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3
Electrical
Discharge
Lamps
3.1 Plasma Processes
This chapter is dedicated to the technology of electrical discharges or plasma for
lighting applications. Plasma, which is often called the fourth state of matter, isan
ionized gas with extremely interesting and useful properties. The term plasma was
rst used to describe an ionized gas by Irving Langmuir in 1927 after observ-
ing how the electried uid carrying high velocity electrons, ions, and impurities
reminded him of the way blood plasma carries red and white corpuscles and germs.
The plasma state here on Earth is quite unusual and exotic but it becomes
very common in the outer layer ...