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Title: The Physics of Confinement Improvement with Impurity Seeding in DIII-D

The Physics of Confinement Improvement with Impurity Seeding in DIII-D Clear increases in confinement (from H{sub 89P} {approx} 1 to H{sub 89P} {<=} 2) and simultaneous reductions of long-wavelength turbulence have been observed in L-mode discharges in DIII-D, which are directly correlated with external impurity injection [1]. These observations provide an opportunity to understand the mechanism for confinement improvement with impurity seeding observed in a number of tokamaks [2], and to make quantitative tests of theory-based turbulence and transport models with experimental measurements. Impurity seeding can be used not only to produce a radiative mantle to reduce heat fluxes to the first wall material [3], but also as a tool to control profiles in Advanced Tokamak (AT) plasmas. Significant confinement improvements are observed with injection of noble gases (Ne, Ar, and Kr) into L-mode edge, negative central shear (sawtooth-free) discharges in DIII-D. Compared to similar reference discharges without impurity injection, confinement enhancement factor and neutron emission in neon-injected discharges are nearly doubled [Fig. 1(a,b)]. The ion and electron temperature with neon injection exhibit increased central values and profile broadening while the electron density profile becomes more peaked.
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Publication Date:
OSTI Identifier:OSTI ID: 766728
Report Number(s):GA-A23443
TRN: US0109347
DOE Contract Number:AC03-99ER54463; AC05-00OR22725; AC02-76CH03073; W-7405-ENG-48; FG03-86ER53225; FG03-95ER54294; FG03-96ER54373; FG03-97ER54415; FG03-92ER54141
Resource Type:Conference
Resource Relation:Conference: 27th European Physical Society Conference on Controlled Fusion and Plasma Physics, Budapest (HU), 06/12/2000--06/16/2000; Other Information: PBD: 1 Aug 2000
Research Org:General Atomics, San Diego, CA (US)
Sponsoring Org:US Department of Energy (US)
Country of Publication:United States
Language:English
Subject: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; L-MODE PLASMA CONFINEMENT; DOUBLET-3 DEVICE; ELECTRON DENSITY; ELECTRON TEMPERATURE; FIRST WALL; NEUTRON EMISSION; RARE GASES; TURBULENCE; ION TEMPERATURE; GAS INJECTION; NEON