Infrared continuum radiation from high and ultra-high pressure mercury lamps

Abstract

Infrared (IR) continuum radiation from the arc of high and ultra-high pressure (UHP) mercury lamps was measured and modelled. Three major contributions to the IR continuum are electron–atom bremsstrahlung, which is dominant, electron–ion bremsstrahlung and electron–ion recombination radiation. The line width of the resonance broadened Hg 71S0 to 61P1 transition at 1014 nm was used to determine the arc core Hg density, and the radiance of this line was used to determine the arc temperature as a function of radius. The temperature map for the UHP lamp was checked using the Bartels method on the 546 nm line of Hg. Model results based on recently published electron–atom bremsstrahlung coefficients were found to be in good agreement with measurements across the near IR.

Measuring the pressure in ultrahigh-pressure mercury arcs

“…19 The axis temperature T = 8270 K came from a radiance measurement; the range of 8200-8300 K for this lamp was confirmed on several Hg lines and with two experimental setups. 10 Recently, Kane et al 6 confirmed this p value by a Brewster-angle reflection measurement of n at the inner wall and an estimate of the local T based on pyrometry of the outer wall. They found 20.1͑1.1͒ MPa for a lamp of the same type; the difference of 6% can be due to production tolerances but also to a quartz-tube shielding in the first experiment that may well have increased the pressure slightly by raising the temperature of the arc tube.…”

“…Lawler et al 10 determined a pressure of 21.3 MPa for a commercial Philips UHP lamp ͑120 W, 1.0 mm arc gap͒ at vertical operation from measurements of the Hg number density n and the local temperature T on the arc axis. The density n = 1.87ϫ 10 26 m −3 was derived from the measured width of the 1014 nm Hg line whose resonance broadening is well understood.…”

“…Such comparison is of fundamental interest especially at higher p ͑25-30 MPa͒ because a deviation would indicate a possible breakdown of the single-perturber approximation that is assumed in the 1014 nm method. 10 We tried this comparison at around 25-27 MPa with appropriate lamps and saw evidence that the 1014 nm method might underestimate the pressure by 10%-20% there. However, these results are uncertain because of difficulties with the proper measurement of the 1014 nm line profile and with the necessary optical-depth correction.…”

“…More precise methods consist of simultaneous measurements of the local particle density n and temperature T at some position in the plasma, e.g., by plasma spectroscopy and of solving the equation of state for the local pressure. [6][7][8][9][10] This delivers the pressure throughout the lamp because hydrostatic or hydrodynamic pressure variations are normally negligible. Rather than via n and T, the pressure can, in principle, also be measured directly by a manometer, connected to the hot lamp such that the pressure gauge remains cold.…”

A calibrated integrating sphere setup to determine the infrared spectral radiant flux of high-intensity discharge lamps

“…Infrared radiation, either in the form of radiation from the plasma or in the form of thermal radiation from the burner wall, can consume 50-75% of the total input power. The ALITE-II project's [6] primary focus was the infrared radiation of HID lamps; several papers regarding the infrared radiation from HID lamps have recently been published [7][8][9]. In these papers the focus was mainly on the continuum radiation generated by the plasma.…”