Plasma Bullet as a Plasma Diffusion Wave-Packet in Plasma Jets

Guangsup Cho,Eun-Ha Choi,Han Sup Uhm IEEE 2013 IEEE transactions on plasma science Vol.41 No.6

<P>The propagation of a plasma bullet in a plasma jet is described under the base of plasma fluid theory in terms of the plasma drift, the gas flow, and the plasma diffusion. The analysis reveals that the plasma bullet originates from the electrostatic diffusion wave in plasma propagating in the plasma column of jets. The plasma diffusion waves, electron waves, and ion waves propagate in the form of a wave-packet modulated by the operation frequency of the voltage pulse. The waves have the dispersion relation of ω ~ <I>ku</I><SUB>αφ</SUB>, and the wavelength has the order of Debye length λ<I>D</I> ~ 10<SUP>-4</SUP> m as <I>k</I><SUP>2</SUP> λ<I>D</I><SUP>2</SUP> ~ 1. The phase velocity is <I>u</I><SUB>αφ</SUB> ~ (<I>u</I><SUB>α</SUB><I>d</I> +<I>ub</I>+<I>un</I>+κ<SUB>α</SUB><I>un</I>) with the mobility ratio of κ<I>e</I>=|μ<I>e</I>/μ<I>i</I>| for electrons (α = <I>e</I>) and κ<I>i</I>=1 for ions (α = <I>i</I>). The terms <I>ued</I>, <I>uid</I>, <I>ub</I>, and <I>un</I> represent the electron drift velocity, the ion drift velocity, the gas blowing velocity, and the plasma diffusion velocity, respectively. The waves are modulated to be the wave-packet of <I>d</I>ω ~ <I>ugdk</I> with the group velocity of <I>ug</I> ~ <I>cs</I><SUP>2</SUP>/<I>un</I> ~ (10<SUP>4</SUP>-10<SUP>5</SUP>)m/s, where the acoustic velocity is <I>cs</I> ~ 10<SUP>3</SUP> m/s and the diffusion velocity is <I>un</I> ~ (10-10<SUP>2</SUP>)m/s estimated in a plasma jet device.</P>

High-Efficiency Gasification of Low-Grade Coal by Microwave Steam Plasma

Uhm, Han Sup,Na, Young Ho,Hong, Yong Cheol,Shin, Dong Hun,Cho, Chang Hyun,Park, Young Ki American Chemical Society 2014 ENERGY AND FUELS Vol.28 No.7

<P>High-power steam plasma for heating the coal powders were developed, where the magnetron power at 915 MHz was available up to 75 kW. The steam plasma itself is an impedance load, which depends on physical conditions, including the microwave power. By monitoring the minimum reflected power, the optimum injection rate of the steam and the corresponding reflected power ratio in terms of the microwave power was found, showing that most of the microwave power is absorbed by the torch plasma with a minimal reflected wave-power of less than a few percent, once the plasma torch was ignited. Indonesian brown coal with high ash content is gasified by two microwave steam plasmas heating up the gas temperature in a reaction chamber of 1145 L in a swirl-type gasifier. With additional heating of synthetic gas from a partial oxidation, the inner temperature of the gasifier can reach to 1700 °C. The carbon conversion rate at the average chamber temperature of 1640 °C is almost 100%, ensuring a complete gasification of carbon in a low-grade coal. The cold gas efficiency is 84%, very high in a relatively small gasifier like the experiment here. The total calorific power of the synthetic gas is 500 kW. Therefore, this gasification system may serve as a moderately sized power plant due to its compactness and lightweight nature. A power plant utilizing low-grade coal would be useful in rural or sparsely populated areas without access to a national power grid.</P>

플라즈마를 이용한 물 분해 및 수소 제조

엄환섭(Uhm Han Sup),강정구(Kang Jung Goo),홍용철(Hong Yong Cheol) 한국에너지학회 2003 한국에너지공학회 학술발표회 Vol.2003 No.-

Electron density characterization of inductively-coupled argon plasmas by the terahertz time-domain spectroscopy

Jang, Dogeun,Uhm, Han Sup,Jang, Donggyu,Hur, Min Sup,Suk, Hyyong IOP 2016 Plasma sources science & technology Vol.25 No.6

<P>Inductively-coupled plasmas (ICP) in the high electron density regime of the order of 10<SUP>13</SUP> cm<SUP>−3</SUP> are generated and their electron density characteristics are investigated by the terahertz time-domain spectroscopy (THz-TDS) method. In this experiment, the plasma was produced by RF (13.56 MHz) with an applied RF power of 300–550 W and the argon gas pressure was in the range of 0.3–1.1 Torr. We generated the THz wave by focusing a femtosecond laser pulse in air with a DC electric field. As a plasma diagnostic tool, the THz-TDS method is found to successfully provide the plasma density information in the high-density regime, where other available plasma diagnostic tools are very limited. In addition, the analytical model based on the ambipolar diffusion equation is compared with experimental observations to explain the behavior of the electron density in the ICP source, where the plasma density is shown to be related to the applied RF power and gas pressure. The analytical result from the model is found to be in good agreement with the THz-TDS result.</P>

Plasma Propagation Speed and Electron Temperature in Slow Electron Energy Non-thermal Atmospheric Pressure Indirect-Plasma Jet

Suanpoot, Pradoong,Gook-Hee Han,Sornsakdanuphap, Jirapong,Han Sup Uhm,Guangsup Cho,Eun Ha Choi Institute of Electrical and Electronics Engineers 2015 IEEE transactions on plasma science Vol. No.

<P>Space- and time-resolved discharge-images from a nonthermal atmospheric-pressure indirect-plasma jet have been observed using a high-speed single-frame camera to investigate the electron temperature. The propagation velocity of the indirect Ar-plasma along the plasma column has been shown to be on the order of 10<SUP>4</SUP> m/s, and that corresponds to an ion acoustic velocity on the order of 10<SUP>2</SUP> m/s. Plasma has been generated by varying input discharge voltages from 2.0 to 4.0 kV at a driving frequency of 40 kHz. Particularly, the average electron temperature in slow electron energy nonthermal atmospheric-pressure indirect-plasma jet has been found to be about 0.3 eV.</P>

Propagation of Plasma Diffusion Wave According to the Voltage Polarity in the Atmospheric Pressure Plasma Jet Columns

Guangsup Cho,Yun-Jung Kim,Eun Ha Choi,Han Sup Uhm IEEE 2014 IEEE transactions on plasma science Vol.42 No.11

<P>Propagation of optical signals measured along the atmospheric plasma-jet column according to the operational voltage polarity is analyzed with the electrostatic plasma-diffusion wave in terms of the characteristic speeds of plasma fluids, such as the plasma drift u<SUB>d</SUB>, the gas flow u<SUB>b</SUB>, and the plasma diffusion u<SUB>n</SUB>. For the positive voltage, the ion wave propagates with the wave-packet velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB>, where c<SUB>s</SUB> is the acoustic velocity along the whole column of plasma jet without any restrictions. The electron wave propagates backward with the group velocity of electron drift with u<SUB>g</SUB> ~ -u<SUB>ed</SUB> toward the high voltage electrode right after passing of the frontline of ion wave-packet. For the negative voltage, the ion wave propagates on the high ionization column with the wave-packet velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB>. The electron wave propagates forward while its propagation mode varies from the group velocity of u<SUB>g</SUB> ~ c<SUB>s</SUB><SUP>2</SUP>/u<SUB>n</SUB> on a region of high electric field to the velocity of electron drift with ug ~ +u<SUB>ed</SUB> on a low field region.</P>

Plasma Diffusion Along a Fine Tube Positive Column

Guangsup Cho,Jung-Hyun Kim,Jong-Mun Jeong,Ha-Chung Hwang,Dong-Jun Jin,Je-Huan Koo,Eun-Ha Choi,Verboncoeur, J.P.,Han-Sup Uhm IEEE 2009 IEEE transactions on plasma science Vol.37 No.3

<P>The propagation velocity of light emission is observed to be u<SUB>p</SUB> ~0.92 times10<SUP>+5</SUP> m/s along a tube of an inner diameter r<SUB>o</SUB> ~1.5 times10<SUP>-3</SUP> m with an external electrode fluorescent lamp filled with 97% Ne and 3% Ar at a total pressure of 30 torr, a mercury-free lamp without phosphor coating the inside glass wall. The origin of this propagation is shown to be ambipolar diffusion with a plasma diffusion speed of u<SUB>p</SUB> ~ (4.8/r<SUB>o</SUB>)D<SUB>a</SUB> for diffusion coefficient D<SUB>a</SUB> along the positive column. When a high voltage magnitude is applied at the external electrode, a high-density plasma is generated inside the hollow electrode, and the plasma diffuses along the positive column toward the ground electrode.</P>

대기압 플라즈마와 응용

엄환섭,Uhm Han-Sup 한국진공학회 2006 Applied Science and Convergence Technology Vol.15 No.2

지표면에서 플라즈마는 전기방전에 의하여 만들어낸다. 그래서 대부분의 플라즈마 발생은 1백만분의 1기압보다 더 낮은 기압에서 발생하고 있었다. 그러나 많은 플라즈마 응용은 고기압에서 발생한 플라즈마를 요구하고 있다. 진공펌프와 같은 고가의 장비를 피하기 위하여 과학자들은 1기압이나 그이상의 압력에서 플라즈마를 발생하는 연구를 하기 시작했다. 많은 량의 제료 공정, 환경보호와 개선, 그리고 고효율 에너지 창출과 이용 등의 분야에 플라즈마를 사용할 때에는 오직 더 많은 량의 플라즈마를 더욱 값싸게 만들 때에만 가능한 것이다. 우리는 따라서 고기압에서 플라즈마를 만들어내는 새로운 방법을 개발하고 이러한 플라즈마가 21세기 산업에 적용될 수 있는 새로운 기반을 구축하는 연구를 수행하고 있다. 이러한 기술은 미래의 재료 공정이나, 환경 그리고 에너지 분야에 지대한 영향을 미칠 것으로 생각한다. Plasmas can be made by electrical discharge on earth. Most of the plasmas on earth have been generated in low pressure environments where the pressure is less than one millionth of the atmospheric pressure. However, there are many plasma applications which require high pressure plasmas. Therefore, scientists start research on plasma generation at high pressure to avoid use of expensive vacuum equipments. Large-volume inexpensive plasmas are needed in the areas of material processing, environmental protection and improvement, efficient energy source and applications, etc. We therefore developed new methods of plasma generations at high pressure and carried out research of applying these plasmas to high tech industries representing 21 century. These research fields will play pivotal roles in material, environmental and energy science and technology in future.

INVESTIGATION OF ELECTRON TEMPERATURE OF NE IN ATMOSPHERIC PRESSURE NON-THERMAL INDIRECT BIOPLASMA JET

Jirapong SORNSAKDANUPHAP,Pradoong SUANPOOT,Han Sup UHM,Guangsup CHO,Eun Ha CHOI 한국진공학회 2015 한국진공학회 학술발표회초록집 Vol.2015 No.2

Microplasma jet at atmospheric pressure

Hong, Yong Cheol,Uhm, Han Sup American Institute of Physics 2006 APPLIED PHYSICS LETTERS Vol.89 No.22