainly focused in the area of evaluation of microstructure, residual stress, shear strength, hardness and with special emphasis in establishing the ductile to brittle transition temperature (DBTT) of the bond coat by using acoustic emission technique during room temperature and high temperature tensile tests. Results reveal that the residual stress was tensile in nature in the TBC layer and compressive in the bond coat as well as in the substrate. The DBTT of this bond coat is around 650 °C, which is in close proximity to the value reported in literature for CoCrAlY type of bond coat. Finite element technique was used to analyze the equivalent stresses in the bond coat, the result of which revealed the highest order of equivalent stress 800 °C, as the bond coat is ductile above 650 °C. Shear strength of the bond coat is in close proximity with that of the bond strength reported in literature for CoCrAlY and Ni22Co17Cr12.5Al0.6Y types of bond coat. © 2009 Elsevier B.V. All rights reserved.
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| 7. |
- Robinson, A. P. L., et al.
(författare)
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Spectral modification of laser-accelerated proton beams by self-generated magnetic fields
- 2009
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Target normal measurements of proton energy spectra from ultrathin (50-200 nm) planar foil targets irradiated by 10(19) W cm(-2) 40 fs laser pulses exhibit broad maxima that are not present in the energy spectra from micron thickness targets (6 mu m). The proton flux in the peak is considerably greater than the proton flux observed in the same energy range in thicker targets. Numerical modelling of the experiment indicates that this spectral modification in thin targets is caused by magnetic fields that grow at the rear of the target during the laser-target interaction.
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| 8. |
- Campbell, S., et al.
(författare)
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Frequency-doubling in femtosecond laser inscribed periodically-poled potassium titanyl phosphate waveguides
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:25, s. 17146-17150
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Tidskriftsartikel (refereegranskat)abstract
- Frequency doubling has been achieved in femtosecond-laser-inscribed single-mode waveguides written in two periodically-poled potassium titanyl phosphate crystals. A conversion efficiency of 0.22 %W-1 was obtained for first-order quasi-phase matching at 980 nm and an efficiency of 0.02 %W-1 for third-order quasi-phase matching at 800 nm.
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| 9. |
- Campbell, S., et al.
(författare)
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Frequency doubling in femtosecond-written periodically-poled potassium titanyl phosphate waveguides
- 2007
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Ingår i: Lasers and Electro-Optics, 2007 European Conference on and the International Quantum Electronics Conference. - 1424409306 - 9781424409303 ; , s. 4386106-
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Konferensbidrag (refereegranskat)abstract
- The second-harmonic conversion efficiency within the PPKTP waveguide is investigated using two separate tunable CW Ti:sapphire lasers at 800 nm and 980 nm. Results show strong conversion efficiency which imply that the local damage-induced index modification does not adversely affect the periodic domain structure in the material.
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| 10. |
- Campbell, S., et al.
(författare)
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Frequency doubling in femtosecond-written periodically-poled potassium titanyl phosphate waveguides
- 2007
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Ingår i: Conference on Lasers and Electro-Optics, 2007, CLEO 2007. - 9781557528346 ; , s. 4452462-
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Konferensbidrag (refereegranskat)abstract
- Frequency doubling is demonstrated in femtosecond-laser-created single-mode waveguides written in a periodically-poled potassium titanyl phosphate crystal. Conversion efficiencies of 0.22%/W (0.02%/W) were obtained for first (third) order phasematching at 980nm (800nm).
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