期刊
PLASMA SOURCES SCIENCE & TECHNOLOGY
卷 29, 期 3, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/1361-6595/ab6f9c
关键词
capillary discharge; atomic nitrogen TALIF; nanosecond pulse discharge; high specific deposited energy; krypton calibration TALIF; N-2 dissociation
资金
- French National Research Agency
- ANR (ASPEN Project)
- LabEx Plas@Par
- French-Russian international laboratory LIA KaPPA 'Kinetics and Physics of Pulsed Plasmas and their Afterglow' [17-52-16001]
- CNRS
The atomic nitrogen (N) density in a nanosecond pulse capillary discharge is measured using two-photon laser induced fluorescence. The capillary discharge is favored for its unique combination of both large reduced fields (E/N) and high specific deposited energies. Under such conditions, we find that a pure nitrogen (N-2) capillary discharge at a pressure of 27 mbar and initial temperature of about 300 K, produces a peak N-atom density of 1.29 x 10(17) cm(-3), corresponding to an extremely high dissociation degree of about 10%. The time evolution of the N-atom density is tracked from a few hundred ns after discharge initiation, up to several ms when the concentration of N-atoms falls below the detection limit. The temporal evolution curve exhibits a trapezoidal-like shape, characterized by an initial rise in the N-atom density up to a few mu s, followed by a relatively flat and constant profile until about 1 ms, and finally terminating with a drop to near detection limits at about 10 ms. The high electron densities (10(15) cm(-3)) and efficient production of electronically excited states associated with this type of discharge is found to have a profound effect on the consequent kinetics. A process of stepwise dissociation through electron impact of the excited states is examined and proposed as a possible explanation for the unusually high energy efficiency of N-atom production. The present study shows that the capillary discharge is an extremely effective source of N-atoms, and forms the impetus for continued study of discharges with both high levels of specific deposited energies (>= 1 eV/molecule) and reduced electric fields (E/N >= 150 Td).
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