Article
Physics, Fluids & Plasmas
S. B. Ballinger, D. Brunner, A. E. Hubbard, J. W. Hughes, A. Q. Kuang, B. LaBombard, J. L. Terry, A. E. White
Summary: This work presents new evidence on the scaling of heat flux width in the Alcator C-Mod tokamak and highlights the importance of volume-averaged pressure in predicting heat flux width. The study also identifies differences in the scaling trends between different confinement scenarios, which calls for further investigation.
Article
Physics, Fluids & Plasmas
D. Silvagni, J. L. Terry, W. McCarthy, A. E. Hubbard, T. Eich, M. Faitsch, L. Gil, T. Golfinopoulos, G. Grenfell, M. Griener, T. Happel, J. W. Hughes, U. Stroth, E. Viezzer
Summary: A study on pedestal relaxation events (PREs) in I-mode plasmas is conducted, revealing their relations with H-mode transition and precursor oscillation. The relative energy loss and electron temperature drop at the pedestal top decrease with increasing pedestal top collisionality. Based on these findings, projections of PRE divertor energy fluence to future devices are made. The model introduced for type-I edge localized modes provides an upper boundary for the energy fluence data.
Article
Instruments & Instrumentation
X. Y. Zhang, W. J. Qing, X. L. Zhang, S. D. Jiao, Q. Li, Y. H. Ding, L. Wang, Z. F. Cheng
Summary: The vacuum ultraviolet (VUV) spectroscopy system on the Joint Texas Experimental Tokamak has been upgraded to improve data acquisition speed and spatial resolution for the study of impurity transport in transient modulated experiments.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Physics, Fluids & Plasmas
A. R. Saperstein, R. A. Tinguely, R. S. Granetz, J. P. Levesque, M. E. Mauel, G. A. Navratil
Summary: This study investigates a new scaling law for disruption halo current rotation frequency based on measurements on Alcator C-Mod and HBT-EP. The new law takes into account the effect of MHD instability on the asymmetric rotation frequency and accurately describes the rotation frequency on C-Mod. The study also finds that disruption rotation is insensitive to the vertical position and impurity content of the plasma, but occasional stagnation in the time evolution of the rotation frequency is observed. The observations support the dominance of poloidal rotation as predicted by the scaling law.
PHYSICS OF PLASMAS
(2023)
Article
Chemistry, Multidisciplinary
Zihang Zhao, Ling Zhang, Ruijie Zhou, Yang Yang, Wenmin Zhang, Yunxin Cheng, Shigeru Morita, Ang Ti, Ailan Hu, Zhen Sun, Fengling Zhang, Weikuan Zhao, Zhengwei Li, Yiming Cao, Guizhong Zuo, Haiqing Liu
Summary: Plasma runaway or plasma disruptions frequently occur during plasma recovery after a vacuum failure, posing challenges in rebuilding a well-confined collisional plasma. This study investigated the impurity behavior during plasma recovery in the Experimental Advanced Superconducting Tokamak (EAST), and found a high content of low-Z impurities, such as oxygen and carbon, which may have caused subsequent runaway discharges. By analyzing EUV spectra, the electron temperature in the recovery discharge was estimated to have dropped to less than 75 eV when the plasma quenched to the runaway status. Real-time lithium granule injection effectively suppressed impurities and runaway electrons, extending the lifetime of confined plasma and improving plasma performance. These findings are valuable for future superconducting fusion devices.
APPLIED SCIENCES-BASEL
(2023)
Article
Nuclear Science & Technology
S. S. Henderson, M. Bernert, C. Giroud, D. Brida, M. Cavedon, P. David, R. Dux, J. R. Harrison, A. Huber, A. Kallenbach, J. Karhunen, B. Lomanowski, G. Matthews, A. Meigs, R. A. Pitts, F. Reimold, M. L. Reinke, S. Silburn, N. Vianello, S. Wiesen, M. Wischmeier
Summary: Current tokamak experiments are using real-time feedback control systems to manage plasma exhaust, while future tokamaks need validation of theoretical models predicting impurity concentration. New spectroscopic measurements show a correlation between divertor nitrogen concentration and power and separatrix electron density. Further analysis of measurement uncertainties and more consistent scenarios are needed to investigate machine size scaling.
NUCLEAR MATERIALS AND ENERGY
(2021)
Article
Optics
J. E. Rice, F. Sciortino, M. Gu, N. Cao, J. W. Hughes, J. H. Irby, E. S. Marmar, S. Mordijck, M. L. Reinke, R. Reksoatmodjo
Summary: X-ray transitions of the very high-n Rydberg series in Ar16+ have been observed, showing that the brightnesses of central chord lines decay as 1/n with principal quantum number n between 7 and 16, and transitions populated by charge exchange exhibit spatial up/down asymmetry. The brightness dependence on n below 16 is in excellent agreement with calculations from the flexible atomic code package.
JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
(2021)
Article
Physics, Fluids & Plasmas
S. G. Baek, B. Biswas, G. M. Wallace, P. T. Bonoli, B. J. Ding, M. H. Li, Y. C. Li, Y. F. Wang, M. Wang, C. B. Wu, G. H. Yan, J. Chen, X. Zhai, A. M. Garofalo, W. Choi, F. Poli, S. Shiraiwa
Summary: This study investigates the optimum rotation angle of the initial lower hybrid perpendicular wavevector to reproduce the centrally peaked current profile observed in normal shear plasmas on both EAST and C-Mod. The results show that increasing the initial poloidal component of the wavevector is effective in achieving this goal. The study also suggests that mitigation or control measures are critical for parasitic effects occurring in a reactor regime.
Article
Physics, Fluids & Plasmas
T. Nishizawa, R. Dux, R. M. McDermott, F. Sciortino, M. Cavedon, C. Schuster, E. Wolfrum, U. von Toussaint, A. Jansen Van Vuuren, D. J. Cruz-Zabala, P. Cano-Megias, C. Moon
Summary: This study presents a non-parametric inference method for determining impurity transport coefficients and applies it to measure these coefficients in a specific plasma. The results show the existence of large diffusion coefficients and strong outward convection in the plasma pedestal area.
Article
Chemistry, Analytical
Courtney A. Cruse, John Goodpaster
Summary: Gas chromatography/vacuum UV spectroscopy was used to study the gas phase VUV spectra of various nitrated compounds. The absorption characteristics of the nitro functional group were found to vary depending on the structure of the molecule, with different compounds exhibiting unique absorption patterns in the vacuum UV region. The diversity of the spectra analyzed could be reliably differentiated using PCA and LDA techniques.
ANALYTICA CHIMICA ACTA
(2021)
Article
Nuclear Science & Technology
A. Grosjean, D. C. Donovan, C. A. Johnson, J. P. Gunn, C. Guillemaut, N. Fedorczak, C. C. Klepper, E. A. Unterberg, West Team
Summary: WEST is an actively cooled, long-pulse tokamak that aims to study plasma operation with tungsten plasma-facing components (PFCs) in preparation for long-pulse operation on tungsten divertor devices like ITER. The sputtering of tungsten in low confinement mode (L-mode) operation is driven by light impurities (C, B, O, N) observed in trace levels in WEST. Identifying the main sources of tungsten and understanding its transport in the Scrape-Off Layer (SOL) are important for plasma performance and durability of PFCs.
NUCLEAR MATERIALS AND ENERGY
(2023)
Article
Physics, Fluids & Plasmas
Tetsutarou Oishi, Naoko Ashikawa, Federico Nespoli, Suguru Masuzaki, Mamoru Shoji, Eric P. Gilson, Robert Lunsford, Shigeru Morita, Motoshi Goto, Yasuko Kawamoto, Chihiro Suzuki, Zhen Sun, Alex Nagy, David A. Gates, Tomohiro Morisaki
Summary: The impurity powder dropper was installed in the 21st campaign of the Large Helical Device experiment for real-time wall conditioning and edge plasma control. Spectroscopic diagnostics were used to observe line emission from injected impurities, identifying emission lines from B and N ions with B and BN powder injection.
PLASMA SCIENCE & TECHNOLOGY
(2021)
Article
Physics, Fluids & Plasmas
V. A. Izzo
Summary: A study on dispersive shell pellet injections for disruption mitigation on the DIII-D tokamak was conducted using the 3D MHD code NIMROD. The simulations aimed to replicate a pellet velocity scan performed on the DIII-D tokamak, showing trends such as improved mitigation and increased likelihood of hot-tail runaway electron production with higher pellet speed. The simulations provided additional physics insights and discussed limitations of the current model and requirements for a predictive model.
PHYSICS OF PLASMAS
(2021)
Article
Physics, Fluids & Plasmas
F. Sciortino, N. T. Howard, R. Reksoatmodjo, A. R. Foster, J. W. Hughes, E. S. Marmar, M. A. Miller, S. Mordijck, T. Odstrcil, T. Putterich, M. L. Reinke, J. E. Rice, P. Rodriguez-Fernandez
Summary: Experimental inferences of cross-field impurity transport coefficients for AlcatorC-Mod plasmas show the impact of edge-localized modes on the results; consideration of line ratios across different spectral ranges improves accuracy of inferred coefficients; significant discrepancies in convection suggest difficulties in predicting flat or hollow impurity profiles.
Article
Physics, Fluids & Plasmas
Liang He, Yongcai Shen, Hongming Zhang, Bo Lyu, Cheonho Bae, Huajian Ji, Chaoyang Li, Jia Fu, Xuewei Du, Fudi Wang, Qiuping Wang, Xianghui Yin, Shunkuan Wan, Bin Bin, Yichao Li, Shuyu Dai
Summary: A space-resolved vacuum-ultraviolet (VUV) spectrometer is designed to measure impurity distribution in the divertor region of tokamaks, providing good spectral resolution and reduced aberration to meet the experimental requirements.
PLASMA SCIENCE & TECHNOLOGY
(2022)
Article
Instruments & Instrumentation
P. Beiersdorfer, E. W. Magee, G. V. Brown, H. Chen, J. Emig, N. Hell, M. Bitter, K. W. Hill, P. Allan, C. R. D. Brown, M. P. Hill, D. J. Hoarty, L. M. R. Hobbs, S. F. James
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
M. A. Leutenegger, P. Beiersdorfer, G. L. Betancourt-Martinez, G. V. Brown, N. Hell, R. L. Kelley, A. Kilbourne, E. W. Magee, F. S. Porter
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
G. V. Brown, P. Beiersdorfer, N. Hell, E. Magee
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
N. Hell, P. Beiersdorfer, E. W. Magee, G. V. Brown
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
M. E. Weller, P. Beiersdorfer, V. A. Soukhanovskii, E. W. Magee, F. Scotti
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
P. Beiersdorfer, E. W. Magee, N. Hell, G. V. Brown
REVIEW OF SCIENTIFIC INSTRUMENTS
(2016)
Article
Instruments & Instrumentation
B. S. Victor, S. L. Allen, P. Beiersdorfer, E. W. Magee
JOURNAL OF INSTRUMENTATION
(2017)
Article
Physics, Fluids & Plasmas
D. J. Hoarty, N. Sircombe, P. Beiersdorfer, C. R. D. Brown, M. P. Hill, L. M. R. Hobbs, S. F. James, J. Morton, E. Hill, M. Jeffery, J. W. O. Harris, R. Shepherd, E. Marley, E. Magee, J. Emig, J. Nilsen, H. K. Chung, R. W. Lee, S. J. Rose
HIGH ENERGY DENSITY PHYSICS
(2017)
Article
Instruments & Instrumentation
E. W. Magee, P. Beiersdorfer, G. V. Brown, N. Hell
REVIEW OF SCIENTIFIC INSTRUMENTS
(2014)
Article
Instruments & Instrumentation
T. E. Lockard, E. W. Magee, D. A. Layne, M. A. Leutenegger, M. E. Eckart, N. Hell, G. V. Brown, P. Beiersdorfer
REVIEW OF SCIENTIFIC INSTRUMENTS
(2018)
Article
Instruments & Instrumentation
N. Hell, T. Lockard, P. Beiersdorfer, E. W. Magee, G. V. Brown, R. Shepherd, T. Arthanayaka
REVIEW OF SCIENTIFIC INSTRUMENTS
(2018)
Article
Instruments & Instrumentation
P. Beiersdorfer, E. W. Magee, G. V. Brown, N. Hell, A. McKelvey, R. Shepherd, D. J. Hoarty, C. R. D. Brown, M. P. Hill, L. M. R. Hobbs, S. F. James, L. Wilson
REVIEW OF SCIENTIFIC INSTRUMENTS
(2018)
Article
Instruments & Instrumentation
M. J. MacDonald, K. Widmann, P. Beiersdorfer, N. Hell, D. J. Hoarty, E. W. Magee, C. Shah, R. Shepherd, G. V. Brown
Summary: The study presents absolute throughput analysis of several crystals for the OHREX spectrometer, including Ge(111), KAP, and different cuts of quartz, showing their high resolving power. The results indicate the potential for accurately measuring spectral line shapes using these crystals in the spectrometer.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Instruments & Instrumentation
N. Hell, P. Beiersdorfer, G. Brown, T. E. Lockard, E. W. Magee, R. Shepherd, D. J. Hoarty, C. R. D. Brown, M. P. Hill, L. M. R. Hobbs, S. F. James, C. Lynch, T. A. Caughey
Summary: The Orion high-resolution x-ray spectrometers have been successfully used in measuring x-ray spectra from plasmas, with recent improvements including optically bonded quartz crystals and the introduction of potassium acid phthalate (KAP) crystals. These improvements have significantly enhanced the accuracy and reliability of measurements conducted in various laboratories.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)
Article
Instruments & Instrumentation
M. E. Eckart, P. Beiersdorfer, G. V. Brown, D. J. Den Hartog, N. Hell, R. L. Kelley, C. A. Kilbourne, E. W. Magee, A. -E. Y. Mangoba, M. D. Nornberg, F. S. Porter, L. M. Reusch, J. P. Wallace
Summary: The NASA-built x-ray microcalorimeter spectrometer has been installed at the Wisconsin Plasma Physics Laboratory and recorded x-ray photons emitted by aluminum impurity ions in a deuterium plasma. The project aims to adapt these microcalorimeters for magnetic fusion energy research and showcase their value for fusion science. The spectrometers combine high spectral resolution with broadband coverage, providing valuable data for fusion experiments.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2021)