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Title: Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses

Abstract

We measured the time-integrated, spatially resolved spectra of soft x rays emitted from laser-induced aluminum plasma to characterize its spatial features. The plasma was excited by an intense femtosecond-laser pulse with a controlled artificial prepulse at intensities of 9.9x10{sup 15} and 6.4x10{sup 14} W/cm{sup 2}, respectively. The dependence of the spectra on the time intervals between the main pulse and the prepulse was obtained for delay times of 0-3 ns. The strongest emissions in soft x-ray range occurred in a narrow region less than 50 {mu}m from the target surface. In contrast to the continuum spectrum, the prepulse technique causes the Al{sup 3+}2p{sup 6}-2p{sup 5}3s emission to extend more than 600 {mu}m from the target surface. We showed that the line emission can be separated spatially from the other continuum component of the emission spectra and that the extension length increased with increases in the pulse-separation time.

Authors:
; ; ;  [1]
  1. NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)
Publication Date:
OSTI Identifier:
20787969
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 99; Journal Issue: 6; Other Information: DOI: 10.1063/1.2180433; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALUMINIUM; ALUMINIUM IONS; EMISSION SPECTRA; LASERS; LIGHT TRANSMISSION; PHOTON EMISSION; PLASMA; PLASMA DIAGNOSTICS; PLASMA PRODUCTION; PULSES; SOFT X RADIATION; SPATIAL DISTRIBUTION; X-RAY SOURCES

Citation Formats

Okano, Yasuaki, Oguri, Katsuya, Nishikawa, Tadashi, and Nakano, Hidetoshi. Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses. United States: N. p., 2006. Web. doi:10.1063/1.2180433.
Okano, Yasuaki, Oguri, Katsuya, Nishikawa, Tadashi, & Nakano, Hidetoshi. Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses. United States. doi:10.1063/1.2180433.
Okano, Yasuaki, Oguri, Katsuya, Nishikawa, Tadashi, and Nakano, Hidetoshi. Wed . "Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses". United States. doi:10.1063/1.2180433.
@article{osti_20787969,
title = {Spatial distribution of soft x-ray line emissions from aluminum plasma excited by a pair of femtosecond-laser pulses},
author = {Okano, Yasuaki and Oguri, Katsuya and Nishikawa, Tadashi and Nakano, Hidetoshi},
abstractNote = {We measured the time-integrated, spatially resolved spectra of soft x rays emitted from laser-induced aluminum plasma to characterize its spatial features. The plasma was excited by an intense femtosecond-laser pulse with a controlled artificial prepulse at intensities of 9.9x10{sup 15} and 6.4x10{sup 14} W/cm{sup 2}, respectively. The dependence of the spectra on the time intervals between the main pulse and the prepulse was obtained for delay times of 0-3 ns. The strongest emissions in soft x-ray range occurred in a narrow region less than 50 {mu}m from the target surface. In contrast to the continuum spectrum, the prepulse technique causes the Al{sup 3+}2p{sup 6}-2p{sup 5}3s emission to extend more than 600 {mu}m from the target surface. We showed that the line emission can be separated spatially from the other continuum component of the emission spectra and that the extension length increased with increases in the pulse-separation time.},
doi = {10.1063/1.2180433},
journal = {Journal of Applied Physics},
number = 6,
volume = 99,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • The influence of a prepulse on soft x-ray emission in the range of 50{approximately}200 A from Al plasma produced by 130-fs Ti:sapphire laser pulses was studied at an intensity of 10{sup 14} W/cm{sup 2} at normal incidence. A prepulse with an intensity of 10{sup 13} W/cm{sup 2} caused enhancement of soft x-ray emission with a large time separation between prepulse and an intense main pulse. However at 800 nm, a prepulse resulted in reduction with small pulse time separation, contrary to previous reports. This observed trends were qualitatively explained in terms of the absorption dependence on scale length. {copyright} {italmore » 1996 American Institute of Physics.}« less
  • The temporal and spectral evolution of soft x-ray pulses (40{endash}100 A) emitted from Al plasma produced by a pair of femtosecond Ti:sapphire laser pulses at normal incidence was studied. Both the soft x-ray emission and the pulse duration increased with increase in the scale length of the preformed plasma. Prepulse enhanced soft x-ray emission about 100 times with a pulse duration of 100{endash}130 ps. A spectrally resolved time history revealed that the emission at shorter wavelengths started and decayed relatively more quickly, and emissions at longer wavelengths built up and decayed more slowly. {copyright} {ital 1996 American Institute of Physics.}
  • We compare x-ray spectra from optical-field-ionized plasmas generated by linearly and elliptically polarized 250-fs Ti:sapphire laser pulses. The experiment demonstrates the difference in the spectra resulting from the different electron temperatures under these two conditions. To avoid high-density effects such as electron heating, collisional ionization, or ionization defocusing the plasmas are generated under well-controlled conditions in a low-pressure gas cell. For the gases investigated (He, N{sub 2},O{sub 2}, and CH{sub 4}) a significantly higher x-ray intensity is observed for elliptically than for linearly polarized light on the majority of lines. This finding is in accord with general theoretical expectations andmore » with the result of simulations. However, for linear polarization, anomalies occur in the relative line intensities of several lines. Possible mechanisms responsible for this effect are discussed. {copyright} {ital 1997} {ital The American Physical Society}« less
  • We report a 43-fold enhancement in the hard x-ray emission (in the 150-300 keV range) from copper nanorod arrays (compared to a polished Cu surface) when excited by 30-fs, 800-nm laser pulses with an intensity of 10{sup 16} W/cm{sup 2}. The temperature of the hot electrons that emit the x rays is 11 times higher. Significantly, the x-ray yield enhancement is found to depend on both the aspect ratio as well as the cluster size of the nanorods. We show that the higher yield arises from enhanced laser absorption owing to the extremely high local electric fields around the nanorodmore » tips. Particle-in-cell plasma simulations reproduce these observations and provide pointers to further optimization of the x-ray emission.« less
  • A laser plasma was generated by pulses of approx.5 x 10/sup 15/ W/cm/sup 2/ intensity and tauapprox.10/sup -10/ sec duration. The x-ray emission spectra of this plasma were recorded in the spectral range 3--18 A. The apparatus employed made it possible to record the spectrum produced by a single laser flash and its resolving power was high (lambda/..delta..lambdaapprox.5000). The relative intensities of the lines due to helium-like and hydrogen-like ions were used in the determination of the electron temperature T/sub e/ and electron density N/sub e/ in the plasma. The spatial distribution of the x-ray emission of a magnesium plasmamore » was determined with a resolution of 25 ..mu... The laser radiation was focused on a plane target and in a recess. In both cases the values of T/sub e/, N/sub e/, and of the Stark and Doppler broadenings of several lines (T/sub e/ was found from the relative intensities of the lines and N/sub e/ from the relative intensities and Stark broadening) were determined as a function of the distance to the target. (AIP)« less