Our results indicate some new relevance for the application of melanopic lux as an additional metric to predict non-visual light effects of electrical light sources for nursing homes, work places, and homes.
An alternating current (ac) high-pressure mercury arc has been experimentally investigated, and the results have been compared with model calculations. In the model, only radial dependencies are considered, and a careful treatment of the radiation transport is included. The absolutely measured side-on radiance in the visible and near ultraviolet spectral range can now be quantitatively reproduced by this model starting from the measured arc current. Agreement between the measured and calculated radial temperature profile can be obtained only by taking into account the time-dependent behavior of the investigated ac arc. The calculated field strengths agree with the measured ones only if more recent values of momentum transfer cross sections for the calculation of the electrical conductivity of mercury have been used. The time-dependent pressure in the discharge is determined via the electrical conductivity using Ohm’s law, the radial temperature distribution, and the electrical field strength.
Electrode-sheath voltages (ESVs) were determined as a function of time in high-pressure ac mercury arcs running at different frequencies in the range 50 Hz–5 kHz with sinusoidal wave forms. Besides the experimental investigations, a one-dimensional model was used to describe the arc-column properties. Measurements of the voltage across the arcs were compared with model calculations for the arc-column voltage only. The calculated voltages are mostly smaller than the measured ones, and it was concluded that the difference should correspond to the ESV. This voltage drop was compared with values obtained in a completely different way, namely, by measuring the voltage at different lengths of the arcs which were otherwise identic, and extrapolating it to zero length. As had been shown before, at 50 Hz this voltage drop has a very pronounced time behavior during a half cycle. The investigations were extended to higher frequencies, and the obtained differences are discussed. The field strengths were derived from the rise of the measured voltage versus the discharge lengths; a quantitative agreement with the calculated field strengths was obtained by choosing an appropriate pressure.
In this paper we introduce an experimental technique that allows for high-speed, three-dimensional determination of electron density and temperature in axially symmetric free-burning arcs. Optical filters with narrow spectral bands of 487.5–488.5 nm and 689–699 nm are utilized to gain two-dimensional spectral information of a free-burning argon tungsten inert gas arc. A setup of mirrors allows one to image identical arc sections of the two spectral bands onto a single camera chip. Two-different Abel inversion algorithms have been developed to reconstruct the original radial distribution of emission coefficients detected with each spectral window and to confirm the results. With the assumption of local thermodynamic equilibrium we calculate emission coefficients as a function of temperature by application of the Saha equation, the ideal gas law, the quasineutral gas condition and the NIST compilation of spectral lines. Ratios of calculated emission coefficients are compared with measured ones yielding local plasma temperatures. In the case of axial symmetry the three-dimensional plasma temperature distributions have been determined at dc currents of 100, 125, 150 and 200 A yielding temperatures up to 20000 K in the hot cathode region. These measurements have been validated by four different techniques utilizing a high-resolution spectrometer at different positions in the plasma. Plasma temperatures show good agreement throughout the different methods. Additionally spatially resolved transient plasma temperatures have been measured of a dc pulsed process employing a high-speed frame rate of 33000 frames per second showing the modulation of the arc isothermals with time and providing information about the sensitivity of the experimental approach.
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