| 131. |
- Senje, Lovisa, et al.
(författare)
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Diagnostics for studies of novel laser ion acceleration mechanisms.
- 2014
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 85:11
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Tidskriftsartikel (refereegranskat)abstract
- Diagnostic for investigating and distinguishing different laser ion acceleration mechanisms has been developed and successfully tested. An ion separation wide angle spectrometer can simultaneously investigate three important aspects of the laser plasma interaction: (1) acquire angularly resolved energy spectra for two ion species, (2) obtain ion energy spectra for multiple species, separated according to their charge to mass ratio, along selected axes, and (3) collect laser radiation reflected from and transmitted through the target and propagating in the same direction as the ion beam. Thus, the presented diagnostic constitutes a highly adaptable tool for accurately studying novel acceleration mechanisms in terms of their angular energy distribution, conversion efficiency, and plasma density evolution.
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| 132. |
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| 133. |
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| 134. |
- Sjögren, Anders, et al.
(författare)
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High-repetition-rate, hard x-ray radiation from a laser-produced plasma: Photon yield and application considerations
- 2003
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 74:4, s. 2300-2311
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Tidskriftsartikel (refereegranskat)abstract
- We present an experimental study of hard x rays produced in laser-produced plasmas. The laser used is a 1 kHz system, delivering 0.7 mJ for 25 fs onto a solid target. The x-ray spectrum was measured with calibrated germanium detectors, allowing a very good estimate of the absolute number of photons emitted from the plasma over a wide energy range; from 7 keV to 0.5 MeV. Assuming a bi-Maxwellian electron distribution with temperatures of 4.5 and 63 keV, theoretical calculations support the experimental findings. The imaging characteristics of the x-ray source were investigated experimentally employing image plates and theoretically based on the electron distribution. (C) 2003 American Institute of Physics.
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| 135. |
- Sjögren, Anders, et al.
(författare)
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Relativistic channel formation with different pulse durations
- 2002
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Ingår i: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 611, s. 119-125
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Konferensbidrag (refereegranskat)abstract
- Relativistic channels are generated in an under-dense plasma by means of subpicosecond laser pulses. The channel extension is characterized via the Thomson-scattered light and the impact of the laser pulse duration and chirp are studied. It is shown that, under certain conditions, the channel extends further when the pulse duration is increased. This is in contrast to many earlier reports, where the channel grows with increasing laser power. Some theoretical arguments are presented to support the experimental findings. The number of electrons, accelerated in the forward direction, and their energies are assessed. In some cases, it is found that the channel divides and the fragments extend in different directions. This raises the question if, and how, the channel formation can be externally manipulated
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| 136. |
- Sprengers, JP, et al.
(författare)
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Lifetime and predissociation yield of N-14(2) b (1)Pi(u)(v=1)
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 120:19, s. 8973-8978
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Tidskriftsartikel (refereegranskat)abstract
- The lifetime of the b (1)Pi(u)(v=1) state in N-14(2) has been determined experimentally using a laser-based pump-probe scheme and an exceptionally long lifetime of 2.61 ns was found. Semiempirical close-coupling calculations of the radiative lifetime, which include Rydberg-valence interactions in the singlet manifold, are consistent with this large value, giving a value of 3.61 ns and suggesting a predissociation yield of similar to28% for this level of the b state. (C) 2004 American Institute of Physics.
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| 137. |
- Sprengers, JP, et al.
(författare)
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Pump-probe lifetime measurements on singlet ungerade states in molecular nitrogen
- 2004
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 389:4-6, s. 348-351
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Tidskriftsartikel (refereegranskat)abstract
- Excited-state lifetimes for a number of vibronic states of (1)Pi(u) symmetry in molecular nitrogen have been determined experimentally in a laser-based pump-probe scheme using a coherent and tunable extreme ultraviolet source based on harmonic generation. States investigated in N-14(2) were b(1)Pi(u)(v = 6-9), of valence character, and c(3)(1)Pi(u)(v = 1) and o(3)(1)Pi(u)(v = 1), of Rydberg character. In the case of b(1)Pi(u)(v = 7) and c(3)(1)Pi(u)(v = 1), rotationally dependent predissociation was observed. States studied in N-15(2) were b(1)Pi(u)(v = 5) and c(3)(1)Pi(u)(v = 1); in addition, lifetimes of the c(4)'Sigma(u)(+)(v = 0,1) and b'(1)Sigma(u)(+)(v = 1) states were determined. The lifetimes show a dependence on the vibrational quantum number and isotope. (C) 2004 Elsevier B.V. All rights reserved.
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| 138. |
- Starczewski, Tomas, et al.
(författare)
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Time-resolved Harmonic-generation In An Ionizing Gas
- 1994
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 27:14, s. 3291-3301
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Tidskriftsartikel (refereegranskat)abstract
- We report on a time-resolved study of the fifth harmonic generated in xenon by 140 ps pulses from a Nd:YAG laser in the 10(13) W cm-2 intensity regime. Absolute timing between the driving laser pulse and the harmonic pulse could be determined by means of reference harmonics generated in non-linear crystals and a single common streak camera. Above a certain laser intensity the centre of the observed harmonic pulse was shifted earlier in time relative to the laser pulse. We found the intensity dependence of this shift to be approximately linear within the intensity range used which is consistent with the results of numerical simulations taking the ionization and dispersion of the xenon gas into account.
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| 139. |
- Svanberg, Sune, et al.
(författare)
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Atomic physics using short-wavelength coherent radiation
- 1997
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 398:1, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- Laser spectroscopy of free atoms has been pursued for 25 years starting in the visible region and with a constant thrust towards shorter wavelengths. A review of generation schemes and atomic-physics experiments in the short-wavelength region is given. Processes in ions and inner shells occur on a very fast timescale setting special demands on the sources. Using picosecond laser technology efficient frequency conversion and an adequate time resolution is achievable, but the spectral resolution is often impaired with such sources. Methods to achieve temporal as well as spectral resolution in the short-wavelength region are discussed. The use of high-order harmonics as tunable short-pulse radiation is described more in detail. Future possibilities for laser spectroscopy and atomic physics at short wavelengths are finally discussed.
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| 140. |
- Svanberg, Sune, et al.
(författare)
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Generation, characterization, and medical utilization of laser-produced emission continua
- 2000
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Ingår i: Laser and Particle Beams. - 0263-0346. ; 18:3, s. 563-570
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Tidskriftsartikel (refereegranskat)abstract
- Intense continua of electromagnetic radiation of very brief duration are formed in the interaction of focused ultra-short terawatt laser pulses with matter. Two different kinds of experiments, which have been performed utilizing the Lund 10 Hz titanium-doped sapphire terawatt laser system are being described, where visible radiation and X-rays, respectively, have been generated. Focusing into water leads to the generation of a light continuum through self-phase modulation. The propagation of the light through tissue was studied addressing questions related to optical mammography and specific chromophore absorption. When terawatt laser pulses are focused onto a solid target with high nuclear charge Z, intense X-ray radiation of few ps duration and with energies exceeding hundreds of keV is emitted. Biomedical applications of this radiation are described, including differential absorption and gated-viewing imaging.
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