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Artificial Events: Area Events
Published in Maurizio Cumo, Antonio Naviglio, Safety Design Criteria for Industrial Plants, 2019
Hydrogen lines, in areas housing safety-related equipment, should be either seismically designed or sleeved such that the outer pipe be directly vented to the outside, or should be equipped with excess flow valves.
A Spectrochemical Snapshot of Heavy Elements in Nile River Sediments: Line Intensity Calculation
Published in Soil and Sediment Contamination: An International Journal, 2022
O. Aied Nassef, Yosr E. E.-D. Gamal
In laser-induced plasma, due to the collision of the emitters with the charged particles, the width of spectral lines is affected by the Stark-broadening effect, which is highly dependent on the electron density ne. It is assumed that the effect of the electronic collision is predominant, while the effect of the collision with the ions is much weaker. Carrying out LIBS experiments in ambient air at atmospheric pressure always results in hydrogen emission because of water vapor in the natural humidity of the air. It was reported that the Hα line (656.72 nm) could be beneficial in the calculation of plasma electron density since it has the advantage of providing a result which is not affected by self-absorption (Griem 1997). Moreover, the linear Stark effect acting on hydrogen lines results in a large broadening which reduces the relative uncertainty of the measurement compared with the case of lines emitted by other elements. The electron density has been calculated from the Hα line using: , where ne is the electron density (cm−3), Δλ is the measured FWHM of the Hα line (in Angstrom) and is the electron impact parameter, tabulated in Ref (Gigosos and Cardeñoso 1996).
Confirmation of the Absence of Contact Between Edge Boundary Plasma and Inboard First Wall in LHD Discharges Based on Radial Profile Measurement of Hβ Line Emissions
Published in Fusion Science and Technology, 2022
Yasuko Kawamoto, Shigeru Morita, Gakushi Kawamura, Motoshi Goto, Tetsutarou Oishi, Tomoko Kawate, Masahiro Kobayashi, Mamoru Shoji
Radial profiles of visible line emissions have been measured using a compact Czerny-Turner-type visible spectrometer (model MK-300, Bunkoukeiki Co. Ltd).11 The focal length of the spectrometer is 300 mm, and 40 optical fibers with a 100-μm core diameter are set just behind the entrance slit. A fan array consisting of the optical fibers is installed on the 7.5-L port in the LHD to observe the radial profile of line emissions at the vertically elongated plasma cross section. A schematic view of the observation chords is shown in Fig. 5. The widest observation angle of 18 deg is obtained by a combination of small lenses equipped with the fiber array to cover the whole plasma region, including the inboard side edge. A low-resolution grating of 300 grooves/mm has been used to observe a wide wavelength interval of the visible spectrum and to examine the time behaviors of the spectral lines in several impurity species in addition to hydrogen neutrals. Therefore, the spectral resolution of the observed line emissions was limited to a low value of Δλ = 17.1 Å. However, the spectral resolution was enough to measure the line emissions from the hydrogen neutrals because the intensity from the hydrogen lines, e.g., Hα (6563 Å: n = 3 to 2 transition) and Hβ (4861 Å: n = 4 to 2 transition) lines, are extremely strong compared to other visible impurity lines.
Temporal Profiling of Electron Temperatures Using the Hα–Hβ Line Emission and Triple Langmuir Probe Array in the Pre-Ionization Discharge of the MT-I Spherical Tokamak
Published in Fusion Science and Technology, 2020
M. Usman Naseer, F. Deeba, S. I. W. Shah, S. Hussain, A. Qayyum
This paper reports the development and testing of the spectroscopic and Langmuir probe system for plasma characterization in the MT-I Spherical Tokamak. The spectroscopic system includes the photodiodes masked with narrow-band filters to obtain the temporal profiles of Hα and Hβ line emissions from the hydrogen plasma discharge in the MT-I. However, at this stage only the pre-ionization phase has been diagnosed using selected hydrogen lines. The line ratio method has been used to calculate the temporal profile of electron temperature from the emission intensities of the Hα and Hβ line emissions having different excitation thresholds. A newly developed TLP array having three individual sets of probes, arranged radially, has been used to measure the temporal profile of electron temperature simultaneously at the edge. Additionally, a spectrometer HR4000+ is used to get the line-integrated emission intensity of the H-Balmer lines. It must be noted that the spectroscopic measurements are time and line averaged, so the temporal fluctuations are not reflected in the data obtained through the spectroscopic method, whereas in the case of an electric probe, these fluctuations are readily visible in the obtained data because of its ability to perform localized measurements at the edge.