Reports of potential applications of Cold Plasma (CP) in agriculture have increased significantly... more Reports of potential applications of Cold Plasma (CP) in agriculture have increased significantly in recent years. As one fast, economic, and pollution-free method, CP treatment has been found to promote seed germination and plant yield. Cold plasma (CP), non-thermal technology, can be generated by radio frequency or microwave sources. It is well known to us that rice (Oryza sativa L) is a common cereal and the staple food over half the world's population. Different researchers reported that there is a positive impact on seed germination and plant yield of rice. Our objective is to develop an eco-friendly and cost efficient technology based on CP technique to improve the seed germination and plant yield of rice. Numerous works has been carried out to develop some statistical models, in which historical data on crop yields and weather are used to calibrate relatively simple regression equations. Three main types of statistical approaches are found in the literature: time series methods, panel methods and cross-section methods. We are planning to develop a statistical model which is basically based on the multi linear regression model to study the crop yield specially for rice. In the present work, a detail review on different experimental works on CP technique for improvement of seed germination and plant yield of rice as well as different statistical models will be described.
Abstract The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic fie... more Abstract The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic field is studied in our present work. It is observed that the ratio of electron to ion saturation current shows almost identical behavior with that of unmagnetized hydrogen plasma when rL > 10rp (here rL: Larmor radius and rp: probe radius). At magnetic field strength, B = 594 gauss, the electron temperature (Te) shows an overestimated value up to ~35–40%, whereas at B ≤ 37 gauss, Te shows around ≤10% overestimated value w.r.t. unmagnetized case. A bi-Maxwellian electron energy probability function is observed for entire magnetic field range for both pristine and dust containing hydrogen plasma. The bulk (cold) electron collection by the Langmuir probe is strongly suppressed whereas the higher energetic electron collection remains unaffected in presence of magnetic field. In presence of dust grains, it is found that the low energy electron population decreases even more than the magnetized plasma and the high-energy tail slightly increases compared to the pristine plasma. Graphical abstract
Проанализированы данные о вкладе метеорологических и синоптических условий в возникновение лесных... more Проанализированы данные о вкладе метеорологических и синоптических условий в возникновение лесных пожаров в Иркутской области. По результатам наблюдений метеорологических станций, расположенных в разных физико-географических районах Иркутской области, рассчитан показатель пожарной опасности по В.Г. Нестерову в периоды апрель-сентябрь 2010-2015 гг. Этот показатель характеризует метеорологические условия исследуемой территории как усредненные по степени пожарной опасности. Выявлено, что наиболее благоприятные условия для возникновения лесных пожаров по времени наблюдаются в мае-июне и августесентябре, а в пространственном отношении-на севере Иркутской области и на побережье оз. Байкал, где отмечается наименьшее количество атмосферных осадков. Синоптический анализ летнего периода 2015 г. с большим числом лесных пожаров на Байкальской природной территории показал господствующее влияние блокирующих процессов, которые сопровождались редким выходом южных циклонов-основных поставщиков влаги в регион. В качестве предикторов лесных пожаров в Иркутской области наиболее высокую оправдываемость (≥70%) в теплый период 2015 г. имели значения температуры воздуха: у поверхности Земли, в нижней (АТ-850 гПа) и средней (АТ-500 гПа) тропосфере, потенциальной температуры на уровне АТ-850 гПа; аномалии геопотенциала АТ-500 гПа, относительной влажности воздуха и сумм атмосферных осадков.
Kognitive Beeinträchtigung und Depressivität im Alter 2 Zusammenfassung Kognitive Beeinträchtigun... more Kognitive Beeinträchtigung und Depressivität im Alter 2 Zusammenfassung Kognitive Beeinträchtigungen im Alter bedeuten nicht selten eine hohe psychische Belastung und können zu psychoreaktiven Verstimmungen führen. Wir untersuchen, inwieweit die belastenden Effekte kognitiver Verluste durch Bildungsressourcen abgemildert und ausgeglichen werden. An der Studie nahmen 201 ältere Personen teil, die das Diagnose-und Beratungsangebot des Gedächtniszentrums des Instituts für Psychogerontologie nutzten. Untersucht wurden die Zusammenhänge zwischen berichteten Beschwerden, kognitiver Leistung und Depressivität in drei Gruppen von dementen Patienten (n = 77), leicht kognitiv beeinträchtigten Patienten (MCI, n = 78) sowie nur subjektiv beeinträchtigten, gesunden Personen (n = 46). Die Ergebnisse zeigen, dass unabhängig von Gesundheit, Familienstand, und Demenzdiagnose die Zusammenhänge zwischen berichteten Beschwerden und Depressivität in Abhängigkeit von Bildungseinflüssen variieren. Zwar gingen berichtete Beschwerden generell mit erhöhtem Depressivitätserleben einher, dieser Zusammenhang war aber bei höher gebildeten Personen geringer. Bildungsressourcen können somit belastende Effekte subjektiver Leistungseinbußen auf die Befindlichkeit kompensieren.
SST-1 Tokamak has recently completed the 1st phase of up-gradation with successful installation a... more SST-1 Tokamak has recently completed the 1st phase of up-gradation with successful installation and integration of all its First Wall components. The First Wall of SST-1 comprises of ~ 3800 high heat flux compatible graphite tiles being assembled and installed on 132 CuCrZr heat sink back plates engraved with ~ 4 km of leak tight baking and cooling channels in five major sub groups equipped with ~ 400 sensors and weighing ~ 6000 kg in total in thirteen isolated galvanic and six isolated hydraulic circuits. The phase-1 upgradation spectrum also includes addition of Supersonic Molecular Beam Injection (SMBI) both on the in-board and out-board side, installation of fast reciprocating probes, adding some edge plasma probe diagnostics in the SOL region, installation and integration of segmented and up-down symmetric radial coils aiding/controlling plasma rotations, introduction of plasma position feedback and density controls etc. Post phase-I up-gradation spanning from Nov 2014 till June 2016, initial plasma experiments in up-graded SST-1 have begun since Aug 2016 after a brief engineering validation period in SST-1. The first experiments in SST-1 have revealed interesting aspects on the `eddy currents in the First Wall support structures influencing the `magnetic Null evolution dynamics’ and the subsequent plasma start-up characteristics after the ECH pre-ionization, the influence of the first walls on the `field errors’ and the resulting locked modes observed, the magnetic index influencing the evolution of the equilibrium of the plasma column, low density supra-thermal electron induced discharges and normal ohmic discharges etc. Presently; repeatable ohmic discharges regimes in SST-1 having plasma currents in excess of 65 KA (qa ~ 3.8, BT = 1.5 T) with a current ramp rates ~ 1.2 MA/s over a duration of ~ 300 ms with line averaged densities ~ 0.8 × 1019 and temperatures ~ 200 eV with copious MHD signatures have been experimentally established. Further elongation of the plasma duration up to one second or more with position and density feedback as well as coupling of Lower Hybrid waves are currently being persuaded in SST-1 apart from increasing the core plasma parameters with further optimizations and with wall conditioning.
Impurity control reduces the radiation loss from plasma and hence enhances the plasma operation. ... more Impurity control reduces the radiation loss from plasma and hence enhances the plasma operation. Oxygen and water vapors are the most common impurities in tokamak devices. Water vapour can be reduced with extensive baking while in order to have a significant reduction in oxygen it is necessary to use glow discharge condition (GDC). RF assisted glow discharge cleaning system will be implemented to remove low z impurities at PFC installed SST-1 vacuum vessel. A RF assisted Glow discharge conditioning is studied at laboratory to find the optimum operating parameters in a view to implement at SST-1 tokamak. Helium is used as a fuel gas in the present experiment. It is observed that the ultimate impurity level is reduced significantly below to the accepted level for plasma operation after RF assisted GDC. The experimental findings of RF assisted Glow discharge conditioning is discussed in details in this paper.
Knowledge of the real EEDF is of great importance in understanding the underlying physics of proc... more Knowledge of the real EEDF is of great importance in understanding the underlying physics of processes occurring at the magnetized plasma, such as the formation of transport barriers, cross-field diffusion coefficients and plasma–substrate interactions. In the present experiment, the application of Langmuir probe to evaluate EEPF in presence of magnetic fields within the range 594 –32 G is investigated. The data recorded for EEPFs in magnetic fields and in dust is acquired using current–voltage characteristics measured in low pressure hydrogen plasma. The values of plasma density, electron temperature and EEPF are evaluated with a single cylindrical Langmuir probe at different axial positions (1 cm to 6 cm) from the magnet. From the recent EEPF observations in presence of magnetic field, it shows a bi-Maxwellian EEPF structure at different magnetic fields. But at different magnetic field, it is observed that the low energy electron population changes whereas the high-energy electron population remains almost constant. EEPF measurement shows almost identical behaviour with the unmagnetized plasma when the larmour radius of electron is greater than or equal to 10 times of the probe radius.
The effect of external magnetic field on the Langmuir probe measurement and dust charging are stu... more The effect of external magnetic field on the Langmuir probe measurement and dust charging are studied in low-pressure hydrogen plasma. The experiment is performed in a dusty plasma device where plasma is created by the hot cathode filament discharge technique. A strong Strontium ferrite magnet is used inside the plasma, near the dust zone. The plasma parameters are measured at different distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where reL rP, riL iirP; the electron collection by the probe deviates strongly from the actual value, until reL 10rP. The observations of electron energy probability function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.
Some parametric studies like the effect of discharge current, plasma temperature and working pres... more Some parametric studies like the effect of discharge current, plasma temperature and working pressure on the charging of dust grains in hot cathode discharge plasma will be presented. The designing concepts of a novel experiment to produce negative hydrogen ions from Cesium coated dust particles and related preliminary studies with dust particles in hydrogen plasma will be presented. The aim of producing negative hydrogen ions is to devise the possibility of using such negative ions in Neutral Beam Injection Heating of Tokamak plasma. Refs: S.S. Kausik, M.Chakraborty, P. Dutta, M. Kakati and B.K. Saikia, Phys. Lett. A 372, 860 (2008)
Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasm... more Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasma device are reported. Addition of argon modifies plasma density, electron temperature, degree of hydrogen dissociation, dust current as well as dust charge. From the dust charging profile, it is observed that the dust current and dust charge decrease significantly up to 40% addition of argon flow rate in hydrogen plasma. But beyond 40% of argon flow rate, the changes in dust current and dust charge are insignificant. Results show that the addition of argon to hydrogen plasma in a dusty plasma device can be used as a tool to control the dust charging in a low pressure dusty plasma. (C) 2014 AIP Publishing LLC.
ABSTRACT The effect of electrostatic confinement on charging of dust grains has been studied in a... more ABSTRACT The effect of electrostatic confinement on charging of dust grains has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. The number of charges collected by dust grains is calculated both from the amount of deflection and floating potential. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.
Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungst... more Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungsten filaments and the permanent magnetic cage (1), which is grounded. The magnetic cage has a full line cusped magnetic field geometry used to confine the plasma elements. A cylindrical Langmuir probe is used to study the plasma parameters in various discharge conditions. The charge accumulated on
ABSTRACT In this study, the effect of magnetron target on different plasma parameters of Argon/Hy... more ABSTRACT In this study, the effect of magnetron target on different plasma parameters of Argon/Hydrogen (Ar - H2) direct current (DC) magnetron discharge is examined. Here, Copper (Cu) and Chromium (Cr) are used as magnetron targets. The value of plasma parameters such as electron temperature (kTe), electron density (Ne), ion density (Ni), degree of ionization of Ar, and degree of dissociation of H2 for both the target are studied as a function of input power and hydrogen content in the discharge. The plasma parameters are determined by using Langmuir probe and Optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. The obtained results show that electron and ion density decline with gradual addition of Hydrogen in the discharge and increase with rising input power. It brings significant changes on the degree of ionization of Ar and dissociation of H2. The enhanced value of electron density (Ne), ion density (Ni), degree of Ionization of Ar, and degree of dissociation of H2 for Cr compared to Cu target is explained on the basis of it's higher Ion Induced Secondary Electron Emission Coefficient (ISEE) value.
The effect of the electrostatic confinement potential on the charging of dust grains and its rela... more The effect of the electrostatic confinement potential on the charging of dust grains and its relationship with the plasma parameters has been studied in an electrostatically plugged multicusp dusty plasma device. Electrostatic plugging is implemented by biasing the electrically isolated magnetic multicusp channel walls. The experimental results show that voltage applied to the channel walls can be a controlling parameter for dust charging.
The effect of energetic electrons on dust charging for different types of dust is studied in hydr... more The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
ABSTRACT In this study, the effect of working pressure and input power on the physical properties... more ABSTRACT In this study, the effect of working pressure and input power on the physical properties and sputtering efficiencies of argon–nitrogen (Ar/N2) plasma in direct current magnetron discharge is investigated. The discharge in Ar/N2 is used to deposit TiN films on high speed steel substrate. The physical plasma parameters are determined by using Langmuir probe and optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. A prominent change of electron temperature, electron density, ion density, and degree of ionization of Ar is found as a function of working pressure and input power. The results also show that increasing working pressure exerts a negative effect on film deposition rate while increasing input power has a positive impact on the same. To confirm the observed physical properties and evaluate the texture growth as a function of deposition parameters, x-ray diffraction study of deposited TiN films is also done.
Reports of potential applications of Cold Plasma (CP) in agriculture have increased significantly... more Reports of potential applications of Cold Plasma (CP) in agriculture have increased significantly in recent years. As one fast, economic, and pollution-free method, CP treatment has been found to promote seed germination and plant yield. Cold plasma (CP), non-thermal technology, can be generated by radio frequency or microwave sources. It is well known to us that rice (Oryza sativa L) is a common cereal and the staple food over half the world's population. Different researchers reported that there is a positive impact on seed germination and plant yield of rice. Our objective is to develop an eco-friendly and cost efficient technology based on CP technique to improve the seed germination and plant yield of rice. Numerous works has been carried out to develop some statistical models, in which historical data on crop yields and weather are used to calibrate relatively simple regression equations. Three main types of statistical approaches are found in the literature: time series methods, panel methods and cross-section methods. We are planning to develop a statistical model which is basically based on the multi linear regression model to study the crop yield specially for rice. In the present work, a detail review on different experimental works on CP technique for improvement of seed germination and plant yield of rice as well as different statistical models will be described.
Abstract The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic fie... more Abstract The accuracy of plasma parameters measured by Langmuir probe in presence of magnetic field is studied in our present work. It is observed that the ratio of electron to ion saturation current shows almost identical behavior with that of unmagnetized hydrogen plasma when rL > 10rp (here rL: Larmor radius and rp: probe radius). At magnetic field strength, B = 594 gauss, the electron temperature (Te) shows an overestimated value up to ~35–40%, whereas at B ≤ 37 gauss, Te shows around ≤10% overestimated value w.r.t. unmagnetized case. A bi-Maxwellian electron energy probability function is observed for entire magnetic field range for both pristine and dust containing hydrogen plasma. The bulk (cold) electron collection by the Langmuir probe is strongly suppressed whereas the higher energetic electron collection remains unaffected in presence of magnetic field. In presence of dust grains, it is found that the low energy electron population decreases even more than the magnetized plasma and the high-energy tail slightly increases compared to the pristine plasma. Graphical abstract
Проанализированы данные о вкладе метеорологических и синоптических условий в возникновение лесных... more Проанализированы данные о вкладе метеорологических и синоптических условий в возникновение лесных пожаров в Иркутской области. По результатам наблюдений метеорологических станций, расположенных в разных физико-географических районах Иркутской области, рассчитан показатель пожарной опасности по В.Г. Нестерову в периоды апрель-сентябрь 2010-2015 гг. Этот показатель характеризует метеорологические условия исследуемой территории как усредненные по степени пожарной опасности. Выявлено, что наиболее благоприятные условия для возникновения лесных пожаров по времени наблюдаются в мае-июне и августесентябре, а в пространственном отношении-на севере Иркутской области и на побережье оз. Байкал, где отмечается наименьшее количество атмосферных осадков. Синоптический анализ летнего периода 2015 г. с большим числом лесных пожаров на Байкальской природной территории показал господствующее влияние блокирующих процессов, которые сопровождались редким выходом южных циклонов-основных поставщиков влаги в регион. В качестве предикторов лесных пожаров в Иркутской области наиболее высокую оправдываемость (≥70%) в теплый период 2015 г. имели значения температуры воздуха: у поверхности Земли, в нижней (АТ-850 гПа) и средней (АТ-500 гПа) тропосфере, потенциальной температуры на уровне АТ-850 гПа; аномалии геопотенциала АТ-500 гПа, относительной влажности воздуха и сумм атмосферных осадков.
Kognitive Beeinträchtigung und Depressivität im Alter 2 Zusammenfassung Kognitive Beeinträchtigun... more Kognitive Beeinträchtigung und Depressivität im Alter 2 Zusammenfassung Kognitive Beeinträchtigungen im Alter bedeuten nicht selten eine hohe psychische Belastung und können zu psychoreaktiven Verstimmungen führen. Wir untersuchen, inwieweit die belastenden Effekte kognitiver Verluste durch Bildungsressourcen abgemildert und ausgeglichen werden. An der Studie nahmen 201 ältere Personen teil, die das Diagnose-und Beratungsangebot des Gedächtniszentrums des Instituts für Psychogerontologie nutzten. Untersucht wurden die Zusammenhänge zwischen berichteten Beschwerden, kognitiver Leistung und Depressivität in drei Gruppen von dementen Patienten (n = 77), leicht kognitiv beeinträchtigten Patienten (MCI, n = 78) sowie nur subjektiv beeinträchtigten, gesunden Personen (n = 46). Die Ergebnisse zeigen, dass unabhängig von Gesundheit, Familienstand, und Demenzdiagnose die Zusammenhänge zwischen berichteten Beschwerden und Depressivität in Abhängigkeit von Bildungseinflüssen variieren. Zwar gingen berichtete Beschwerden generell mit erhöhtem Depressivitätserleben einher, dieser Zusammenhang war aber bei höher gebildeten Personen geringer. Bildungsressourcen können somit belastende Effekte subjektiver Leistungseinbußen auf die Befindlichkeit kompensieren.
SST-1 Tokamak has recently completed the 1st phase of up-gradation with successful installation a... more SST-1 Tokamak has recently completed the 1st phase of up-gradation with successful installation and integration of all its First Wall components. The First Wall of SST-1 comprises of ~ 3800 high heat flux compatible graphite tiles being assembled and installed on 132 CuCrZr heat sink back plates engraved with ~ 4 km of leak tight baking and cooling channels in five major sub groups equipped with ~ 400 sensors and weighing ~ 6000 kg in total in thirteen isolated galvanic and six isolated hydraulic circuits. The phase-1 upgradation spectrum also includes addition of Supersonic Molecular Beam Injection (SMBI) both on the in-board and out-board side, installation of fast reciprocating probes, adding some edge plasma probe diagnostics in the SOL region, installation and integration of segmented and up-down symmetric radial coils aiding/controlling plasma rotations, introduction of plasma position feedback and density controls etc. Post phase-I up-gradation spanning from Nov 2014 till June 2016, initial plasma experiments in up-graded SST-1 have begun since Aug 2016 after a brief engineering validation period in SST-1. The first experiments in SST-1 have revealed interesting aspects on the `eddy currents in the First Wall support structures influencing the `magnetic Null evolution dynamics’ and the subsequent plasma start-up characteristics after the ECH pre-ionization, the influence of the first walls on the `field errors’ and the resulting locked modes observed, the magnetic index influencing the evolution of the equilibrium of the plasma column, low density supra-thermal electron induced discharges and normal ohmic discharges etc. Presently; repeatable ohmic discharges regimes in SST-1 having plasma currents in excess of 65 KA (qa ~ 3.8, BT = 1.5 T) with a current ramp rates ~ 1.2 MA/s over a duration of ~ 300 ms with line averaged densities ~ 0.8 × 1019 and temperatures ~ 200 eV with copious MHD signatures have been experimentally established. Further elongation of the plasma duration up to one second or more with position and density feedback as well as coupling of Lower Hybrid waves are currently being persuaded in SST-1 apart from increasing the core plasma parameters with further optimizations and with wall conditioning.
Impurity control reduces the radiation loss from plasma and hence enhances the plasma operation. ... more Impurity control reduces the radiation loss from plasma and hence enhances the plasma operation. Oxygen and water vapors are the most common impurities in tokamak devices. Water vapour can be reduced with extensive baking while in order to have a significant reduction in oxygen it is necessary to use glow discharge condition (GDC). RF assisted glow discharge cleaning system will be implemented to remove low z impurities at PFC installed SST-1 vacuum vessel. A RF assisted Glow discharge conditioning is studied at laboratory to find the optimum operating parameters in a view to implement at SST-1 tokamak. Helium is used as a fuel gas in the present experiment. It is observed that the ultimate impurity level is reduced significantly below to the accepted level for plasma operation after RF assisted GDC. The experimental findings of RF assisted Glow discharge conditioning is discussed in details in this paper.
Knowledge of the real EEDF is of great importance in understanding the underlying physics of proc... more Knowledge of the real EEDF is of great importance in understanding the underlying physics of processes occurring at the magnetized plasma, such as the formation of transport barriers, cross-field diffusion coefficients and plasma–substrate interactions. In the present experiment, the application of Langmuir probe to evaluate EEPF in presence of magnetic fields within the range 594 –32 G is investigated. The data recorded for EEPFs in magnetic fields and in dust is acquired using current–voltage characteristics measured in low pressure hydrogen plasma. The values of plasma density, electron temperature and EEPF are evaluated with a single cylindrical Langmuir probe at different axial positions (1 cm to 6 cm) from the magnet. From the recent EEPF observations in presence of magnetic field, it shows a bi-Maxwellian EEPF structure at different magnetic fields. But at different magnetic field, it is observed that the low energy electron population changes whereas the high-energy electron population remains almost constant. EEPF measurement shows almost identical behaviour with the unmagnetized plasma when the larmour radius of electron is greater than or equal to 10 times of the probe radius.
The effect of external magnetic field on the Langmuir probe measurement and dust charging are stu... more The effect of external magnetic field on the Langmuir probe measurement and dust charging are studied in low-pressure hydrogen plasma. The experiment is performed in a dusty plasma device where plasma is created by the hot cathode filament discharge technique. A strong Strontium ferrite magnet is used inside the plasma, near the dust zone. The plasma parameters are measured at different distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where reL rP, riL iirP; the electron collection by the probe deviates strongly from the actual value, until reL 10rP. The observations of electron energy probability function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.
Some parametric studies like the effect of discharge current, plasma temperature and working pres... more Some parametric studies like the effect of discharge current, plasma temperature and working pressure on the charging of dust grains in hot cathode discharge plasma will be presented. The designing concepts of a novel experiment to produce negative hydrogen ions from Cesium coated dust particles and related preliminary studies with dust particles in hydrogen plasma will be presented. The aim of producing negative hydrogen ions is to devise the possibility of using such negative ions in Neutral Beam Injection Heating of Tokamak plasma. Refs: S.S. Kausik, M.Chakraborty, P. Dutta, M. Kakati and B.K. Saikia, Phys. Lett. A 372, 860 (2008)
Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasm... more Experimental results on effect of adding argon gas to hydrogen plasma in a multi-cusp dusty plasma device are reported. Addition of argon modifies plasma density, electron temperature, degree of hydrogen dissociation, dust current as well as dust charge. From the dust charging profile, it is observed that the dust current and dust charge decrease significantly up to 40% addition of argon flow rate in hydrogen plasma. But beyond 40% of argon flow rate, the changes in dust current and dust charge are insignificant. Results show that the addition of argon to hydrogen plasma in a dusty plasma device can be used as a tool to control the dust charging in a low pressure dusty plasma. (C) 2014 AIP Publishing LLC.
ABSTRACT The effect of electrostatic confinement on charging of dust grains has been studied in a... more ABSTRACT The effect of electrostatic confinement on charging of dust grains has been studied in a dusty plasma experimental setup by applying electrostatic field to each channel of a multicusp magnetic cage. The number of charges collected by dust grains is calculated both from the amount of deflection and floating potential. The experimental results demonstrate the significant effect of confining wall potential on charging of dust grains.
Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungst... more Hydrogen plasma is produced in a plasma chamber by striking discharge between incandescent tungsten filaments and the permanent magnetic cage (1), which is grounded. The magnetic cage has a full line cusped magnetic field geometry used to confine the plasma elements. A cylindrical Langmuir probe is used to study the plasma parameters in various discharge conditions. The charge accumulated on
ABSTRACT In this study, the effect of magnetron target on different plasma parameters of Argon/Hy... more ABSTRACT In this study, the effect of magnetron target on different plasma parameters of Argon/Hydrogen (Ar - H2) direct current (DC) magnetron discharge is examined. Here, Copper (Cu) and Chromium (Cr) are used as magnetron targets. The value of plasma parameters such as electron temperature (kTe), electron density (Ne), ion density (Ni), degree of ionization of Ar, and degree of dissociation of H2 for both the target are studied as a function of input power and hydrogen content in the discharge. The plasma parameters are determined by using Langmuir probe and Optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. The obtained results show that electron and ion density decline with gradual addition of Hydrogen in the discharge and increase with rising input power. It brings significant changes on the degree of ionization of Ar and dissociation of H2. The enhanced value of electron density (Ne), ion density (Ni), degree of Ionization of Ar, and degree of dissociation of H2 for Cr compared to Cu target is explained on the basis of it's higher Ion Induced Secondary Electron Emission Coefficient (ISEE) value.
The effect of the electrostatic confinement potential on the charging of dust grains and its rela... more The effect of the electrostatic confinement potential on the charging of dust grains and its relationship with the plasma parameters has been studied in an electrostatically plugged multicusp dusty plasma device. Electrostatic plugging is implemented by biasing the electrically isolated magnetic multicusp channel walls. The experimental results show that voltage applied to the channel walls can be a controlling parameter for dust charging.
The effect of energetic electrons on dust charging for different types of dust is studied in hydr... more The effect of energetic electrons on dust charging for different types of dust is studied in hydrogen plasma. The hydrogen plasma is produced by hot cathode filament discharge method in a dusty plasma device. A full line cusped magnetic field cage is used to confine the plasma elements. To study the plasma parameters for various discharge conditions, a cylindrical Langmuir probe having 0.15 mm diameter and 10.0 mm length is used. An electronically controlled dust dropper is used to drop the dust particles into the plasma. For different discharge conditions, the dust current is measured using a Faraday cup connected to an electrometer. The effect of secondary emission as well as discharge voltage on charging of dust grains in hydrogen plasma is studied with different dust.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, 2013
ABSTRACT In this study, the effect of working pressure and input power on the physical properties... more ABSTRACT In this study, the effect of working pressure and input power on the physical properties and sputtering efficiencies of argon–nitrogen (Ar/N2) plasma in direct current magnetron discharge is investigated. The discharge in Ar/N2 is used to deposit TiN films on high speed steel substrate. The physical plasma parameters are determined by using Langmuir probe and optical emission spectroscopy. On the basis of the different reactions in the gas phase, the variation of plasma parameters and sputtering rate are explained. A prominent change of electron temperature, electron density, ion density, and degree of ionization of Ar is found as a function of working pressure and input power. The results also show that increasing working pressure exerts a negative effect on film deposition rate while increasing input power has a positive impact on the same. To confirm the observed physical properties and evaluate the texture growth as a function of deposition parameters, x-ray diffraction study of deposited TiN films is also done.
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Papers by Bharat Kakati
cooling channels in five major sub groups equipped with ~ 400 sensors and weighing ~ 6000 kg in total in thirteen isolated galvanic and six isolated hydraulic circuits. The phase-1 upgradation spectrum also includes addition of Supersonic Molecular Beam Injection (SMBI)
both on the in-board and out-board side, installation of fast reciprocating probes, adding some edge plasma probe diagnostics in the SOL region, installation and integration of segmented and up-down symmetric radial coils aiding/controlling plasma rotations, introduction of plasma position feedback and density controls etc. Post phase-I up-gradation spanning from Nov 2014 till June 2016, initial plasma experiments in up-graded SST-1 have begun since Aug 2016 after a brief engineering validation period in SST-1. The first experiments in SST-1 have
revealed interesting aspects on the `eddy currents in the First Wall support structures influencing the `magnetic Null evolution dynamics’ and the subsequent plasma start-up characteristics after the ECH pre-ionization, the influence of the first walls on the `field errors’ and the resulting locked modes observed, the magnetic index influencing the evolution of the equilibrium of the plasma column, low density supra-thermal electron induced discharges and normal ohmic discharges etc. Presently; repeatable ohmic discharges regimes in SST-1 having
plasma currents in excess of 65 KA (qa ~ 3.8, BT = 1.5 T) with a current ramp rates ~ 1.2 MA/s over a duration of ~ 300 ms with line averaged densities ~ 0.8 × 1019 and temperatures ~ 200 eV with copious MHD signatures have been experimentally established. Further elongation of the plasma duration up to one second or more with position and density feedback as well as coupling of Lower Hybrid waves are currently being persuaded in SST-1 apart from increasing the core plasma parameters with further optimizations and with wall conditioning.
experiment, the application of Langmuir probe to evaluate EEPF in presence of magnetic fields within the range 594 –32 G is investigated. The data recorded for EEPFs in magnetic fields and
in dust is acquired using current–voltage characteristics measured in low pressure hydrogen plasma. The values of plasma density, electron temperature and EEPF are evaluated with a single cylindrical Langmuir probe at different axial positions (1 cm to 6 cm) from the magnet.
From the recent EEPF observations in presence of magnetic field, it shows a bi-Maxwellian EEPF structure at different magnetic fields. But at different magnetic field, it is observed that the low energy electron population changes whereas the high-energy electron population
remains almost constant. EEPF measurement shows almost identical behaviour with the unmagnetized plasma when the larmour radius of electron is greater than or equal to 10 times of the probe radius.
distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where reL rP, riL iirP; the electron collection by the probe deviates strongly from the actual value, until reL 10rP. The observations of electron energy probability
function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.
cooling channels in five major sub groups equipped with ~ 400 sensors and weighing ~ 6000 kg in total in thirteen isolated galvanic and six isolated hydraulic circuits. The phase-1 upgradation spectrum also includes addition of Supersonic Molecular Beam Injection (SMBI)
both on the in-board and out-board side, installation of fast reciprocating probes, adding some edge plasma probe diagnostics in the SOL region, installation and integration of segmented and up-down symmetric radial coils aiding/controlling plasma rotations, introduction of plasma position feedback and density controls etc. Post phase-I up-gradation spanning from Nov 2014 till June 2016, initial plasma experiments in up-graded SST-1 have begun since Aug 2016 after a brief engineering validation period in SST-1. The first experiments in SST-1 have
revealed interesting aspects on the `eddy currents in the First Wall support structures influencing the `magnetic Null evolution dynamics’ and the subsequent plasma start-up characteristics after the ECH pre-ionization, the influence of the first walls on the `field errors’ and the resulting locked modes observed, the magnetic index influencing the evolution of the equilibrium of the plasma column, low density supra-thermal electron induced discharges and normal ohmic discharges etc. Presently; repeatable ohmic discharges regimes in SST-1 having
plasma currents in excess of 65 KA (qa ~ 3.8, BT = 1.5 T) with a current ramp rates ~ 1.2 MA/s over a duration of ~ 300 ms with line averaged densities ~ 0.8 × 1019 and temperatures ~ 200 eV with copious MHD signatures have been experimentally established. Further elongation of the plasma duration up to one second or more with position and density feedback as well as coupling of Lower Hybrid waves are currently being persuaded in SST-1 apart from increasing the core plasma parameters with further optimizations and with wall conditioning.
experiment, the application of Langmuir probe to evaluate EEPF in presence of magnetic fields within the range 594 –32 G is investigated. The data recorded for EEPFs in magnetic fields and
in dust is acquired using current–voltage characteristics measured in low pressure hydrogen plasma. The values of plasma density, electron temperature and EEPF are evaluated with a single cylindrical Langmuir probe at different axial positions (1 cm to 6 cm) from the magnet.
From the recent EEPF observations in presence of magnetic field, it shows a bi-Maxwellian EEPF structure at different magnetic fields. But at different magnetic field, it is observed that the low energy electron population changes whereas the high-energy electron population
remains almost constant. EEPF measurement shows almost identical behaviour with the unmagnetized plasma when the larmour radius of electron is greater than or equal to 10 times of the probe radius.
distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where reL rP, riL iirP; the electron collection by the probe deviates strongly from the actual value, until reL 10rP. The observations of electron energy probability
function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.