Diagram of hairpin resonator. width and length. Epoxy holds the loop wire and the hairpin together without allowing a direct electrical connection. The oscillating currents from the sweep generator create oscillating electromagnetic fields in the loop wire. The oscillating electromagnetic fields couple to the hairpin when the frequency from the sweep generator is near the hairpin’s quarter-wavelength resonance.
Schematic of experiment.
(a) Three resonance curves at . (b) Three resonance curves at . At higher currents, the peak frequency shifted to larger values and the value decreased. The shift to higher peak frequencies indicated an increase in electron number density, as seen in Eq. (3). The decrease in for a given pressure also indicated an increase in electron number density.
Real component of the dielectric constant vs normalized plasma frequency for a range of normalized collision frequencies .
Hairpin resonance curves at selected points in time in the afterglow are shown at a pressure of . The resonant frequency shifted from in the afterglow, which indicated a decrease in the electron number density.
Electron number density versus time in the nitrogen afterglow. At each pressure, the current before switching off the discharge was . Since the diffusion of electrons was no longer ambipolar below an electron number density of roughly , we do not include values below this cutoff.
Experimental and numerical steady-state results.
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