冷端温度对无极灯253.7nm共振谱线的影响

无极灯是一种长寿命、低汞害、无频闪的新型电光源,其光效在很大程度上取决于253.7nm共振谱线的辐射效率。通过原子发射光谱分析,实验研究了冷端温度对253.7nm共振谱线的影响规律。研究发现,253.7nm共振谱线的辐射效率随冷端温度变化近似呈正态分布,即无极灯工作存在一个最佳冷端温度。运用气体放电理论对实验结果进行了定性分析,对无极灯光效的提高具有指导意义。     

Efficient light source based on an inductive ferrite-free discharge at frequencies of 300–3000 kHz

Glass cylindrical tubes from 30 to 50 cm long and from 5 to 7 cm in diameter are used to initiate an inductive discharge in electrodeless luminescent lamps at frequencies of 300–3000 kHz with a power of 50–300 W. The tubes are filled with mercury vapor and an inert gas (argon at a pressure of 0.1 mm Hg), and their inner surface is covered by a phosphor and protective coating. An induction coil (from 5 to 14 turns) made of a low-resistivity multiple-conductor cable embraces the discharge tube in the longitudinal direction, forming a discharge-initiating loop. Because of a high Q factor of the coil, Q _c = 400, the power losses in it are 4–5 W at frequencies higher than 400 kHz; the energy efficiency of the lamp is η = 0.95–0.96. Luminous efficiency ? of the lamp grows with discharge excitation frequency, reaching ? = 83–84 lm/W at a frequency of 530 kHz and a power of 150 W.     

Use of a Twin-Port Power Divider and Attenuator in the Operation of Electrodeless Discharge Lamps for Multi-Element Atomic Fluorescence Spectrometry

The range of the two techniques of multi-element atomic fluorescence spectrometry may be extended by the use of a twinport power divider to allow two multi-element electrodeless discharge lamps to be operated from a single microwave generator. Various combinations of 1/4-wave, 3/4-wave resonant cavities and an A-antenna in conjunction with a coaxial attenuator allow lamps of differing excitation requirements to be operated simultaneously.     

Radiative characteristics of high-frequency electrodeless helium lamps

Based on the system of equations describing the populations of highly excited helium atomic levels and the electron density and energy balance and on the Maxwell equations, we develop a model for an electrodeless high-frequency discharge in helium. We suggest a method of self-consistent calculation in a plasma-field system. The model developed is used to calculate the radiative characteristics of high-frequency electrodeless lamps. The derived dependences of line intensities on gas pressure, lamp radius, and discharge power are in good agreement with the experimental data.     

Determination of gas temperature of high-frequency low-temperature electrodeless plasma using molecular spectra of hydrogen and hydroxyl-radical

In this study we determine gas temperature of He+H₂, Ar+H₂ and Ne+H₂ high frequency electrodeless lamps using intensity distribution in rotational spectra of hydrogen molecule and hydroxyl radical. The measurement results show that OH rotational spectra can be successfully used for estimation of gas temperature of the high-frequency electrodeless lamps at very small amounts of hydrogen present in plasma. The analysis of the measurement results leads to the conclusion that in “pure” plasma the applied energy is used to heat plasma, while for the plasma with hydrogen addition the energy is used in chemical reactions.     

Spatial distribution of radiation intensity in high-frequency electrodeless discharge lamps

The spatial distribution of the intensity of radiation from high-frequency electrodeless discharge lamps of LV-2 and VSB-2 types, used as radiation sources in atomic absorption spectrometry, was investigated. Radiation intensity distributions over the cross section of the lamps were measured on the atomic and ionic lines of a buffer gas and a filler element. It is shown that in a lamp filled with buffer gas only the distribution of the intensity of atomic and ionic lines is dome-shaped, and that it is determined by the electron density distribution in the plasma as well as by the mechanism of excitation and ionization of the buffer gas. The distribution of the intensity of radiation from the filler element is strongly nonuniform, with a maximum that is concentric with the bulb walls and a minimum on the lamp axis. The observed spatial intensity distributions are explained by the redistribution of filler-element atoms over the volume of the lamp under the conditions of high electron concentrations. The time dynamics of the spatial intensity distributions during warm-up of the lamps was investigated. It is shown that the process of establishment of stationary distributions goes on nonmonotonically, which is due to the redistribution of energy among different components of the discharge plasma. Translated from Zhurnal Prikladnoi Spektroskopi, Vol. 67, No. 1, pp. 15–20, January–February, 2000.     

Pulsed alkali pump light sources for Nd:YAG lasers

Pulsed arc discharges in alkali metal vapours are investigated for use as pump light sources for Nd:YAG lasers. Alkali lamps have a very high radiation efficiency and emit strong lines near the laser pump bands. These absorption bands are fitted by the emission spectrum of sodium and potassium lamps by changing the vapour pressure and input power. The spectral radiation distributions of the lamps are measured by a spectrograph with a gated OMA system. Ray tracing calculations for a laser cavity are used to evaluate the efficiency of the alkali radiation emission for Nd:YAG pumping. The results show that the excitation efficiency of the alkali lamps is twice as high as that of usually used rare gas lamps. For sodium resonance lines the side-on spectral radiance is calculated by a radiation transport model to estimate the pressure and the temperature profile. The results indicate that the alkali vapour lamps could be used as pump light sources with high efficiencies and low heat loading of the laser cavity.     

Longitudinal rf discharge in Xe/Cl<Subscript>2</Subscript> mixtures

Results are presented from the studies of the electrical and emission characteristics of the low-temperature plasma of a longitudinal rf (f₀=1.76 MHz) discharge in Xe/Cl₂ mixtures at pressures of 100–800 Pa. The discharge was ignited in a cylindrical quartz tube with an inner diameter of 1.4 cm and interelectrode distance of 3.0 cm. The discharge emission within the spectral range of 190–670 nm is studied. The dynamics of the discharge current and discharge emission at different pressures and compositions of a Xe/Cl₂ mixture are investigated. It is shown that a discharge in a Xe/Cl₂ mixture acts as a wideband excimer-halogen lamp with a cylindrical output aperture emitting in the spectral range of 220–320 nm. The broad plasma emission spectrum is formed due to the overlap of the XeCl(D, B-X; B, C-A) bands that are broadened at low working-gas pressures. The composition of the working mixture is optimized to achieve the maximum power of the wideband UV plasma emission. Longitudinal rf discharges in low-pressure Xe/Cl₂ mixtures are of interest for developing small-size wideband (Δλ=220–450 nm) cylindrical-aperture lamps, whose efficiency can, on average, exceed the efficiency of conventional hydrogen lamps by more than one order of magnitude.     

平板型感应耦合等离子体源的线圈配置对功率耦合效率的影响

基于感应耦合等离子体的变压器模型，分析了感应耦合等离子体的功率耦合效率与线圈配置(几何尺寸、电学参量)及等离子体基本参量(等离子体电子密度、电子-中性粒子有效碰撞频率)之间的关系；然后，改变平板型线圈的匝数从而改变了线圈的几何尺寸、电学参量，并且测量出了不同的线圈所对应的功率耦合效率.实验结果表明，线圈的电感量是能否实现放电的决定性因素；而功率耦合效率则与感应线圈的Q值、放电参量(气压、功率)等密切相关，射频输入功率的增加、放电气压的上升都会导致感应耦合等离子体耦合效率的提高，这与感应耦合等离子体的变压器模型预测结果是符合的. 然而，变压器模型给出的提高线圈Q值可导致耦合效率增强的预测结果仅适用于同等电感量的线圈条件. 本文对于单线圈的感应耦合等离子体源的研究为线圈的优化设计甚至大面积的多线圈感应耦合等离子体源研制提供了理论依据. 关键词： 感应耦合等离子体 功率耦合效率 变压器模型     

Nonequilibrium lighting plasmas

The science of a variety of devices employing nonequilibrium lightning plasmas is reviewed. The devices include the fluorescent lamp, the low-pressure sodium lamp, the neon sign, ultraviolet lamps, glow indicators, and a variety of devices used by spectroscopists, such as the hollow cathode light source. The plasma conditions in representative commercial devices are described. Recent research on the electron gas, the role of heavy particles, spatial and temporal inhomogeneities, and new electrodeless excitation schemes is reviewed. Areas of future activity are expected to be in new applications of high-frequency electronics to commercial devices, new laser-based cidiagnostics of plasma conditions, and more sophisticated models requiring more reliable and extensive rate coefficient data     

Plasma cleaning of multilayer mirrors in EUV lithography from amorphous carbon contaminations

The feasibility of plasma cleaning of the multilayer mirrors used in 13.5-nm EUV lithography from carbon contaminations is studied. Experiments conducted in electrodeless plasma of the surface-wave low-pressure discharge in helium and hydrogen demonstrated the high rate, efficiency, and selectivity of this cleaning without any damage of the mirror’s upper protection layer, even at the atomic level. The optimal working parameters of plasma cleaning are determined and its possible mechanism is discussed.     

Electrodeless-discharge-vapor-lamp-based Faraday anomalous-dispersion optical filter

We report an excited-state Faraday anomalous-dispersion optical filter operating on the rubidium 5P(3/2)-5D(5/2) transition (775.9 nm in vacuum) without the use of a pump laser. An electrodeless discharge vapor lamp is employed to replace the Rb vapor cell in a traditional Faraday anomalous-dispersion optical filter system. Atoms can be excited by power rather than a complex frequency-locked pump laser. A proof-of-concept experimental demonstration with a maximum transmission of 1.9% and a filter bandwidth of 650 MHz is presented.     

High-energy dye laser pumped by wall-ablation lamps

A guideline for the optimum design of linear wall-ablation lamps is presented with a simple empirical formula which describes the luminescent characteristics of lamps. The absolute luminescent efficiency of the wall-ablation lamp was measured. A high-energy dye laser with a quadruple-elliptical cylindrical cavity was constructed using these lamps, and an output energy of 23.3 J (11.6 MW) was obtained with an overall efficiency of 0.31 %. The energy-flow diagram of this laser system was computed with a rate-equation analysis, and the conversion efficiency from electrical input to laser output was determined. One can expect an overall efficiency of about 2 %.     

Extreme-ultraviolet source based on the electron-cyclotron-resonance discharge

An extreme-ultraviolet (EUV) source based on a low-pressure discharge sustained in a magnetic trap by the high-power millimeter-wave radiation under electron-cyclotron-resonance (ECR) conditions is discussed. Multiply charged ions are efficiently generated and excited in such a discharge (tin ions injected into the trap from a vacuum-arc discharge were used) and emit line radiation in the desired wavelength range. A radiation power of 50 W in a wavelength range of 13.5 nm ± 1% and an efficiency of about 1% for the conversion of the micro-wave radiation absorbed in the plasma to the extreme ultraviolet radiation were achieved in the preliminary experiments.     

Ionization-overheating instability threshold in the electrodeless microwave discharge plasma

Experiments with a pulsed freely localized electrodeless microwave discharge in air under a pressure corresponding to the ascending branch of the pressure dependence of the breakdown field are described. The discharge is initiated in a focused quasi-optical electromagnetic beam. The minimal threshold values of the electromagnetic field (for which a brighter plasma channel extended along the field is formed in the initially spatially homogeneous diffuse discharge plasma) are determined by varying air pressure for several fixed values of this field in the focal region of the beam. In accordance with the prevailing theory, this phenomenon is interpreted as the result of evolution of ionization-overheating instability in the microwave discharge plasma.     

分段表面放电沉积效率研究

 利用一种结构紧凑的分段表面放电辐射源模块，详细研究了在不同电压、电容、气压实验条件下回路等效电阻、等效电感及放电能量沉积效率的变化规律，利用四分幅相机拍摄获得了不同实验条件下的放电等离子体通道图像，分析讨论了放电等离子体运动对放电能量沉积效率的影响，提出了提高能量放电沉积效率的有效途径。     

高功率氙灯脉冲放电过程中石英管壁热损伤机理

基于高功率激光装置对脉冲氙灯工程运行可靠性的要求,利用现有的能源模块开展了氙灯放电考核实验。实验结果表明:虽然氙灯运行在安全的能量负载水平,当能源模块单个放电回路的峰值功率超过300MW时,氙灯石英玻璃管壁存在热损伤风险。肉眼观察到管壁损伤后在反射器对侧的灯管内壁出现乳白色沉积层。经扫描电镜和X射线光电子能谱测试分析,证实热损伤形成的乳白色沉积物为二氧化硅。为探究管壁热损伤机制,采用高速摄影观测了氙灯放电等离子体沟道发展过程。图像显示放大器内金属反射器的几何形状对放电沟道的分布产生了显著影响,尤其是在侧灯箱,灯内电弧沟道会靠近反射器一侧集中分布,因此,导致等离子体对灯管的偏烧。当放电峰值功率超过石英热负载极限时,管壁表面二氧化硅材料会被烧蚀至蒸发、气化,并随后沉积在灯管较冷部位。研究结果表明放电回路的放电峰值功率过高、放大器内金属反射器均会对氙灯造成热损伤。     

Comparison of Detection Limits in Atomic Fluorescence and Absorption Spectroscopy

Dagnall, Taylor, and West have recently compared detection limits for a number of metals in atomic fluorescence and absorption spectroscopy and have concluded that “atomic fluorescence measurements using an electrodeless discharge tube are inherently more sensitive than those obtainable by atomic absorption measurements”. Likewise West and Williams have compared the two techniques for magnesium²and silver³, using high-intensity hollow-cathode lamps as sources, and have found much lower detection limits in fluorescence than in absorption.     

铟网位置对无极灯253.7 nm共振谱线的影响

无极灯是一种基于高频电磁感应和无极气体放电的新型电光源,由Hg 253.7 nm共振谱线激发荧光粉进而发出可见光。通过原子发射光谱分析,实验研究了铟网位置对Hg 253.7 nm共振谱线的影响规律。研究发现,Hg 253.7 nm共振谱线的相对强度,当铟网位于耦合线圈两端时最强,位于耦合线圈中部时较弱,远离耦合线圈时最弱。并推断,存在一个最佳的铟网位置,对应最高的发光效率。结合Maxwell 3D有限元仿真,从气体放电角度对实验结果进行了定性分析,对无极灯模型设计与参数优化具有指导意义。     

Carbon monoxide emission in VUV spectral region upon excitation of natural gas by a capacitive discharge

Upon excitation of natural gas by a capacitive electrodeless discharge, an intense excitation of the (4⁺) band system of CO in the region of 150-200 nm was observed. Excited CO molecules are accumulated as a result of plasmochemical reactions in the gas-discharge plasma. At a pressure of 15 Torr, a pulse repletion frequency of 100 kHz, and a specific excitation power of ~300 mW/cm³, the power density of radiation of the (4⁺) band system of CO from the external surface of a radiator was ~5 mW/cm² at an efficiency of up to ~2%.