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A simple profile-fitting method is applied to determine the concentrations of metastable and resonant species in a cold atmospheric pressure argon plasma jet. This method is based on the analysis of the effect of self-absorption broadening on the profiles of spectral lines emitted from plasma. The Argon lines which correspond to transitions to metastable and resonant lower states were measured with high resolution optical emission spectroscopy. Fitting the measured line contours yields line-integrated densities (Nl × L) of metastable Ar(1s5) and Ar(1s3) of 1.2 × 1015 m-2 and 5.0 × 1014 m-2, respectively. For resonant species, it is difficult to perform a good density-estimation by fitting measured line contours because of the broad intrinsic resonant line shape and the low resonant densities in the plasma. Top-limits of 4.8 × 1015 m-2 and 7.2 × 1014 m-2 are estimated for resonant states Ar(1s2) and Ar(1s4), respectively. By comparing the fittings of metastable and resonant lines, it is found that the applicability of the profile-fitting routine is sensitive to the line-center optical thickness of emission lines (mainly determined by the lower states densities) and the sharpness of intrinsic line profiles of corresponding transitions. [ABSTRACT FROM AUTHOR]

The fundamental of the generation and propagation of the atmospheric pressure nonequilibrium plasma jets has recently attracted significant interests. In this paper, investigations on the effects of the parameters of the pulsed dc voltages on the optical emission intensity of the plasma jet and the bullet propagation behavior are carried out based on the temporal-spatial resolved optical emission spectroscopy measurements and the high-speed photography. It is found that, with the increase in the applied voltage, the bullet propagates out from the nozzle earlier and accelerates to higher peak-velocities. The increase in the pulse frequency exerts no significant influences on the optical emission of the plasma jet and the bullet propagation velocity. But it can induce the bullet propagates out from the nozzle earlier. Besides, it is interesting to notice that, with the increase in the pulse width in the beginning, the bullet propagates out from the nozzle with longer delay time. However, when the pulse width is increased to be more than 100 μs, the delay time of the bullet propagating out from the nozzle becomes much shorter. On the other hand, with the increase in the pulse width, the optical emission intensity of the plasma jet drops and the maximum bullet velocity decreases too. Detailed analysis shows that it may be due to the accumulation of the charges and radicals, which can shorten the prebreakdown of the discharge inside the syringe and result in the bullet propagating out earlier from the nozzle. [ABSTRACT FROM AUTHOR]

Cold plasmas have recently received great attention. In this paper, optical and electrical diagnostics are carried out on a reliable and user-friendly plasma plume. A simple electrical model is used to simulate the electrical characteristics of the device. The plasma is represented by a resistor connected in parallel with a capacitor, an inductor, and another resistor, which are connected in series. The simulated current-voltage waveforms have very good agreement with experimental measurements. Besides, the emission spectra of the plasma are also studied. It shows that, when Ar is used as working gas, there is strong OH (hydroxyl radical) emission and the emission intensities of the N2 emission bands are more than three times higher than that of He. On the contrary, when He is used as working gas, the emission intensities of N2+ band are much stronger. Detail analyses on these observations are presented. [ABSTRACT FROM AUTHOR]

The propagation behavior of cold atmospheric pressure plasma jets has recently attracted lots of attention. In this paper, a cold He plasma jet generated by a single plasma electrode jet device is studied. The spatial-temporal resolved optical emission spectroscopy measurements are presented. It is found that the emission intensity of the He 706.5 nm line of the plasma behaves similarly both inside the syringe and in the surrounding air (plasma plume). It decreases monotonously, which is different from the emission lines, such as N2 337.1 nm line, N2+ 391.4 nm line, and O 777.3 nm line. For the discharge inside the syringe, the emission intensity of the He 706.5 nm line decays more rapidly than that of the other three spectral lines mentioned above. The N2 337.1 nm line behaves a similar time evolution with the discharge current. For the N2+ 391.4 nm line and the atomic O 777.3 nm line, both of them decay slower than that of the He 706.5 nm and the N2 337.1 nm. When the plasma plume propagates further away from the nozzle, the temporal behaviors of the emission intensities of the four lines tend to be similar gradually. Besides, it is found that, when the size of the plasma bullet appears biggest, the propagation velocity of the bullet achieves its highest value while the emission intensity of the N2+ 391.4 nm line reaches its maximum. Detailed analysis shows that the Penning effect between the metastable state Hem and the air molecules may play a significant role in the propagation of the plasma bullet in the open air. [ABSTRACT FROM AUTHOR]

The “plasma bullet” behavior of atmospheric pressure plasma plumes has recently attracted significant interest. In this paper, a specially designed plasma jet device is used to study this phenomenon. It is found that a helium primary plasma can propagate through the wall of a dielectric tube and keep propagating inside the dielectric tube (secondary plasma). High-speed photographs show that the primary plasma disappears before the secondary plasma starts to propagate. Both plumes propagate at a hypersonic speed. Detailed studies on the dynamics of the plasma plumes show that the local electric field induced by the charges on the surface of the dielectric tube plays an important role in the ignition of the secondary plasma. This indicates that the propagation of the plasma plumes may be attributed to the local electric field induced by the charges in the bulletlike plasma volume. [ABSTRACT FROM AUTHOR]

SQUID magnetometric and dc-susceptibility measurements reveal that the Tc of HgBa2CuO(4 + delta) decreases with an annealing temperature (Ta) of more than 300 degrees centigrade in vacuum and becomes zero when Ta is 400 degrees centigrade. At pressures of approximately 500 atm, Tc decreases with a reduction in Ta. Doping of anion causes a variation in Tc. The delta value does not depend on O2 partial pressure in this compound.

Focuses on a study which investigated the temperature and magnetic field dependence of critical current density for yttrium barium copper oxide thin films. Discussion on the importance of the critical current density in electronic applications of high-temperature superconductor thin films; Details of the experimental procedure; Findings from x-ray diffraction analysis.