Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak
- Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
A profile for the critical gradient scale length (Lc) has been measured in L-mode discharges at the Alcator C-Mod tokamak, where electrons were heated by an ion cyclotron range of frequency through minority heating with the intention of simultaneously varying the heat flux and changing the local gradient. The electron temperature gradient scale length (LTe-1= |∇Te|/Te) profile was measured via the BT-jog technique and it was compared with electron heat flux from power balance (TRANSP) analysis. The Te profiles were found to be very stiff and already above the critical values, however, the stiffness was found to be reduced near the q = 3/2 surface. The measured Lc profile is in agreement with electron temperature gradient (ETG) models which predict the dependence of Lc-1 on local ,Zeff, Te/Ti, and the ratio of the magnetic shear to the safety factor. The results from linear Gene gyrokinetic simulations suggest ETG to be the dominant mode of turbulence in the electron scale (k⊥ρs > 1), and ion temperature gradient/trapped electron mode modes in the ion scale (k⊥ρs > 1). Finally, the measured Lc profile is in agreement with the profile of ETG critical gradients deduced from GENE simulations.
- Research Organization:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Texas, Austin, TX (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- FC02-99ER54512; FG03-96ER54373
- OSTI ID:
- 1540168
- Alternate ID(s):
- OSTI ID: 1432578
- Journal Information:
- Physics of Plasmas, Vol. 25, Issue 4; ISSN 1070-664X
- Publisher:
- American Institute of Physics (AIP)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Variable location channels to improve efficiency and precision for direct ∇ T e measurements and high spatial resolution T e -profile measurements using electron cyclotron emission
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journal | October 2018 |
Helical core formation and evolution during current ramp-up in the high-field tokamak Alcator C-Mod
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journal | February 2019 |
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