| 1. |
- Cutic, Nino, et al.
(författare)
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An electro-optical system for MAX-lab test-fel facility
- 2009
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Ingår i: ; , s. 685-687
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Konferensbidrag (refereegranskat)abstract
- To get information about arrival of the electron bunch relative to the laser pulse; electro-optic detection scheme in near-crossed polarizer configuration was set up and tested. Electron bunch induced birefringence in ZnTe crystal leaves a polarization footprint in a chirped infrared pulse. The IR pulse is sampled before third harmonic generation from the amplifier, stretched and synchronized to the ultraviolet beam that is used for seeding. We report details of this setup and preliminary jitter measurements.
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| 2. |
- Cutic, Nino, et al.
(författare)
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Characterization of the arrival time jitter at the MAX-lab test-FEL using electro-optical spectral decoding
- 2011
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 626, s. 16-19
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Tidskriftsartikel (refereegranskat)abstract
- Electro-optical spectral decoding is used as an online diagnostic tool at the MAX-lab test-FEL to characterize the arrival time of electrons relative to the seed-laser pulse, measure the jitter between them and to measure the relative width of the electron bunch in order to optimize compression. Frequency characteristics of the jitter are presented. The measurements are used to get information on possible causes of the jitter and accompanying drifts. (C) 2010 Elsevier B.V. All rights reserved.
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| 3. |
- Cutic, Nino, et al.
(författare)
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Vacuum ultraviolet circularly polarized coherent femtosecond pulses from laser seeded relativistic electrons
- 2011
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Ingår i: Physical Review Special Topics. Accelerators and Beams. - 1098-4402. ; 14:3
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Tidskriftsartikel (refereegranskat)abstract
- We have demonstrated the generation of circularly polarized coherent light pulses at 66 nm wavelength by combining laser seeding at 263 nm of a 375 MeV relativistic electron bunch with subsequent coherent harmonic generation from an elliptical undulator of APPLE-II type. Coherent pulses at higher harmonics in linear polarization have been produced and recorded up to the sixth order (44 nm). The duration of the generated pulses depends on the temporal overlap of the initial seed laser pulse and the electron bunch and was on the order of 200 fs. Currently, this setup is the only source worldwide producing coherent fs-light pulses with variable polarization in the vacuum ultraviolet.
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| 4. |
- Erny, Christian, et al.
(författare)
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Metrology of high-order harmonics for free-electron laser seeding
- 2011
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- We examine the characteristics of high-order harmonics generated with 800 nm, 25 mJ, 160 fs laser pulses in an Ar gas cell with the objective of seeding a free electron laser. We measure the energy per pulse and per harmonic, the energy jitter, the divergence and the position stability of the harmonic beam. We perform ab initio numerical simulations based on integration of the time-dependent Schrodinger equation and of the wave equation within the slowly varying envelope approximation. The results reproduce the experimental measurements to better than a factor of two. The interaction of a frequency comb of harmonic fields with an electron bunch in an undulator is examined with a simple model consisting of calculating the energy modulation owing to the seed-electron interaction. The model indicates that the undulator acts as a spectral filter selecting a given harmonic.
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| 5. |
- Muscarella, Robert, et al.
(författare)
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The global abundance of tree palms
- 2020
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 29:9, s. 1495-1514
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Tidskriftsartikel (refereegranskat)abstract
- AimPalms are an iconic, diverse and often abundant component of tropical ecosystems that provide many ecosystem services. Being monocots, tree palms are evolutionarily, morphologically and physiologically distinct from other trees, and these differences have important consequences for ecosystem services (e.g., carbon sequestration and storage) and in terms of responses to climate change. We quantified global patterns of tree palm relative abundance to help improve understanding of tropical forests and reduce uncertainty about these ecosystems under climate change.LocationTropical and subtropical moist forests.Time periodCurrent.Major taxa studiedPalms (Arecaceae).MethodsWe assembled a pantropical dataset of 2,548 forest plots (covering 1,191 ha) and quantified tree palm (i.e., ≥10 cm diameter at breast height) abundance relative to co‐occurring non‐palm trees. We compared the relative abundance of tree palms across biogeographical realms and tested for associations with palaeoclimate stability, current climate, edaphic conditions and metrics of forest structure.ResultsOn average, the relative abundance of tree palms was more than five times larger between Neotropical locations and other biogeographical realms. Tree palms were absent in most locations outside the Neotropics but present in >80% of Neotropical locations. The relative abundance of tree palms was more strongly associated with local conditions (e.g., higher mean annual precipitation, lower soil fertility, shallower water table and lower plot mean wood density) than metrics of long‐term climate stability. Life‐form diversity also influenced the patterns; palm assemblages outside the Neotropics comprise many non‐tree (e.g., climbing) palms. Finally, we show that tree palms can influence estimates of above‐ground biomass, but the magnitude and direction of the effect require additional work.ConclusionsTree palms are not only quintessentially tropical, but they are also overwhelmingly Neotropical. Future work to understand the contributions of tree palms to biomass estimates and carbon cycling will be particularly crucial in Neotropical forests.
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| 6. |
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| 7. |
- Werin, Sverker, et al.
(författare)
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The test FEL facility at MAX-lab
- 2009
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Ingår i: ; , s. 313-316
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Konferensbidrag (refereegranskat)abstract
- A facility for seeding and harmonic generation utilizing an optical klystron is under commissioning at MAX-lab. The facility utilizes the 400 MeV linac accelerator, improved operation of an RF-gun, an undulator system of two undulators and a magnetic chicane and combined laser system for gun and seeding. The goal is to seed the electron beam at 263 nm and generate the harmonics 2-5 (131-53 nm). Currently the system is under commissioning. We report on the operation of the subsystems and the latest results on the commissioning towards achieving harmonic generation.
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