Volume 88, Issue 9, 01 November 2000
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
88(2000); http://dx.doi.org/10.1063/1.1314306View Description Hide Description
We present results from a vacuum-ultraviolet (VUV) “photoabsorption imaging” technique based on the measurement of the time and space resolved absorption of a quasimonochromatic VUVbeam from a laser plasma light source. The use of VUVradiation as a probe beam permits direct access to resonance lines of (singly and more highly charged) ions and also to the resonant and nonresonant continua of atoms and ions. In this experiment we have confined ourselves to measurements using the resonances of Ca, and as markers of the temporal and spatial distribution of ground state atoms and ions in an expanding laser plasma plume. We show how time resolved column density maps may be extracted from such images. In addition we have extracted plasma plume velocities from the data, which compare well with an analytical laser ablation model.
88(2000); http://dx.doi.org/10.1063/1.1319163View Description Hide Description
Plasma immersion ion implantation is an effective surface modification technique. Unlike conventional beam-line ion implantation, it features ion acceleration/implantation through a plasma sheath in a pulsed mode and non-line-of-sight operation. Consequently, the shape of the sample voltage pulse, especially the finite rise time due to capacitance effects of the hardware, has a large influence on the energy spectra of the incident ions. In this article, we present a simple and effective analytical model to predict and calculate the energy distribution of the incident ions. The validity of the model is corroborated experimentally. Our results indicate that the ion energy distribution is determined by the ratio of the total pulse duration to the sample voltage rise time but independent of the plasma composition, ion species, and implantation voltage, subsequently leading to the simple analytical expressions. The ion energy spectrum has basically two superimposed components, a high-energy one for the majority of the ions implanted during the plateau region of the voltage pulse as well as a low-energy one encompassing ions implanted during the finite rise time of the voltage pulses. The lowest-energy component is attributed to a small initial expanding sheath obeying the Child-Langmuir law. Our model can also deal with broadening of the energy spectra due to molecular ions such as or in which case each implanted atom only carries a fraction (in this case, half) of the total acceleration energy.
Spatiotemporal behaviors of excited Xe atoms in unit discharge cell of ac-type plasma display panel studied by laser spectroscopic microscopy88(2000); http://dx.doi.org/10.1063/1.1314312View Description Hide Description
Two-dimensional spatiotemporal behaviors of excited Xe atoms in the resonance state and the metastable state were measured in a unit discharge cell of an ac-type plasma display panel by a laser absorption technique combined with an optical microscope. The measured density of has two large peaks on both the temporal anode and cathode sides. The peak at the anode has a narrower spatial distribution while the peak at the cathode is distributed over the electrode area. In its temporal behavior, the anode peak rises slightly faster than the peak at the cathode and decays faster at the beginning of afterglow, but both peaks tend to have the same decay rate in the later period. The behavior of shows similar features, but the decay rate is much larger, corresponding to the effective lifetime of imprisoned resonance radiation. The maximum densities of and are and respectively. Emission from atoms was also observed, and this nearly followed the current wave form. With these results, we estimated the efficiency of vacuum ultraviolet emissions from excited atoms and excimers formed from atoms.