Determination of electron density and energy influx in a hollow cathode glow discharge used for powder modification

The electron density and energy influx in an argon hollow cathode glow discharge were determined to obtain adequate parameters for subsequent surface modification of low density polyethylene (LDPE) powder to change the wettability. The electron density was studied by Langmuir probe measurement in dependence on process gas pressure and hollow cathode material. Besides the determination of the rate of increasing electron density with input power an optimal experimental pressure was determined. The energy influx was studied by thermal probe measurements in dependence on process gas pressure, bias voltage, axial position and hollow cathode material. Inside the hollow cathode the energy influx is nearly constant along the whole cathode length. With increasing pressure the energy influx decreased. At biased thermal probe the energy influx was observed to decrease up to the floating potential and beyond it increases with increasing voltage. Using different hollow cathode materials the electron density as well as the energy influx reach higher values for aluminum than for copper and stainless steel.     

Relative densities of hydrogen ion species in a hollow cathode glow discharge

Highly resolved Doppler shifted peaks of the hydrogen Balmer lines, resulting from charge exchange of H⁺, H₂⁺, and H₃⁺ with an H₂ gas target, were obtained without the need for a deconvolution procedure. This enabled the unambiguous determination of the chemistry of these hydrogen species in the units of mTorr pressure range. This was obtained from a gaseous discharge using a biconical hollow cathode that yielded a well collimated and monoenergetic beam.     

Influence of the hollow cathode dimensions on the electron beamcurrent in a pseudospark discharge

Investigations on the electron beam current of a free running pseudospark discharge are presented. A single gap system with hollow cathodes of different dimensions is used. The filling gases are argon and helium. The electron beam signal consists of a first pulse with currents of several hundreds of mA and a main pulse with currents up to 20 A. A variation of length and diameter of the hollow cathode significantly influences the pressure range in which a free running pseudospark discharge exists and the peak current of both electron beam pulses. Plasma formation and electron beam generation are studied by high speed photography. The experimental results give some information on the discharge mechanisms that is integrated in a qualitative model of the pseudospark discharge     

槽型空心阴极放电中槽底阴极面的电子发射对放电的影响

运用粒子和流体组合模型理论研究了槽型空心阴极放电中槽底阴极面上二次电子发射对放电等离子体特性、电离特性及阴极溅射的影响.研究表明,从槽底阴极面发射的电子在进入负辉区后,可以形成振荡电子,因而具有增强电离的作用.根据各阴极面上的离子的空间分布可以推知槽底附近的阴极面上的溅射较强,这可以解释槽型空心阴极放电实验中观察到的因溅射导致槽底截面形状圆形化的现象.     

Laser action in a gallium hollow cathode discharge

cw laser action was observed for the 6335 and 7199 Å transitions of Ga II in a hollow cathode discharge. Charge exchange and radiative cascade processes are suggested to be responsible for the population of the upper laser levels.     

Time evolution of hollow cathode ionization processes in the finalbreakdown phase of a transient hollow cathode discharge

The enhanced ionization processes taking place inside the hollow cathode region (HCR) of a transient hollow cathode discharge (THCD) are essential events which lead to final electrical breakdown. This ionization growth is permanently assisted by a virtual anode moving in the anode-cathode gap (A-K gap), which extends the anode potential to within the hollow cathode region. In the paper, the ionization growth inside the HCR under the enhanced field due to the close proximity of the anode potential has been studied using a statistical technique in a range of pressures, with three different cathode apertures. Statistical time distributions of an extensive experimental data set are analyzed to understand the mechanisms involved in the final stages, just before electric breakdown     

Study of the rectangular hollow cathode discharge

The rectangular hollow cathode discharge is studied with respect to the applicability of similarity mechanisms analogously to other gas discharge types. Probe characteristics of the discharge are measured, the conditions of steady and continuous discharge glow in the cathode cavity are determined.     

CW laser oscillation in a hollow cathode He-Kr discharge

CW laser oscillation on the 4694 Å transition of Kr II has been observed in a hollow cathode He-Kr discharge.     

Intermodulated optogalvanic Zeeman spectroscopy in a hollow cathode discharge

The Zeeman and hyperfine structures of various transitions of calcium, copper, and neon are investigated by means of Doppler-free optogalvanic spectroscopy. This work demonstrates the suitability of the hollow cathode discharge to high resolution Zeeman spectroscopy of refractory and reactive elements.     

Atomic nitrogen laser action in a hollow cathode discharge

Near-infrared laser action of nitrogen atoms was obtained in a hollow cathode discharge. Four laser lines at wavelengths of 1358.2, 939.3, 938.7, and 862.9 nm were observed in the cw mode. In addition, the laser line at 904.6 nm was observed in quasi-cw operation in the afterglow for the first time. It is supposed that resonant charge exchange between He⁺ and N₂ followed by predissociation of N ₂ ⁺ is an important way of populating the upper laser levels.     

Production of copper vapor in a pulsed hollow cathode discharge

Spectral emission from a pulsed Cu hollow cathode was investigated in relation to discharge current to gain information on the density of the sputtered Cu vapor and on the persistence time of the metastable and ground-state atoms. The cathode was excited with 250 μsec discharge pulses at current densities up to 1 A/cm², using He, Ne and Ar as buffer gases. The intensities of the emitted Cu I lines were found to depend strongly on the simmer current. In atmospheres of Ne or Ar, the intensities of the resonance lines exhibited characteristic maxima during the initial 20 μsec of the discharge pulses. The density of the sputtered Cu atoms was determined by absorption measurements using a second Cu hollow cathode as alight source.     

Non-local model of hollow cathode and glow discharge

A general form of the non-local equation for an ionization source in glow discharge and hollow cathode 3D-simulation is formulated. It is a fundamental equation in hollow cathode theory, which allows formulation of a complete set of field equations for a self-consistent problem in a stationary glow discharge and hollow cathode. It enables us to describe the region of negative glow and the hollow cathode effect and compare calculation results of electrical dependencies (pressure-voltage) with experimental data, – under conditions of gradual appearance of the hollow cathode effect.     

空心阴极放电条纹特性的光谱诊断

利用发射光谱法,研究了圆柱型空心阴极放电条纹的特性.测量了条纹区的发射光谱,在此基础E计算得到r电子激发温度、相对电子密度和电子平均能量的空间分布特性.结果表明条纹区的光强、电子激发温度和电子密度均呈非等幅的周期性变化.与暗纹中心处相比,明纹中心具有较高的电子激发温度和较低的电子密度.由阴极向阳极,明纹中心处的电子激发温度幅值逐渐减小.此外,条纹区的电子激发温度随着电流的增加而增加.     

Sheath and electron density dynamics in the normal and self-pulsing regime of a micro hollow cathode discharge in argon gas

A microplasma is generated in the microhole (400 μm diameter) of a molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure (30–200 Torr) in pure argon. Imaging and emission spectroscopy have been used to study the sheath and electron density dynamics during the stationary normal regime and the self-pulsing regime. Firstly, the evolution of the microdischarge structure is studied by recording the emission intensity of the Ar (5p[3/2]₁–4s[3/2]₁)_{1}) line at 427.217 nm, and Ar⁺ (4p′ ²P_3/2–4s′ ²D_5/2)_{5/2}) line at 427.752 nm. The maximum of the Ar⁺ line is located in the vicinity of the sheath-plasma edge. In both regimes, the experimental observations are consistent with the position of the sheath edge calculated with an ionizing sheath model. Secondly, the electron density is recorded by monitoring the Stark broadening of the H_b_\beta-line. In the self-pulsing regime at 150 Torr, the electron density reaches its maximum value of 4 × 10¹⁵ cm^-3, a few tens of ns later than the discharge current maximum. The electron density then decays with a characteristic decay time of about 2 μs, while the discharge current vanishes twice faster. The electron density in the steady-state regime is two orders of magnitude lower, at about 6–8 × 10¹³ cm^-3.     

Laser action in an indium hollow cathode discharge

Hollow cathode discharge excitation of indium is shown to produce laser action at 468.1, 689.2, 1342.8, and 1720nm. The cw468.1 nm and 1720 nm ionic lines are excited by charge exchange effect whereas the 689.2 nm cw ionic line is excited by a radiative cascade. The 1342.8 nm atomic line appears in the afterglow of the pulsed discharge and its population inversion is produced by recombination of the indium ions and the electrons. Shanghai Institute of Optics and Fine-Mechanics, Academia Sinica. Research Fellow 1979–1980 of the Alexander-von-Humboldt-Stiftung