Diagnostics of pre-breakdown light emission in a helium coplanar barrier discharge: the presence of neutral bremsstrahlung

Abstract

Weak light emission (∼10 −3 of active discharge signal; average count rate ∼ 1 photon s −1 nm −1 ) associated with surface charge relaxation during the dark phase of a helium diffuse coplanar barrier discharge was studied by optical emission spectroscopy, using a technique of phase-resolved single photon counting. The optical emission spectra of the dark phase contained luminescent bands of the dielectrics used (Al 2 O 3 , AlN) and spectral lines from the gas constituents (OH * , N 2 *, N 2 * + , He * , He 2 *, O * ). During the charge relaxation event, a broad continuum appeared in the optical emission spectra, consisting of bremsstrahlung radiation and amplified luminescence of the dielectric barrier.The analysis presented suggests that the bremsstrahlung radiation originated from slow electrons colliding with neutral helium atoms. The fitting procedure we developed reproduced well the observed shape of the continuum. Moreover, it provided a method for the determination of electric field strength in the discharge during this particular phase. The electric field reached 1 kV cm −1 during the charge relaxation event.

Time-resolved optical emission spectroscopy in CO2 nanosecond pulsed discharges

“…Electronneutral Bremsstrahlung continuum has been reported many times in atmospheric pressure discharges [30][31][32][33][34][35][36]. In some cases, it has even been used for electron density and temperature measurements [31,32,35,36]. Looking at the Bremsstrahlung spectra shown in [30,36] calculated at various electron temperatures, we find that they are not conflicting with our spectra if we assume an electron temperature in the range 1-2 eV.…”

Advanced electrical current measurements of microdischarges: evidence of sub-critical pulses and ion currents in barrier discharge in air

“…For the case of corona discharges, the similar contributions of Laan et al [70] or Petit et al [71] can be mentioned. We believe that the enhanced methodology of current measurements presented in this paper can contribute significantly to the recently-reported special cases of the discharging phenomena in extremely weak prebreakdown phases, whether at the dielectric surface [14,31,32] or in the volume [27,29,30].…”

“…Typically, in order to study the microdischarge current development the required resolution of the current probe has to go to sub-ns times and μA. Moreover, a low current discharging phenomenon was observed recently during the prebreakdown phases of surface and volume barrier discharges [14,27,[29][30][31][32], which is hard to study without the necessary dynamical range in the current probing system.…”

“…Recently, optical emission, absorption and laser spectroscopy techniques have dominated as tools for detailed plasma investigation. Precise current measurements and their proper analysis are somewhat left behind, although the investigation of ultra-fast, low-current phenomena (as reported in [14,27,[29][30][31][32]) could significantly benefit from them. In this paper, we present a simple self-made current probe and compare its performance with some commercial current probes in common usage.…”

Comparing efficiencies of polypropylene treatment by atmospheric pressure plasma jets

“…All the measured spectra contained relatively weak $${\text{Cr}}^{3+}$$ lines (692.9 and 694.3 nm) originating from the impurities present in the alumina ceramic body of the tube used to limit the acceptance cone of the fiber. [ 47 ]…”