Options
O'Sullivan, Gerry
Preferred name
O'Sullivan, Gerry
Official Name
O'Sullivan, Gerry
Research Output
Now showing 1 - 7 of 7
- 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.Scopus© Citations 83 772 - PublicationUTA versus line emission for EUVL : studies on xenon emission at the NIST EBIT(IOP Publishing, 2004-12)
; ; ; ; ; ; ; ; ; ; ; Spectra from xenon ions have been recorded at the NIST EBIT and the emission into a 2% bandwidth at 13.5 nm arising from 4d_5p transitions compared with that from 4d_4f and 4p_4d transitions in Xe XI and also with that obtained from the unresolved transition array (UTA) observed to peak just below 11 nm. It was found that an improvement of a factor of five could be gained in photon yield using the UTA rather than the 4d_5p emission. The results are compared with atomic structure calculations and imply that a significant gain in efficiency should be obtained using tin, in which the emission at 13.5 nm comes from a similar UTA, rather than xenon as an EUVL source material.Scopus© Citations 52 380 - PublicationSystematic investigation of self-absorption property and conversion efficiency of 6.7-nm extreme ultraviolet sources(American Institute of Physics, 2010-12)
; ; ; ; ; ; ; ; ; We have demonstrated rare-earth plasma extreme ultraviolet sources at 6.7 nm to investigate the spectral behavior and the conversion efficiencies to different laser wavelength and the initial target densities. The conversion efficiency was maximized to be 0.9% at laser intensity of 7 × 1012 W/cm2 at its wavelength of 1064 nm, which is attributed to the minimum self-absorption effect by use of the low initial density target, together with the narrow spectrum. It is important to use a low initial density target and to produce low electron density plasmas for efficient EUV sources using the high-Z targets.499Scopus© Citations 54 - 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.Scopus© Citations 3 453 - 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 nmScopus© Citations 9 674 - 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.Scopus© Citations 3 797 - 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.394