Radial Measurements of Gas Discharge Parameters of Atmospheric Pressure Microplasma

Abstract

In this work Abel inversion technique was used for radial measurements of the microplasma in Ar-2%H2 flow at open atmosphere. The gas discharge parameters were investigated using spatially resolved high resolution optical emission spectroscopy (OES) to allow acquisition of OH (A 2Σ+, ν = 0 →X 2Π, ν′ = 0) rotational bands at 306.357 nm, Ar I 603.213 nm line and N2(C3∏u, ν = 0 →B3∏g, ν′ = 0) second positive system with the band head at 337.13 nm. The nonthermal plasma was generated between microhollow anode (~500 μm inner diameter) and a cathode copper foil, fed by direct current source for a current ranging from 20 mA to 100 mA (Townsend discharge from 20 mA to 30 mA, normal glow discharge from 30 mA to 80 mA at 210 V and abnormal discharge beyond 90 mA). The 1.5 mm length cylindrical-shape plasma has an outspread bright disk (negative glow region) near the cathode surface. Besides the gas temperature, the excitation temperature was measured radially for a current ranging from 20 mA to 100 mA, either from Boltzmann-plot of Ar I 4p – 4s and 5p – 4s transitions of excited argon or from Cu I two lines method of excited cuprum atoms released from the cathode surface. The measurements showed a nearly bell-shaped distribution of these temperatures, peaked at 120 μm from the center with the minimum at the plasma border. The average excitation temperature was about ~8000 K (maximum ~10,000 K) and the average rotational temperature was about 650 K (maximum ~800 K) from 20 K to 100 K. For the N2 second positive system with Δν = -2 it was estimated the vibrational temperature for the bright disk (1500 K to 5000 K). Hβ line Stark broadening was employed to define the electron number density of the negative glow (1015 cm -3).

Optical Measurements of an Atmospheric Pressure Microplasma Jet Aiming Surface Treatment

“…Figure 6 presents the experimental rotational spectrum of OH (first order, ultra-violet, A 2 Σ + , ν = 0 →X 2 Π, ν ' = 0) at 306.4 nm obtained for Ar APMJ. The T rot may be taken from the Boltzmann plot (BP) [13][14][15][16][17][18][19]. The spectra of OH bands were obtained with a resolution of 0.05 nm.…”

“…Figure 3 shows a set of neutral and ionic particles, especially highly reactive ones as OH, O and N 2 + . We can estimate the electronic temperature through Line Intensity Method, where the Saha equation is used to obtain the ratio between emitted spectral lines [13][14][15][16][17]. We choose the following lines ( Fig.3): a) Ar + 4p-4s and Ar 4p-4s; b) N 2 + (391nm) and N 2 rotational lines.…”

Low Temperature Microplasma Jet at Atmospheric Pressure for Inducing Surface Modification on Polyethylene Substrates

“…Atmospheric Pressure Microplasma Jet (APMJ) can be generated through a number of configurations, generally using noble gases [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The APMJ are suitable for industrial and research applications, such as surface modification, biological material sterilization, biomedical applications (dermatological, dental, etc.…”

Study of Microhollow Cathode Glow Discharge to Improve the Wettability on Surface of Polypropylene Film

“…Because of the required small size of the cathode opening for high-pressure operation, these discharges are known as Microhollow Cathode (MHC) discharges [2][3][4][5][6][7][8][9][10]. High-pressure direct current (dc) MHC glow discharges can be easily generated inside the cavity between perforated small area of Cu foil electrodes (9cm 2 and 50µm thickness), separated by thin layer of mica (dielectric material, about 100µm thickness).…”