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

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 q 95 ~ 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 × 10 20/m 3. 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.
ORCiD logo [1] ;  [2] ;  [3] ; ORCiD logo [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2] ;  [1]
  1. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC02-09CH11466; FC02-99ER54512
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 5; Journal ID: ISSN 0029-5515
IOP Science
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
Contributing Orgs:
the Alcator C-Mod Team
Country of Publication:
United States
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; helium discharge; ITER; ELMy H-mode
OSTI Identifier: