Three new extreme ultraviolet spectrometers on NSTX-U for impurity monitoring

Abstract

Three extreme ultraviolet (EUV) spectrometers have been mounted on the National Spherical Torus Experiment-Upgrade (NSTX-U). All three are flat-field grazing-incidence spectrometers and are dubbed X-ray and Extreme Ultraviolet Spectrometer (XEUS, 8-70 Å), Long-Wavelength Extreme Ultraviolet Spectrometer (LoWEUS, 190-440 Å), and Metal Monitor and Lithium Spectrometer Assembly (MonaLisa, 50-220 Å). XEUS and LoWEUS were previously implemented on NSTX to monitor impurities from low- to high-Z sources and to study impurity transport while MonaLisa is new and provides the system increased spectral coverage. The spectrometers will also be a critical diagnostic on the planned laser blow-off system for NSTX-U, which will be used for impurity edge and core ion transport studies, edge-transport code development, and benchmarking atomic physics codes.

Intercombination Transitions in the n = 4 Shell of Zn-, Ga-, and Ge-Like Ions of Elements Kr through Xe

“…However, since the electron beam ion trap was operated with a continuous influx of neutral Xe gas (under high-vacuum conditions), as well as cycled every so often to remove unwanted heavy-element contaminants, all lower charge states of Xe are expected to be present, but in small amounts. This spectrum has been dispersed with the moderate resolution LoWEUS spectrograph (Long-wavelength Extreme Ultraviolet Spectrometer) [64,65], covering a range roughly from 20 to 45 nm, which extends the study by Biedermann et al [60] considerably in wavelength, but (so far) without the systematic variation of the electron beam energy. The shortest-wavelength (unidentified) line at 21.118 nm is also seen in second order at 42.230 nm, and so are the mountains of blended lines at the adjacent longer wavelengths.…”

Emission Lines of Fe xiv, Fe xv, and Fe xvi in the Extreme Ultraviolet Region 40–100 Å

“…Spectra were measured with a grazing-incidence spectrometer described by Beiersdorfer et al (1999a) employing an average 1200 line/mm flat-field grating developed by Harada & Kita (1980;Nakano et al 1984) with a 3°angle of incidence. Similar instruments from LLNL have also been installed at the National Spherical Torus Experiment (Graf et al 2008;Lepson et al 2010;Weller et al 2016), the Alcator C-Mod tokamak (Reinke et al 2010;Lepson et al 2012), and the DIII-D tokamak (Victor et al 2017). Readouts were taken with a backilluminated, liquid nitrogen-cooled CCD camera with a 1-inch square array of 1024 × 1024 pixels and a resolving power, E/ ΔE, of ∼300 at 100 Å.…”

EUV Beam-Foil Spectra of Titanium, Iron, Nickel, and Copper

“…The experiment required about a day (and night) of accelerator time. The EBIT experiment [28,29] used a grazingincidence flat-field spectrograph (variable line-spacing grating of R = 5 m and approximately 1200 L/mm) [110,111]; the spectrum was recorded on a CCD chip with an exposure time of 30 min. The spectrograph has no entrance slit but images the 60 µm wide zone of the stored ion cloud exposed to the energetic electron beam directly onto the detector.…”

“…As mentioned above in the subsection on Fe, high-resolution nickel spectra have been recorded at the Livermore electron beam ion trap EBIT (see, for example, [27]). The spectrograph used [112] produced highly resolved spectra of wavelength bands that matched the individual detection bands of the SolarDynamicsObservatory spacecraft, but it did not permit observation beyond wavelengths of about 25 nm, where a smaller, mediumresolution flat-field spectrograph [110,111] was employed instead [28,29]. The spectra obtained with this instrument are close in resolution to the beam-foil survey spectra of Ni [56] that have been discussed above.…”