Experimental verification of a zero-dimensional model of the ionization kinetics of XeCl discharges

An improved 0-dimensional model for XeCl high-pressure glow discharges is presented. Calculated discharge voltages are compared with precise measurements at a small, very homogeneous discharge. Excellent agreement in a wide parameter field demonstrates that this model may serve as a reference for simpler models describing the ionization kinetics

Small volume coaxial discharge as precision testbed for 0D-models of XeCl lasers

In order to check the predictions of 0D-models experimentally, a small coaxial discharge configuration for the generation of homogeneous high pressure glow discharges (diameter 11 mm, length 20 mm) in rare gas halogen excimer laser gas mixtures under accurately controlled conditions has been developed. It uses X-ray preionization and a special pulse-forming network (PFN) delivering fast rising (8 ns) single square pulses (U 0=25 kV; I=300 A; prop=100 ns). Discharge current and voltage are measured precisely by a capacitive voltage divider and a shunt integrated into the discharge chamber. All circuit data needed for the model calculations have been evaluated. Interferometric and spectroscopic diagnostics of the bulk of the discharge and of the cathode sheath have been performed. First results for Ne/Xe/HCl mixtures are compared with model calculations

Vacuum arc cathode spot parameters from high‐resolution luminosity measurements

Cathode spots on arc‐cleaned copper and molybdenum electrodes in vacuum were studied by fast image converter framing and streak camera photography with high temporal and spatial resolution. The frame exposure time was 20 ns and the interframe period was 200 ns; the streak sweep time was between 200 ns and 1 μs. Spatial structures with a resolution of 5 μm could be determined by observing the spot movement with a small slit at the streak camera and a high sweep speed. Strong fluctuations of the light emission of the spot were found with characteristic times of 50–100 ns. When the spot moved out of the slit field of view a stepwise decrease occurred in the measured light, indicating an internal substructure of the spot with distances between fragments less than 10 μm and even smaller fragment diameters. The current per fragment was estimated to be 20–40 A. The frames confirm the short time constants of the spot. From frame to frame a spot motion was observed in most cases, yielding spot residence times <200 ns

A hierarchical risk model for traffic participants

As traffic participation is inherently a risky activity, traffic psychology has generated a great number of so-called risk models, i.e. models in which the risk concept plays a major role. Three of these models are attracting a great deal of attention these days: Näätänen and Summala's ‘Model of drivers’ decision making and behaviour', Wilde's ‘Theory of risk homeostasis’ and Fuller's ‘Threat-avoidance model of driver behaviour’. All three models emphasize motivational aspects with regard to risk and they claim to be generally applicable to a large array of traffic situations. In an attempt to use these models for quantitative predictions in a concrete example (an overtaking manoeuvre), we found that many model components had not been defined at all, or had been defined only partially, or in a contradictory fashion. We have therefore developed our own model which allows quantitative calculations in terms of behaviour alternatives, subjective probabilities of events, and utilities of the outcomes of behaviour alternatives. The concept of risk is more sharply defined as well. Further, the model explicitly takes into account that traffic tasks may be conceived as hierarchically ordered in strategic, tactical and operational task levels

An argon cascade-arc plasma pulsed with 2200 amperes

In the past several authors have reported on experiments with wall stabilized arcs, to study transport coefficients, deviations from local thermodynamic equilibrium (LTE) and optical properties of these thermal plasmas. Most of these experiments have been performed with continuous arcs in a pressure range of atmospheric to a few 100 atm. In order to get high electron densities, temperatures and to reach higher ionization stages, a current pulse of approximately=2200 A is superimposed on a stationary argon cascade-arc with filling pressures of 1-3 atm. In this way high power densities can be reached, without the need of extensive cooling and power requirements. The rise time of the current pulse approximately=60 mu s and duration time approximately=1.5 m