Tomographic reconstruction of two-dimensional radiated power distribution during impurity injection in KSTAR plasmas using an infrared imaging video bolometer

Jang, Juhyeok; Choe, Wonho; Peterson, B.J.; Seo, D. C.; Mukai, K.; Sano, Ryuichi; Oh, Seungtae; Hong, Suk–Ho; Hong, Jin; Lee, H.Y.

doi:10.1016/j.cap.2018.01.009

Cited by 22 publications

(16 citation statements)

References 23 publications

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“…Especially for the understanding of the plasma radiation distribution during impurity seeding [2], used to reduce the heat load on the divertor through enhanced radiation, two-dimensional (2D) radiation profiles, obtained through tomographic inversion of line averaged signals from collimated bolometer detectors [3]- [5], will play the main role. The resistive bolometer is a standard diagnostic and will be installed in ITER as the main bolometer diagnostic [6].…”

Section: Introductionmentioning

confidence: 99%

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Peterson¹,

Nishitani²,

Reichle³

et al. 2022

J. Inst.

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Imaging bolometers have been studied for ITER to serve as a complementary diagnostic to the resistive bolometers for the measurement of radiated power. Two tangentially viewing InfraRed imaging Video Bolometers (IRVB) could be proposed for an ITER equatorial port, one having a view of the entire plasma cross-section (core viewing) and one tilted down 43 degrees from the horizontal to view the divertor (divertor viewing). The IRVBs have 7 cm (horizontal) by 9 cm (vertical) Pt sensor foils, 6 mm × 6 mm apertures, 15 × 20 pixels and focal lengths of 7.8 cm and 21 cm, respectively. Using SANCO and SOLPS models for a 840 m3 plasma radiating 67.3 MW, synthetic images from the IRVBs are calculated to estimate the maximum signal strengths to be 246 W/m2 and 62 W/m2, respectively. We propagate the X-ray energy spectra from the models through the synthetic diagnostics to give the photon energy spectrum for each IRVB pixel, which are used to calculate the fraction of the power absorbed by the foil as a function of foil thickness. Using a criteria of >95% absorbed power fraction, we selected foil thicknesses of 30 μm and 10 μm, respectively. We used these thicknesses and assumed IR systems having 105 fps, 1024×1280 pixels and sensitivities of 15 mK, to calculate the IRVB sensitivities of 3.19 W/m2 and 1.05 W/m2, and signal to noise ratios of 77 and 59, respectively. Using the Monte Carlo Nuclear Particle code we calculated for the core viewing IRVB the foil heating by neutrons to be 1.0 W/m2 and by gammas to be 117 W/m2. This indicates that countermeasures may be needed to remove the nuclear heating signal.

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Section: Introductionmentioning

confidence: 99%

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Peterson¹,

Nishitani²,

Reichle³

et al. 2022

J. Inst.

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“…Langmuir probe arrays on the divertor targets were used to measure the ion saturation current density, and a divertor infrared television (IRTV) system with high resolution was used to measure the heat flux on the outer target [24]. Tangentially reconstructed two-dimensional radiated power distributions were obtained using an infrared imaging video bolometer (IRVB) [25,26].…”

Section: Discharge With Argon Seeding In the Presence Of Rmp-driven E...mentioning

confidence: 99%

Argon–seeded detachment during ELM control by RMPs in KSTAR

et al. 2023

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In this study, we demonstrate argon-seeded discharges that exhibited a detached divertor during the full suppression and mitigation of edge localized modes (ELMs) by an ITER-like, three-row resonant magnetic perturbation (RMP) configuration in KSTAR. During the ELM suppression phase, the peak heat flux on the divertor target was successfully reduced from 1.6 MW/m2 to 0.5 MW/m2 via argon seeding. Further, the ion saturation current densities corresponding to the particle fluxes on both targets were reduced by more than 50%. During the RMP grassy-ELM regime, a further reduction to 0.1 MW/m2 in the divertor heat load was successfully achieved. A highly localized radiation zone near the x-point was also observed during divertor detachment. The calculated degree of detachment (DoD) based on the two-point model increased to levels of approximately 3 and 2.3 for the outer target and inner target cases, respectively. These results provide valuable information regarding the effect of mid-Z impurities on RMP-detachment-compatible discharges.

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“…In KSTAR, several imaging diagnostics with tomographic reconstruction algorithms have been developed for impurity transport study [8][9][10][11], including the tungsten powder injection experiment. However, both the vacuum (VUV) and extreme ultraviolet (EUV) spectrometers [10,12] on KSTAR and the one planned for ITER [13], which have a capability of resolving the spatial distribution of line emissions, suffer from a limited viewing angle due to the narrow allocated space, which makes it difficult to accurately reconstruct the local emissivity profile of each line radiation from the chordintegrated data.…”

Section: Local Profiles Of Line Emission Of Impurity Ions In Rotating...mentioning

confidence: 99%

Local profiles of line emission of impurity ions in rotating fusion plasmas

2020

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We analyze the poloidal distribution of impurity ions, such as C V, C VI and O VIII, in fast rotating KSTAR plasmas using the impurity emission lines in the 1–7 nm wavelength range obtained from the space-resolved extreme ultra violet spectrometer. This is aided particularly by a new tomographic reconstruction technique with limited viewing angles. The vacuum and extreme ultraviolet spectrometer system at ITER and its prototypes installed at KSTAR are one of the main diagnostic systems to monitor the impurity species in fusion plasmas; however, they have an insufficient field of view to utilize the conventional reconstruction method. The new algorithm developed in this work considers a curvilinear grid of pixels mapped onto the magnetic equilibrium and a weight factor considering toroidal rotational effect on impurity species. Validation tests with poloidally asymmetric images of synthetic plasma demonstrate that this method is highly useful for emission diagnostics that have a narrow field of view. The experimental results of the spatially resolved spectra from KSTAR plasma clearly show that even the light impurities such as carbon and oxygen are significantly affected by the toroidal rotation. Accordingly, the method is expected to be utilized for estimating the poloidal density profile of each charge state of an impurity species, which will play a key role in impurity transport studies.

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Tomographic reconstruction of two-dimensional radiated power distribution during impurity injection in KSTAR plasmas using an infrared imaging video bolometer

Cited by 22 publications

References 23 publications

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Estimates of foil thickness, signal, noise, and nuclear heating of imaging bolometers for ITER

Argon–seeded detachment during ELM control by RMPs in KSTAR

Local profiles of line emission of impurity ions in rotating fusion plasmas

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