Breakdown Characteristics of Electrical Discharges in High-Density Helium Near the Critical Point

Muneoka, Hitoshi; Urabe, Keiichiro; Stauss, Sven; Terashima, Kazuo

doi:10.7567/apex.6.086201

Cited by 16 publications

(12 citation statements)

References 36 publications

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“…Details of the cryoplasma chamber system have been introduced elsewhere. 9,11,12,17,24) The DBD electrode was a parallel-plate configuration made of stainless steel electrodes with dimensions of 10 × 5 mm 2 and polyimide sheets with a thickness of ∼0.125 mm placed on the surfaces of both electrodes, thereby acting as dielectrics. The discharge gas gap between the polyimide sheets was 0.5 mm.…”

Section: Methodsmentioning

confidence: 99%

Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

Urabe

Muneoka

Stauss

et al. 2015

Jpn. J. Appl. Phys.

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Cryoplasmas, which are plasmas whose gas temperatures are below room temperature (RT), have shown dynamic changes in their physical and chemical characteristics when the gas temperature in the plasmas (T gp ) was decreased from RT. In this study, we measured the temporal behavior of helium metastable (He m ) atoms generated in a parallel-plate dielectric barrier discharge at ambient gas temperatures (T ga ) of 300, 100, and 14 K and with a gas density similar to atmospheric conditions by laser absorption spectroscopy. The increments of T gp to T ga were less than 20 K. We found from the results that the He m lifetime and maximum density become longer and larger over one order of magnitude for lower T ga . The reasons for the long He m lifetime at low T ga are decreases in the rate coefficients of three-body He m quenching reactions and in the amounts of molecular impurities with boiling points higher than that of He.

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Section: Methodsmentioning

confidence: 99%

Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

Urabe

Muneoka

Stauss

et al. 2015

Jpn. J. Appl. Phys.

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“…For example, in SC-He, DC breakdown voltage was seen to drop in the vicinity of the critical point under the quite narrow gap of 3 m under a quasi-uniform electric field [8], [9], while in SC-CO2, this…”

Section: Introductionmentioning

confidence: 97%

Effect of Voltage Rise Rate on Streamer Branching and Shock Wave Characteristics in Supercritical Carbon Dioxide

Furusato

Ota

Fujishima

et al. 2016

IEEE Trans. Plasma Sci.

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Abstract-This paper reports on dependence of voltage rise rate on positive streamer branching and shock waves in supercritical carbon dioxide. Voltages with rise rates of 0.21 and 4.5 kV/ns were applied to a needle-to-plane electrode. Pre-breakdown phenomena involving streamer growth and shock wave propagation were observed by means of a shadowgraph method. Results show that the spread angle of the streamer at the needle tip under 4.5 kV/ns was nearly twice as large as that under 0.21 kV/ns. The discharge may initiate without density reduction due to electrostrictive force. While shock wave Mach number was little affected by the voltage rise rate, it increased by increasing the negative voltage peak. Consequently, the velocity of shock wave is presumed to be influenced by population of the vibrational state of carbon dioxide.Index Terms-Nanosecond pulsed discharge, positive streamer, shock waves, supercritical carbon dioxide, shadowgraph method, electrostrictive force. I. INTRODUCTIONISCHARGE plasma in supercritical (SC) fluid displays excellent controllability of both physical properties and chemical reactivity and is thus anticipated in new chemistry synthesis fields such as phenol polymerization [1], metallic oxide nanomaterials [2], carbon nanomaterials [3] and nanodiamonds [4]. Recently, the study of a pulsed power switch using SC-CO2 and SC-N2 has been launched as a novel application [5]- [7]. Understanding of streamer discharge and shock waves in SC fluids is of importance in the development of a SC reactor.Several studies related to direct current (DC) breakdown characteristics have been reported. For example, in SC-He, DC breakdown voltage was seen to drop in the vicinity of the critical point under the quite narrow gap of 3 m under a quasi-uniform electric field [8], [9], while in SC-CO2, thisThe manuscript was submitted in March 2016 "This work was supported by Grant-in-Aid for Research Activity Start-up (No. 26889048) and by TEPCO Memorial Foundation".T. Furusato, T. Fujishima, and T. Yamashita are with the Graduate School of Engineering, Nagasaki University, Nagasaki 852-8521, Japan (t-furusato@nagasaki-u.ac.jp).M. Ota, T. Sakugawa, S. Katsuki and H. Akiyama are with the Graduate School of Science and Technology, Kumamoto University, . critical anomaly did not occur under gaps ranging from 80 to 200 m under a non-uniform electric field [10], [11]. Despite these great discrepancies, little attention has been given to the study of pre-breakdown phenomena in SC fluids.No unified pre-breakdown theory in dense medium yet exists due to its complex mechanism, with both the direct impact ionization model and bubble theory independently proposed through many studies [12], [13]. However, recent research has suggested a new pre-breakdown mechanism: ultra-short pulsed voltage in dielectric liquids [14]-[16], which is that nano-sized pores created by the electrostrictive force in the vicinity of the needle tip affects the pre-breakdown mechanism in dielectric liquids with pulse widths ranging from sub-nanosec...

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“…Consequently, an antagonistic action between a molecular attraction and a thermal agitation under a condition close to its critical condition causes an increase in density fluctuation which often affects breakdown characteristics in SCfluids. A local decrease of breakdown voltage appears under SC conditions close to critical condition of medium for DC breakdown in SC-Xe, CO2 and H2O at the 1 μm gap [7], pulsed breakdown in SC-air at 25 μm gap [8], and DC breakdown in SC-He at 3 μm gap [9,10]. However, the anomaly of breakdown voltage around critical condition disappears under longer electrode gap, e.g.…”

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confidence: 93%

Anomalous plasma temperature at supercritical phase of pressurized CO<inf>2</inf> after pulsed breakdown followed by large short-circuit current

Furusato

Ashizuka

Kamagahara

et al. 2018

IEEE Trans. Dielect. Electr. Insul.

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The relation between breakdown characteristics and plasma temperature of a pulsed arc discharge in highly pressurized CO2 was investigated up to a supercritical phase. A transient arc discharge was generated by applying nanosecond pulsed voltage with a rising rate of 0.7 kV/ns to a point-to-plane gap of 1 mm. The breakdown voltage, arc current, and consumption energy increased with the CO2 density in the gas phase. However, they were constant at the CO2 densities in the supercritical phase. The plasma temperature determined from the blackbody radiation ranged from 8000 to 12000 K and its dependence with respect to the CO2 density was all similar to the breakdown voltage, arc current, and consumption energy characteristics except under the critical density of CO2 (469 kg/m 3). Although the breakdown voltage, arc current, and consumption energy in supercritical phase were also constant against the CO2 density, the plasma temperature demonstrated a local decrease around the critical density. The anomaly of the plasma temperature is consistent with the calculated result of the isochoric specific heat of CO2 which has a local maximum around the critical density. Index Terms-Supercritical fluids, pulsed power, breakdown, pulsed arc discharge, optical emission spectroscopy. 1 INTRODUCTION RECENTLY, plasmas in supercritical (SC) fluids have been studied for use as an arc extinguishing medium [1, 2] and have drawn attention as a novel chemical synthesis method, e.g. phenol polymerization [3], metallic oxide nanomaterials [4], carbon nanomaterials [5], and nanodiamonds [6]. Understanding breakdown characteristics in the SC-fluids is of importance for the design of high-pressure chambers. In the supercritical fluid condition, a medium exceeds specific critical pressure and Manuscript

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Breakdown Characteristics of Electrical Discharges in High-Density Helium Near the Critical Point

Cited by 16 publications

References 36 publications

Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

Laser absorption spectroscopy diagnostics of helium metastable atoms generated in dielectric barrier discharge cryoplasmas

Effect of Voltage Rise Rate on Streamer Branching and Shock Wave Characteristics in Supercritical Carbon Dioxide

Anomalous plasma temperature at supercritical phase of pressurized CO<inf>2</inf> after pulsed breakdown followed by large short-circuit current

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