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Sokell, Emma
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Sokell, Emma
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Sokell, Emma
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Now showing 1 - 6 of 6
- 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.285Scopus© Citations 51 - 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 - PublicationWhat elements of a community help undergraduates gain confidence?(2019-07-24)
; ; ; ; ; Women's underrepresentation in the field of physics continues to be an issue, in part because of the perceptions women may have about their abilities to study physics. In this paper, we will study undergraduate students' perceptions about the required level of competence for studying physics, and how these perceptions may change due to participation in spaces that support competence building. We use a mixed methods approach to look at survey responses collected from students on the Foundations of physics course at University College Dublin, and interviews with physics undergraduate facilitators of an informal program that explore the overlaps of physics and music. We hypothesise, that female students perceive the required level of competence to study physics to be higher than male students. We propose that providing formal and informal spaces that support competence building will improve undergraduate students' perceptions of their competence to study physics.101 - PublicationOptimizing conversion efficiency and reducing ion energy in a laser-produced Gd plasma(American Institute of Physics, 2012)
; ; ; ; ; ; ; ; ; ; We have demonstrated an efficient extreme ultraviolet (EUV) source at 6.7 nm by irradiating Gd targets with 0.8 and 1.06 μm laser pulses of 140 fs to 10 ns duration. Maximum conversion efficiency of 0.4% was observed within a 0.6% bandwidth. A Faraday cup observed ion yield and time of flight signals for ions from plasmas generated by each laser. Ion kinetic energy was lower for shorter pulse durations, which yielded higher electron temperatures required for efficient EUV emission, due to higher laser intensity. Picosecond laser pulses were found to be the best suited to 6.7 nm EUV source generation.625Scopus© Citations 42 - 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