MODELING OF THE ION AND FAST ATOM ENERGY SPECTRA IN AN ARGON TOWNSEND DISCHARGE

Simulation of argon ion motion in the low-current discharge is fulfilled by the Monte Carlo method, taking into account the charge exchange and elastic scattering on argon atoms. The energy spectra of ions and fast neutrals generated under ion elastic scattering are calculated and their contributions to the cathode sputtering are found.96-9

Моделирование влияния тонкой диэлектрической пленки на поверхности электрода на зажигание разряда в ртутных осветительных лампах при низких температурах окружающей среды

The mixture of argon and mercury vapor with temperature-dependent composition is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was to develop a model of the low-current discharge in an argon-mercury mixture at presence of a thin insulating film on the cathode and to investigate the influence of film on the discharge ignition voltage at low ambient temperatures. When discharge modeling, we used the obtained earlier expression which describes dependence of the mixture ionization coefficient on temperature. When there was a thin insulating film on the cathode the model took into account that positive charges are accumulated on its surface during the discharge. They generate an electric field in the film sufficient for the field emission of electrons from the metal substrate of the electrode into the insulator and some of them can overcome the potential barrier at the film outer boundary and go out in the discharge volume improving emission characteristics of the cathode.Calculations showed that at a temperature decrease the electric field strengthes in the discharge gap and the voltage in it are increased due to reduction of the saturated mercury vapor density in the mixture followed by the decrease of its ionization coefficient. Existence of a thin insulating film on the cathode surface results in an increase of the cathode effective secondary electron emission yield which compensates the reduction of the mixture ionization coefficient value.The results of discharge characteristics modeling demonstrate that in case of the cathode with an insulating film the discharge ignition becomes possible at a lower inter-electrode voltage. This ensures outdoor mercury lamp turning on at a reduced supply voltage and increases its reliability under low ambient temperatures.Смесь аргона и паров ртути с зависящим от температуры составом используется в качестве рабочего газа в различных типах газоразрядных осветительных ламп. Целью данной работы являлось построение модели слаботочного разряда в смеси аргон-ртуть при наличии на катоде тонкой диэлектрической пленки, а также определение ее влияния на напряжение зажигания разряда при низкой температуре окружающей среды.При моделировании разряда мы использовали полученное ранее выражение, описывающее зависимость ионизационного коэффициента рассматриваемой смеси от температуры. В случае наличия на катоде тонкой диэлектрической пленки в модели учитывали, что в разряде на ее поверхности накапливаются положительные заряды. Они создают в пленке электрическое поле, достаточное для возникновения полевой эмиссии электронов из металлической подложки электрода в диэлектрик, часть из которых может преодолевать потенциальный барьер на внешней границе пленки и выходить в разрядный объем, улучшая эмиссионные характеристики катода.Расчеты показали, что при снижении температуры происходит увеличение напряженности электрического поля в разрядном промежутке и напряжения на нем, обусловленное уменьшением концентрации насыщенных паров ртути в смеси, а следовательно, и ее ионизационного коэффициента. Наличие же тонкой диэлектрической пленки на поверхности катода может приводить, вследствие существования полевой эмиссии электронов в пленку, к увеличению эффективного коэффициента электронной эмиссии катода, компенсирующему снижение величины ионизационного коэффициента.Представленные результаты моделирования характеристик разряда демонстрируют, что в случае катода с диэлектрической пленкой становится возможным возникновение разряда при более низком межэлектродном напряжении. Это обеспечивает зажигание лампы наружного освещения при меньшем напряжении питающей сети и повышает ее надежность в условиях низких температур

Моделирование распыления поверхности катода ионами и быстрыми атомами в таунсендовском разряде в смеси аргон-ртуть с зависящим от температуры составом

The mixture of argon and mercury vapor is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was development of a model, describing transport of electrons, ions and fast atoms in the one-dimensional low-current gas discharge in argon-mercury mixture, and determination of the dependence of their contributions to the cathode sputtering, limiting the device service time, on the temperature.For simulation of motion of electrons we used the Monte Carlo method of statistical modeling, whereas the ion and metastable excited atom motion, in order to reduce the calculation time, we described on the basis of their macroscopic transport equations, which allowed to obtain their flow densities at the cathode surface. Then, using the Monte Carlo method, we found the energy spectra of ions and fast atoms, generated in collisions of ions with mixture atoms, at the cathode surface and also the effective coefficients of the cathode sputtering by each type of particles.Calculations showed that the flow densities of argon ions and fast argon atoms, produced in collisions of argon ions with slow argon atoms, do not depend on the temperature, while the flow densities of mercury ions and fast argon atoms generated by them grow rapidly with the temperature due to an increase of mercury content in the mixture.There are represented results of modeling of the energy spectra of ions and fast atoms at the cathode surface. They demonstrate that at low mercury content in the mixture of the order of 10–3 the energies of mercury ions exceed that of the other types of particles, so that the cathode is sputtered mainly by mercury ions, and their contribution to sputtering is reduced at a mixture temperature decrease.Смесь аргона и паров ртути используется в качестве рабочего газа в различных типах газоразрядных осветительных ламп. Целью данной работы являлось построение модели, описывающей перенос электронов, ионов и быстрых атомов в слаботочном разряде в смеси аргон-ртуть, а также определение зависимости их вкладов в распыление катода, ограничивающее срок службы прибора, от температуры. Для моделирования движения электронов мы применяли метод статистического моделирования Монте-Карло. Перенос ионов и возбужденных атомов с целью сокращения затрат расчетного времени описывали на основе макроскопических уравнений, что позволило найти плотности их потоков у поверхности катода. Затем с использованием метода Монте-Карло находили энергетические спектры ионов и быстрых атомов, образующихся при столкновениях ионов с атомами смеси, у поверхности катода, а также эффективные коэффициенты распыления катода каждым типом частиц.Расчеты показали, что плотности потоков ионов аргона и быстрых атомов аргона, возникающих при столкновениях ионов аргона с медленными атомами аргона, не зависят от температуры, в то время как плотности потоков ионов ртути и быстрых атомов аргона, образуемых ими, быстро возрастают при увеличении температуры вследствие увеличения содержания ртути в смеси.Представлены результаты моделирования энергетических спектров ионов и быстрых атомов у поверхности катода. Они демонстрируют, что при малом содержании атомов ртути в смеси порядка 10−3 распыление катода происходит, главным образом, ионами ртути, так как их энергии существенно превосходят энергии других типов частиц, причем их вклад в распыление уменьшается со снижением температуры смеси

MODELING OF THE ION AND FAST ATOM ENERGY SPECTRA IN AN ARGON TOWNSEND DISCHARGE

96-96Simulation of argon ion motion in the low-current discharge is fulfilled by the Monte Carlo method, taking into account the charge exchange and elastic scattering on argon atoms. The energy spectra of ions and fast neutrals generated under ion elastic scattering are calculated and their contributions to the cathode sputtering are found

Моделирование распыления поверхности катода ионами и быстрыми атомами в таунсендовском разряде в смеси аргон-ртуть с зависящим от температуры составом

The mixture of argon and mercury vapor is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was development of a model, describing transport of electrons, ions and fast atoms in the one-dimensional low-current gas discharge in argon-mercury mixture, and determination of the dependence of their contributions to the cathode sputtering, limiting the device service time, on the temperature. For simulation of motion of electrons we used the Monte Carlo method of statistical modeling, whereas the ion and metastable excited atom motion, in order to reduce the calculation time, we described on the basis of their macroscopic transport equations, which allowed to obtain their flow densities at the cathode surface. Then, using the Monte Carlo method, we found the energy spectra of ions and fast atoms, generated in collisions of ions with mixture atoms, at the cathode surface and also the effective coefficients of the cathode sputtering by each type of particles. Calculations showed that the flow densities of argon ions and fast argon atoms, produced in collisions of argon ions with slow argon atoms, do not depend on the temperature, while the flow densities of mercury ions and fast argon atoms generated by them grow rapidly with the temperature due to an increase of mercury content in the mixture. There are represented results of modeling of the energy spectra of ions and fast atoms at the cathode surface. They demonstrate that at low mercury content in the mixture of the order of 10⁻³ the energies of mercury ions exceed that of the other types of particles, so that the cathode is sputtered mainly by mercury ions, and their contribution to sputtering is reduced at a mixture temperature decrease

Моделирование влияния тонкой диэлектрической пленки на поверхности электрода на зажигание разряда в ртутных осветительных лампах при низких температурах окружающей среды

The mixture of argon and mercury vapor with temperature-dependent composition is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was to develop a model of the low-current discharge in an argon-mercury mixture at presence of a thin insulating film on the cathode and to investigate the influence of film on the discharge ignition voltage at low ambient temperatures. When discharge modeling, we used the obtained earlier expression which describes dependence of the mixture ionization coefficient on temperature. When there was a thin insulating film on the cathode the model took into account that positive charges are accumulated on its surface during the discharge. They generate an electric field in the film sufficient for the field emission of electrons from the metal substrate of the electrode into the insulator and some of them can overcome the potential barrier at the film outer boundary and go out in the discharge volume improving emission characteristics of the cathode. Calculations showed that at a temperature decrease the electric field strengthes in the discharge gap and the voltage in it are increased due to reduction of the saturated mercury vapor density in the mixture followed by the decrease of its ionization coefficient. Existence of a thin insulating film on the cathode surface results in an increase of the cathode effective secondary electron emission yield which compensates the reduction of the mixture ionization coefficient value. The results of discharge characteristics modeling demonstrate that in case of the cathode with an insulating film the discharge ignition becomes possible at a lower inter-electrode voltage. This ensures outdoor mercury lamp turning on at a reduced supply voltage and increases its reliability under low ambient temperatures

Simulation of cathode surface sputtering by ions and fast atoms in Townsend discharge in argon-mercury mixture with temperature-dependent composition

The mixture of argon and mercury vapor is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was development of a model, describing transport of electrons, ions and fast atoms in the one-dimensional low-current gas discharge in argon-mercury mixture, and determination of the dependence of their contributions to the cathode sputtering, limiting the device service time, on the temperature.For simulation of motion of electrons we used the Monte Carlo method of statistical modeling, whereas the ion and metastable excited atom motion, in order to reduce the calculation time, we described on the basis of their macroscopic transport equations, which allowed to obtain their flow densities at the cathode surface. Then, using the Monte Carlo method, we found the energy spectra of ions and fast atoms, generated in collisions of ions with mixture atoms, at the cathode surface and also the effective coefficients of the cathode sputtering by each type of particles.Calculations showed that the flow densities of argon ions and fast argon atoms, produced in collisions of argon ions with slow argon atoms, do not depend on the temperature, while the flow densities of mercury ions and fast argon atoms generated by them grow rapidly with the temperature due to an increase of mercury content in the mixture.There are represented results of modeling of the energy spectra of ions and fast atoms at the cathode surface. They demonstrate that at low mercury content in the mixture of the order of 10–3 the energies of mercury ions exceed that of the other types of particles, so that the cathode is sputtered mainly by mercury ions, and their contribution to sputtering is reduced at a mixture temperature decrease

Modeling of an Impact of Thin Insulating Film on the Electrode Surface on Discharge Ignition in Mercury Illuminating Lamps at Low Ambient Temperatures

The mixture of argon and mercury vapor with temperature-dependent composition is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was to develop a model of the low-current discharge in an argon-mercury mixture at presence of a thin insulating film on the cathode and to investigate the influence of film on the discharge ignition voltage at low ambient temperatures. When discharge modeling, we used the obtained earlier expression which describes dependence of the mixture ionization coefficient on temperature. When there was a thin insulating film on the cathode the model took into account that positive charges are accumulated on its surface during the discharge. They generate an electric field in the film sufficient for the field emission of electrons from the metal substrate of the electrode into the insulator and some of them can overcome the potential barrier at the film outer boundary and go out in the discharge volume improving emission characteristics of the cathode.Calculations showed that at a temperature decrease the electric field strengthes in the discharge gap and the voltage in it are increased due to reduction of the saturated mercury vapor density in the mixture followed by the decrease of its ionization coefficient. Existence of a thin insulating film on the cathode surface results in an increase of the cathode effective secondary electron emission yield which compensates the reduction of the mixture ionization coefficient value.The results of discharge characteristics modeling demonstrate that in case of the cathode with an insulating film the discharge ignition becomes possible at a lower inter-electrode voltage. This ensures outdoor mercury lamp turning on at a reduced supply voltage and increases its reliability under low ambient temperatures

Моделирование влияния тонкой диэлектрической пленки на поверхности электрода на зажигание разряда в ртутных осветительных лампах при низких температурах окружающей среды

The mixture of argon and mercury vapor with temperature-dependent composition is used as the background gas in different types of gas discharge illuminating lamps. The aim of this work was to develop a model of the low-current discharge in an argon-mercury mixture at presence of a thin insulating film on the cathode and to investigate the influence of film on the discharge ignition voltage at low ambient temperatures. When discharge modeling, we used the obtained earlier expression which describes dependence of the mixture ionization coefficient on temperature. When there was a thin insulating film on the cathode the model took into account that positive charges are accumulated on its surface during the discharge. They generate an electric field in the film sufficient for the field emission of electrons from the metal substrate of the electrode into the insulator and some of them can overcome the potential barrier at the film outer boundary and go out in the discharge volume improving emission characteristics of the cathode. Calculations showed that at a temperature decrease the electric field strengthes in the discharge gap and the voltage in it are increased due to reduction of the saturated mercury vapor density in the mixture followed by the decrease of its ionization coefficient. Existence of a thin insulating film on the cathode surface results in an increase of the cathode effective secondary electron emission yield which compensates the reduction of the mixture ionization coefficient value. The results of discharge characteristics modeling demonstrate that in case of the cathode with an insulating film the discharge ignition becomes possible at a lower inter-electrode voltage. This ensures outdoor mercury lamp turning on at a reduced supply voltage and increases its reliability under low ambient temperatures