Influence of CO2-laser mixture composition on the distribution of energy in nitrogen spectrum

The DC glow discharge has been studied for mixtures of helium, nitrogen and carbon dioxide - these mixtures are widely used in CO₂ lasers, which are classified as discharge lasers.Analysis of the bands of the nitrogen molecule (the first and the second positive system - B³Π_g → A³Σ_g, C³Π_u → B³Π_g respectively) in an emission spectrum of the glow discharge was used to deduce an energetic balance and a vibrational temperature.The vibrational temperature of dinitrogen was determined by means of optical emission spectroscopy from the second positive system of the nitrogen molecule for various discharge currents and pressures. The dependence of the vibrational temperature on the nitrogen ratio in the mixture was also investigated.A connection between an occurrence of discharge instabilities (often called striations or ionization waves) and the composition of the gas mixture was observed - the less nitrogen was put in the mixture (in favor of helium), the larger part of positive column was subject to standing ionization waves. Ionization waves observed in the positive column of the glow discharge were investigated using optical emission spectroscopy, which showed sinusoidal profile of the vibrational temperature along the axial direction of the ionization waves.     

Cathode layer characteristics of a low-pressure glow discharge in argon and nitrogen

Cathode layer characteristics were experimentally determined for a glow discharge in argon and nitrogen in a broad range of gas pressures. A normal glow discharge regime is observed only provided that the gas ionization takes place in the anode layer (on the right of the inflection point in the glow discharge initiation curve). Importance of using a correct method for the normal cathode voltage drop is emphasized.     

Inexpensive detector for terahertz imaging

Glow discharge plasma, derived from direct-current gas breakdown, is investigated in order to realize an inexpensive terahertz (THz) room-temperature detector. Preliminary results for THz radiation show that glow discharge indicator lamps as room-temperature detectors yield good responsivity and noise-equivalent power. Development of a focal plane array (FPA) using such devices as detectors is advantageous since the cost of a glow discharge detector is approximately $0.2-$0.5 per lamp, and the FPA images will be diffraction limited. The detection mechanism of the glow discharge detector is found to be the enhanced diffusion current, which causes the glow discharge detector bias current to decrease when exposed to THz radiation.     

直流辉光和磁控增强放电等离子体的空间分辨发射光谱技术

光学发射光谱(OES)方法是等离子体诊断的有力工具之一,可以定量地给出等离子体的多种重要参数,如等离子体中的物种成分、粒子能态分布、激发温度、粒子相对密度等.本文介绍了一种用于电子回旋共振(ECR)微波等离子体磁控溅射靶附近的增强放电和直流辉光放电等离子体空间分辨诊断的发射光谱装置.其特点是光学收集系统的位置可以水平精细移动,因而可以对放电区域进行空间分辨发射光谱测量.作者利用这套装置对氩气的ECR微波等离子体和直流辉光放电等离子体进行诊断.在ECR微波等离子体的下游区内氩离子谱线的发射强度很弱,主要是高激发态原子的辐射.在磁共振增强放电区,离子谱线强度有所增加但仍比原子谱线弱,类似于直流辉光放电正柱区的光发射特性.     

Determination of (40)ca(+) in the presence of (40)ar(+): an illustration of the utility of time-gated detection in pulsed glow discharge mass spectrometry

The glow discharge ionization source operated in the pulsed, or modulated, power mode affords a number of distinct advantages over its steady-state counterpart. It is well-known that pulsed plasma operation permits the application of higher instantaneous powers by allowing time for the sample to cool. This minimizes sample overheating while effecting higher sputtering yields and lower limits of detection. The presence of discrete time regimes affords the added advantage of temporal selectivity. Such selectivity allows the observation of analyte ions during a time regime in which their signal is at a maximum while that of electron ionized background species is declining. Significantly, time regimes are found when no background argon ion signals are observable but analyte ion signals remain. This means that discrimination against isobaric interferences arising from the discharge gas is possible. A prime example of the utility of this advantage arises in the determination of calcium with an argon glow discharge. Both the major argon and calcium isotopes are found at a nominal m/z of 40. Time-gated mass spectrometeric detection during the afterpeak time regime enables the ready determination of (40)Ca(+) in samples at the ppm level. A linear calibration curve is obtained that also demonstrates the elimination of the (40)Ar(+) signal from mass spectra obtained with either a dc or rf glow discharge ion source.     

Two-dimensional model of a direct current glow discharge: description of the argon metastable atoms, sputtered atoms, and ions

A two-dimensional model is presented that describes the behavior of argon metastable atoms, copper atoms, and copper ions in an argon direct current glow discharge, in the standard cell of the VG9000 glow discharge mass spectrometer for analyzing flat samples. The model is combined with a previously developed model for the electrons, argon ions, and atoms in the same cell to obtain an overall picture of the glow discharge. The results of the present model comprise the number densities of the described plasma species, the relative contributions of different production and loss processes for the argon metastable atoms, the thermalization profile of the sputtered copper atoms, the relative importance of the different ionization mechanisms for the copper atoms, the ionization degree of copper, the copper ion-to-argon ion density ratio, and the relative roles of copper ions, argon ions, and atoms in the sputtering process. All these quantities are calculated for a range of voltages and pressures. Moreover, since the sticking coefficient of copper atoms on solid surfaces is not well-known in the literature, the influence of this parameter on the results is briefly discussed.     

电极结构对辉光放电着火电压的影响

用于微波传感的辉光管存在着火电压高的问题.本文研究了针形电极在几种电极结构下的辉光放电着火电压,电极结构分别为2针、3针和4针.在本实验的氩气压0.5～2.5 kPa范围内,几种电极结构下着火电压有明显的不同,在0.5kPa气压下着火电压差值最大(208 V).进行了电场计算,根据计算结果简要分析了着火电压变化行为.本...     

Diamond-like carbon films of low hydrogen contents made with a mixture of hydrocarbon and reactive gas

Diamond-like carbon coatings were deposited from a d.c. glow discharge in a gas mixture which consisted of argon, CO₂ and C₂H₂. The grown films are hard, transparent in the IR region and electrically insulating. The hydrogen content is typically lower by at least a factor of 3 than that of films grown from r.f. glow discharge of hydrocarbons.     

建立快速测定空分设备液氧中氧化亚氮的分析方法

介绍一种利用毛细管热导检测器气相色谱法(GC-TCD)测定空分设备液氧中氧化亚氮的检测方法。比较了填充柱和毛细管柱、脉冲放电检测器和热导检测器的优缺点,从生产实际出发,确定选择10m的毛细管PQ柱和热导检测器的搭配,对空分设备旁冷凝器的液氧中氧化亚氮含量进行监控。实际运用情况表明:该方法具有分析准确、过程时间短和稳定性好的优点。     

毛细管放电软X光激光装置固有预脉冲的消除

本文对毛细管放电产生类氖氩46.9nm激光进行了实验研究。实验中发现毛细管放电装置中布鲁姆林(Blumlein)传输线所产生的固有预脉冲对软X光激光的产生及稳定输出都有十分不利的影响。为了消除这种影响,提出了用外加隔离开关和隔离电容的方法消除固有预脉冲。经过实验验证,确定了隔离开关和隔离电容的最佳位置。结果该方法能够有效隔离固有预脉冲,使整个放电装置达到稳定运行。在此基础上,得到并改善了毛细管放电类氖氩46.9nm激光输出。     

Hysteresis of the current-voltage characteristic of a continuous electron-beam-controlled discharge in a nitrogen flow

A hysteresis in the current-voltage characteristic of continuous electric discharge controlled by an electron beam in a nitrogen flow has been experimentally observed. It is suggested that the transition from a self-sustained glow discharge regime (typical of ionization chamber) to the electron-beam-controlled discharge is accompanied by the transition from the laminar to turbulent boundary layer at the cathode surface.     

The flowing afterglow in argon and helium: Differences in two reactor designs in application to the analysis of moisture

Excitation by rare gas metastables in a glow discharge afterglow is effective for the sensitive chemiluminescent detection of trace moisture. In the development of a flowing afterglow (FLAG) system for the study of effluent gases from high explosives, two approaches were taken in the design of a modular reactor. A glass reactor system with a tantalum shell hollow cathode source isolated by a Woods horn was compared to a 3 in. dia. steel reactor in which the reactor entrance port acts as the cathode. The sensitivity of both systems increases linearly with currents up to 15 mA in operation at 1 Torr argon or helium. The steel reactor provides an order of magnitude greater sensitivity for OH than the glass reactor. A continuous moisture background at 60°C over vacuum dried nitrocellulose of 0.9 nmol/gm-s (0.02 ppm) is demonstrated. With the steel system a photon count sensitivity for OH at 308.9 nm of 30000 counts/nmol in argon and 5200 counts/nmol in helium is obtained using a 0.4 nm bandpass.     

等离子体的Langmuir探针诊断及数值滤波

Ｌａｎｇｍｕｉｒ探针是诊断等离子体荷粒子参数的重要手段。本文首次报道了用加热的调谐探针,在抑制了对探针的射频干扰和“中毒效应”之后,对探针Ｉ－Ｖ曲线的统计涨落噪声进行了数字滤波的光滑化处理,获得了射频辉光放电硅烷等离子体的电子能量分布函数,平均能量和浓度等重要参数。     

Numerical Simulation of Two-Dimensional Structure of Glow Discharge in View of the Heating of Neutral Gas

A two-dimensional computer model of glow discharge is given, which takes into account the heating of ambient gas and the external electric circuit. The structure of a glow discharge in molecular nitrogen is investigated numerically in the pressure range from 1 to 20 torr at an electric field intensity of up to 4 kV/cm. The regularities of heating a gas are investigated at different pressures and electric field intensities. It is demonstrated that, at a pressure p = 1 torr, a glow discharge burning in the mode of normal density of current assumes a toroidal shape.     

高纯氖中杂质含量的测定

介绍了一种利用热导检测器(TCD)、氧化锆检测器(ZrO2D)、脉冲放电氦离子化检测器(PDHID)分析高纯氖中微量氦、氢、氧+氩、氮、一氧化碳、二氧化碳、甲烷的方法.经过方法验证证明,该方法能够达到较高的准确度和精密度.     

A glow discharge ion gun for etching

A simple glow discharge ion source is described which has been designed to etch specimens by selective sputtering. Output ion currents of up to 0.7 mA for argon and 2 mA for hydrogen have been achieved at 8 kV. A theory of operation is proposed to explain the measured energy spectrum of the emergent ions.     

Plasma modification and deposition on inner tube faces by pulsed DC discharges

The modification of inner surfaces of tubes becomes increasingly important in many fluid transport applications. However, long tubes require special plasma techniques for a surface functionalization on the nanometer scale without damaging the bulk. This work focuses on pulsed DC glow discharges in inert argon, reactive oxygen, nitrogen and air plasma as well as polymerizing acetylene plasma revealing strong influences to the wetting behavior by the total duration of the plasma discharge time (plasma on-time). While the investigated polymers polyamide, polycarbonate, polyethylene terephtalate, and thermoplastic polyurethane react very differently on the inert and reactive etching (activation) plasma, the deposition of plasma polymer films (polymer-like carbon with decreasing cross-linking at lower plasma intensity and >50% hydrogen content) suppresses all substrate influences.     

Plasma modification and deposition on inner tube faces by pulsed DC discharges

The modification of inner surfaces of tubes becomes increasingly important in many fluid transport applications. However, long tubes require special plasma techniques for a surface functionalization on the nanometer scale without damaging the bulk. This work focuses on pulsed DC glow discharges in inert argon, reactive oxygen, nitrogen and air plasma as well as polymerizing acetylene plasma revealing strong influences to the wetting behavior by the total duration of the plasma discharge time (plasma on-time). While the investigated polymers polyamide, polycarbonate, polyethylene terephtalate, and thermoplastic polyurethane react very differently on the inert and reactive etching (activation) plasma, the deposition of plasma polymer films (polymer-like carbon with decreasing cross-linking at lower plasma intensity and >50% hydrogen content) suppresses all substrate influences.     

Surface modification of carbon electrodes using an argon plasma

In this work, an activated carbon sheet was modified, to improve capacitance and energy density of electric double layer capacitors (EDLCs). Surfaces were treated with plasma for selected times of 1, 5, 10, 20, and 30 min. The plasma source was a DC glow discharge in argon gas. The pressure was 20 Pa and the distance between positive and negative electrodes was 20 mm. DC power was 70 W. The activated carbon sheets were set up so that the sheets were covered with the DC glow discharge. The results showed that plasma treatment led to roughening of the surface of the activated carbon sheets which became more pronounced for increased time. This was attributed to an increased surface area caused by argon plasma etching. For discharge times greater than 10 min, contamination from sputtered PTEE in the chamber appeared to have a smoothing effect and led to a reduction of the measured surface area. Capacitance of the EDLCs cells with the activated carbon sheets after 1 min plasma surface treatment was increased by 2% compared to EDLCs cells with the original activated carbon sheet. The results have shown that the modification by plasma treatment of activated carbon sheets is a suitable technique for EDLCs used in high current applications.