Visible emission spectrum of pulse-periodic discharge in high-pressure cesium vapor

The spectrum of pulse-periodic discharge in high-pressure cesium vapor has been studied by experimental and theoretical methods. Experiments confirmed a significant shift of the 6P and 5D recombination continuum thresholds toward longer wavelengths, which was theoretically predicted previously for the emission from discharge in a dense cesium plasma. The overlapping continua form an almost continuous spectrum of emission in the visible spectral range. The results of calculations well agree with the experimental data. It is established that the discharge under consideration is an effective, mercury-free source of light with a color rendering index of R _a = 98 and a light yield of η = 81 lm/W.     

Dynamics of the development of high-current pulse-periodic discharge in cesium vapor

Some peculiarities in the development of high-current pulse-periodic discharge in cesium vapor have been studied. It is established that, at a cesium vapor pressure of P _Cs > ～100 Torr, a difference between the electron temperature and that of the heavy plasma component almost does not influence the development of discharge. At P _Cs ～ 250 Torr, the character of discharge exhibits significant changes, which require further detailed investigations.     

A two-temperature model of pulse-periodic radiative discharge in high-pressure cesium vapor

A two-temperature model of pulse-periodic radiative discharge in high-pressure cesium vapor has been developed. Under high pressure and temperature conditions, a local thermodynamic equilibrium (LTE) in the discharge plasma is established at the electron temperature. Conditions in a nonequilibrium near-wall region are analyzed, where the state of plasma deviates from the LTE. The parameters of plasma during a discharge pulse and the radiation spectrum are calculated.     

Mechanism of the electric field effect on the intensity of visible continuum emission from the positive column of gas discharge in a cesium vapor-xenon mixture

We have studied the nature of continuum emitted in the visible spectral range from a noncontracted positive column of discharge in a cesium vapor-xenon mixture at a pressure of 45 Torr and at a degree of ionization below 3 × 10^?6. The main contribution to the continuous emission under such conditions is due to electron-xenon atom bremsstrahlung. The intensity of emission has been experimentally and theoretically studied as a function of the electric field strength and electron density in the positive column. It is established that an increase in the visible emission intensity with the electric field strength is related to an increase in the number of hot electrons in plasma.     

UV emission from capacitive discharge in inert gas-iodine vapor mixture

We have studied the optical characteristics of capacitive discharge in binary mixtures of helium, neon, argon, and krypton with iodine vapor in a spectral range of 180–300 nm. It is established that the main power of UV radiation from the discharge plasma is concentrated in the emission lines at 183.0 and 206.2 nm. The intensity of emission due the spectral lines of iodine atom was optimized with respect to the inert gas type and partial pressure. The optimum results were obtained using He-I₂ mixture with partial pressures of helium within 0.8–2.0 kPa and iodine vapor below 50–60 Pa. Being excited with a trains of nanosecond current pulses at a repetition rate of 10–100 Hz, the capacitive discharge emitted pulses with duration not exceeding 400–500 ns.     

On the efficiency of emission from a plasma column in high-pressure pulse-periodic discharge in cesium

Spectral energy fluxes emerging from the surface of an axially symmetric column of inhomogeneous cesium high-pressure plasma have been calculated by direct integration of the radiation-transport equation. It is shown that, at a specified plasma temperature on the axis, irrespective of the radiation -formation mechanism and the radial distribution of the plasma parameters, the maximum energy fluxes arise when the radial optical thickness τ _R of the plasma column is close to unity. The asymptotic τ _R value, at which the discharge column radiation is the largest part of the Planck radiation, has been found.     

The emission characteristics of low-pressure water vapor discharge UV emitters

We have studied the characteristics of UV emission sources operating on low-pressure normal (H₂O) and heavy (D₂O) water vapor excited by periodic-pulsed and glow discharges. The emission in a 300–330 nm wavelength interval has been studied in detail for water vapor pressures ranging from 50 to 2500 Pa. A comparison of the characteristics of emission from discharge plasma at low (50–150 Pa) and elevated (2.0–2.5 kPa) water vapor pressures reveals significant differences in the character of emission spectra, which can be related to the different types of emitting species (hydroxy radicals versus small clusters of such radicals and water molecules). Discharge current and emission intensity pulses in the periodic-pulsed discharge regime have been measured.     

Reconstruction of the X-ray emission spectrum of a nanosecond creeping discharge

A method is proposed for determining the soft x-ray emission spectrum of a nanosecond creeping discharge. The method includes a determination of the photoelectron density from photocurrent measurements and a calculation of the spectral flux density. The results are compared with experimental data on the wavelength interval of maximum radiation intensity. Pis’ma Zh. Tekh. Fiz. 24, 39–44 (April 12, 1998)     

Thermal diffusion of cesium vapor in helium

An examination is made of thermal diffusion of cesium vapor in helium. Calculations of the diffusion coefficients and the thermal diffusion ratio are made from an evaluation of the thermal diffusion flux during condensation of cesium from a mixture containing helium.     

Depth profiling of thin films with pulsed glow discharge atomic emission spectrometry

The application of microsecond pulsed Grimm glow discharge atomic emission spectrometry for depth profiling of thin films is examined. The effects of pulsed conditions including pulse voltage, pulse frequency, pulse width, and Ar pressure on depth profiling performance were characterized for Zn and Cu coatings on steel. Using optimized conditions, linear calibration curves of coating thickness for Zn (6.1-26.9 μm) and Cu (50-500 nm) on steel were achieved. A precision of 2-5% relative standard deviation was determined. An ultrathin coating of Cu (10 nm) on steel was also measured by this technique.     

Condensation of cesium vapor from flowing argon

This article considers experimental data on the condensation of small amounts of cesium from flowing argon. We have analyzed the influence of mist formation on condensation and compared the experimental data with calculated results.Deceased.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 4, pp. 600–606, April, 1971.     

Radiation characteristics of a dense cesium plasma in the visible range

Calculations are made of the radiation spectrum from a cesium plasma column. It is shown that this plasma may serve as a light source with a high proportion of visible radiation and an almost continuous spectrum. The visible spectrum is formed mainly by bright recombination 6P and 5D continua whose thresholds are shifted in the long-wavelength direction. Pis’ma Zh. Tekh. Fiz. 23, 40–45 (December 26, 1997)     

A theory of pulse-periodic radiative high-pressure cesium discharge

The gasdynamics of pulse-periodic discharge in high-pressure cesium vapor has been self-consistently modeled for the first time. The discharge is an effective light source with a continuous spectrum and a luminous efficacy of η_V=74 lm/W. Under conditions where the optical thickness of plasma in most part of the spectrum is close to unity, the main mechanisms of energy transfer in the discharge volume are nonlocal radiative heat exchange and radiative heat conduction.     

Microwave spectrum asymmetry in an optically pumped cesium beamresonator

This paper deals with a theoretical and experimental study that describes the effect of a frequency detuning of the laser used to achieve optical pumping in a small optically pumped cesium beam resonator. The ground state Zeeman sublevels with opposite angular momentum are unequally populated, leading to an asymmetrical microwave spectrum. The relative population asymmetry as a function of the laser frequency has a dispersion-like shape. Its dependence on laser intensity, applied magnetic field, and laser linewidth is demonstrated for a laser at 852 nm and tuned to the ²S_1/2F=3→²P_3/2F'=3 transition of the Cs D₂ line. Finally, the effect of a slight laser detuning on the Rabi pulling frequency shift is discussed     

Semiempirical equation of state with few constants for cesium vapor

Statistical analysis is performed of consistency of the known experimental data on the density of cesium vapor. A semiempirical equation of state with few constants is employed, which is based on “pseudogroup” expansions of pressure and density in powers of activity. The second group integral is theoretically calculated using spectroscopic and quantum-mechanical data on atomic interaction. A modification of this equation of state is suggested, which enables one to approximate experimental data both at low and moderate densities and in the near-critical region. Equations of state are derived, which describe both the data of single experiments and the majority of these data taken together. The experimental data indicative of the significant effect of anomalous ionization of cesium vapor on its thermodynamic behavior are shown to be invalid.     

Characterization of the pulsed discharge electron capture detector

A new version of the pulsed discharge electron capture detector (PDECD) has been developed and characterized. Changes to the old version include a slightly altered detector geometry, replacement of the polymer insulation with sapphire and quartz, and the use of methane dopant gas instead of nitrogen or hydrogen. Various operating parameters have been investigated and optimized, including discharge current, dopant gas, bias voltage, and sample introduction position. The resulting detector is more inert and more sensitive (a limit of 36 fg for lindane) and capable of operation at temperatures as high as 400 °C. By running 23 halocarbon compounds on the improved PDECD and on a (63)Ni-ECD using the same GC system, we find that the PDECD is superior to (63)Ni-ECD in terms of sensitivity, linearity, and response time. We attribute the enhanced sensitivity to a lower positive ion concentration, which in turn lowers the electron-positive ion rate of recombination. Pesticides (including some real-world samples) have also been analyzed on the PDECD. The results demonstrate that the PDECD can replace the radioactive ECD typically used in these analyses.