Continuum radiation in a high pressure argon–mercury lamp

Abstract

In typical high pressure high intensity discharge lamps about 60% of the deposited power is released in non-useful channels, non-radiative heat transfer from the hot arc core, ultraviolet radiation and infrared radiation, of which the last is the dominant one.To reduce the amount of infrared radiation emitted in high pressure argon-mercury lamps the sources of continuum radiation are identified, quantified and compared with results from emission spectroscopy. Objective data, especially for mercury, are lacking, which makes experimental verification necessary.Three possible continuum radiation sources were examined: electron-atom free-free bremsstrahlung, electron-ion free-free bremsstrahlung and electron-atom free-bound recombination radiation. The radiance caused by each of these processes can be calculated from test lamp fillings and the temperature profile in the lamp using a computer program. From comparing experimental results with computer calculations, the electron-mercury atom bremsstrahlung process has been determined as dominating the infrared radiation.

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

“…As pointed out in Refs. [38][39][40], continuum radiation-based electron characterization represents one of the easiest methods of determining both n e and T e simultaneously. The continuum radiation from the ionized gas originates from the free electrons that undergo interactions with ions and neutral atoms; thus, valuable information on the statistical state of free electrons can be retrieved from the measured emission spectrum.…”

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

“…The free-free radiation emitted in collisions of electrons with neutral species r is described by [36,37] ff (20) with…”

“…In the calculation of the electron Stark widths the sum over the lines connected to upper or lower level of the considered line, e.g. (36), was restricted to lines with transition wavelength λ ul below 10000 nm. The total number of these lines is close to the number of lines used by Menart et (table 2).…”

“…Thus the temperatures, where Stark broadening becomes the dominant broadening mechanism, depends on the considered line. While the emission coefficient is independent of the line widths the net emission coefficient for non-zero radius R depends on the absolute line widths and thus on the electron Stark width scaling factors s r introduced in (36), (38), and (39).…”

“…They are summarized in table 2. In expressions (36), (38), and (39) all transitions connected to upper or lower level of the considered line have a positive contribution to the electron Stark width. Thus, values of s r above unity as those for Ar + , Fe, and Fe + may be caused by a lack of lines in the underlying data.…”