No abstract

Normal glow discharges in micrometer scales are being widely studied for a variety of ultra ne processing technologies. DC glow discharge characteristics were investigated at an atmospheric pressure in the range of 0.1-1.65 MPa. The operational discharge characteristics such as voltage-current (V -I) measurement, discharge size, gas temperature, vibrational, and rotational temperatures were obtained for helium (He) and nitrogen (N 2 ) gases. Optical emission spectroscopy studies were carried out to measure rotational and vibrational temperatures using the nitrogen second positive system. Discharge above atmospheric pressure was characterized for the current range of 0.1-1.2 mA and an electrode gap of 5-250 µm. This paper presents evidence for a discharge size as small as 7 µm in N 2 and 16.7 µm in He, while operating at a low current of 0.5 mA and at high pressures of 1.65 and 0.34 MPa, respectively. To the best of our knowledge, this is the rst time an experimentally obtained normalized current density corrected with effective pressure has been estimated to be close to an analytical value (400 µA cm −2 Torr −2 ) for N 2 using a stainless-steel cathode at above atmospheric pressure. The observation of the breakdown of two different gases (N 2 and He), the V -I characteristics, and high current densities indicate that microplasma exhibits a stable glow discharge when a low capacitance external circuit is used. Rotational and vibrational temperatures are obtained in the ranges of 1186-2894 K and 4208-3608 K, respectively, for the pressure range of 0.10-1.65 MPa in N 2 gas for a constant discharge current of 0.5 mA and an electrode gap of 150 µm. It is also notable that the transition from non-equilibrium to equilibrium discharge in both rotational and vibrational temperatures was observed in N 2 at 0.86 MPa, without the transition to thermal plasma (arc discharge).

No abstract

A new non-invasive diagnostic system is developed for Microwave Induced Plasma (MIP) to reconstruct tomographic images of a 2D emission profile. A compact MIP system has wide application in industry as well as research application such as thrusters for space propulsion, high current ion beams, and creation of negative ions for heating of fusion plasma. Emission profile depends on two crucial parameters, namely, the electron temperature and density (over the entire spatial extent) of the plasma system. Emission tomography provides basic understanding of plasmas and it is very useful to monitor internal structure of plasma phenomena without disturbing its actual processes. This paper presents development of a compact, modular, and versatile Optical Emission Tomography (OET) tool for a cylindrical, magnetically confined MIP system. It has eight slit-hole cameras and each consisting of a complementary metal-oxide-semiconductor linear image sensor for light detection. The optical noise is reduced by using aspheric lens and interference band-pass filters in each camera. The entire cylindrical plasma can be scanned with automated sliding ring mechanism arranged in fan-beam data collection geometry. The design of the camera includes a unique possibility to incorporate different filters to get the particular wavelength light from the plasma. This OET system includes selected band-pass filters for particular argon emission 750 nm, 772 nm, and 811 nm lines and hydrogen emission H(α) (656 nm) and H(β) (486 nm) lines. Convolution back projection algorithm is used to obtain the tomographic images of plasma emission line. The paper mainly focuses on (a) design of OET system in detail and (b) study of emission profile for 750 nm argon emission lines to validate the system design.

This paper reports a plasma reactive oxygen species (ROS) method for decontamination of PPE (N95 respirators and gowns) using a surface DBD source to meet the increased need of PPE due to the COVID-19 pandemic. A system is presented consisting of a mobile trailer (35 m3) along with several Dielectric barrier discharge sources installed for generating a plasma ROS level to achieve viral decontamination. The plasma ROS treated respirators were evaluated at the CDC NPPTL, and additional PPE specimens and material functionality testing were performed at Texas A&M. The effects of decontamination on the performance of respirators were tested using a modified version of the NIOSH Standard Test Procedure TEB-APR-STP-0059 to determine particulate filtration efficiency. The treated Prestige Ameritech and BYD brand N95 respirators show filtration efficiencies greater than 95% and maintain their integrity. The overall mechanical and functionality tests for plasma ROS treated PPE show no significant variations.