Helium experiments on Alcator C-Mod in support of ITER early operations

Kessel, C. E.; Wolfe, S. M.; Reinke, M. L.; Hughes, J. W.; Lin, Y.; Wukitch, S. J.; Baek, S. G.; Bonoli, P. T.; Chilenski, M.; Diallo, A.

doi:10.1088/1741-4326/aab1b7

Helium experiments on Alcator C-Mod in support of ITER early operations

Journal Article · Tue Mar 13 00:00:00 EDT 2018 · Nuclear Fusion

DOI:https://doi.org/10.1088/1741-4326/aab1b7· OSTI ID:1432049

^[1]; Wolfe, S. M. ^[2]; Reinke, M. L. ^[3]; ^[2]; Lin, Y. ^[2]; Wukitch, S. J. ^[2]; Baek, S. G. ^[2]; Bonoli, P. T. ^[2]; Chilenski, M. ^[2]; Diallo, A. ^[1]

Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Helium majority experiments on Alcator C-Mod were performed to compare with deuterium discharges, and inform ITER early operations. ELMy H-modes were produced with a special plasma shape at B_T = 5.3 T, I _P = 0.9 MA, at q₉₅ ~ 3.8. The He fraction ranged over, n _He,L/n_L = 0.2–0.4, with n _D,L/n _L = 0.15–0.26, compared to D plasmas with n _D,L/n _L = 0.85–0.97. The power to enter the H-mode in He was found to be greater than ~2 times that for D discharges, in the low density region <1.4 × 10²⁰/m³. However, it appears to follow the D threshold for higher densities. The stored energies in the He discharges were about 80% of those in D, and about 40% higher net power was required to sustain them compared to D. Global particle confinement times for tungsten of $$\tau _{{\rm W}}^{{\rm *}}$$ /τ _E ~ 4 were obtained with ELMy H-modes in He, however accumulation occurred when the ELMs were irregular and infrequent. The electron temperatures and densities in the pedestal were similar between D and He discharges, and the ΔT _e/T _e and Δn _e/n _e values were similar or larger in He than D. The higher net power required to access the H-mode, and sustain it in flattop, for He discharges in C-Mod, imply some limitations for He operation in ITER.

View Accepted Manuscript (DOE)

Research Organization:: Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: the Alcator C-Mod Team

Grant/Contract Number:: AC02-09CH11466; FC02-99ER54512

OSTI ID:: 1432049

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 5 Vol. 58; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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