Effect of boronization in VEST: Achieving 0.1 MA discharge

Yang, Joon-Mo; Hong, Suk–Ho; Kim, D.; Jang, Jae Young; Kim, J.Y.; Jung, E.C.; Kim, Yeonjoo; Hwang, Y.S.

doi:10.1016/j.fusengdes.2018.10.021

Cited by 5 publications

(3 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To assess the impact of impurity line emissions on the calculated R(T e ) curve used in the two-filter method, X-ray spectra from specific elements in the plasma were simulated using the FLYCHK code [22]. This calculation was performed under the assumption of the typical experimental condition in VEST after boronization, which is 1% composition of carbon and oxygen along with a plasma density of 10 19 m −3 [23]. When we simulated X-ray spectra from plasma using a steady-state ionization balance [24], the transport and effective residence time of the impurity species were neglected.…”

Section: Consideration Of Error Contribution From Impurity Line Emiss...mentioning

confidence: 99%

“…To measure soft X-rays, multichannel absolute extreme ultraviolet (AXUV) photodiodes with sensitivity at less than 1 keV are used in this study. With the multichannel measurements, T e profiles can be Sensors 2023, 23, 8357 2 of 12 inferred directly from the ratio of the intensity levels of the SXR signals measured from the identical line-of-sight (LOS) but through different filters. We designed the system to measure temperatures around 10-200 eV for VEST, suggested by previous measurements using the existing Thomson scattering system and triple probe.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electron Temperature Measurements Using a Two-Filter Soft X-ray Array in VEST

Lee,

Lim,

Jeong

et al. 2023

Sensors

View full text Add to dashboard Cite

A multichannel soft X-ray (SXR) array has been developed to measure the electron temperature in the Versatile Experiment Spherical Torus (VEST). To estimate electron temperature using the two-filter method applied to SXR intensity, we designed a pinhole camera that has two photodiode arrays with different metallic filters. We also adopted a filter wheel and tested various filter parameters to find the optimal filter set. Through tests, the combination of aluminum and beryllium was found to be the most suitable for the current experimental conditions in VEST. The filtered SXR signals were acquired with a low-noise preamplifier, exhibiting sufficient signal-to-noise ratios for electron temperature estimation based on the intensity ratio of two signals obtained with different filters. The estimated electron temperature from the developed two-filter SXR array showed reasonably matched levels and consistent trends with Thomson scattering measurements. Error contribution from impurity line emission is also discussed.

show abstract

Section: Consideration Of Error Contribution From Impurity Line Emiss...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electron Temperature Measurements Using a Two-Filter Soft X-ray Array in VEST

Lee,

Lim,

Jeong

et al. 2023

Sensors

View full text Add to dashboard Cite

show abstract

“…High density and low impurity influx to achieve high performance are required for major IREs in VEST. To achieve such conditions, a boronization technique after the glow discharge cleaning is applied [21].…”

Section: Vest Parameters and Diagnosticsmentioning

confidence: 99%

Observation of MHD-correlated blobs during internal reconnection events in VEST

Jung¹,

Na²,

Kim³

et al. 2022

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

Internal reconnection events (IREs), one of the relaxation events driven by internal magnetohydrodynamic (MHD) instabilities in fusion plasmas, are accompanied by a strongly MHD-correlated blob at the edge in the VEST spherical tokamak. The MHD-correlated blob plays a significant role in the onset and the strength of IREs. Various techniques analyzing visible camera images show correlated waveforms between blobs and magnetic fluctuations, and they produce visualized images of corotating structures of the MHD modes and the MHD-correlated blobs. In the images, a phase drag in the rotations of the two structures initially appears and vanishes on the verge of IREs. IREs maintaining the phase drag, however, leads to a less violent impact in terms of current decrease and magnetic field bursting. In addition, the MHD-correlated blobs are followed by the increasing degree of nonlinear interactions between the internal MHD mode and high-frequency broadband fluctuations (> 60 kHz) at the edge. These results suggest that boundary plasmas can impact internally driven relaxation events via MHD-correlated edge phenomena.

show abstract