The two-dimensional structure of radiative divertor plasmas in the DIII-D Tokamak

Conference · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:508733

Fenstermacher, M E; Allen, S L ^[1]; Brooks, N H ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. General Atomics, San Diego, CA (United States); and others

Recent measurements of the 2-D spatial profiles of divertor plasma density, temperature, and emissivity in the DIII-D tokamak under highly radiating conditions are presented. Data are obtained using a Divertor Thomson Scattering system and other diagnostics optimized for measuring the high electron densities and low temperatures in these detached divertor plasmas (n{sub e} < 10{sup 21} m{sup -3}, 0.5 eV < T{sub e}). D{sub 2} puffing in the divertor increases the plasma radiation and lowers T{sub e} to less than 2 eV in most of the divertor volume. Modeling shows that this temperature is low enough to allow ion- neutral collisions, charge exchange, and volume recombination to play significant roles in reducing the plasma pressure along the magnetic separatrix by a factor of 3 to 5, consistent with the measurements. Absolutely calibrated VUV spectroscopy and 2-D images of impurity emission show that carbon radiation near the X-point, and deuterium radiation near the. plates contribute to the reduction in T{sub e}. Uniformity of outer leg radiated power (within a factor of 2) along the outer divertor leg, with @ target heat flux on the divertor target reduced four-fold, was obtained. A comparison with 2-D fluid simulations shows good agreement when physical sputtering and an ad hoc chemical sputtering source (0.5%) from the private flux region surface is used.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 508733
• Report Number(s): UCRL-JC--125494; CONF-961102--11; ON: DE97052671
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DIVERTORS
PLASMA DIAGNOSTICS
TOKAMAK DEVICES