| 11. |
- Fullagar, Wilfred, et al.
(författare)
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A broadband laser plasma X-ray source for application in ultrafast chemical structure dynamics
- 2007
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 78:11, s. 1-115105
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Tidskriftsartikel (refereegranskat)abstract
- A plasma source free from characteristic emission lines is described, based on laser irradiation of a water jet in a helium atmosphere. Various key aspects of the laser interaction are presented along with practical characterization of the observed isotropic ~4–10 keV x-ray emissions, measurements of which indicate subpicosecond duration. Observations are consistent with a vacuum heating plasma mechanism at the helium-water interface and indicate strong potential for in-house ultrafast chemical structure dynamics application when coupled to contemporary detector developments.
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| 12. |
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| 13. |
- Glinec, Yannick, et al.
(författare)
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Evolution of energy spectrum from laser-accelerated protons with a 100 fs intense prepulse
- 2008
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Ingår i: Applied Physics B. - : Springer Science and Business Media LLC. - 0946-2171 .- 1432-0649. ; 93:2-3, s. 317-321
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Tidskriftsartikel (refereegranskat)abstract
- A parametric study is reported where a femtosecond prepulse is used to change the target properties before the interaction with a multi-terawatt laser pulse which accelerates protons from a foil target. The proton spectrum as function of the prepulse delay and intensity, up to 1.5 ns and up to 3x106 W/cm2, respectively, shows a global decrease of the maximum proton energy with delay and intensity. However, under appropriate conditions, it is found that the maximum proton energy increases by more than 10% and that the spectral shape changes.
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| 14. |
- Kazamias, S, et al.
(författare)
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Characterization of a transient collisional Ni-like molybdenum soft x-ray laser pumped in grazing incidence
- 2008
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:3
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental results from an extensive investigation of a Ni-like Mo X-ray laser pumped in the transient regime and GRIP configuration (GRazing Incidence Pumping). The pump laser is a 10 Hz, 1 J, Ti:Sa laser system. The main diagnostic is a monochromatic near-field imaging system with a 1.7 micron spatial resolution that shows the soft x-ray laser source size and position relative to the target surface. Changes of those characteristics are observed for different GRIP angles, varied between 15◦ and 21◦, while keeping all other parameters constant. Intense lasing is observed routinely at 18.9 nm with up to 3 microjoule output energy and stable operation is demonstrated at 10 Hz. We have investigated the role of several pumping parameters, in particular the relative energy and delay between the long and short pulse. We show that this multi-parameter scan leads to a well-defined optimal regime of operation and better understanding of the GRIP configuration. Finally, as the GRIP scheme requires careful tailoring of the plasma conditions to the specific soft x-ray laser under investigation, we add a prepulse before the plasma producing long pulse to generate large-scale preplasmas. This increases the brightness of the soft x-ray beam and leads to an almost gaussian near-field spatial profile.
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| 15. |
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| 16. |
- Kovacev, M, et al.
(författare)
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Extreme ultraviolet fourier-transform spectroscopy with high order harmonics
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:22
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a new scheme for extreme ultraviolet (xuv) Fourier-transform spectroscopy based on the generation of two phase-locked high-harmonic beams. It allows us to measure for the first time interferograms at wavelengths as short as 90 nm, and open the perspective of performing high-resolution Fourier-transform absorption spectroscopy in the xuv. Our measurements also demonstrate that a precise control of the relative phase of harmonic pulses can be obtained with an accuracy on an attosecond time scale, of importance for future xuv pump-xuv probe attosecond spectroscopy.
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| 17. |
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| 18. |
- Lindau, Filip, et al.
(författare)
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Characterization of quasi-monoenergetic electron beams at the lund laser centre
- 2008
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Ingår i: IEEE Transactions on Plasma Science. - 0093-3813. ; 36:4, s. 1707-1714
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Tidskriftsartikel (refereegranskat)abstract
- Experiments performed with the high-contrast 0.7-J 35-fs Ti:sapphire laser at the Lund Laser Centre focused into a helium gas jet have produced quasi-monoenergetic electron beams with energies up to 150 MeV. The beam is produced as a result of controlled wavebreaking of a wakefield generated by the relativistically channeled laser beam. Under the best conditions of laser energy and plasma density, a beam with narrow-energy-spread component was produced on every shot with an energy stability of similar to 10% and a pointing stability of similar to 6 mrad. Furthermore, it can be deduced that the electron beam originates from a source with both transverse and longitudinal extents < 10 mu m, implying a pulselength of < 25 fs. These measurements mark an important improvement in the characterization, as well as repeatability, of laser-plasma-generated electron beams with a single driver laser beam.
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| 19. |
- Lindau, Filip, et al.
(författare)
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Laser-accelerated protons with energy dependent beam direction
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95:175002, s. 1-175002
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Tidskriftsartikel (refereegranskat)abstract
- The spatial distribution of protons, accelerated by intense femtosecond laser pulses interacting with thin target foils under oblique irradiation are investigated. Under certain conditions, the proton beams are directed away from the target normal. This deviation is towards the laser forward direction, with an angle that increases with the level and duration of the amplified spontaneous emission pedestal before the main laser pulse. In addition, for a given laser pulse, this beam deviation increases with proton energy. The observations are discussed in terms of different electron acceleration mechanisms and target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target rear surface.
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| 20. |
- Lindau, Filip, et al.
(författare)
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Quantitative study of 10 Hz operation of a soft x-ray laser-energy stability and target considerations
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:15, s. 9486-9493
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Tidskriftsartikel (refereegranskat)abstract
- A soft x- ray laser from Ni- like Mo, pumped in grazing incidence ( GRIP), is analyzed with regard to high repetition rate operation. Reliable lasing is obtained, but with significant energy fluctuations attributed mainly to beam pointing jitter from the pump laser. Two modes of operation are compared: continuously moving target and stationary target. With a moving target the soft X- ray output is constant on average, whereas the repeated use of the same target position leads to a pulse energy which increases for several tens of shots. This effect might be caused by improved guiding of the pump laser in the formed groove and the removal, through laser ablation, of the oxide layer on the target surface. (c) 2007 Optical Society of America.
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