| 1. |
- Ramstein, B, et al.
(författare)
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H-2(He-3, t)2p reaction at 2 GeV
- 2003
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 16:4, s. 583-597
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Tidskriftsartikel (refereegranskat)abstract
- The exclusive H-2 (He-3, t)2p reaction has been studied at 2 GeV for energy transfers up to 500 MeV and triton angles up to 3.4degrees. The protons were measured in the large acceptance magnetic detector DIOGENE, in coincidence with the forward tritons detected in a dedicated magnetic arm. The energy transfer spectra extend well above the pion threshold. However, in the region of Delta excitation, the yield is less than 10% of the inclusive H-2(He-3, t) cross-section, which indicates the small contribution of the DeltaN --> NN process. The angular distributions of the two protons in their center of mass have been analysed as a function of energy transfer and triton angle and a Legendre polynomial decomposition has been achieved. These data have been compared to a model based on a coupled-channel approach for describing the NN and NDelta systems.
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| 2. |
- Roos, L, et al.
(författare)
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Tailoring harmonic radiation to different applications using a genetic algorithm
- 2001
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 34:24, s. 5041-5054
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Tidskriftsartikel (refereegranskat)abstract
- We use a genetic algorithm to theoretically optimize several properties of extreme ultraviolet (XUV) radiation, generated as high-order harmonics in xenon and argon. We maximize the harmonic pulse energy, minimize the pulse duration or optimize the temporal coherence by varying at the same time two or three parameters that are easily accessible in experiments, related to the characteristics of the laser beam and the nonlinear medium. For the 15th and 29th harmonies in argon, we find up to 10(9) photons per pulse, and pulse durations as short as 6 fs generated by a 50 fs laser pulse. We can also tailor the phase matching conditions to spectrally select the transform-limited part of the harmonic radiation. This allows us to identify conditions when the time structure of the XUV radiation presents a train of attosecond pulses. We find that the optimum conditions for the different properties are in general not the same. They depend in particular on whether the harmonic belongs to the plateau or the cutoff region of the harmonic spectrum. This reflects the unavoidable interplay between the microscopic intensity-dependent harmonic phase and the macroscopic phase matching conditions imposed by a nonlinear medium interacting with an intense, focused laser beam.
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| 3. |
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