| 1. |
- Bashkanov, M., et al.
(författare)
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Two-pion production in proton-proton collisions
- 2004
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Ingår i: Hadron Spectroscopy, Tenth International Conference on Hadron Spectrscopy, Aschaffenburg, Germany 31 August - 6 September 2003. - 0735401977 ; , s. 241-244
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Busch, S., et al.
(författare)
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Ion acceleration with ultrafast lasers
- 2003
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:19, s. 3354-3356
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Tidskriftsartikel (refereegranskat)abstract
- Hot-electron confinement can build up fields capable of accelerating ions up to MeV energies when an ultrashort 35-fs laser pulse at similar to2x10(18) W/cm(2) interacts with a small spherical target. Singly charged ions with different masses have similar energies. A simple phenomenological model describes how ultrashort and less-energy-consumptive pulses drive ions to MeV energies. The energetic and spatial-emission characteristics of protons, deuterons and oxygen ions released from water and heavy-water droplets of similar to15 mum in size was determined for this interaction scenario.
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| 3. |
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| 4. |
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| 5. |
- Korn, G., et al.
(författare)
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Ultrashort 1-kHz laser plasma hard x-ray source
- 2002
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 27:10, s. 866-868
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Tidskriftsartikel (refereegranskat)abstract
- We achieved a continuous, stable, ultrashort pulse hard x-ray point source by focusing 1.8-W, 1-kHz, 50-fs laser pulses onto a novel, 30-mum-diameter, high-velocity, liquid-metal gallium jet. This target geometry avoids most of the debris problems of solid targets and provides nearly 4pi illumination. Photon fluxes of 5 X 10(8) photons/s are generated in a two-component spectrum consisting of a broad continuum from 4 to 14 keV and strong K-alpha and K-beta emission lines at 9.25 and 10.26 keV. This source will find wide use in time-resolved x-ray diffraction studies and other applications.
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| 6. |
- Schnurer, M., et al.
(författare)
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Influence of laser pulse width on absolute EUV-yield from Xe-clusters
- 2001
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Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 14:3, s. 331-335
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Tidskriftsartikel (refereegranskat)abstract
- Using 50 fs (similar to 2 x 10(18) W/cm(2)) and 2 ps (similar to 5 x 10(16) W/cm(2)) pulses from a Ti:Sa multi-TW laser at 800 nm wavelength large Xe-clusters (10(5)...10(6) atoms per cluster) have been excited. Absolute yield measurements of EUV-emission in a wavelength range between 10 nm and 15 nm in combination with cluster target variation were carried out. The ps-laser pulse has resulted in about 30% enhanced and spatially more uniform EUV-emission compared to fs-laser excitation. Circularly polarized laser light instead of linear polarization results in enhanced emission which is probably caused by electrons gaining higher energies by the polarization dependent optical field ionization process. An absolute emission efficiency at 13.4 nm of up to 0.8% in 2 pi sr and 2.2% bandwidth has been obtained.
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| 7. |
- Thoss, A., et al.
(författare)
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Kilohertz sources of hard x rays and fast ions with femtosecond laser plasmas
- 2003
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 20:1, s. 224-228
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a new, stable, kilohertz femtosecond laser plasma source of hard-x-ray continuum and K-alpha emission that uses a microscopic liquid jet target that is continuous and debris free. Plasmas produced by ultrashort (50-fs) intense laser pulses from a fine (10-30-mum diameter) liquid Ga jet emit bright 9.3- and 10.3-keV K-alpha and K-beta lines superimposed on a multikilovolt bremmstrahlung continuum. Kilohertz femtosecond x-ray sources will find many applications in time-resolved x-ray diffraction and microscopy studies. As high-intensity lasers become more compact and operate at increasingly high repetition-rates, they require a target configuration that is both repeatable from shot to shot and debris free. Our target provides a pristine, unperturbed filament surface at rates >100 kHz. A number of liquid metal targets are considered. We show the hard-x-ray spectrum described above. The source was generated by a 50-fs-duration, 1-kHz, 2-W, high-intensity Ti:sapphire laser. Using the same technology, we also generate forward-going sub-mega-electron-volt (sub-MeV) protons from a 10-mum liquid water target at 1-kHz repetition rates. Kilohertz sources of high-energy ions will find many applications in time-resolved particle interaction studies and will lead to efficient generation of short-lived isotopes for use in nuclear medicine and other applications. The protons were detected with CR-39 track detectors in both the forward and the backward directions up to energies of similar to500 keV. As the intensity of compact high-repetition-rate lasers sources increases, we can expect improvements in the energy, conversion efficiency, and directionality to occur. The effect of these developments is discussed. As compact, high-repetition-rate femtosecond laser technology reaches focused intensities of similar to10(19) W/cm(2), many new applications of high-repetition-rate hard-x-ray and MeV ion sources will become practical.
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| 8. |
- Vogt, Ulrich, et al.
(författare)
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Design and application of a zone plate monochromator for laboratory soft x-ray sources
- 2001
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 72:1, s. 53-57
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Tidskriftsartikel (refereegranskat)abstract
- In this article we describe the test of a zone plate monochromator for a laboratory soft x-ray source which is a laser produced plasma on a liquid jet target. The monochromator consists of a zone plate and a pinhole. Due to the special zone plate used (condensor zone plate KZP7) the monochromator is particularly suitable for laboratory sources since it collects a relatively large solid angle in the present setup. Depending upon the diameter of the pinhole a monochromaticity of up to lambda/Delta lambda =600 can be achieved. The usefulness of the linear monochromator was proven on the basis of a filter transmission measurement. The monochromator can be used for several applications. In particular it is suitable for time-resolved x-ray absorption spectroscopy and pump and probe experiments. The use for such investigations is discussed.
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| 9. |
- Beck, M., et al.
(författare)
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A pulse-train laser driven XUV source for picosecond pump-probe experiments in the water window
- 2001
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Ingår i: Optics Communications. - 0030-4018 .- 1873-0310. ; 190:06-jan, s. 317-326
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Tidskriftsartikel (refereegranskat)abstract
- We describe the development of a table top soft X-ray source based on a laser produced plasma. The plasma is produced by a Nd:YLF pulse-train laser which delivers pulse trains of up to 400 pulses each of about 25 ps duration, Number and energy of the micropulses are fully computer controlled adjustable for an optimum interaction with a rotating solid target. Spectral, spatial and temporal characteristics of the X-ray emission from Mylar and copper targets have been studied. A calibrated back-illuminated CCD camera together with a slit grating spectrograph were utilized for the measurement of the absolute soft X-ray photon fluxes. The temporal measurements were performed using a streak camera while the plasma size was measured with a zone plate. An application of the system in a X-ray absorption experiment is shown, The advantages of the system in view of possible optical pump and soft X-ray probe experiments will be discussed.
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| 10. |
- Beck, M., et al.
(författare)
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Evaluation of the energetic position of the lowest excited singlet state of beta-carotene by NEXAFS and photoemission spectroscopy
- 2001
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Ingår i: Biochimica et Biophysica Acta - Bioenergetics. - 0005-2728 .- 1879-2650. ; 1506:3, s. 260-267
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Tidskriftsartikel (refereegranskat)abstract
- In carotenoids the lowest energetic optical transition belonging to the pi -electron system is forbidden by symmetry, therefore the energetic position of the S-1 (2(1)A(g)) level can hardly be assessed by optical spectroscopy. We introduce a novel experimental approach: For molecules with ir-electron systems the transition C1s --> 2p(pi*) from inner-atomic to the lowest unoccupied molecular orbital (LUMO) appears in X-ray absorption near edge spectra (NEXAFS) as an intense, sharp peak a few eV below the carbon K-edge. Whereas the peak position reflects the energy of the First excited singlet state in relation to the ionization potential of the molecule, intensity and width of the transition depend on hybridization and bonding partners of the selected atom. Complementary information can be obtained from ultraviolet photoelectron spectroscopy (UPS): At the low binding energy site of the spectrum a peak related to the highest occupied molecular orbital (HOMO) appears. We have measured NEXAFS and UPS of beta -carotene. Based on these measurements and quantum chemical calculations the HOMO and LUMO energies can be derived.
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