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Title: Radial ion transport in a nonaxisymmetric magnetic mirror

Abstract

An experimental study of radial ion transport in a nonaxisymmetric magnetic mirror is presented. It is found that the ion confinement time perpendicular to the magnetic field is an order of magnitude shorter than predicted by classical and neoclassical theories, and that radial transport can be the dominant ion loss mechanism. Transport experiments are performed in hydrogen, helium and argon plasmas by measuring equilibrium radial profiles of plasma density, ionization source, end loss current, electric field, electron temperature and ion temperature. The radial profiles of the perpendicular diffusion coefficient (D/perpendicular/) are presented, and range from a radial average of approx. =5 /times/ 10/sup 3/ cm/sup 2//sec for hydrogen to approx. =2 /times/ 10/sup 4/ cm/sup 2//sec for argon. These coefficients are a factor of ten larger than the maximum possible classical and neoclassical diffusion coefficients in all three gases. The effect of low frequency RF power in the ion cyclotron range on the radial ion transport rate is also investigated. RF power increases the ion perpendicular transport, which then becomes the dominant loss mechanism. With sufficient RF power, the ion perpendicular loss rate exceeds the ionization source, with a resultant loss of plasma equilibrium. Application of RF power increases themore » radial transport rate of plasmas with resonant ions, which are also heated by the RF waves, as well as plasmas whose ion cyclotron resonance is not inside the confinement region. The increased transport rate during application of RF power shows up as an increased D/perpendicular/. This indicates that the radial ion transport is due to a direct interaction between the ions and the RF field, rather than to radial profile changes or enhanced ambipolar potential which are other RF effects. The effect of RF power on plasma potential is also studied. 64 refs., 57 figs., 11 tabs.« less

Authors:
Publication Date:
Research Org.:
Massachusetts Inst. of Tech., Cambridge (USA). Plasma Fusion Center
OSTI Identifier:
6439456
Report Number(s):
DOE/ET/51013-264; PFC/RR-89-2
ON: DE89008760; TRN: 89-009279
DOE Contract Number:  
AC02-78ET51013
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis (Ph.D.). Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; MAGNETIC MIRROR CONFIGURATIONS; CHARGED-PARTICLE TRANSPORT; ASYMMETRY; CONFINEMENT TIME; ELECTRON TEMPERATURE; ION TEMPERATURE; IONIZATION; PLASMA DIAGNOSTICS; RF SYSTEMS; TEMPERATURE MEASUREMENT; MAGNETIC FIELD CONFIGURATIONS; OPEN CONFIGURATIONS; RADIATION TRANSPORT; 700103* - Fusion Energy- Plasma Research- Kinetics

Citation Formats

Goodman, D L. Radial ion transport in a nonaxisymmetric magnetic mirror. United States: N. p., 1989. Web.
Goodman, D L. Radial ion transport in a nonaxisymmetric magnetic mirror. United States.
Goodman, D L. Wed . "Radial ion transport in a nonaxisymmetric magnetic mirror". United States.
@article{osti_6439456,
title = {Radial ion transport in a nonaxisymmetric magnetic mirror},
author = {Goodman, D L},
abstractNote = {An experimental study of radial ion transport in a nonaxisymmetric magnetic mirror is presented. It is found that the ion confinement time perpendicular to the magnetic field is an order of magnitude shorter than predicted by classical and neoclassical theories, and that radial transport can be the dominant ion loss mechanism. Transport experiments are performed in hydrogen, helium and argon plasmas by measuring equilibrium radial profiles of plasma density, ionization source, end loss current, electric field, electron temperature and ion temperature. The radial profiles of the perpendicular diffusion coefficient (D/perpendicular/) are presented, and range from a radial average of approx. =5 /times/ 10/sup 3/ cm/sup 2//sec for hydrogen to approx. =2 /times/ 10/sup 4/ cm/sup 2//sec for argon. These coefficients are a factor of ten larger than the maximum possible classical and neoclassical diffusion coefficients in all three gases. The effect of low frequency RF power in the ion cyclotron range on the radial ion transport rate is also investigated. RF power increases the ion perpendicular transport, which then becomes the dominant loss mechanism. With sufficient RF power, the ion perpendicular loss rate exceeds the ionization source, with a resultant loss of plasma equilibrium. Application of RF power increases the radial transport rate of plasmas with resonant ions, which are also heated by the RF waves, as well as plasmas whose ion cyclotron resonance is not inside the confinement region. The increased transport rate during application of RF power shows up as an increased D/perpendicular/. This indicates that the radial ion transport is due to a direct interaction between the ions and the RF field, rather than to radial profile changes or enhanced ambipolar potential which are other RF effects. The effect of RF power on plasma potential is also studied. 64 refs., 57 figs., 11 tabs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1989},
month = {2}
}

Technical Report:
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