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Title: Moderate pressure plasma source of nonthermal electrons

Plasma sources of electrons offer control of gas and surface chemistry without the need for complex vacuum systems. The plasma electron source presented here is based on a cold cathode glow discharge (GD) operating in a dc steady state mode in a moderate pressure range of 2–10 torr. Ion-induced secondary electron emission is the source of electrons accelerated to high energies in the cathode sheath potential. The source geometry is a key to the availability and the extraction of the nonthermal portion of the electron population. The source consists of a flat and a cylindrical electrode, 1 mm apart. Our estimates show that the length of the cathode sheath in the plasma source is commensurate (~0.5–1 mm) with the inter-electrode distance so the GD operates in an obstructed regime without a positive column. Estimations of the electron energy relaxation confirm the non-local nature of this GD, hence the nonthermal portion of the electron population is available for extraction outside of the source. The use of a cylindrical anode presents a simple and promising method of extracting the high energy portion of the electron population. Langmuir probe measurements and optical emission spectroscopy confirm the presence of electrons with energies ~15 eVmore » outside of the source. These electrons become available for surface modification and radical production outside of the source. In conclusion, the extraction of the electrons of specific energies by varying the anode geometry opens exciting opportunities for future exploration.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1]
  1. Princeton Univ., Princeton, NJ (United States)
Publication Date:
Grant/Contract Number:
AC02-09CH11466; 201506340040
Type:
Accepted Manuscript
Journal Name:
Journal of Physics. D, Applied Physics
Additional Journal Information:
Journal Volume: 51; Journal Issue: 23; Journal ID: ISSN 0022-3727
Publisher:
IOP Publishing
Research Org:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; glow discharge; electron source; non­equilibrium plasma; non­local plasma; nonthermal electrons
OSTI Identifier:
1459552

Gershman, S., and Raitses, Y.. Moderate pressure plasma source of nonthermal electrons. United States: N. p., Web. doi:10.1088/1361-6463/aabfb1.
Gershman, S., & Raitses, Y.. Moderate pressure plasma source of nonthermal electrons. United States. doi:10.1088/1361-6463/aabfb1.
Gershman, S., and Raitses, Y.. 2018. "Moderate pressure plasma source of nonthermal electrons". United States. doi:10.1088/1361-6463/aabfb1.
@article{osti_1459552,
title = {Moderate pressure plasma source of nonthermal electrons},
author = {Gershman, S. and Raitses, Y.},
abstractNote = {Plasma sources of electrons offer control of gas and surface chemistry without the need for complex vacuum systems. The plasma electron source presented here is based on a cold cathode glow discharge (GD) operating in a dc steady state mode in a moderate pressure range of 2–10 torr. Ion-induced secondary electron emission is the source of electrons accelerated to high energies in the cathode sheath potential. The source geometry is a key to the availability and the extraction of the nonthermal portion of the electron population. The source consists of a flat and a cylindrical electrode, 1 mm apart. Our estimates show that the length of the cathode sheath in the plasma source is commensurate (~0.5–1 mm) with the inter-electrode distance so the GD operates in an obstructed regime without a positive column. Estimations of the electron energy relaxation confirm the non-local nature of this GD, hence the nonthermal portion of the electron population is available for extraction outside of the source. The use of a cylindrical anode presents a simple and promising method of extracting the high energy portion of the electron population. Langmuir probe measurements and optical emission spectroscopy confirm the presence of electrons with energies ~15 eV outside of the source. These electrons become available for surface modification and radical production outside of the source. In conclusion, the extraction of the electrons of specific energies by varying the anode geometry opens exciting opportunities for future exploration.},
doi = {10.1088/1361-6463/aabfb1},
journal = {Journal of Physics. D, Applied Physics},
number = 23,
volume = 51,
place = {United States},
year = {2018},
month = {4}
}