On phenomena in ionized gases
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- Mineralization of 2,4-dichlorophenoxyacetic acid by plasma-ozonation
- Ultrafast Laser Diagnostics to Interrogate High Pressure, Highly Collisional Plasma Environments
- Metastables Electrons Fronts
- Effects of plasma-facing materials on the negative ion (H-/D-) current extracted from an ECR plasma source
- 5. References
- Application of plasma-bullet propagation to hydrophilic treatments of an interconnected porous scaffold
- 3. Results and discussion
- Acknowledgements
- + 60 ns + 80 ns + 100 ns 5 mm + 0 ns + 20 ns + 40 ns
- Bubble formation in the discharge between planar and needle electrodes via laser ablation-induced cavitation bubble
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3. References [1] S. Takamura, N. Ohno, D. Nishijima, and S. Kajita: Plasma Fusion Res. 1 (2006) 051. [2] S. Kajita, T. Yoshida, D. Kitaoka, et al.: J. Appl. Phys. 113 (2013) 134301. [3] S. Kajita, T. Yoshida, N. Ohno, et al.: Sci. Rep.
Topic number 60
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Mineralization of 2,4-dichlorophenoxyacetic acid by plasma-ozonation
M. Magureanu 1 , C. Bradu 2 , V.I. Parvulescu 3
1 Department of Plasma Physics and Nuclear Fusion, National Institute for Lasers, Plasma and Radiation Physics, Magurele-Bucharest, Romania 2 Department of Systems Ecology and Sustainability, Faculty of Biology, University of Bucharest, Romania 3 Department of Organic Chemistry, Biochemistry and Catalysis, Faculty of Chemistry, University of Bucharest, Bucharest, Romania
A pulsed corona discharge in contact with liquid combined with ozonation was investigated for the degradation of 2,4 dichlorophenoxyacetic acid (2,4-D), a widely used herbicide. The target compound was completely eliminated after 30 min treatment. The reaction rate constant for 2,4-D removal by plasma-ozonation was 194.5 x 10 -3 min -1 , more than twice the value obtained by ozonation alone. Within 60 min over 90% mineralization was obtained, which represents a significant improvement as compared to O 3 alone. The chlorine balance demonstrates the absence of chlorinated by-products after 30 min treatment. An attempt to improve energy efficiency revealed the beneficial effect of shortening discharge pulse duration.
Pesticides are commonly detected in various water bodies and thus threaten aquatic species [1]. Various advanced oxidation processes are studied for elimination of these chemicals, and among them ozonation is considered one of the most promising, but the main drawback is poor mineralization [2,3]. In this work, non-thermal plasma generated in a pulsed corona discharge above liquid is combined with ozonation, with O 3 produced in the discharge. This combination proved efficient for the removal of other chemical compounds from water [4]. The target compound chosen for this study is 2,4-D, a widely used herbicide, often detected in surface and ground water and sometimes in drinking water [5]. The experiments were carried out using a pulsed corona discharge above liquid (multiwire-plate geometry) in series with a cylindrical ozonation reactor [4]. The 2,4-D solution (25 mg/L, 330 mL) was continuously circulated between the two reactors and the effluent gas from the plasma was bubbled into the solution contained in the cylinder. The removal of 2,4-D is completed after 30 min treatment in the plasma-O 3 system (Fig. 1a) and the rate constant (194.5x10 -3 min -1 ) is more than twice the value obtained for O 3 treatment alone (88.2x10 -3
min -1 ). The mineralization degree is assessed from the elimination of TOC (total organic carbon). TOC removal reaches over 90% after 60 min plasma+O 3
3
alone (56%) (Fig. 1b). The results prove the major role played by other plasma-generated oxidants, besides O 3 , in the degradation of 2,4-D. Reducing discharge power by shortening the pulse duration did not affect the degradation, and thus results in lower energy costs. 0 5 10 15 20 25 30 35 40 60 0.0 0.2 0.4
0.6 0.8
1.0 0 5 10 15 20 -4 -3 -2 -1 0
c
/
c 0 treatment time (min) O 3
3 +
plasma (P d = 31
W) O
3 +
plasma (P d = 11
W) k plasma+O3 =
194.5 x
10 -3
min -1 k O3 =
88.2
x 10 -3 min -1
l n (c
/
c 0 ) a 0 10 20 30 40 50 60 0.0 0.2 0.4
0.6 0.8
1.0 1.2
0.0 0.2
0.4 0.6
0.8 1.0
1.2 O 3 O 3 + plasma (P d = 31 W) O 3 + plasma (P d = 11 W)
TOC
T O C
/
T O C 0 treatment time (min)
Cl
/ Cl M-theor C l / C l M -th e o r b
Fig. 1. a: Degradation of 2,4-D; b: Mineralization and dechlorination of 2,4-D solution during ozonation and plasma+O 3 treatment with plasma powers of 11 and 31 W [1] L.H. Nowell et al., Sci. Total Environ. 476–477 (2014) 144 [2] K. Ikehata and M.G. El-Din, Ozone: Sci. Eng. 27 (2005) 83 [3] S. Chiron et al., Water Res. 34 (2000) 366 [4] M. Magureanu et al., Chemosphere 165 (2016) 507 [5] D.B. Donald et al., Environ. Health Perspect. 115 (2007) 1183 17
61 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Ultrafast Laser Diagnostics to Interrogate High Pressure, Highly
E. V. Barnat 1 P and A.Fierro A . FiP
1 P
P
P
P
The implementation and demonstration of laser-collision induced fluorescence (LCIF) generated in atmospheric pressure helium environments is presented in this communication. As collision times are observed to be fast (~ 10 ns), ultrashort pulse laser excitation (< 100 fs) of the 2 3 S to 3
3 P (388.9 nm) is utilized to initiate the LCIF process. Both neutral induced and electron induced components of the LCIF are observed in helium afterglow plasma as the reduced electric field (E/N) is tuned from < 0.1 Td to over 5 Td. Under the discharge conditions presented in this study (640 Torr He), the lower limit of electron density detection is ~ 10 12 e/cm 3 . Spatial profiles of the 2 3
resolving capabilities of the LCIF method.
Diagnostics play a key role in assessing our understanding of processes that occur in low- temperature plasmas by benchmarking predictive capabilities as well as through discovering otherwise unexpected behaviors. As the perceived landscape of low-temperature plasma science evolve and challenges become more complex (high densities, shorter lifetimes, more reaction pathways), a broad range of diagnostic capabilities are needed to provide a sufficiently complete picture of the plasma. Therefore, new methods need to be developed and made available to facilitate research efforts of the low-temperature plasma community. In this presentation, we described continued efforts to further the state-of-the-art in plasma diagnostics. To further the develop of the laser-collision induced fluorescence (LCIF) method [1] for use in such plasmas, a 640 Torr helium discharge, in a point-to-point configuration (Figure 1a) is studied. A key and potentially transformative element of the ongoing effort is the utilization of short pulse (~100 fs) laser to perform the initiation of the LCIF process (Figure 1a). For the presented data, LCIF is observed for 10 ns, starting ~ 1 ns before laser excitation. To demonstrate the ability of the of the LCIF method to interrogate spatial and temporal evolution of a plasma, the evolution of a 640 Torr helium afterglow plasma in response to a 250 ns high- voltage excitation event (Figure 1b) is studied. It is observed that two excitation fronts are present during the formation of the plasma channel and that behind these fronts resides regions of higher electron density. As the electron density builds, the velocity of the front launched from the cathode (lower electrode) accelerates due to increased localized E/N. The successful development of the LCIF method in atmospheric pressure plasma environments will be presented in an upcoming fast- track communication [2].
This work was supported by the Office of Fusion Energy Science at the U.S. Department of Energy under contracts DE-AC04-94SL85000 and DE- SC0001939.
[1] E. V. Barnat and K. Frederickson, Plasma Sources Sci. Technol. 19 (2010) 055015. [2] E. V. Barnat and A. Fierro, J. Phys. D (accepted)
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(a)
Time(ns) A x ial pos
it ion (
m m ) 0 200
400 0 2 4 6 8 Metastables Electrons Fronts
(b) Fig. 1 – (a) Laser-collision induced fluorescence concept and set-up utilized in studies. (b) Spatial and temporal evolution of helium afterglow plasma in response to 250 ns voltage pulse. 62
XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
S. Béchu P 1 P , UF F. Biggins P 1 P , J. Angot 1 P , S. Aleiferis 2 , P. Svarnas 2 , Yu. A. Lebedev 3 ,
V. A. Shakhatov 3 , A. Bès 1 , L. Bonny 1 , D. Fombaron 1 , A. Simonin 4 , A. Lacoste 1
P 1 P
2 High Voltage Lab., Electrical & Computer Engineering Dept, University of Patras, Rion-Patras, Greece 3 Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences (TIPS RAS), Moscow, Russia 4 CEA, IRFM, F-13108 St Paul lez Durance, France
The possibility of enhancing the extracted negative ion (H-/D-) current due to plasma-surface interactions on selected materials (potential alternatives of Cs in NBI for tokamak), is herein demonstrated. Current results, from plasmas sustained at a few mTorr by ECR dipolar plasma sources, as obtained with laser photodetachment at 1064 nm, demonstrate that, when tungsten material faces plasma it induces an obvious enhancement of the negative ion density. An extracting system using magnetic cores and three cooled electrodes are used to evaluate effects of the material itself and its relative position in the plasma, on the extracted current. The influence of the dimensions and geometry of the extracting aperture on the beam intensity, are also studied.
The ignition of fusion reactions in future reactors requires the injection in the bulk plasma of high- energy high power deuterium neutral beams (34 MW of 1 MeV D° beams on ITER, the international tokamak). These systems, called neutral beam injectors (NBI), are based on the acceleration of intense deuterium negative ion (NI) beams, followed by a neutralization in D 2 gas. These injectors require caesium to reach the demanded current intensity of 55 A. Despite its high efficiency to increase the negative ion extracted current, caesium induces a potential contamination of the accelerator resulting in high voltage breakdowns Hence, an alternative material becomes mandatory to achieve the negative ion current specifications of NBI designed for ITER.
LPSC has a long collaboration with CEA-Cadarache (in charge of French scientific research on NBI) searching for alternatives to Cs as a negative ion enhancers. LPSC operates electron cyclotron resonance (ECR) plasma at low power intake (up to 0.2 kW), while High Voltage Laboratory (Patras) investigates identical ECR plasma at higher power (up to 1 kW). Collaboration with the Topchiev Institute (Moscow), allows the development of optical emission spectroscopy diagnostics, as essential for considering plasma-surface interactions. 3. Experimental setup ROSAE-III is a stainless steel cylindrical plasma reactor [1] (152 mm in diameter and 214 mm long) developed at the LPSC. It is operated with dipolar plasma sources [2] at low pressure (< 25 mTorr). A cylindrical wall-coverage of borosilicate glass (Pyrex TM
plates made of the same material, can be housed in ROSAE III. Hence, hydrogen plasma can be confined in a chamber of either low (γ H = 0.005; Pyrex TM at 280 K) or moderate (γ H = 0.1-0.5; stainless steel) recombination coefficient. Studied materials are mounted on the Pyrex TM surface to face the H 2 /D 2 plasma. Absolute negative ion density has been already measured inside ROSAE-III by laser photodetachment at 1064 nm. Furthermore, recently, an extracting device has been designed, following 3D modelling (COMSOL software [3]), and it is being implemented for measurements of the negative current extracted from the plasma. It consists of three cooled electrodes. Two magnetic cores are used to prevent electrons from being co- extracted with negative ions.
The above experimental device should validate recent results of photodetachment measurements that shown a significant enhancement, by a factor 2.5, of the negative ion density in the bulk plasma when tungsten coverage is used. It will not only allow to assess the effect of the materials nature (tungsten, tantalum, and graphite) on the extracted currents but also to determine its best location with respect to the extracting aperture to maximize the negative ion current.
[1] S. Bechu et al., Phys. Plasmas. 20, (2013). [2] A. Lacoste et al., Plasma Sources Sci. T 11, 407 (2002).
[3] https://www.comsol.fr/ #18
63 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal Application of plasma-bullet propagation to hydrophilic treatments of an interconnected porous scaffold M. Oshiro 1 , T. Shirafuji 1 , K. Orita 2 , Y. Hirakawa 2 , H. Toyoda 2 UPPP
1 Deparment of physical Electronics and Informatics, Graduate School of Engineering, Osaka City University, Osaka, Japan 2 Department of Orthopedic Surgery, Graduate School of Medicine, Osaka City University, Osaka, Japan P An atmospheric pressure plasma jet employing dielectric barrier discharge of helium gas is known to be a source of plasma bullets, which propagate in high-purity helium gas channels. A plasma bullet propagates to the direction independent of gas-flow direction, and nicely separated when they encounter branches of gas channels. We have applied these characteristics of plasma bullets to hydrophilic treatment of internal surfaces of an interconnected porous scaffold. The scaffold employed in this work is a hydrophobic treated glass filter with a thickness of 3.15 mm and a pore-channel diameter of 160-250 μm. Plasma bullets injected from one side of the scaffold have penetrate it and ejected from the other side. Water permeability of the scaffold has been markedly improved after the treatment with the plasma-bullet penetration. 1. Introduction Atmospheric pressure plasma jets (APPJs) have been widely used for various surface treatments. Its unique nature involving “plasma bullets” [1] may be used for the treatment of internal surfaces of an interconnected porous scaffold used in bone- regeneration. There are few reports which discuss utilization of plasma bullets for such treatment, while there are extensive works using low pressure plasma [2] or those using an APPJ as a simple jet [3]. 2. Experimental Setup We have irradiated a helium APPJ to a hydrophobic treated glass filter, instead of expensive HA or β-TCP, of which thickness and pore channel diameter are 3.15 mm and 160-250 μm, respectively.
Figure 1 show time-evolution of plasma bullets on the back side of the APPJ-irradiated glass filter, which indicates that the bullets penetrate the glass filter and exit out of its back side. Figures 2(a) and 2(b) show that water permeability of the back side of the glass filter before and after the treatment for 10 min. We can see marked improvement in water permeability of the hydrophobic glass filter after the treatment. These results indicate that the internal surfaces of the hydrophobic glass filter have become hydrophilic by propagation of plasma bullets. Acknowledgements This work was partly supported by JSPS MEXT KAKENHI Grant Numbers 15H03585 and 15K13391. References [1] M. Teschke et al, IEEE Trans. Plasma Sci. 33, 310 (2005). [2] D.-S. Lee et al, J. Phs. D 45, 372001 (2012). [3] I. Trizio et al, Plasma Process. Polym. 12, 1451 (2015).
Fig. 1 Propagation of plasma bullets ejected from the glass filter. + 60 ns + 80 ns + 100 ns 5 mm + 0 ns + 20 ns + 40 ns backside of porous dielectric Fig. 2 Water permeability of the glass filter before and after the plasma-bullet treatment.
14 64 XXXIII ICPIG, July 9-14, 2017, Estoril/Lisbon, Portugal
Bubble formation in the discharge between planar and needle electrodes via laser ablation-induced cavitation bubble
K. Sasaki and Y. Takahashi P
Division of Quantum Science and Engineering, Hokkaido University, Sapporo, Japan
We observed the formation of a bubble in the discharge process between needle and planar electrodes. A unique experimental condition was that a cavitation bubble, which was induced by liquid-phase laser ablation, was positioned between the electrodes. When the distance between the needle electrode and the gas-liquid boundary of the cavitation bubble became close, we observed the formation of an additional bubble from the tip of the needle electrode. The discharge occurred when the needle electrode and the cavitation bubble was connected by the additional bubble. It should be emphasized that the bubble formation was not induced by the Joule heating of water, since we observed the bubble formation even when the current through the electrode was negligible.
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