ARGES
Determination of instabilities in metal halide lamps in weightlessness.
What is the aim of the experiment?
High-Intensity Discharge (HID) lamps are gaining ground in the lighting industry because of their very high-energy efficiency. Inside these lamps, which are enclosed in a ceramic container, the gaseous contents begin to de-mix or separate away from each other over time. When this separation occurs the resulting distribution of light is non-uniform in the illuminated area.
Furthermore, instabilities might occur in the lamp. This instability is characterized by the fact that the central channel of the plasma (ionised or electrically charged gas) starts to bend away from the central axis and may even start to rotate around this axis, in the shape of a corkscrew.
Although the instability may not have a direct detrimental effect on the efficiency of the lamp, lamps which are instable for a prolonged period, may develop a crack in the wall of the burner allowing the gaseous contents to leak into the outer bulb, and thus making the lamp no longer functional.
The main objectives of this experiment are to determine which factors are critical in the onset of spiral formation instabilities in HID lamps and to characterise the separation of individual gaseous elements in HID lamps using high-resolution emission spectroscopy. Spectroscopy analyses the light emissions coming from the different elements within the lamp.
Why do it in space?
In HID lamps, physical phenomena are severely influenced under Earths normal gravity conditions: Due to convection on Earth, this will cause a horizontally burning light discharge in a lamp to bend upwards and a vertically burning discharge will exhibit convective (heat transfer) properties in its cells.
This makes it impossible to study these phenomena on the ground. If a proper understanding of these phenomena is to be gained, experiments in a weightless environment are necessary.
What is it good for?
This experiment will help in the development of more efficient HID lamps in the future, for use in space and on Earth. This could have a large impact within the lighting industry as HID lamps are widely used for all kinds of applications, including highways, sports stadiums, building exteriors, shops, etc.
Team Members:
G.M.W. Kroesen
Eindhoven University of Technology
PO Box 513
NL 5600 MB Eindhoven
The Netherlands
Tel.: +31 40 247 4357
Fax: +31 40 245 6050
email: g.m.w.kroesen@tue.nl
Marco Haverlag
CDL
Phillips Lighting
Eindhoven
The Netherlands
More Information:
A Fact Sheet of the ARGES experiment is available for download as pdf-file in English and in Dutch.
A summary description of the ARGES experiment in Dutch is available at the ESA Dutch Internet Portal.