On phenomena in ionized gases
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- 3. Results and discussion
- Effect of nitric oxide radicals on the proliferation of budding yeast
- 4. References
- Molecules Radicals and Ions produced in a N 2 -H 2 CCP RF
- 2. Experimental device.
- H atom generation and loss kinetics in VHF plasmas
- Densities of active species in N 2 /CH 4 afterglows with application to nitrogen
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1. Introduction Electric power systems include oil-filled equipment such as transformers. When an arc fault occurs inside such equipment, the internal pressure increases, and this may result in blowout and other hazards. To clarify the arc fault phenomena, this paper reports a fundamental study concerning pressure rises due to an arc under insulating oil in a closed vessel.
Arc tests were carried out at the High-Power Testing Laboratory, CRIEPI, under the conditions listed in Table 1. The vessel used in the experiment (Fig. 1) contained the oil and a little air; the pressure rises were measured using pressure transducers located in the air and the oil. The arc was ignited by a fusing copper wire between the copper electrodes under the oil.
The measured waveforms shown in Fig. 2 represent the arc current, pressure rise in air (Pair), and that in oil (Poil), respectively. Every pressure rise peaks to about 200 kPa for the arc duration. The pressure oscillations in air and in oil have reversed phases. To discuss the differences in pressure oscillation, we calculated the approximate pressure for an oil flux. Assuming that flammable gas surrounding the arc compresses the air volume, an acceleration of the oil flow ( α ) can be calculated from Pair. Based on this assumption, the pressure rise in oil (Pcal) is calculated from the oil density ( ρ ), arc depth (D), and measured Pair as follows: Pcal = ρ
D α + Pair (1) Thus, it was observed that Pcal is roughly consistent with the measured value except for several pressure peaks, the differences of pressure oscillation in air and in oil are attributed to oil flow.
0 40 80 120
Arc current [kA
] Pressure rise in air (P air ) [
kPa ] Pressure rise in oil (P oil ) [
kPa ] Time [ms] φ 396
Fig. 1. Configuration of closed vessel. (Unit: mm) Air
20 Oil
745 (Pair) (Poil) 325
φ 310
Electrodes Pressure transducers Fig. 2. Measured waveforms and calculated pressure rise in oil (Pcal). Calculated (Pcal) Reversed phase Arc depth (D) Density (ρ) 906 kg/m 3
1 Table 1. Experimental conditions. Item Condition Power source (Short-circuit generator) Test frequency 50 Hz Voltage / Current RMS 7.2 kV / 2 kA Arc duration 100 ms Closed
vessel Shape
See Fig. 1 Air / Oil volume 1.51 / 120 x10 -3 m 3
Electrodes Material / form Copper / round bar Diameter / Gap length 5 mm / 5 mm
116
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Effect of nitric oxide radicals on the proliferation of budding yeast
Masafumi Ito P 1 P , U Masashi Okachi UP 1 P , Jun-Seok Oh P 1 P , Hiroshi Hashizume P 2
, Masaru Hori 2 P
2
P 1 P
P
P
We have investigated the effect of NO radical treatment on the proliferation of budding yeast and optimized treatment conditions. NO and O 3 densities were measured using UV absorption spectroscopy and the proliferation was evaluated with microscope with cell-counting chamber. From these results, we observed around 20 % increase of the number of yeast cells at a NO density of ~ 7 × 10 16
-3 .
1. Introduction Non-thermal atmospheric pressure plasmas (herein referred to as plasma) are gaining importance to use in biology, medicine, and agriculture. [1] The plasma is a mixed of electrons, ions, photons and neutrals. Recent our studies were focused on the correlation between microorganisms and plasma generated neutral reactive species. [2] Here, we focused on NO which is a well-known molecule in biomedical application. For examples, it is known that the NO enables to improve signal transmission between nerves, maintaining blood pressure, supressing infection, and renewal tissue. In this study, we report the effect of NO radical treatment on the proliferation of budding yeast and optimized treatment conditions.
A commercially available atmospheric pressure plasma radical generator (Tough Plasma, Fuji Machine MFG Co., Ltd.) was used in this study. NO generated with mixture of O 2 and N 2 into buffered Ar (4 slm) through the radical generator. Flow rate of O 2
and N 2 was varied with a fixed total flow rate of 1 slm. The use of a large amount of Ar provides a high electron density on the order of 10 16 cm
−3 . [3] The gas channel at downstream of the radical source is bended where high energy photons are intercepted and the electrically grounded electrodes on the gas channel and the nozzle exit (0.5 mm × 16 mm) terminate charged species. The 3ml-yeast suspension was prepared in a 38-mm diameter petri dish and treated with a fixed distance of 1 cm between the slit exit of the radical source and the surface of the liquid suspension. The cells in counting chamber were counted by using a microscope.
Using UV absorption spectroscopy, we measured NO and O 3 densities, and decided a gas mixture condition, N 2 (30%)–O 2 (70%) in buffered Ar, to obtain high NO density but low O 3 density (lower than the detection limit). From our calculation, it was measure the NO density to be 7.27 × 10 16 cm
-3 . With
this known NO density, we obtained 20% increase of number of budding yeast cell for 15 s treatment. While, longer treatment times up to 45 s, the cell counting results also showed large number of yeast cells compare to the untreated (t = 0, control) but smaller than 15 s. This work was partly supported by MEXT-Supported Program for the Strategic Research Foundation at Private Universities (S1511021), JSPS KAKENHI Grant No. 26286072 and a project for Promoting Research Center in Meijo University.
[1] A. Fridman, Plasma Chemistry, Cambridge (2008). [2] H. Hashizume et al Appl. Phys. Letts. 107 (2015) 093701.
[3] H. Inui et al Appl. Phys. Express 3 (2010) 126101.
17 0 1 2 3 4 5 6 7 Num be r o f b ud di ng ye
as t c
el l (x1 0 7 ce lls /m l) Treatment time (s) 0 15 30 45
Fig. 1 Number of budding yeast cell was increased about 20% with NO treatment for 15 s. Cells were counted after incubation time of 48 h. 117
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Molecules Radicals and Ions produced in a N 2 -H 2 CCP RF
N. Carrasco P 1 P , D. Dubois 1 , A. Chatain 1 , L. Vettier 1 , G. Cernogora 1
P 1 P
CCP RF discharges are well known to be sources of dusty plasmas. These plasmas are used to simulate the formation of organic solid particles in planetary atmospheres, as Titan with a N 2 CH 4 mixture. As a first step for understanding these plasmas, we study here the formation of molecules, radicals and positive ions in a N 2 H 2 CCP RF plasma. mixture. Radicals and positive ions are measured by in situ mass spectrometry. Neutrals are accumulated in a cold trap downstream the plasma. These molecules are measured, after warming the trap by mass spectrometry and IR absorption spectroscopy. . When mass spectrometry gives relative values of species abundances, IR absorption gives absolute values of the most abundant molecules. A focus is done on NH 3 , this
molecule being produced as well in the discharge as by catalytic effect on the metallic wall of the discharge.
A Capacitively Coupled Plasma in N 2 -CH
4
mixture is used for the formation of dust to simulate the formation of solid aerosols in Titan’s atmosphere. Details of this experimental device are described in details in [1]. The dissociation of CH 4
produces H 2 molecules. In order to understand the complex chemistry occurring in the N 2 CH 4 mixture, study of the N 2 H 2 mixture is developed as a first step.
Experimental device
The CCP discharge is confined in a metallic cylindrical box of 13.6 cm in diameter. Two slots, diametrically opposed are managed in the cylindrical box. This box is placed into a 30 cm in diameter and 40cm height stainless steel reactor fitted with two KBr windows diametrically opposed. Gas mixture is injected continuously in the plasma and pumped with a rotary pump. The amount of H 2 in N 2 is tuned from 1 to 5%. Pressure in the plasma discharge is maintained at 1 mbar. Between the discharge and the pump, a trap cooled by liquid nitrogen condenses molecules produced in the discharge.
The neutral molecules, radicals and positive ions are measured using a mass spectrometer EQP Hiden placed in front of one of the slot.
After few hours of plasma run, the gas injection is turned off, valves upstream and downstream the cold trap are closed and the trap is slowly warmed up to the room temperature. Then the condensed gases are reinjected in the reactor. The molecules densities are measured using a Nicolet 6700 Fischer FTIR spectrometer through the 40 cm of in diameter of the reactor [2]. Focus is done on the NH 3 molecule measured in the 967 cm -1 band. In our experimental conditions, the NH 3
12 cm
-3 .
4- Perspectives These results obtained are now to be compared with the modelling of the plasma in our experimental conditions. The major point is the relative contribution of volume reactions versus catalytic ones for the formation of NH 3 .
5. References [1] Alcouffe, G. , M. Cavarroc, G. Cernogora, F. Ouni, A. Jolly, L. Boufendi and C. Szopa (2010),. Plasma Sources Sci. Technol. 19(1): 015008. [2] Dubois D., Carrasco N., Petrucciani M., Tigrine S., Vettier L Neutral Chemistry in Titan's Ionospheric Simulated Conditions, Dubois D., et al., DPS-EPSC 2016, Oct 2016, Pasadena, USA
Topic number 9 118
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
H atom generation and loss kinetics in VHF plasmas
S. Nunomura 1 P , H. Katayama 2 P22
, I. Yoshida 3
P
National institute of advanced industrial science and technology (AIST), Tsukuba, Ibarak, 305-8568, Japan 2 Panasonic corporation, Kaizuka, Osaka 597-0094, Japan 3 Photovoltaic Power Generation Technology Research Association Minato-ku, Tokyo 105-0011, Japan P
We study hydrogen (H) atom generation and loss kinetics in capacitively coupled low pressure H 2
plasma. The H atom density has been measured by using vacuum ultra violet absorption spectroscopy (VUVAS), under two different electrode setups: conventional diode (direct) and triode with an intermediate mesh (remote). In the triode setup, the H atom density is strongly reduced across the mesh electrode; it varies from 10 12 cm
-3 to 10
10 cm
-3 across the mesh. The fluid model simulations for VHF discharges have been performed to study the details of the H atom generation, diffusion and recombination kinetics.
A H atom is widely known to be reactive species, which reacts easily with other gas-phase species and various material surfaces. So, its reaction kinetics often plays key roles in plasma processing. So far, the H atom kinetics has been studied in “direct” plasma configuration. However, it is not studied for the “remote” plasma configuration that has advantages of less-ion bombardment and reduced surface charging. Here, we study the H atom kinetics in capacitively-coupled very high frequency (VHF) discharges not only in direct (diode) configuration but also in remote (triode) configuration. The H atom density is experimentally determined from VUVAS [1]. The fluid model simulations of VHF discharges are performed to study the H atom kinetics. Figure 1 show the meausrement results of the H atom density, n H , in VHF H 2 discharges [2]. It is found that n H is of the order of 10 12 cm
-3 in the discharge region, whereas it is of the order of 10 10
cm -3 in the processing region under the remote configuration. For our mesh geometry, i.e., a mesh with 0.2 mm in thickness and 36% in aperture ratio, n H varies two orders of magnitude across the mesh. Figure 2 shows the simulation results. As shown Fig. 2(a), n H is broadly peaked at the middle of the discharge region. The peak value is recognized to be ~1.0 x 10 12 cm
-3 , which is in good agreement with that measured by VUVAS in this study. The H atoms are generated mainly in the discharge region, via two processes: the electron impact dissociation (e + H 2
=> e + 2H), as shown in Fig. 2(b), and the ion-molecule reaction (H 2 +
2 => H
3 + + H), as shown in Fig. 2(c). We also notice that in the processing region, the generation rate of the H atoms, g H , is negligibly small. This is because the electron temperature is rather low compared with the threshold energy of the electron impact dissociation. As for the loss of H atoms, the electron attachment (e + H => H
- ), shown in Fig. 2(d), is negligibly small, compared with the generation. The loss of H atoms is thus dominated by the surface recombination on the electrode. In the presentation, more details of experimental and simulation results are presented. [1] S. Takashima, M. Hori, T. Goto and K. Yoneda, J.
[2] S. Nunomura, H. Katayama and I. Yoshida, Plasma Sources Sci. Technol. 26 (2017) 055018.
Topic number: 9 Fig. 1. H atom density, n H , & Balmer emission intensity, I
, vs. the discharge power, P VHF
at H 2 gas pressure of p = 0.3 Torr. Fig. 2.
Contour plots of hydrogen (H) atom related parameters [2]. (a) H atom density, n H , (b) H atom generation rate, g
, associated with the electron impact dissociation (e + H 2 => e + 2H) (c) H atom generation rate, associated with the ion-molecule reaction (H 2 +
2 => H
3 + + H) and (d) H atom loss rate due to the electron attachment, e + H => H - . The simulation space includes two unit cells of the mesh structure in the horizontal axis of 0 – 1.66 mm. 119
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Densities of active species in N 2 /CH 4 afterglows with application to nitrogen and carbon doping of anatase nanocrystals and ALD TiO 2
A. Ricard P 1 P , U J.P. Sarrette UP 1 P , Y. Wang P 2 P , Y.K. Kim 2 2
P 1 PLL
LAPLACE, Université de Toulouse, CNRS, INPT, UPS, 118 ro ute de Narbonne, 1062 Toulouse, France P
P
N 2 / 0-3 0 / 00 CH 4 microwave (HF) flowing afterglow emissions have been characterized by optical emission spectroscopy at pressure between 4 and 20 Torr in a tube of 18 mm internal diameter (i.d.) at constant flow rate (Q tot
= 0.5 slpm) and injected HF power (P HF = 100 W). The N 2 1 st pos at 580.4 nm and CN violet at 384.7 nm band system intensities were recorded along the tube in the late afterglow region. After calibration of the N atom density by NO titration, the absolute concentrations of N and C atoms were determined. The C-atom density shows a maximum value of 4.7 10 13 cm
-3 at 13 Torr for the N 2 / 0.04 0 / 0 CH 4 mixture. Anatase nanocrystals and ALD (Atomic Layer Deposition) TiO 2 samples were exposed to optimum afterglow conditions at temperatures ranging from 300 to 600 K. Surface-selective chemical modifications of TiO 2 samples are evaluated by XPS. 1. Introduction In various applications such as photocatalysis, photovoltaics and sensors, the performance of TiO 2 is largely determined by the detailed chemical structure of the surface. For example, the introduction of nitrogen in TiO 2 can reduce the bandgap below 3.0 eV for a visible activity in photocatalysis. Nevertheless, the N-doped TiO 2 performance largely depends on the control of the nitrogen bonding structure and distribution between the surface and the bulk. In addition, carbon may also displace the lattice Ti to give C-doped TiO 2 which may show enhanced visible light absorption and photoactivity. However, the ultimate performance is strongly related with detailed bonding nature of carbon on the surface as well as within the TiO
2 matrix. From this point of view, flowing afterglows at reduced pressure can be very useful because of their high concentrations in atoms and of their simplified chemistry, easily monitored through the operating parameters (pressure, gas flow rate, injected power). The aim of the present study is to maximize the production of N and C-atoms in N 2 /CH 4 afterglows and to expose anatase nanocrystals and ALD TiO 2
samples in optimal conditions. X-ray photoemission spectroscopy (XPS) is used to quantitatively evaluate the modifications induced on the extreme surface composition.
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