Pulsed Discharge In Xenon Research Articles

Influence of flash ignition mechanism of high-current pulsed xenon discharge on the optical degradation of the quartz shell in the UV region of the spectrum

Influence of flash ignition mechanism of high-current pulsed xenon discharge on the optical degradation of the quartz shell in the UV region of the spectrum

Energy and Emission Characteristics of a Short-Arc Xenon Flash Lamp Under "Saturated" Optical Brightness Conditions

We present the results of a study of the electrical, energy, and spectral brightness characteristics of an experimental three-electrode high-pressure xenon flash lamp under conditions ensuring close to maximum possible spectral brightness for the xenon emission. We show that under saturated optical brightness conditions (brightness temperature in the visible region of the spectrum ~30,000 K), emission of a pulsed discharge in xenon is quite different from the emission from an ideal blackbody: the maximum brightness temperatures are 24,000 K in the short-wavelength UV region and 19,000 K in the near IR range. The relative fraction of UV radiation in the emission spectrum of the lamp is >50%, which lets us consider such lamps as promising broadband sources of radiation with high spectral brightness for many important practical applications.

Investigation of a pulsed xenon discharge at medium pressure

The pulsed discharge in xenon at pressures between 10 and 50 Torr and a peak current of 130 mA has been analysed by means of a time-dependent, spatially one-dimensional fluid model. Main features of the model of the radially inhomogeneous discharge plasma in a discharge tube with an inner diameter of 6.5 mm are given. The comparison of results of model calculations with experimental data shows good agreement for the axial electric field, and the qualitative behaviour of measured axis densities of low-lying excited states is reproduced well by the model. The analysis of the spatiotemporal variation of the pulsed discharge shows the formation of a constricted column plasma at increasing pressure. In particular, a pronouncedly nonlocal behaviour of the electron component is found, and the densities of the metastable and resonance atoms are predicted to have a radial profile with a maximum out of the axis during the discharge phase.

Spectral characteristics of a high-current pulsed discharge in xenon

The radiation characteristics of a pulsed discharge xenon lamp are experimentally and theoretically studied. The data on radiation spectra are obtained for various compositions and pressures of working medium, energies and time profiles of excitation pulse, discharge gap configurations, etc. Electron temperature and mean spectroscopic symbol of emitting ions are estimated. It is demonstrated that cw radiation (continuum) results from the photorecombination transitions.

Measurements of Electric-Field Strengths in Ionization Fronts during Breakdown

Using laser-induced fluorescence-dip Stark spectroscopy, we performed time-resolved, direct measurements of electric-field strengths during the breakdown phase of a low-pressure, pulsed discharge in xenon. With this experimental technique we could for the first time quantitatively measure the time evolution of the driving force of the plasma breakdown process: the electric field. Moving ionization fronts were measured with submicrosecond resolution. These ionization fronts were sustained by a spatially narrow, rapidly moving region of strong electric field.

Emission characteristics of a pulsed discharge in xenon

Emission characteristics of a high-current pulsed discharge in xenon are studied experimentally. The study is aimed at developing a source of spontaneous UV radiation (with λ ≤ 250 nm) for controlling highvoltage crystalline diamond switches.

IR-LAS Measurements of a Pulsed Xenon Discharge Plasma

As a first step to understand the processes taking place in a pulsed xenon discharge, the temporal behavior of the radial metastable atom distribution in a xenon lamp was measured by IR laser absorption spectroscopy. During the first 10μs after starting the discharge, high electron density and the depletion of the ground state atoms at the center of the discharge brought about an almost flat distribution of the metastable atoms within the half-radius area. Following that, the metastable atom density became higher at the center than outside because of recombination between electrons and ions. After the metastable density increase and following voltage cut off, the metastable density decreases again. Considering the diffusion equation alongside these results, it becomes clear that the decrease of the metastable density is caused by quenching to the resonace level from the metastable level or three-body collisions forming excimers.

On the decay of metastable and resonance Xe atoms in the afterglow of a constricted discharge

The radial and temporal dependences of the metastable 6 3P2 (Xem) and resonance 6 3P1 (Xer) state densities are measured in the active phase and afterglow of pulsed discharge in xenon by laser absorption technique at pressure 10 Torr and currents 200–500 mA. It is found that the densities grow by a factor of 25 during the transition from the active discharge phase to the afterglow and there is no decrease of the density after switching the field off. It is shown that the collisional-radiative recombination prevails over the dissociative recombination because of high electron density and relatively low electron temperature in a constricted discharge. The electron cooling after the field switching-off is caused mainly by electron–ion collisions whereas the electron–atom elastic collisions are less effective due to the Ramsauer effect. The quantitative modelling of the active phase and afterglow is performed on the basis of the time-dependent system of balance equations for densities of excited atoms and charged particles, as well as electron temperature. The results of the modelling reflect all peculiarities of the excited atom behaviour both in the active phase and afterglow.

Influence of reflected radiation on a pulsed xenon discharge in quartz tubes (review)

Influence of reflected radiation on a pulsed xenon discharge in quartz tubes (review)

Superheating instability in a pulsed xenon discharge

It is shown that previously obtained conditions for superheating instability substantially vary if we take into account secondary xenon ionization. Instability completely vanishes if the density of heavy particles in the discharge is kept constant and whenever a discontinuous time variation of temperature T in a restricted region between 15 · 103 ° K and 20 · 103 ° K is possible for a constant effective pressure. The development of instability is studied numerically by a ranging method. Stationary temperature distributions possessing a high contrast as a local temperature passes through a given range of instability with constant pressure are presented.

Interferometric measurements of the gas density distribution in the dark space of an abnormal glow discharge in xenon

Measurements of the spatial dependence of the gas density distribution near the cathode of an abnormal glow discharge on the current density are described. The technique uses a pulsed discharge in xenon with a mercury cathode, placed in one arm of a Michelson interferometer so that the changing density influences the optical path length. The sensitivity of the system is equivalent to approximately 0.04 Torr at 300K. Considerable changes in gas density are observed in the dark space, particularly at high current densities. The proposed theoretical model for this non-uniform gas density agrees well with the experimental results.

Decay of excited species in the afterglow of a pulsed discharge in xenon

The decay of the 1s5 metastable state of xenon has been measured by means of an absorption technique in the afterglow of a pulsed DC discharge. At the same time the decay of excited Xe2* molecules has been measured by monitoring the ultraviolet continuum radiation. It is shown that these excited molecules are formed in two-body and three-body collisions between metastable 1s5 atoms and ground state atoms. The rate coefficient for de-excitation of 1s5 state by two-body collisions is determined as 35*10-16 cm3 s-1 and and the rate coefficient for de-excitation by three-body collisions as 8.55*10-32 cm6 s-1. The diffusion coefficient of Xe(1s5) in Xe is DM=52*1016 cm-1 s-1.

Stimulated Infrared Emission from Trivalent Uranium

Stimulated infrared emission from uranium(III) in CaF/sub 2/ was studied using a single CaF/sub 2/ crystal with 0.05 mole% uranium and silver films on both ends. The crystal was cooled with liquid helium and excited by a pulsed xenon discharge, and the radiation was isolated at 2.5 mu and detected. Oscilloscope traces of the detector response showed the ratio between the stimulated emission and the background light to be>1000 and relaxation oscillations to be present, the number of spikes increasing with the power of the xenon discharge. (D.L.C.)