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Title: On the formation of large orbit proton rings by cusp injection

Abstract

This thesis research used an annular, applied-B, extraction ion diode and cusped magnetic field (the Megavolt Ion Coil Experiment) designed to produce ion rings whose parameters approach those desired for tilt stabilization of other plasma confinement devices. The work consisted of three principal parts: (1) Design, construction, and testing of a magnetic cusp-field to convert a cylindrical beam into a hollow rotating beam. This magnet has worked perfectly for over 5 years. (2) Detailed numerical investigations of single-particle trajectories in such cusp fields. These simulations indicate that unless the beam is more than 99% space-charge neutralized (more than previously realized), the ion beam will not propagate through the cusp field. Analysis of beam/gas interactions show that under these conditions, the only significant gas ionization mechanism is direct impact ionization. (3) Experimental investigation of an ion beam's behavior in traversing a cusp. Unfortunately, due to funding limitations, these experiments had to be terminated prematurely, and only a limited data base could be acquired. Comparison of these data to simulations without self-fields indicated significant discrepancies: if the full ion current was carried by protons, the calculated downstream beam diamagnetic signals were an order of magnitude higher than the observed signals, and themore » time width was approximately half the observed width. The principal conclusions reaches are: (1) The ion energy appears to be 10% to 15% lower than the measured applied voltage, perhaps due to charge-exchange effects in the diode. (2) Space-charge fields of only a few kV/cm in the cusp can cause enough axial drag and particle loss to reproduce the observed low levels of downstream signals. (3) The longer duration of the observed signals may have been caused by plasma currents driven in the beam-generated plasma, although the data are not definitive.« less

Authors:
Publication Date:
Research Org.:
Cornell Univ., Ithaca, NY (United States)
OSTI Identifier:
7279799
Resource Type:
Miscellaneous
Resource Relation:
Other Information: Thesis (Ph.D.)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CUSPED GEOMETRIES; ION BEAM INJECTION; ION RINGS; SYNTHESIS; TRAJECTORIES; BEAM INJECTION; MAGNETIC FIELD CONFIGURATIONS; OPEN CONFIGURATIONS; 700390* - Other Plasma Physics Studies- (1992-); 700380 - Elementary & Classical Processes in Plasmas- (1992-)

Citation Formats

Podulka, W J. On the formation of large orbit proton rings by cusp injection. United States: N. p., 1992. Web.
Podulka, W J. On the formation of large orbit proton rings by cusp injection. United States.
Podulka, W J. Wed . "On the formation of large orbit proton rings by cusp injection". United States.
@article{osti_7279799,
title = {On the formation of large orbit proton rings by cusp injection},
author = {Podulka, W J},
abstractNote = {This thesis research used an annular, applied-B, extraction ion diode and cusped magnetic field (the Megavolt Ion Coil Experiment) designed to produce ion rings whose parameters approach those desired for tilt stabilization of other plasma confinement devices. The work consisted of three principal parts: (1) Design, construction, and testing of a magnetic cusp-field to convert a cylindrical beam into a hollow rotating beam. This magnet has worked perfectly for over 5 years. (2) Detailed numerical investigations of single-particle trajectories in such cusp fields. These simulations indicate that unless the beam is more than 99% space-charge neutralized (more than previously realized), the ion beam will not propagate through the cusp field. Analysis of beam/gas interactions show that under these conditions, the only significant gas ionization mechanism is direct impact ionization. (3) Experimental investigation of an ion beam's behavior in traversing a cusp. Unfortunately, due to funding limitations, these experiments had to be terminated prematurely, and only a limited data base could be acquired. Comparison of these data to simulations without self-fields indicated significant discrepancies: if the full ion current was carried by protons, the calculated downstream beam diamagnetic signals were an order of magnitude higher than the observed signals, and the time width was approximately half the observed width. The principal conclusions reaches are: (1) The ion energy appears to be 10% to 15% lower than the measured applied voltage, perhaps due to charge-exchange effects in the diode. (2) Space-charge fields of only a few kV/cm in the cusp can cause enough axial drag and particle loss to reproduce the observed low levels of downstream signals. (3) The longer duration of the observed signals may have been caused by plasma currents driven in the beam-generated plasma, although the data are not definitive.},
doi = {},
url = {https://www.osti.gov/biblio/7279799}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1992},
month = {1}
}

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