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Title: Diagnostic Development for ST Plasmas on NSTX

Abstract

Spherical tokamaks (STs) have much lower aspect ratio (a/R) and lower toroidal magnetic field, relative to tokamaks and stellarators. This paper will highlight some of the challenges and opportunities these features pose in the diagnosis of ST plasmas on the National Spherical Torus Experiment (NSTX), and discuss some of the corresponding diagnostic development that is underway. The low aspect ratio necessitates a small center stack, with tight space constraints and large thermal excursions, complicating the design of magnetic sensors in this region. The toroidal magnetic field on NSTX is less than or equal to 0.6 T, making it impossible to use ECE as a good monitor of electron temperature. A promising new development for diagnosing electron temperature is electron Bernstein wave (EBW) radiometry, which is currently being pursued on NSTX. A new high-resolution charge exchange recombination spectroscopy system is being installed. Since non-inductive current initiation and sustainment ar e top-level NSTX research goals, measurements of the current profile J(R) are essential to many planned experiments. On NSTX several modifications are planned to adapt the MSE technique to lower field, and two novel MSE systems are being prototyped. Several high speed 2-D imaging techniques are being developed, for viewing both visiblemore » and x-ray emission. The toroidal field is comparable to the poloidal field at the outside plasma edge, producing a large field pitch (>50{sup o}) at the outer mid-plane. The large shear in pitch angle makes some fluctuation diagnostics like beam emission spectroscopy very difficult, while providing a means of achieving spatial localization for microwave scattering investigations of high-k turbulence, which are predicted to be virulent for NSTX plasmas. A brief description of several of these techniques will be given in the context of the current NSTX diagnostic set.« less

Authors:
;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
814679
Report Number(s):
PPPL-3822
TRN: US0304307
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 16 Jun 2003
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASPECT RATIO; CHARGE EXCHANGE; DIAGNOSIS; ELECTRON TEMPERATURE; ELECTRONS; EMISSION SPECTROSCOPY; FLUCTUATIONS; INCLINATION; MAGNETIC FIELDS; MODIFICATIONS; MONITORS; RECOMBINATION; SPECTROSCOPY; STELLARATORS; VELOCITY; DIAGNOSTICS; LIGHT SCATTERING; OPTICAL SPECTROSCOPY; SPHERICAL TORUS; SPHERICAL TOKAMAK; THOMSON SCATTERING

Citation Formats

D. Johnson, and NSTX Team. Diagnostic Development for ST Plasmas on NSTX. United States: N. p., 2003. Web. doi:10.2172/814679.
D. Johnson, & NSTX Team. Diagnostic Development for ST Plasmas on NSTX. United States. doi:10.2172/814679.
D. Johnson, and NSTX Team. Mon . "Diagnostic Development for ST Plasmas on NSTX". United States. doi:10.2172/814679. https://www.osti.gov/servlets/purl/814679.
@article{osti_814679,
title = {Diagnostic Development for ST Plasmas on NSTX},
author = {D. Johnson and NSTX Team},
abstractNote = {Spherical tokamaks (STs) have much lower aspect ratio (a/R) and lower toroidal magnetic field, relative to tokamaks and stellarators. This paper will highlight some of the challenges and opportunities these features pose in the diagnosis of ST plasmas on the National Spherical Torus Experiment (NSTX), and discuss some of the corresponding diagnostic development that is underway. The low aspect ratio necessitates a small center stack, with tight space constraints and large thermal excursions, complicating the design of magnetic sensors in this region. The toroidal magnetic field on NSTX is less than or equal to 0.6 T, making it impossible to use ECE as a good monitor of electron temperature. A promising new development for diagnosing electron temperature is electron Bernstein wave (EBW) radiometry, which is currently being pursued on NSTX. A new high-resolution charge exchange recombination spectroscopy system is being installed. Since non-inductive current initiation and sustainment ar e top-level NSTX research goals, measurements of the current profile J(R) are essential to many planned experiments. On NSTX several modifications are planned to adapt the MSE technique to lower field, and two novel MSE systems are being prototyped. Several high speed 2-D imaging techniques are being developed, for viewing both visible and x-ray emission. The toroidal field is comparable to the poloidal field at the outside plasma edge, producing a large field pitch (>50{sup o}) at the outer mid-plane. The large shear in pitch angle makes some fluctuation diagnostics like beam emission spectroscopy very difficult, while providing a means of achieving spatial localization for microwave scattering investigations of high-k turbulence, which are predicted to be virulent for NSTX plasmas. A brief description of several of these techniques will be given in the context of the current NSTX diagnostic set.},
doi = {10.2172/814679},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jun 16 00:00:00 EDT 2003},
month = {Mon Jun 16 00:00:00 EDT 2003}
}

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