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- Cacciani, P., et al.
(författare)
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Lifetime measurements of the e1II, v = 0 and v = 1 states of12C16O, 13C16O, and13C18O
- 1998
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Ingår i: Astrophysical Journal. - 0004-637X. ; 499:2 PART II, s. 223-226
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Tidskriftsartikel (refereegranskat)abstract
- In a laboratory investigation using tunable picosecond lasers in a pump-probe configuration, lifetimes of the E 1u, v = 0 and v = 1 states of CO are experimentally determined. For E 'D, v = 1, the lifetime is found to vary significantly for the isotopomers. Combining the data with existing oscillator strengths, predissociation probabilities within the range of 93.6%-98.6% result for 12C16O, 13C16O, and 13C18O in the case of the E 1u, v = I state, which is the state that predominantly influences the isotopic fractionation of CO in interstellar clouds.
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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. |
- Batani, D., et al.
(författare)
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Effects of laser prepulses on laser-induced proton generation
- 2010
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Low-intensity laser prepulses (<10(13) W cm(-2), nanosecond duration) are a major issue in experiments on laser-induced generation of protons, often limiting the performances of proton sources produced by high-intensity lasers (approximate to 10(19) W cm(-2), picosecond or femtosecond duration). Depending on the intensity regime, several effects may be associated with the prepulse, some of which are discussed in this paper: (i) destruction of thin foil targets by the shock generated by the laser prepulse; (ii) creation of preplasma on the target front side affecting laser absorption; (iii) deformation of the target rear side; and (iv) whole displacement of thin foil targets affecting the focusing condition. In particular, we show that under oblique high-intensity irradiation and for low prepulse intensities, the proton beam is directed away from the target normal. Deviation is towards the laser forward direction, with an angle that increases with the level and duration of the ASE pedestal. Also, for a given laser pulse, the beam deviation increases with proton energy. The observations are discussed in terms of target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target surface.
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| 7. |
- Ferri, J., et al.
(författare)
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Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
- 2020
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Ingår i: Journal of Plasma Physics. - : Cambridge University Press (CUP). - 0022-3778 .- 1469-7807. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Using particle-in-cell simulations, we demonstrate an improvement of the target-normal-sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.
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| 8. |
- Ferri, Julien, 1990, et al.
(författare)
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Enhancement of laser-driven ion acceleration in non-periodic nanostructured targets
- 2020
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 86:1
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Tidskriftsartikel (refereegranskat)abstract
- Using particle-in-cell simulations, we demonstrate an improvement of the target-normal-sheath acceleration (TNSA) of protons in non-periodically nanostructured targets with micron-scale thickness. Compared to standard flat foils, an increase in the proton cutoff energy by up to a factor of two is observed in foils coated with nanocones or perforated with nanoholes. The latter nano-perforated foils yield the highest enhancement, which we show to be robust over a broad range of foil thicknesses and hole diameters. The improvement of TNSA performance results from more efficient hot-electron generation, caused by a more complex laser-electron interaction geometry and increased effective interaction area and duration. We show that TNSA is optimized for a nanohole distribution of relatively low areal density and that is not required to be periodic, thus relaxing the manufacturing constraints.
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| 10. |
- Gratz, M, et al.
(författare)
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Time-gated x-ray tomography
- 1998
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 73:20, s. 2899-2901
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Tidskriftsartikel (refereegranskat)abstract
- Time-gated x-ray tomography with scatter reduction is demonstrated using a laser-produced plasma as an ultrashort-pulse x-ray source in combination with a time-resolving streak-camera detector. Backprojections of a phantom imbedded in 9 cm of water show an effective 50% increase in contrast when scattered x-ray quanta (being delayed in time) are suppressed by gating on the prompt, nonscattered photons. Implications for future volumetric tomography, in particular concerning possible dose reductions, are discussed. (C) 1998 American Institute of Physics. [S0003-6951(98)02846-0].
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