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Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling.

Lee HC, Chung CW - Sci Rep (2015)

Bottom Line: It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis.This hysteresis was presented in the plasma balance model where the EED is considered.Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Hanyang University, Seoul, 133-791, Republic of Korea.

ABSTRACT
Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

No MeSH data available.


Related in: MedlinePlus

Evolution of the electron energy probability function (EEPF) due to heating mode transition at the Ar Ramsauer gas.(a–d) The measured EEPFs at each region (I)-(IV) in the Ar gas discharge of 250 mTorr of Fig. 1b. In the low plasma density mode, the EEPFs show the Druyvesteyn distribution (Fig. 2a,d), while the EEPFs are the Maxwellian distrution in the high density plasma mode (Fig. 2b,c). The Druyvesteyn distribution is caused by the energy dependent electron heating at Ramsauer gas. (e) Elastic collision cross sections at Ar and He. The Ar has minimum cross section for electron-neutral collisions, which is a result by the quantum-mechanical effect, called Ramsauer-Townsend scattering minimum.
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f2: Evolution of the electron energy probability function (EEPF) due to heating mode transition at the Ar Ramsauer gas.(a–d) The measured EEPFs at each region (I)-(IV) in the Ar gas discharge of 250 mTorr of Fig. 1b. In the low plasma density mode, the EEPFs show the Druyvesteyn distribution (Fig. 2a,d), while the EEPFs are the Maxwellian distrution in the high density plasma mode (Fig. 2b,c). The Druyvesteyn distribution is caused by the energy dependent electron heating at Ramsauer gas. (e) Elastic collision cross sections at Ar and He. The Ar has minimum cross section for electron-neutral collisions, which is a result by the quantum-mechanical effect, called Ramsauer-Townsend scattering minimum.

Mentions: When the input power or the plasma power decreases, the plasma density still remains at the H mode until plasma power of 12.56 W at input power of 23 W. A slight decrease in the input power from 23 W to 22 W results in an abrupt change of the discharge characteristic to an E mode with low plasma density. Through this transition of the discharge mode, there is a huge hysteresis with the trajectory [I→II→III→IV] in case of the Ar gas of 250 mTorr (Fig. 1b). In He gas discharges, it is noted that the hysteresis is not observed at either a high gas pressure of 300 mTorr (Fig. 2c) or a low gas pressure of 40 mTorr (not presented here). This direct experimental evidence implies that the plasma has bi-stability characteristic with strong nonlinearity only at the high pressure Ramsauer gas discharge.


Effect of Electron Energy Distribution on the Hysteresis of Plasma Discharge: Theory, Experiment, and Modeling.

Lee HC, Chung CW - Sci Rep (2015)

Evolution of the electron energy probability function (EEPF) due to heating mode transition at the Ar Ramsauer gas.(a–d) The measured EEPFs at each region (I)-(IV) in the Ar gas discharge of 250 mTorr of Fig. 1b. In the low plasma density mode, the EEPFs show the Druyvesteyn distribution (Fig. 2a,d), while the EEPFs are the Maxwellian distrution in the high density plasma mode (Fig. 2b,c). The Druyvesteyn distribution is caused by the energy dependent electron heating at Ramsauer gas. (e) Elastic collision cross sections at Ar and He. The Ar has minimum cross section for electron-neutral collisions, which is a result by the quantum-mechanical effect, called Ramsauer-Townsend scattering minimum.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4612307&req=5

f2: Evolution of the electron energy probability function (EEPF) due to heating mode transition at the Ar Ramsauer gas.(a–d) The measured EEPFs at each region (I)-(IV) in the Ar gas discharge of 250 mTorr of Fig. 1b. In the low plasma density mode, the EEPFs show the Druyvesteyn distribution (Fig. 2a,d), while the EEPFs are the Maxwellian distrution in the high density plasma mode (Fig. 2b,c). The Druyvesteyn distribution is caused by the energy dependent electron heating at Ramsauer gas. (e) Elastic collision cross sections at Ar and He. The Ar has minimum cross section for electron-neutral collisions, which is a result by the quantum-mechanical effect, called Ramsauer-Townsend scattering minimum.
Mentions: When the input power or the plasma power decreases, the plasma density still remains at the H mode until plasma power of 12.56 W at input power of 23 W. A slight decrease in the input power from 23 W to 22 W results in an abrupt change of the discharge characteristic to an E mode with low plasma density. Through this transition of the discharge mode, there is a huge hysteresis with the trajectory [I→II→III→IV] in case of the Ar gas of 250 mTorr (Fig. 1b). In He gas discharges, it is noted that the hysteresis is not observed at either a high gas pressure of 300 mTorr (Fig. 2c) or a low gas pressure of 40 mTorr (not presented here). This direct experimental evidence implies that the plasma has bi-stability characteristic with strong nonlinearity only at the high pressure Ramsauer gas discharge.

Bottom Line: It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis.This hysteresis was presented in the plasma balance model where the EED is considered.Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical Engineering, Hanyang University, Seoul, 133-791, Republic of Korea.

ABSTRACT
Hysteresis, which is the history dependence of physical systems, is one of the most important topics in physics. Interestingly, bi-stability of plasma with a huge hysteresis loop has been observed in inductive plasma discharges. Despite long plasma research, how this plasma hysteresis occurs remains an unresolved question in plasma physics. Here, we report theory, experiment, and modeling of the hysteresis. It was found experimentally and theoretically that evolution of the electron energy distribution (EED) makes a strong plasma hysteresis. In Ramsauer and non-Ramsauer gas experiments, it was revealed that the plasma hysteresis is observed only at high pressure Ramsauer gas where the EED deviates considerably from a Maxwellian shape. This hysteresis was presented in the plasma balance model where the EED is considered. Because electrons in plasmas are usually not in a thermal equilibrium, this EED-effect can be regarded as a universal phenomenon in plasma physics.

No MeSH data available.


Related in: MedlinePlus