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O'Sullivan, Gerry
Preferred name
O'Sullivan, Gerry
Official Name
O'Sullivan, Gerry
Research Output
Now showing 1 - 10 of 17
- PublicationShorter-wavelength extreme-UV sources below 10nm(SPIE, 2011-10-07)
; ; ; ; ; ; ; A next-generation laser-produced plasma system based on rare-earth targets generates strong resonant line emissions at 6.5–6.7nm.346 - PublicationSpectral and temporal behavior of an alkali metal plasma extreme ultraviolet source for surface morphology applications(American Institute of Physics, 2011-02-28)
; ; ; ; ; ; ; ; We have characterized the emission spectrum and temporal history of a pure potassium plasma in a capillary discharge. Strong broadband emission was observed around 40 nm due to 3s−3p, 3p−3d, and 3d−4f transitions in ions ranging from K2+ to K4+ at a time-integrated electron temperature of about 12 eV. The temporal behavior of this emission strongly follows the recombination phase in the plasma and it was successfully reproduced by a hydrodynamic simulation of the potassium plasma which accounted for atomic processes.386Scopus© Citations 3 - PublicationFeasibility study of broad band efficient "water window" source(American Institute of Physics, 2012)
; ; ; ; ; ; We demonstrate a table-top broadband emission water window source based on laser-produced high-Z plasmas. Resonance emission from multiply charged ions merges to produce intense unresolved transition arrays in the 2 to 4 nm region, extending below the carbon K edge (4.37 nm). Arrays resulting from n = 4−4 transitions are overlaid with n = 4−5 emission and shift to shorter wavelength with increasing atomic number. From spectral analysis, a guideline for microscope construction design for single-shot live cell imaging is proposed based on the use of a bismuth plasma source, coupled with multilayer mirror optics.617Scopus© Citations 67 - PublicationGd plasma source modeling at 6.7 nm for future lithography(American Institute of Physics, 2011-12-05)
; ; ; ; ; ; ; Plasmas containing gadolinium have been proposed as sources for next generation lithography at 6.x nm. To determine the optimum plasma conditions, atomic structure calculations have been performed for Gd11+ to Gd27+ ions which showed that n=4 - n=4 resonance transitions overlap in the 6.5 – 7.0 nm region. Plasma modeling calculations, assuming collisional-radiative equilibrium, predict that the optimum temperature for an optically thin plasma is close to 110 eV and that maximum intensity occurs at 6.76 nm under these conditions. The close agreement observed between simulated and experimental spectra from laser and discharge produced plasmas indicates the validity of our approach.485Scopus© Citations 32 - PublicationTungsten spectra recorded at the LHD and comparison with calculations(IOP Science, 2010-10)
; ; ; ; ; ; ; ; ; ; ; We have measured extreme ultraviolet (EUV) spectra from highly charged tungsten ions in low-density and high-temperature plasmas produced in the Large Helical Device at the National Institute for Fusion Science. The EUV spectra emitted after injection of a tungsten pellet into a hydrogen plasma were recorded at plasma temperatures of 1.5 and 3 keV and were dominated by an intense transition array in the 4.5–6.5 nm region, the profile and extent of which was different in both spectra. Some discrete lines present were identified by comparison with existing spectral data while atomic structure calculations showed that the dominant emission in both arose from Δn = 0, n = 4–n = 4 transitions and the main differences could be attributed to the appearance of the 4p–4d and 4s–4p transitions from W XXXIX to W XLVI in the higher temperature spectrum. Comparison with calculations showed that the dominant emission in both temperature regimes arose from stages where the 4f subshell was either almost or completely stripped. We also investigated if the effect of low density favours transitions to the lowest level as observed in recently reported results.653Scopus© Citations 82 - PublicationThe effect of viewing angle on the spectral behavior of a Gd plasma source near 6.7 nm(American Institute of Physics, 2012)
; ; ; ; ; ; ; ; ; ; We have demonstrated the effect of viewing angle on the extreme ultraviolet (EUV) emission spectra of gadolinium (Gd) near 6.7 nm. The spectra are shown to have a strong dependence on viewing angle when produced with a laser pulse duration of 10 ns, which may be attributed to absorption by low ion stages of Gd and an angular variation in the ion distribution. Absorption effects are less pronounced at a 150-ps pulse duration due to reduced opacity resulting from plasma expansion. Thus for evaluating source intensity it is necessary to allow for variation with both viewing angle and target orientation.496Scopus© Citations 18 - PublicationMeasurement of EUV spectra from high Z elements in the Large Helical Device(American Institute of Physics, 2010-09-21)
; ; ; ; ; ; ; ; ; ; ; ; ; Extreme ultra-violet (EUV) emission spectra from highly charged tin, xenon and tungsten ions have been measured in optically thin high-temperature plasmas produced in the Large Helical Device (LHD) at the National Institute for Fusion Science by using a grazing incidence spectrometer and a tracer-encapsulated solid pellet (TESPEL) injector. Quasi-continuous spectral features arising from unresolved transition array (UTA) of open 4d subshell ions were commonly observed for tin, xenon and tungsten around 13.5, 11, and 5 nm, respectively, when edge plasma was cooled enough. The spectral appearance obviously depends on edge electron temperature and atomic number. In the case of intermediate edge temperature, sharp discrete lines from highly charged open 4s or 4p subshell ions are clearly observed for tin and xenon in longer wavelength side of the UTAs but not for tungsten. Assignments of the strong discrete lines have been performed with the help of comparisons with the other experimental data and the theoretical calculations by Cowan code. Contribution of open 4f subshell ions should also be considered to interpret the whole spectra from tungsten ions.324Scopus© Citations 2 - PublicationInterpretation of spectral emission around 20 nm region from tungsten ions observed in fusion device plasmas(Institute of Physics, 2011-08-24)
; ; ; ; ; ; ; ; ; ; ; ; ; We have measured extreme ultraviolet (EUV) spectra from tungsten ions around 20 nm region in plasmas produced in the Large Helical Device at the National Institute for Fusion Science. The spectra after injecting a tungsten pellet into a hydrogen plasma were monitored by a grazing incidence spectrometer. Quasicontinuum spectral feature arising from unresolved transition array (UTA) was observed around 20 nm region in plasmas with temperatures below 1.0 keV. This structure is reasonably considered to be the same one as those observed in another tokamak device or laser produced plasmas under low temperature conditions. Atomic structure calculations have been performed for tungsten ions with open 5p, 5s and 4f subshells (W7+–W27+) to interpret this commonly observed feature around 20 nm. Wavelengths and gA values for these transitions were calculated, and their mean wavelengths and extent were compared with the observations, which suggests that the emission largely arises from n = 5–5 transitions in stages lower than W27+.225Scopus© Citations 26 - PublicationScaling of laser produced plasma UTA emission down to 3 nm for next generation lithography and short wavelength imaging(Society of Photo-optical Instrumentation Engineers, 2011-08-22)
; ; ; ; ; ; ; ; ; ; ; An engineering prototype high average power 13.5-nm source has been shipped to semiconductor facilities to permit the commencement of high volume production at a 100 W power level in 2011. In this source, UTA (unresolved transition array) emission of highly ionized Sn is optimized for high conversion efficiency and full recovery of the injected fuel is realized through ion deflection in a magnetic field. By use of a low-density target, satellite emission is suppressed and full ionization attained with short pulse CO2 laser irradiation. The UTA is scalable to shorter wavelengths, and Gd is shown to have similar conversion efficiency to Sn (13.5 nm) at a higher plasma temperature, with a narrow spectrum centered at 6.7 nm, where a 70% reflectivity mirror is anticipated. Optimization of short pulse CO2 laser irradiation is studied, and further extension of the same method is discussed, to realize 100 W average power down to a wavelength of 3 nm603Scopus© Citations 9 - PublicationConfiguration Interaction in Charge Exchange Spectra of Tin and Xenon(IOP Publishing, 2011)
; ; ; ; ; ; ; ; ; ; ; Charge state specific extreme ultraviolet spectra from both tin ions and xenon ions have been recorded at Tokyo Metropolitan University. The Electron Cyclotron Resonance Source spectra were produced from charge exchange collisions between the ions and rare gas target atoms. In order to identify unknown spectral lines of tin and xenon, atomic structure calculations were performed for Sn14+ - Sn17+ and for Xe 16+ - Xe20+ using the Hartree-Fock with Configuration Interaction code of Cowan. The energies of the capture states involved in the single electron process that occurs in these slow collisions are estimated using the classical over barrier model.686Scopus© Citations 2