Thomson scattering in a low-pressure argon mercury positive column

Abstract

The electron density and the electron temperature in a low-pressure argon mercury positive column are determined using Thomson scattering. Special attention has been given to the stray light reduction in the Thomson scattering setup. The results are obtained in a discharge tube with a 26 mm diam, 5 mbar of argon, a mercury pressure in between 0.14 and 1.7 Pa, and an electric current ranging from 200 to 400 mA. The systematic error in the electron density is 15%, the statistical error is 25%. The total error in the electron temperature is 10%–20%.

Radiometric efficiency of low pressure barium discharges

“…Bakker and Kroesen have recently demonstrated that color temperature in fluorescent lamps can be modified by controlling radial cataphoresis. 24,25 Numerical modeling of low-pressure gas discharges is a well-developed field that relies heavily on basic atomic data. For Ba, there is a need for a large volume of data including radiative decay rates, electron-impact excitation, and ionization cross sections of Ba, Ba*-Ba quenching cross sections, Ba*-rare gas quenching cross sections, line broadening coefficients, and diffusion coefficients.…”

Thomson scattering in a low-pressure neon mercury positive column

“…8 and the density of the 2p states as given in Ref. 7, we can conclude that the LIF signal is of the same order of magnitude as the Thomson scattering signal for the measurements in series A and B. For series C, the LIF signal is much lower, and for series D and E, the LIF signal is negligible.…”

“…The error in the absolute value of the electron density due to uncertainty in the calibration is approximately 15%. 9 For the measurements at the two lowest mercury pressures, there is an additional systematic error introduced by the correction for the LIF signal. For the 18°C measurements, this additional error is at maximum 30%, for the 24°C, this additional error is at maximum 10%.…”

“…6 Furthermore, we measured the mercury ground state density profile 5 and the emission and excited state density profiles. 7 With our Thomson scattering setup 8 we investigated the influence of radial cataphoresis on the electron velocity distribution function in an argon-mercury discharge. 9 Since these Thomson measurements are much easier to perform in such a discharge than in a neon-mercury discharge, this was our starting point.…”

“…7 With our Thomson scattering setup 8 we investigated the influence of radial cataphoresis on the electron velocity distribution function in an argon-mercury discharge. 9 Since these Thomson measurements are much easier to perform in such a discharge than in a neon-mercury discharge, this was our starting point. However, the explanation of the results of the measurements in mercury-neon discharges described above needs a better knowledge of the electron density and the electron temperature in such a discharge.…”