Propagation dynamics of a room-temperature pulsed argon plasma plume through a simple dispersion-grating diagnostic method

In this paper, a novel grating-ICCD camera dispersion diagnostic method was designed to investigate the propagation behaviors of an open-air pulsed argon plasma plume. Based on the dispersion feature of gratings, the irradiative plasma plume was dispersed into several emission-volumes corresponding to different wavelengths. And a series of high-speed dispersed emission-image sequences were captured by the ICCD camera. From these sub-microsecond emission-images at different wavelengths, the temporal and spatial propagation behaviors of excited species in the plasma plume were observed clearly

Positive- and negative-pulsed argon plasma plumes in the open air

Cold atmospheric pressure plasma plumes have obtained great interests for their attractive features and application potentials. In this work, cold argon plasma plumes were generated in the open air by a single medical-needle excited by a high-power pulsed excitation source. Characteristic comparision was carried out in the plasmas under different polarties of applied voltages. The results showed that the positive pulsed plasma plume performed a larger discharge current and stronger optical emission than the negative case. Gas temperature of the plasmas were obtained by the Boltzmann plot method and fitting the syntheric-to-experimental spectrum of the OH (A-X) transition emission bands. It is found that both the positive and negative pulsed plasma plumes are under a relative low gas temperature about 400 K. Through the high-speed imaging, an interesting propagation process was observed for the positive pulsed plasma plume, during which the plasma first propagates in the form of plasma ‘bullets’, and then transits into typical stream propagation as soon as the ‘bullets’ disappears in the open air, which is much different with the negative case

Electron Density and Temperature Measurement of an Atmospheric Pressure Plasma by Millimeter Wave Interferometer

In this paper, a 105 GHz millimeter wave interferometer system is used to measure the electron density and temperature of an atmospheric pressure helium plasma driven by submicrosecond pulses. The peak electron density and electron-neutral collision frequency reach 8 X 1012 cm-3 and 2.1 X 1012 s-1, respectively. According to the electron-helium collision cross section and the measured electron-neutral collision frequency, the electron temperature of the plasma is estimated to reach a peak value of about 8.7 eV

Dynamics of an Atmospheric Pressure Plasma Plume Generated by Submicrosecond Voltage Pulses

Nonequilibrium plasmas driven by submicrosecond high voltage pulses have been proven to produce high-energy electrons, which in turn lead to enhanced ionization and excitations. Here, we describe a device capable of launching a cold plasma plume in the surrounding air. This device, the plasma pencil, is driven by few hundred nanosecond wide pulses at repetition rates of a few kilohertz. Correlation between current-voltage characteristics and fast photography shows that the plasma plume is in fact a small bulletlike volume of plasma traveling at unusually high velocities. A model based on photoionization is used to explain the propagation kinetics of the plasma bullet under low electric field conditions

Optimization of Ultraviolet Emission and Chemical Species Generation from a Pulsed Dielectric Barrier Discharge at Atmospheric Pressure

One of the attractive features of nonthermal atmospheric pressure plasmas is the ability to achieve enhanced gas phase chemistry without the need for elevated gas temperatures. This attractive characteristic recently led to their extensive use in applications that require low temperatures, such as material processing and biomedical applications. The agents responsible for the efficient plasma reactivity are the ultraviolet (UV) photons and the chemically reactive species. In this paper, in order to optimize the UV radiation and reactive species generation efficiency, the plasma was generated by a dielectric barrier discharge driven by unipolar submicrosecond square pulses. To keep the discharge diffuse and to maintain low operating temperatures, helium (He) was used as a carrier gas. Mixed with helium, varying amounts of nitrogen (N2) with the presence of trace amounts of air were used. The gas temperature was determined to be about 350 K at a 1-kHz pulse frequency for all cases and only slightly increased with frequency. The UV emission power density, PUV, reached its highest level when 5% to 10% of N2 is mixed to a balance of He. A maximum PUV of about 0.8 mW/cm2 at 10-kHz pulse frequency for a He (90%) + N2 (10%) mixture was measured. This was more than four times higher than that when He or N2 alone was used. Furthermore, the emission spectra showed that most of the UV was emitted by excited NO radicals, where the oxygen atoms came from residual trace amounts of air. In addition to NO, NO2, and excited N2, N2+, OH, and He were also present in the plasma

Room-Temperature Atmospheric Pressure Plasma For Biomedical Applications

As low-temperature non-equilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little ozone is generated and the gas temperature, as measured by emission spectroscopy, remains at room temperature even after hours of operations. The plasma plume can be touched by bare hands and can be directed manually by a user to come in contact with delicate objects and materials including skin and dental gum without causing any heating or painful sensation

Special Issue on Plenary and Invited Papers From ICOPS 2010

HE 37th IEEE International Conference on Plasma Science (ICOPS) was held in Norfolk, VA, from June 20 to June 24, 2010. The technical program combined seven technical-related areas of plasma science and a range of diverse topics. A total of 562 abstracts from 37 countries were accepted, and the technical program included four plenary talks. There were 217 oral and 345 poster presentations. The plenary talks were given by Prof. L. Boufendi on Dusty Plasmas, Prof. E. Kunhardt on Non-Equilibrium Plasma Sources, Dr. K. S. Budil on High Energy Density Physics, and Dr. M. Thumm on the use of gyrotrons for ITER and fusion reactors. For the first time, ICOPS had a session on terahertz radiation and applications organized by Dr. B. Levush of NRL and two special sessions on the emerging field of Plasma Medicine, organized by Prof. M. Laroussi and Prof. M. Kong

Measurement of OH radicals at state X ²Π in an atmospheric-pressure micro-flow dc plasma with liquid electrodes in He, Ar and N₂ by means of laser-induced fluorescence spectroscopy

The density of OH radicals in ground state is measured by laser-induced fluorescence (LIF) spectroscopy in the core of a micro-flow discharge in He, Ar and N-2 with a water electrode. The lines P-2(6), P-1(4) and P-2(3) of the X (2)Pi (v '' = 0) to the A(2)Sigma(+) (v' = 1) transition are used for OH radical excitation. The density of the main quencher of OH radical in the core of the discharge is estimated based on the time decay of the LIF signal. It is revealed that the plasma core consists of a high amount of 8-10% of water vapour. The calculation of the absolute density of OH radical is carried out based on the model of LIF excitation including vibrational and translation energy transfer, and the results in different gases are presented for the discharge

Grand Challenges in Low Temperature Plasmas

Low temperature plasmas (LTPs) enable to create a highly reactive environment at near ambient temperatures due to the energetic electrons with typical kinetic energies in the range of 1 to 10 eV (1 eV = 11600K), which are being used in applications ranging from plasma etching of electronic chips and additive manufacturing to plasma-assisted combustion. LTPs are at the core of many advanced technologies. Without LTPs, many of the conveniences of modern society would simply not exist. New applications of LTPs are continuously being proposed. Researchers are facing many grand challenges before these new applications can be translated to practice. In this paper, we will discuss the challenges being faced in the field of LTPs, in particular for atmospheric pressure plasmas, with a focus on health, energy and sustainability